MedicineLakex

Development of national emission standards for pesticides manufacturing industry

Development of National Emission Standards For Pesticides Manufacturing
Industry
CONTENTS
1.1 Pesticide Use
1.2 Pesticide Production in India
2.1 Acephate
2.1.1 Associated air pollutants
2.2 Aluminium Phosphide
2.2.1 Associated air pollutants
2.3 Captafol
2.3.1 Associated air pollutants
2.4 Captan
2.4.1 Associated air pollutants
2.5 Cypermethrin
2.5.1 Associated air pollutants
2.6 Dimethoate
2.6.1 Associated air pollutants
2.7 2,4 – Dichlorophenoxy Acetic Acid (2,4-D)
2.7.1 Associated air pollutants
2.8 Dichlorvos (D.D.V.P.)
2.8.1 Associated air pollutants
2.9 Ethion
2.9.1 Associated air pollutants
2.10 Endosulphan
2.10.1 Associated air pollutants
2.11 Fenvalterate
2.11.1 Associated air pollutants
2.12 Malathion
2.12.1 Associated air pollutants
2.13 Methyl Bromide
2.13.1 Associated air pollutants
2.14 Monocrotophos
2.14.1 Associated air pollutants
2.15 Isoproturon
2.15.1 Associated air pollutants
2.16 Phosalone
2.16.1 Associated air pollutants
2.17 Phorate
2.17.1 Associated air pollutants
2.18 Phosphamidon
2.18.1 Associated air pollutants
2.19 Zinc Phosphide
2.19.1 Associated air pollutants
3.1 Emissions Profile in Pesticide Industry
3.2 Solvents
3.3 Prioritisation of Air Pollutants for Control
3.4 Toxicity and Health Impact of Priority Pollutants
4.1 Principle of Air Pollution Control Technology
4.1.1 Separation techniques
4.1.2 Thermal destruction
4.1.3 Conversion to harmless product
4.1.4 Combination approach
4.2 Control Technologies Adopted in Indian Industries
4.3 Efficiency Evaluation of Existing Pollution Control Technology
4.4 Description of Various Treatment Technique
4.4.1 Absorption
4.5 Condensation
4.6 Chemical Reaction
4.7 Incinerator Technology with Air Pollution Control Devices
4.8 Adsorption
5.1 Introduction
5.2 Best Practicable Approach (general availability to required technology
and techno-economic feasibility)
5.3 Emission Standards with respect to Location Specificity
5.4 Emission Standards
5.5 Guidelines for Fugitive Emission Control
5.6 LDAR for Pesticide Industry
The word pest comes from the Latin word "pestis" which includes an animal or plant that occurs in such abundance as to present a distinct threat, economically or medically to man or his interest. A pest may be insect, fungus, weed, rodent, bacteria, virus, nematodes, acarid / mite, parasite and even animal or bird. Worldwide, about 10,000 species of insects are important as pest, out of 750,000 identified species. Over 50,000 species of fungi are responsible for some 1,500 plant diseases; Over 1,800 species of weeds out of the known 30,000 cause serious economic loss. About 15,000 species of nematodes produce more than 1,500 serious deleterious effects on plants. Over 1,00,000 species of pests destroy food which could be food for 135 million people. The word pest has no biological meaning. Pests are organisms that diminish the value of resources in which we are interested.
In India, crops are affected by over 200 major pests, 100 plant diseases, hundreds of weeds and other pests like nematodes, harmful birds, rodents and the like. About 4,800 million rats cause havoc in India. Approximately, 30% of Indian crop yield potential is being lost due to insects, disease and weeds which in terms of quantity would mean 30 million tones of food grain. The value of total loss has been placed at Rs 50,000 million, represents about 18% of the gross national agriculture production. The pest wise losses are as follows: Loss of Food Grains (%)
Besides the agriculture, non – agriculture pests are carriers of malaria, filaria, encephalitis, typhus, plague and other dreadful diseases. About 30 household pests are worthy of attention, like files, fleas, bedbugs, lice, cockroaches, mites, termites and moths. Man's war against pests is perennial and almost eternal. No agriculture or forest crop can be grown in an insect and disease – free environment. Pests and disease are parts of natural processes that are going on since the beginning of the universe, and the biological process of evolution. Total extermination of pests is not possible and is no longer the aim of pesticide application. The control of pests is the objective and designated as plant protection. The efficient producer wants to keep loss due to pests to a minimum pest control is now the chemistry of human survival.
While pest control is one of the imperative prerequisite, it bears also higher degree of negative impacts on environment. Since the chemicals which control the pest commonly known as pesticides. Pesticides are basically toxics and persistence; it can enter in food chain and causes injury to human health. It also destroys the diversity and food web and causes ecological imbalance. Pest control therefore needs regulation on the interest of human health and environment. Pesticide Use
Pesticides are defined as the substance or mixture of substances used to prevent, destroy, repel, attract, sterilise, stupefy or mitigate any insects. Generally pesticides are used in three sectors viz. agriculture, public health and consumer use. The consumption of pesticide in India is about 600 gms. / hectare, where as that of developed countries is touching 3000 gms. / hectare.
There is a wide range of pesticides found used in non-agriculture situations such as industries, public health and for a number of purposes in the home. Domestic use of pesticides is mainly as fly killer, ant killer, moth killer, repellants, rodenticides and fungicides etc. By and large industrial use of pesticide is of vital importance in the industries such as wood and carpet, wood preservation, paint industry, paper and board industry, leather industry, building industry, miscellaneous industrial application e.g. soluble cutting oils, industrial water systems, drilling fluids etc. Pesticide Production in India
Pesticide is manufactured as technical grade products and consumable
pesticides are then formulated The installed capacity of technical grade pesticide
was 1,45,800 tonnes during March 2005, and the production in the financial year
2004-05 was 94,000 tonnes. The year wise actual production during year 2001 to
2005 was given at Table 1.
Table 1: Actual Production of Technical Grade Pesticides
Overall Annual Growth
(Tonnes/Year) Growth (%)
(2004-05) / (2001-02)
Source: Annual Report 2005-06 of Ministry of Chemicals & fertilizers, Department of
Chemicals & Petrochemicals, page no – 54-55
The annual growth of pesticide production between the years 2001 to 2005 was
14.9%. The productions of various categories of technical grade pesticides against
the installed capacity during the year 2004-05 in India are summarized in Table 2.
Table 2: Installed Vs Production Capacity of various pesticides
Production Distribution
of various
Installed Production Installation pesticides
Source: Annual Report 2005-06 of Ministry of Chemicals & fertilizers, Department of Chemicals
From above table, the percentage distribution of various categories of technical
grade pesticides are insecticides (67%), Fungicides (24%), Weedicides (6%) and the
others Herbicides, Rodenticides, Fumigants (3%). The table clearly indicates that in
India the production of insecticides is very high compared to the other types of
pesticides. The list of technical grade pesticides manufactured under various types
in India during the year 2004-05 is given at Table 3. The technical-grade pesticides
manufactured are registered under the Insecticides Act, 1968 in India.
Information compiled from the Monitoring and Evaluation Division, Department of
Chemicals & Petrochemicals, Ministry of Chemicals and Fertilizers reveal that in the
pesticide sector, Gujarat has in installed capacity of 77.68 MT but produces about
36.05 MT, followed by Maharashtra with installed capacity of 41.08 MT but
producing about 32.16 MT, Andhra Pradesh produces 2.655 MT against an installed
capacity of 3.4 MT, Kerala producing 2.407 MT against an installed capacity of 4.594
MT and Karnataka producing 0.911 MT against installed capacity of 3.9 MT. This is
summarized in Table 4.
Table 3: Produc tion of Technical Grade Pesticides
Name of the Pestici de
Cap acit y ( 000' M T)
Produ ction
Ch lorp yr iph os Capta n & C aptaf ol Copp on – o xych lor id e Zin c Pho sph id e Alum in ium P hosp hat e Meth yl Brom id e Source: Annual Report 2005-06 of Ministry of Chemicals & fertilizers, Department of Chemicals & Petrochemicals
Table 4: Sta te w ise Installe d capacity Vs Production
Name of the
Installe d
capacit y
(MT/Year)
Source: Annual Report 2005-06 of Ministry of Chemicals & fertilizers, Department of Chemicals
& Petrochemicals
Pesticides are produced by chemical reactions of organic materials, which seldom go to completion. The degree of completion of organic reaction is generally very much less than those involving inorganic reactions. The law of mass actions states that in order to transform one reactant fully, the other reactant must be present far in excess in weight than the stoichometric requirement. This law is applied in practical field. As a result, the final mass of an organic reaction is associated with not only the desired product, but also untreated reactants and undesired products of side reactions or partially completed reactions. The manufactures of pesticide is hardly accomplished in one reaction, in most cases, it involves various unit processes and unit operations. The important types of unit process (chemical reactions) are: Also, the important types of unit operations (physical) are: Liquid / Liquid extraction Liquid / Liquid separation Liquid / Solid separation Gas / Solid separation In each reaction, state some raw material remain un-reacted, and some unwanted
product are formed which remain in the system. Desired products are carefully
recovered in each step from the system. Unwanted products are discarded, but not
carefully. These inevitably become pollutants in wastewater and solid waste. Some are
vented out in the atmosphere. Although in some cases some recyclable materials are
also profitably taken back in to the system. Impurities present in raw materials may also
react with one another and in many cases show up as a scum, froth or tar or simply as
un-reacted raw material. In order to understand generation of wastewater, solid waste
and emission understanding of unit process and operation is required. The typical unit
operation of chemical synthesis is depicted in Fig. 1. Within this backdrop the
manufacturing process of some of the technical grade pesticides and associated air
pollutants are discussed in the subsequent paragraphs.
Oil , coal, natural gas, electricity, steam etc.
Thermo oil, pressurised air, hydraulic oil, etc Such as catalysts, acids, alkaline, neutral salts which don't take parting the chemical reaction Recycling especially
Chemical Raw
Chemical operations /
process/ reactions and Unit
By Products for
internal or external use
Non reacted raw
materials – recovery
and reuse possible
Waste Heat
Usually different defined sources with certain flow and composition - to treat with / without reuse Solid Waste
Waste Water
Usually different defined sources with certain flow and composition - to pre-treatment and final treatment, sometimes with reuse Fig.1: Typical Unit operations of Chemical Synthesis
Process starts with the addition of Dimethyl Sulphate to Dimethyl thio phosphoramide (DMPAT) to give Methamodophos, which is acetylated with acetic Anhydride in presence of sulphuric acid to give crude acephate. Crude acephate is neutralised with ammonia solution and extracted in methylene chloride. The extracted acephate liquor is crystallised under chilled condition in presence of Ethyl acetate. Crystallised Acephate is then centrifuged and dried. The chemistry of Acephate production is stated below: Step 1: Isomerisation Step 2:Acetylation P-N-C-CH3 + CH3COOH Step 3:Neutralisation & Extraction of Acephate Liquor ammonia is slowly added under stirring to neutralize sulphuric acid and acetic acid. Liquor ammonia is added till pH is about 7. Layers are separated. Organic layer is washed with water. Aqueous layer is sent to effluent treatment plant.
Step 4:Crystallisation of Acephate Liquor Organic layer is subjected to vacuum distillation to recover methylene chloride. After
recovery of methylene choloride, mother liquor is taken in a crystallizer. Ethyl acetate is
added, stirred and crystallized Acephate is allowed to settle. Acephate is filtered and
mother liquor is taken for ethyl acetate recovery. Viscous organic mother liquor after
ethyl acetate recovery is sent for incineration. The process flow diagram of Acephate is
given in Fig. 2.
[1] Acetic Acid (50%)[2] Ammonium Sulphate Fig. 2: Process Flow Diagram of Acephate Manufacturing
Associated Air Pollutants
There is no channelised emission observed in the process of Acephate manufacturing. Because, process steps for preparation of Dimethyl thio phosphoramide (DMPAT) has been eliminated / stopped, which is the source of HCl emission as data received from the industrial units manufacturing Achephate.
Aluminium phosphide is manufactured by reacting Aluminium and Phosphorus in a closed chamber. Aluminium phosphide is formed, instantaneously liberating heat of reaction. The Aluminium phosphide thus obtained, is reduced to required size, blended with inert ingredients and converted into various tablets and pouches. The process flow diagram of Aluminium phosphide is shown in Fig. 3.
Vent P2O5 (as H3PO4 mist) WASTEWATER TO ETP Urea/MR-17 210 Kg TABLETING POUCHING Aluminium Phosphide Fig 3. : Process Flow Diagram of Aluminium Phosphide Manufacturing
2.2.1. Associated Air Pollutants
During the course of reaction, P2O5 fumes (as H3PO4 mist) generated, which are pass through scrubber, followed with mist eliminator so as to control the emission of pollutants. Also, dilute phosphoric acid is generated as a by-product by the industrial units.
Sulphur is charged in reactor then chlorine is slowly passed at controlled temperature (55o to 60oC) to form sulphur Mono Chloride. Again Chlorine is passed through Sulphur Mono Chloride to convert it to Sulphur Dichloride. Sulphur Dichloride is added to hot (86oC) Trichloro Ethylene & then Misture is heated to 135oC to form Tetrochloro Ethyl Sulphomyl Chloride (TCESCL), which is then washed with water and diluted with Toluene. Finally TCESCl is condensed with Tetra hydro phthalic imide (THPI) in presence of NaOH to give Captafol, which is centrifuged & dried.
The steps of chemical reactions for Captafol manufacturing are as follows: Sulphur Mono Chloride Preparation Sulphur Monochloride Sulphur Dichloride Preparation Tetrachloro Ethyl Sulphonyl Chloride Preparation (TCESCl) Tri-chloro Ethylene Tetrahydro Phthalic Imide Step5: Filtration & Drying 2.3.1 Associated Air pollutants
In the manufacturing of Captafol pesticide, S2Cl2 & SCl2 are formed during chlorination of sulphur and subsequent chlorination of sulphur monochloride. It is observed that there is no direct emission of S2Cl2 & SCl2. But, only chlorine emission takes place during process, which is confirmed during in-depth study.
Manufacturing process starts with chlorination of Carbon Disulphide to form CSCl4, which is washed with water & diluted with Toluene prior to condensation. After dilution CSCl4 is condensed with Tetra Hydro Pthelic Amide (THPA) at temperature less than 10oC to form Captan. Toluene is added for slurry preparation. Then the crude mass is centrifuged and then dried in rotary drier. The chemistry of Captan formation is given below: Chlorination of Carbon Disulphide Washing & Dilution of CSCl4 Tetra Hydro Pthelic Amide Filtration & Drying Process flow diagram for manufacturing of Captan is given in Fig. 4
Aqueous Phase to ETP Aqueous Phase to ETP Fig. 4: Process Flow Diagram of Captan Manfuacturing
2.4.1 Associated Air Pollutants
The air pollutants identified from the process of manufacturing of Captan are Hydrochloric Acid (HCl) and Chlorine (Cl2).
Dichloro Vinyl Cyclo propane Carboxylic Acid Chloride (DVACl) also known as Cypermethric Acid Chloride (CMAC) and Meta Phenoxy Benzaldehyde (MPBAD) are taken in an agitator reactor, in a solvent (Hexane). Sodium cyanide and water are added to the mass. Mass is agitated in reactor for the required time. At the end of reaction, the reaction mass is separated into two phases, organic layer and aqueous layer.
Organic layer containing the product, Cypermethric technical with solvent is
taken for distillation, where the solvent is removed and recycled. The final traces
of solvent, which are around 3-4%, are removed under vacuum and recycled
back. The process flow diagram is shown in Fig. 5.
Aq. CN- LAYER Cyanide Treatment) 1st Water wash1st Soda wash2nd Soda wash 2nd Water wash Aq. CN- LAYER (Cyanide Treatment) Rec. HEXANE. (Recycle) Fig. 5: Process Flow Diagram of Cypermethrin Manufacturing
DVA chloride
Acrylonitrile and Carbon tetrachloride are reacted in presence of catalyst to give Tetrachloro butyronitrile (TCBN) and the same is taken for distillation. Purified TCBN is hydrolysed with Sulphuric acid to form Tetra chloro butyric acid. The spent acid is separated, taken for despatch. TCB acid is reacted with Thionyl chloride to make TCB Acid chloride. The gases liberated are scrubbed with water to remove HCl and with Caustic to remove SO2. TCBACl is taken for distillation.
Distilled TCBACl is reacted with Isobutylene in presence of Tri Ethyl Amine to make 2-Cyclobutanone (2-CB). After recovery of solvent, it is taken for filtration. Mother liquid is taken for recycle. 2-CB powder is isomerised in presence of catalyst to give the derivative of 4-Cyclobutanone (4-CB).
4-Cyclobutanone thus obtained is reacted with Caustic solution to form Sodium salt of DVA. DVANa is acidified with HCl to make DV Acid. DVA is further reacted with Thionyl chloride to obtain DVA chloride. The gases liberated are scrubbed with water to remove HCl and with Caustic to remove SO2. DVA chloride thus obtained is taken for solvent recovery followed by distillation to make purified DVA chloride.
Metaphenoxy benzaldehyde (MPBAD)
Benzaldehyde is reacted with Bromine and chlorine in presence of EDC to form Meta Bromo Benzaldehyde (MBB). HCl generated during the course of reaction is scrubbed in water to form HCl, which is recycled. Reaction mass is washed with HCl (3-4%). AlCl3 solution formed during the wash is sold after treatment. Organic portion from above wash is treated with thio sulphate and given a water wash. Organic layer containing MBB and EDC is taken for distillation. Crude MBB thus formed is then fractionally distilled to get distilled MBB. EDC and mid fractions recovered during the distillation are recycled. Distilled MBB is then reacted with Mono Ethylene Glycol in presence of catalyst to form Meta Bromo benzaldehyde acetal (MBBA).
MBBA is reacted with phenol in presence of catalyst, KOH and Toluene to form Meta Phenoxy benzaldehyde acetal (MPBA). MPBA is further treated with caustic lye in presence of water. Aqueous layer is separated from organic layer and treated with sulphuric acid. KBr solution formed during the course of treatment is then taken for Bromine recovery. Organic layer containing MPBA and toluene is taken for hydrolysis in next stage.
MPBA in toluene is heated with sulphuric acid (98%) to form Metaphenoxy Benzaldehyde (MPBAD). MEG generated during the reaction is taken for recovery and recycled. MPBAD + Toluene are fractionally distilled to get pure MPBAD. Toluene and mid fractions recovered during the distillation are recycled.
2.5.1 Associated Air Pollutants
The air pollutants identified from the process of manufacturing of Cypermethrin are Chlorine (Cl2), Hydrochloric Acid (HCl) and Sulphur dioxide (SO2).
The process of manufacturing Dimethoate is furnished below alongwith process chemistry: Step 1: DDPA preparation Phosphorous penta Sulphide reacts with methanol to produce Dimethyl Dithio Phosphoric Acid, which is used in next step.
Dimethyl Dithio Phosphoric Acid Step 2: Na-DDPA preparation 20% Sodium carbonate is added to the DDPA solution prepared as above till pH 7.0. The layers are separated. The toluene layer goes for purification and the aqueous layer containing sodium salt of DDPA is taken for next step.
Step 3: Methyl monochloro acetate (MMCA) Monochloro Acetic Acid, Methanol and Catalytic amount of sulphuric acid are refluxes and MMCA formed is distilled out at 140oC and used for the next step.
CH2ClCOOH + CH3OH CH2ClCOOCH3 + H2O Step 4: Condensation Na-DDPA prepared as in step 2 and MMCA prepared as in step 3 are mixed and heated for four hours at 60oC under stirring. After the reaction is over same is washed with water and carried out amidation reaction with MMA at –2oC. The reaction mass is neutralised to pH 5.5 – 6.0 with 10% sulphuric acid and the product is extracted with ethylene dichloride solvent. The solvent is then removed from the separated organic layer under vacuum at 70 -75oC and dimethoate is packed.
The process flow diagram is shown in Fig.6.
2.6.1 Associated Air Pollutants
The air pollutants identified from the process of manufacturing of demethoate are Hydrogen Sulphide (H2S) and Methanol (CH3OH). Methanol is not reported by the industrial units. NaCl Solution to ETP Aqueous Layer to ETP Fig. 6: Process Flow Diagram of Dimethoate Manufacturing
2,4 – Dichlorophenoxy acetic acid (2,4 – D)
Phenol is chlorinated to get Dichlorophenol, which is condensed with mono chloro Acetic Acid in presence of Alkaline solution to get 2,4-D Sodium. Astirrable slurry of 2,4-D Sodium is prepared and its pH adjusted to 1.0 – 1.2 by adding 98% Sulphuric acid. 2,4-D acid thus formed is filtered, dried & packed. The process flow diagram is shown in Fig. 7.
1. PHENOL 2. ACETIC ACID Fig. 7: Process Flow Diagram of 2, 4 – D Acid Manufacturing
2.7.1 Associated Air Pollutants
The air pollutants identified from the process of manufacturing of 2, 4 – D Acid are Hydrochloric Acid (HCl) and Chlorine (Cl2). In the first step Tri-Methyl Phosphite (TMP) is slowly allowed to react chemically with tri chloro acetaldehyde at controlled conditions of temperature and at ambient pressure to produce crude DDVP. Product obtained from step 1 is purified under vacuum by film evaporator to get final product having purity around 95%. The chemistry of DDVP manufacturing process is stated below: CCl3 CHO + (CH3O)3 P  (CH3O)2 P-O-CH = CCl2 + CH3Cl Chloral TMP DDVP Methyl Chloride The process flow diagram for manufacture of DDVP is shown in Fig. 8.
To liquification Fig. 8: Process Flow Diagram of D.D.V.P. Manufacturing
2.8.1 Associated Air Pollutants
Methyl chloride (CH3Cl).is identified air pollutant from the manufacturing process of D.D.V.P.
2.9 Ethion
Phosphorus penta-sulphide and absolute alcohol are reacted to produce diethyl dithiophsophoric acid (DDPA), which is reacted with caustic to form sodium salt of DDPA. This salt and methylene dibromide are reacted together to produce Ethion. The manufacturing process step by step is given below alongwith process chemistry: Step 1: Preparation of Dithioacid Toluene is taken in the reactor and phosphorus pentasulfide is added under stirring. Temperature is raised and ethanol is slowly added under controlled temperature conditions. During the reaction, hydrogen sulphide gas is evolved. It is absorbed in dilute sodium hydroxide solution in a scrubber.
Step 2: Sodium salt preparation: With Dithioacid formed in step No. 1, sodium hydroxide solution is added slowly and temperature is controlled by circulating cooling water in the jacket of reactor. At the end of reaction, two layers are separated. Aqueous layer is taken for next step and organic layer is sent for toluene recovery.
Step 3: Condensation To the aqueous solution of sodium salt of dithioacid, methylene bromide is added, and temperature is raised under maintain condition. At the end of reaction, layers are separated. Aqueous layer contains sodium bromide and organic layer contain product is steam stripped to remove impurities.
The process flow diagram of Ethion manufacturing is given at Fig. 9.
INDUSTRIAL ALCOHOL BY-PRODUCT - SODIUM BROMIDE SOLUTION HYDROGEN SULPHIDE BY-PRODUCT SODIUM SULPHIDE Fig. 9: Process Flow Diagram of Ethion Manufacturing
2.9.1 Associated Air Pollutants
Hydrogen Sulphide (H2S) and Ethyl Mercaptan (C2H5SH) are identified air pollutants from the manufacturing process of Ethion.
The manufacturing process for Endosulphan alongwith process chemistry in sequence is stated below: Step 1: Hexa-chloro-cyclo-pentadiene (HCCP) is reacted with 2-Butene 1:4-Diol in presence of carbon tetra chloride as solvent to form Het Diol.
Step 2: Solid Het Diol is separated from mother liquor by centrifuge.
Step 3: Het Diol is then reacted with Thionyl chloride in Carbon tetrachloride solvent to give Endosulphan solution.
Step 4: Carbon tetrachloride is recovered by distillation to give molten Endosulphan, which is flaked and packed The process flow diagram of Endosulphan manufacturing is given at Fig. 10.
2.10.1 Associated Air Pollutants
Hydrochloric Acid (HCl) is identified air pollutant from the manufacturing process of Endosulphan.
Recovered Solvent Recovered Solvent Endosulphan (Technical) Fig. 10: Process Flow Diagram of Endosulphan Manufacturing
Para chloro toluene (PCT) is chlorinated to Para chloro benzyl chloride (PCBC). The HCl and Cl2 gases liberated are scrubbed with water and caustic solution. The chlorinated mass is distilled to remove excess PCT. PCBC is reacted with Sodium cyanide to form PCCN. The aqueous layer is treated with Sodium hypochlorite to reduce cyanide content.
The para chloro benzyl cyanide is reacted with Isopropyl bromide in presence of caustic to form PCAN. The reaction mass is washed with water. Aqueous layer is taken for NaBr recovery. The organic layer is taken for fractional distillation. PCAN thus obtained is hydrolysed with sulphuric acid to form PCA.
PCA is further reacted with Thionyl chloride to obtain PCA chloride. The gases liberated are scrubbed with water to remove HCl and with caustic to remove SO2. PCA chloride thus obtained is condensed with MPBAD, alongwith sodium cyanide and washed with water. Organic mass containing solvents is taken for solvent distillation. Fenvalerate (Tech) thus obtained is packed in drums.
The aqueous layer containing excess cyanide is treated with Sodium
hypochlorite and is drained to ETP. The process flow diagram is given at Fig.
11A to Fig. 11 E
PCT - 1908 KgCATALYST - 9.54 Kg TO SCRUBBER (30% HCl) DCM - 19.08 KgCl2 - 279.84 Kg HCL  - 143.1 Kg (100%) Fig. 11 A. Process Flow Diagram (step PCT to D/PCBC)
D/PCBC(96%) - 596 Kg NaCN - 200 KgH2O - 200 KgCatalyst - 22.4 Kg 1st. Dilution water - 440 Kg1st. Wash Water - 900 Kg (1st. Dilution + 1st. Wash)CN- Effluent (For CN- Treatment) Fig. 11 B. Process Flow Diagram (step D/PCBC to C/PCCN)
C/PCCN (96%) - 543.543 Kg IPBr. (98% min.) - 427.284 KgCatalyst - 34.32 KgCaustic Lye (47%) - 1029.6 Kg 1st. Dilution water - 600.6 Kg1st. Wash water - 1115.4 Kg Aq. NaBr - 1716 Kg (For Br2 - Recovery) Effluent to ETP - 1115.4 Lit.
- 1376.232 Kg.
Residue (Incineration) Fig. 11 C. Process Flow Diagram (step C/PCCN to D/PCAN)
D/PCAN (96%) H2SO4 (98%) H2O EDC Spt. H2SO4 (Sell) Half part to StorageTank Half part for Isolation H2O Caustic Lye (47%) EDC Hexane HCl Rec. Hexane 1st Fraction D/PCACl Residue (Incineration) Fig. 11 D. Process Flow Diagram (step D/PCAN to D/PCACl)
CN - Effluent (CN- Treatment) CN - Effluent (For CN- Treatment) FENVALERATE (TECH.) Fig. 11 E. Process Flow Diagram of Fenvalerate
(step D/PCACl to Fenvalerate technical)
2.11.1 Associated Air Pollutants
Hydrochloric Acid (HCl), Chlorine (Cl2) and Sulphur Dioxide (SO2) are identified air pollutant from the manufacturing process of Endosulphan.
The process description for manufacturing of Malathion alongwith process chemistry is furnished below: Step 1: DDPA preparation Phosphorus penta sulphide reacts with methanol to produce Dimethyl-Dithio-phosphoric Acid (DDPA).
Step 2: DEM preparation Maleic anhydride is reacted with ethyl alcohol in presence of Benzene and catalytic amount of sulphuric acid. The water formed is removed azeotropically and then the solvent is distilled out. The diethyl-maleate (DEM) is neutralised and purified.
Step 3: Malathion preparation It is manufactured by the condensation reaction (at 70-80oC) of dithio-phophoric acid (DDPA) and diethy-maleate (DEM) in the presence of catalyst. The excess acidity is neutralised using dilute caustic solution and then washed with water. The solvent and moisture is removed under vacuum and dry Malathion tech is packed. P2S5 + 4CH3OH2 Process flow diagram is shown in Fig. 12.
NaOH + WATER142 335 SPENT NaOH SOLUTION Reaction Mass1458 MALEIC ANHYDRIDE MALATHION TECHNICAL Fig. 12: Process Flow Diagram of Malathion manufacturing
2.12.1 Associated Air Pollutants
Hydrogen Sulphide (H2S) is an identified air pollutant from the manufacturing process of Malathion.
Methyl Bromide
Methyl Alcohol and Bromine are reacted in a glass lined reactor. After completion of Bromination, distillation of Methyl Bromide is started. As the boiling point of Methyl Bromide is 4.5º C, chilled brine having temperature less than – 8º C is circulated in the Reflux condenser as well as Product condenser.
Methyl Alcohol + Bromine  Methyl Bromide A dense ash (Na2CO3) column is used to prevent carry over of un-reacted
bromine if any. When the colour of the vapour is colourless the reflux condenser
chilled brine flow is controlled to allow the vapour to flow to product condenser.
The Methyl Bromide vapour gets condensed in the product condenser and flows
to the receiver tank. Chilled brine is circulated in the Jackets of the receiver
tanks. The process flow diagram for manufacture of Methyl Bromide is shown in
Fig. 13
Chilled brine inlet Chilled brine inlet Chilled brine outlet Chilled brine outlet Fig.13. Process Flow Diagram of Methyl Bromide Manufacturing
2.13.1 Associated Air Pollutants
There is no reported emission from closed reaction of Methyl Bromide manufacturing.
Manufacturing of Monocrotophos, following steps are involved: Step 1: Chlorination of MMAA: Chlorination of Monomethyl acetoacetamide (MMAA), water and methanol are taken and cooled to 25oC to 30oC temperature then chlorine gas is passed. After the reaction is completed, the reaction mass is neutralised to pH 7.0 with 20% Sodium Carbonate solution. The solvents (methanol & some amount of water) and distilled out and chlorinated product is extracted with EDC. The water is removed by refluxing the chlorinated product in EDC with simultaneous water removal. The reaction mass is taken for the next step.
Step 2: Condensation The chlorinated product (MMACl) is condensed with Trimethyl phosphite (TMP) to form Monocrotophos Technical.
The process flow diagram is shown in Fig. 14.
CH3COCH2CONHCH3 + Cl2  CH3COCHClCONHCH3 + HCl Mathanol + Water 1544 Kg Urea 100 Kg.
Chlorine 205 Kg.
CO2 (g) 27 Kg.
Reuse (16% Water) 1128 Kg Recovered Methanol (50%) 630 Kg Recovered EDC 1039 Kg NaCl + Water to ETP Methyl Chloride 125 Kg.
TMP + EDC + Impurities to EDC Recovery Fig. 14: Process Flow Diagram of Monocrotophos Manufacturing
2.14.1 Associated Air Pollutants
Hydrogen Chloride (HCL) and Methyl Chloride (CH3Cl) are identified air pollutant from the manufacturing process of Monocrotophos.
Cumene is nitrated with a mixture of nitric acid and sulphuric acid to produce
nitrocumenes. Nitrocumenes are reacted with sulphur and caustic soda to give
cumidine. Cumidine is reacted with urea and di-methyl amine in presence of
solvent to produce isoproturon. Isoproturon is isolated by filtration and dried then
pulverised and packed. The process flow diagram is given at Fig. 15
SPENT ACID FOR SALE WATER, CAUSTIC LYE RECOVERED NH3 Reuse /Sale FROM STEAM DISTILLATION to ETP DRYING, PULVERIZING & PACKING Fig 15: Process Flow Diagram of Isoproturon Manufacturing
2.15.1 Associated Air Pollutants
Ammonia (NH3) is an identified air pollutant from the manufacturing process of Isoproturon.
Orthoaminophenol is reacted with urea in solvent medium to get benzoxozolone, which is then chlorinated in solvent medium, and formaldehyde is added to get hydroxy methychloro benzoxazolone (HMCB). HMCB is chlorinated using dry HCl gas to get chloromethyl chlorobenzoxazolone (CMCB) which is extracted in methylene chloride medium. P2S5 is reacted with ethyl alcohol to get diethyl dithiophosphoric acid (DDPA) which is neutralised with caustic soda to get sodium salt of DDPA. This sodium salt and CMCB are reacted to get crude phosalone. P2S5 + 4C2H5OH  2 (Na salt of DDPA) The process flow diagram for manufacture of Phosalone is shown in Fig. 16.
2.16.1 Associated Air Pollutants
Ammonia (NH3), Hydrochloric Acid (HCl) and Hydrogen Sulphide (H2S) are the identified air pollutants from the manufacturing process of Phosalone.
Fig. 16: Process Flow Diagram of Phosalone Manufacturing
Phosphorus pentasulfide and ethyl alcohol are reacted slowly in the presence of
Diethyl thio phosphoric acid (DETA) heel at 60-65º C. Hydrogen sulphide
evolves from the reaction mixture. The gas is scrubbed with caustic lye. It gets
converted to Di- sodium sulphide and sodium hydrogen sulphide, which has a by
–product value. After the completion of reaction, the product is charged in
another reactor through a sparkler filter. The product of step one is reacted with
Formaldehyde and Ethyl Mercaptan at room temperature to produce crude
phorate. This is a condensation reaction. Crude Phorate thus obtained from
step I is washed using washing soda and steam stripped to remove volatile
organics and moisture. The process flow diagram of phorate manufacturing
process is show in Fig. 17.
S S
SH (NaOH Scrubber) (Sodium hydrogen sulphide) Diethyl thio phosphoric acid DETA + 2HCHO + 2 C2H5SH (Formaldehyde) (Ethyl Mercaptan) 2.17.1 Associated Air Pollutants
Hydrogen Sulphide (H2S) and Ethyl Mercaptan (C2H5SH) are the identified air pollutants from the manufacturing process of Phorate.
Phosphorous Penta Sulphide Industrial Alcohol Hydrogen
DTA Reactor
Para Formaldehyde By Product –
Sodium sulphide
Phorate Reactor
Water Treatment Reactor
Organic layer and treated
water to effluent treatment
plant and incinerator
Fig. 17: Process Flow Diagram of Phorate Manufacturing
Diethylacetoacetamide (DEA) is chlorinated by using chlorine. HCl gas removed by degassing is scrubbed to obtain HCl as by-product. Reaction mass is neutralised using sodium carbonate and dichloro diethyl aceto acetamide (DDA) present in the organic layer is removed. DDA is diluted in solvent, heated to 100oC and Trimethyl phosphite (TMP) is added. From the reaction mass, methyl chloride gas is removed by degassing and phosphamidon technical is obtained. The process flow diagram for manufacture of Phosphamidon is shown in Fig.18
2.18.1 Associated Air Pollutants
Hydrochloric Acid (HCl) and Methyl Chloride (CH3Cl) are the identified air pollutants from the manufacturing process of Phosphamidon METHYL CHLORIDE 0.168 HAZARDOUS WASTE TO PHOSPHAMIDON TO INCINERATOR Fig.18: Process Flow Diagram of Phosphamidon Manufacturing
Zinc dust is charged in a reactor and heated. Phosphorous is added slowly in
to the reactor. Once the reaction is completed, Zinc phosphide mass is
crushed in ball mill and packed into desired containers. The process flow
diagram for manufacture of Zinc phosphide is shown in Fig. 19
2.19.1 Associated Air Pollutants
Phosphorus Pentaoxide (P2O5 as H3PO4 mist) is identified air pollutants from the manufacturing process of Zinc Phosphide.
Fig. 19: Process Flow Diagram of Zinc Phosphide Manufacturing
AIR POLLUTANTS FROM PESTICIDE INDUSTRY
Emissions Profile in Pesticide Industries
In general, process emissions can be classified into channelised and fugitive emissions. The channelised emission is a point source emission from process operations and the fugitive emission is an uncontrolled emission from storage tanks/drums, spills, leaks, overflows etc. In order to identify the various sources of process emissions and their control systems in pesticide industries a questionnaire survey and in-depth studyof some pesticide industries were conducted. The manufacturing process for a product is a combination of various unit operations and unit process. The material balance of the reactants and products gives the characteristics and quantity of emissions. However, their quantity is constrained by the efficiency of conversion of the system. Chances of pure process emissions of only one gaseous pollutant are very less. The process emissions are contaminated by other vapours of raw materials, solvents and also some times product of the unit operations. Theoretical emission of pollutants is difficult to compute. Very often during the unit operations wastewater and solid waste are separated, whereas waste gas is directly released from the reactions itself. It is observed that no process or production site is directly comparable to another. However, there are some forms of similarities with respect to air pollutants with product specific group such as organochlorine, organophosphate etc. Based on the studies conducted on various pesticide manufacturing units,
as the identified pollutants associated with products are given in Table 5.
Table 5: Product and associated priority pollutants
Name of the Pollutants
Aluminium phosphide P2O5 fumes (as H3PO4 mist) Cl2 , HCl and SO2 Name of the Pollutants
Dichlorvos (D.D.V.P) P2O5 as H3PO4 mist Solvents
Besides the air pollutant listed in Table 5, the pesticide manufacturing
processes use various types of solvents for separation of desired product
from other chemicals. The list of solvents for various pesticides
manufacturing process is given in Table 6. Spent solvent are recovered
either recycle in the same system or reuse for other purposes. The un-
recovered solvents are generally incinerated in the pesticide industries in
India. The loss of solvent is not so significant. A well designed LDAR
programme can prevent loss due to fugitive emissions.
Table 6: List of Solvents used in manufacturing process of pesticides
Name of the
Product list
Divenyl acid chloride, Acetamiprid, Imidachlorprid, Tetrachloro Alphamethrin, Permethrin Name of the
Product list
Acephate, 2,4-D acid, Mancozeb Acepate, 2,4-D acid Malathion, Diethyl Aniline, Dimdethoate, Lindane Endosulfan, 2,6, Dichloro pyridine, Divenyl acid isoproturan, Tetrachloro Cypermethrin, Alphamethrin, Permethrin Cypermethrin, Alphamethrin, Permethrin, Devrinol Malathion, Phorate, Ethion, Terbufos, Diethyl Aniline, Ethyl chloride, Phenthoate, Lindane Captan, Dimethote, Monocrotophos, Meta Bromo Phorate, Tebufos Deltamethrin, Fenvalerate, Cypermethrin, Divenyl acid chloride, Iso proturon Isopropyl alcohol Delatamethrin, Phosphamidon, Imidachlorprid Phenthoate, Methyl Parathion,Temephos Acephate, Deltamethrin, Propiconazole Mepiquate chloride 2,4-D acid, Meta Phenoxy Denzaldehyde D-Allethrin, Carbendazin For formulations, Captafol, Captan, Cypermethrin, Ethion, Malathion, Dimethote, Fenvalerate, 5-Amino Salicylic acid, Andpa, Meta Phenoxy Denzaldehyde, Permethrin, Benfuresate, d-Allethrin, Penpropathrin, Tenephos, Metconazole Cypermethrin, Divenyl acid chloride, Benfuresate, Permethrin, Deltamethrin Benfuresate, Phosphamidon, Pendimethalin, Prioritisation of air pollutants for control
Considering the health risk or damage to environment and effects on man made assets and the volume of discharge, a combinatory tree is evolved for prioritisation or selection of air pollutant for control, has been identified. This is stated below : Most priority Air pollutant
Volume of
Medium priority Air pollutant
Less priority Air pollutant
Volume of
Discharge
Least priority Air pollutant
An exercise has been made with said combinatorial tree, accordingly the priority air pollutants identified are listed below: Hydrogen Bromide (HBr) Hydro Chloric Acid (HCl) Hydrogne Sulphide (H2S) Methyl Chloride (CH3Cl) Phosphorous Pentoxide (P2O5 as H3PO4 mist) Sulphur Dioxie (SO2) Toxicity and Health Impact of Priority Pollutants
Summary of toxic properties of priority pollutants identified from the
studied process are given in Table 7.
Table 7: Properties and Health impact of some priority pollutants
Physical & Chemical
Exposure, odour and
Colourless, stable at room TWA 50ppm, Ammoniacal Exposure can cause Anhydrous strong, high corrosive in coughing, chest pains react presence of Cu and its difficulty in breathing. exothermically with acids alloys. Slightly corrosive Repeated Anhydrous in presence of Al and Zn. overexposure ammonia decompose to Very slightly corrosive in cause permanent lung hydrogen and nitrogen presence of Mild Steel. gases above 450° C. Non in edema and chemical presence of glass or pneumonitis. be Stainless steel (304 or cause serious damage lowered by contact with 316) certain metals.
TLV 0.5 ppm, pungent Can cause itching and extremely reactive can suffocating bleach like burning of the eyes, react violent with many odour, strongly corrosive nose, throat. At high combustible materials and to most metals in the concentrations chlorine other chemicals including presence of moisture is respiratory poison.
stable TWA 3 ppm, Pungent Toxic- causes serious incompatible with strong suffocating oxidising agents, strong corrosive Hazardous common Bromine and Hydrogen slightly TLVTWA 5 ppm, irritating Toxic may be fatal if odour inhaled, severe irritant, incompatible with alkalis threshold 0.77 ppm, and very dry gaseous hydrogen inhalation, ingestion or chloride can be handled through skin contact.
in elevated temperature the corrosion rates increase. Commonly used metals are Carbon steel alloy 400, 300, series stainless steels, alloy 600 and Nickel 200 Colourless gas, stable, TWA 10 ppm, smell of High toxic may be fatal highly inflammable, may rotten eggs, corrosive to if inhaled. Skin contact form explosive mixture with air incompatible with oxidising agents, oxides and metals Colourless gas, stable, TWA irritating Toxic-high incompatible with strong pungent non concentrations are fatal oxidising corrosive agents, moisture Zinc and materials except Zn when its alloys dry; corrosive when wet stable TWA 0.5ppm, extremely Highly toxic, affects the repulsive central nervous system condition, decomposition smell. Odour threshold is of chemical can emit 0.001 ppmcarbon hydrogen sulphide and sulphur dioxide AVAILABLE CONTROL TECHNOLOGY TO PREVENT AND CONTROL OF
AIR POLLUTANTS FROM PESTICIDE INDUSTRY
Principle of Air Pollution Control Technology
Principle of air pollution control technology can be broadly classified into following groups. Separation techniques Gas solid separation Liquid-liquid separation Gas liquid separation Conversation to harmless end product Thermal destruction These are illustrated below. 4.1.1 Separation techniques
In case of gas solid separation, the following techniques are employed: Wet dust scrubber Fabric filter including ceramic filter With respect to liquid-gas or liquid-liquid separation, the following techniques are considered: 4.1.2 Thermal destruction
Thermal destruction is generally used, when toxic and carcinogenic chemicals are emitting from the process. The thermal destruction technology generally used is stated below: Thermal oxidation Catalytic oxidation 4.1.3 Conversion to harmless product
These techniques are used for organic pollutants; however, these techniques are not used in India. The techniques are: 4.1.4 Combination approach
The technique for cleaning of flue gases can combine both recovery and abatement. The techniques are as follows: Dry sorbent injection Semi dry sorbent injection Selective non-catalytic reduction (SNCR) of NOx Selective catalytic reduction (SCR) of NOX In order to provide an overview, all available techniques are compiled in
Fig. 20. To this purpose it appears appropriate to distinguish between two
sources of waste gases:
"Normal" temperature processes, such as production, handling or work-up processes, with the main contaminants: Volatile organic compounds such as solvents Inorganic gases, such as hydrogen halides, hydrogen sulphide, ammonia, carbon monoxide Particulates in the form of dust Incineration processes, with main contaminants: Particulates in the form of ashes and dust, containing soot, metal oxides Fuel gases such as carbon monoxide, hydrogen halides, sulphur-oxygen compounds (SOx), nitrogen-oxygen compounds (NOx) reactions, unit / work-up operations, handling Emission from combustion / incineration processes Electrostatic precipitatorFabric filterTwo stage dust filterHigh efficiency filter Mist filter Dry, semi-dry and wet sorption SO2, HCl, HF, HBr compounds (incl. Nox, SO HCl, HF, HBr, Cl2) Bio filtrationBio scrubbing Bio tricklingThermal oxidationCatalytic oxidationFlaringCondensationWet scrubberSeparatorCycloneElectrostatic precipitatorFabric filterTwo stage dust filterHigh efficiency filter Mist filterSNCR/ SCR Fig. 20. Available techniques for end-of-pipe treatment of waste gases from chemical industries in relations to type of contaminants
Arising waste gases are treated by techniques where: The waste gas content is recovered and either recycled to the original process or used in another process as raw material or energy carrier The contaminants are abated.
Compounds normally worth to recover comprise: VOC, recovered from, solvent vapours or vapours of low-boiling products VOC used as energy carrier in incinerators or boilers Hydrogen chloride, transferred into hydrochloric acid Ammonia to recycle into the production process Sulphur dioxide, transferred into sulphuric acid, sulphur or gypsum Dust containing higher amounts of solid raw products or end products Control Technologies Adopted in India
On the basis of information received from various industries either in
questionnaire survey or collected during in-depth study of pesticides
industries, the control technologies adopted to control the identified gaseous
pollutants are given in Table 8.
Table 8: Control technologies adopted in Indian industries
 Water Scrubber,  Caustic Scrubber, Water / Caustic Scrubber  Caustic Scrubber, Water / Caustic Scrubber  Charcoal Bed Scrubber, Liquification, filling and /or Combustion  Scrubber with NaOCl media Scrubber with NaOH media Charcoal Bed Scrubber  Water/Caustic Scrubber Water Scrubber (Ring jet scrubber) + Mist Eliminator + Demister  Mist Eliminator Two Stage Water Scrubber  Recovery System  Channelised Emission was not observed, because this chemical (solvent) is used in less quantity in the manufacturing  Caustic Scrubber  Incinerator / chemical reaction compounds, non recovered solvents Efficiency Evaluation of Existing Pollution Control Technologies
The concept of control efficiency is the limitation of emissions into the atmosphere by the use of air pollution control equipment systems. The efficiency of pollution control technology / system is defined as the ratio of the quantity of emissions prevented from entering to the atmosphere by the control device to the quantity of emissions that would have entered the atmosphere (quantity input to the control device); if there had been no control.
The efficiency of gas cleaning devices is expressed in a variety of ways, including control efficiency, penetration, and decontamination factor. The most common means for expressing the efficiency of performance is in terms of the control efficiency, which is defined as the ratio of the quantity of pollutant prevented from entering the atmosphere by the control device to the quantity that would have been emitted (inlet quantity to the gas cleaning device) to the atmosphere had there been no control device.
Efficiency (η) = Collected / Inlet = C/I = (Inlet – Outlet)/Inlet = (I-O)/I Penetration is defined as the ratio of the amount of pollutant escaping (penetrating without control) the gas cleaning device to the amount entering.
Penetration (P) = Outlet / Inlet Hence penetration focuses attention upon the quality of the emission stream, but in reality it is actually another way of looking at control efficiency. Since Efficiency (η) = 1 – [outlet / inlet] For a control efficiency of 99.999% (i.e., E = 0.99999), the penetration is 0.00001, or 10-5. Alternatively, efficiency can be expressed as the decontamination factor (DF), which is defined as the ratio of the inlet amount to the outlet amount.
= Inlet / Outlet = 1 / (1 – E) For a percentage control efficiency of 99.999%, DF is 105. The logarithm to the base 10 of the decontamination factor is the decontamination index. In the numerical example above, this index is 5.0. These efficiency terms are used to represent the overall efficiency of control of a single device or any combination of control devices.
Based on the data obtained from the industry and also monitored / measured
during the in-depth study, it is found that the control system as presented in
the Table 9 are suitable for identified priority pollutants on efficiency point of
view.
Table 9: Suitable Control Systems for Priority Pollutants
Water/Caustic Scrubber Water/Caustic Scrubber Liquification system and/or Incinerator Scrubber with NaOH media Water/Caustic Scrubber Water Scrubber (Ring jet scrubber) + Mist Eliminator + Demister Two Stage Water Scrubber Adsorption Bed (Charcoal or Molecular Sieve) After review of available and adopted control technologies for the control of identified gaseous pollutants, it is found that the technologies based on absorption and chemical reaction are being commonly used to control the gaseous pollutants e.g. HCl, H2S, SO2, P2O5 (as H3PO4), Cl2, NH3 and HBr. In case of H2S, adsorption and incineration technology is also adopted by some pesticide industry. To control the emission of CH3Cl, condensation (liquification) and incineration system is observed in one or two large scale industry. Description of Various Treatment Techniques
In the previous paragraph, it is indicated that the absorption (scrubber) generally used as air pollution control devices in India for pesticides industry. However, incinerator is also used for destruction of odorous compounds or un-recovered solvents, in some occasion chemical oxidation is also used for abatement of odorous compounds. Condensation is used as an intermediate step for recovery of chemicals before using cleaning up technology such as incinerator. In this paragraph, an attempt is made to describe the most commonly used techniques such as absorption, condensation, chemical reaction and incinerator as air pollution control devices for controlling priority pollutants in pesticides manufacturing industries in brief. There are various techniques available for recovery and abatement, however, concerning most important techniques for pesticide manufacturing industries to control priority (gaseous) pollutants emission are (i) absorption, (ii) adsorption, (iii) condensation, (iv) chemical reaction and (v) incineration. 4.4.1 Absorption
The identified priority pollutants from the pesticide process / operation can be efficiently removed using suitable scrubbing liquor in a mass transfer device. The liquor and gas can contact each other while both are flowing in the same direction (co-current flow), in opposite directions (counter current flow), or while are flows perpendicular to the other (cross flow). The scrubbing liquor used for the removal of gaseous pollutants can be by-product, in the form of slurry or a chemical solution. In chemical engineering terminology the alternate terms for scrubbing is absorption.
Absorption is a diffusion-controlled, gas-liquid mass transfer process. The efficiency of absorption in air pollution control is governed by the ease with which contaminants can be transferred through the interface into the liquid face. Absorption is enhanced by high diffusion rates, high solubility, large interfacial areas and turbulence. The gaseous containing vapours are scrubbed with water or liquid in which they are soluble. Scrubbing can be carried out in spray columns, packed bed columns, plate columns, floating-bed scrubbers and liquid-jet scrubber or venturi scrubbers. With the proper choice of operating conditions, almost complete removal of gaseous vapour is possible by this method.
Absorption is carried out in variously designed scrubbers. The various designs of scrubbers are based on the consideration to provide maximum contact between absorbent and the gas so as to achieve a high efficiency of gas removal. An account of some common type of scrubbers is given below: a)
Packet Tower Scrubber
The design of a packed tower scrubber is given in Fig. 21. It consists
of a long tower packed with a suitable inert packing material such as
polyethylene. The absorbent trickles down from the top to downward,
while the gases pass in the opposite direction from downward to the
top, thus allowing the maximum reaction time. The presence of
packing material makes the absorbent to trickle down in thin films to
provide maximum surface area for contact. The packed tower is
usually more economic for corrosive gases and vapours in view of the
lesser quantities of corrosion resistant materials required for its
construction.
b)
Plate Tower Scrubber
The construction of a plate tower scrubber is shown in Fig. 22. It
consists of a long vertical chamber fitted with perforated circular plates
at equal spacing. The gases or vapours pass from downward to the top
of the tower making a contact with the liquid present on the each
perforated plate. The liquid do not fall through the pores on the plates
as it is held by the pressure created by the velocity of the gases. Each
plate is provided with a pipe to carry the excess absorbent downward
from plate to plate. The plate towers are most suitable when a frequent
cleaning is required particularly in case of the liquid which after
absorption contains high quantities of particulates and relatively
insoluble and offensive gases.
Spray Tower Scrubber
The design and construction of these scrubbers is given in Fig. 23a to
Fig. 23c. In these types of scrubbers, the liquid is sprayed on the
pollutant gas that provides the turbulence to the gases for better
absorption. The method is best suited for highly soluble and offensive
gases. The design of the scrubber can be so made as to give a
centrifugal force to both liquid spray and the gas to achieve maximum
contact between the two for higher efficiency of removal. The spray
tower scrubber can also be used for removal of both solid and liquid
particulates.
Liquid Jet Scrubber
The device is most suitable for the condensable gaseous pollutants.
The scrubber is shown in Fig. 24, and consists of two vertical
chambers. In one of the chambers, a liquid jet is sprayed which
atomizes and produces small droplets of the absorbent. Gases are
also introduced into the same chamber from the upper end. Non-
condensable clean gases are removed from the other chamber.
Agitated Tank Scrubber
The effluent gases, in this type of scrubber, are agitated together with
the absorbent in a tank against baffle plates fitted on the sides of the
tank as shown in Fig. 25. The turbulence caused by stirring provides
greater absorption efficiency when particulates are also present.
Fig. 21:- Packed Tower Gas Scrubber
Fig. 22: Plate Tower Gas Scrubber
Fig. 23 (a) to (c) : - Spray Tower Gas Scrubbers
Fig. 24: Liquid Jet Scrubber
Fig. 25: Agitated Tank Gas Scrubber
All these scrubbers described above, operate efficiently at a temperature below 100°C that avoids the undue loss of the absorbent by evaporation, and keeps it in the liquid state. For this, the scrubbers are always preceded by some cooling devices to bring down the temperature of effluent gases to the desired level. The treated gases have always a lower temperature, and contain large quantities of water vapours and absorbent droplets. Demisters or some other suitable devices are installed in sequence after the scrubber to remove water vapours and the traces of the absorbent from the effluent gases. Reheating of the gases is also necessary in most cases to provide required buoyancy to the gases for their escape from the long stacks.
Condensation is best for vapours with reasonable high vapour pressure. In these process volatiles gases and vapours are controlled. Condensation may be useful for primary recovery before final cleanup with another method such as adsorption and incineration of gas. In the condensation process gases were cooled to achieve adequate condensation. Fog occurs when the rate of heat transfer appreciably exceeds the rate of mass transfer. When fog formation is unavoidable, it may be removed by high efficiency moist collector designed for 0.5-5µg droplets. Condensation procedures were normally used in the organic chemical process.
Odours of many organic compounds can be destroyed by strong oxidants such as KMnO4, HNO3, H2O2, K2Cr2O7 and hypochlorite solution. Conversion of HCl to NH4Cl is an example of changing a gas to a particulate (as by-product). Use of alkaline scrubbing medium to collect acidic gases is a way of enhancing the collection of an absorption process. In general, gaseous pollutants were collected easily by chemical reactions.
Incineration Technology with Air Pollution Control Device
Incinerator is a versatile process. Organic materials are destroyed the organic molecular structure by oxidation or thermal degradation. Incineration provides the highest degree of destruction and control for a broad range of hazardous substances. Design and operating experience exists and a wide variety of commercial incineration system are available, which are stated below: Liquid injection; Fluidised bed incinerator; and Pyrolysis bases incineration In India, it is observed that selection of incinerator technology mainly guided
by physical state of hazardous waste generated by the pesticides industry.
The incinerator technology adopted by pesticides industries is given in Table
10.
Table 10: Incinerator Technology adopted by Pesticides Industries
% share Technology adopted Only liquid waste Liquid injection (horizontal) liquid with some Only solid waste (solid & semi solid) Typical air pollution control devices for controlling different pollutants from an
incinerator are given in Table 11.
Table 11:
Air Pollution Control Devices for Controlling Different
Pollutants
Air pollution control devices (APCDs)
Acid gases, Mercury, Dioxin, Packed towers, spray dryers or dry and Furan Emission Particulate and Heavy Metal Venturi electrostatic precipitators (ESPs) or fabric filters Oxide of Nitrogen Emission Selective non-catalytic reduction (SNCR) and selective catalytic reduction (SCR) Adsorption
Besides the techniques stated above on air pollution control system of pesticide, adsorption technique has a large potential too. Adsorption is a surface phenomenon by which gas or liquid molecules are captured by and adhere to the surface of the solid adsorbent. It is desirable for removal of contaminant gases to extremely low levels (<1ppmv) and handling large volume of gases with quite dilute contaminants. It may be used alone or along with other methods, in combination, it is usually the last step of clearing the exhaust gases.
Adsorption is used to concentrate (30-50 folds) or store contaminants until they can be recovered or destroyed in the most economical manner. In the case of solvent recovery, studies have shown that the value of solvent recovered will often pay the total annualized cost of the adsorption system. Adsorption is also used to prevent the release of odorous or otherwise offensive organic gases associated with rendering, glue manufacturing, pesticide production, food processing etc.
The adsorbents used to adsorb gases and reduce odour should have large
surface area and pore volume. The adsorption of the gases is also dependent
on other factor e.g. temperature, molecular polarity and chemical nature of
adsorbent surface. Some of the adsorbents commonly used in air pollution
control are activated carbon, activated alumina, silica gel and molecular
sieves. Typical data for adsorbent material and their uses are given in Table-
12.
In adsorption, the adsorbate is recovered, with its chemical form un-changed. It is highly concentrated, and involves no potential of water pollution problem. The adsorbents were normally regenerated when the break through point is reached.
Table 12: Typical Data for Adsorbent Material and their Use
Specific
Bulk Density
area (m2/g)
Removal of odours and Dehydration of gases purification of gases Selective adsorption of NH3, H2S, C2H2 and SO2 AN APPROACH FOR DEVELOPMENT OF EMISSION STANDARDS FOR
PESTICIDE INDUSTRY
The National Environment Policy (NEP), 2006, with respect to emission standards i.e. permissible discharges of specified waste by different class of activities relates to risk reduction of health, sensitive and valuable ecosystem and manmade asset. The NEP further stated that standard for each class of activities need to be set on the basis of general availability of required technology, the feasibility of achieving the applicable environmental quality standards at the location (specific or category) concerned with the proposed emissions standards, and the likely unit costs of meeting the proposed standard. It is also important that the standard is specified in terms of quantities of pollutants that may be emitted, and not only by concentration levels, since the latter can often be easily met through dilution, with no actual improvement in ambient quality. National Environmental Policy also recommends to eschew the prescribed abatement technology. Keeping in view of above the approach for development of emission standard for Pesticide industries is given below: General availability of required technology and techno-economic feasibility Risk reduction related to health, ecosystem and manmade asset Ensure to achieve the ambient air quality standard (location specific) Best Practicable Approach (general availability to required technology and
techno-economic feasibility)
The emission standards for point source are often based on the best practicable means of control at source. The standard developed based on the best practicable means should in particular be uniform for the whole of the country for specific group of industries, in this case pesticide. An advantage of the technology –based approach is that within a specific group of industries the extent of pollution control measures are alike. In addition, these standards serve to preserve the environment quality in non-polluted areas without modification. The disadvantage of this approach is that these standards may become unnecessary burden on the industry where the recipient environment does not demand such control measures. This is because these standards do no related to the actual environmental of the specific site.
The methodology suggested for evolving stand on best practicable means is
explained in Flow Chart (Fig. 26). The acceptability of development of standard
on the basis of Best Practicable Technology is very much linked to the techno-
economic acceptability of the suggested stage of treatment to the pollutant which
is possible by linking the annual cost of pollution control measures (capital and
capitalised operation, maintenance and repair cost converted into annual cost or
annual burden) to the annual turnover of the industry. The stage of treatment
whose annual burden remains within the critical percentage of annual turnover is generally accepted as minimal stage of treatment and the concomitant emission standards is evolving standard of Best Practicable technology. There may be medium hard industry for whom the annual burden of the minimal stage of treatment should remain above the critical percentage of annual turnover but below the super critical percentage. The industry for whom the annual burden of the minimal state of treatment remains above supercritical percentage of annual turnover are obviously hard industry. 3% is generally considered, as critical and 5% is super critical.
- Total number of pollution control stage; annual burden of each stages of treatment is required to be evaluated - Stage of pollution control under consideration J = 1, it indicates the best stage of treatment which obviously uses the best available technology of treatment - Critical percentage of annual turnover of the industry to be ascertained by the industry committee - Super critical percentage of annual turnover of the industry to be ascertained by the industry committee - Quality of treated emission corresponding to any stage of treatment - Annual burden of any stage of treatment - Annual turnover of the industry - Location details of discharge of emissions; in the ambient AQL - Air quality criteria for the location INPUT N, J, C, EQs, ABs, AT PRINT AS EMISSION PRINT AS LOCATION SPECIFIC EQ Fig. 26 Flow Chart depicting Methodology for Best Practicable Means
On the basis of questionnaire survey and in-depth studies carried out, industry-
wise comparison of present available control technologies with respect to
identified priority pollutants are given in Table 13.
Table 13: Comparison of Control System for Identified Pollutants
Product (or)
Source of Pollution
after control
Incinerator (Liquid) Incinerator (Solid) Water Scrubber + Mist Eliminator + Demister (German Technology) Product (or)
Source of Pollution
after control
Mercaptan Scrubber Wet Scrubber with Charcol bed Scrubber Wet Scrubber with Wet Scrubber with Wet Scrubber with No Control System Liquification + Filling System or Incineration Liquification +Filling System or Incineration Scrubber + Caustic Scrubber + Ring Jet Two Stage Primary & Secondary Scrubber Product (or)
Source of Pollution
after control
No Control System Fenvelerate (PCT Scrubber & Bromine Bromine Rec. Unit Incineration after No Control System Totally closed & Controlled System Product (or)
Source of Pollution
after control
Water Jet Scrubber Water spray tower Incinerator (Liquid / Liquid & Vapour / Two stage tail gas absorption System along with water scrubber for vent Phenoxy Herbicide system & Caustic system & Caustic Product (or)
Source of Pollution
after control
Absorption tower & Data not available (Recovery as H3PO4) Hydrocarbon Waste Multi Cyclone Blower Isoproturon / Diuron Product (or)
Source of Pollution
after control
Plain Water Scrubber Scrubber + Activated No Control System No Control System Note: N.A. = Not Available.
In the light of above, general availability of technology in India for control of air
pollution in pesticides industries, are given in Table 14.
Table 14: Comparison of Best Practicable Technology for pollutants
Recovery
Expected
Achievable
average Conc.
-Caustic Scrubber -Caustic Scrubber -Liquification & -Incineration after Recovery
Expected
Achievable
average Conc.
-Scrubber with NaOCl -Scrubber with NaOH -Charcoal Scrubber -Caustic Scrubber (Ring jet scrubber) + Mist Eliminator + Demister -Two Stage Water Scrubber-Recovery System With respect to various control systems to various pollutants, the annual burden
to annual turn over ratio is summarised in Table 15. The table reveals that
AB/AT ratios are below critical percentage.
Table 15: AB/AT ratio for various pollution control systems
AB / AT ratio
and  Water/Caustic Scrubber  Liquification & filling system  Ventury Scrubber  Three stage caustic scrubber P2O5 and  Mist Eliminator  Water Scrubber + Mist Eliminator +  Two Stage Water Scrubber AB / AT ratio
and  Caustic scrubber  Incinerator with caustic scrubber  Solid waste incinerator HCl  Chemical waste Incinerator with quencher, water / caustic scrubber  Scrubber with NaOcl media  Charcoal scrubber Emission Standards with respect to Location Specificity
Dispersion modelling is a very strong tool/best alternative to estimate the Ground
Level Concentration (GLC) of the source emission pollutants in the ambient air.
If the modelling results of emission from the industry indicate violation or
likelihood of violation of ambient air quality standards (after accounting for
background levels), the industry sector specific emission standards be made to
ensure compliance with the ambient air quality standards. For this purpose, the
PC based Gaussian model has been employed to calculate the maximum
Ground Level Concentration (GLC) of priority pollutants. The modelling results
are shown in Table 16 and 17. For the calculation of GLC of priority pollutants,
worst-case source emission & weather conditions are taken into account:
Maximum volumetric flow rate as 5000 m3/hr (because it is varying from 1000 m3/hr to 5000 m3/hr in different pesticide units covered) Wind velocity at stack height is 1 m/s Plume rise = 0.5 m (Because the temperature and pressure of emission vents are observed as ambient temperature and atmospheric pressure respectively).
Ambient temperature = 25C.
Stability condition - F = Stable (throughout 24 hours is constant) Table 16: Control system + 20 m Stack height + Max. achievable
Table 17: Control system+ 30 m Stack height + Max. achievable
concentration
After going through the data obtained through questionnaire survey and during in-depth study, it was observed that the vent height of the process emission was varying from 10 m to 22 m, industry to industry and the maximum height of surrounding building was observed as 10 m.
Considering the achievability of best practicable standards with the general
availability of technology, the maximum ground level concentration with the help
of modelling, threshold limit value and also considering standards prescribed by
Central Pollution Control Board in other cases, the proposed standards for
pesticide industry are summarised in Table 18.
Table 18: Proposed Emission Standards for Pesticides Manufacturing
and Formulation Industry
The Central Pollution Control Board developed national emission standards for pesticides manufacturing industries, which were presented before eighteenth meeting of Peer and Core Committee held on April 20 & 21, 2004. Subsequently proposed standards were approved by the 132nd Board meeting held on January 04, 2005 and forwarded to MoEF for consideration and issuance of notification under the Environment (Protection) Act, 1986.
The Ministry of Environment and Forests; vide G.S.R. 46(E) dated 3rd February,
2006, notified the National Emission Standards for Pesticide Manufacturing and
Formulation Industry. The notified standard is given in Table 19.
Table 19: National Emission Standards for Pesticide Manufacturing and
Not to exceed
Particulate matte r with pesticide Guidelines for Fugitive Emission Control
Fugitive emissions over reactors, formulation areas, centrifuges, chemical loading, transfer areas etc., are yet to be collected through hoods and ducts by induced draft and controlled by scrubber / dust collector.
Usually scrubbers installed for channelised emissions are used for fugitive emissions to control also and some times dedicated scrubbers are provided. This practice may be permitted as long as tail gas concentrations are within the prescribed limit.
In addition, organic gaseous emissions (odorous and toxic) be routed to activated carbon beds (adsorption) or to thermal oxidiser, and for dust emissions cyclones / bag filters are to be provided.
Emphasis be given to solvent management / solvent loss prevention.
Enclosures to chemical storage area, collection of emissions from loading of raw materials, in particular, solvents through hoods and ducts by induced draft, and control by scrubber / dust collector to be ensured.
Vapour balancing, nitrogen blanketing, ISO tanks etc. to be provided; special care needs to be taken for control in respect of odorous chemicals. LD AR for Pesticide Indus tr y
Pesticides are manufactured in multi-stages in batch mode. In the manufacture of technical grade pesticides, various types of solvents are being utilized by the industries. Some of the solvents used are low boiling solvents and when such solvents are used, emission of Volatile Organic Compounds can be high. In addition to this, from the manufacture of intermediate products or technical grade pesticides, emission of raw materials or by-products like Cl2 and H2S is possible.
The pesticide industries are using pipelines, pumps, valves and other fittings in the transfer of solvents / raw materials from storage to the reactors and other ancillary facilities. To reduce fugitive emissions from the plants, proper Leak Detection And Repair (LDAR) Program is required at industry level.
The major solvents, which need special attention, are Toluene, Benzene, Xylene, Ethyl Acetate, Methanol and Cyclohexane. The raw materials or by-products needing special attention during transfer are Cl2 and H2S.
Comparing with refineries and petrochemical sector, the quantity of solvents used by pesticide industries is very less. Typically, the quantity handled in a batch process pesticide unit will be only 2,000 liters of solvent per batch. However, for better control of fugitive emissions, a proper LDAR Program is required.
The proposed LDAR program is as follows: Identification of sources: Valves, pipes, joints, pump seals, flanges etc Monitoring Program: VOC monitoring should be carried out by the industry regularly. For low boiling solvents and toxic / hazardous chemicals, monitoring frequency of minimum once in a quarter is suggested. The suggested solvents / chemicals subjected to such monitoring is Benzene, Toluene, Ethyl Mercaptan and H2S. The industries handling small quantities of Chlorine and Ethyl Mercaptan can use simpler monitoring methods. They can use lead acetate paper for checking the joints of pipes. For chlorine lines' leak detection, they can use dilute ammonia solution.
Preventive Maintenance: Focus should be for prevention of fugitive emissions for which preventive maintenance of pumps, valves, pipelines are required. Proper maintenance of mechanical seals of pumps and valves are required. A preventive maintenance schedule should be prepared by each industry and adhered to.
Repair Program: When monitoring results indicate VOC above permissible limits, repairing should be done immediately. The repairs should be conducted in such a way that there is no fugitive emission from the particular component.
To make the LDAR program more effective, for critical gases like H2S and Cl2, continuous monitors should be installed.
For Mercaptan lines, leak detection can be done with lead acetate solution, which is more reliable.
Minimal National Standards: Pesticides Manufacturing and Formulation Industry (COINDS/15/1985-86), Central Pollution Control Board, Delhi Revised MINAS Pesticides (COINDS/31/1988-89), Central Pollution Control Board, Delhi Wastewater Management in Pesticide Industry (COINDS/47/1993-94), Central Pollution Control Board, Delhi.
Document on pesticides Industry (INDO/5/84/85), Rajasthan Pollution Control Board, Jaipur.
Environment Audit – NOCIL Agrochemicals (PROBES/49/1992-93), Central Pollution Control Board, Delhi.
Rationale in Evolution of Standards for Industrial Effluents and Emissions (PROBES/67/1996-97), Central Pollution Control Board, Delhi.
Chemical Industry News, August 1995.
Pesticides Information, Journal, January-March 1998.
Chemical Weekly Annual, Journal, September,1998.
Manual for Pesticides User's: Pesticide Association of India, New Delhi Nov 1983 Audit and Reduction Manual for Industry Emissions and Wastes UNEP, 1991.
Air Pollution Control and Design for Industry Edited by Paul N. Cheremisinoff.
Environmental Engineers' Volume 2 Air Pollution Edited by Bela G. Liptak.
Air Pollution Control Engineering Edited by Noel de Nevers, University of Utah.
Pollution Control in Process Industries, Edited by S.P. Mahajan, IIT, Bombay.
An Introduction to Air Pollution, Edited by R. K. Trivedi & P. K. Goel, Department of Pollution Studies, Y.C. College of Science, Karad, Vidyanagar (Maharashtra) Industrial Pollution Control Handbook, Edited by Herbert F. Lund, President, Leadership Plus, Inc.
Encyclopaedia of Environmental Pollution and Control, Vol. 1, Edited by R.K. Trivedi Air Pollution Control Technology, An Engineering Analysis Point of View, Edited by Robert M. Bethea, P.E., Ph.D., Professor of Chemical Engineering, Texas Tech University, Lubbock, Texas.
Air Pollution Control Engineering, Basic Calculations for Particulate Collection, Second Edition, Edited by William Licht, Department of Chemical and Nuclear Engineering, University of Cincinnati, Cincinnati, Ohio.
Air Pollution, Third Edition, Volume IV, Engineering Control of Air Pollution Edited by Arthur C. Stern, Department of Environmental Sciences and Engineering, School of Public Health, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
Threshold Limit Values (TLV) for Chemical Substances in the Work Environment Adopted by ACGIH for 1984-85.
Filled Questionnaires received from various Pesticide Industries.

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