LECTURE 15-19 IIA SULFUR AND SULFURIC ACID.pptx

SULFUR AND SULFURIC ACID

1. LECTURE 4-7 INORGANIC CHEMICAL INDUSTRIES IIA-SULFUR AND SULFURIC ACID 16-08-2023 INORGANIC CHEMICAL INDUSTRIES 1

2. SULFUR Raw material for H2SO4 production 4 % consumption of acid as compared to USA Pertinent Properties of Sulfur Chemical formula-S Atomic wt.- 32.07 MP-112.8oC BP-444.6oC 2. Consumption Pattern: SO2, SO3, H2SO4, H2SO4+SO3 16-08-2023 INORGANIC CHEMICAL INDUSTRIES 2

3. RAW MATERIALS SOURCES ELEMENTAL SULFUR, PYRITES (SULFIDES OF IRON), H2S, WASTE GASES, SMELTING OPERATIONS SUCH AS COPPER, IRON, ZINC AND LEAD INDIA- AMJHORE IN ROHTAS DISTRICT OF BIHAR, SALADIPURA IN SIKAR DISTRICT OF RAJASTHAN SULFUR DEPOSIT IN PUGA VALLEY OF KASHMIR 16-08-2023 INORGANIC CHEMICAL INDUSTRIES 3

4. OTHER SOURCES OF S PETROLEUM REFINERIES ZINC & COPPER SMELTER AS BY PRODUCT Elemental sulfur Mining (Frasch Process) S deposits in salt domes Large supply of hot water Quantitative requirement Basis: 1MT of S water (160oC) 6 T Dome operating Capacity: 500-800 T/d of S 16-08-2023 INORGANIC CHEMICAL INDUSTRIES 4

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6. Major Engg . Problems HT in melting and shipping operations Finding suitable sources of treated water Corrosion 16-08-2023 INORGANIC CHEMICAL INDUSTRIES 6

7. OXIDATION – REDUCTION OF H2S Raw Materials: H2S from natural (sour) gas and petroleum refinery streams. Recovered by scrubbing with ethanolamines and high temperature stripping. Quantitative requirements: Basis: 1MT of S and 100% yield H2S 1.2 tons; Air 1700Nm3 Plant capacities: 20-600 t/d 16-08-2023 INORGANIC CHEMICAL INDUSTRIES 7

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9. Major Engg . Problems 2-stage reactor design for exothermic SO2 oxidation of H2S. 70-80% conversion in 1 st stage at 300-400oC range followed by 250-300oC operation in 2 nd reactor to obtain favourable equilibrium. Heat exchange for molten S handling Corrosion Final clean-up of stack gases 16-08-2023 INORGANIC CHEMICAL INDUSTRIES 9

10. ELEMENTAL SULFUR FROM PYRITES (FINNISH PROCESS) 16-08-2023 INORGANIC CHEMICAL INDUSTRIES 10

11. Quantitative requirements Basis: 1 ton of elemental S (99+% purity, 92% total S recovery) Pyrite ore (Amjhore) 4.4 tons Limestone 0.65 ton Fuel oil 0.76 ton Water 25 tons Electricity 1800KWH Co-Products: SO2 from FeS roasting=1.2 tons Fe2O3 from FeS roasting= 2.8 tons Electricity = 3200KWH total or 1400 KWH net Plant capacities: 250 t/d as elemental sulfur 16-08-2023 INORGANIC CHEMICAL INDUSTRIES 11

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13. Major Engg . Problems Pyrites ore beneficiation: Amjhore has 5-7% SiO2 and requires either flotation initially or extra limestone to flux out the silica. The latter is preferred to prevent the loss of 30% ore during beneficiation. Grinding: Particle size range of -200 mesh was an economic balance between HT rate from combustion gases + residence time. Substitution of coal for fuel: Pulverized coal directly in the smelter burners or working with secondary combustion gases after ash has been removed must be resolved 16-08-2023 INORGANIC CHEMICAL INDUSTRIES 13

14. Major Engg . Problems Gaseous reactions in the smelting furnace: Complete combustion of fuel without excess air is desirable to avoid unbalance of the H2S-SO2 ratio. Two-stage catalytic reactor design: Plant 1 st operated only with cold stage so that COS & CS2 remained unconverted to free sulfur. Heat recovery and generation of electric energy: Overall all process has excess heat energy 16-08-2023 INORGANIC CHEMICAL INDUSTRIES 14

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16. H2SO4 H 2 SO 4 is a colourless or slightly yellow viscous liquid with a pungent odour. It has a density of 1.84 g/mL, boiling point of 337°C, and melting point of 10°C. "Concentrated" sulfuric acid is 98% in water, and is the most stable form. 16-08-2023 INORGANIC CHEMICAL INDUSTRIES 16

17. METHODS OF PRODUCTION Classification of Processes Chamber process (1746), yield-80% Contact process, Yield-98% Both processes are based on SO2 Contact process Chemical reactions 16-08-2023 INORGANIC CHEMICAL INDUSTRIES 17

18. Raw materials SO2 sources Sulfur Pyrites CuS , ZnS , PbS , MoS2, Waste H2SO4, H2S Catalyst: V2O5, Pt. Characteristics of catalysts: 16-08-2023 INORGANIC CHEMICAL INDUSTRIES 18

19. Characteristics of catalysts: Porous carrier- having large surface area, controlled pore size, and resistance to process gases at high temperature: in pellet form if it is used in the fixed beds, powdered form for fluidized beds. Active catalytic agent- Secret preparations, e. g. V2O5 Promoter- alkali and/or metallic compounds added in trace amounts to enhance activity of catalytic agent 16-08-2023 INORGANIC CHEMICAL INDUSTRIES 19

20. Advantages of V2O5 Relatively immune to poisons Low initial investment and only 5% replacement / yr Requires only 10 kg of catalyst mass containing 7-8% V2O5 per daily ton of 100 % acid Disadvantages of V2O5 Must use dilute SO2 input (7-10%); as catalyst is less active and requires high O2/SO2 to give economic conversion. Larger converters and higher initial investment are necessary Quantitative requirements Basis: 1 ton of 100% H2SO4 SO2 0.67 ton air 1450-2200 Nm3 Plant capacities: 50-1000 tons/day of 100% acid 16-08-2023 INORGANIC CHEMICAL INDUSTRIES 20

21. 16-08-2023 INORGANIC CHEMICAL INDUSTRIES 21 Yield increased to 97% 30% of total catalyst and convert 80% SO2

22. Major Engg . Problems Design of multistage catalytic converter for highly exothermic reaction Optimization of space velocity in a catalyst chamber: pumping cost versus fixed charges of reactor Corrosion problems: Optimization studies shows that equilibrium yield can be increased by the square root of system pr at a given temperature Adaption of process to various types of gas feeds Yield can drop due to longitudinal mixing if the convective gas velocity through the bed is too low. Removal of heat of absorption of SO3 in acid. Pr. drop must be low so 8 cm stacked packing is often used. 16-08-2023 INORGANIC CHEMICAL INDUSTRIES 22