NAME :- ARUP RAY CLASS :- B.CHE (IV) ROLL :- 001110301020 SEC :- A1 Seminar project on The wet sulphuric acid (WSA) PROCESS and its technology NAME :- ARUP RAY CLASS :- B.CHE (IV) ROLL :- 001110301020 SEC :- A1 REF :-The Process Principles in sulphur recovery by the WSA by Jens Kristen Laursen, Haldor Topsoe A/S. Helge Rosenberg etc.

INTRODUCTION AND DEVELOPMENT The wet sulfuric acid process (WSA process) is one out of many gas desulfurization processes on the market today. Since its introduction in the 1980s, when it was patented by the Danish catalyst company Haldor Topsoe, it has been recognized as an efficient process for recovering sulfur from various process gases in the form of commercial quality sulfuric acid (H2SO4). PROCESS PRINCIPLE Contrary to conventional sulphuric acid processes, the WSA process treats the process gas with all of its water content. This means that no cooling/condensation prior to the SO2 conversion stage is required. Consequently, there will be no liquid waste effluent, no loss of acid, no use of cooling water for this part and no loss of heat.

SALIENT FEATURES OF WSA PROCESS : Compared to other sulphur treatment processes, the WSA process offers a wider range of features: More than 99% recovery of the total sulphur content, always in compliance with environmental legislation. Product is clean, concentrated sulphuric acid of commercial quality, also in turndown situations. Heat of reaction is recovered as superheated or saturated steam. Gases containing hydrocarbons and with even very high CO2 content are accepted. No consumption of chemicals (except for optional DeNOx). Very low consumption of cooling water. No consumption of process water. No liquid or solid waste effluents. Wide turndown range. Simple layout, simple operation, overall attractive economy. Easy to combine with SCR for NOx removal.

THE PROCESS : Combustion: In the first step, sulphur is burned to produce sulphur dioxide: S(s) + O2(g) → SO2(g) or, alternatively, hydrogen sulphide (H2S) gas is incinerated to SO2 gas: 2 H2S + 3 O2 → 2 H2O + 2 SO2 + 518 kJ/mole In case there is some methane in the acid gas (as in our case), it will be combusted according to following reaction : CH4 +2 O2 → CO2 + 2 H2O Oxidation: This is then oxidized to sulphur trioxide using oxygen with vanadium oxide as catalyst. 2 SO2 + O2  ↔ 2 SO3 + 99 kJ/mole (reaction is reversible) Hydration: The sulphur trioxide is hydrated into sulphuric acid H2SO4: SO3 (g) + H2O (g) → H2SO4 (g) + 101 kJ/mole Condensation: The last step is the condensation of the sulphuric acid to liquid 97–98% H2SO4: H2SO4 (g) → H2SO4 (l) + 69 kJ/mole The energy produced by these above mentioned reactions is used for steam production. Approximately 2-3 ton high pressure steam / ton acid produced.

Topsoe WSA plant schematic diagram The WSA process flowchart SO2 Converter Topsoe WSA plant schematic diagram

EQUIPMENTS SO2 converter : The WSA condenser : Tail gas treatment unit : Waste heat boiler : Plate type heat exchanger : Catalysts : The SO2 conversion catalysts applied in the WSA process are the Topsøe VK series catalysts. The catalyst is based on vanadium pent oxide and sodium/potassium pyrosulphates on a diatomaceous earth silica carrier material.

The cleaned process gas leaves the WSA condenser at approximately 100 ˚C and can be sent directly to stack. The vertical glass tubes, the brick-lined bottom section and the coated tube-plates of the condenser are designed for long service life and avoidance of corrosion. Proprietary glass tube technology developed by Topsoe is used in WSA for condensation of sulphuric acid vapors.

APPLICATION : The wet catalysis process is especially suited for processing one or more sulfur containing streams such as: Processing of acid gases from amine regeneration units in hydrodesulphurization (HDS). Treatment of tail gases from Claus units. Regeneration of spent sulfuric acid from alkylation. Treatment of stack gases from utility boilers fired by heavy residues and petroleum coke. Treatment of H2S from coal gas. Industrial application : Refineries – Amine off-gas, SWS off-gas, Claus tail gas Coal Gasification – Rectisol, Selexol acid gas treatment Metallurgical and mineral industry – Smelter off-gas Power Plant – Boiler flue gas Coking, Viscose, Petrochemical, etc.

Benefits of using WSA process The WSA process is environmentally sustainable and highly energy efficient: No generation of waste materials. Efficient heat recovery ensures the best possible energy. Economy and maximum export of superheated steam at desired pressure. Very low consumption of cooling water. No consumption of chemicals.