What is the ratio of ammonia to sulfur in the ammonia-based desulfurization process for coke oven gas?
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In the coke oven gas desulfurization process, hydrogen sulfide in the gas is removed through a reaction between ammonia present in the gas and hydrogen sulfide. Is there a specific ratio required between ammonia and hydrogen sulfide? If the ammonia content in the gas is low, does it affect the desulfurization effect? I would appreciate your advice.
Based on the analysis of the ammonia-based desulfurization mechanism, the free ammonia content in the circulating fluid has a direct impact on the efficiency of coal gas desulfurization; abroad, ammonia-based desulfurization processes require a high ammonia level in the circulating fluid. The ammonia in the circulating liquid is replenished by absorbing ammonia from the gas; therefore, the ammonia content in the gas also directly affects the desulfurization efficiency of coke oven gas. According to foreign sources, the ammonia-to-sulfur ratio in the gas used for ammonia-based desulfurization should be greater than 0.7. The free ammonia content in normal circulating fluid is 4–5 g/l, with an ammonia-to-sulfur ratio of 0.7–1.0.
It depends on the specific coking process; after initial cooling in rammed coking, the ammonia content in the gas is low, with an ammonia-to-sulfur ratio generally below 1 (around 0.7). If strict desulfurization requirements are imposed, ammonia supplementation to the desulfurization solution must be considered.
If the ammonia content in the washing liquid is low, it is possible to increase the extraction of ammonia gas from higher positions in the ammonia vaporization tower in order to raise the ammonia content in the washing liquid.
Based on the analysis of the ammonia-based desulfurization mechanism, during the cyclic washing process with ammonia water, in addition to absorbing H2S, ammonia also reacts with HCN and CO2. Therefore, the mass ratio of NH3 to H2S in the gas cannot meet the requirements for H2S removal. The ammonia-to-sulfur ratio can be increased from the following aspects: improving the ammonia washing process ； Decompose the fixed ammonium salts in the residual ammonia solution ； An appropriate amount of concentrated ammonia water or ammonia gas is directly introduced into the upper section of the desulfurization tower ； Control the operation of the desorption tower to increase the ammonia-to-sulfur ratio of the regenerated lean liquid. Production data from a domestic plant show that the ammonia-sulfur mass ratio of the regenerated lean solution is greater than 9, with a desulfurization efficiency of over 90%.