Ammonia and benzene, toluene, and xylene (BTX) are typically encountered in refineries, gasification facilities, gas processing plants, and heavy oil upgraders together with H2S in the sour water stripper off gas. This gas is often processed in the Claus unit prior to venting to the atmosphere. Ammonia must be completely destroyed in the reaction furnace to prevent plugging and corrosion of downstream equipment. Fluor's proprietary configurations Acid Gas Split-Flow, Feed Preheat, Fuel Gas Supplement and Oxygen Enrichment effectively increase the reaction furnace flame temperature for complete contaminants destruction.
The proprietary Acid Gas Split Flow configuration utilizes a two-chamber reaction furnace that is a single vessel divided by a refractory choke ring. The amine acid gas, which has no ammonia, is split between the front and the rear chambers of the furnace. All the ammonia-bearing gas is sent to the front zone. By the same mechanism as mentioned above, bypassing part of the acid gas results in higher temperatures in the front zone where ammonia destruction takes place. In this case, the bypassed amine acid gas rejoins the combustion mixture in the rear zone of the reaction furnace instead of downstream of the waste heat boiler, to maximize sulfur recovery in the furnace section.
The Split Flow configuration is not recommended for processing acid gases containing aromatics and heavy hydrocarbons. For those cases, Feed Preheat, Fuel Gas supplement, and/or Oxygen Enrichment are employed.
The various processes are not mutually exclusive and can be applied concurrently to achieve the required contaminant destruction.