Typical process flow of sulfur recovery and exhaust gas treatment units

The typical process flow for sulfur recovery and flue gas treatment devices is as follows: In the first step, the acidic gas rich in hydrogen sulfide, which is emitted from various desulfurization units after treatment with amine solution and acid water stripping, is mixed in proportion with air and then fed into a thermal reaction furnace where an oxidation reaction takes place to produce sulfur gas. Step 2: The process gas coming out of the thermal reaction furnace (containing sulfur gases, unoxidized hydrogen sulfide, sulfur dioxide, nitrogen, etc.) is cooled to around 315 degrees in a waste heat boiler, where heat exchange generates medium-pressure steam. Step 3: The gas, after being cooled in the waste heat boiler, enters the primary condenser where it is further cooled to around 160 degrees. All of the sulfur gases present in the gas get condensed and separated from the gas itself, then flow into the sulfur tank through a sulfur seal. Step 4: The process gas after the primary condenser is reheated to 260 degrees to 290 degrees, then enters the primary catalytic reactor where it undergoes further reactions to produce sulfur gas. After heat exchange, the process gas enters the secondary condenser where its temperature is reduced to around 160 degrees. All of the sulfur gases present in the process gas condense and separate from the gas, then flow into the sulfur tank via a sulfur seal. Step 5: The process gas after the secondary condenser exchanges heat with the process gas at the outlet of the primary catalytic reactor, so as to reach the inlet temperature of 220–250 degrees in the secondary catalytic reactor. Within this reactor, the process gas is further converted into sulfur gas. After heat exchange, the process gas enters a three-stage condenser where its temperature is reduced to around 160 degrees. All of the sulfur gases present in the process gas condense and separate from the gas, then flow into a sulfur tank through a sulfur seal. After secondary conversion, the sulfur recovery rate can reach around 95%. Step 6: To further increase the sulfur conversion rate and meet stricter environmental requirements, it is necessary to carry out hydrogenation reduction treatment on the exhaust gas from the Claus sulfur recovery unit, that is, to send it to an exhaust gas treatment unit. The exhaust gas from the sulfur recovery unit is heated (there are three heating methods; the first one involves using the waste heat from the flue gas of the incinerator) ； The second method involves using an online heating furnace to generate high-temperature flue gas for direct mixing and heating; the third method involves heat exchange with the exhaust gas from the hydrogenation reactor, along with supplementary electric heating. The resulting mixture is then mixed with hydrogen and fed into the hydrogenation reactor, where, under the action of a catalyst, elemental sulfur and sulfur dioxide are reduced to hydrogen sulfide, while thiooxycarbene and carbon disulfide are hydrolyzed into hydrogen sulfide. Step 7: The process gas exiting the hydrogenation reactor is cooled through heat exchange; after being quenched with water, it enters the absorption tower where ultra-poor amine solution is used to absorb the hydrogen sulfide contained in it. The gas is then returned to the acidic gas network via stripping and regeneration. Step 8: The clean gas exiting the top of the absorption tower contains trace amounts of hydrogen sulfide (usually below 200 ppmv); this hydrogen sulfide is converted into sulfur dioxide through high-temperature treatment in a thermal incinerator, after which it is released into the atmosphere.

May I ask, since the heat transfer coefficient for gas-to-gas heat exchange is relatively low, would extensive use of gas-to-gas heat exchange in Claus units result in a large required heat transfer area, thereby making the corresponding heat exchange equipment larger?