【Monthly Topic】Waste gas emission issues from water-coal slurry gasification
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The components of the hot water tower exhaust, deaerator vent gas, and the stripping tail gas from the shift unit in the black ash water treatment system for the water-coal slurry gasification process are essentially similar; the main components are CO2, H2S, NH3, H2O, along with small amounts of CO, H2, CH4, and N2. I would like to know what the advantages and disadvantages are of sulfur recovery from these gases compared to those from boilers How do various companies do it?
The exhaust gases emitted from these sections, when sent for desulfurization recovery or used in boilers, have little practical value; after all, the water vapor content in these gases is over 95%, while the amounts of non-condensable gases such as CO2, H2S, and NH3 are very low. I have the following views: First, it has little calorific value and cannot be used as a source of heat ； The second exhaust gas is primarily composed of water vapor. When this water vapor enters the sulfur recovery furnace or boiler, it does not contribute to providing heat; on the contrary, it takes away heat, resulting in a loss of some of the heat energy. From another perspective, this means an increase in energy consumption ； The third stream of exhaust gases enters the boiler, which provides some slight benefit for flue gas denitration, but the benefit is limited. In my opinion, it’s better to simply use an independent acidic gas flare to burn these gases at the flare tip. As the saying goes, even the smallest mosquito counts as flesh, but these exhaust gases aren’t even worth as much as mosquito flesh.
I agree with what was said on the second floor: most of this exhaust gas consists of water vapor, and its calorific value is not high. However, by using circulating water for heat exchange to cool the gas and remove the water, its calorific value can be increased; thereafter, it can be sent to sulfur recovery systems where its heat value can be utilized again. This is the process we use.
The problem is that continuous emission to a flare stack is also not allowed; it is only permissible in the event of an accident.