Issues with gas treatment from the water separation unit in the Luchi process
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In the Luchi coal-to-gas project, some units emit small amounts of toxic and harmful gases directly into the atmosphere, causing environmental pollution. The exhaust gas discharged from the single exhaust valve at the top of the atmospheric-pressure equipment in the gas water separation unit of the gas generation workshop is released directly into the atmosphere. It is understood that several companies in the same industry are currently adopting two treatment methods: 1. Sending the exhaust gases to a gasification torch for combustion treatment. 2. Add an alkaline scrubber tower; the exhaust gas is sent to this new scrubber tower where it is washed with 15% alkaline solution before being released. Are there any better solutions? I would appreciate some guidance from an expert.
It would be best if it could be sent to the torch for burning so as to meet the emission standards.
Since it is a atmospheric-pressure tank with a low gas volume, sending the gas directly to the flare seems problematic? I wonder what the effect of washing with alkali is?
The alkali cleaning effect is decent, but the alkali solution pipeline often gets clogged by crystallization, leading to unstable operation.
How to deal with the concentrated solution after washing is also a problem!
Some companies discharge the alkali-washed solution into the tar wastewater tank or into the gas and water system.
If there are heating furnaces, industrial furnaces, or boilers near the odor emission point, it is possible to install an additional corrosion-resistant plastic fan to draw in the odor containing trace amounts of H2S from that point, along with a small amount of air (about 300 Nm3/H). This air is then fed into the inlet silencer of the combustion fan in the nearby industrial furnace. The combustion fan pressurizes this mixture of odorized air and the surrounding air, sending it into the air passage of the burner at the top of the industrial furnace. The fuel gas (off-gas) and the odorized air burn together in the combustion chamber; the high temperature of 1000–1600 degrees Celsius in this chamber converts all of the H2S into SO2, which is then released through the chimney, thereby eliminating any odor pollution completely.
Due to the low pressure and the presence of air in this gas stream, directly increasing its pressure and then sending it to a flare for combustion poses process safety risks. A torch explosion could be caused by an excessive oxygen level.
If 15% caustic soda is used to absorb this odor, the waste alkaline solution becomes a **chemical due to the presence of sodium sulfide, increasing the difficulties in its management and disposal.
This problem exists not only in Lurgi gasifiers but also in pulverized coal gasification and water-coal slurry gasification. This problem is widespread; it seems easy, but in reality it is quite difficult to solve.
We are preparing to install a set of regenerative thermal oxidation units; I wonder if they are used in other industries as well.