With the unpopular policy of energy saving and emission reduction from time to time, many enterprises intend to use biogas from sewage stations to replace natural gas partially and enter boilers to extinguish or generate electricity. So, the hydrogen sulfide removal process (desulfurization) before the application of biogas has become a difficult choice for factories and stationmasters. At present, compared with the commonly used processes are dry desulfurization, wet desulfurization and biological desulfurization, this paper will give you a simple explanation and comparison of the three processes.
I. Common desulfurization processes
1. Dry Desulfurization
Biogas flows from one end of the desulfurization tower to the other end after being purified by a packed layer (mainly composed of activated carbon and iron oxide). Hydrogen sulfide reacts with iron oxide in the filler layer to form iron sulfide, and the regeneration can be stopped after the reaction of iron oxide is completed.
Fe2O3 · H2O+ 3H2S = Fe2S3 + 4 H2O
Fe2O3.H_2O+3H_2S = Fe2S_3+4H_2O
Fe2S3 + 3/2 O2+ 3 H2O = Fe2O3 ·H2O + 2 H2O+ 3 S
Fe2S3+3/2 O 2+3 H 2 = Fe2O3.H 2+2 H 2+3 S
2. Wet Desulfurization
Wet desulphurization is to send methane into the washing tower, wash it through alkaline solution, wash it out, wash the liquid into the rich liquid tank and regeneration tank, and then use the chemical method to catalyze and oxidize. Finally, the sulphide is converted into elemental sulfur (sulfur foam), and the absorption liquid can be recycled and recycled.
The process flow chart is as follows:
3. Biological Desulfurization
Biological desulfurization is also a kind of wet desulfurization. Compared with the catalytic oxidation process of wet desulfurization mentioned above, the biggest difference is that Thiobacillus is used instead of chemical catalyst to oxidize sulfide directly to sulfur.
H2S + OH-= HS- + H2O
HS- + 1/2O2= So + OH-
1) Dry desulfurization is mostly used in the condition of low load of hydrogen sulfide disposal or high requirement for desulfurization effect. At this time, dry desulfurization is mostly used for further desulfurization after wet desulfurization or biological desulfurization.
2) In formulating desulfurization effect, it is advocated that a reasonable removal effect be formulated according to the limitation of hydrogen sulfide concentration by follow-up equipment (boiler or generator) and the ratio of biogas consumption to natural gas consumption. Usually we advocate that the final hydrogen sulfide content be controlled at 25-100 ppm.
Above all, we have introduced three most commonly used desulfurization processes, each of which has its own advantages and disadvantages. In practical work, please select the appropriate technology according to the practical situation and use it sensitively. If you have any questions, welcome to contact us. Our website is http://www.dh-gwsg.com
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