Biological Desulfurization System for Biogas Plant

タイトルまたは説明

The major contaminant in biogas is H₂S which is both poisonous and corrosive, and causes significant damage to piping, equipment and instrumentation. Biological desulfurization (BDS) is a process in which sulfur compounds (H₂S, organic sulfur) are catalyzed by microorganisms or their enzymes, and the sulfur-containing organic compounds are converted into elementary sulfur and a trace amount of SO₄^*- ions. A new type of desulfurization bacteria was used in the biological desulfurization process, and the desulfurization efficiency was higher than *9.5% (higher than the traditional desulfurization process )

Biological desulphurization of biogas can be performed by using micro-organisms. Most of the sulphide oxidising micro-organisms belong to the family of Thiobacillus.

Working Principle 
Biological desulfurization process can be divided into three units: (1) scrubbing tower  (2) bio-regeneration reactor  (3) sulfur separator.

As shown in the following flowchart, the alkaline bio-washing liquid is ejected from the top of the scrubber and contacted with the sulfur compounds (mainly H₂S) gas entering from the bottom of the scrubber. During this process, the H₂S will be efficiently absorbed. Then the rich liquid containing sulfide flows into the bio-regeneration reactor from the bottom of the scrubber, and the alkaline biological detergent will be regenerated by the biological treatment of the desulfurization microorganism. The elemental sulfur will be seperated from sulfur separator in form of particle precipitation.

H₂S is absorbed by biological scrubbing liquid in washing tower, the main chemical reaction:
H₂S+OH^- = HS^-+H₂O; H₂S+CO₃^*- = HS^-+HCO^- 
Biological Regenation Reactor: 
HS^-*1/2O₂ = S+OH^-  (with catalysts of microorganisms)

Characteristics and Advantages 
1. No need of catalyst and oxidizing agent (except air).
2. No need to deal with chemical sludge.
3. It has little biological pollution, low energy consumption, high sulfur recovery, high efficiency and no odor.

Comparison of Various Desulfurization Process