20000m3/Day Wet Chemical Biogas Desulphurization Plant

• Desulfurization Technology: Wet + Dry Chemical
• Biogas Flow Rate: 20000 Nm3/Day
• Transport Package: LCL or FCL
• Specification: Complete System
• Trademark: ALONG BIOGAS
• Origin: China
• Model NO.: ALONG BIOGAS -GasCle series
• HS Code: 8486909000
• Production Capacity: 100 Sets/Year

Product Description

Wet desulphurization technologies include physical absorption, chemical absorption and chemical oxidation. The need of reprocessing hydrogen sulfide of Physical and chemical absorption restrict their applications in actual projects. The widely used method is chemical oxidation, with alkaline solution as the absorbent and oxygen carrier as catalyst. The alkaline chemicals dissolved in water and goes into tower to contact with hydrogen sulfide to make oxidation reaction with elemental sulfur generated. The desulphurization efficiency of mature chemical oxidation method can reach above 99.5%.

For large projects, the desulphurization process is usually the combination of wet and dry types. Wet type is for the primary filtration while dry type for the fine desulphurization.

The wet desulphurization tower is composed of scrubbing tower, H2S sampling and monitoring system, alkaline solution deploying groove, softening water feed device, liquid level control system, supports and connection fittings. Automatic operation would be achieved through the monitoring of outlet hydrogen sulfide content and Ph value.

When system in operation, raw biogas gets through tower in the bottom-up flow, while the Na2CO3 solution(or NaOH solution) sprays into tower from the top down, by this means the complete reaction occurs between H2S and alkaline solution. The liquid is gathered in the bottom groove of tower, with automatic addition by metering pump by means of the monitoring of H2S concentration at outlet.

Main reaction mechanism if take Na2CO3 as alkaline chemicals
1,  Absorption:                    H2S + CO32- = HS- + HCO3-
2,  Oxidation Separation of Sulfur:      HS- + [Catalyst]·O = OH- + [Catalyst]·H
3,  Regeneration:                [Catalyst]·H + O2 = [Catalyst]·O
                            OH- + HCO3- = CO32- + H2O


Dry chemical desulphurization is a simple, efficient and low-cost solution for removing Hydrogen Sulfide in biogas, generally suitable for low-flow biogas with low Hydrogen Sulfide content. Main principle is that H2S is oxidized by O2 to sulfur or sulfur oxide, so it is also known as dry oxidation process.

The process is structured as a cylindrical container with chemical fillings inside, which are activated carbon or ferric oxide, etc. The raw biogas at low velocity goes through the filling layer, then hydrogen sulfide would be oxidized to sulfur or sulfur oxide, which remains in the filling layer. And the purified biogas flows out of tower at upper position.

We call this cylindrical container as tower, material is carbon steel or stainless steel, wall thickness is 4 ~ 10 mm available, diameter varies in the range of 440 ~ 5000 mm, and height of tower is 1.0 ~ 10 meters available. It's a kind of nonstandard equipment, actual dimension would be subject to gas flow and hydrogen sulfide content in the raw biogas.

Main equipment is the steel-structure tower, filled by desulphurizer agent, equipped with observation window, pressure gauge, thermometer and other components. There are usually two towers to be used alternately, one for operation while the other for regeneration. When biogas flows through tower down-up, below chemical reactions would occur:

Desulphurization agent (Ferric Oxide):
First-step: Fe2O3·H2O + 3 H2S = Fe2S3 + 4 H2O (Desulphurization)
Second-step: Fe2S3 + 3/2 O2 + 3 H2O = Fe2O3·H2O + 2 H2O + 3 S(Regeneration)

The biogas containing hydrogen sulfide reacts firstly with the high-loading desulphurizaer agent near the bottom entrance. The upper filling layer is low-loading agent. By means of well-designed biogas airspeed and line speed to reach fine desulphurization effect.

It's better to install a primary filter before the process of desulphruzation, to remove physical impurities and make biogas with a certain humidity.

When the desulphurizer agent in the running tower is observed discolored or the pressure loss is too big, the other tower should be used alternately. Natural ventilation for the current tower after biogas emptying for regeneration of desulphurizer agent. When regeneration result is not good enough for reuse, a replacement for the old agent would be processed through the bottom outlet and the same amount of fresh agent is filled into tower.