Views: 3 Author: Site Editor Publish Time: 2023-08-30 Origin: Site
With the rapid development of the economy, the global energy demand is increasing. Excessive reliance on traditional fossil fuels in the energy structure can lead to a significant energy crisis. Biogas, as an emerging green energy source, is gaining attention and becoming prominent.
This article will delve into the role, advantages, and future development prospects of activated carbon in biogas desulfurization.
Biogas is a mixed gas, primarily composed of methane (CH4), carbon dioxide (CO2), hydrogen sulfide (H2S), vola
tile organic compounds (VOCs), and nitrogen (N).
Hydrogen sulfide (H2S) in biogas can cause strong corrosion to metal equipment and pipes during usage, leading to the emission of harmful gases like sulfur dioxide, polluting the environment. Therefore, it is essential to remove hydrogen sulfide before comprehensive utilization.
Here are some common biogas desulfurization technologies.
Biogas enters the reaction tower from the bottom and contacts the absorbent liquid in countercurrent, and the purified biogas is discharged from the top of the tower. This desulfurization method, known as the alkaline liquid absorption method, utilizes oxygen to regenerate the absorbent.
In the PDS method, the reaction between sodium hydrosulfide, sodium bicarbonate, and elemental sulfur not only solves the problem of harmful substances generated by the reaction of sodium hydrosulfide with oxygen but also produces reaction products with higher sulfur capacity and larger sulfur particles, facilitating flotation and separation.
High polymeric compounds (HPC) can remove H2S from biogas and recycle the generated elemental sulfur. The HPAS method, with its excellent oxidation-reduction capability, converts H2S into elemental sulfur, consisting of desulfurization and oxidation-regeneration processes.
Iron oxide, also known as sponge iron, is an ancient desulfurizing agent. The high oxidation-reduction potential of Fe3+ oxidizes H2S to elemental sulfur, which can be recycled. The generated elemental sulfur has a catalytic effect on the entire absorption process.
The activated carbon method consists of desulfurization and activated carbon regeneration processes. During desulfurization, activated carbon catalyzes hydrogen sulfide, reacts with the stored oxygen to produce elemental sulfur, and adsorbs it. When the activated carbon is saturated, it can be regenerated using ammonium sulfide solution, and the generated polysulfide ammonium undergoes steam heating to decompose into ammonium sulfide and elemental sulfur, continuing the cycle.
Membrane separation is a concentration-driven process. Due to the higher relative permeability of impurities such as CO2 and H2S compared to CH4, these impurities permeate to the low-pressure side to form permeate gas, while the CH4 gas in biogas becomes residual gas flowing out from the other side.
While there are various biogas desulfurization technologies, many of them come with high costs and potential secondary pollution issues. Activated carbon, however, is a low-energy-consumption and low-pollution desulfurization technology that is gaining increasing attention.
Activated carbon, with its high surface area, adsorption rate, and capacity, achieves a desulfurization efficiency of up to 99%.
Its advantages include a fast reaction rate with hydrogen sulfide, short contact time, large processing capacity, and low desulfurization cost.