Biogas purification, have you ever heard about this process? If not, don’t worry! In this article, we will explain how to remove CO₂ from biogas, a process called CO₂ scrubbing. In order to upgrade biogas to biomethane, which meets pipeline-quality standards and can serve as renewable natural gas, it’s really important to remove carbon dioxide during processing.
After that, the purified gas is ready to be used for residential heating and as vehicle fuel. So, you see, there are several reasons to remove CO₂ from biogas.
Generally, CO₂ is always present in biogas because, during anaerobic digestion (the breaking down of organic material without oxygen), bacteria produce a gas mixed with CO₂ and CH4 with trace amounts of H2S and water vapour at the saturation phase.
Common Methods to Minimize CO₂ from Biogas include:
These systems generally reduce the H2S and H2O content. Biogas treatment systems also need to include feed compression on the unpressurised raw biogas. Eventually, water vapour, hydrogen sulfide, siloxanes, ammonia, oxygen, nitrogen, etc., are some components that are present in biogas.
The most widely used technologies for biogas upgrading are water scrubbing. PSA, membrane and chemical scrubbing. Among these technologies, water scrubbing and PSA are generally regarded as the most suitable for small-scale applications due to their cost-effectiveness and low-maintenance requirements.
Removal of H2S from biogas is important as it can cause corrosion to the equipment. Also, it is dangerous for human and animal health. The CO₂ present in the biogas should also be eliminated with the help of a carbon dioxide scrubber because it reduces the calorific value of the gas.
These processes should be carried out to ensure the biogas produced qualifies as a natural gas substitute, which is environmentally friendly and safe for health.
The main ingredient to purify biogas using the water scrubber is obviously water. The water flows in a pressurised or unpressurised biogas purification column from the top to the bottom of the column, absorbing CO₂ and H₂S gases.
VPSA based upgradation systems can now offer a high methane purity exceeding 98% and a recovery rate above 99%, making it highly efficient. It processes raw biogas with a low energy consumption of less than 0.2 kW/m³ and includes built-in removal of H₂S, H₂O, and CO₂, with the possibility of partial O₂ and N₂ removal. The system offers a 50% turndown ratio, is pre-assembled for easy installation, and supports remote control and monitoring. Designed for low maintenance. Additionally, it supports CO₂ recovery, enhancing its versatility and environmental benefits.
So, you see, biogas purification is an important step in converting raw biogas into a clean, efficient, and renewable energy source. By using these scrubbing methods, one can eliminate CO₂ from the biogas.
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