DMT Environmental Technology has developed a unique process and concept, the DMT Carborex® PWS process for biogas upgrading. This allows us to offer a flexible, high quality gas upgrading plant, which can be delivered as prefabricated modules with final assembly on site. This approach means shorter delivery times and the possibility for a quick start-up of the process.
The process consists out of a scrubber process which means absorption of carbon dioxide and hydrogen sulphide in circulating water. The upgrading system utilizes reused water in a recirculation process. Depending on size and requirements the plants can be built as containerized units or assembled in industrial buildings. Electrical equipment is located in separate compartments, equipment is also located in separate compartments. The entire process is controlled by a PLC system where it is possible to communicate with the PLC system from a monitor computer system.
Movie 1: The DMT Carborex® PWS Biogas upgrading plant movie
Pressurized water scrubbing
Water scrubbing is generally used to remove carbon dioxide but also hydrogen sulphide from biogas since these gases are more soluble in water than methane. The absorption process is purely physical. Usually the biogas is pressurised and fed to the bottom of a packed column where water is fed on the top and so the absorption process is operated counter currently. Water scrubbing can be used for selective removal of both carbon dioxide and hydrogensulphide since this is more soluble in water than carbon dioxide. The water which exits the column with absorbed carbon dioxide and hydrogen sulphide can be regenerated and circulated back into the absorption column.
The most cost effective method is not to circulate the water if cheap water can be used, for example, outlet water from a sewage treatment plant. This process can be economically applied in the purification of gases with daily sulphur production rates up to more than 10 tons. Examples of gas streams that can be treated with this process are:
- Landfill gas
- Biomass digester gases
- Natural gas
- Industrial waste gases
- Flare gases
The selective absorption process has several key advantages compared to alternative processes available on the market :
- Low energy consumption
- No consumption of chemicals
- Selective towards H2S and CO2
- Simple process scheme and process control
- Flexible towards feed gas fluctuations
- Odour free cleaned gas (H2S < 1 ppmv is possible)
- Basically no chemical waste
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