dmt making pressurized water scrubbing
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Making pressurized water scrubbing the ultimate biogas upgrading technology with the DMT Carborex PWS system.Robert Lems*, Erwin Dirkse** *R&D manager, DMT Environmental Technology, Yndustrywei 3, 8501SN, Joure, The Netherlands (E-mail: [email protected]). ** Managing Director, DMT Environmental Technology. ([email protected]) Abstract Biogas is one of the most promising energy sources for the future. Biogas is a waste product from e.g. landfill sites or digesters that can be applied as a green and renewable energy source with no global emissions on CO2 and hardly no local emissions on other pollutants. Currently most biogas is used at a CHP at which a large part of the energy is converted into heat which can not or only partly be used. This could result in an energy loss up to 60%. But biogas can also be upgraded to natural gas quality. As upgraded biogas, the gas can be used as vehicle fuel, injected into the gas grid or transported to more efficient energy production sites by which the total energy recovery can be close to 100%. Most important for biogas upgrading to natural gas quality is the removal of CO2 and H2S. A second important issue is the energy efficiency and methane losses. In this paper the advantages of pressurized water scrubbing compared to other available technologies are stressed out. In more detail innovations of the DMT Carborex PWS technology are explained. The possibilities for recovery of liquefied CO2 and the integration of heat-pump technology makes it the ultimate process for biogas upgrading. The result is an energy neutral plant without methane losses and even a reduction on global CO2 emissions (instead of being neutral). DMT will demonstrate the pressurized water scrubbing system in relation with the other upgrading processes by field experiences. Keywords Biogas, Biological desulphurization, CO2 recovery, Heat pump, Methane recovery, Natural gas, Pressurized water scrubbing, Upgrading system. Abbreviations upgrading: PSA: Pressure swing absorption, CA: Catalytic absorption, MS: Membrane separation, CL: Cryogenic liquefaction, PWS: Pressurized water scrubbing. Introduction Biogas is produced by fermentation of organic material in e.g. digesters but also at landfill sites. The gas contains high amount of methane which can be used as a green energy source with no global emissions on CO2 and hardly no 1 local emissions on other pollutants (see figure 1 for an example of vehicle fuel comparison). This makes biogas the most sustainable source of energy in the future comparable to solar-, wind- and water power.
Figure 1: Comparison of different vehicle fuels on global and local pollution emissions.
Currently most biogas is used in CHP or gas engines at which a large part of the energy is converted into heat from which usually only a small part can be used on site. This can result in energy losses up to 60%. But biogas can also be upgraded to natural gas quality or better. As upgraded green gas, the biogas can 2 be used as vehicle fuel , injected into the gas grid and/ or transported to more efficient energy production sites where the total energy recovery can be close to 100%.
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For upgrading biogas to natural gas quality, the main function of the plant is the removal of CO2 and H2S (see table 1) to increase the energy content and reduce risk of corrosion. A second important aspect for the upgrading plant is the energy and methane efficiency to reach the desired final methane concentration. Most upgrading processes like pressurized water scrubbing have an energy efficiency between 90-96% and a methane slip of 0.5-2%. However, the DMT Carborex PWS system combines the PWS upgrading technology with the recovery of liquefied CO2 and the integration of highly advanced heat-pump technology. The result is an energy neutral plant with no methane loss and even a reduction on global CO2 emissions (instead of being neutral). Table 1: Raw biogas versus biogas at natural gas quality (The Netherlands/ UK/ German) and biogas at 3, 4 maximum quality for vehicle fuel use. Component Unit Biogas Natural gas Natural gas Vehicle fuel (Dutch) (German/ UK) CH4 v/v % 45-70 90-95 >95 >97 CO2 v/v % 30-45