Biogas is an eco-friendly energy source that is becoming in- creasingly important in today‘s energy supply. It can be used to generate power or heat or as a fuel, and provides a high energy yield per square meter of land. But an extensive up- grading and purification process is required before biogas is fed into the natural gas grid. New and highly selective poly- mer membranes from Evonik convert raw biogas simply and efficiently into highly pure biomethane. This increases yield and conserves valuable resources. Evonik Product Story Evonik Industries AG Rellinghauser Straße 1–11 45128 Essen Germany Contact Corporate Press Alexandra Boy phone +49 201 177-3167 fax +49 201 177-3030 [email protected]Trade Press Thomas Lange phone +49 2365 49-9227 fax +49 2365 49-809227 [email protected]Biogas from spaghetti? Membranes from Evonik upgrade biogas, generated from renewable raw materials, simply and efficiently.
Transcript
Biogas is an eco-friendly energy source that is becoming in-creasingly important in today‘s energy supply. It can be used to generate power or heat or as a fuel, and provides a high energy yield per square meter of land. But an extensive up-grading and purification process is required before biogas is fed into the natural gas grid. New and highly selective poly-mer membranes from Evonik convert raw biogas simply and efficiently into highly pure biomethane. This increases yield and conserves valuable resources.
Evonik Product Story
Evonik Industries AG Rellinghauser Straße 1–1145128 EssenGermanyContactCorporate Press Alexandra Boy phone +49 201 177-3167 fax +49 201 177-3030 [email protected] Press Thomas Langephone +49 2365 49-9227 fax +49 2365 49-809227 [email protected]
Biogas from spaghetti?Membranes from Evonik upgrade biogas, generated from renewable raw materials, simply and efficiently.
Green is in, with bicycles preferred to cars, organic produce to fast food, and energy class A+++ to A: In our modern society, decisions are increas- ingly being influenced by ecological considerations. Industry and business are also reacting to the trend towards sustainability and offering more and more “eco” products. And green energy is following the same track. Ac-cording to the Renewables Global Status Report (GSR) 2011, renewable energies today account for about 16 percent of global energy consump-tion; by the year 2050, this figure could rise to more than 50 percent, as predicted in a scenario of the World Climate Council in its Special Report on Renewable Energy Sources and Climate Change Mitigation (SRREN). With the major energy producers focusing mainly on wind, water and sun, biogas as an alternative energy source appears to have been somewhat overshadowed—quite unjustifiably, because it is a highly efficient energy source and an important component of decentralized supply structures.
Efficient biogas upgrading Biogas is produced by fermentation of biomass, an organic substance con-sisting of, for example, plants, liquid manure, or effluent sludge. But in ad-dition to the methane energy source, raw biogas also contains carbon dio-xide (CO2) and other trace gases. Because CO2 is not combustible, it lowers the calorific value of the gas and must therefore be separated out. The common separation methods such as pressurized water scrubbing, pressure swing adsorption, and amine scrubbing have considerable disad-vantages: They need comparatively large amounts of energy as well as auxiliary materials and chemicals. Wastes and wastewater are generated that must be treated and disposed of. Further, the biogas after upgrading is usually at low pressure. Before it is fed into a medium-pressure grid, it needs to be compressed to 15-20 bar by, for example, an additional com-pressor. Conventional upgrading plants are therefore usually cost effective only for raw biogas quantities significantly in excess of 500 standard cubic meters per hour (Nm³/h). This usually makes them unsuitable for decen-tralized energy supply with a large number of relatively small plants. Evonik Industries has developed a technology for cost- and energy-effici-ent separation of CO2. What appears at first sight to be a bunch of spa-ghetti strands or a paint brush is in fact a bundle of highly selective mem-branes made up of multiple cylindrical polymer hollow fibres. These are used in the new hollow fibre membrane modules of SEPURAN® Green.
Evonik Product Story
Highly selective membranes “SEPURAN® membranes are made from an internally developed high-per-formance polymer with very high temperature and pressure resistance. This plastic gives the membrane the property of distinguishing particularly effectively between methane and CO2, allowing the raw gas to be puri-fied to more than 97 percent methane,” says Dr. Goetz Baumgarten of the Fibres and Membranes growth line of Evonik‘s High Performance Po-lymers Business Line.
How does the membrane work? Gas molecules are of different sizes and have different solubilities in polymers. The biogas to be cleaned is introdu-ced under high pressure at one end of the membrane. “The CO2 mole-cules are smaller than the methane molecules and also more soluble in po-lymers. As a result, they pass through the micropores of the membranemuch faster and are separated from the methane,“ explains Baumgarten. CO2, water vapor, and traces of ammonia and hydrogen sulfide are drawn off at the low-pressure side (from the lateral opening in Figure 2), while the methane collects at the other end of the membrane, the high-pressure side. The methane-rich gas is directly drawn off at the high-pressure sideand needs no further compression for feeding into the grid.
Evonik’s membrane-based biogas upgrading offers particularly high plant availability, and has very low energy requirements and low maintenance
Evonik Product Story
It looks like a bunch of spaghetti strands or a paintbrush, but is in fact a bundle of highly selective polyimide hollow fibers in Evonik’s new SEPURAN membrane module.
costs. Moreover, the upgrading generates neither wastes nor emissions; nor are auxiliary materials such as water or sorbents required. All these pluses are directly reflected in the form of cost advantages. In addition, the membrane technology is applicable for small and large plants due to the high flexibility of the process. And the technology can easily be adap-ted for changing flow volumes and gas compositions.
The number of biogas plants based on SEPURAN® Green continues to grow: In 2012, EnviTec Biogas and Evonik opened an industrial-scale pilot plant with SEPURAN® modules at the Sachsendorf site in Brandenburg. This was followed a year later by the start-up of another 350 standard cu-bic meter gas upgrading plant in Köckte, in the state of Saxony-Anhalt. Early 2013 saw the start-up of a new SEPURAN® Green based biogas plant of Eisenmann AG in Pratteln, Switzerland; with an upgrading capa-city of 210 standard cubic meters, the plant processes about 15,000 me-tric tons of biowaste each year. “We’ve started marketing our high-perfor-mance membranes all over the world. In addition, we’re also developing the SEPURAN® product family further for new applications such as sepa-rating hydrogen and obtaining nitrogen from compressed air,” says Baum-garten, summarizing the future of the membranes.
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Biogas is produced by microbial fermenta-tion of sustainable raw materials like corn, or from effluent sludge or liquid manure. Following separation of various minor com-ponents like water vapor, hydrogen sulfide, and particularly CO2, the biogas can then be used in the gas grid, in combined heat and power plants, and at filling stations.
