Adding gas from biomass to the gas grid - SGC

Plant examplesParameter Unit Process Plant 1 Plant 2 Plant 3Location/name Ellinge Bromma KristianstadCapacity range m 3 10 - 1000 70 55 175biogas/hInput· methane%45 - 75 58 - 60 61 - 6660· carbon dioxide%25 - 55 40 - 42 33 - 3840· nitrogen%< 10 0.4 - 1.60· hydrogen sulphideppm< 1000< 10 < 0.5no dataOutput· methane· carbon dioxide· air· dewpoint%%%°C> 98< 2< 120 - 3596 - 990.5 - 30.8-6096 - 972 - 31-5097 - 981.5 - 20 - 0.5< -20Process conditions· adsorption pressure bar6 - 12 7 - 11228 - 10· water flowm 3 /h 10 - 15 9 8 - 20 5 - 1520 - 25· adsorption temperature °C10 - 25 10 - 25 10-2510 - 25· pressure in flash tank bar2 - 5 no flash tank no data1.5 - 2Supplier Ellinge FEAB Malmberg WaterTable 14: Removal of carbon dioxide using water wash without regenerationRemoval of carbon dioxide using SelexolSelexol is a registered trade mark for a polyglycol ether. The chemical is dissolved in water and hasa very low vapour pressure. This means that the losses of chemicals are very low in the process.Selexol removes carbon dioxide, hydrogen sulphide and water simultaneously.The selectivity for hydrogen sulphide is very high compared to carbon dioxide and regenerationfrom H 2 S requires increased energy input.Carbon dioxide is absorbed in a circulating Selexol solution at elevated pressure. Cleaned biogas iscompressed and fed into the bottom of an absorption column. Selexol is fed from the top of thecolumn to achieve a gas-liquid counter flow. The column is equipped with random packing to give alarge surface for gas-liquid contact and internals for the collecting and redistribution of Selexol.Carbon dioxide is absorbed by the Selexol solution and the gas leaving the top of the column isstripped from most of the carbon dioxide content.Methane is partly soluble in pressurised Selexol solution and therefore some methane will beremoved with the liquid. To minimise the losses of methane, the Selexol solution is depressurised ina flash tank after leaving the absorption column. The released gas mixture is rich in methane and isrecirculated to the compressor inlet.9Depending on the absorption pressure, for every 100 m 3 /h processed biogaspage: 41