Adding gas from biomass to the gas grid - SGC

Parameter Unit Process Plant exampleLocation/nameLaholmCapacity range M 3 biogas/h 100 to > 10,000 250Input· methane%45 - 7569 - 72· carbon dioxide %25 - 5528 - 31· nitrogen%< 10 - 0.2· hydrogen sulphideppm< 10 10 0 - 15Output· methane· carbon dioxide· air· dewpoint· hydrogen sulphideProcess conditionsAbsorption pressureAbsorption temperaturePressure in flash tankDesorption pressureSelexol flowSupplier%%%°CppmBar°Cbarmbar (abs)m 3 /h> 98< 2< 1.5< -20095 - 982 - 50 - 0.5< -60010 - 127 - 920 - 3572 - 51.5 - 2atmospheric to 2009503 - 6 11 10 - 15Malmberg Water ABTable 15: Removal of carbon dioxide using Selexol4.3.5 Removal of carbon dioxide by chemical reactionThis process is based on the same principle as the absorption processes without chemical reaction,see § 4.3.4. The raw gas is led through a liquid, typically at elevated pressure and temperature, andthe undesired components (e.g. CO 2 , H 2 S) are absorbed in the liquid. However, instead of simplydissolving these components, the liquid reacts chemically with them and therefore drives them intosolution.Due to absorber costs and the disposal of contaminated absorber, the absorber is alwaysregenerated, i.e. single pass operation know, from water scrubbers are not applied. The process iscontinuous and the absorber is regenerated in a reversal chemical reaction in which the absorbedCO 2 is released.Table 15 illustrates the characteristics of a number of gas treatment processes with absorption inchemically reacting absorbers. The alkanolamines MEA, DEA and DGA are examples of absorbers.Several of the alkanolamines also absorb a significant amount of the water contained in the biogas.MEA, that is an organic base in an aqueous solution, is one of the most feasible chemicalabsorbers. MEA is often used in gas separation processes in e.g. CO 2 production from flue gases,cleaning of natural gases, and production of hydrogen and ammonia. It is a colourless, viscous,1011Excess H 2S (> 10 ppm) removed separately to reduce energy costsDepending on the absorption pressure, for every 100 m 3 /h processed biogaspage: 43