COMPARATIVE ANALYSIS OF THE ENERGY CHARACTERISTICS OF AMINE AND WATER ABSORPTION PROCESSES EXTRACTING CO2 AND H2S FROM BIOGAS

Abstract

Currently in the world we remark wide development of biomethane from biogas production projects and it’s utilization as a universal fuel and engine fuel, it’s supply to the natural gas distribution network. The authors made a comparative assessment of energy costs of biomethane production from biogas, using common amine and waterabsorption processes of carbon dioxide and hydrogen sulfide extraction from biogas. For amine case, extraction of acid components process operating costs consist largely (up to 70–80 %) of the energy expenses for the regeneration of saturated amine, therefore, proposed solution is an effective absorbent — aqueous solution of methyldiethanolamine (MDEA, 40 %) (MDEA, 40 %) and monoethanolamine (IEA, 10 %), usage of which 2,3–2,5 times reduces heat load in the stripper reboiler in comparison with conventional solutions of monoethanolamine (MEA). Comparison of specific energy consumption for production biomethane using an amine and water purification technology of biogas from CO2 and H2S shows that the last has a 20–30 % lower power consumption than the amine. Our studies have shown that under comparable conditions the CO2 concentration at the outlet of the amine desorbing process is in the range of 98 % versus 80 % with water absorption, that indicates a loss of CH4 with gas desorption. Amine absorption gives an output of biomethane on average on 15 % more than water. Using this difference of produced biomethane the additional cost of the regeneration of the rich absorbent is compensated. Furthermore, water absorption requires a significant amount of water, it is connected with environmental concerns and the availability of water resources. In addition, if necessary, during the production of commercial carbon dioxide, the amine process has the advantage of CO2 concentration it is substantially higher at the outlet of the stripper. The comparative analysis of these schemes was conducted using GasCondOil and HYSYS software systems. The results and parameters of the biogas purification process from acid components can be used to calculate the carbon dioxide recovery process and to obtain biomethane — natural gas analogue. Bibl. 17, Fig. 9, Tab. 4.