Abstract
Natural gas is becoming increasingly important as a primary energy source. A suitable replacement for fossil natural gas is bio-SNG, produced by biomass gasification, followed by methanation. A major challenge is efficient gas cleaning processes for removal of sulfur compounds and other impurities. The present study focuses on development of a gas cleaning step for a product gas produced in a 50 MWfuel gasification system. The developed gas cleaning washing process is basically a modification of the Rectisol process. Several different process configurations were evaluated using Aspen plus, including PC-SAFT for the thermodynamic modeling. The developed configuration takes advantage of only one methanol wash column, compared to two columns in a conventional Rectisol process. Results from modeling show the ability of the proposed configuration to remove impurities to a sufficiently low concentrations - almost zero concentration for H2S, CS2, HCl, NH3 and HCN, and approximately 0.01 mg/Nm3 for COS. These levels are acceptable for further upgrading of the gas in a methanation process. Simultaneously, up to 92% of the original CO2 is preserved in the final cleaned syngas stream. No process integration or economic consideration was performed within the scope of the present study, but will be investigated in future projects to improve the overall process.
Highlights
There is an increased global concern associated with the dependency on fossil feedstocks as the main source for energy as well as for various products, due to its harmful effect on the environment, and the issue of possible supply insecurity
Natural gas is becoming increasingly important as a primary energy source and is used for production of heat and power for domestic and industrial purposes, as well as a chemical feedstock
The study focuses on the development of an efficient gas cleaning and upgrading process for removing the impurities, especially sulfur compounds, but keeping the CO2 for a gasification system, based on the WoodRoll® process
Summary
There is an increased global concern associated with the dependency on fossil feedstocks as the main source for energy as well as for various products, due to its harmful effect on the environment, and the issue of possible supply insecurity. World energy consumption from 1971 to 2009 displays an average energy usage growth per year of approximately 100 million ton oil equivalent, or about 1.5% each year. A major part of this usage, about 80%, is supplied by fossil fuels, implying a profound dependency on fossil resources. In case of EU, the energy dependency data shows that about 64% of gas and 83% of oil demand in 2009 was imported, while these two fuels provide for about 60% of the of total EU energy need. Governments have established regulations to control the emissions and to reduce the amount of imported energy resources. The target for the EU climate policy is to reduce emissions down to 80% of the level of 1990, by 2020 [1]
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