Process to Produce a Methane Rich Gas Mixture From Gasification Derived Sulphur Containing Synthesis Gases

Abstract

A method for converting a raw gas into a methane-rich and/or hydrogen-rich gas includes the following steps: a) providing the raw gas stemming from a coal and/or biomass gasification process, thereby the raw gas comprising beside a methane and hydrogen content carbon monoxide, carbon dioxide, alkanes, alkenes, alkynes, tar, especially benzole and naphthalene, COS, hydrogen sulfide and organic sulfur compounds, especially thiophenes; thereby the ratio of hydrogen to carbon monoxide ranges from 0.3 to 4; b) bringing this raw gas into contact with a catalyst in a fluidized bed reactor at temperatures above 200° C. and at pressures equal or greater than 1 bar in order to convert the raw gas into a first product gas, thereby simultaneously converting organic sulfur components into hydrogen sulfide, reform tars, generate water/gas shift reaction and generate methane from the hydrogen/carbon monoxide content; c) bringing the first product gas into a sulfur absorption process to generate a second product gas, thereby reducing the content of hydrogen sulfur and COS from 100 to 1000 ppm down to 1000 ppb or less; d) optionally bringing the second product gas into a carbon dioxide removal process to generate a third product gas at least almost free of carbon dioxide; e) bringing the third product gas into a second methanation process to generate a fourth product gas having a methane content above 5 vol %; f) optionally bringing the fourth product gas into a carbon dioxide removal process to generate a fifth product gas at least almost free of carbon dioxide g) bringing the fifth product gas into an hydrogen separation process in order to separate a hydrogen rich gas from a remaining methane-rich gas, called substitute natural gas.

Description

[0001]The present invention relates to a method for converting coal or biomass to at least almost sulfur-free substitute natural gas. Further, the invention relates to a process to produce a methane rich gas mixture from gasification derived sulphur containing synthesis gases.[0002]In particular, the present invention relates to a continuous production process of synthetic natural gas (SNG) from biomass, coal or naphta. More specifically, the present invention relates to the production of clean gaseous heating fuels from these less valuable sulphur containing hydrocarbonaceous materials.DESCRIPTION OF THE PRIOR ART[0003]The production of SNG from biomass is the conversion of a “dirty / difficult” fuel into a clean burning well known commodity. The costumer has the freedom to use the SNG for power generation, heating or mobility. A big plus is the already existing infrastructure such as pipelines and compressed natural gas (NG) cars. To insert the product gas of the methanation into th...

AI Technical Summary

Problems solved by technology

Drawbacks of this kind of raw gas are the high amount of poisonous components, such as alkenes, alkynes, H2S, COS, organic S-species, HCN, NH3, organic N-species.

Disadvantage of this process scheme is the high number of operation units and the different temperature levels of the units (especially cooling down to the scrubber temperature).

However, the raw gas composition is less favorable for the SNG synthesis as the SNG composition results in higher energetic losses.

First, the energetic effort in the gasification unit is higher for the production of pure H2, CO, CO2-mixtures; secondly the pure H2, CO, CO2-mixtures result in higher thermal losses in the synthesis due to the exothermic enthalpy of the methanation reaction.

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