Abstract
Underground Coal Gasification (UCG) enables the utilisation of coal reserves that are currently not economically exploitable due to complex geological boundary conditions. Hereby, UCG produces a high-calorific synthesis gas that can be used for generation of electricity, fuels and chemical feedstock. The present study aims to identify economically competitive, site-specific end-use options for onshore and offshore produced UCG synthesis gas, taking into account the capture and storage (CCS) and/or utilisation (CCU) of resulting CO 2 . Modelling results show that boundary conditions that favour electricity, methanol and ammonia production expose low costs for air separation, high synthesis gas calorific values and H 2 /N 2 shares as well as low CO 2 portions of max. 10%. Hereby, a gasification agent ratio of more than 30% oxygen by volume is not favourable from economic and environmental viewpoints. Compared to the costs of an offshore platform with its technical equipment, offshore drilling costs are negligible. Thus, uncertainties related to parameters influenced by drilling costs are also negligible. In summary, techno-economic process modelling results reveal that scenarios with high CO 2 emissions are the most cost-intensive ones, offshore UCG-CCS/CCU costs are twice as high as the onshore ones, and yet all investigated scenarios except from offshore ammonia production are competitive on the European market.
Highlights
Underground Coal Gasification (UCG) can be an economic method to increase worldwide coal reserves by utilisation of coal deposits that are currently not mineable by conventional methods.Hereby, a target coal seam is converted by the injection of a gasification agent into a synthesis gas within a controlled, sub-stoichiometric gasification process [1,2,3,4,5]
We used the Cost of Electricity (COE) calculation according to Nakaten et al [5], based on UCG synthesis gas electrification in a combined cycle gas turbine power plant (CCGT) with an operational efficiency of 58% and a capacity of 100 MW net power generation
We further investigated the impact of different synthesis gas calorific values (CV) and related synthesis gas compositions, as the CV determines UCG synthesis gas end-utilisation options in view of its economical suitability for commercialisation
Summary
Underground Coal Gasification (UCG) can be an economic method to increase worldwide coal reserves by utilisation of coal deposits that are currently not mineable by conventional methods. A target coal seam is converted by the injection of a gasification agent into a synthesis gas within a controlled, sub-stoichiometric gasification process [1,2,3,4,5]. UCG synthesis gas is applicable for different end-use options, such as the provision of chemical raw materials, liquid fuels, hydrogen, fertilizers or electricity (cf Figure 1). The early idea of UCG and its evolution has a long history that was picked up especially at times of raw material scarcity.
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