Innovative Zero-emission Coal Gasification Power Generation Project

1. Project summary

In order to achieve the 50% CO2 reduction targeted in Cool Earth 50 program, which is “a long-term target of cutting global emissions by a half from the current level by 2050 as a common goal for the entire world”, innovative technologies such as carbon dioxide capture and storage (CCS) are necessary to be developed in addition to very efficient use of energies, energy saving, switch to energy sources of low CO2 burden, and introduction of renewable power sources and/or nuclear power generation. It is strongly expected to reduce the CO2 emissions from the coal-fired thermal power generation plants by high thermal efficiency and much more efficient CCS.
The innovative zero-emission coal gasification power generation project aims to assess the technical feasibility on the comprehensive system covering the coal gasification power generation system to CCS, and to develop fundamental technologies to achieve the power generation efficiency after CO2 capture equivalent to that of conventional integrated gasification combined cycle (IGCC), 42% of transmission end efficiency (HHV basis). To achieve this target, CO2 after the combustion of the gasified fuel is recycled to gasifier, and then finally CO2 is captured without any gas separation.

2. Research issues

A new process concept is schematically drawn in Figure 1, where remarkable improvement of power generation efficiency is expected by using the recovered CO2 from the coal gasification system as a part of oxidizing agents of coals.
In this project, the following issues in the next-generation CO2-cycling IGCC system will be studied; (1) the effectiveness of CO2 addition in the oxidizing gases on the coal gasification performance, (2) the optimization of dry gas cleaning technology, and (3) the feasibility of the system for the practical-scaled plant and for the various coal resources in Asia-Pacific basin. Central Research Institute of Electric Power Industry (CRIEPI) and Kyushu University carry out jointly these issues from both fundamental and application aspects.

Figure 1. Schematic of the next-generation CO2-cycling IGCC system

3. Assigning tasks

“Development of next-generation CO2-capturing IGCC technology”
(1) Development of O2-CO2 gasification technology
(i) Analysis and assessment of basic gasification technology by O2-CO2
(ii) Elucidation of CO2 gasification mechanism and acceleration of gasification
(iii) Optimization of gasifier based on numerical analysis of O2-CO2 gasification
(2) Design and optimization of dry gas cleaning at high CO concentration
(3) Feasibility study (FS) for commercialization

Kyushu University
“Elucidation of O2-CO2 coal gasification mechanism and application to various coal resources in Asia-Pacific basin”
(1) Investigation of chemistry of O2-CO2 gasification
(2) Analysis of coals and minerals in coals and their behaviors in gasification
(3) Elucidation of physical properties, structures, and behaviors of ashes generated during gasification for the smooth operation
(4) Behaviors of CO-rich product gas in dry gas cleaning
(5) Pretreatment of coals for efficient gasification
(6) Some bases for CCS
(7) Analysis of mass and heat transfer in gasification reactor

4. Research at Kyushu University

(1) Analysis of O2-CO2 gasification
Chemical and physical behaviors of CO2 are analyzed in the O2-CO2 gasification of coals. The competitive adsorption of O2 and CO2 is firstly analyzed to quantify how much O2 and CO2 gasify the coals. Roles of char structure and minerals as well as the gasification conditions are studied in this gasification. The final goal of this research is to accelerate the gasification by CO2 and to find optimum content of CO2 for gasification efficiency and CO2 capture. It is also analyzed how much the recycled CO2 can bring in the heat and how much heat is required for the endothermic gasification by CO2. Optimum amount of recycled CO2 can be obtained by balance of all these factors.
(2) Analysis of char
Structure of chars, which should affect their reactivity in O2-CO2 gasification, is analyzed in terms of pore, surface, and bulk chemistries. Various techniques, such as XRD, Raman, 13C-NMR, SEM, TEM, XPS, and N2 adsorption, are applied to draw three-dimensional structure of chars. In addition, new gasification rate equation including structure of chars will be proposed.
(3) Analysis of ash
During the gasification processes, minerals included in coals become slag and fly ash. The slag and fly ashes do strongly influence on operability of the gasification system, and work as catalyst or inhibitor in the whole gasification system. Thus, the minerals in coals and chars are analyzed. Their changes and influences at heat treatments under gasification conditions, especially in O2-CO2 atmospheres, are analyzed in detail. The flux discharging efficiency and adhesion of the softened/molten/solidified inorganic substances in the coals will be particularly analyzed based on their glass-crystal states by applying solid state NMR, conventional and high temperature XRD, and SEM/TEM for particles.
(i) Structure of minerals and its change during the gasification is analyzed by XRD, multiple-nuclei solid state NMR, Raman, XRF, SEM, TEM, and N2 adsorption techniques to clarify the chemical species, structure, and size of polymeric inorganic glass and crystal. Remaining carbons which adhere to inorganic particles are very much concerned as factors for their sticking to the furnace wall and dissolution in the glass matrix.
(ii) Behaviors of minerals in coals and chars in the gasification will be studied by using TGA, high-pressure TGA, and drop tube furnace.
(iii) New gasification reaction rate equations considering the influences of minerals will be proposed.
(4) Establishment of simulation base for the present gasification system
Starting from applications of commercial simulators, our own simulators will be developed by taking properties and structure of materials present in the gasification process.