Dr Hui Song

This paper is concerned about a detailed techno-economic assessment of a hypothetical 500 MWe coal-fired power plant in New South Wales, Australia, for oxy-fuel conversion using integrated chemical looping air separation (ICLAS) technology and cryogenic air separation unit (CASU). The key objectives of this study are to (i) investigate and compare the detailed integration options for oxy-fuel conversion using ICLAS and CASU and (ii) determine the technical merits of the above integration options and the conditions at which the technologies become economically feasible. The study produced scientific evidence that confirms the viability of the CLAS process from both technical and economic points of view under certain conditions. The detailed technical analysis revealed that ICLAS with natural gas integration is energy-efficient compared to CASU running on parasitic load. This is primarily due to the fact that ICLAS needs less auxiliary power compared to CASU. Despite the fact that ICLAS natural gas integration has resulted in higher efficiencies than CASU running on parasitic load, from a series of detailed economic analyses, it was observed that both ICLAS and CASU may not be viable under the present operating and economic conditions. Nevertheless, from sensitivity analysis, it was concluded that ICLAS can become feasible if economic conditions are improved, e.g., a low natural gas market price (<$3.5/GJ), a high electricity wholesale price (>$59/MWh), and/or a high carbon tax (>$33/tonne).

The development of lignite-char-supported metal oxide catalyst for reduction of nitric oxide (NO) is investigated in this paper. The characteristics of NO reduction by copper and iron oxide catalysts supported on activated lignite chars (ALC) was studied using a fixed-bed reactor at 300 °C. The results showed that the impregnation of Cu on ALC resulted in higher catalytic reactivity during NO reduction compared with that of Fe. Chemisorption of O2 and NO on Cu/ALC catalyst was found to play an important role in denitrification. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyses showed that chemically adsorbed oxygen facilitates the formation of C(O) complex and oxidation of Cu0 to Cu+ for Cu/ALC catalyst. The C(O) intermediates and C*production formed due to the fact that C/O2 reaction promoted the reduction of NO. It is suggested that the catalytic reaction of NO in this case comprised of C/O2 reaction, C(O)/NO reaction and formation of N2 and CO2. Cu seemed to have significantly promoted the C(O) formation and CO oxidation compared with Fe. The catalytic reactivity of Cu species for C(O) formation and CO oxidation followed the order of Cu0 > Cu+ > Cu2 +. Fe3O4 was believed to be the active phase in Fe catalyst. The oxygen and char-supported metal catalysts significantly promoted C/NO reaction, and therefore may lead to a lower operation temperature of NOx removal.

The larger reactor volume, additional oxygen polishing unit, and carbon stripper for the separation of oxygen carriers and ash in the chemical looping combustion (CLC) and/or chemical looping oxygen uncoupling (CLOU) processes for solid fuels are anticipated not only to incur operational complexity but also to increase the capital and operating costs. As an alternative, this paper proposes a novel hybrid process, called "Chemical Looping Oxy Combustor (CLOC)". This novel process provides an integration of chemical looping air separation (CLAS) with fluidized bed oxy-fuel combustion and is expected to eliminate the need for an additional oxygen polishing unit and carbon stripper. It can be retrofitted to any existing coal circulating fluidized bed (CFB) at low cost. The other advantages of CLOC includes less solid handling issues, flexibility in handling low-grade coal with high moisture, no/less contamination of oxygen carriers, no/less slip of CO2/SOx in an air reactor, low energy penalty, etc. Also, in the CLOC process, coal combustion will occur in a separate fluidized bed combustor with relatively faster kinetics, because of the availability of high oxygen concentration (i.e., ~25-28 vol-"%), which eliminates the need for a larger fuel reactor volume. In the current paper, thermodynamic simulations of CLOC process using Cu-, Mn-, and Co-based metal oxide oxygen carriers were performed. Their performances were also compared against the conventional air-firing and oxy-firing technologies, e.g., oxy-fuel combustion integrated with cryogenic air separation unit (CASU) and CLOU. It was identified that the CLOC process needs external heat for reduction reactor provided by either direct or indirect methane combustion. Moreover, a maximum plant thermal efficiency was achieved for CLOC using Cu-based oxygen carrier. The energy penalty of the CLOC process, compared with the air-firing base case, was found to be ~2%-3%, which is ~4-5 times smaller than those of the CASU cases and only half of that of the CLOU process, indicating that CLOC offers a promising option for the combustion of solid fuels.

Coal will continue to dominate China s energy supply in the future. The mining of coal creates large amount of gangue which not only occupies a large area of land but also generate environmental problems. On the other hand, coal gangue is a low calorific fuel which should be utilized properly. A few small power plants are current running or under construction in China. However, due to its high ash content, coal gangue generates a large amount of ash when it is combusted in power plants. The ash from power stations not only contributes to emissions of fine particulates in the air but also results in the contamination of soil. The utilization of coal gangue ash is therefore important to reduce China s environmental pollution. In this paper, current status of the research and development of gangue ash utilization in China is reviewed. The gangue ash has found its application in a wide range of areas, such as road construction, chemicals, agriculture fertilizers, etc. Some ash samples were collected by the authors from a coal gangue fired power plant in Fuxin, northeast China. Characteristics of the ash were analyzed by using XRD, SEM, Laser sizer and other techniques. Because of its physical structure (e.g., large surface area and porosity) and its composition (i.e., containing mainly SiO2, Al2O3 and CaO) the gangue ash has a potential in the application of iron-based sorbents for high temperature removal of hydrogen sulfide from coal gas. A desulphurization sorbent was prepared by using the mixture of iron oxide and the gangue ash collected from the power plant. The structure and property of the surbent were examined using XRD, SEM and other techniques.