Coal-based Power Generation Systems Research Articles

High-efficiency power generation system with CO2 capture based on cascading coal gasification employing chemical recuperation

Coal-based power generation systems combined with CO2 capture can generate clean, efficient, decarbonized electricity and have recently received significant attention. This study proposes a high-efficiency power generation system with CO2 capture using cascading coal gasification coupled with chemical recuperation. The proposed system involves using waste heat from the gas turbine exhaust to start coal pyrolysis, achieving the first stage of chemical recuperative pyrolysis. Pyrolysis products, excluding coal gas (CG), are fed into the gasifier for the second stage of coal gasification. Furthermore, the sensible heat of syngas at the gasifier outlet is sequentially used to preheat the gasification agent and tar, supply heat for CG reforming, and generate steam. The cascading coal gasification and stepwise utilization of thermal energy decrease oxygen consumption during gasification and reduce the proportion of partially oxidized coal. The results indicate that, at a 90% carbon capture rate, the net power generation efficiencies of the proposed and reference systems are 40.26 and 37.58%, with exergy efficiencies of 39.22 and 36.55%, respectively. The improvements in the proposed system primarily stem from its highly efficient coal utilization, which decreased exergy destruction for the gasification process by 43%. These results imply the system may enhance efficient, low-carbon coal use.

Performance of hot-gas cleanup technology for clean coal processing

The integration of advanced coal-based power generation systems with hot-gas cleanup technology endows the former with higher efficiency and reduces their environmental impacts. Syngas from coal gasification or flue gas from combustion contains dust particulates that must be eliminated before the raw gas is burned in gas turbines to protect the turbine blade and control particulate emissions. The present work attempts to provide a general understanding of moving granular bed filters (MGBFs), which are regarded as a promising technology for hot-gas cleanup, and proposes a filtration technology for application to near-industrial environments. An experimental method was established to investigate the filtration processing of dust particulates under various operating conditions. The experimental facility included an air fan, two-stage gas heaters, a screw feeder for dust particulates, a measurement system to detect the size distribution of dust particulates, a filter granule supply device, a rotary valve, and an MGBF filled with filter granules. The collection efficiency of the MGBF was assessed at different temperatures ranging from room temperature to 500 °C and granular mass flow rates of 300–1500 g/min under a fixed filtration superficial velocity of 2100 cm/min and dust concentration 7500 ppmw. Variations in the outlet concentration and size distribution of dust particulates were measured to evaluate the dynamic characteristics of the cleanup process. Results revealed that an optimal mass flow rate must exist for high collection efficiency under specific operating temperatures. In addition, important design constraints were identified for the successful operation of the proposed MGBF system. The findings indicated that the proposed design could be useful in different cross-flow filter systems for gas cleanup. This work lays a solid foundation for future research on clean coal processing.

Coal Demand and Environmental Regulations: A Case Study of the Polish Power Sector

The impact of environmental regulations implemented in the power industry that affect the consumption of solid fuels is of key importance to coal-based power generation systems, such as that in Poland. In this context, the main purpose of the paper was to determine the future demand for hard coal and brown coal in the Polish power sector by 2050 with reference to the environmental regulations implemented in the power sector. To achieve these goals, a mathematical model was developed using the linear programming approach, which reflected the key relationships between the hard and brown coal mining sector and the power sector in the context of the environmental regulations discussed. The environmental regulations selected had a great influence on the future demand for hard and brown coal in the power generation sector. The scope of this influence depended on particular regulations. The prices of CO2 emission allowances and stricter emissions standards stemming from the Industrial Emissions Directive and the BAT (Best Available Techniques) conclusions had the largest influence on the reduction of hard coal demand. In the case of brown coal, no new power generating units would be deployed; hence, brown coal consumption would drop practically to zero in 2050 under all the scenarios considered.

Multi-objective optimization of a dual-layer granular filter for hot gas clean-up by using genetic algorithm

Granular filters are one of the most promising methods for hot gas clean-up in coal-based power generation systems. In order to further improve the filtration performance, a dual-layer granular filter is proposed, and multi-objective optimization via genetic algorithm is applied to optimize the geometric parameters. The optimization result is a Pareto front which includes a set of optimal solutions. Users can select each solution based on trade-offs between filtration efficiency, pressure drop, dust holding capacity and project limitations. An optimal case with relatively high efficiency, high deposition uniformity and low pressure drop is selected from the Pareto front. Numerical simulations are performed, and comparison of filtration performance between the optimal case and a single layer filter are conducted, to verify the superiority of the optimum structure. The optimum dual-layer granular filter has higher filtration efficiency than the single layer filter but with the expense of a small amount of pressure drop. The dual-layer granular filter also has higher deposition uniformity and higher dust holding capacity. Cleaning intervals for the dual-layer filter can be increased approximately 0.4 h, which gives the dual-layer filter better economic performance. The larger granular size in the first layer of dual-layer granular filter can let particles pass-through and deposit more uniformly than in the single layer filter, thus improving the dust holding capacity. The smaller granular size in the second layer also gives it better performance when filtering small particles.

Parameter study of filtration characteristics of granular filters for hot gas clean-up

Granular filters are a promising technology in hot gas clean-up for coal-based power generation systems. Numerical simulations are presented for the filtration characteristics of randomly packed granular filters. The effect of filter height is first investigated to obtain a unit height which can predict filtration characteristics of the entire filter, and it is found that the unit height should be at least 10 times the granule diameter. The filtration performance, including filtration efficiency, pressure drop and deposition uniformity are analyzed, and the effect of gas velocity, particle diameter and granule diameter are then investigated. The results show that the pressure drop increases rapidly with the increase of gas velocity and decrease with granule diameter. Increasing the gas velocity and particle diameter leads to increased filtration efficiency and decreased deposition uniformity. The effect of Stokes number on filtration efficiency and deposition uniformity can be divided into three regimes, and filter height and granule diameter need to be optimized according to Stokes number. A correlation of initial filtration efficiency is obtained for use in filter design and structural optimization.

Hot gas filters for coal-based power generation systems: Operating experiences

A semi-industrial filtration facility is currently in operation at the ETSI-University of Seville, with financial support from the European Commission and the Spanish Ministry of the Environment. This pilot plant allows testing different elements and reverse-flow pulse cleaning strategies using real coal ash and under diverse operating conditions such as temperature and pressure. The aim of the on-going research is the evaluation of the alternatives for hot gas filtration technologies and the optimisation of the operation and performance of the filtering elements.The first experimental campaign carried out in the filtration facility commenced in 2005. Four types of elements were tested at maximum temperature and pressure of 235°C and 7.5barg respectively. This paper describes the main results obtained during the second phase of the experimental campaign, in which the temperature was increased up to 370–550°C. Three types of elements (one type of bag filter and two types of candles) were tested. Main parameters investigated for the characterisation of the filtering elements performance were the pressure drop across the element, the cleaning pulse interval, the baseline pressure drop, the filtration efficiency and the durability of the elements. Dependences on the particle loading and temperature among others were also established. Results obtained and conclusions extracted provide a useful tool for the implementation of the filtration technologies at industrial scale.

Carbon balance of sugarcane bioenergy systems

An important criterion for bioenergy systems evaluation is their greenhouse gas mitigation potential. Sugarcane bioenergy systems are able to produce grid-bound surplus electricity but also have net CO 2 emissions associated with the upstream fossil-fuel consumption for plantation management, transportation and processing of the fibrous biomass. However, when compared to coal-based power generation systems, sugarcane bioenergy systems are able to avoid CO 2 emissions at rates that range between 1.081 and 1.137 kg CO 2/ k Wh depending on the cane-residue utilisation strategy adopted. As a consequence, sugarcane bioenergy systems stand out as promising energy projects for funding under the Kyoto Protocol's proposed clean development mechanism and joint implementation.

97/01263 A review of ash in conventional and advanced coal-based power systems

Process conditions are briefly described for conventional and advanced power systems. The advanced systems include both combustion and gasification processes. We discuss problems in coal-based power generation systems, including deposition, agglomeration and sintering of bed materials, and ash attack are discussed. We also discuss methods of mitigating ash problems and anticipated changes anticipated in ash use by converting from conventional to advanced systems.

95/06395 The Power Systems Development Facility at Wilsonville, Alabama

One of the Morgantown Energy Technology Center`s (METC`s) goals is to: {open_quotes}Commercialize Advanced Power Systems with improved environmental performance, higher efficiency, and lower cost. {close_quotes} Advanced coal-based power generation systems include Integrated Gasification Combined Cycle (IGCC), Pressurized Fluidized- Bed Combustion (PFBC), and Integrated Gasification/Fuel Cell systems. The strategy for achieving this goal includes: (1) Show the improved performance and lower cost of Advanced Power Systems through successful Clean Coal Technology demonstration projects, (2) Build and operate Technology Integration Sites in partnership with U.S. Industry (these sites will resolve key technology issues and effect continuous product improvement, and these partnerships result in leveraging of research and development (R&D) funds), and (3) Set up partnerships with other agencies and organizations such as Electric Power Research Institute (EPRI) to leverage R&D funds and skills. Demonstration of practical high-temperature particulate control devices (PCD`s) is crucial to the evolution of advanced, high- efficiency coal-based power generation systems. There are stringent particulate requirements for the fuel gas for both turbines and fuel cells. In turbines, the particulates cause erosion and chemical attack of the blade surfaces. In fuel cells, the particulates cause blinding of the electrodes. Filtration of the incoming, hot, pressurized gas is required to protect these units. Although filtration can presently be performed by first cooling the gas, the system efficiency is reduced. Development of high temperature, high pressure filtration is necessary to achieve high efficiency and extend the lifetime of downstream components to acceptable levels.

Low Emissions Combustor Development for an Industrial Gas Turbine to Utilize LCV Fuel Gas

Advanced coal-based power generation systems such as the British Coal Topping Cycle offer the potential for high-efficiency electricity generation with minimum environmental impact. An important component of the Topping Cycle program is the gas turbine, for which development of a combustion system to burn low calorific value coal derived fuel gas, at a turbine inlet temperature of 1260°C (2300°F), with minimum pollutant emissions, is a key R&D issue. A phased combustor development program is underway burning low calorific value fuel gas (3.6-4.1 MJ/m3) with low emissions, particularly NOx derived from fuel-bound nitrogen. The first phase of the combustor development program has now been completed using a generic tubo-annular, prototype combustor design. Tests were carried out at combustor loading and Mach numbers considerably greater than the initial design values. Combustor performance at these conditions was encouraging. The second phase of the program is currently in progress. This will assess, initially, an improved variant of the prototype combustor operating at conditions selected to represent a particular medium sized industrial gas turbine. This combustor will also be capable of operating using natural gas as an auxiliary fuel, to suit the start-up procedure for the Topping Cycle. The paper presents the Phase 1 test program results for the prototype combustor. Design of the modified combustor for Phase 2 of the development program is discussed, together with preliminary combustion performance results.

Application of Ceramic Membranes in Advanced Coal-based Power Generation Systems

Abstract The U.S. Department of Energy is researching high-temperature ceramic gas separation membranes. DOE will demonstrate the feasibility of using these membranes to remove the sulfur and nitrogen contaminants found in gas streams of advanced coal-based power generation systems. These contaminants must be removed to protect not only the turbine system components but also the environment. This paper discusses the integration of passive, faciltated, and catalytic membranes, and the expected benefits of applying this membrane technology.