Standard Coal Consumption Rate Research Articles

A novel solar-aided lignite-fired power generation system with calcium looping CO2 capture, lignite pre-drying and feedwater preheating

Integrating solar heat and calcium looping (CaL) process into the existing lignite-fired power generation system is a promising technology to control CO2 emission. However, the heat released from carbonation process led to the temperature increase of exhaust flue gas together with heat losses in boiler. To recover the waste heat from the exhaust flue gas, this paper proposed a solar-aided lignite-fired power generation system with CaL process CO2 capture, lignite pre-drying and feedwater preheating (i.e., design III). Besides, design I without waste heat recovery and design II with only lignite pre-drying were simulated for comparison. Through the case study based on a solar-aided 330 MW lignite-fired power generation system, thermal and techno-economic performance of design III was the best on the design condition. Its standard coal consumption rate was 374.44 g/kWh, which was 61.12 g/kWh and 8.24 g/kWh lower than design I and design II, respectively. With the new design, the annual net profit of design III is $18.2924 M, with $0.5652 M higher than design II. The sensitivity analysis indicated that the thermal performance of design III was also the best under various conditions of CO2 capture efficiency and integrated solar heat.

A novel solar tower assisted pulverized coal power system considering solar energy cascade utilization: Performance analysis and multi-objective optimization

Solar-assisted pulverized coal power systems offer higher solar energy utilization efficiency, enabling pulverized coal power plants to rapidly achieve energy-saving and emission-reduction targets. This study proposes the incorporation of two solar heaters to create a new solar tower assisted pulverized coal power (STPCP) system for the cascade utilization of solar energy. A comprehensive performance analysis, considering both power-boosting (PB) and fuel-saving (FS) operation modes, has been conducted. The multi-objective particle swarm optimization method is then applied to optimize the system from both thermal and economic perspectives. The findings demonstrate that in FS mode, annual coal consumption decreases by 24.35 × 103 tons, while in PB mode, annual power generation increases by 94.12 GWh. The optimization analysis demonstrates that the optimal cost of electricity (COE) and annual standard coal consumption rate in PB mode are 1.4 × 10−4 USD/kWh and 4.3 g/kWh lower than those in FS mode. Additionally, as the solar field cost declines, the optimal COE and annual standard coal consumption rate gradually decrease. While, increasing coal prices result in higher optimal COE, but lower optimal annual standard coal consumption rate. Based on this study, it can be inferred that the STPCP system shows promising prospects in the future.

Enhancing the flexibility and stability of coal-fired power plants by optimizing control schemes of throttling high-pressure extraction steam

Regulating the thermal system configuration can improve the ramp-up rate of the coal-fired power plants during peak shaving transient processes, while it may bring penalties in the performance of the steam temperature control and thermal efficiency. This study simulated the load ramping up transient processes when throttling the extraction steam of high-pressure heaters. The results show that there is a gap between the needed energy and energy supply caused by drastic fluctuations of reheat steam flowrate. Control schemes of steam temperatures and fuel demands were revised considering the dispatch of the fuel and working medium. According to economic optimality, the order of throttling high-pressure heaters was optimized. By implementing the revised control strategies, the fluctuations of steam temperatures were diminished and the maximum deviation of live and reheat steam temperatures was reduced by 23.5 °C and 11.4 °C, respectively. The flexibility indicator was increased by up to double at most. The average standard coal consumption rate variations with and without the revised control schemes were compared and the maximum difference is 1.23 g kW−1 h−1 with 2.5 % Pe min−1. The flexibility and economic performance were both improved when adopting the revised control schemes.

Performance enhancement of a solar-assisted pulverized coal power system by integrating a supercritical CO2 cycle

Current solar-assisted pulverized coal power (SPCP) systems lack the efficient cascading utilization of solar energy, resulting in its wastage. Therefore, there is a need to optimize the integration scheme between solar energy and pulverized coal power systems. In this study, the integration of two different supercritical CO2 cycles with SPCP systems is proposed to enable the cascaded utilization of solar energy. The thermal performances of the two proposed power systems are presented. Then, a sensitivity analysis is performed to examine the effects of supercritical CO2 cycle variables on the system. Finally, an economic evaluation is conducted to examine and compare the economic performance. The results demonstrate significant reductions in the extraction steam superheat and the exergy loss in feedwater heaters. Compared to SPCP systems, both proposed systems exhibit a decrease in the standard coal consumption rate by approximately 4.7 g/kWh. Sensitivity analysis shows that the CO2 mass flow rate has the most important effect on the system performance. The economic evaluation reveals that the cost of electricity for the two suggested systems increases by only about 0.04 cents/kWh. In summary, the findings suggest that the proposed power systems exhibit superior thermal performance and confirm its economic feasibility in the future.

Carbon reduction and flexibility enhancement of the CHP-based cascade heating system with integrated electric heat pump

The energy utilization efficiency and the flexibility enhancement of the combined heat and power (CHP) plant can promote both decarbonization and renewable energy integration. In this research, we proposed a novel CHP cascade heating system by integrating it with the electric heat pump (EHP). The integration of EHP can consume power generation load and bear part of the heat load, which improves the flexible peak regulation ability of the novel heating system. Based on the detailed simulation model of a typical 2 × 300 MW subcritical CHP plant, the reference and novel systems are compared in thermodynamic and peak-load regulation performance to present the benefits of the EHP design. The results showed that, under the design condition, the heating capacity in the novel system had an increment of 6.02 % to that in the reference system, bringing out a 4.51 % improvement in electricity generation efficiency. Correspondingly, the average standard coal consumption rate for generating of the novel system reduced by 9.53 g/kWh. Under the same heat load, the peak shaving lower limit of the novel system is 59 MW lower than the reference system on average, and the load rate is reduced by 10 % of the rated power generation capacity on average. In the case study, under the typical day operation of the regional electric-thermal integrated energy system, the wind power curtailment ratio of the novel system is 10.75 % lower than that of the reference system. Meanwhile, with further waste heat recovery, the daily standard coal consumption of the novel system can be saved by 231.81 t, equivalent to a reduction of 607.34 t of CO2 emissions.

Performance study of a novel supercritical CO2 solar-coal supplementary power generation system

• New supercritical CO 2 solar-coal supplementary power generation system is proposed. • The annual solar generating power accounts for 61.29% of the total power output. • Standard coal consumption rate is 161.11 g/kWh lower than pure coal-fired system. • The new system performances with the change of the load rate are revealed. • Effects of solar multiple and thermal energy storage capacity on new system are studied. To reduce the CO 2 emission and improve the solar energy utilization rate, a novel supercritical CO 2 solar-coal supplementary power generation system is proposed. Compared with the previous studies on supplementary systems, the novel system takes solar energy as the main heat source instead of coal, which greatly increases the proportion of solar energy input. The results show that, when the solar multiple (parameter representing the area of the heliostat field) is 3 and the thermal energy storage capacity is 16 h, on the summer and winter solstices, the proportions of solar generating power are 100% and 57.15%, respectively. The novel system can operate steadily during the whole year. The annual solar generating power is 161.07 GWh, accounting for 61.29%. The standard coal consumption rate of the novel system is 101.76 g/kWh, 161.11 g/kWh lower than that of the pure coal-fired system. The exergy efficiency for the novel system increases with an increasing operation load rate. Under 50%, 75%, 100%, and 125% load rates, the exergy efficiencies are 16.7%, 25.0%, 33.4%, and 38.0%, respectively. It is the first time to study the effects of the solar multiple and the thermal energy storage capacity on the energy, exergy, environmental, and economic performances of the supercritical CO 2 solar-coal supplementary power generation system. When the thermal energy storage capacity is 16 h, the solar multiple corresponding to the optimal economic performance is 2.5.

Performance upgrading of supercritical unit on preferable operation mode with promoting feed water temperature

Promoting feed water temperature (FWT) at low loads for supercritical unit has proved to be an effective technology to ensure denitrification capacity of Selective Catalytic Reduction (SCR). However, operational economy of unit is significantly reduced on conventional intermediate point temperature (IPT) setting mode. Hence, a superior operation strategy defined as IPT regulating mode for supercritical unit is proposed. Mathematical method was further developed. Then, operation characteristics on economy and pollutant emission of a 660 MW supercritical unit are investigated on IPT regulating mode. A series of influencing mechanisms were revealed. Simultaneously, individual significant parameters were compared with that of traditional operation strategy. Results shows, supercritical unit with increasing FWT achieve a better performance on IPT regulating mode. Compared with traditional operation strategy, NOx emission are fully up to requirement. Concurrently about 2.89 g/kWh in standard coal consumption rate is decreased and 37.3 MW increasing in power generation is achieved averagely. Moreover, such operation strategy also makes superheated steam temperature maintain rated value. Reheated steam temperature promotes by 27.3 ℃ averagely, and become more smooth and steady. This study also reveals that advantages of proposed strategy will be more prominent with higher FWT and lower operating load.

Thermal system for comprehensive utilization of boiler and steam turbine energy of coal-fired power units based on the S-CO2 cycle

In this study, an additional S-CO2 cycle system configuration for coal-fired power units has been proposed. This system achieves cascade utilization of steam turbine extraction and boiler flue gas energy, to improve the coal-fired power unit generation efficiency. Thermodynamic analyses were carried out for the new thermal system based on energy and exergy analyses. The results show that under the turbine heat acceptance (THA) condition, the proposed thermal system could reduce the standard coal consumption rate by 0.91% in coal-fired power units. Furthermore, the factors affecting the system performance are analyzed, and the effect laws of various elements on the total investment and payback period are derived. The suggested thermodynamic system provides a method for using energy on both sides of the boiler and steam turbine.

Performance assessment of the novel coal-fired combined heat and power plant integrating with flexibility renovations

The operational flexibility of coal-fired combined heat and power (CHP) plants is critical for the power grid to accommodate high-penetration renewable energy. Flexibility renovations, including the high back-pressure (HBP) renovation and the low-pressure turbine zero power output (LZPO) renovation, are integrated within CHP plants and can enhance the heat-power supply flexibility. In this study, the existing two renovations are compared in consideration of flexibility, energy and exergy performance. The performance assessment of the novel CHP plant integrating with flexibility renovations are conducted. Quantitative analyses are then conducted on a characteristics day. Results show that compared with the HBP renovation, the LZPO renovation presents greater potential to improve the accommodation of renewable energy and energy efficiency, whereas is not satisfactory in larger exergy loss. Besides, compared with the conventional plant, the feasible peak-shaving capacity and heating capacity of the novel renovated plant are improved by 43 MW and 320 MW, respectively. The maximal energy utilization efficiency increases from 71.70% to 80.91%, and the exergy loss decreases from 216.9 MW to 151.2 MW. Moreover, the accommodation of renewable energy increases by 5.1 million kWh while the standard coal consumption rate for power generation decreases from 248.3 g/kWh to 222.3 g/kWh.

A high-efficiency and eco-friendly design for coal-fired power plants: Combined waste heat recovery and electron beam irradiation

To ensure the sustainable development of the economy and society, energy-saving and emission reduction is an inevitable choice to solve resource scarcity and control environmental pollution, while coal-fired power plants are an important industry to implement this strategy. A novel design combining organic Rankine cycle with electron beam flue gas treatment is proposed to reduce pollutant emissions and recover flue gas waste heat of 600 MW power plant. The flue gas flows through the organic Rankine cycle to recover waste heat, then enters the electron beam irradiation device for desulfurization-denitrification, and eventually generates by-products of ammonium sulfate and ammonium nitrate that could be applied in agriculture. The particle swarm optimization algorithm is employed to improve the thermodynamic, economic and environmental performance, then the most suitable scheme is selected by combining TOPSIS and the entropy weight method. The optimization results indicate that the integrated system could produce equivalent electric quantity of 22.58 MW, and the payback period is 4.91 years. Meanwhile, ammonium sulfate and nitrate with production of 3544 kg/h and 6165 kg/h are obtained. Compared with the referenced power plant, the thermal efficiency of the improved scheme increases by 1.26% and the standard coal consumption rate decreases by 2.72%.

Thermal and economic performances comparison of different pulverized coal power systems augmented by solar trough or tower technologies

In this study, three different solar-assisted pulverized coal power (SPCP) systems utilizing solar trough or tower technologies are investigated and compared. In scheme 1, the parabolic trough solar collector is parallel to the high-pressure feed-water heaters. In scheme 2, the solar tower field is parallel to the boiler. In scheme 3, the solar tower field is connected in series between intermediate- and low-pressure cylinders. Results show that even though the same amount of solar energy is introduced into the three SPCP systems, the exergy that can be efficiently utilized differs due to the varying integrating temperature range in these three SPCP systems. The standard coal consumption rates of SPCP systems are lower when compared with the pulverized coal power system, but the levelized costs of electricity of SPCP systems are higher due to the heavy solar field investment. Among all the SPCP systems, scheme 3 owns the lowest standard coal consumption rate (275.11 g/kWh) and levelized cost of electricity (4.30 US$/kWh). Therefore, scheme 3 is recommended for the development of SPCP in the near and midterm. The economic performance of SPCP systems will improve as coal price rises or solar field cost falls when compared with the pulverized coal power system.

Performance analysis of an efficient waste heat utilization system in an ultra-supercritical coal-fired power plant

With the rise of new energy sources in the power industry, improving the efficiency of coal-fired power plants is essential. Currently, the leading main causes of irreversible energy loss are the energy level mismatches of boilers and turbines. An ultra-supercritical coal-fired power plant thermodynamic system was reconstructed based on the first and second laws of thermodynamics to improve the efficiency of power plants, and an efficient condensate water preheating air integrated bypass flue waste heating efficient utilization system is thus herein proposed. Consequently, high and medium steam turbine extraction flow is returned to the steam turbine to do work, and cold source loss is reduced by increasing the extraction steam flow of the low-pressure cylinder. At the same time, the inlet air temperature in the air preheater is significantly increased by preheating the hot air with condensate water, resulting in a reduced heat transfer temperature difference and significantly improved exergy efficiency. Compared with conventional low-temperature economizer and bypass flue waste heat utilization schemes, the results indicate that the heat transfer exergy efficiency increased significantly from 78.49% to 95.88% in the air preheater, and the heat consumption rate of the turbine generator set decreased by 108.06 kJ/(kW⋅h). The generation efficiency increases by 0.74%, while the standard coal consumption rate decreases by 3.92 g/(kW⋅h). In terms of economic investment, the dynamic payback period is 3.31 years and the net present value is $2.20 M/year. This paper provides an effective energy conservation and emission reduction plan for coal-fired power plants to contribute towards achieving national carbon peaking and carbon neutrality goals.

Modeling and Off-Design Performance Analysis of a Screw Expander-Based Steam Pressure Energy Recovery System in a Combined Heat and Power Unit.

A screw expander-based heating system is proposed based on a 330 MW combined heat and power unit to recover the extraction steam pressure energy. EBSILON Professional software was applied to model the proposed system, and the thermal performance of the traditional system and the new system was compared under different operating conditions. The results show that under the designed heating condition, the standard coal consumption rate of the new system is reduced by 4.74 g/kWh, and the exergy efficiency of the heating process is increased by 17.29%. When the extraction steam pressure changes with the load within a range greater than 0.1 MPa, there is an optimal operating range for the new system, which is related to the built-in pressure ratio of the screw expander and the extraction steam pressure difference, and the distribution of the optimal operating range varies with the supply-water temperature. The heating process exergy efficiency of the two systems shows opposite trends under off-design conditions. Additionally, under the condition of meeting the extraction steam pressure, the method for increasing the output power of the screw expander by adjusting the butterfly valve to increase the extraction steam pressure only increases the standard coal consumption rate of the system. Furthermore, through an application case study, the annual economic benefit of the new system is expected to be ¥ 4.15 million, and the payback period is 5.02 years.

Performance study of solar tower aided supercritical CO2 coal-fired power generation system with different schemes

Solar tower aided coal-fired system can obviously reduce coal consumption and CO2 emission, but there are few studies on integration system using supercritical CO2 (S-CO2) Brayton cycle. Therefore, in this paper, three new solar tower aided 300 MW S-CO2 coal-fired power generation systems with different integration schemes are proposed and their performances are studied and compared. In the schemes 1, 2, and 3, the solar energy is used to replace the partial heat loads of the low-temperature recuperator, the superheated surface, and the reheated surface, respectively. The results show that performances of new integration systems are significantly better than those of the traditional S-CO2 coal-fired power station in terms of standard coal consumption rate and CO2 emission rate. The standard coal consumption rates of schemes 1, 2, and 3 are reduced by 7.71 g/kWh, 9.95 g/kWh, and 10.54 g/kWh, respectively. Compared with the traditional S-CO2 coal-fired power station, the boiler exergy losses of new integration systems are obviously reduced, of which scheme 3 is reduced by 13.7 MW. After comprehensive consideration and comparison, the scheme 3 is the optimal system. In addition, influences of both the solar energy and operation load on the performances of scheme 3 are studied. The results show that under off-design conditions, the solar generating power, the solar field efficiency and the solar-to-electricity efficiency of scheme 3 increase with an increasing solar energy. Under the 100% load rate, when the solar energy increases by 1 MW, the solar generating power increases by about 0.35 MW on average. The proportion of power generation from solar energy increases with a decreasing operation load. When the solar energy is 40 MW, the proportions of power generation from solar energy at 100%, 75%, and 50% load rates are 3.44%, 4.52%, and 6.50%, respectively.

Flexibility and efficiency co-enhancement of thermal power plant by control strategy improvement considering time varying and detailed boiler heat storage characteristics

Flexibility enhancement of coal-fired power plants is extremely urgent to accommodate high-penetrated renewable energy and maintain the stability of power grid. Cycling rate, an important aspect of operational flexibility of coal-fired power plants, is mainly dragged by the large boiler thermal inertia. The idea of this study is to enhance the flexibility of the power plant by clarifying and considering the time varying and detailed boiler heat storage characteristics. The dynamic simulation and control models of a double-reheat power plant are developed and validated. The time varying and detailed boiler heat storage characteristics are represented by the principal parameters obtained by using stepwise regression algorithm. The improved control strategy is proposed and its performances are examined. Results show that the improved control strategy can enhance load cycling rate from 9.9 MW min−1 to 23.1 MW min−1, and the accumulative standard coal consumption rate can be reduced by 0.47%. Moreover, the control parameters, including output power and steam temperature, can reach the target quickly and are accurately controlled. The improved control provides a detailed guidance for the trade-off between the flexibility and high-efficiency in power plants during load cycling processes.

Energy and exergy analyses of a novel cogeneration system coupled with absorption heat pump and organic Rankine cycle based on a direct air cooling coal-fired power plant

A novel cogeneration system in which the combination of an organic Rankine cycle (ORC) and an absorption heat pump (AHP) are applied to recover condensate waste heat of exhaust steam from steam turbine in a direct air cooling coal-fired power plant is put forward to further improve energy utilization efficiency in the paper. The novel cogeneration mode can achieve multiple purposes of increasing power generation, improving heating load, reducing irreversible heat exchange loss of heating network and preventing from freezing for air cooling system in winter. The energy and exergy analyses have been accomplished for a 600 MW direct air cooling coal-fired power plant based on the first and second laws of thermodynamics. The generated power and heating load increase by 16.2 MW and 78,541.16 kW at 50% THA (Turbine heat acceptance) as heating flow rate is 100 kg/s in the novel cogeneration mode. The standard coal consumption rate and total exergy loss decrease by 48.98 g/kWh and 62.21 MW. The total energy and exergy efficiency respectively improve by 11.97% and 4.01%. Besides, the total exergy efficiency is increased with increasing load. The proposed scheme can provide a new method for energy conservation and icing protection of direct air cooling units in winter.

Optimization for Circulating Cooling Water Distribution of Indirect Dry Cooling System in a Thermal Power Plant under Crosswind Condition with Evolution Strategies Algorithm

Crosswind has an adverse impact on the performance of an indirect dry cooling system. In order to mitigate the adverse influence, this study redistributed the circulating cooling water among air-cooled heat exchanger sectors so that the performance of the indirect dry cooling system could be improved. An evolution strategies algorithm combined with numerical effectiveness-based heat exchanger model was established to minimize the operation costs of the whole system. Based on a 660 MW practical power plant, optimal circulating cooling water operation strategies under varied crosswind speeds and ambient temperatures were calculated to show its application. According to the calculated results, the performance of the indirect dry cooling system could be enhanced by optimizing circulating cooling water distribution under any crosswind speed, especially under high ambient wind speeds. There is a slight promotion of the coal savings with a rise in ambient temperature: improvements of about 5%. The standard coal consumption rate could save as much as 2.50 g/kWh under crosswind speed of 10 m s−1 and ambient temperature of 32 °C, compared to the 0.1 g/kWh under crosswind speed of 2 m s−1 and ambient temperature of 32 °C.

Operation strategies of axial flow fans in a direct dry cooling system under various meteorological conditions

AbstractFor a direct dry cooling system, the turbine back pressure fluctuates with the meteorological conditions. Moreover, the operation of axial flow fans plays an important role in the cooling performance of air‐cooled condensers (ACC). It is of significant use to study the operation strategies of axial flow fans under various ambient conditions. Based on typical 2 × 660 MW direct dry cooling power generating units, the ACC model coupled with the turbine thermodynamic characteristics is developed, by which the thermo‐flow performances of the ACC are predicted in the dominant wind direction, and then the standard coal consumption is calculated. The results show that the increased ambient temperature and wind speed, or the reduced fan rotational speed leads to the high turbine back pressure. At the low ambient temperature and wind speed, the standard coal consumption rate of the unit can be reduced by reducing the speed of axial flow fans appropriately, with the maximum drop in coal consumption rate reached 0.734 g/(kWh) when the ambient temperature is 10°C without wind. If the wind speed exceeds 12 m/s or the ambient temperature reaches 25°C, 110% of the rated fan rotational speed is recommended.

Design and Performance Analysis of New Ultra-Supercritical Double Reheat Coal-Fired Power Generation Systems

In order to solve the existing problems of large mean heat transfer temperature differences of regenerative air heaters and high superheat degrees of regenerative extraction steam in double reheat coal-fired power generation systems, two new design schemes of ultra-supercritical double reheat cycles are proposed, which can realize the deep boiler-turbine coupling among the heat transfer processes of air, feeding water and regeneration extraction steam on the base of the principle of energy level matching. A typical 1000 MW ultra-supercritical double reheat cycle system is selected as the reference system and the overall system model is built by using the Ebsilon simulation software. The performances of two new systems are analyzed by using both the exergy method and energy equilibrium method. The results show that net output powers of both new systems 1 and 2 increase by 6.38 MW and 6.93 MW, respectively, and the standard coal consumptions of power generation decrease by 1.65 g/kWh and 1.79 g/kWh, respectively. The off-design performances of new systems and the reference system are analyzed, and the results show that performances of two new systems are better than that of the reference system. The system flow of the new system 2 is more complex compared with that of the new system 1. Generally speaking, the performance of new system 1 is better than that of new system 2. On the basis of new system 1, new system 3 is further optimized and its full operating condition performance characteristics are analyzed. The standard coal consumption rate of new system 3 is reduced about 1 g/kWh at higher load, and around 0.2 g/kWh at low load.

Exergy and thermo-economic analyses and performance comparison of different solar aided coal-fired power systems

A solar aided coal-fired power (SACP) system has proven to be an efficient method to use solar energy on a large scale and reduce fossil fuel consumption in coal-fired power systems. In this study, three different SACP systems were investigated using thermo-economic analysis method to evaluate the systems’ production performance in detail. Moreover, sensitivity analysis was performed to explore the influences of the coal price and solar field investment. The exergy analysis shows that, for all these systems, the boiler and solar field have the largest and second-largest exergy destruction, respectively. The exergy cost and thermo-economic cost analyses show that the SACP system, where the solar field is placed between intermediate- and low-pressure turbines, has the best system performance. The unit exergy cost and the unit thermo-economic cost of the electricity of this system are 2.60 kW/kW and 7.96 US$/GJ, respectively. Furthermore, the standard coal consumption rate of this system is 275.16 g/kWh. The sensitivity analysis shows that with continuing solar field cost reductions, the unit thermo-economic cost of the electricity will further decrease in the future.