The techno-economic performance of a coal fired power plant integrated with postcombustion capture is affected by not only the capture system but also the way the power plant is operated. The existing integration studies typically use amines as the CO2 capture absorbent. However, amines will degrade in the capture process and produce harmful substances. Ammonia is a robust, low-cost alternative solvent for reducing CO2 emissions from coal-fired power plants. On the basis of a 660 MW coal-fired power plant, this study analyzes the performance of the integration of coal-fired power plant with an ammonia-based CO2 capture process in three operation modes which include (1) reduction of power plant output compared to the original power station without CO2 capture and 85% CO2 capture efficiency, (2) the same power output as the original power station without CO2 capture and the same CO2 capture rate as in (1), and (3) the same power output as the original power station without CO2 capture and 85% CO2 capture efficiency. In each of three operation modes, we also analyzed the effect of stream extraction with and without auxiliary equipment energy consumptions in the CO2 capture process on the energy performance of the power plant. Results show that operation mode 2 exerts the least energy penalty on the power plant, but captures less CO2. On the premise of capturing as much CO2 as possible, operation mode 3 is the optimal operating mode, but the boiler and high-pressure cylinder require modification. Operation mode 3 is used as an example to analyze the effect of the solvent regeneration heat duty and temperature on the performance of the power plant. A decrease in heat duty is found to increase the system thermal efficiency and reduce the coal consumption rate and energy penalty. Lowering regeneration temperature while keeping the heat duty unchanged will improve the thermal efficiency of the system and reduce the coal consumption rate and energy penalty.

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Integration of coal-fired power plants with NH3-based CO2 capture is a promising technology for CO2 capture. However, the output and efficiency of the original coal-fired power plant are reduced because the integration requires energy. This work studied three typical coal-fired power plants with the capacities of 330, 660, and 1000 MW and turbine levels of N330-16.67/538/538, N660-24.2/566/566, and N1000-25/600/600, respectively. The integration of these coal-fired power plants with the same NH3-based postcombustion CO2 capture system was established. Heat consumption, energy penalty, and other evaluation indicators were obtained through an Ebsilon simulation. Among the three coal-fired power plants, the thermal efficiency of 1000 MW is the highest, whereas that of 330 MW is the lowest. The energy penalty of the 660 MW coal-fired power plant is the highest, whereas that of 330 MW is the lowest. To fully analyze the integration performance of power plants with different capacities, comprehensive evaluation of the gray correlation of an integrated system from six aspects based on the gray relational degree method is carried out. Analysis results show that the correlation coefficient of the 1000 MW coal-fired power plant is the highest, whereas that of 330 MW is the lowest. The energy consumption formula that was once proposed for a 660 MW coal-fired power plant is further optimized, and a new evaluation system of an integrated system combining an energy consumption formula and a gray correlation coefficient is presented.

This study investigates the multi-objective optimization of load dispatch of a solar-assisted coal-fired power generation system. The improved environmental/economic load dispatch model considers coal consumption, NO x emissions, and power purchase cost. The singular weighted method is utilized to solve this multi-objective and multi-constraint optimization problem. A power system that includes five power generators, one of which is retrofitted to a solar-assisted coal-fired unit, is also analyzed. It can be concluded that the loads of solar-assisted coal-fired units are higher than the original coal-fired unit, and with the increase of solar radiation, the gap between the loads of two units also increases. In addition, after retrofitting, the coal consumption, the NO x emission, and power costs of units reduce by about 2.05%, 0.45%, and 0.14%, respectively. From the study on the on-grid power tariff, where the tariff drops from 16.29 cents/kWh to 3.26 cents/kWh, NO x emissions drop from 12.31 t to 11.28 t per day, a reduction of about 8.38%. The cost of purchasing electricity decreases from $ 2,982,161.8 to $ 2,020,505.0 per day, a decrease of 32.25%. Therefore, when both coal-fired units and solar-assisted coal-fired units exist in a region, the use of solar-assisted coal-fired power generation units should be prioritized.Energies 2019, 12, 1284 2 of 16 157(2) When the temperature of the feed water out of the oil-water heat exchanger is lower than 158 that of the original second heater but higher than that of the original third heater. The feed water 159 enters the second heater. This mode is shown in (b) position. 160(3) When the temperature of feed water out of the oil-water heat exchanger is lower than that of 161 the original first heater but higher than that of the original second heater. The feed water enters the 162 first heater. This mode is shown in (c) position. 163(4) When the temperature of feed water out of the oil-water heat exchanger is higher than that 164 of the original first heater. The feed water enters the boiler. This mode is shown in (d) position.165 3. Methodology 166Under certain constraints, multi-objective optimization aims to have more than one goal to 167 achieve an optimal solution. One of the easiest ways to obtain the optimal solution is called standard 168 quantization or the singular weighted method. A weight is assigned to each target. All the targets 169 with their own weights are positioned together, and then the problem is solved under the same 170 constraints of the original problem. The obtained solution is a solution to the original problem (called 171 the Pareto solution). The weight arrangement is constantly changed; hence, different optimal

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