Thermal efficiency of coal-fired power plants: From theoretical to practical assessments

Abstract

The improvement in thermal efficiency for coal to power processes is increasingly important due to concerns on CO2 emissions. This paper presents a systematic study on direct combustion coal to power processes with respect to thermodynamic, technical and economic factors. Traditional exergy analysis focuses on irreversibilities in existing processes, while the new methodology investigates the thermal efficiency from its theoretical maximum to practical values by adding irreversibilities one by one. As a result of the study presented in this paper, various measures for increasing the thermal efficiency are investigated and the corresponding improvement potential is presented. For a reference power plant, the exergy of the coal feed is calculated to be 1.08 times the lower heating value, while the actual thermal efficiency is 45.5% when irreversibilities for the combustion reaction, the heat transfer between flue gas and water/ steam, the low temperature heat losses, the steam cycle, and other factors are included. Different measures to increase the thermal efficiency of the reference plant by 0.1% points are presented. The minimum thermal efficiency penalty related to CO2 capture is 2.92-3.49% points within an air factor range of 1.0-1.4 when the CO2 is 100% recovered.

Exergy Analysis of Solid Fuel-Fired Heat and Power Plants: A Review

“…It is likely to continue as a key component of the fuel mix in the generation of power even though these plants account for over 28% of the total global emissions of carbon dioxide [45]. In order to maximize the utility of coal used in the production of energy, considerable efforts need to be made to enhance the capacity and efficiency of plants whilst simultaneously reducing their environmental impact and costs of power generation [46]. Improving both the efficiency and cost effectiveness of power plants can be achieved by reducing the thermodynamic inefficiencies associated with the system that result in a reduction of the CO 2 emission per MW of electricity generated [47].…”

Thermal behavior and microcharacterization analysis of second-oxidized coal

“…Correlation coefficient (dimensionless) O daf O content of air-dried basis (%) S daf S content of air-dried basis (%) T Thermokinetic temperature (K) T 1 First characteristic temperature, critical temperature (°C) T 2 Second characteristic temperature, active temperature (°C) T 3 Third characteristic temperature, pyrolysis temperature (°C) T 4 Fourth characteristic temperature, ignition temperature (°C) T 5 Fifth characteristic temperature, burned-out temperature (°C)…”

“…China is the largest coal-producing country [3,4], and the problem of coal spontaneous combustion [5][6][7] is gaining increasing attention. To govern the wastage of coal resources, numerous coal mines in China have begun to re-mine old coal mines and mined-out areas, which have a risk of second or multiple oxidations.…”

One feedwater heater taken out of service as a strategy to maintain full load and its effect on steam power cycle parameters and performance

“…They also indicated that there are considerable opportunities for applying energy conservation measures. Other studies also show the potential for improving the energy efficiency of this type of plants by energy conservation measures . Simulation tools and models of the thermodynamic cycles of steam power plants are useful for predicting and analyzing the cycles' performance by calculating the thermodynamic variables.…”

“…Other studies also show the potential for improving the energy efficiency of this type of plants by energy conservation measures. [6][7][8] Simulation tools and models of the thermodynamic cycles of steam power plants are useful for predicting and analyzing the cycles' performance by calculating the thermodynamic variables. Therefore, these tools and models can contribute to the running of the plant in a more effective way, since they contribute to an adequate decision making.…”