Evaporative Cooling Applied in Thermal Power Plants:A Review of the State-ofthe-Art and Typical Case Studies

A review is conducted about the application of the evaporative cooling technology in thermal power plants.Different case studies are considered,namely,evaporative air conditioners,evaporative cooling in direct air-cooled systems,gas turbine inlet cooling,wet cooling towers,and hybrid cooling towers with a crosswind effect.Some effort is provided to describe the advantages related to direct evaporative cooling when it is applied in thermal power plants and illustrate the research gaps,which have not been filled yet.In particular,typical case studies are intentionally used to compare the cooling performances when direct evaporative cooling is implemented in different types of cooling towers,including the natural draft wet cooling tower(NDWCT)and the pre-cooled natural draft dry cooling tower(NDDCT).It is shown that the NDWCT provides the best cooling performance in terms of power station cooling,followed by the pre-cooled NDDCT,and the NDDCT;moreover,the evaporative pre-cooling is able to enhance the cooling performance of NDDCT.Besides,on a yearly basis,better NDDCT cooling performances can be obtained by means of a spray-based pre-cooling approach with respect to wet media pre-cooling.Therefore,the use of nozzle spray is suggested for improvement in the performance of indirect/direct air-cooling systems with controlled water consumption.

Increasing the Efficiency and Level of Environmental Safety of Pro-Environmental City Heat Supply Technologies by Low Power Nuclear Plants

In connection with the current prospect of decarbonization of coal energy through the use of small nuclear power plants (SNPPs) at existing TPPs as heat sources for heat supply to municipal heating networks, there is a technological need to improve heat supply schemes to increase their environmental friendliness and efficiency. The paper proves the feasibility of using the heat-feeding mode of ASHPs for urban heat supply by heating the network water with steam taken from the turbine. The ratio of electric and thermal power of a “nuclear” combined heat and power plant is given. The advantage of using a heat pump, which provides twice as much electrical power with the same heat output, is established. Taking into account that heat in these modes is supplied with different potential, the energy efficiency was used to compare these options. To increase the heat supply capacity, a scheme with the use of a high-pressure heater in the backpressure mode and with the heating of network water with hot steam was proposed. Heat supply from ASHPs is efficient and environmentally friendly even in the case of significant remoteness of heat consumers.

Output power analyses for the thermodynamic cycles of thermal power plants

Thermal power plant is one of the important thermodynamic devices, which is very common in all kinds of power generation systems. In this paper, we use a new concept, entransy loss, as well as exergy destruction, to analyze the single reheating Rankine cycle unit and the single stage steam extraction regenerative Rankine cycle unit in power plants. This is the first time that the concept of entransy loss is applied to the analysis of the power plant Rankine cycles with reheating and steam extraction regeneration. In order to obtain the maximum output power, the operating conditions under variant vapor mass flow rates are optimized numerically, as well as the combustion temperatures and the off-design flow rates of the flue gas. The relationship between the output power and the exergy destruction rate and that between the output power and the entransy loss rate are discussed. It is found that both the minimum exergy destruction rate and the maximum entransy loss rate lead to the maximum output power when the combustion temperature and heat capacity flow rate of the flue gas are prescribed. Unlike the minimum exergy destruction rate, the maximum entransy loss rate is related to the maximum output power when the highest temperature and heat capacity flow rate of the flue gas are not prescribed.

Flow Characteristics Diagnosis and Optimization for Dust Collectors Inflow Duct in Thermal Power Plants

火电厂烟风道用于输送烟气、冷风等介质，其设计优化水平不但影响火电厂烟风系统阻力的大小，而且影响与烟风道直接相连的各个设备的运行状态。某600MW机组除尘器前烟道设计不合理，存在磨损严重、进入除尘器烟气分配不均等问题，文中采用标准缸￡模型，利用Fluent求解器对该部分烟道的流场进行数值计算，诊断分析其存在的主要问题，提出的3个改造方案均可使烟道阻力大幅度下降、烟道磨损减轻、进入除尘器烟气分配均匀。同时，研究了缓转半径及烟气流速对该段烟道阻力和烟气分配的影响情况，计算结果表明该段烟道缓转半径宜选在0．875以上，烟气流速对该段烟道的性能基本没有影响。

A Feature Weighted Mixed Naive Bayes Model for Monitoring Anomalies in the Fan System of a Thermal Power Plant

With the increasing intelligence and integration,a great number of two-valued variables(generally stored in the form of 0 or 1)often exist in large-scale industrial processes.However,these variables cannot be effectively handled by traditional monitoring methods such as linear discriminant analysis(LDA),principal component analysis(PCA)and partial least square(PLS)analysis.Recently,a mixed hidden naive Bayesian model(MHNBM)is developed for the first time to utilize both two-valued and continuous variables for abnormality monitoring.Although the MHNBM is effective,it still has some shortcomings that need to be improved.For the MHNBM,the variables with greater correlation to other variables have greater weights,which can not guarantee greater weights are assigned to the more discriminating variables.In addition,the conditional P(x j|x j′,y=k)probability must be computed based on historical data.When the training data is scarce,the conditional probability between continuous variables tends to be uniformly distributed,which affects the performance of MHNBM.Here a novel feature weighted mixed naive Bayes model(FWMNBM)is developed to overcome the above shortcomings.For the FWMNBM,the variables that are more correlated to the class have greater weights,which makes the more discriminating variables contribute more to the model.At the same time,FWMNBM does not have to calculate the conditional probability between variables,thus it is less restricted by the number of training data samples.Compared with the MHNBM,the FWMNBM has better performance,and its effectiveness is validated through numerical cases of a simulation example and a practical case of the Zhoushan thermal power plant(ZTPP),China.

Independent component analysis approach for fault diagnosis of condenser system in thermal power plant

A statistical signal processing technique was proposed and verified as independent component analysis(ICA) for fault detection and diagnosis of industrial systems without exact and detailed model.Actually,the aim is to utilize system as a black box.The system studied is condenser system of one of MAPNA's power plants.At first,principal component analysis(PCA) approach was applied to reduce the dimensionality of the real acquired data set and to identify the essential and useful ones.Then,the fault sources were diagnosed by ICA technique.The results show that ICA approach is valid and effective for faults detection and diagnosis even in noisy states,and it can distinguish main factors of abnormality among many diverse parts of a power plant's condenser system.This selectivity problem is left unsolved in many plants,because the main factors often become unnoticed by fault expansion through other parts of the plants.

Discharge water temperature assessment of thermal power plantusing remote sensing techniques

Thermal power plants are generally constructed near to sea coast to meet their requirement of coolingwater. The warm water discharge from the thermal power plant is one of the major environmentalconcerns in view of the thermal pollution in the sea water. The temperature limit for the warm waterdischarge from the thermal power plant has to be monitored and controlled. Coastal Gujarat PowerLimited (CGPL) operates (24×7) at an “once-through system” based sea water circulation for powergeneration. The used sea water is then discharged into the sea through an outlet channel. As per environmental norms, the discharge water temperature needs to be maintained below the stipulated “delta”rise (+7 ℃) with respect to ambient sea surface temperature at the inlet. We demonstrate the applicability of thermal remote sensing data in understanding the seasonal and temporal variations of thetemperature difference between the discharge water and the ambient sea water. We used thermal banddata from Landsat-8 satellite imagery to map water surface temperature and create temperature profilesalong the intake and outflow channels (till the sea), to understand the variation of temperature andestimate the “DT” between intake point and various observation points along the outflow. This analysiswas carried out for all 11 months (except June) of the year 2018 to correlate temperature variations withseasonal changes. Tidal conditions during the time of data acquisition were also considered to accountfor the effect of tides on DT. The result shows that the average temperature rise between intake andoutflow are maintained at ~3 ℃ across all the months of 2018, with minor variations in the months ofJuly and August. Further, average temperature drop from outflow to cooling channel (before diaphragm)is seen to be ~2 ℃ across all the months with similar seasonal fluctuations.

FGD Capacity Prediction of Thermal Power Plants in China

Through analyzing the proportion of SO2 emission from thermal power plants in the nationwide SO2 emis- sion in USA, Japan etc. developed countries, and the developmental course of thermal power installed capacity and the FGD capacity in USA, the FGD capacity of thermal power plants in China is forecasted from two angles. One is to predict FGD capacity in accordance with the policy in force in China. The other is to predict FGD capacity based upon the emission right trading policy. As compared, it is held that FGD equipment should be mainly installed on the large size units burning high sulfur coal according to the emission right trading policy. Such a method of work not only can economize large amount of investments and operation costs, but also can realize the same environmental effect.

The Optimal Steam Pressure of Thermal Power Plant in a Given Load

As the large change of the grid load, many large capacity units of our country had to change the load in order to meet the gird need. When a thermal power plant receives a given load instruction from the grid, it is necessary to set an optimal steam pressure to maintain the high efficiency of the plant. In the past optimization methods, during the process of calculation, the output of the turbine often changed, it was hard to maintain the output constant. Therefore, in combination with the theory of variable condition of turbine, calculation of governing stage and the matrix equation of thermal power system, an optimization method were put forward and an optimal solution was got in a given load.

Korean Atmospheric Environmental Impact Assessment for Thermal Power Plant

Korea has adopted Environmental Impact Assessment (hereafter “EIA”) system for more than 3 decades. There are 74 big projects subject to EIA according to (Environmental Impact Assessment Law (No. 10892). For thermal power plant of which output is more than 10 MW, EIA must be done by proponents. To assess impact on atmospheric environment, proponents utilize air dispersion models and to minimize the adverse impact on air quality, state-of-the-art add-on control technology is applied.

FGD Franchising Pilot Project of Thermal Power Plants

According to the national policy on enhancing environmental protection,the five major power generation companies are required to carry out flue gas desulphurization(FGD) franchising pilot project in thermal power plants.This paper introduces the development of this pilot project,including the foundation,purpose,objects,demands and procedures.It also discusses some main problems encountered during implementation,involving the understanding,legislation,financing,taxation,pricing and management of franchise.At the end,it puts forward some suggestions and countermeasures with regard to laws,regulations,taxation policy and electricity pricing policy.

Modeling the Dispersion and Atmospheric Mitigation of Pollutants in the Dibamba-Douala Thermal Power Plant

This work simulates the dispersion and atmospheric attenuation of pollutants from the Dibamba-Douala thermal power plant. The objective of this research is to study the dispersion of air pollutants and mitigate the impact of pollutants on the populations living around the power plant. The methodology used is as follows: the Gaussian model is used for the representation of the dispersion in the form of a plume, the finite difference method for digital resolution. Finally, dispersion charts are constructed which allow the heights of the chimneys to be fixed for which the concentrations of pollutants discharged comply with ambient air quality standards. The results obtained using the simulation made in the MATLAB software version 2016 show that, for a wind regime of 1.5 m/s;we have a predicted distance of 150 m at which the concentration is canceled out. Then, for the wind speed of 2 m/s;we had a predicted distance of 125 m and finally for a wind speed of 2.5 m/s;we observed the 120 m distance at which the concentration is canceled. In addition, for the same wind regimes, the attenuation of pollutants at ground level is obtained for a height of 60 m.

Effects of NaOH Concentrations on Properties of the Thermal Power Plant Ashes-Bricks by Alkaline Activation

The use of the thermal power plant ashes including fly ash(FA) and bottom ash(BA) for producing unfired building bricks(UBB) using sodium hydroxide(NaOH) solution as an alkaline activator was investigated. A low applied forming pressure of 0.5 MPa and various NaOH concentrations of 5, 8, 10, and 12 M were used for the preparation of brick samples with different solution-to-binder(S/B) ratios of 0.35 and 0.40. The bricks were subjected to various test programs with reflecting the effect of both NaOH concentrations and S/B ratios on the brick’s properties. The compressive strength, unit weight, ultrasonic pulse velocity, and thermal conductivity of bricks increased with increasing NaOH concentration, whereas the contrary trend was found with increasing S/B ratio. Also, the water absorption of bricks was observed to reduce with increasing NaOH concentration and decreasing S/B ratio. As the results, the combined utilization of both low forming pressure and coal power plant ashes can produce the UBBs with low unit weight, low heat conductivity, and acceptable strength and water absorption rate as stipulated by TCVN 6477-2016. Furthermore, the outcomes of chemical analysis and microstructure observation also demonstrate that a high concentration of the Na OH promoted the geopolymerization process. Notably, the use of NaOH solution of either 10 M or above is recommended for the production of UBBs, which are classified as grade M5.0 or higher.

500 MW Unit Simulator for Panshan Thermal Power Plant Passed Acceptance

After a thorough demonstration in Panshan Thermal Power Plant, the 500 MW super critical pressure unit simulator developed by the Simulation & Control Institute under the North China University of Electric Power was accepted by experts from the North China Electric Power Group Company on 3rd August 1996.

Difficulties and Solutions for Desulphurization of Thermal Power Plants in China

As coal is the most important primary energy in China, SO2 , the main pollutant of coal-fired power plantsseriously pollutes the environment in the course of energy utilization and conversion. Flue gas desulphurization is inevitable in China, however, it is rather difficult to reach the stipulated standards without any compulsory administrative measures of the government. What are the exact difficulties and solutions for the desulphurization in power plants?