Optimizing Two-Phase Flow Heat Transfer:DCS Hybrid Modeling and Automation in Coal-Fired Power Plant Boilers

In response to escalating challenges in energy conservation and emission reduction,this study delves into the complexities of heat transfer in two-phase flows and adjustments to combustion processes within coal-fired boilers.Utilizing a fusion of hybrid modeling and automation technologies,we develop soft measurement models for key combustion parameters,such as the net calorific value of coal,flue gas oxygen content,and fly ash carbon content,within theDistributedControl System(DCS).Validated with performance test data,thesemodels exhibit controlled root mean square error(RMSE)and maximum absolute error(MAXE)values,both within the range of 0.203.Integrated into their respective automatic control systems,thesemodels optimize two-phase flow heat transfer,finetune combustion conditions,and mitigate incomplete combustion.Furthermore,this paper conducts an in-depth exploration of the generationmechanismof nitrogen oxides(NOx)and low oxygen emission reduction technology in coal-fired boilers,demonstrating a substantial reduction in furnace exit NOx generation by 30%to 40%and the power supply coal consumption decreased by 1.62 g/(kW h).The research outcomes highlight the model’s rapid responsiveness,enabling prompt reflection of transient variations in various economic indicator parameters.This provides a more effective means for real-time monitoring of crucial variables in coal-fired boilers and facilitates timely combustion adjustments,underscoring notable achievements in boiler combustion.The research not only provides valuable and practical insights into the intricacies of two-phase flow heat transfer and heat exchange but also establishes a pioneering methodology for tackling industry challenges.

Optimal dynamic dispatch of surplus gas among buffer boilers in steel plant

As valuable energy in iron-and steel-making process,by-product gas is widely used in heating and technical processes in steel plant.After being used according to the technical requirements,the surplus by-product gas is usually used for buffer boilers to produce steam.With the rapid development of energy conservation technology and energy consumption level,surplus gas in steel plant continues to get larger.Therefore,it is significant to organize surplus gas among buffer boilers.A dynamic programming model of that issue was established in this work,considering the ramp rate constraint of boilers and the influences of setting gasholders.Then a case study was done.It is shown that dynamic programming dispatch gets more steam generation and less specific gas consumption compared with current proportionate dispatch depending on nominal capacities of boilers.The ignored boiler ramp rate constraint was considered and its contribution to the result validity was pointed out.Finally,the significance of setting gasholders was studied.

Corrosion of Different Materials in Combustion Chamber of Yellow Phosphorus Tail Gas in Industrial Boiler

The corrosion of materials in combustion chamber of yellow phosphor tall gas was investrgated. The results reveal that the corrosion behavior is different for different materials under actual work conditions.

Comprehensive Solution to Flue Gas Desulfurization and Denitration of Circulating Fluidized Bed Boiler

With the advantages of high combustion efficiency, wide fuel flexibility and low concentrations of discharged pollutants, circulating fluid- ized bed （CFB） boiler has been widely used in recent years. However, in order to meet the requirement of new emission standard, it＇s necessary to add flue gas desulfurization and denitration devices. In this paper, the choice of flue gas purification processes for CFB boiler has been discussed firstly, and then the economy and rationality of the SNCR ＋ CFB-FGD ＋ COA comprehensive solution to flue gas desulfurization and denitration have been analyzed.

Retrofit of 350-MW Supercritical Boiler Based on the Analysis on Exhaust Gas Temperature

Since the first batch of 350-MW supercritical utility boilers was put into operation, the exhaust flue gas temperature of the boilers has always been higher than the designed value. The main reason is that the heat absorbed by the air heater is not sufficient. In Huaneng Dongfang Power Plant, the exhaust flue gas temperature is lowered through modifications to the economizer and the air heater. The experimental results reveal that every year, each boiler could save 3 850 tons of standard coal and reduce 85 tons of SO2 and 9 000 tons of CO2 respectively after retrofit.

Heating and Cooling Hybrid System with Gas Mixture Sourced Heat Pump and Heating Boiler

Preliminary investigation shows that air sourced type heat pumps by energy efficiency are competitive with gas boilers having 93% of coefficient of performance （COP） if heat pumps are used in climatic zones, having outside air temperature higher than （-3 ℃ to -5 ℃）. But, in such conditions the heat pump＇s evaporator is covered by ice crust, which cuts off the flow of outside air-heat source through the evaporator of heat pump. For avoiding stating problems it is recommended to use as heat source a mixture of waste warm gases. In this article a high efficiency heating-cooling system is developed, consisting of warm gases mixture sourced heat pump, heating boiler operating simultaneously with heat pump and solar air heater. The heating demand of the served house is shared between boiler and heat pump. Instead of outside air the warm gases mixture enters into evaporator of heat pump. A new construction of heat exchanger was developed. The article presents the structure and principle of operation, as well as the method for optimization and design of suggested system. Analysis proved high energy efficiency and cost effectiveness of the new system.

Influence of Recirculated Flue Gas Distribution on Combustion and NOx Formation Characteristics in S-CO_(2) Coal-fired Boiler

Supercritical carbon dioxide(S-CO_(2))Brayton power cycle power generation technology,has attracted more and more scholars'attention in recent years because of its advantages of high efficiency and flexibility.Compared with conventional steam boilers,S-CO_(2) has different heat transfer characteristics,it is easy to cause the temperature of the cooling wall of the boiler to rise,which leads to higher combustion gas temperature in the furnace,higher NOX generation concentration.The adoption of flue gas recirculation has a significance impact on the combustion process of pulverized coal in the boiler,and it is the most effective ways to reduce the emission of NOX and the combustion temperature in the boiler.This paper takes 1000MW S-CO_(2) T-type coal-fired boiler as the research target to investigate the combustion and NOX generation characteristics of S-CO_(2) coal-fired boilers under flue gas recirculation condition,the influence of recirculated flue gas distribution along the furnace height on the characteristics of NOX formation and the combustion of pulverized coal.The results show that the recirculated flue gas distribution has the great impact on the concentration of NOX at the boiler outlet.When the bottom recirculation flue gas rate is gradually increased,the average temperature of the lower boiler decreases and the average temperature of the upper boiler increases slightly;The concentration of NOx at the furnace outlet increases.

Modeling and Simulation Study on Reverse Swirl of Secondary Air in Large Tangentially Fired Boiler

Based on the porosity method and the improved non uniform QUICK scheme, this paper describes a three dimensional computer simulation to predict the flow characteristics in a tangentially fired boiler. The model is applied to a 600?MW boiler modeling under different operating conditions of reverse swirl of secondary air. The numerical results achieve reasonable agreement with experimental data. The calculated results of flow field, the pressure distribution, the relative diameter of tangential circle, angular momentum flux in furnace and the velocity distribution index in horizontal gas pass are analyzed in detail. And then the effects of the reverse swirl of secondary air on flue gas imbalance are discussed. Finally a reasonable operating condition of the reverse swirl of secondary air is presented.

Deep Desulphurization and DeNO_X in Circulating Fluidized Bed Boiler

With the revision of emission standards, deep desulphurization and DeNO X is needed in circulating fluidized bed (CFB) boilers. The operation of the first set of 300-MW CFB boiler plus limestone/gypsum wet flue gas desulphurization (FGD) system in the world shows that deep desulphurization and DeNO X of CFB boilers has higher SO2 removal efficiency at a lower Ca/S ratio compared with traditional inner desulphurization mode. It can meet the increasingly rigid emission standards, and is suitable for more fuels. Deep desulphurization and DeNO X can also achieve a highly-efficient high-temperature CFB boiler that can not only achieve inner desulphurization and low NO X emission, but benefits low-grade, high sulfur content fuels as well. Research of deep desulphurization and DeNO X will be a developing direction for CFB boilers.

Modelling and analyzing the impact of hydrogen enriched natural gas on domestic gas boilers in a decarbonization perspective

Decarbonization of energy economy is nowadays a topical theme,and several pathways are under discussion.Gaseous fuels have a fundamental role for this transition,and the production of low carbon-impact fuels is necessary to deal with this challenge.The generation of renewable hydrogen is a trusted solution since this energy vector can be promptly produced from electricity and injected into the existing natural gas infrastructure,granting storage capacity and easy transportation.This scenario will lead,in the near future,to hydrogen enrichment of natural gas,whose impact on the infrastructures is being actively studied.The effect on end-user devices such as domestic gas boilers,instead,is still little analyzed and tested,but is fundamental to be assessed.The aim of this research is to generate knowledge on the effect of hydrogen enrichment on the widely used premixed boilers:the investigations include pollutant emissions,efficiency,flashback and explosion hazard,control system and materials selection.A model for calculating several parameters related to combustion of hydrogen enriched natural gas is presented.Guidelines for the design of new components are provided,and an insight is given on the maximum hydrogen blending bearable by the current boilers.

WHR （Waste Heat Technology） Method in Tri-generation Model

This paper is focused on description of cool production in using WHR （Waste Heat Technology） Technology-a new method of centralized production of heat by using the waste heat from generated exhaust gas, which has been in 2009 developed and operated by companies HELORO s.r.o, and COMTHERM s.r.o.

Pressure Analysis of the Initial Process of Diffusion Combustion Surge in a 350 kW Gas Boiler

In order to meet the increasingly stringent requirements for nitrogen oxides(NOx)emissions from gas boilers,flue gas recirculation(FGR)technology is commonly used to achieve ultra-low NOx emissions.However,under some ultra-low NOx combustion conditions with FGR,a surge phenomenon occurs in the boiler,which causes a flameout and should be avoided.In this study,the diffusion combustion surge of gas boiler with a rated power of 350 k W and equipped with FGR device was investigated.Pressure characteristic analysis results of the initial process of combustion surge showed that the high-frequency component of pressure is closely related to combustion stability and its change can provide reference for the occurrence of surge.Besides,the initial process of surge was analyzed by wavelet packet entropy method.Results indicated that the wavelet packet entropy of pressure signals could effectively reflect the stability of combustion in the furnace,and it could also be used to study the occurrence of surge.

Transforming Waste Heat into“Renewable Heat”

Introduction:The current worldwide electric power&heat&cool production has a negative impact on the environment by emissions and enormous leaks of low-potential waste heat.Transformation of unused industrial low power heat into“renewable heat”useful to enhance the efficiency of the system is essential and actual innovation in the field of worldwide environmental protection.By introducing and defining the terminology of low-potential,“renewable”,“green heat”has created a new,parallel category of research in the energy sector.Traditional co-generation systems produce heat for space heating and hot water and generate electricity.Moving to tri-generation allows growing demand for air conditioning for homes,offices and commercial spaces such as server rooms and switchboards to be met simultaneously or on a seasonal basis.Tri-generation,or combined cooling,heat and power,is the process by which some of the heat produced by a co-generation plant is used to generate chilled water for air conditioning or refrigeration.Usually an absorption chiller is linked to the plant to provide this functionality.The technical solution is related to the new efficient manner and system of simultaneous generation of heat/cold from multiple heat sources,which has not yet been known,but in practice required.New system also enables advantageous utilization of solar power in supporting of the cooling output.The innovative system can be operated also within the existing central heating distribution systems.

Experimental and thermal stress investigation on side wall deformation at the pendent convective pass in a utility boiler

An experimental investigation is performed on side wall deformation at the pendant convective pass (PCP) in a 300 MW and a 600 MW utility boiler. The temperature distributions are measured on the side wall areas of the water-cooled wall, the PCP and the horizontal convective pass (HCP) in the two utility boilers. These experiments show that there are great temperature differences in the side wall areas during the startup process in both utility boilers. These temperature differences can reach 80～150 °C with the side wall temperature in the PCP area higher than those in the water-cooled wall and the HCP. The highest temperature in the PCP is close to the flue gas side temperature at the same position in the horizontal flue gas pass. Thermal stress analyses are conducted in the side wall areas in the water-cooled wall, the PCP and the HCP with the software ANSYS. The results show that, at great temperature differences, the PCP side wall undergoes negative thermal stresses that exceed the yield strength causing deformation in the PCP side wall.

Heating energy performance and part load ratio characteristics of boiler staging in an office building

Commercial buildings account for significant portions of the total building energy in South Korea and thus a variety of research on the boiler operation related to heating energy in office buildings has been carried out thus far. However, most of the researches have been conducted on the boiler itself, i.e., the part load ratio characteristics and the corresponding gas energy consumption patterns are not analyzed in the existing studies. In this study, the part load ratio and the operating characteristics of gas boiler have been analyzed within an office building equipped with the conventional variable air volume system. In addition, the gas consumption among different boiler staging schemes has been comparatively analyzed. As a result, significant portions of total operating hours, heating load and energy consumption has been found to be in a part load ratio range of 0 through 40% and thus energy consumption is significantly affected by boiler efficiency at low part load conditions. This suggests that boiler operation at the part load is an important factor in commercial buildings. In addition, utilizing sequential boiler staging scheme can save a gas usage of about 7%. For annual heating energy saving, applying the sequential control boiler with a 3:7 proportion staging is considered to be the optimal control algorithm for maximum efficiency of boilers.

Application of Response Surface Methodology for Analysis of Reheat Steam Temperatures in a Double Reheat Coal-Fired Boiler

For the improvement of reheat steam quality and performance of double reheat coal-fired utility boiler under wide load operation, a variety of temperature regulation ways were utilized to adjust the energy distribution between different heating surfaces. In this paper, thermodynamic calculation based on the fundamental heat transfer theory was conducted for the analysis of temperature regulation strategy effects to steam temperature. In consideration of the specific overlapping heating surface arrangement, the compartment model was adopted to solve this problem. Response surface methodology(RSM) was used to analysis the effect of each temperature regulating variables on the steam temperature and boiler efficiency;then the polynomial model was fitted to predict the primary and secondary steam temperature simultaneously. Results showed that the flue gas recirculation rate has a relatively significant influence on the steam temperature, the maximum temperature deviation between fitting value and calculation value is 3.85℃ in 75% THA;the quadratic model can well predict the steam temperature under different operation conditions in wide load change. The variation of flue gas baffle has a significant influence on the boiler efficiency, compared to the flue gas recirculation and angle of burner oscillation. The influence of various factors on the reheat steam temperature is flue gas baffle > flue gas recirculation > angle of burner oscillation.

Modelling of the Whole Process of a University Campus CHP Power Plant and Dynamic Performance Study

Combined heat and power （CHP） refers to a process/system designed to utilize the waste or residual heat from a power generation process. Thus, a CHP plant can produce both electricity and heat. The nature of such a combination makes the process more complex than any single power generation process or boiler heating system. The paper focuses on modelling study and analysis of energy efficiency of the University of Warwick micro-CHP power plant. In this CHP modelling study, a gas turbine module is built to provide driving power and methane is used as fuel gas. Heat recovery system and auxiliary boiler modules are developed for thermal power generation. All the sub-systems are validated by comparing the simulation results with the operating data collected from the CHP plant. The dynamic performance of the key CHP process outputs is studied with respect to the variation of the input syngas stream, including electricity generation, thermal power output and water output temperature. Simplified controllers are also applied to the gas engineheat recovery subsystem and auxiliary boiler. Simulation results with/without feedback control are both analyzed. The study has highlighted the key factors which influence the plant performance and suggested the strategy for potential energy efficiency improvement.