Boiler Efficiency Research Articles

Investigation of heating energy performance gap (EPG) in design and operation stages of residential buildings

The Energy Performance Gap (EPG) in buildings is a recognized phenomenon. However, its definition and underlying factors are extensive, necessitating a thorough investigation of the quantitative impact of each factor contributing to the EPG. In this research, a calibration-based approach is employed to identify and measure the contribution of these factors. Questionnaires, measurements, analyses, and calibrations are conducted on the energy performance of four residential units of an apartment block building in Iran as a case study. Subsequently, the impact rates of three key causes of the EPG, namely heating system efficiency, weather data in an EnergyPlus Weather (EPW) format file, and occupant behavior, are determined. By incorporating these causes into the model calibration process, the disparities between the design and operation stages are decreased. The study highlights the significance and quantifiable effects of accurate and measured boiler efficiency, utilizing a genuine EPW file rather than a convenient EPW file e.g., airport stations, and adopting precise and adaptable assumptions for occupant behavior modeling in bridging the EPG between the design and operation stages. There are a number of factors that impact the design stage gap, including boiler efficiency, occupant behavior, and a corrected EPW file, which contribute 43.9%, 26%, and 6.6%, respectively.

Data-driven boiler efficiency and NOx characteristic variable selection and combustion optimization

In the process of comprehensively promoting carbon peak and carbon neutralization, thermal power units need to adapt to the needs of high efficiency and cleanliness, so as to play the role of ballast stone in the transformation and upgrading of energy structure. When the traditional analysis method can not be comprehensive, real-time and efficient analysis, the introduction of data science is an option. Therefore, this paper is based on the data-driven method to model and optimize the combustion of thermal power plant boilers. The second-order characteristic variable selection algorithm is used to screen the key variables of boiler efficiency and NOx emission. Based on the multi-objective optimization algorithm of NSGA-II, the pareto frontier solution and the optimal adjustable parameter setting under different boundary conditions are determined. The example shows that the optimization scheme proposed in this paper can effectively improve the efficiency of power plant boilers and reduce NOx emissions.

Reducing boiler maintenance costs with improved materials for air-heater tubes

Corrosion of boiler air-heater tubes costs the industry several million dollars each year in repairs, reduced boiler steam output and reduced boiler efficiency. There have been many cases where the reduced boiler steam output caused by leaking air-heater tubes has reduced factory crushing rates and electricity export. Corrosion of air-heater tubes can, in many cases, be minimised by improving the gas and air flow distributions with turning vanes and ductwork redesign, but in nearly all cases, there are some tubes on the cold air side of air-heaters that are still susceptible to dew-point corrosion. Using improved tube materials in parts of boiler air-heaters that are susceptible to dew-point corrosion will significantly extend air-heater life. Available materials and coatings were reviewed, and laboratory- and factory-scale trials, metal temperature measurements, dew-point calculations and a financial analysis-based ranking of commercially available tube materials were undertaken. S-TEN 1 had a similar corrosion performance to SS304 stainless steel. Both the S-TEN 1 and SS304 stainless steel tubes had significantly greater resistance to dew-point corrosion than the carbon-steel tubes typically used in the air-heaters of Australian sugar factory boilers. The good performance of S-TEN 1 in this project is not consistent with the poor performance of S-TEN 1 (no better than carbon-steel) in earlier trials carried out by Isis Mill. The conditions experienced by the trial tubes in this project were not as severe as those experienced by the tubes in the earlier Isis Mill trials, and this appears to be the main reason for the current improved performance of the S-TEN 1 tubes. This requires further investigation.

Preheating and Humidification of the Combustion Air to Increase the Hot Water Boiler Efficiency

Energy efficiency is one of the most pressing topics now. Energy consumption in-creases as living standards rise. Efficient heat production, i.e. efficient use of energy, is achieved with optimal boiler load. The second pressing issue is the protection of the environment from pollution. The process of burning different types of fuels to produce heat or energy results in emissions that can have negative impacts on the environment. One of the solutions to improve air quality is to reduce emissions from heating plants during their production. The scientific paper considers the possibility of a preheating and humidification for combustion air system to increase the efficiency of the boiler and reduce the amount of harmful emissions in flue gases. The boiler efficiency values were calculated before and after the installation of the preheating and humidification system for the combustion air, and measurements of the flue gas analysis were carried out using a Testo 350 flue gas analyzer. Calculations and measurements for flue gas analysis have shown that the combustion air preheating and humidification system increases the boiler house efficiency by 15 % and re-duces nitrogen oxide emissions by 70 %.

Torrefaction as a Way to Remove Chlorine and Improve the Energy Properties of Plant Biomass

This study characterizes and compares the physicochemical parameters of three types of biomass: giant miscanthus, wheat straw, and white willow. An analysis of the chlorine content in the biomass was determined using a 5E-FL2350 fluorine and chlorine analyzer. In addition, energy parameters characterizing the biomass were determined, such as the content of ash and volatile matter in the tested materials, using the LECO TGA 701 thermogravimetric analyzer. The carbon and hydrogen contents were tested using the LECO TruSpec CHN elementary organic analyzer. The calorific value was determined using the LECO AC 500 isoperibolic calorimeter. Based on the research results, it was concluded that the use of the biomass torrefaction process improves its energy parameters. In the long term, this will affect the maintenance of the technical and operational efficiency of devices, installations, and power boilers compared to the co-combustion of fresh biomass. The greatest differences in results were recorded in the case of chlorine content. Carrying out detailed tests on the material immediately after its harvest showed that the content of this element was about 70% higher than in the case of torrefied raw material. The presence of chlorine in alternative fuels is responsible for the formation of chloride corrosion. Its content can be up to five times higher compared to conventional energy sources. The degree of risk of chloride corrosion of the selected elements of devices and installations is assessed on the basis of the so-called “chlorine corrosion index”.

Improving the Quality of Boiler Feed Water Based on the PDCA Cycle by Integrating Seven Tools

A boiler is an equipment that produces steam, which is used as a heater, drives a turbine to produces electricity, and so on. In order to avoid reducing efficiency boilers and save operational costs due to the formation of scale and corrosion on pipes, special treatment is required for boiler water. However, the facts in the field are that many BFW (Boiler Feed Water) products are found that do not meet the quality requirements set by the company. PT. Petrokimia Gresik is an industrial chemical company that uses boilers to assist its production process. The method used in this study is quality control analysis with the PDCA approach and Seven Tools in the form of check sheets, histograms, Pareto diagrams, control charts, fishbone diagrams, and FMEA to identify the factors causing the occurrence of defective products and see the corrective actions that must be taken based on the factors causing the occurrence of defective products. Preventive maintenance was carried out to create and schedule socialization of SOPs, collect data on spare part replacements, and check the chemical content in work unit wastewater. Based on the research results, it reveals that the PDCA approach and Seven Tools can minimize defects and succeed in reducing SO3 and PO4 parameter defects by 67,5%. The proposed improvement efforts include preventive maintenance, monitoring the consistency of SOP implementation, identifying replacement spare parts, as well as checking chemical content in work unit wastewater.

Technical-Economic Analysis of Energy Efficiency Solutions for the Industrial Steam System of a Natural Gas Processing Plant

Steam, which is primarily employed as a heat transfer medium in process plants, is one of the most widely utilized energy carriers in the industrial sector. One of the factors that affects the cost of steam is how well the condensate collection, steam supply, and return systems of industrial steam systems perform. In a case study, the steam systems of a natural gas processing plant were simulated. The amount of demineralized water loss and, consequently, the identification of various solutions to improve the system were analyzed. The whole steam system was simulated using the MEASUR software platform (v 1.2), and by placing the operational information of the steam system, it was possible to create a baseline for the system, model saving solutions, and finally, provide a technical and economic evaluation of the solutions. Due to the high loss of steam condensate in the SRU steam system (more than 3000 kg per hour), solutions to improve the energy efficiency of the SRU steam system in the form of a maximum recovery of steam condensate (replacement of defective steam traps, redesign of the low-pressure condensate collection network, and high-pressure waste condensate collection) were evaluated with two price assumptions of current energy prices and real prices (the energy saving value of one cubic meter of natural gas is equal to 13 cents). The results show that, for current prices, the investment return period will be between 11.8 and 3.8 months. Moreover, in the main steam system of the refinery (unit 9200), there are three solutions: replacing and repairing defective steam traps, installing an expansion turbine instead of a steam pressure relief valve (PRV), and other solutions (including increasing boiler efficiency, automatic control of the boiler, and energy recovery boiler blowdown) under two price assumptions, the current and real prices of natural gas and demineralized water, were evaluated, and the modeling results show that the investment return period for each of the above solutions at the current prices is 10.2, 186, and 13.3, respectively. The investment return period is based on assuming real fuel and BFW prices are equal to 2.0, 37.6, and 1.7, respectively.

Air Preheater Performance Analysis: Installation of Soft Seal Material to Improve Air Preheater Leakage

Air preheaters are used in thermal power plants to preheat combustion air before it enters the furnace by recovering and using waste heat from the flue gas that is supposed to be exhausted at the stack to reduce the work needed by the furnace to combust fuel and improve the boiler efficiency. Air preheater leakage is the bypassing of the cooler ambient air into the flue gas side, reducing the temperature needed to heat the heating elements which transfers the heat into the air side. This negatively impacts the heat transfer effectiveness of the air preheater and the overall thermal efficiency of the plant. This paper aims to review the effectiveness of the soft touch seals applied in a Ljungstrom Type Regenerative Air Preheater installed in a 455 MW (net) Coal-Fired Thermal Power Plant situated in Mauban, Quezon Province in the Philippines in reducing the air preheater leakage through calculations and analysis in compliance with the ASME Performance Test Code to ensure accuracy and repeatability.

Xylan fast pyrolysis: An experimental and modelling study of particle changes and volatiles release

Biomass char particles produced by pyrolysis may have different morphologies, which has important implications on burning mode, conversion rate and boiler efficiency. These features are difficult to address due to the complexity of biomass structure and pyrolysis reaction models.The present work reports preliminary results on the morphological changes and volatile release that solid particles of Xylan experience upon fast heating in a Drop Tube Reactor (DTR) and in a Heated Strip Reactor (HSR) in a range of temperature between 1100 and 1573 K under inert atmosphere with heating rate in the order of 103 K/s. Two different Xylan samples were chosen as representative of Hemicellulose in angiosperm biomass: xylooligosaccharide extracted from Beechwood (hardwood biomass) and from Corn Cob (herbaceous biomass).During the heatup phase, Xylan particles do not retain the original shape and morphology, neither in DTR nor in HSR experiments. In the early pyrolysis stage, Xylan particles melt and form viscous droplets. As devolatilization proceeds these droplets in the DTR evolve into highly viscous sponge-like particles with spherical shape, which swell and eventually shrink, ultimately producing highly porous spherical char particles.The experimental results are compared with the predictions obtained by the Bio-CPD Xylan pyrolysis model. The model is fairly able to calculate the pyrolysis yields in the DTR, but predicts unexpectedly low extent of metaplast formation. To explain the remarkable melting phenomena and morphological changes observed in the experiments, tuning of some CPD parameters and inclusion of mass transfer and pressure build-up within the particles might be necessary in future work.

Optimization of secondary air operation parameters of waste incineration boiler based on response surface methodology

To reduce the NOx emission concentration of waste incineration boilers and improve the thermal efficiency of incinerators, the combustion process of a 600 t/d incineration boiler was numerically investigated. First, the influences of the secondary air injection angle, velocity and temperature on the NOx concentration at the waste incineration boiler outlet and the thermal efficiency of the incinerator were analyzed through a single factor simulation test. Then, coupling optimization of key operating parameters, including the secondary air injection angle, velocity and temperature, was conducted via the response surface design method to obtain the specific functional relationships between outlet NOx concentration, incinerator thermal efficiency, front wall secondary air injection angle, rear wall secondary air velocity and secondary air temperature, as well as the optimal operating parameters for the boiler. The results showed that when the secondary air injection angle of the front wall ranges from 68°∼80° and the secondary air injection angle of the back wall is 67°, the minimum NOx concentration is 142.23 mg/m3, and the maximum thermal efficiency of the incinerator reaches 85.51 %. When the secondary air velocity at the front wall is 42 m/s and the secondary air velocity at the back wall ranges from 42 ∼ 66 m/s, the NOx concentration at the outlet is the lowest at 140.05 mg/m3, and the thermal efficiency of the incinerator is the highest at 85.63 %. When the secondary air temperature ranges from 297.16 ∼ 309.16 K, the NOx concentration at the outlet is the lowest at 155.45 mg/m3, and the thermal efficiency of the incinerator is the highest at 84.64 %. The secondary air injection angle, velocity and temperature impose significant effects on the NOx concentration at the outlet and thermal efficiency of the incinerator. The optimal parameters, as determined in the multifactor simulation test, include a 77° secondary air injection angle of the front wall, 69 m/s secondary air velocity at the back wall, and 297.15 K secondary air temperature. Under these conditions, the NOx concentration at the outlet is 134.98 mg/m3, and the thermal efficiency of the incinerator reaches 86.11 %. This study has important guiding significance for reducing pollution and improving the efficiency of waste incineration boilers.

Power Generation from Utilizing Thermal Energy of Hazardous Waste Incinerators

A large amount of thermal energy is generated from burning hazardous chemical wastes, and the temperature of the flue gases in hazardous waste incinerators reaches up to (1200 °C). The flue gases are cooled to (40°C) and are treated before emission. This thermal energy can be utilized to produce electrical power by designing a system suitable for dangerous flue gases in the future depending on the results of much research about using a proto-type small steam power plant that uses safe fuel to study and develop the electricity generation process with water tube boiler which is manufactured experimentally with theoretical development for some of its parts which are inefficient in experimental work. The studied system generates theoretically (120 kg steam /h at 8 bars) with dry wood as fuel and preheating for the air of combustion and feed water and a diesel engine of (8 hp) four-stroke with single piston converted to steam engine coupled with the electrical generator of (3 kVA). The results are compared with practical values valid in the literature about small power plants of steam capacity (0.1-1) ton/h and operating pressure up to 10 bars. Experimentally, the generated electrical power is little and sufficient to operate a small fan and lump. The current converted steam engine is better than a conventional steam engine in auto lubrication with some operational problems. The boiler efficiency is 63.28%.

Prediction Modeling of Flue Gas Control for Combustion Efficiency Optimization for Steel Mill Power Plant Boilers Based on Partial Least Squares Regression (PLSR)

The energy-intensive steel industry, which consumes substantial amounts of electricity, meets its power demands through external electricity purchases and self-generation through the operation of its own generators. This study aimed to optimize boiler combustion efficiency and increase power generation output by deriving optimal operational values for O2 and CO within the boiler flue gas using machine learning (ML) with the aim of achieving maximum boiler efficiency. This study focuses on the power-generation boilers at steel mill P in Korea. First, 361 types of operation data from power generation equipment were collected and preprocessed. Subsequently, a partial least squares regression (PLSR) algorithm was used to develop a prediction model for O2 and CO values, known as the Boiler Flue Gas Prediction Model (BFG-PM). The prediction accuracy for O2 was notably high (83.2%), whereas that for CO was lower (53.4%). Nonetheless, the model’s reliability was high because more than 90% of the predicted values were within a 10% error range. Finally, the correlation of the BFG-PM model was applied to the performance test code (PTC) 4.0 for the boiler efficiency calculations formula, deriving the optimal O2 and CO control points. Through a simulation, it was verified that the boiler efficiency was improved by controlling the combustion air. In addition, an average increase in boiler efficiency of 0.29% was confirmed by applying it directly to the generator operating on-site. The results of this study are expected to contribute to annual cost savings, with a reduction of USD 217,000 in electricity purchasing costs and USD 19,700 in greenhouse gas emissions trading expenses.

Technical-economic-environmental analysis of biomass direct and indirect co-firing in pulverized coal boiler in China

An analysis was conducted on two integrated models involving direct co-firing and pyrolysis co-firing systems within a typical 600 MW coal-fired power generation plant. The study assessed the performance of various biomass sources (sawdust, corn straw, and rice husk) using distinct co-firing ratios (5%, 10%, 15%, 20%) across technological, environmental, and economic dimensions. The findings revealed that in terms of thermal and exergy efficiency, the pyrolysis co-firing approach exhibited lower results compared to direct co-firing. Notably, among the biomasses tested, sawdust demonstrated the least impact on boiler efficiency. The CO2 emission was estimated by the Life Cycle Assessment method. The emission of the conventional boiler, along with direct and pyrolysis co-firing of corn straw at a 20% ratio, resulted in CO2 emissions of 1.075 kg, 0.954 kg, and 0.942 kg per 1kWh of electricity, respectively. The different feeding methods were also discussed, providing technically and economically rational options for coal-fired power plants. The economic feasibility of both co-firing systems was also proposed. At carbon tax rates of 410 CNY/t and 464 CNY/t for the direct co-firing and pyrolysis co-firing models respectively, the operational cost of the co-firing systems becomes comparable to that of a coal-fired boiler. However, when the by-product price exceeds 3700 CNY/t, the pyrolysis co-firing model becomes the more economically favorable option. This study primarily concentrates on investigating the real-world application and effective utilization of biomass co-firing systems within the specific framework of China's energy scenario.

Thermochemical Technologies for the Optimization of Olive Wood Biomass Energy Exploitation: A Review

The use of biomass can be a strategic way to realize a carbon-neutral energy plan, ensuring a fuel feedstock. Residual biomass arising from pruning is demonstrated to be an important energy resource in terms of quantity and quality. In the Salento peninsula, Apulia Region, in the south of Italy, a dramatic outbreak of Xylella fastidiosa has decimated olive trees since 2013, gaining a considerable amount of wood biomass. This paper, starting from the need to find a way to optimize the use of this available stock, reviews the main technologies on the utilization of olive wood for energy purposes. In particular, processes and products are here described, and an energy analysis compares lower heating value (LHV), higher heating value (HHV), mass yield, process operating conditions, and energy generated and spent by the process in order to find the most effective technology in order to optimize the energy use of olive biomass. The conclusions show the advantages and disadvantages of each technology. Pyrolysis performs well, showing the best results for both char HHV and syngas yield under different operating conditions. Gasification seems to be the most appropriate among conversion technologies to optimize olive tree pruning for energy purposes, as it can be used to produce both electrical and thermal energy. In terms of economic valorization, char is the most promising material representing a value-added product, the quality and versatility of which ranges from fuel to soil improvers and additives for the construction of supercapacitors. Conversely, its disadvantages are mainly represented by high ash content, which can slightly decrease the boiler efficiency. Finally, the amount of alkali metals can produce several problems, such as fouling, slagging, corrosion, etc., posing a challenge for combustion control and pollutant minimization.

Enhancing the Fuel Efficiency of Cogeneration Plants by Fuel Oil Afterburning in Exhaust Gas before Boilers

Cogeneration or combined heat and power (CHP) has found wide application in various industries because it very effectively meets the growing demand for electricity, steam, hot water, and also has a number of operational, environmental, economic advantages over traditional electrical and thermal systems. Experimental and theoretical investigations of the afterburning of fuel oil in the combustion engine exhaust gas at the boiler inlet were carried out in order to enhance the efficiency of cogeneration power plants; this was achieved by increasing the boiler steam capacity, resulting in reduced production of waste heat and exhaust emissions. The afterburning of fuel oil in the exhaust gas of diesel engines is possible due to a high the excess air ratio (three to four). Based on the experimental data of the low-temperature corrosion of the gas boiler condensing heat exchange surfaces, the admissible values of corrosion rate and the lowest exhaust gas temperature which provide deep exhaust gas heat utilization and high efficiency of the exhaust gas boiler were obtained. The use of WFE and afterburning fuel oil provides an increase in efficiency and power of the CPPs based on diesel engines of up to 5% due to a decrease in the exhaust gas temperature at the outlet of the EGB from 150 °C to 90 °C and waste heat, accordingly. The application of efficient environmentally friendly exhaust gas boilers with low-temperature condensing surfaces can be considered a new and prosperous trend in diesel engine exhaust gas heat utilization through the afterburning of fuel oil and in CPPs as a whole.

Air Pollutants Emission during Co-Combustion of Animal Manure and Wood Pellets in 15 kW Boiler

One of the aims of the environmental and energy policy of the European Union is to reduce the emission of air pollutants, primarily from heat and electricity production, e.g., using renewable energy sources. An example of such a fuel is agricultural biomass including animal manure, which can be used to produce energy in many ways, inter alia direct combustion. The aim of the study was to measure the concentration of NO, NOx, CO, dust and boiler efficiency during the combustion and co-combustion of wood and manure pellets. The research was conducted in the laboratory of the Poznań University of Technology using a 15 kW domestic boiler at maximum power. Manure pellets had higher moisture—9.2%, lower high heating value—17.25 MJ·kg−1, lower low heating value—16.45 MJ·kg−1, and higher ash content—11.23% than wood pellets. The average concentrations of CO, NO, NOx and dust for 100% wood pellets were 198 ± 27 mg·m−3, 129 ± 5 mg·m−3, 198 ± 8 mg·m−3 and 8.7 ± 0.5 mg·m−3, respectively. For this, the fuel boiler power was 13.6 kW (air–fuel ratio 1.48), and it was close to the maximal nominal power. Increasing the share of manure pellets in the burning mixture worsened the stability of the combustion process, and the occurrence of incomplete combustion was observed, which resulted in an increased concentration of CO and dust. Additionally, NO and NOx concentrations also increased. The average boiler power during the combustion of 100% manure pellets was 7.8 kW (air–fuel ratio 2.2), and the average concentrations of CO, NO, NOx and dust were 1548 ± 555 mg·m−3, 355 ± 53 mg·m−3, 554 ± 88 mg·m−3 and 482 ± 63 mg·m−3, respectively.

Experimental study on NOx reduction performance by ammonia solution injection into the fuel-rich zone in a 75 t/h coal-fired industrial boiler

Industrial-scale trials of NOx reduction by ammonia solution injection into the fuel-rich zone were conducted in a 75 t/h corner-tangentially coal-fired boiler, and impacts of SOFA ratio, secondary air distribution modes, and ammonia solution injector configurations on the NOx reduction performance were discussed in detail. Results indicated that the waist air distribution mode and the increase in SOFA ratio could reduce the oxygen concentration in the reduction zone, which was conducive to the NOx reduction performance of injected ammonia solution. Ammonia solution injector configurations also had a remarkable influence on NOx reduction performance. Ammonia solution injected from injectors in the top layer and at four corners yielded lower NOx emissions than that in the bottom layer and on four walls, respectively. Meanwhile, more ammonia solution injectors in service were favorable for the reducing agent mixing with flue gas, thereby enhancing the NOx reduction performance. The lowest NOx emissions of 48 mg/m3 and a corresponding maximum NOx reduction efficiency of 86.09 % were achieved under the optimized conditions, i.e., 30 % SOFA ratio, the waist air distribution mode, and all 16 ammonia solution injectors in service. However, the boiler efficiency test indicated that the retrofit led to a reduction of 0.28 % in the boiler thermal efficiency simultaneously, necessitating further studies to mitigate the adverse effects.

Efficiency Analysis using Economizer Alternative Energy in Boilers

Efficiency is one of the efforts in implementing energy conservation. Economizers are an alternative source of energy that can survive because of the potential for energy efficiency. Economizer equipment in producing electrical energy and steam produces less than 10-30% fuel needed for a conventional energy plant. The Economizer system that was assumed in this study, there was an increase in boiler efficiency with an Economizer system of 19%. As for the need for burning calories in the combustion chamber with an Economizer system of 46,868,200,68 kcal/hour compared to a system without an Economizer of 61.003.054,86 kcal/hour. Thus the fuel requirement will be less with an Economizer system of 7,735 kg/hour compared to a system without an Economizer of 10.069 kg/hour. So that the results obtained with the same ratio and type of fuel, there is a fuel efficiency of 2.334 kg/hour.

A review on methods of water softening processes for improving efficiency of bio-mass fired boiler

In order to create the steam needed for the industrial process specifically for a laundry process, bio-mass fired boilers are employed. A biomass fired boiler's production rate and efficiency is directly influenced by its effectiveness and safety. Therefore, for the industry to maintain continuous output, biomass fired boiler functioning must be at its best and efficient. The main issues that can result in reduction of efficiency and output in the bio-mass fired bioler is due to boiler tube corrosion and scale formation. The quality of the untreated water which is hardened in nature is one of the primary causes of scale formation. Therefore, to optimize the boiler function, improvement in water quality can help in preventing corrosion and the development of scale. There are various processes for treating water commonly called as water softening done by either by mixing /adding chemical agents in the water itself or by treating water from exterior. However the cost and quality of the softening technology is important for the industry. The cost of operating the boiler can be decreased by using an alternate fuel, reducing heat losses and elimination of scale formation in the boiler. This article is specifically confers about increase in efficiency of boiler by the elimination of scaling in the boiler. Various relevant research papers are studied on technologies for water treatment with advantages / disadvantages and cost effectiveness. This article focuses to review research papers which were written for the improvement of feed water to biomass fired boiler by studying various water softening techniques and suggest optimized solution to the company.

A new on-line combustion optimization approach for ultra-supercritical coal-fired boiler to improve boiler efficiency, reduce NOx emission and enhance operating safety

To take into account the economy, environment protection and operating safety of the boiler in the combustion optimization process, a new on-line combustion optimization approach for boiler is proposed. The historical combustion data collected from DCS of the coal-fired power plant is preprocessed at first. Then improved biogeography optimization-based long short-term memory neural network (IBBO-LSTM) and similarity measurement method are designed to construct the adaptive dynamic combustion model for boiler with boiler efficiency, NOx emission and the temperature of water wall as outputs respectively. After that improved non-dominated sorting genetic algorithm-Ⅱ (INSGA-Ⅱ) is designed to generate a series of boiler combustion optimization solutions under different running load offline, and improved multi-level fuzzy comprehensive evaluation (IDHGF) is designed to retain the combustion optimization solutions with higher running safety. Meanwhile, the retained optimization solutions are integrated into an optimization cases base. Thereafter, case-based reasoning based on safety enhancement mechanism (CBRSEM) is designed to achieve the online combustion optimization for boiler. Finally, to confirm the effectiveness of the combination of IBBO-LSTM, INSGA-Ⅱ, IDHGF and CBRSEM, different online optimization methods (IBBO-LSTM-INSGA-Ⅱ, IBBO-LSTM-INSGA-Ⅱ-IDHGF, IBBO-LSTM-NSGA-Ⅱ-DHGF-CBR, IBBO-LSTM-NSGA-Ⅱ-IDHGF-CBR, IBBO-LSTM-NSGA-Ⅱ-DHGF-CBRSEM, IBBO-LSTM-NSGA-Ⅱ-IDHGF-CBRSEM, IBBO-LSTM-INSGA-Ⅱ-DHGF-CBR, IBBO-LSTM-INSGA-Ⅱ-IDHGF-CBR) are adopted to optimize a given combustion case. The proposed on-line combustion optimization approach for boiler received satisfied combustion optimization results that the growing for boiler efficiency was 0.653%, and the reduced concentration for NOx emission reached 22.891 mg/m3, and the operating safety raised from 5.592 to 6.913. In conclusion, IBBO-LSTM-INSGA-Ⅱ-IDHGF-CBRSEM can online offer the combustion optimization strategy to the boiler operators to improve boiler efficiency, reduce NOx emission and enhance the running safety of boiler, so that it is suitable for online application.