Boilers In China Research Articles

Condition Monitoring of Limestone and Soft Sensing Model of SO2 Emissions in a Circulating Fluidized Bed Boiler

Soft sensing models of the desulfurization process are developed in a circulating fluidized bed (CFB) boiler that can capture sulfur dioxide (SO2) with the limestone sorbent in the furnace. First, calcining utilization of CaCO3 and sulfating utilization of CaO are proposed by mechanism analysis of the theoretical air and flue gas, and the online prediction method is achieved by using an adaptive-tree-structure-based fuzzy inference system (ATSFIS). Second, condition monitoring models of active CaCO3, active CaO, and soft sensing model of SO2 emissions are studied by using the experimental data of a CFB boiler in China, which can monitor the storage and condition of the limestone in the furnace and predict SO2 emissions. Finally, a nonlinear proportional–integral–derivative (PID) control system based on the above models is designed to control the feed rate of limestone for the reduction of SO2 emissions. The simulation results show that the soft sensing models are consistent with the mechanism test results...

Applicability of the ASME Exemption Curve for Chinese Pressure Vessel Steel Q345R

Q345R steel is the most commonly used material in fabrication of the pressure vessels and boilers in China, due to its excellent properties. In 2010, ASME code case 2642 accepted Q345R steel for use in construction of pressure vessels. The code case specified impact test exemption curve A for the impact test requirements for Q345R. However, this provision severely limits the application of this material at low temperature, since most of the minimum design metal temperature (MDMT) of curve A is above the freezing point. In this paper, a series of tests (such as uniaxial tensile test, impact test, and fracture toughness test) were carried out at low temperature to investigate the mechanical properties of Q345R steel plates with thickness of 36–80 mm. This study of low temperature usage of Q345R steel was conducted using the fracture mechanics assessment procedure of API 579-1/ASME FFS-1. The fracture toughness is given by master curve (MC) method in the transition regime. The results show that Q345R can be used at lower temperature and that classifying Q345R steel into curve D is appropriate.

Analysis on high-temperature corrosion characteristic of 0Cr18Ni9NbCu3BN steel

The high-temperature corrosion characteristic of 0Cr18Ni9NbCu3BN steel was analysed in this paper. The samples were selected from a super-heater with service time of 34 696 h in an ultra-supercritical boiler in China. Scanning electron microscopy, energy spectrum analysis and energy dispersive X-ray spectroscopy were adopted to analyse the element constitute, morphology and phase structure of the corrosion scale. The results indicated that corrosion scale can be divided into three layers, and the middle layer of corrosion scale is enriched with Cr. The Cr-rich layer could not set an efficient barrier to prevent sulphur from penetrating to the matrix. It actually can prevent O from penetrating to metal base effectively. The main corrosion forms are high-temperature oxidation and sulphidation, while the sulphidation rate was greater than the oxidation rate. The sulphidation is the major type of corrosion attack. Oxidation and sulphidation interactively cause the corrosion progress consistently.

Discussion on Approach to Renovation of Industrial Coal-Fired Boilers in China

This paper analyzed the present status of industrial coal-fired boilers and relevant policies and standard requirements, and had in-depth discussion on alternative ways of industrial coal-fired boilers, pollution control and management optimization for energy saving. It pointed out that options for elimination and replacement of industrial coal-fired boilers are new energy high efficiency boilers, industrial waste heat utilization, heat pump, new energy and renewable energy. For pollutant control, it provided feasible technologies on controlling dust, sulfur dioxide and nitrogen oxides respectively. Energy conservation measures including evenly hierarchical coal feeding technology, low nitrogen high efficiency combustion technology and etc. are stated as well. It ends up with brief analysis of relevant necessary supporting measures for the whole renovation scheme.

Development and Application of A Coal Combustion Life Cycle On-line Monitoring System

In China, coal quality fluctuates and deviates greatly from the original design in many large-scale coal-fired power plants. To maintain a secure level and combustion efficiency, a “coal combustion life cycle online monitoring system” (CLMS) has been developed and installed on a 215MW boiler in China. Ten temperature detectors have been installed at the heights of three-layer burners along the furnace. To improve the accuracy of measuring unburnt carbon in fly ash, an adjustable microwave test facility was established. An on-line measurement device for unburnt carbon in ash has been newly developed and attached to the convection flue gas pass. To optimize combustion processes, a real-time neural network prediction model for coal calorific value has been developed. By calculating and analyzing the data in computer workstations, safety evaluation of burner ignition, economic analysis and energy loss analysis can be obtained in real time. As for fluctuation in coal quality, application of the system has improved boiler efficiency more than 1.0%, and reduced NOx by ~10–15%.

An Imprint for the Latest Technolgy

This article discusses how Harbin Boiler Co. Ltd (HBC) has incorporated the ASME Boiler and Pressure Vessel Code to ensure that the research, manufacturing, and servicing behind its products are in line with the international standard. HBC got to know ASME Codes in the early 1980s. In 1987, HBC became the first manufacturer of utility boilers in China to obtain ASME Authorization Certificates and Code stamps S (power boilers), U (pressure vessels), and Ш (alternative rules for pressure vessels). HBC obtained the National Board Authorization Certificate and Code stamp R (repair and alteration of boilers) in 1996. In 2004, HBC completed manufacturing the first product project with the U stamp – 24 oil tanks and gas tanks for the Three Gorges Zuoan Power Plant. During the course of obtaining ASME certificates and Code stamps, HBC also enhanced its design capability and manufacturing level, promoted its technology and management levels, further improved its quality and management system, and greatly strengthened its comprehensive competitiveness in the market.

A non-equal fragment model of a water-wall in a supercritical boiler

In this paper, a non-equal fragment model is developed to investigate the heat and mass transfer of a water-wall in a supercritical boiler. In this model, the water-wall has been divided into several fragments and has been coupled with a boiler furnace model, which is divided into seven compartments based on the position of the burners. The model was validated using data from a 600 MW supercritical boiler in China. The agreement between the calculated response and the operation data is satisfactory. Compared with conventional methods, the non-equal fragment model provides a more reliable heat distribution and a more adaptive response under different burners' conditions. The steam thermodynamic distributions along the vertical direction have been meticulously calculated and will be helpful for the metal temperature prediction, performance estimation and energy-saving potential analysis.

A New SO<sub>X</sub> Simulation Model of Coal Combustion

It is very important to study the emission of pollutant from a coal combustion device, and it is a best way to adopt numerical simulation for such a study. By using a mathematical model with a post-processing method and based on combustion simulation, this paper calculates the SOx distribution in a power plant boiler furnace. For the formation of SOx, a conventional chemical reaction model is adopted, and according to the principles of reaction dynamics, a model for the SOx formation is also put forward. It is the first time for preceding the calculation and on-site testing an 800MW-unit boiler in China. The test and calculation results show that the model is reasonable, and such a study will be valuable as a reference to the boiler design and its clean operation.

Comparison and Analysis on Flue Gas Denitrification Technology in Coal Fired Boiler Retrofit

The widely used technologies of Selective Catalytic Reduction (SCR), Non-selective Catalytic Reduction (SNCR) and hybrid SNCR-SCR for coal-fired boiler in China are reviewed. The technical characteristics of different processes and transformation methods are compared. Analysis is made about the advantages of each technology and the major problems in the retrofitting. The proposal for the corresponding problems is presented. Reference is provided for coal-fired boiler denitrification transformation in China.

Theoretical Analysis about Boiler Retrofit to Burn CWS

In this paper, the test fuel is organic waste water slurry, which can be mixed to by organic waste water and pulverized coal. The organic waste water comes from chamfor Papermaking Company of Jiangsu province. Theoretically, we introduce the structure retrofit of the 75t/h Circulating Fluidized Bed Boiler of chamfor Papermaking Company in detail. It is the first industrial application that coal organic waste water as fuel to burn in circulating fluidized bed boiler in China. To get more reasonable boiler structure transformation scheme and more accurate data, we need carry lots of experiments.

Effects of the Updated National Emission Regulation in China on Circulating Fluidized Bed Boilers and the Solutions To Meet Them

The advantage of circulating fluidized bed (CFB) boilers in China is their ability to utilize low rank coal with low cost emission control. However, the new National Emission Regulation (NER) issued in early 2012 brings much more stringent challenges on the CFB industries, which also causes much attention from other countries. Based on the principle of a CFB boiler and previous operating experience, it is possible for the CFB boilers to meet the new NER and maintain the advantage of low cost emission control, while, more influences should be considered in their design and operation. To meet the requirement of the new NER, the fly ash collector should adopt a bag house or combination of electrostatic precipitator and bag filter to ensure dust emissions of less than 30 mg · Nm(-3). For SO2 emission control, the bed temperature should be strictly lower than 900 °C to maintain high reactivity and pores. The limestone particle size distribution should be ranged within a special scope to optimize the residence time and gas-solid reaction. At the same time, the injecting point should be optimized to ensure fast contact of lime with oxygen. In such conditions, the desulfurization efficiency could be increased more than 90%. For lower sulfur content fuels (<1.5%, referred value based on the heating value of standard coal of China), increasing Ca/S enough could decrease SO2 emissions lower than that of the new NER, 100 mg · Nm(-3). For fuels with sulfur content higher than 1.5%, some simplified systems for flue gas desulfurization, such as flash dryer absorber (FDA), are needed. And the NOx emissions of a CFB can be controlled to less than 100 mg · Nm(-3) without any equipment at a bed temperature lower than 900 °C for fuels with low volatiles content (<12%), while for fuels with high volatiles, selective non-catalytic reduction (SNCR) should be considered. Due to the unique temperature in CFB as well as the circulating ash, the efficiency of SNCR could reach as high as 70%. The Hg emission of CFB is very low for the new NER due to its innate property.

Studies on Magnesium-Based Wet Flue Gas Desulphurization Process with a Spray Scrubber

As China became the largest SO2 emission country in the world after 1999, the State Environmental Protection Administration has targeted to reduce the national SO2 emission level since 2000, which required that all new thermal power units as well as the most existing ones must have flue gas desulphurization (FGD) systems installed. The domestic research on flue gas desulphurization is becoming the hottest topic in environmental science and engineering over the years. The sulphur dioxide removal was first applied in 1930s, nearly 100 different FGD processes and process variations have been studied. However, only a few results have been applied in the industry. Among these techniques, wet FGD processes are the most widely used in most countries because of their high desulphurization efficiency. The magnesium-based wet FGD process is one of the techniques to meet these requirements, which has been increasingly used on the industrial boiler in China because of its low investment, compact flow sheet, less land occupied, high efficiency, reliable operation, rare fouling and low price of the magnesium-based absorbent. MgSO4 is the byproduct from magnesium-based wet FGD process and can be sold as fertilizer. Though the FGD processes have been studied by a number of researchers, it should be noted that the magnesiumbased wet FGD process has not been the subject of many studies. The present work was undertaken to make a systematic Studies on Magnesium-Based Wet Flue Gas Desulphurization Process with a Spray Scrubber

Highly efficient and economical nitrogen oxides controlled by an in‐furnace urea solution pyrolysis coupled with SCR system for a coal‐fired utility boiler

ABSTRACTAn in‐furnace urea pyrolysis coupled with selective catalytic reduction (SCR) system was applied on a 125 MW tangentially coal‐fired utility boiler in China. The coupling system was well‐designed to distribute NO and NH3 more uniformly in the flue gas at the inlet of the SCR reactor. The experimental results showed that the homogeneous NO and NH3 concentrations distribution could result to better performance of the SCR reaction. A 15 wt% urea solution directly injected into the furnace at the same flow rate of 1.2 t/h in Cases 4–6, corresponded to the normalized stoichiometric ratio of 1.40, 1.47 and 1.35. The coupling system showed a high NO reduction efficiency of up to 85–89% and could control NO emission to as low as 40, 34 and 27 ppm, respectively, with NH3 slip less than 5 ppm. The calculated urea utilization efficiency was above 58% in the cases. The high utilization efficiency of the urea solution would significantly reduce the running cost of the system. There were only five injectors at the boiler's front wall, and one layer of total 90.3 m3 catalysts in the two SCR reactors, which would drastically reduce the initial investment. The effects of the urea solution flow rates were studied at 100 and 125 MW boiler loads; it was found that 1.2 t/h was the suitable flow rate of the urea solution, and the NO emission could be controlled lower than 40 ppm. The coupling system was stable, efficient and cost‐efficient in industrial operation. © 2012 Curtin University of Technology and John Wiley &amp; Sons, Ltd.

Experimental study on the aerodynamic and separating characteristics of a novel tiny‐oil ignition cyclone burner for down‐fired utility boiler

ABSTRACTA novel tiny‐oil ignition cyclone burner is presented in this paper. Such a burner is an improvement and modification of the cyclone burner of the Foster Wheeler (FW) Company. In order to reduce the oil consumption during the start up and low load operation of the W‐shaped flame pulverized coal‐fired utility boiler, tiny‐oil technology is introduced to the cyclone burner based on the design concept of staged ignition. This burner is employed in down‐fired boiler, with the advantages of burning low volatile coal more efficiently and reducing the oil consumption. Experiments are carried out to investigate the aerodynamic characteristics and the coal particle separation efficiency of the novel tiny‐oil ignition cyclone burner. The influence of the vent air damper opening on the performance of the cyclone is studied. The modifications and improvements on the novel tiny‐oil ignition cyclone burner produce no unfavorable influence on performance of vent air ratio and the separating efficiency. This burner has been employed for a 300‐MW down‐fired pulverized coal utility boiler in China, and the oil consumption reduces by 70% compared with the technology of FW Company. Copyright © 2011 Curtin University of Technology and John Wiley &amp; Sons, Ltd.

Cost-Efficient Nitrogen Oxides Control by a Hybrid Selective Noncatalytic Reduction and Selective Catalytic Reduction System on a Utility Boiler

Abstract The hybrid process of selective noncatalytic reduction (SNCR) followed by selective catalytic reduction (SCR) is an up-to-date nitrogen oxides control technique and can achieve a high efficiency (60%–95%) with moderate cost. The SNCR/SCR hybridization was investigated through experimentation on a 100 MW, coal-fired utility boiler in China. The baseline nitrogen oxides emission of the hybrid urea-based SNCR/SCR system was 170 ppm at 6% O2 controlled by coal reburning technology. The hybrid SNCR/SCR system including only 89 m3 catalysts could control NO emission under 25 ppm with ammonia slip <4 ppm at 300–430 tons/h of boiler load. Total NO reduction efficiency was generally about 85% and could be beyond 90%, in which SCR's efficiency was 50%–70% individually and SNCRs was about 60%–75%. NO emission decreased from about 65 to 15 ppm when the flow rate of 35% urea solution increased from 0.15 to 0.47 tons/h. At higher boiler load, more urea solution had to be injected and higher layer of the agent ...

Bamboo Wastes as Fuel in Industrial Boiler in China

: It is estimated that more than 500,000 industrial boilers (mostly stoker-fired) in China consume over 400 million tons of coal per year. Because of low efficiency (only 60-65 percent) of industrial boilers, the energy consumption and pollution emissions from industrial boilers rank second place in China’s industry. On the other hand, China is rich in bamboo resource, and bamboo forest area is more than 5 million hectares, and occupies more than 1/4 of the world’s total. However, the common utilization rate of bamboo timber’s physical processing is below 40% in weight, over 60% of bamboo timber becomes left over when processed. Bamboo wastes, compared with coal fuel, are a very clean and renewable and sustainable energy. Therefore, there is the requirement that coal fired industrial boiler change its fuel into bamboo wastes in China, and some suggestions for bamboo fired boiler are presented in this paper. It is well economy of bamboo fired boiler in the region of China where an abundance of bamboo wastes disposed.

Experimental investigation on heat transfer and frictional characteristics of vertical upward rifled tube in supercritical CFB boiler

Water wall design is a key issue for supercritical Circulating Fluidized Bed (CFB) boiler. On account of the good heat transfer performance, rifled tube is applied in the water wall design of a 600MW supercritical CFB boiler in China. In order to investigate the heat transfer and frictional characteristics of the rifled tube with vertical upward flow, an in-depth experiment was conducted in the range of pressure from 12 to 30MPa, mass flux from 230 to 1200kg/(m2s), and inner wall heat flux from 130 to 720kW/m2. The wall temperature distribution and pressure drop in the rifled tube were obtained in the experiment. The normal, enhanced and deteriorated heat transfer characteristics were also captured. In this paper, the effects of pressure, inner wall heat flux and mass flux on heat transfer characteristics are analyzed, the heat transfer mechanism and the frictional resistance performance are discussed, and the corresponding empirical correlations are presented. The experimental results show that the rifled tube can effectively prevent the occurrence of Departure from Nucleate Boiling (DNB) and keep the tube wall temperature in a permissible range under the operating condition of supercritical CFB boiler.

Performance improvement and reduction of emissions from coal-fired utility boilers in China

An international partnership between Canada and China was established to improve performance and reduce emissions from coal-fired utility boilers. A well-tested computational fluid dynamic (CFD) modeling tool was used to identify the improvement strategies for 11 selected units ranging from 200 to 600 MW e, to increase operation availability and realize the reduction of coal consumption, acid rain precursor NO X and green house gas CO 2 emissions. Sustainability measures were introduced to promote replication of project results by the Chinese partners to maximize impact beyond the duration of the project. It is estimated that the study results could potentially be extended to 23% of the 2005 coal-based power generation capacity in China to achieve significant CO 2 emissions reduction prior to implementing advanced clean coal technologies like Integrated Gasification Combined Cycle (IGCC) and oxy-coal combustion with CO 2 capture.

Mathematical modeling and thermal-hydraulic analysis of vertical water wall in an ultra supercritical boiler

Water wall design is a key issue for an ultra supercritical boiler. In order to increase the steam–water mixture turbulization and to prevent the burnout of tubes walls, vertical rifled tubes are applied in Yuhuan power plant boiler which is the first 1000 MW ultra supercritical boiler in China and began to operate in December 2006. Mathematical modeling and thermal-hydraulic analysis are key factors for the successful design and operation of water walls. The water wall system is treated in this paper as a network consisting of circuits, pressure grids and connecting tubes. The mathematical model for predicting the mass flux distribution and metal temperature in water wall is based on the mass, momentum and energy conservation equations. An experiment on the heat transfer characteristics of vertical rifled tube was conducted with the aim to obtain the heat transfer performance and corresponding empirical correlations. The fitting computational formulas are applied in the mathematical model. The presented modeling method is more accurate than the conventional graphic method and can be applied to complex circuit structures. The mass flux distribution and the metal temperature in the water wall are calculated at 35%, 50% and 100% of the boiler maximum continuous rating (BMCR). The results show a good agreement with the plant data. The maximum relative difference between the calculated mass flux and the plant data is 9.7% at 50% BMCR load. The metal temperature difference in the tip of fins in lower circuit 8 is about 3–7 °C at 35% BMCR load. The results show that the vertical water wall in the ultra supercritical boiler of Yuhuan power plant can operate safely.

Application of gaseous fuel reburning for controlling nitric oxide emissions in boilers

An experimental study was performed on a 36 kW th down-fired furnace in order to obtain a wider and more detailed knowledge of the influence of the key parameters on the gaseous fuel reburning process when typical Chinese coals served as the primary fuel. The experimental results show that both above 50% nitric oxide reduction and low carbon loss can be obtained when reburn zone residence time is about 0.6 s–0.9 s, gaseous reburn fuel percent is about 10%–15% and average excess air coefficient of reburn zone is about 0.8–0.9. According to the optimizational reburning operating parameters, a 350 MW e coal-fired boiler was retrofitted for reburning application. The retrofitted boiler had about 0.7 s reburn zone residence time and about 2 s residence time after the burnout air was injected. The results of the demonstration on the full-scale boiler showed that the nitric oxide emission was about 235 mg/Nm 3 (O 2 = 3%, dry) from the retrofitted boiler and above 60% nitric oxide reduction efficiency could be achieved with no adverse effects on the boiler operability when the coke-oven gas used as the reburn fuel. This successful demonstration project filled the gaps in the gaseous fuel reburning application on 300 MW e grade unit boiler in China and showed that the values of the optimizational reburning parameters obtained from experiments could be successfully applied to the designing, retrofitting and optimizing for the gaseous fuel reburning process.