In a coal-fired power plant, pulverized coal, using air as a transport medium, is pneumatically transported toward different burner nozzles by splitting the large pipe into small pipes through bifurcators or trifurcators. The combustion efficiency of the burner is dependent on matching the air and coal in these pipes. Increasingly tight emission standards also make the balance of air and coal a very critical factor for the success of the power plant. Coal roping occurs when the gas-solid flow passes through a curved pipe. The momentum of the particles carries them to the outside of the wall, concentrating in a small region. Therefore, the particle concentration in this small region is much higher than the other part of the pipe cross-section. Coal roping upstream of a coal distributor (bifurcator) can create a significant imbalance in coal loading in the split between the two branches. This can significantly impact plant performance and increase NOx production. Previous research [2] has shown that coal rope characteristics depend on many parameters; the geometry (i.e., elbow radius of curvature-to-pipe diameter ratio, pipe orientation, orifice opening, and the locations of orifices) of the coal pipe, which is determined at the design stage, will strongly affect the coal distribution in the outlet of coal pipes. This characteristic of coal roping indicates that optimizing the pipe geometry may be helpful in getting a more uniform coal distribution at the pipe’s outlet cross-section and minimizing the problems caused by imbalance between burners. In this paper, we present the CFD-based coal pipeline design tool to achieve the evenly distributed coal particle distribution across the pipe cross-section.

The NOx-CO reaction model was developed for commercial scale pulverized coal firing boilers. The model was used to decide optimize combustion performance and it featured simplified sub models of NOx reduction, pyrolysis and CO oxidation. To improve combustion performance of commercial scale pulverized boilers, it is most important to predict the distribution of NOx and CO concentrations and search for the best conditions in a short time. The NOx reduction sub model was developed for both volatile and char combustion. The pyrolysis sub model was developed from a comparison of Distributed Activation Energy Model results and experimental data. The CO oxidation sub model was characterized by its consideration of the effect of hydroxide radicals. The simulation gave a lower CO oxidation rate for a long reaction time, the same as the actual result. The NOx-CO reaction model successfully analyzed NOx and CO concentration distributions of commercial scale boilers for power plants (260–1000MW).

The traditional approach to reduce NO x has been to retrofit and install commercially available “plug-in” Low NO x burners. Typically, these use a combination of internal staging and are often used in conjunction with over-fire air to create off-stochiometric or staged combustion. That is, the complete combustion of the fuel occurs in several stages. Often, well designed Low NO x burners are installed without a comprehensive systems approach. The typical challenges associated with staged combustion are related to the fact that burner performance must be nearly perfect to complete combustion within the available residence time of the furnace. Specifically, attention to airflow measurement and control by use of reliable & repeatable venturis and with pulverizer performance optimization. To maintain or improve this unit’s excellent reliability, a focus on optimizing the inputs and completing the combustion prior to the furnace exit was implemented. The goals of this project were as follows: 1. NO x Reduction from .78lb/mmBtu(full load) – 1.0#/mmBtu(low load) to less than 0.36 lb/mmBtu; 2. Flyash Carbon Content less than 10%; 3. Combustion Optimization; 4. Minimal slagging; 5. Maintain the same as baseline FEGT or reduce FEGT; 6. Maximum Load Capability; 7. Maximum Fuel Flexibility; 8. Complete the project at the lowest cost per kW possible (with the best results). All of the goals were accomplished. The technical success of this project is the results of applying a systematic and comprehensive approach beginning with raw coal feed to the pulverizers. The benefits of this total combustion optimization project is that later when additional NO x reductions are required, they can be added as a complimentary change to the present system. For example, if this unit is later equipped with SNCR or SCR, reduced rates of ammonia will be required, there will be reduced “popcorn ash” production, and less SCR catalyst wear and overall unit improved performance and reliability.

Unit 1 at Hitachinaka Power Station, which is the newest 1,000MW coal fired power station of Tokyo Electric Power Co., Inc., entered into the commercial operation in December 2003. IHI (Ishikawajima-Harima Heavy Industries Co., Ltd.) constructed the flue gas treatment system with the state-of-the-art technology and low emission values. To meet demands for both reducing construction cost and high performance, IHI applied a single rectangular Absorber based on the simultaneous desulfurization and oxidation method, Nonleakage type Gas-Gas Heater (GGH) and Electrostatic Precipitator (ESP) at low-low temperature position. Unit 1 at Mizue Power Station of GENEX Co., Ltd., which is one of the independent power produces, entered into the commercial operation in June 2003. In this plant, IHI applied a high performance spray tower Absorber and wet type Electrostatic Precipitator (ESP) to meet the high desulfurization efficiency for vacuum residue oil firing and extremely rigorous regulation owing to location near the metropolitan area.

Three-dimensional (3-D) flowfield data has been obtained using Particle Image Velocimetry (PIV) for varying swirl distributions in the burner. The 3-D data also allows one determine the local swirl number of the resulting flow. Flow characteristics of the resulting flowfield, both without and with combustion, have been examined for the effect of co- and counter-swirl under lean direct injection conditions using unconfined and confined combustor geometry. Experimental results of the effect of swirl and combustion are presented to simulate the flow dynamics of Lean Direct Injection (LDI) configuration gas turbine combustion. The selected configuration is typical because it does not make use a premixing zone and relies totally on the swirl and the injector to accomplish rapid mixing. Specifically, the effect of radial distribution of combustion air and swirl in a burner are examined under non-burning and burning conditions using propane as the fuel. The present study explores single swirler interaction with the use of an experimental double concentric swirl burner that simulates one swirler of a practical gas turbine combustor. Results showed that both swirl and combustion has significant effect on the characteristics of the internal and external recirculation zones. The calculated local swirl number differs significantly form that estimated using geometrical relationship derived from the vane angle only. The effect of combustion for the confined and unconfined geometries was also been found to be different. In the confined geometry combustion decreases the size of the recirculation zone. This is in contrast to that found for the unconfined conditions. Combustion enhances the recirculation zone in the unconfined geometry. Combustion provides greater velocity magnitudes than their counter non-combustion conditions. The counter-swirl combination resulted in smaller and more well defined internal recirculation regions. The results provide the role of swirl and combustion on the mean and turbulence characteristics of flows over a range of swirl and shear conditions between the inner and outer flow of the burner. This data provides important insights on the flow dynamics in addition to providing data for model validation and model development.

Increasing attention has been given to the development of low-NOx combustion technology for DME (Dimethyl Ether). The present paper describes a R&D study for water-tube boiler carried out in Kansai University and Hirakawa Guidam Co. Ltd. under the support of DME project from METI. The main problem arisen in DME use is a difficulty in an application of premixed flame owing to low ignition temperature and rather high burning velocity. Then the previously developed tube-nested combustor, i.e. water-tubes are installed in the empty furnace, becomes effective means to overcome such difficulty in realizing low-NOx combustion. This paper begins with a brief review of R&D study of the tube-nested combustor specifically designed for city gas. Then further development for DME-fired water-tube boiler is described.

As an aid to the simulation of combustion in the power generation industry, a computer code has been developed using Excel/VBA to permit the rapid calculation of adiabatic flame temperatures and product species compositions for a large variety of easily specified fuel and air reactant conditions. Results are calculated immediately for the cases of “air” (with specified oxygen volume percentage) as the oxidant, with and without dissociation. Alternatively, the product temperature may be identified, and then the heat transfer in the combustor is calculated. In the general computer code developed, the very general fuel is specified by way of its C-H-O-N-S values. Additional water content may be specified. The “air” is specified by way of the volume percentage of oxygen and the other component (nitrogen and/or carbon dioxide). The temperatures of each reactant (fuel and “air”) are specified by the user. The computer code is very user friendly, with automatic nested loops for parameter variation and automatic generation of graphs, which are particularly useful in assessing the particular process under consideration.

Fires can be a major problem when they occur in industrial power generation facilities. The volume, temperature, composition of combustion product species, and location of smoke produced in fires may be calculated. A computer code is described that accomplishes this. Smoke cooling and volume changes are included from radiation heat loss from the fire, cooler air entrainment into the plume (column of smoke products above the fire), and conduction heat loss through the ceiling. Any hydrocarbon fuel, also possibly containing oxygen, is permitted as the fuel, and it burns with a specified equivalence ratio with air or oxygen. If in “air”, the volume fraction of oxygen may be specified. For simplicity and because most applications are to fires burning in air, dissociation is omitted since this is rather minimal at the temperatures encountered. The mathematical basis and algorithms are presented, together with the methodology of the Excel/VBA computer code that permits easy input and output, and results show the versatility of the code.

A comparative analysis of nitrogen and oxygen enriched combustion is presented in this paper. Nitrogen enrichment of intake air is proposed as an alternative to Exhaust Gas Recirculation (EGR). NO x reduction by EGR is not very promising due to engine reliability concerns and increased maintenance costs. Air separation membrane, on the other hand, is a potential strategy for NO x reduction due to uncompromised reliability of engine performance. Oxygen-rich and nitrogen-rich streams are produced by passing air through a nonporous polymeric membrane. Nitrogen Enriched Air (NEA) reduces NO x formation by lowering in-cylinder combustion temperatures but with a compromise in Fuel Conversion Efficiency (FCE). However, advanced ignition timing improves FCE considerably. Oxygen Enriched Air (OEA), on the other hand, improves FCE due to the availability of extra oxygen for better combustion which results in higher bulk gas temperatures and NO x emissions. This behavior could be controlled by retarding the ignition timing. Experimental results of nitrogen and oxygen enriched combustion of a Kohler M12 generator (converted to operate with natural gas) is presented in this paper. A 68% reduction in NO x and a 0.8% drop in FCE were observed at −30 ATDC ignition timing (IT) with 2.1% N 2 enrichment (40 slpm). A 9% O 2 enrichment (40 slpm) at −30 ATDC IT improved FCE by 1% but with higher NO x emissions. The increase in NO x emissions was minimal with a 2% improvement in FCE at −10 ATDC IT and 9% O 2 enrichment (40 slpm). Some of the drawbacks encountered were engine misfire at higher concentrations of nitrogen enriched air and retarded ignition timing resulting in poor FCE. This paper discusses both the approaches and highlights the benefits of nitrogen enrichment using an air separation membrane over its counterpart for NO x reduction.

The real time, in-situ measurement of excess oxygen and temperature in the radiant heat zone of a boiler or furnace provides a window for viewing combustion conditions closest to the source. Excess oxygen and temperature measurements, taken at strategic sample points around the firebox, provide timely information for optimal trim control of the combustion process. With fuel costs skyrocketing and a focus on reducing NOx emissions, it is essential that the excess oxygen measurement be fast and accurate. Commercially available in-situ, high temperature oxygen sensors have the potential to solve combustion control and burner management problems with short payback and high annual ROI in power applications.

Although coal fired power generation plant was originally designed to operate on a particular coal, increasingly stringent emissions regulations have led to modifications to both the coal type and firing mode. Low sulphur (S) coals minimize the requirement for sulphur dioxide (SO 2 ) scrubbing plant combustion modifications are used as the primary measure to reduce the emission of nitrogen oxides (NOx) and these changes in the firing regime and/or the coal type can also impact on the in boiler ash deposition, particulate collection and the overall efficiency of the boiler operation. Emission regulations requiring maximum NOx levels of 0.15lbs./MM.Btu. are at, or just below, the limit of NOx reduction achievable by primary measures and at this limit significant increases in unburnt carbon (UBC) in ash levels can be expected, which affect boiler efficiency and also the operation of any SO 2 and particulate collection plant. Coals are usually purchased, in addition to price, on quality based on the well established proximate and ultimate analyses, whereas parameters derived from these basic analyses may be more effective in defining the behaviour of a coal, substituted for the original design coal, in order to meet current emissions regulations whilst still maintaining an acceptable operating efficiency.

A study of spray combustion with porous inserts was performed using an on-axis fuel used in a concentric Jet-A. Combustion performance was evaluated by measuring exhaust emissions and flame temperatures for different operating conditions with and without ceramic foam inserts of various properties. The results indicated that the enhanced heat transfer in the flame zone could reduce nitrogen oxides and unburned hydrocarbon emissions. Placing a second porous layer downstream could yield further reductions in both emissions. The results for different firing rates and equivalence ratios revealed the residence time in the porous layer is an important factor regulating combustor performance.

The paper presents the results of a unique method of ash measurement at the NRG Huntley station. High Temperature strain gauges were installed in the boiler penthouse. The gauges were located on rods that support the superheater pendants. Output from the gages measure ash accumulation and soot blower effectiveness. Output from the system is utilized in the soot blower control system to optimize blower operation. The system will allow less steam to be used for soot blowing while keeping the superheater clean at all times. This is valuable to the plant as a switch to 100% PRB coal is made. The paper will present details of the installation.

Gas-liquid screen, a novel liquid-gas two-phase flow type, is applied in a scrubber for WFGD. According to the characters of the flow type, heat transfer experiments have been conducted to study the temperature distribution of flue gas in the tower and find the relation between heat transfer coefficient, flue gas and liquid velocity. The results show that whether in concurrent or countercurrent tower the heat transfer coefficient will increase with L/G decreasing at a fixed gas velocity. The optimum position of heat transfer is at the top of the Gas-liquid screen. So multilayer ‘Gas-liquid screen’ could to be arranged to optimize the effect of heat transfer and reduce the industry cost. The formulas of the relation between heat transfer coefficient, flue gas and liquid velocity are gained. These can provide strong foundation for the engineers and the further mass transfer experimental study.

This study was conducted to delineate the coupling effects of the elliptic geometry of the burner and a crossflow on the combustion of gas jets. This paper presents the flow and thermal structure of burner-wake stabilized turbulent propane jet flames from circular (diameter = 0.45 cm) and elliptic (major axis/minor axis = 3) burners of equivalent exit area in a crossflow of air. The elliptic burner was oriented with its major axis or minor axis aligned with the crossflow. Experiments were conducted in a wind tunnel provided with optical and probe access. Flame structure data including temperature profiles and concentration profiles of CO 2 , O 2 , CO, and NO were obtained in the single flame configuration (at jet to crossflow momentum flux ratio = 0.0067), where a planar recirculation zone exists completely stabilized in the wake of the burner tube. This study is complementary to our previous study with a two-zone structure flame at jet/crossflow momentum flux ratio of 0.11. Results show that in this flame configuration, the peak NO concentration in the circular burner is higher than that in the elliptic burner flames. Carbon monoxide concentration was approximately same in the flame with circular burner and the elliptic burner with its major axis aligned with cross-flow; the CO concentration in the elliptic flame with the minor axis of the burner aligned with cross-flow was slightly smaller.

This study was an investigation of the characteristics of a horizontal laminar diffusion flame established from a tubular burner in a buoyant vertical flow vitiated with combustion products created by a flat flame. The effects of varying flat flame equivalence ratio on these characteristics were studied. Applications of this study include exhaust gas recirculation (EGR), staged combustion in furnaces, and afterburners in jet engines. The fuel used for both the horizontal (cross-flow flame) and the flat flame in this study was propane. For a range of flat flame burner equivalence ratio (0.6 to 0.9), measurements of cross-flow flame length, and global emissions of NO were made. The mass flow rate of propane delivered to the cross-flow flame was held constant during these measurements. The flames were photographed with a digital camera. Profiles of combustion species concentrations and temperature were taken at 25% and 50% of the cross-flow flame length for flat flame burner equivalence ratios of 0.6 and 0.8, and for a non-combustion case (air flow only) in the flat flame. It was found that increasing the flat flame burner equivalence ratio caused an increase in the length of the cross-flow flame. The maximum temperature of the cross-flow flame decreased with increasing flat flame burner equivalence ratio. The introduction of the cross-flow flame increased the NO production in a flat flame with an equivalence ratio of 0.6, but did not significantly affect the NO production in a flat flame of an equivalence ratios of 0.7 or 0.8, and reduced it (by as much as 25%) in a flat flame of equivalence ratio of 0.9. This reduction of NO production and flame temperature and increase in flame length with increasing flat flame equivalence ratio was attributed to the reduction of oxygen available to the cross-flow flame. These results were supported with the in-flame combustion species concentration profiles.

A computational code, which can be used to calculate gas-liquid-solid 3-phase equilibrium line, has been developed based on the principle of free energy minimum. Then the equilibrium lines of dissolution of SO 2 and CaCO 3 in water are obtained using the code. The results satisfy the mass and charge conservation and match well with the data in the references. Finally, multiphase equilibrium lines of the reaction in WFGD are calculated in different conditions. The results show that temperature, concentration of SO 2 , CO 2 , have different effects on the solubility of SO 2 under initial conditions given in the paper. Temperature and concentration of SO 2 have great effects, and the concentration of CO 2 has a small effect. The solubility of SO 2 increases as the partial pressure of SO 2 increases, temperature decreases or the concentration of CO 2 decreases. These conclusions have a great guidance on designing the tower of wet flue gas desulphurization.

Coal fired power stations are among factors mostly polluting atmosphere by greenhouse gases, especially by CO 2 . Strong efforts are done to reduce this pollution, increasing the generation efficiency by gasification of coal, development of super -critical power units and so on. For the existing power station good results may be achieved by simultaneous optimization of the operation condition including proper choice of the fired coal. An analysis of data collected in IEC, where more than 60% of electricity is generated in coal fired units, makes it possible to explore dependence of greenhouse gases emissions (CO 2 , SO 2 , NO x ,) on the fired coals composition and operation condition. As a tool for the above data analysis computer technique, created in IEC, was used. The technique is based on a modular numerical model including elements corresponding to furnace, boiler, turbine and the whole power unit. It permits to reveal the influence of the coal composition on the boiler and the whole unit performance, as well as on the pollutant emissions. The technique application permitted to separate impact of the two factors: the coal composition and operation conditions on specific emissions of the pollutants. The main result of the study is that the optimization of operation condition while proper choice of the coal provides decrease of pollutants emissions. 2. Bioconversion of CO 2 emitted by power stations by intensive photosynthesis is one of the mostly efficient ways for carbon emissions mitigation, especially in countries with high solar activity. Agricultural projects based on CO 2 enrichment by flue gases -greenhouses, water ponds for macro and micro algae growing, forests, citrus orchards and other biological systems, if placed in the neighborhood of the coal-fired power stations with high content of CO 2 in the flue gases, can be profitable also because of use of cheap low-potential heat and the station infrastructure. Efforts for removal of pollutant components of the flue gases will be compensated by high CO 2 content. First steps in this direction have been done by IEC in collaboration with MATI Lev-ha-Galil, Hishtil Nurseries, ARO and IOLR, with support of the R&D Division of the Ministry of the National Infrastructure and showed feasibility of the proposal.

Flame detecting and diagnosis of combustion in modern coal-fired boilers are very important to the safe and economical operating of power generation unit. So the effective real-time detection of combustion flame stability and in-time judgment are necessary. One of the important characteristics of combustion flame is a combination of flame jet fluctuation and flickering of flame radiation, which is a time random variable and reflects the combustion conditions. In this paper, after the data are acquired through the tests in our university’s laboratory, the power spectrum analysis using algorithm of fast Fourier transformation (FFT) and a self-organized neural network are applied into a diagnostic system for combustion conditions. At first, a time series of radiation intensity values of the flame, which fluctuate at a mean intensity value with a certain frequency are obtained through the photoelectric sensor. And then the time signal is converted to the power spectrum signal through the processing of FFT. Under the stable and unstable combustion conditions, the spectral intensity of the low frequency component of the converted signal has distinct magnitude. According to this method, software for the power spectrum analysis and the self-organized neural networks has been developed.

Through analyzing the air and pulverized coal mixture flow characteristics of coal-fired boiler in power plant, it is put forward that measuring pulverized coal flow parameters is based on energy conservation theory and arrangement rule of measuring point location is for improving measurement precision. System for measuring temperature and velocity and concentration of air and pulverized coal mixture flow is developed, and some functions of on-line measuring air-pulverized coal mixture parameters are achieved. Adopting those efficient measuring methods are able to improve boiler operation’s safety and efficiency.