Advanced Materials Research Vols. 354-355

Abstract: The high temperature air combustion performance of natural gas in an industrial furnace with a swirling burner was numerically modeled. A Beta function PDF (Probability Density Function) combustion model was selected to simulate the gas combustion combined with the Reynolds Stress Model (RSM) to simulate the turbulent flow. The radiation was simulated by a Discrete Ordinates method. The NO chemistry was simulated by thermal NO model. The simulation was performed at inlet air oxygen fraction 8% and the total air excess ratio 1.1 for natural gas. The effect of preheated air temperature on NO emission, temperature, O₂ and CO distribution in the furnace was investigated. Results showed that thermal NO emission increased when the preheated air temperature increased from 1073 K to 1473K. When the preheated air temperature increased, both of the maximum and averaged temperature in the furnace increased. The oxygen was consumed by the formation of thermal NO at higher inlet air temperature and the fuel was not fully burnt out.

Abstract: There exist certain limitations to research the law and influence factors of the nitrogen oxides formation only with the help of field tests, because the nitrogen oxides formation of the boiler is influenced by various factors. The flow, combustion mathematical models interrelated and so on are established taking the 410t/h boiler fired tangentially as a prototype by the use of the fluent software. All the mathematical models are verified and modified with the aid of routine field test data, and the accuracy and reliability of the mathematical models are improved. Then NO_x formation performance is stimulated in allusion to the influence factors without field test conditions. The mathematical simulation results show that mathematical models can provide a sufficient theoretical basis to analyze accurately combustion and NO_x formation law in furnace, and the deficiencies of field tests have been made up.

Abstract: In this paper, cycle efficiency, net electric power and steam lose rate are calculated between the single flash and binary geothermal power system. The prime mover is 10kW single screw expander. These parameters of the single flash system are calculated by rated inlet volume flow rate of the single screw expander. The heat absorption capacity of both systems is determined to be equivalent. The working fluids of binary system are R134a, R245fa, and R600a. Those parameters of binary system are calculated with the condition that the saturated temperature of the working fluid before pump is 22°C. Engineering Equation Solver (EES) software is used for analysis. The results show that electric power of the single flash system is on the rise and steam loss rate of the single flash system is on the decrease with an increase of the inlet temperature between 100°C and 155°C. From the same heat absorption capacity, the binary system has apparent improvement in electric power and efficiency. The efficiency of binary system can increase by 2.1% compared with single flash system.

Abstract: After the temperature medium voltage coal boiler changed to burn biomass, the quantity of the smoke greatly increased, the economizer heat increased and the boiling rate rose, which tends to cause the economizer’s tuber wall to overheat. In this article, the calculation formula of the economizer’s tube’s outside surface temperature and the average temperature are deduced based on the basic thermal law. Besides, by measuring the economizer’s wall temperature, the relation between the wall temperature and the boiling rate is attained and two limit boiling rate concepts which judge the safe work of the economizer are also put forward. What’s more, the window procedure which calculates the wall temperature and the limit boiling rate is also compiled. In the end, the authors summarize the rapid- increasing change rule of the wall temperature between the two limit boiling rates and hold that the biomass boiler boiling rate should be controlled below the first boiling rate.

Abstract: Based on the experimental data obtained in natural circulation experiment in narrow rectangular channel, critical heat flux (CHF) was detected and analyzed through wavelet transform, and the technology of edge detection was applied in the analysis of the photos of CHF which were taken in the experiment. Results showed that the apply of wavelet transform using of db1 wavelet and edge detection using of Canny algorithm could both distinguish the singularity of CHF in one-dimensional temperature signal and regions of dry patch that represented CHF phenomena in two-dimensional photograph accurately, which can provide a new approach in the analysis of CHF experimental research of natural circulation.

Abstract: Experimental investigations on hydrodynamic characteristics of cylindrical pressurized spout-fluidizing bed were carried out. Two kinds of millet were used as bed materials. The operational pressure is 0.1MPa~0.4MPa (absolutely pressure). Five distinct flow patterns, i.e, fixed bed(FB), jet in fluidized bed with bubbles(JFB), jet in fluidized bed with slugging(JFS), spout with aeration(SA) and spout-fluidizing bed(SF) were identified. Effects of the static bed height and operational pressure on the flow pattern map were particularly studied. Typical flow pattern images obtained by a high- resolution digital CCD camera were presented for classifying these flow patterns. Typical flow pattern maps were plotted for describing the transitions between flow patterns with operating conditions

Abstract: Introduced the supercritical unit boiler feed-water supply system of once-through boiler’s structure and characteristics, and the feed-water supply system control principle and control strategy. Analysis of the system all controlled object and based on the interaction between the mid-point in the feed-water supply system enthalpy control of the regulatory process and problems, and put forward the corresponding optimization measures, and simulation research, the simulation results show that the feed-water supply system to improve the quality of the feed-water supply system adjustment, the main adjust the parameter of good quality, safety and economy got the reliable guarantee.

Abstract: This paper discusses the problems of instable combustion, serious slag, outfire in boilers with horizontal concentrated boiler, taking a 410t/h boiler as the sample. Through experimental researches on different adjusting characteristics of horizontal concentrated burners, it is found that the coal air mixture has different characteristics in velocity and concentration when the baffles are respectively left in the centrifugal or centripetal side of the bent pipes, and that the baffles wear pattern also depends on individual installation location. During many cold and hot commissioning tests, the effective height of baffles is regulated and the original refractory belts are replaced to vertical evenly spaced bare-tube wall. After taking the above measures, the significant problems in the boiler are settled and the economics and safety operation performance is improved considerably. Thus the paper can offer certain references for other boilers with horizontal concentrated burners.

Abstract: A new heat exchange pipe—heat exchanger inserted by disturbance device has been introduced. By applying commercial software—Fluent, the heat transfer and the flow performance of the heat exchanger which is a three-dimension numerical simulation in which the medium is air have been simulated, With simulation analysis of flow field in the heat exchanger，the enhanced transfer mechanism has been got; Using the heat transfer efficiency j/f, nine different models with different bending curvature and column spacing have been analyzed. Through analyzing the impact of the heat transfer and the flow performance on different bending curvature and column spacing, the best combination is achieved. Providing a certain theoretical basis, for research and design new type of heat exchanger pipes.

Abstract: The numerical model was established to simulate the gas flow and heat transfer in cement grate cooler. It is useful to increase the gas temperature when the extracting exit position is close to the cement kiln end. The appropriate position of the extracting high temperature gas is about 5 m far away from the cement clinker inlet.