Efficient and clean combustion and distribution te

Pulverized coal efficient and clean combustion and distribution technology

preface

in recent years, with the increasing attention of governments to environmental protection, the movement of pollution control and environmental protection has sprung up all over the world. New environmental protection technologies and products continue to emerge, but also continue to generate new problems. Pulverized coal combustion plays an important role in pollution emission, and it has always been the focus and difficulty of high-precision pollution control. Many countries have always regarded it as the central task in the activities of environmental pollution control, and have achieved relatively obvious results. It is predicted that the proportion of coal in China's primary energy demand will still be about 70% from 2000 to 2010, and will drop to less than 50% by 2050, but the absolute amount of coal consumption has increased significantly. Therefore, for our government, to control the overall indicators of environmental protection, we must first control the pollution caused by coal combustion. The way out is to vigorously develop clean coal technology with the purpose of efficient and clean utilization of coal

during the decade of continuous development of clean coal technology, many products and complete sets of technologies have been developed at home and abroad. There are advanced coal preparation technology, coal water slurry technology, coal gasification and coal liquefaction technology, circulating fluidized bed, pressurized circulating fluidized bed, integrated coal gasification combined cycle and other technologies, flue gas purification technology of various treatment levels and comprehensive utilization technology of fly ash. Considering the current situation in China, the technology of efficient and clean combustion of pulverized coal and flue gas purification should have broad application space in the near future

current situation of pulverized coal efficient and clean combustion technology and flue gas purification technology

pulverized coal efficient and clean combustion and flue gas purification technology include high-efficiency combustion technology, low NOx combustion technology, flue gas desulfurization technology, flue gas denitration technology, dust removal technology, etc. Now it is briefly introduced as follows:

generally speaking, pulverized coal efficient combustion technology and low NOx combustion technology are two contradictory technologies. The fundamental reason for reducing NOx generation and emission is to control the temperature in the combustion area not to be too high, but low-temperature combustion affects the combustion rate of pulverized coal. The purpose is to coordinate the application of these two technologies to achieve the best comprehensive effect. In fact, it is required to control the whole process of pulverized coal combustion. It can not only ensure the stability of pulverized coal ignition, but also have a low combustion temperature. At the same time, it has a long enough combustion time at a certain temperature to ensure burnout. At present, the more advanced combustion technology in the world basically takes these factors into account. Among them, the once through burners are mainly: abb-ce company uses the inertia separation effect of the primary air elbow, and sets a perforated diaphragm in the middle of the elbow outlet to divide the pulverized coal flow into two sections, the upper and lower dense and thin pulverized coal burners, and a V-shaped blunt body with adjustable axial distance is installed at the nozzle. By reasonably organizing the secondary air, At the same time, the combustion effect of stability, high efficiency and low NOx emission is achieved; Mitsubishi Heavy Industries (MHI) of Japan has developed a PM type burner, which uses the centrifugal action of the elbow to divide the primary air into upper and lower thick and thin air streams. At the same time, the flue gas recirculation and integral staged combustion technology in the furnace have also achieved good results. Swirling burners are mainly used: FW company uses cyclones to increase the concentration of primary air entering the main burner and reduce the primary air speed to ensure the ignition stability of pulverized coal flow and control the generation of NOx; There are also many industrial applications, such as Pax type swirl pulverized coal burner of b&w company, swirl pulverized coal burner of wide mediation range of IHI company in Japan, and multi-stage air supply swirl burner of steinmeller company in Germany. These industrial products can ensure NOx emission below 400mg/nm3 and have high combustion efficiency. At present, the low NOx combustion technology being developed abroad can control the NOx production at about 200mg/nm3, which has reached a relatively high level. However, because many advanced countries in the world have set strict standards for NOx emission, it is difficult to achieve NOx control value only by improving and improving combustion technology, so some boiler units have added flue gas denitration devices at the tail

in recent years, China has also developed many types of low NOx combustion technologies. The representative ones are dense dilute pulverized coal burners, including horizontal Dense dilute, upper and lower Dense dilute once through burners, swirl burners and controllable Dense dilute swirl pulverized coal burners. However, due to the variety of coal and other problems in China, these technologies have encountered some problems in application, including coal-fired units manufactured with similar foreign technologies. Through efforts, recently, a complete set of low load stable combustion and low NOx emission combustion technology with certain coal adaptability has been developed and industrially applied for lignite boilers, which can control NOx emissions below 400mg/nm3 and combustion efficiency above 99%, which is relatively advanced

flue gas desulfurization, denitration and dust removal are the three main contents of flue gas purification. In terms of flue gas desulfurization, wet desulfurization plays an absolutely dominant role, accounting for more than 90% of the market in developed countries. Other desulfurization technologies include semi dry desulfurization, humidification of calcium injection tail in the furnace, flue gas circulating curing bed method, electron beam ammonia method and so on. In terms of development, wet desulfurization is still dominant due to its high indicators, and flue gas circulating vulcanization bed desulfurization method has gradually occupied some markets due to its comprehensive advantages in technology and economy, and will be gradually applied in a large number of developing countries. For China, it is best to adopt wet desulfurization technology for new units, and the equipment should be in place in one step; The retrofitted unit depends on the sulfur content of the coal. For example, for high sulfur coal, the method of smoke exhaust circulating vulcanization bed can be adopted, and for low sulfur coal, calcium injection in the furnace and tail humidification can be adopted, especially the value of a large number of existing water film dust collectors can be comprehensively utilized. In terms of flue gas denitration, foreign countries generally use selective reduction reaction devices to remove most of the nitrogen oxides in flue gas, and other methods are still in the development and research stage. Due to the limitations of capital and site, there is no precedent for industrial application in China, and it is temporarily unable to complete the construction of demonstration units. In terms of flue gas dust removal, due to the continuous increase in the requirements of developed countries for smoke emission rate and ultra-fine particle dust removal rate, many countries have gradually changed the electrostatic precipitator to pulse filter, which can print the standard experimental report based on the force value, displacement, stiffness, curve and other data. This can be represented by Australia, the United States and other countries. China plans to replace a large number of cyclone dust collectors or water film dust collectors of medium-sized units with electrostatic precipitators in the near future. The index is that the export smoke and dust is not more than 200mg/nm3, and there is no requirement for floating dust. On the proposed Dalian Taishan pressurized circulating vulcanization bed boiler, the Chinese side plans to adopt the pulse back blowing filter bag dust collector to achieve high performance

scientific research work and application of achievements during the "Eighth Five Year Plan" and "Ninth Five Year Plan" of the national power station Combustion Engineering Technology Center

Introduction to research facilities

whether mechanism research or pilot scale test can be divided into three parts: aerodynamic characteristics test, gas-solid two-phase flow characteristics test and coal combustion characteristics test. Therefore, the center has built three test halls to meet the different requirements of the three tests

the aerodynamic characteristics test hall has a total area of 800m2, with a main air supply pipe and a total air volume of 50000nm3/h. It is divided into four areas: the flow characteristics research area of a single burner, the flow characteristics area in the furnace, the energy-saving and resistance reduction area of the optimized structure, the measurement device and damper detection and other product technology development areas. The test instruments include dandy 3D system, PIV system and other conventional instruments. At present, more than 30 bench laboratory research work has been completed and many of them have achieved good results in field application. In addition, there are other supporting mechanism research test-bed and flow field calculation software

the 500m2 gas-solid two-phase flow test hall is also the main air supply pipe. The total air volume is 35000nm3/h, the pressure head is 10000pa, and the powder supply can reach 200kg/h. The powder is silicon carbide or pulverized coal and fly ash of power plant. It can be used for the development of concentration and dilution burners, the improvement of cyclone separation and dust collector, the research of electric dust collector and filter bag dust collector, the research of flow characteristics of desulfurization tower, and the research of wear test, etc. In addition, there are independent pulverized coal distributor test-bed, automatic adjustable cascade shutter pulverized coal distributor test-bed and other mechanism test-bed. The testing instruments include laser holography system, sheet light source shooting system, Kurt particle sizer, optical fiber concentration analysis system, flow field graphic reconstruction analysis system and other conventional testing systems for concentration and flow field

the 700m2 coal combustion characteristics test hall can be divided into three parts. The first part is the introduction of the pilot coal combustion test system (CRF) of Ontario power company of Canada. The hourly coal consumption is 20kg and the thermal power is 0.2mw. The device is divided into raw coal drying system, raw coal crushing system, pulverizing system, combustion system, primary and secondary air system, flue gas treatment system, furnace calcium injection system, flue gas dust removal system, flue gas composition testing system and control system. The test system and control system adopt Rosemount flue gas analysis system and other flow, temperature and pressure sensors, all of which are input into the computer and all variables are dynamically adjusted by the computer to meet the test conditions and requirements. The device can comprehensively and accurately simulate the whole process of raw coal drying, crushing, pulverizing, pulverized coal conveying, combustion and flue gas treatment. It can focus on the evaluation and research of the influence of fuel quality on combustion stability, burnout degree, sediment formation, pollutant formation, particle emission and collection, and can develop new low NOx Combustion Technology in this process Calcium injection technology and other flue gas treatment technologies in the furnace. This device has a high degree of automation, a high level of control and testing instruments, and a good test repetition rate. It can carry out a wide range of technical development and research. It is one of the more advanced coal combustion test devices in the world. At present, the center has made some modifications to this test device, rebuilt the combustion system, increased the combustion power to 0.3mw, increased the flue gas tail humidification activation device, increased the suspension flue gas desulfurization device, and is carrying out new research

the second part is the atmospheric entrainment fluidization and combustion simulation device (aefgc) jointly built with the Dutch Energy Foundation (ECN). It is equipped with an integral, premixed and multistage flat flame gas burner, with a coal consumption of about 5g per hour. By providing different mixed gas powders in different stages, it simulates the initial heating rate, premixed and gaseous environment experienced by particles in the actual process. It is the infrastructure for the study of approximate single particle mechanism. It is equipped with gas analysis system, powder supply system, testing system and other advanced control systems

the third part is the basic research facilities, including thermogravimetric/differential thermal synchronous analysis laboratory, fuel element rapid analysis and other fuel characteristics analysis laboratory. It can be used for experimental research and analysis of coal ignition characteristics, burn out rate, combustion reaction kinetics and desulfurization mechanism

in addition to these physical studies, the center has also allocated some specialized personnel to carry out numerical simulation research on flow, diffusion and combustion, and introduced a set of numerical simulation software including NOx generation prediction from Germany, which has achieved certain results

research and application

during the "Eighth Five Year Plan" and "Ninth Five Year Plan", the center has undertaken more than 100 vertical and horizontal scientific research and production transformation and industrial manufacturing projects. Among them, there are seven thematic sub thematic projects of the key research projects of the Ninth Five Year Plan of the State Science and Technology Commission and two demonstration production line construction projects of the State Planning Commission