煤粉工业锅炉技术发展及应用

中国煤粉工业锅炉借鉴油气锅炉和德国煤粉工业锅炉技术理念,经历立项研发、中试验证和工业示范,系统技术逐步成熟,自2010年起,实现规模化工业应用。煤粉工业锅炉系统具有高热效率、低烟气污染物排放等优点,有效带动了燃煤工业锅炉产业发展。笔者论述了煤粉工业锅炉技术与发展,重点介绍了煤粉工业锅炉的关键技术,并对主要技术进行对比,分析了煤粉工业锅炉的工业应用情况,最后提出了煤粉工业锅炉技术发展方向。煤粉工业锅炉系统由燃料煤粉生产、储供、油气点火、燃烧、锅炉本体、烟气净化以及自动化控制等系统构成。锅炉热效率大于91%,烟气污染物达到国家超低排放标准,系统技术符合国家煤炭清洁利用方向。燃料煤粉生产采用一步法工艺,通过强化流动性和安全措施,现可实现最大为1 000 m^3安全存储量。锅炉供粉采用气动活化、无脉动给料及高速引射流浓相输送技术,已实现输送阻力低于20 kPa,粉风固气比大于2.5 kg/m^3,供料精度在±3.0%以内,最大供料量为5 t/h的浓相供料技术与装备,广泛应用于锅炉供料系统。供料量在2.5 t/h,供料精度在±2.0%和±1.0%以内的第三代和第四代供料器也分别开展了工业验证和样机的试制工作,并取得了阶段性的成果。煤粉燃烧器采用逆喷式回流式结构,设计工作依据其结构特征,通过模拟气流扩展角、回流区域范围、回流量、旋流强度以及温度和速度场等研究开展,再经过实际工程应用,进一步验证优化设计参数,最终实现燃烧器的逐级放大。天然气/煤粉双燃料燃烧器具有便捷切换和快速着火功能。风冷燃烧器采用内外双级旋流供风燃烧技术,具有点火迅速、燃烧稳定、燃烧效率高和初始NOx排放低等优点。随着煤粉锅炉系统测控技术向智能化、网络化和集成化方向发展。锅炉烟气脱硫除尘采用NGD高倍率灰钙循环脱硫技术,具有占地小,运行成本低等特点,在低钙硫摩尔比下,系统脱硫和除尘效率分别达到90%和99.95%以上。低温炭基预氧化脱硝耦合NGD协同烟气净化技术具有工艺简单,耗水少,废物资源再利用,无二次污染产生等优点,更加适合于煤粉工业锅炉的烟气净化。煤粉工业锅炉在发展历程中通过关键技术和装备优化升级,在大型化、模块化和系列化方向已取得成效,在节能性、环保性和经济性等方面较常规工业锅炉具有显著优势,技术已达到世界先进水平。未来随着国家能源结构优化,天然气/煤粉锅炉、低氮燃烧、生物质复合半焦粉及协同化烟气净化等技术的开发与成熟,煤粉工业锅炉技术将成为煤炭清洁燃烧利用主要技术之一。

Development and application of the technology of pulverized coal industrial boiler

In China,pulverized coal industrial boiler has drawed lessons from the technical concepts of oil-gas boilers and German pulverized coal industrial boilers,which experiences project development,pilot test certificate and industrial demonstration.The system technology is gradually maturing.Since 2010,large-scale industrial application has been achieved.The coal-fired industrial boiler system has the advantages of high thermal efficiency and low emission of flue gas pollutants,which effectively promotes the development of coal-fired industrial boiler industry. In this paper,the technology and development of coal-fired industrial boiler were discussed,the key technologies of coal-fired industrial boiler were mainly introduced,the main technologies were compared,and the industrial application of coal-fired industrial boiler was analyzed,and finally the development direction of coal-fired industrial boiler technology was put forward.The results show that the technical system of pulverized coal industrial boiler consists of pulverized coal production,storage and supply,oil and gas ignition,combustion,boiler body,flue gas purification and automatic control system. The boiler thermal efficiency is more than 91 %,the flue gas pollutants meet the national ultra-low emission standard,and the system technology is more in line with the national coal clean utilization direction.The one-step process is adopted in the production of pulverized coal. The safe storage technology can achieve a storage capacity of 1 000 m^3 by strengthening the fluidity and safety protection measures of pulverized coal.The technology of pneumatic activation,pulse less feeding and high-speed jet dense phase conveying is adopted for feeding.The conveying resistance is less than 20 k Pa,the powder-air-solid ratio is more than 2.5 kg/m^3,the feeding accuracy is less than ±3.0 %,and the maximum feeding amount is 5 t/h.The dense phase feeding technology and equipment are widely used in the boiler feeding system.The feeding amount 2.5 t/h third-generation and fourth-generation feeders with feeding accuracy within ± 2.0% and ± 1.0% also carried out industrial verification and prototype trial production respectively,and achieved phased results.The pulverized coal burner adopts the reverse injection type reflux structure.According to its structural characteristics,the design work is carried out by simulating the air flow expansion angle,reflux area range,reflux flow,swirl intensity,temperature and velocity field,and then through practical engineering application,the design parameters are further verified and optimized,and finally the gradual amplification of the burner is realized.The natural gas/pulverized coal dual fuel burner has the functions of convenient switching and fast ignition.The air-cooled burner adopts internal and external two-stage swirl air supply combustion technology,which has the advantages of rapid ignition,stable combustion,high combustion efficiency and low initial NOxemission.With the development of pulverized coal boiler system technology,the boiler structure has gradually formed the related design and manufacturing specifications.Based on the continuous improvement of technology and equipment,the measurement and control technology is developing towards intelligence,networking and integration.Boiler flue gas desulphurization and dust removal adopts NGD high rate ash-calcium cycle desulphurization technology,which has the characteristics of small land occupation,low operating cost,and the system’s desulphurization and dust removal efficiency can reach 90 % and 99.95 %,respectively,at a low molar ratio of calcium and sulfur.The low-temperature carbonbased pre-oxidation denitration coupled with NGD synergistic flue gas purification technology being developed is in the same direction as the synergistic purification of flue gas at home and abroad.The utility model has the advantages of simple process,less water consumption,reuse of waste resources,no secondary pollution,etc.,which is more suitable for flue gas purification of pulverized coal industrial boilers.The pulverized coal industrial boiler has been optimized and upgraded through key technologies and equipment in the development process,and has achieved results in the direction of large-scale,modularization and series.It has significant advantages over conventional industrial boilers in terms of energy saving,environmental protection and economy,and the technology has reached the world advanced level.In the future,with the optimization of the national energy structure,and the development and maturation of natural gas/pulverized coal boilers,low-nitrogen combustion,biomass composite semi-coke powder,and synergistic flue gas purification and other technologies,pulverized coal industrial boiler technology will become one of the main technologies for clean coal combustion.