Development and technical progress in large-scale circulating fluidized bed boiler in China

Circulating fluidized bed (CFB) boilers has realized the clean and efficient utilization of inferior coal like gangue and coal slime, high sulfur coal, anthracite, petroleum coke, oil shale and other resources. As a country with the largest amount of CFB boilers and the largest installed capacity in the world, China has 440 100–600 MW_e CFB boilers with a total capacity of 82.29 GW_e, including 227 units of 135 MW_e, 95 units of 300 MW_e, and 24 supercritical units. The statistics of typical 100–300 MW_e CFB boilers showed that the average number of unplanned shut-down was only 0.37 times per year, among which the 135 MW_e was 0.26 times per year and 300 MW_e was 0.46 times per year. The auxiliary power ratio of some 300 MW_e CFB boilers based on flow-pattern reconstruction can be reduced to about 4%, which is closed to the same level of pulverized coal (PC) boilers. This paper summarizes the development process and application status of China’s large-scale CFB boilers, analyzes the characteristics and technical performance of the iconic units, and introduces solutions to the problems such as water wall wear and bottom ash cooling.     

600MW超临界CFB机组深度调峰运行技术

经通过分析超临界CFB机组在深度调峰方面的优势,结合600MW超临界CFB机组的实际运行工况,提出机组在深度调峰前应开展的试验工作。研究600MW超临界CFB机组的深度调峰过程,从汽机、锅炉、电气等方面提出有效的技术措施,解决深度调峰可能带来的锅炉流化不良、环保参数控制困难等问题。通过在600MW超临界CFB机组上应用,机组在30%负荷深度调峰运行,工况稳定,各项参数正常,取得了较好效果。     

超临界CFB机组汽动给水泵油中进水分析

白马循环流化床示范电站600MW超临界CFB机组自投运以来,A、B汽动给水泵组经常出现润滑油质偏差现象,主要原因为油中含水过大造成。通过对给水泵相关系统进行全面的分析研究,指出了润滑油进水的原因是,给水泵轴承和密封水采用的呼吸器易堵塞造成回油室为较大负压状态。给水泵转速变化时,低压密封水室压力轻微波动,微正压的水进入微负压的回油室,造成油中微量带水。经过分析研究提出改进建议,运行后取得了较好效果,汽动给水泵组的油中含水量大幅降低,保证了机组安全稳定运行。     

环保新标准的循环流化床锅炉改造分析

对循环流化床在脱硝、脱硫和除尘等方面环保技术路线进行了分析,权衡各项技术的利弊及经济因素,结合新颁布的火电厂大气污染物排放标准(GB 13223—2011),做出如下建议:半干旋转喷雾法脱硫工艺(SDA)和SCR结合使用后,氮氧化物的脱除效率可达到95%,循环流化床中高灰分的环境不适合使用SCR,SNCR的脱除效率虽然相对较低,但是通过调整还原剂的停留时间和与烟气的混合程度,脱硝效率可达70%以上,完全可以满足新环保标准的要求;石灰石-石膏湿法脱硫技术成熟,脱硫效率高,负荷适应性好,在循环流化床炉内脱硫的基础上外加该工艺,可以保证足够的脱硫效率;电袋组合式除尘器发挥了两种除尘器的技术优势,可以达到新标准的要求。     

300MWCFB锅炉配套半干法烟气脱硫的汞排放试验研究

某300 MW循环流化床(CFB)锅炉采用炉内脱硫、SNCR、预电除尘器和烟气循环流化床半干法脱硫装置实现了超低排放。对不同工况下不同位置的烟气汞浓度和灰渣等固体副产物中的汞含量进行测试分析,研究结果表明:燃煤在循环流化床锅炉燃烧产生的汞主要以气态汞和颗粒汞形式存在;锅炉负荷提高,烟气中气态汞和颗粒汞浓度均有所提高,炉内脱硫对原始汞排放特性几乎没有影响;烟气循环流化床半干法脱硫装置可脱除71%～77%的气态汞和86%～88%的颗粒汞;采用预电除尘器与烟气循环流化床半干法脱硫结合的超低排放路线,总汞脱除率可达到82%～87%,使烟囱排放的汞浓度不高于1.5μg/m~3。副产物分析结果表明,烟气中脱除的汞主要富集于粉煤灰和半干法脱硫灰中。     

高海拔地区大型循环流化床锅炉特性研究

结合青海盐湖工业股份有限公司供热中心4×480 t/h循环流化床(CFB)锅炉的启动调试,通过理论论证及实际应用,对高海拔地区大型循环流化床锅炉特性进行研究,解决了低气压地区流化床锅炉高负荷工况下频繁结焦问题。给出了流化床锅炉正常运行所要维持的流化风速范围,明确了高海拔地区循环流化床锅炉流化风速计算应选用标态风量,与低海拔地区一致,使得此类技术具备实际可参考性及可操作性,对解决同类型问题有一定的参考价值。     

210 MW CFB燃烧石煤的可行性研究

为合理、高效综合利用石煤资源发电及灰渣提钒,在210 MW CFB(循环流化床)锅炉上进行石煤实炉试烧试验。结果表明:试验最大掺烧比例为石煤∶无烟煤=78∶22,对应入炉燃料热值在7.96~9.63 MJ/kg。锅炉能连续稳定运行,充分验证了利用CFB锅炉燃烧石煤燃料发电的可行性。试验分析了低热值石煤独有的燃烧特性,为工程项目设计建设提供了准确可靠的试验数据。     

循环流化床燃用半焦SNCR脱硝特性试验研究

为了检验循环流化床锅炉燃用半焦时选择性非催化还原（SNCR）脱硝技术的特性,在2 MW环形炉膛循环流化床试验台上开展了SNCR脱硝特性试验研究,考察了氨水和尿素溶液2种脱硝剂在不同的旋风分离器温度（反应温度）和氨氮摩尔比（NSR）时的脱硝特性。研究结果表明：循环流化床燃烧半焦时采用SNCR脱硝技术,可有效地降低烟气中氮氧化物（NOx）排放质量浓度,氨水作为脱硝剂的效果优于尿素溶液,氨水溶液SNCR反应温度为921 ℃（NOx初始排放质量浓度为350 mg/Nm 3）,NSR达到1.77时,NOx排放质量浓度为93 mg/Nm 3,达到了国标要求;尿素溶液SNCR反应时NH3逃逸量相比氨水SNCR反应时小,但是有较高的N2O排放浓度,这2种脱硝剂的脱硝反应特性存在差异;反应温度对SNCR脱硝特性影响明显,在反应温度为833 ℃时,氨水脱硝效率较低,而尿素溶液则无脱硝效果,在反应温度为871 ℃和921 ℃时,氨水和尿素溶液均能表现出较高的脱硝效率;随着NSR提高,脱硝效率提高,但是氨逃逸和N2O的排放浓度也都增加。     

330 MW循环流化床锅炉炉膛壁面颗粒浓度分布测量

循环流化床(CFB)锅炉炉膛内固体颗粒浓度对炉膛水冷壁传热、炉内温度分布和受热面磨损影响较大。在某台亚临界330 MW机组CFB 锅炉炉膛水冷壁上开设测孔,利用颗粒取样抽屉装置对炉膛内的局部颗粒浓度进行测量,研究炉膛近水冷壁区域的颗粒浓度水平分布。结果表明,在距离壁面1m范围内,颗粒浓度随着与壁面距离的增加而减小,相同高度的中心区内颗粒浓度基本保持不变;测孔所在高度越高,颗粒浓度越小;炉膛空截面风速的增加将使炉膛上部测孔的颗粒浓度增加;回归得到近壁面颗粒浓度水平分布关联式,利用关联式计算近壁面颗粒浓度误差小于20％。     

The effect of biomass co-combustion in a CFB boiler on solids accumulation on surfaces of P91 steel tube samples

The paper describes the results of industrial tests associated with the co-combustion of biomass and agromass with coal and focused on diagnostics and assessment of the effect of fuel type on the accumulation of solids on the surface of P91 steel tube samples placed in the vicinity of steam superheater in a commercial large-scale (over 400 MW) circulating fluidized bed boiler.Analysis of samples indicated the effect of fuel type, as well as the location of the area on the steel tube on the rate of solids accumulation. Alkali compounds were quite uniformly distributed at both front and rear sections of the steel tube samples, while calcium and sulfur components were mainly found in the front area. The average solids accumulation rates calculated for the rear areas of P91 steel tube samples were roughly two times higher than those for the front ones. The highest solids accumulation rate on the front area (1.04·10⁻⁹ ms⁻¹) was calculated for the case of agromass co-combustion with coal.