生物质无轴螺旋连续热解装置送料器设计及中试

为解决有轴螺旋送料器存在质量大、能耗高、易产生机械干涉等问题,该文设计了送料能力为150 kg/h的生物质无轴螺旋送料器,并以稻壳为原料开展了冷态输送和热解试验。设计的无轴螺旋送料器关键尺寸为:螺旋外径为400 mm、螺旋轴径为80 mm、螺距为200 mm,送料器采用柴油燃烧机和热解气回烧的方式加热,计算出燃烧机需要提供的功率为95.43 k W。稻壳冷态输送试验表明,当送料频率为50 Hz即无轴螺旋的转速为2.03 r/min时,无轴螺旋送料器输送稻壳的送料量为224.3 kg/h150 kg/h,无轴螺旋送料器的实际送料量高于理论计算值。稻壳热解试验表明,当加热腔最高温度为(700±50)℃时,随着热解时间增加,稻壳炭的挥发分质量分数由22.45%减至13.6%,灰分质量分数由29.38%增至33.44%,固定碳质量分数由48.17%增至52.96%。稻壳炭的高位热值随热解时间增加而增加,但在试验范围内增幅不大。热解时间对生物炭品质影响较大,即传热速率是限制大型连续热解反应器处理效率提高的主要因素,因此,在工业化应用的大型热解反应器的设计中,应着重考虑提高热解传热效率的方法。

Design and pilot test for feeder of biomass shaftless screw continuous pyrolysis device

Biomass continuous pyrolysis is a promising technology of biomass energy utilization. The technology has a lot of advantages, for example, the device applied in the technology is simple, can run continuously and stably, which is easy to be widely used, reaction conditions are easy to control, the efficiency is high. Continuous feeder is one of the core components of continuous pyrolysis reactor, which is generally a screw feeder, but shaft screw feeder of continuous pyrolysis reactor has problem of high energy consumption because of its high weight. What's more, it is easy to interference between screw and cylinder wall so that the device often need to stop and repair. It is difficult to operate continuously, which leads to low efficiency. However, these problems can be solved by applying shaftless screw to continuous pyrolysis reactor. The design of shaftless screw feeder with feeding capacity of 150 kg/h was introduced in this paper. Rice husk was used to carry out transport tests at room temperature and pyrolysis tests at the temperature of (700±50)℃ to study its feeding characteristic and pyrolysis characteristic. Shaft diameter, outside diameter, pitch of helix of the screw without shaft is 80, 400, 200 mm respectively. The distance between the outer diameter of the screw and the wall of the pipe is 20 mm. The diameter of pyrolysis tube is 456 mm and the thickness of pyrolysis tube's wall is 8 mm. What's more, a diesel combustion engine was used to produce heat for the feeder. The power of the diesel engine ranged from 58 to 116 kW. In addition, a motor was used to drive shaftless screw rotation, its main technology parameters: power rating: 5.5 kW, rated speed: 1450 r/min, reduction ratio: 29. Test results showed that When the transport frequency was 50 Hz, the feeding amount of screw feeder without shaft was 224.3 kg/h>150 kg/h. Obviously, the actual feeding amount of screw feeder was higher than the theoretical value. Rice husk was filled in the shaftless screw feeder densely due to the extruding effect of shaftless screw in the process of conveying. Continuous pyrolysis experiments of rice husk under different pyrolysis time were conducted in the case that the maximum temperature of heating chamber was 700℃ . With the pyrolysis time increased, the volatile content of rice husk char decreased from 22.45% to 13.6%, the ash content increased from 29.38% to 33.44%, and the fixed carbon content increased from 48.17% to 52.96%. According to the results of industrial analysis of rice husk carbon, most of the volatiles in rice husk have been released. In addition, the pyrolysis time has a slight influence on the calorific value of rice husk char. The high calorific value of rice husk char increased from19.307 MJ/kg to 20.821 MJ/kg with the increase of pyrolysis time. Thus, the shaftless screw feeder designed in this paper reached the requirements, providing design basis for industrial application of biomass continuous pyrolysis reactor.