掺混煤液化残渣萃余物对煤粉加压输送的影响规律

Characteristics of high pressure dense-phase pneumatic conveying of pulverized coal blending extract residue of direct coal liquefaction residue

将煤液化残渣萃余物(以下简称萃余物)掺混到煤粉中进行共气化是萃余物大规模资源化利用的一种方式,实现萃余物与煤共气化首先要保证该混合物料的加压密相输送过程的稳定及可控。为研究萃余物掺混到煤粉后的加压密相输送规律,针对某气化装置的原料煤粉及该煤粉掺混20%萃余物的混合粉体,首先采用HR指数和FF函数表征方法对两种粉体的流动性进行比较分析,并结合粉体的扫描电镜照片来分析颗粒微观结构对粉体流动性的影响,然后在25 mm内径输送管道中,进行背压(接收罐压力)4和2 MPa的加压密相输送实验研究,获取粉体质量流量和质量浓度随表观气速变化的输送操作规律,最后以粉体质量流量和水平直管段压差的平均波动和最大波动幅度作为输送稳定性的评价标准,通过大数据分析得到掺混萃余物对粉体输送稳定性的影响规律。结果表明:HR指数和FF函数表征方法均说明掺混20%萃余物会导致粉体的流动性变差;在相同表观气速下,高背压4 MPa下掺混20%萃余物对粉体输送过程的质量流量影响较小,而低背压2 MPa下掺混20%萃余物则会导致粉体输送的质量流量降低;在低表观气速区,掺混20%萃余物会导致输送过程中的粉体质量浓度降低,当表观气速增大至临界气速后,输送混合粉体和煤粉时管道内颗粒的质量浓度相近;当表观气速低于4 m/s时,掺混20%萃余物的粉体输送稳定性不如煤粉,当表观气速增大至4 m/s后,混合粉体的输送稳定性提高至煤粉输送同一水平,其质量流量平均波动幅度小于4%,最大波动幅度小于15%,水平直管段压差平均波动幅度小于8%,最大波动幅度小于40%。

Mixing the Extraction Residue of Direct Coal Liquefaction Residue(ER)into pulverized coal as fuels for co-gasification processes demonstrates a way of multi-utilization of the ER waste.But the stability and controllability of the pneumatic conveying process of this new mixture has not been studied yet.In order to investigate on the pneumatic conveying characteristics of this mixture,the pure pulverized coal and the mixture which contains of 80%pulverized coal and 20%ER were prepared as experiment samples.The fluidity of these two samples was firstly evaluated by the Hausner Ratio(HR)and Flow Function(FF)method,with their microscopic structures analyzed using SEM(Scanning Electron Micrographs).Then the high pressure dense-phase pneumatic conveying experiments were conducted at back pressure of 4 and 2 MPa,with conveying pipe diameter of 25 mm.During the experiment,the relationship between conveyed mass flowrate particles concentration and superficial gas velocity were analyzed.The stability of conveying process was evaluated with the fluctuations level of the particles mass flowrate and pressure drop of horizontal pipe,the maximum and the averaged fluctuation level of these two measured values were calculated and recorded.Results showed that the fluidity of the coal particles blended with ER became worse when comparing to the pulverized coal,evaluated by both HR and FF functions.When conveying at same superficial gas velocity,the measured mass flowrate of the mixture is similar to the pulverized coal at a high back pressure level(4 MPa),while decreases when the back pressure level drops to a lower level(2 MPa).When conveying under a same pressure level,the mixture showed a poor concentration rate compared to the pulverized coal at low superficial gas velocity,while they performed a similar concentration rate when superficial gas velocity above the critical gas velocity.In general,when the superficial gas velocity was lower than 4 m/s,the mixture of coal particles blended with 20% ER performed a poor stability compared to the pure pulverized coal.When the superficial gas velocity above 4 m/s,this two particles performed a same stability level with the mean fluctuation of mass flow rate less than 4%,the maximum fluctuation less than 15%and the mean fluctuation of pressure drop at horizontal pipe section less than 8%and maximum fluctuation less than 40%.