废弃秸秆等生物质低能耗非相变秒级干燥

doi:10.11949/0438-1157.20240212

摘要/Abstract

摘要：

自主研发并设计搭建了生物质非相变旋流干燥的小试和中试实验装置。小试实验结果表明，在最佳干燥条件下秸秆含水率可从68%降至15%左右，脱水效率可达70%以上，放大规模的实验在中试装置上进行了验证。仿真模拟研究揭示了旋流场内切向、径向和轴向速度对固液分离的影响。理论计算结果表明干燥过程脱除的水分中有64.81%以非相变液滴形式脱离，说明非相变在干燥过程中占主要地位。机理研究表明水分可从生物质孔道中分离，这是由于生物质在旋流场中发生自公转耦合运动，导致其表面形成孔道，使水分以微液滴形式脱除。此外还对玉米胚芽、酒糟、木屑等生物质进行了实验，均达到接近70%的脱水效率，证明了该技术对生物质种类的普适性。

关键词: 生物质, 干燥, 旋风分离器, 计算流体力学, 低能耗

Abstract:

Aiming at the problem of high energy consumption in traditional biomass drying, a low energy consumption non-phase transition second drying method was proposed to overcome the latent heat of phase transition. The 2 kg/h pilot test and 84 kg/h pilot test equipment of biomass non-phase change drying were independently developed, designed and built. The experimental results show that the drying conditions of straw with particle size 1—5 mm are 80℃, gas-solid ratio 9.75, gas velocity 18 m/s, residence time 10—30 s, water content can be reduced from 68% to the lowest about 15%, and the dehydration efficiency can reach more than 70%. The scaled up experiment was verified on the pilot plant. The effects of tangential, radial and axial velocities on solid-liquid separation in swirl field are revealed. In addition, 64.81% of the water removed in the drying process was removed in the form of non-phase change droplets, indicating that non-phase change plays a dominant role in the drying process. The changes of particle surface morphology before and after straw drying and the further mechanism study showed that water could be separated from the pore, which may be due to the microinterface oscillation induced by the self-rotating coupling of biomass particles in the swirl field, and the pore was created on the surface of the biomass particles to enhance the centrifugal force effect to remove water in the form of microdroplets. In addition, experiments on biomass such as corn germ, distilling grains and wood chips were carried out. Under the conditions of 100℃, atmospheric pressure and residence time of 30 s, the dehydration efficiency of nearly 70% was achieved, which proved the universality of the technology for biomass types.

Key words: biomass, drying, cyclone separator, computational fluid dynamics, low energy consumption

中图分类号:

TQ 35

张香港, 常玉龙, 汪华林, 江霞. 废弃秸秆等生物质低能耗非相变秒级干燥[J]. 化工学报, 2024, 75(7): 2433-2445.

Xianggang ZHANG, Yulong CHANG, Hualin WANG, Xia JIANG. Low energy consumption non-phase change second drying of waste straw and other biomass[J]. CIESC Journal, 2024, 75(7): 2433-2445.

图/表 16

表1 常见的热干化技术对比分析［18］

Table 1 Comparative analysis of common sludge thermal drying technologies［18］

技术类型	干燥效率	能耗水平	时间	应用阶段	成熟度	热媒温度
旋转鼓式干燥机	高	中等	短	工业规模	高	150~400℃
流化床干燥机	中等	低	中等	工业/小规模	中等	100~200℃
喷雾干燥机	高	高	短	工业规模	高	200~300℃
微波干燥机	高	中等	短	实验室规模	中等	50~150℃
真空干燥机	中等	中等	长	实验室/小规模	中等	50~100℃
红外干燥机	中等	低	短至中等	小规模	中等	100~200℃

图1 生物质非相变干燥过程

Fig.1 Schematic diagram of non-phase change drying of biomass

图2 非相变旋流干燥装置[21]

Fig. 2 Non-phase change cyclone drying device[21]

表2 实验中的主要仪器与设备

Table 2 Main instruments and equipment of experiment

实验仪器	型　号	生产公司
鼓风干燥箱	DHG-9145A	上海泰坦科技股份有限公司
分析天平	BSA124S	德国赛多利斯公司
扫描电镜	HITACHI SU5000+	日本日立公司
超声仪	KH800KDE	昆山禾创超声仪器有限公司
水浴锅	DF-101S	北京科伟永兴仪器有限公司

图3 (a) 模型网格图；(b) 不同网格密度条件下旋流器柱锥连接面上一条直径上的切向速度对比

Fig.3 (a) Grid of model; (b) Comparison of tangential velocity distribution along a diameter in cylinder and cone connection surface at different mesh density

图4 不同载气温度对秸秆干燥效果的影响

Fig.4 Effect of different carrier gas temperature on drying effect of straw

图5 不同气固比对秸秆干燥效果的影响

Fig.5 Effect of different gas-solid ratio on drying effect of straw

图6 不同载气气速对秸秆干燥效果的影响

Fig.6 Effect of different carrier gas velocity on drying effect of straw

图7 秸秆非相变干燥中试实验结果

Fig.7 Experimental results of non-phase change drying of straw

表3 不同类型生物质的物理特性以及干燥效果

Table 3 Physical properties and drying effects of different types of biomass

生物质名称	初始含水率/%	密度/（kg/m³）	粒径/mm	脱水效率/%
酒糟	67.8	650	0.5~1.0	69.4
木屑	55.3	200	1.0~2.5	70.2
玉米胚芽	60.0	300	1.0~3.0	68.7
市政污泥	80.0	1000	0.1~5.0	63.8

图8 不同高度下CFD模拟30~60 m3/h气量范围流体速度分布曲线

Fig.8 CFD simulation of fluid velocity distribution curves in gas volume range of 30—60 m3/h at different altitudes

图9 CFD模拟云图

Fig.9 CFD simulation cloud image

图10 不同粒径颗粒角速度对比

Fig.10 Comparison of rotation speed of different diameter particles

图11 非相变旋流干燥对生物质表面形貌的影响

Fig.11 Effect of non-phase change cyclone drying on biomass surface morphology

表4 非相变水分比例计算基本参数

Table 4 Basic parameters for calculating proportion of non-phase change moisture

参数	数值
处理量，G/（kg/h）	84
初始含水率，n₁/%	68
剩余含水率，n₂/%	19.11（40 s）
环境空气温度,T₀/℃	25
入口载气温度,T₁/℃	90
出口载气温度,T₂/℃	40
初始物料温度,T_m1/℃	25
干燥后物料温度,T_m2/℃	35
气量，Q/（m³/h）	1300

表5 两种干燥技术成本对比

Table 5 Cost comparison of two drying technologies

项目	非相变旋流干燥装置	管束式干燥装置
能耗	65.96 kW·h/t	耗电：26.37 kW·h/t；耗汽：1.118 t/t
成本	36.28 CNY/t	226.61 CNY/t
装置占地面积	约24 m²	约3600 m²

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