煤直接液化技术换代的化学反应问题

doi:10.11949/0438-1157.20250685

摘要/Abstract

摘要：

煤直接液化反应器大型化是提高转化效率和经济性的必然选择，前人针对大型液化反应器涉及的工程化难题进行了诸多研究，支撑了神华百万吨级工业装置的稳定运行以及二代技术的发展，但仍面临提高油收率的挑战。深入认识煤直接液化技术换代伴随的煤反应环境的变化及其对自由基反应的影响是提高油收率的基础。本文着重分析了神华煤直接液化两代技术中煤浆的温度分布和化学反应特征，尤其是分配盘下部的自由基反应，研判了二代技术环境下煤的反应时间及液化效率，论证了煤浆温度、溶剂循环比以及梯级升温对上湾煤和哈密富油煤自由基碎片生成和加氢速率匹配的影响，探讨了高温溶剂外循环所导致的热高分温度提升促进缩聚反应的原因，提出降低外循环溶剂的量或温度进而提高油收率、降低缩聚反应、提高装置稳定性的思路。

关键词: 煤直接液化, 分配盘, 自由基反应, 缩聚结焦

Abstract:

The Shenhua's direct coal liquefaction (DCL) technology has advanced from the first generation (1G) to the second generation (2G). This progress has overcome many engineering challenges encountered in the 1G technology, but scarcely addressed the environmental changes of coal from 1G to 2G that influence the kinetics of coal conversion, particularly with regard to the oil yield. This study examines the temperature distribution of coal in the liquefaction reactors, the changes in concentrations of coal and hydrogen donor solvent due to the alteration in the solvent recycle strategy, from internal recycle in the 1G to external recycle in the 2G, and as a result, the changes in radical reactions and oil yield. It shows that the reaction time as well as the concentrations of coal and hydrogen donor solvent in the 2G technology is lower than those in the 1G technology. These changes may lead to lower coal conversion and oil yield in 2G technology compared to the 1G technology.Reduce the amount or temperature of the external circulating solvent to improve oil yield, reduce condensation reactions, and enhance plant stability.

Key words: direct coal liquefaction, distribution tray, free radical reaction, condensation coking

中图分类号:

TQ 529.1

王元哲, 刘振宇, 闫玉新, 王丝语, 石磊, 刘清雅. 煤直接液化技术换代的化学反应问题[J]. 化工学报, 2025, 76(10): 5522-5532.

Yuanzhe WANG, Zhenyu LIU, Yuxin YAN, Siyu WANG, Lei SHI, Qingya LIU. Chemical reaction issues in the technological upgrading of direct coal liquefaction[J]. CIESC Journal, 2025, 76(10): 5522-5532.

图/表 13

图1 煤直接液化的反应路径示意

Fig.1 Reaction pathways in DCL process

图2 中国神华煤直接液化第一代技术流程示意[13-14]1—煤制氢装置;2—磨煤机;3—煤粉仓;4—混捏机;5—煤浆罐;6—进料泵;7—预热炉;8—第一反应器;9—第二反应器;10,11,17—强制循环泵;12—分离器;13—五通式减压阀;14—常压塔;15—减压塔;16—减底泵;18—加氢稳定反应器;19,21,22—分馏塔;20—加氢改质反应器

Fig.2 Schematic diagram of Shenhua first-generation DCL technology[13-14]1—coal hydrogen device; 2—coal mill; 3—coal bunker; 4—mixing machine; 5—coal slurry tank; 6—feed pump; 7—preheating furnace; 8—first liquefaction reactor; 9—second liquefaction reactor; 10, 11, 17—recirculating pump; 12—splitter; 13—five-way decompression valve; 14—atmospheric distillation tower; 15—vacuum distillation tower; 16—bottom pump; 18—hydrogenation stabilization reactor; 19, 21, 22—separation tower; 20—hydrogenation and upgrading reactor

表1 神华煤直接液化技术对比

Table 1 Comparison of Shenhua DCL technologies

对比项目	一代技术	二代技术
反应器形式及内部构造	浆态床/回流杯+ 中心管+循环泵	浆态床/无内构件
串联反应器台数	2	3
液化名义温度/℃	455	455
溶剂循环方式	内（小）循环	外（大）循环
热高分温度/℃	约420	约460

图3 煤直接液化一代和二代技术的反应单元对比

Fig.3 Comparison of reaction units in two generations DCL technologies

图4 煤直接液化一代和二代技术第一反应器内物料流动及浓度对比示意

Fig.4 Comparison of material flow and concentration in the primary reactor of two generations DCL technologies

表2 二代技术一反中反应物的平均浓度、平均反应速率及停留时间与一代技术的对比

Table 2 Comparison of the reactants’ mean concentration， mean reaction rates and residence time in the primary reactor of two generations DCL technologies

煤浆流量/(t/h)	循环比R	C_solid,2-1/C_solid,1-1	C_HDS,2-1/C_HDS,1-1	r_coal,2-1/r_coal,1-1	r_oil,2-1/r_oil,1-1	τ_coal,2-1/τ_coal,1-1	τ_coal,2-T/τ_coal,1-T
1170	0	1.0	1.00	1.00	1.0	0.74	1.11
1170	1	0.50	0.50	0.25	0.25	0.37	0.56
1170	2	0.33	0.33	0.11	0.11	0.25	0.38
1170	3	0.25	0.25	0.06	0.06	0.18	0.27

图5 神华煤直接液化一代技术反应器及温度测定位置

Fig.5 Reactors and temperature measurements of Shenhua’s first-generation DCL technology

表3 神华煤直接液化一代技术反应器内煤浆在内循环比R=3下的温度分布［14］

Table 3 Temperature distribution of coal slurry in the Shenhua’s first-generation DCL reactor under internal circulation ratio R=3［14］

测温点	第一反应器径向温度/℃					第二反应器径向温度/℃
测温点	1	2	3	4	平均	1	2	3	4	平均
A	465.3	465.5	466.1	466.7	465.9	460.4	461.9	462.1	462.1	461.6
B	462.4	463.4	463.0	464.4	463.3	459.6	460.9	460.6	461.3	460.6
C	459.5	460.1	460.0	461.5	460.4	458.9	459.6	460.0	460.0	459.6
D	456.8	458.3	458.4	458.3	458.0	457.8	458.6	458.7	459.0	458.5
E	454.6	456.9	456.1	456.0	455.9	457.2	458.2	457.9	457.6	457.7
F	453.6	456.2	453.4	452.8	454.0	455.8	456.5	457.0	456.7	456.5
G	452.4	453.1	449.5	451.1	451.5	454.7	455.9	456.3	455.4	455.6
H	447.7	448.4	447.3	447.5	447.7	453.4	455.1	455.1	454.7	454.6

图6 神华煤直接液化一代技术反应器中油煤浆温度的变化历程

Fig.6 The temperature profile of oil-coal slurry in reactors of Shenhua's first-generation DCL technology

表4 原料煤的元素分析和工业分析结果［20］

Table 4 Proximate and ultimate analyses of raw coals［20］

煤样	工业分析/%(mass)			元素分析/%(mass,daf)					摩尔比
煤样	M_ad	A_ad	V_daf	C	H	O^a	N	S	H/C	O/C
SW	1.5	5.2	30.1	77.6	4.8	16.6	0.8	0.2	0.75	0.16
NMH	4.8	5.3	47.1	67.0	5.4	26.3	0.9	0.4	0.97	0.29

图7 SW煤的自由基碎片参数在不同温度和供氢溶剂用量下数值（基于文献[20-21]数据计算的新参数）

Fig.7 The radical quantities of SW coal at different temperatures and HDS∶Coal ratios (Data extracted from Refs.[20-21])

图8 NMH煤的自由基碎片参数在不同温度和供氢溶剂用量下数值（基于文献[20-21]数据计算的新参数）

Fig.8 The radical quantities of NMH coal at different temperatures and HDS∶Coal ratios (Data extracted from Refs.[20-21])

图9 两段升温液化模式下的液体收率对比（数据来自文献[20]）(模式A表示420℃反应40 min;模式D表示420℃反应10 min后升温至455℃反应30 min;模式E表示455℃反应40 min)

Fig. 9 Comparison of liquid yields under two-stage heating liquefaction process (Data from Ref.[20])(Model A represents react at 420℃ for 40 min; Model D represents react 420℃ for 10 min and heat up to 455℃ and react for 30 min; Model E represents react at 455℃ for 40 min)

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