Modeling of the entrained flow gasification reactor under the synergistic action of ligniteoxidation and steam gasification

doi:10.16085/j.issn.1000-6613.2019-0180

Abstract

Abstract:

Shengli lignite was gasified at 800℃/900℃ under N₂, O₂, H₂O, H₂O+O₂ atmospheres in a simulated entrained-flow reactor (?80mm×3000mm). And kinetics of main reactions & flow characteristics of gas/solid were discussed, in order to build coal gasification model. The results showed that: the gas phase flow was divided into 3 zones, jet zone, recirculation zone and downstream zone, but the height of jet zone and recirculation zone only was 5% of that of reactor and could be neglected; pyrolysis and combustion occur simultaneously; the oxidation reaction (OR) and the steam gasification reaction (SGR) were controlled by membrane diffusion and chemical reaction respectively, and the rate equations derived from shrinking core model and reaction mechanism were in good agreement with experimental data. Moreover, the apparent rate constant of SGR in H₂O+O₂ atmosphere was obviously larger than that in H₂O atmosphere, especially at high temperature. It might be caused by that OR could produce microspores and develop mesopores to promote SGR rate, i.e. OR and SGR had synergistic effect. The model built was solved by MATLAB and employed to predict 12 groups of experiments (60 data points). And the predicted values were in good agreement with the experimental values, with the error of less than 20% for 85% predicted values and less than10% for 70% predicted values. For the prediction of lignite conversion rate, the predicted values were in perfect agreement with the experimental values, with the error of less than 4.6% for 75% predicted values.

Key words: entrained-flow reactor, synergistic action, flow characteristics, membrane diffusion, dynamics, model

摘要：

为了建立?80mm×3000mm下行夹带流煤气化反应器模型，以胜利褐煤为原料，在该反应器中进行了N₂、O₂、H₂O、H₂O+O₂气氛下800℃/900℃气化实验，研究了流场分布、主要反应发生区域，并结合反应机理和缩合模型推导了不同速控步/气化气氛下C-O₂氧化和C-H₂O气化速率方程。结果发现，实验条件下，喷嘴附近的射流区及其周围的回流区仅占反应器高度的5%，气相主要以平推流流动；热解和燃烧反应同时发生，反应器分为热解燃烧区和气化区；气膜扩散控制下的C-O₂氧化速率方程和化学反应控制时C-H₂O气化速率方程与实验数据吻合较好；相对H₂O气氛，H₂O+O₂气氛下C-H₂O气化反应的表观气化反应速率常数明显较大，尤其在高温下，建模时需分别考虑H₂O和H₂O+O₂气氛下气化速率。这主要是由于氧化反应的开孔/扩孔作用使碳颗粒微孔数量、比表面积、孔容增加，促进了C-H₂O气化反应。采用MATLAB编程拟合求解模型中未知参数和模型，对12组实验（60个数据点）进行预测，85%预测值误差小于20%，70%预测值误差小于10%。对褐煤转化率的预测，75%预测值误差小于4.6%。建立的反应器模型误差较小，为反应器设计和放大奠定基础。

关键词: 气流床, 协同作用, 流动特点, 气膜扩散, 反应速率, 模型

CLC Number:

TQ53

Xianglong CHENG,Jinju GUO,Haiyong ZHANG,Jialiang SUN,Yanbing ZHANG,Chengjian SONG. Modeling of the entrained flow gasification reactor under the synergistic action of ligniteoxidation and steam gasification[J]. Chemical Industry and Engineering Progress, 2020, 39(1): 119-128.

程相龙,郭晋菊,张海永,孙加亮,张延兵,宋成建. 褐煤氧化和气化反应协同作用下夹带流反应器的建模[J]. 化工进展, 2020, 39(1): 119-128.

Figures/Tables 18

工业分析/%					元素分析/%
M_ad	A	V	FC		C	H	S	O^a N
5.89	9.87	36.23	53.90		62.26	6.12	0.66	29.85 1.11

方程系数										变量	矩阵积
C_char	0.75	0.8	0.43	0.27	C_tar	0	0	0	0	CHAR	C_lignite
H_char	0.25	0.2	0	0	H_tar	1	0.11	0.18	0.06	CH₄	H_lignite
O_char	0	0	0.57	0.73	O_tar	0	0.89	0	0	C₂H₆	O_lignite
N_char	0	0	0	0	N_tar	0	0	0.82	0	CO	N_lignite
S_char	0	0	0	0	S_tar	0	0	0	0.94	CO₂	S_lignite
1	0	0	0	0	0	0	0	0	0	TAR	1-VOL
0	1	0	0	0	0	0	0	0	0	H₂	1.19 H_lignite
0	0	1	0	0	0	0	0	0	0	H₂O	1.17 H_lignite
0	0	0	1	0	0	0	0	0	0	NH₃	0.31 O_lignite
0	0	0	0	1	0	0	0	0	0	H₂S	0.14O_lignite

水蒸气体积分数/%	K₁	K₂
25	0.031	1.111
35	0.030	0.799

温度/℃	H₂O体积分数/%	K₁
温度/℃	H₂O体积分数/%	H₂O气氛	H₂O+1% O₂气氛
800	25	0.031	0.096
800	35	0.030	0.084
900	25	0.006	0.256
900	35	0.008	0.251

水蒸气	H₂O气氛			H₂O+1% O₂气氛
水蒸气	总孔容/cm³?g^-1	微孔容/cm³?g^-1	比表面积/cm²?g^-1	总孔容/cm³?g^-1	微孔容/cm³?g^-1	比表面积/cm²?g^-1
25% H₂O	0.0373	0.0044	10.6599	0.2393	0.1701	345.852
35% H₂O	0.0431	0.0045	10.8629	0.2446	0.1852	391.266

反应	速率方程	参考文献
C+CO₂ $→$ 2CO^①	$r = 1 1 / k d i f f + 1 / k r Y 2 + 1 / k d a s h (1 / Y - 1) P C O 2$ $k r = 247 e x p (- 21060 / T) k d i f f = 7.45 × 10 - 4 (T / 2000) 0.75 / (P · d p) Y = [(1 - x) / (1 - f)] 1 / 3$	Dobner^[30]
C+2H₂ $→$ CH₄	$r = 1 1 / k d i f f + 1 / k r Y 2 + 1 / k d a s h (1 / Y - 1) (P H 2 - P C H 4 / K e q)$ $k r = 0.12 e x p (- 17921 / T) k d i f f = 1.33 × 10 - 3 (T / 2000) 0.75 / (P · d p) k e q = 5.12 × 10 - 6 e x p (18400 / 1.8 T) Y = [(1 - x) / (1 - f)] 1 / 3$	Wen和Chuang^[18]
CO+H₂O $→$ CO₂+H₂	$r C O = δ 1 (2.77 × 105) (y c o - y c o ①) e x p (- 27760 / 1.987 T) × P (0.5 - P / 250) e x p (- 8.91 + 5553 / T) y c o ① = y C O 2 × y H 2 / (K e p y H 2 O) / P K e p = e x p [- 3.6893 + 7234 / (1.8 T)] δ = 0 . 28 ①$	Singh和Saraf^[31]
CO+3H₂ $→$ H₂O+CH₄	$r H 2 = δ × k 0 × e x p (- E / R T) [H 2] 0.5 [C O] 0.5$	于建国等^[32]
Y+O₂ $→$ H₂O+CO₂	$r = q e x p (- 99760 / R T) [Y] [O 2]$ ^①	岑可法等^[33]

反应	速率方程	参考文献
C+CO₂ $→$ 2CO^①	$r = 1 1 / k d i f f + 1 / k r Y 2 + 1 / k d a s h (1 / Y - 1) P C O 2$ $k r = 247 e x p (- 21060 / T) k d i f f = 7.45 × 10 - 4 (T / 2000) 0.75 / (P · d p) Y = [(1 - x) / (1 - f)] 1 / 3$	Dobner^[30]
C+2H₂ $→$ CH₄	$r = 1 1 / k d i f f + 1 / k r Y 2 + 1 / k d a s h (1 / Y - 1) (P H 2 - P C H 4 / K e q)$ $k r = 0.12 e x p (- 17921 / T) k d i f f = 1.33 × 10 - 3 (T / 2000) 0.75 / (P · d p) k e q = 5.12 × 10 - 6 e x p (18400 / 1.8 T) Y = [(1 - x) / (1 - f)] 1 / 3$	Wen和Chuang^[18]
CO+H₂O $→$ CO₂+H₂	$r C O = δ 1 (2.77 × 105) (y c o - y c o ①) e x p (- 27760 / 1.987 T) × P (0.5 - P / 250) e x p (- 8.91 + 5553 / T) y c o ① = y C O 2 × y H 2 / (K e p y H 2 O) / P K e p = e x p [- 3.6893 + 7234 / (1.8 T)] δ = 0 . 28 ①$	Singh和Saraf^[31]
CO+3H₂ $→$ H₂O+CH₄	$r H 2 = δ × k 0 × e x p (- E / R T) [H 2] 0.5 [C O] 0.5$	于建国等^[32]
Y+O₂ $→$ H₂O+CO₂	$r = q e x p (- 99760 / R T) [Y] [O 2]$ ^①	岑可法等^[33]

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