Design and optimization of cryogenic air separation process with dividing wall column based on self-heat regeneration

doi:10.11949/0438-1157.20230240

Abstract

Abstract:

Industrial gases commonly obtained by cryogenic distillation are widely used currently. The energy consumption of the process is always huge, and the energy consumption of compression and rectification accounts for the largest proportion. A cryogenic air separation process with a dividing wall column was proposed based on the self-heat regeneration, in which the double-tower distillation air separation process was replaced by a single-tower distillation process applying the self-heat regeneration technology to complete the process of heat exchange. The energy of the process was analyzed by the pinch principle, and the total energy consumption (TEC), carbon dioxide emissions ([CO₂]_em), and total annual cost (TAC) were evaluated, respectively. The results showed the cryogenic air separation process based on the self-heating regeneration in the dividing wall column reduced energy consumption for oxygen production by 26.19%, CO₂ emission by 25.18%, and the TAC by 31.93%. The optimized air separation process using self-heat regeneration technology and dividing wall column technology has shown stronger advantages in energy saving, economy, and environmental protection.

Key words: self-heat regeneration, dividing wall column, air separation, computer simulation, optimal design, systemic energy saving

摘要：

工业气体应用广泛，当前常用深冷精馏法获取，工艺能耗巨大，其中压缩和精馏部分的耗能占比最大。基于自热再生和隔壁塔技术，提出了一种隔壁塔深冷空分方案，用单塔精馏空分过程代替双塔精馏空分过程，利用自热再生优化过程换热。利用夹点原理对优化前后的工艺进行能量分析，并从总能量消耗（TEC）、二氧化碳排放量（[CO₂]_em）、年度总费用（TAC）三个角度分别进行评价。结果表明，基于自热再生的隔壁塔深冷空分工艺较常规空分工艺，制氧消耗降低了26.19%，二氧化碳排放减少了25.18%，年度总费用降低了31.93%。利用自热再生技术和隔壁塔技术优化后的空分工艺，在节能、经济以及环保方面表现出更强的优越性。

关键词: 自热再生, 隔壁塔, 空气分离, 计算机模拟, 优化设计, 系统节能

CLC Number:

TQ 015.2

Zhaolun WEN, Peirui LI, Zhonglin ZHANG, Xiao DU, Qiwang HOU, Yegang LIU, Xiaogang HAO, Guoqing GUAN. Design and optimization of cryogenic air separation process with dividing wall column based on self-heat regeneration[J]. CIESC Journal, 2023, 74(7): 2988-2998.

文兆伦, 李沛睿, 张忠林, 杜晓, 侯起旺, 刘叶刚, 郝晓刚, 官国清. 基于自热再生的隔壁塔深冷空分工艺设计及优化[J]. 化工学报, 2023, 74(7): 2988-2998.

Figures/Tables 18

Table 1 Feeding conditions of raw materials

温度/℃	压力/kPa	空气处理/（m³/h,标准工况）	组成/%（mol）
温度/℃	压力/kPa	空气处理/（m³/h,标准工况）	氮气	氧气	氩气
25	101	166900	0.7809	0.2095	0.0096

Fig.1 Process flowsheet of conventional double-tower distillation air separation process

Table 2 Parameters of traditional air separation distillation column

参数	上塔	下塔	粗氩塔	精氩塔
理论级数	55	35	80	38
进料位置	1/8/22/25/28/33/55	1/35	1/80	1/38
产品抽出位置	1/23/28/55	1/21/35	1/80	1/38
塔顶温度/℃	-192.17	-178.04	-191.64	-192.17
塔底温度/℃	-179.33	-174.27	-185.65	-182.00
操作压力/kPa	150	540	150	150

Fig.2 T-Q diagram of conventional double-tower distillation based air separation process

Fig.3 Partial distillation stage diagram of air separation process

Fig.4 Process flowsheet of single-tower distillation based air separation process in dividing wall column

Fig.5 Influence of extraction position of side line of crude argon gas on product purity in process

Fig.6 Influence of extraction position of side line of polluted nitrogen gas on product purity

Fig.7 Influence of the number of crude argon tower trays on product purity

Fig.8 Influence of the number of pure argon tower trays on product purity

Fig.9 Influence of the number of main distillation tower trays on product purity

Fig.10 Flow chart of air separation optimization in dividing wall column

Fig.11 Influence of production position of crude argon side line on annual total cost

Fig.12 Influence of lateral production location of polluted nitrogen on annual total cost

Table 3 Analysis of economic optimization results of single-tower distillation based air separation process in dividing wall column

参数	数值
N_VR	23
N_WN	9
N_T1	110
N_T2	70
N_T3	38
TAC/ $(10^{6} U S D / a)$	10.06

Table 3 Analysis of economic optimization results of single-tower distillation based air separation process in dividing wall column

参数	数值
N_VR	23
N_WN	9
N_T1	110
N_T2	70
N_T3	38
TAC/ $(10^{6} U S D / a)$	10.06

Fig.13 T-Q diagram of single-tower distillation based air separation process with dividing wall column

Table 4 Comparison of design parameters

产品名称	产量/(m³/h,标准工况)			纯度/%
产品名称	企业生产数据	常规双塔空分	隔壁单塔空分	纯度/%
空气	165800	166900	166900	—
氧气	30000	34800	34900	>99.6
氮气	17350	63000	63000	>99.99
氩气	670	1030	1100	>99.999
制氧能耗/ (kW∙h/m³,标准工况)	0.43	0.42	0.31	—

Table 5 Comparison of simulated result

参数	常规双塔空分	隔壁单塔空分
精馏塔费用/(10⁵ USD/a)	3.09	3.96
换热器费用/(10⁶ USD/a)	4.87	1.95
压缩机费用/(10⁶ USD/a)	9.61	7.73
总投资费用/(10⁷ USD/a)	3.10	2.77
总运行费用/(10⁷ USD/a)	1.09	0.66
压缩机能耗/kW	14470	10827
冷却器能耗/kW	12325	6194
总耗能 $T E C$ /kW	43410	32481
二氧化碳排放量/(kg/h)	4078	3051
年度总费用TAC/(10⁶ USD/a)	14.78	10.06
设备折旧年限/a	8	8

Table 5 Comparison of simulated result

参数	常规双塔空分	隔壁单塔空分
精馏塔费用/(10⁵ USD/a)	3.09	3.96
换热器费用/(10⁶ USD/a)	4.87	1.95
压缩机费用/(10⁶ USD/a)	9.61	7.73
总投资费用/(10⁷ USD/a)	3.10	2.77
总运行费用/(10⁷ USD/a)	1.09	0.66
压缩机能耗/kW	14470	10827
冷却器能耗/kW	12325	6194
总耗能 $T E C$ /kW	43410	32481
二氧化碳排放量/(kg/h)	4078	3051
年度总费用TAC/(10⁶ USD/a)	14.78	10.06
设备折旧年限/a	8	8

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