Comparison of conventional and novel high-pressure NGL recovery processes

doi:10.16085/j.issn.1000-6613.2018-1994

Abstract

Abstract:

Large-scale high-pressure condensate gas fields such as Yingmai and Dina in the Tarim Basin area currently only simply control the dew and hydrocarbon point for the feed natural gas. The recovery rate of heavy hydrocarbons is very low and the economic benefits are not maximized. Taking NGL (natural gas liquid) recovery for gas fields can significantly increase the economic benefits of these fields. Nowadays, HPA (high pressure absorber) process is widely used to recovery NGL for high-pressure natural gas. In this paper two improved processes based on HPA process were proposed: revised type Ⅰ process and revised type Ⅱ process. SQP（sequential quadratic programming） algorithm was selected to optimize the operating parameters of the three processes with the lowest unit energy consumption as the objective function. The energy consumption analysis showed that the three processes had different adaptation range of feed gas richness and pressure. Under lean conditions the revised type Ⅰ process was more energy efficient than HPA process in the range of feed gas pressures of 7000—8000kPa. When the feed gas pressure was higher than 7500kPa, the energy consumption of revised type Ⅱ process started to be lower than the former two, and with the increase of feed gas pressure, the energy saving of revised type Ⅱ process was more obvious. For rich gas, revised type Ⅱ process had the highest energy consumption and the difference between revised type Ⅰ process and HPA processes was not apparent.

Key words: high-pressure NGL recovery, process improvement, process optimization, energy consumption analysis

摘要：

塔里木盆地地区的英买、迪那等大型高压凝析气田目前仅对原料天然气进行了烃水露点控制，重烃回收率低，经济效益没有实现最大化，对此类气田进行凝液回收可显著提升气田的经济效益。现今适用于高压天然气凝液回收的流程主要为HPA（high pressure absorber）流程，本文在HPA流程基础上提出两种改进流程，即改进Ⅰ型流程和改进Ⅱ型流程。并通过SQP（sequential quadratic programming）算法以单位能耗最低为目标函数对3种流程进行操作参数优化, 并通过能耗分析表明：3种流程具有不同原料气贫富和压力适应范围，在贫气条件下，原料气压力在7000~8000kPa范围内，改进Ⅰ型比HPA流程更节能，而当原料气压力高于7500kPa时，改进Ⅱ型流程能耗开始低于前两者，且随原料气压力增加，节能效果更加明显。而对于富气，改进Ⅱ型流程能耗最高，改进Ⅰ型与HPA流程区别不明显。

关键词: 高压凝液回收, 流程改进, 流程优化, 能耗分析

CLC Number:

TE64

Hong JIANG, Shijian ZHANG, Jiaqiang JING, Cong ZHU. Comparison of conventional and novel high-pressure NGL recovery processes[J]. Chemical Industry and Engineering Progress, 2019, 38(06): 2581-2589.

蒋洪, 张世坚, 敬加强, 朱聪. 常规及创新高压凝液回收流程对比[J]. 化工进展, 2019, 38(06): 2581-2589.

Figures/Tables 13

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工况	N₂	CO₂	C₁	C₂	C₃	iC₄	nC₄	iC₅	nC₅	C₆	C₇	C₈ ⁺
1	1.0210	0.3504	88.2883	7.4074	1.5015	0.3003	0.3103	0.1301	0.0901	0.1502	0.2002	0.2503
2	0.9164	0.3655	86.3094	7.2607	3.1431	0.6556	0.6097	0.1285	0.0837	0.1163	0.2220	0.1892

工况	N₂	CO₂	C₁	C₂	C₃	iC₄	nC₄	iC₅	nC₅	C₆	C₇	C₈ ⁺
1	1.0210	0.3504	88.2883	7.4074	1.5015	0.3003	0.3103	0.1301	0.0901	0.1502	0.2002	0.2503
2	0.9164	0.3655	86.3094	7.2607	3.1431	0.6556	0.6097	0.1285	0.0837	0.1163	0.2220	0.1892

参数	数值	参数	数值
外输压力要求/kPa	6000	脱乙烷塔第三股进料位置	17
换热器最小接近温差/℃	4	膨胀机等熵效率/%	85^[14]
吸收塔塔顶与塔底压差/kPa	10	压缩机绝热效率/%	75^[15]
吸收塔理论塔盘数	8	导热油进料温度/℃	280
脱乙烷塔塔顶与塔底压差/kPa	20	导热油出料温度/℃	250
脱乙烷塔理论塔盘数	26	物性流体包	Peng Robinson^[16]
脱乙烷塔第二股进料位置	8	凝液回收率要求/%	≥99

参数	数值	参数	数值
外输压力要求/kPa	6000	脱乙烷塔第三股进料位置	17
换热器最小接近温差/℃	4	膨胀机等熵效率/%	85^[14]
吸收塔塔顶与塔底压差/kPa	10	压缩机绝热效率/%	75^[15]
吸收塔理论塔盘数	8	导热油进料温度/℃	280
脱乙烷塔塔顶与塔底压差/kPa	20	导热油出料温度/℃	250
脱乙烷塔理论塔盘数	26	物性流体包	Peng Robinson^[16]
脱乙烷塔第二股进料位置	8	凝液回收率要求/%	≥99

流程	操作变量	变量范围
流程	操作变量	工况1	工况2
HPA	低温分离器温度（T _S1）/℃	-36≤T _S1≤-30	-18≤T _S1≤-23
	TEE-101分流比（S ₁₀₁）	0.75≤S ₁₀₁≤0.82	0.75≤S ₁₀₁≤0.82
	吸收塔塔底凝液换热后进脱乙烷塔温度（T _S4）/℃	-5≤T _S4≤44
	吸收塔塔压（P _T-101）/kPa	4000≤P _T-101≤4700
	脱乙烷塔塔压（P _T-102）/kPa	3000≤P _T-102≤3800
	塔顶压缩机出口压力（P _S5）/kPa	P _S5＝P _T-101+200
改进Ⅰ型	低温分离器温度（T _S1）/℃	-35≤T _S1≤-28	-25≤T _S1≤-20
	TEE-101分流比（S ₁₀₁）	0.55≤S ₁₀₁≤0.6	0.75≤S ₁₀₁≤0.82
	吸收塔塔底凝液换热后进脱乙烷塔温度（T _S4）/℃	-5≤T _S4≤44
	吸收塔塔压（P _T-101）/kPa	4000≤P _T-101≤4700
	脱乙烷塔塔压（P _T-102）/kPa	3000≤P _T-102≤3800
	塔顶压缩机出口压力（P _S2）/kPa	P _S2＝P _T-101+200
改进Ⅱ型	低温分离器温度（T _S1）/℃	-38≤T _S1≤-32	-33≤T _S1≤-27
	TEE-101分流比（S ₁₀₁）	0.55≤S ₁₀₁≤0.65	0.65≤S ₁₀₁≤0.70
	吸收塔塔底凝液换热后进脱乙烷塔温度（T _S4）/℃	-5≤T _S4≤44
	吸收塔塔压（P _T-101）/kPa	4000≤P _T-101≤4700
	脱乙烷塔塔压（P _T-102）/kPa	3000≤P _T-102≤3800
	增压泵出口压力（P _S2）/kPa	P _S2＝P _T-101+50
	塔顶压缩机出口压力（P _S5）/kPa	P _S5＝P _S6