Evaluation of the cryogenic helium recovery process from natural gas based on flash separation by advanced exergy cost method – Linde modified process

doi:10.1016/j.cryogenics.2017.08.005

Cryogenics

Volume 87, October 2017, Pages 1-11

https://doi.org/10.1016/j.cryogenics.2017.08.005 Get rights and content

Highlights

•
Advanced exergoeconomic analysis is done on a new helium extraction process.
•
Cost of exergy destruction and exergy destruction rate are calculated.
•
Three different strategies are suggested to improve performance of the components.

Abstract

In this paper, exergy cost analysis method is used to evaluate a new cryogenic Helium recovery process from natural gas based on flash separation. Also advanced exergoeconomic analysis was made to determine the amount of avoidable exergy destruction cost of the process component. This proposed process can extract Helium from a feed gas stream with better efficiency than other existing processes. The results indicate that according to the avoidable endogenous exergy destruction cost C-4 (287.2$/hr), C-5 (257.3$/hr) and C-6 (181.6$/hr) compressors should be modified first, respectively. According to the endogenous investment and exergy destruction cost, the interactions between the process components are not strong. In compressors, a high proportion of the cost of exergy destruction is avoidable while in these components, investment costs are unavoidable. In heat exchangers and air coolers, a high proportion of the exergy destruction cost is unavoidable while in these components, investment costs are avoidable. Finally, three different strategies are suggested to improve performance of each component, and the sensitivity of exergoeconomic factor and cost of exergy destruction to operating variables of the process are studied.

Introduction

Helium is widely used in cryogenic industries because of its unique characteristics [1]. The main conventional sources of helium is natural gas (NG), and extracting helium from liquefied natural gas (LNG) end-flash has become one of the major production approaches [2]. The removal of Helium [3] and other undesirable components [4] has the secondary benefit of improving the heating value of NG. Due to its low normal boiling point, Helium can be isolated in cryogenic processes such as those used in natural gas liquefaction [5]. Two cryogenic methods are distillation-based and flashing-based processes. In the multi-stage flash process, the Helium together with Nitrogen in a series of flash drums is separated as the gas product. Two modified flash based Helium recovery processes were introduced and investigated [6]. A flash based Helium recovery process was developed to extract helium from the feed gas to a natural gas liquefaction plant [7]. In [8] a new process configuration which can recover Helium more than previous similar cases was introduced. Several process configurations were studied to find the most suitable system for integration with a LNG plant for recovery of the Helium from LNG end-flash gas [9]. The processes used for helium recovery from LNG end-flash gas are cost and energy-intensive [10]. Exergy analysis method has been used for evaluation of various energy systems [11], [12], [13], [14], [15]. Exergy analysis is utilized to evaluate a new integrated LNG, natural gas liquids (NGL) and nitrogen rejection unit (NRU) process [16]. LNG regasification processes are investigated by exergy method [17], [18]. Exergoeconomic analysis method combines the exergy concept with economic analysis procedures. Exergoeconomic evaluation is performed on two popular natural gas liquefaction processes, namely single mixed refrigerant APCI and Linde processes [19]. Exergoeconomic method is used to evaluate the NGL and LNG co-production process [20]. Exergoeconomic analysis and optimization of propane- mixed refrigerant LNG process is investigated [21]. Advanced exergy and exergeoconomic analysis methods are employed to recognize the interactions between the components and to determine proportion of investment and exergy destruction cost rates which can be avoided. Advanced exergy method is used for evaluation of an currently in operation thane recovery plant in Iran [22]. The results reveal that this process has a high potential for improvement. Advanced exergy analysis is applied on natural gas liquefaction processes (LNG) which uses mixed refrigerant cycles [23]. The results reveal that the interactions between the processes components are not strong. The multistage mixed refrigerant systems are evaluated with advanced exergoeconomic analysis [24]. To recognize interactions between the process components, two single mixed refrigerant processes were investigated by advanced exergoeconomic analysis method [25]. The results show that interactions between the process components are not considerable. Advanced exergoeconomic is applied on a novel process for production of LNG by using a single effect absorption refrigeration cycle [26]. The results show that for improvement of the process performance the compressors and air coolers investment costs should be changed.

In this paper exergoeconomic analysis method is used to evaluate a new cryogenic Helium recovery process from natural gas based on the flash separation. Also advanced exergoeconomic analysis is done on the components with great cost of exergy destruction rate because. Helium recovery processes have not been investigated by advanced exergoeconomic method before. This paper shows improvement potential of the flash based Helium recovery processes that can be avoided.

Section snippets

Process description

Flash based Helium recovery processes require less equipment towards the other cryogenic processes such as distillation based processes. Fig. 1 illustrates process flow diagram of the Helium recovery process proposed by Linde Co. [8]. Fig. 2 shows the under consideration process which is a modification of Linde process [6]. Scope of this process is production of a rich Helium stream from the natural gas as the product stream. Multi-stage compressors and Air coolers are utilized for compression

Thermodynamic modeling

Aspen HYSYS [27] software was used to model the cryogenic Helium recovery process. Two equation of states (EOS) namely Peng-Robinson-Stryjek-Vera (PRSV) and Peng–Robinson (PR) have been suggested for modeling of the cryogenic natural gas processes [28]. In this work Peng–Robinson (PR) equation of state is used for calculation of the thermodynamic properties. Table 3 presents process main equipment power consumption. A parameter (η) is used to compare performance of this process with similar

Conventional exergy and exergoeconomic analysis

Exergy is the maximum attainable useful work from a specific amount of energy. According to Eq. (2), total exergy is divided into four parts, namely physical (Ė_ph), chemical (Ė_ch), kinetic (Ė_ke) and potential (Ė_po) exergies [29]. $\dot{E} = {\dot{E}}_{ph} + {\dot{E}}_{ch} + {\dot{E}}_{ke} + {\dot{E}}_{po}$

Kinetic and potential exergies are usually neglected and physical and chemical exergies are gained as follows: ${\dot{E}}_{ph} = H - H_{o} - T_{o} (S - S_{o})$ ${\dot{E}}_{ch} = \sum x_{i} {\dot{E}}_{i}^{o} + G - \sum x_{i} G_{i}$

where in Eq. (2) T_o, S and H are the reference environmental temperature, entropy and enthalpy,

Conventional exergy and exergoeconomic analysis

Conventional exergy and exergoeconomic analysis methods were used to evaluate a new cryogenic Helium recovery process from natural gas based on the flash separation. Table 11 shows results of the exergy and exergoeconomic methods. After E-1 (9901.21 kW), HE-2 (9180.71 kW) and HE-1 (7352.91 kW) heat exchangers, the highest exergy destruction is related to C-4 (6458.42 kW), C-5 (6214.25 kW) and C-6 (5312.94 kW) compressors, respectively. Therefore, heat exchangers are responsible for around 53% of

Conclusions

In this paper advanced exergoeconomic analysis was used to evaluate a new cryogenic Helium recovery process from natural gas based on the flash separation method. According to the new parameter (η), the proposed process can extract the Helium from the feed gas stream with a better efficiency (95.8%) comparing to the Linde process (95%). Results of the conventional method showed that the heat exchangers are responsible for around 53% of exergy destruction of the process (excluding mixers, valves

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Research paperEvaluation of the cryogenic helium recovery process from natural gas based on flash separation by advanced exergy cost method – Linde modified process

Highlights

Abstract

Introduction

Section snippets

Process description

Thermodynamic modeling

Conventional exergy and exergoeconomic analysis

Conventional exergy and exergoeconomic analysis

Conclusions

Int J Hydrogen Energy

Int J Hydrogen Energy

Int J Hydrogen Energy

Int J Hydrogen Energy

Helium cryogenics

Springer Science & Business Media

Resources: stop squandering helium

Nature

Fundamentals of natural gas processing

Novel LNG-based integrated process configuration alternatives for coproduction of LNG and NGL

Ind Eng Chem Res

Cryogenic mixed refrigerant processes

Springer Science & Business Media

Advanced exergy analysis of novel flash based Helium recovery from natural gas processes

Energy

Optimum design of integrated liquid recovery plants by variable population size genetic algorithm

Can J Chem Eng

Helium extraction from LNG end flash

LNG links remote supplies and markets

Oil Gas J

Multi-objective exergy-based optimization of a continuous photobioreactor applied to produce hydrogen using a novel combination of soft computing techniques

Int J Hydrogen Energy

Simulation and exergy-method analysis of an industrial refrigeration cycle used in NGL recovery units

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Research paper
Evaluation of the cryogenic helium recovery process from natural gas based on flash separation by advanced exergy cost method – Linde modified process