Design and Analysis of Liquid Hydrogen Technologies: Liquefaction, Storage, and Distribution

By Ahmad K. Sleiti and Wahib A. Al-Ammari

Design and Analysis of Liquid Hydrogen Technologies: Liquefaction, Storage and Distribution offers readers a comprehensive guide to the development, analysis, design, and assessment methodologies for liquid hydrogen. From the fundamentals to the latest developments and current applications, the book provides an extensive and systematic discussion of the design, simulation, and techno-economic analysis methodologies supported by practical examples, verified codes, and innovative process designs.

The book provides a comprehensive overview of the liquid hydrogen economy, followed by detailed advanced thermoeconomic, exergoeconomic, optimization, and dynamic simulation models that are essential for the assessment of the current and future LH2 technologies. The authors then identify current technological challenges and propose innovative solutions for LH2 technologies, with a focus on the liquefaction plants and storage facilities. In-depth analyses are provided of the reliability, safety, and environmental impacts of the different stages of the LH2 supply, transportation, regasification, and distribution. To improve the economic feasibility of LH2 plants, recent advanced energy-integrated systems are discussed. Potential market applications are considered, and detailed techno-economic assessments are provided. Finally, the book critically evaluates the future directions and prospective development of liquid hydrogen technologies, regulations, safety standards, and new markets for liquid hydrogen applications.

Bringing together the latest information, Design and Analysis of Liquid Hydrogen Technologies: Liquefaction, Storage and Distribution provides a valuable resource for students, researchers, scientists, and engineers working in the hydrogen economy or involved in the processing, design, manufacturing, quality control, reliability, safety, systems, and testing of cryogenic refrigeration and liquid hydrogen production, storage, and transportation.

• Describes, in detail, the current operational and conceptual hydrogen liquefaction, storage, transportation, regasification, and distribution technologies
• Offers comprehensive analytical tools, decision-making tools, and practical examples for the advanced modeling and simulation of liquid hydrogen plants
• Provides techno-economic, reliability, safety, and environmental impact analysis of liquid hydrogen technologies, along with future prospects

• Language: English
• Publisher: Elsevier Science
• Release date: Apr 2, 2024
• ISBN: 9780443214370

Ahmad K. Sleiti

Dr. Ahmad K. Sleiti research is focused on energy systems and thermofluids, with special interest in cryogenic refrigeration, liquefaction of H2 and NG, turbomachinery, Solid Oxide Fuel Cells, alternative energy, energy efficiency, CFD and experimental thermofluids. Dr. Sleiti obtained his Ph.D. degree in Mechanical Engineering from University of Central Florida. He has authored over 135 peer-reviewed papers in journals and conference proceedings, 2 book chapters and 3 patents. Dr. Sleiti has over 30 years of experience in industry and academia as expert, tenured faculty member and consultant. Dr. Sleiti is currently a professor of mechanical engineering at Qatar University. Previously he held an assistant and associate professor positions at UNC, ERAU and UCF in USA from 2001 to 2015. He also worked as senior engineer, project manager and consultant for high-ranked engineering firms and R&D corporations (SIGMA, PENTA GROUP, BETA, Siemens Energy, Electrodynamics, ASHRAE and others).

Book preview

Front Cover for Design And Analysis Of Liquid Hydrogen Technologies - Liquefaction, Storage, and Distribution - 1st edition - by Ahmad K. Sleiti, Wahib A. Al-ammari

Design And Analysis Of Liquid Hydrogen Technologies

Liquefaction, Storage, and Distribution

Ahmad K. Sleiti

Department of Mechanical &Industrial Engineering, College of Engineering, Qatar University, Doha, Qatar

Wahib A. Al-ammari

Department of Mechanical &Industrial Engineering, College of Engineering, Qatar University, Doha, Qatar

Table of Contents

Cover image

Title page

Copyright

Chapter one. Current and future hydrogen liquefaction technologies—design and analysis

Abstract

Abbreviation

1.1 Introduction

1.2 Fundamentals of cryogenic liquefaction

1.3 Performance evaluation

1.4 Current operational and conceptual hydrogen liquefaction processes

1.5 Recent advanced hydrogen liquefaction technologies

1.6 Future directions for H2 liquefaction process

References

Chapter two. Challenges and potential solutions of liquid hydrogen technologies

Abstract

2.1 Challenges and potential solutions of liquid hydrogen technologies

2.2 Liquid hydrogen storage: current status, challenges, and potential solutions

2.3 Liquid hydrogen transportation and distribution: current status, challenges, and potential solutions

2.4 Liquid hydrogen applications: current status, challenges, and potential solutions

References

Chapter three. Design and selection of refrigerants used in liquid hydrogen plants

Abstract

3.1 Design and selection of refrigerants used in liquid hydrogen plants

3.2 Systematic thermodynamic approaches for the selection and design of cryogenic refrigerants

3.3 Discussion and comparison

3.4 Reliability, compatibility, and safety assessments of the cryogenic refrigerants

3.5 Environmental impacts of cryogenic refrigerants

3.6 Summary

References

Chapter four. Energy and exergy analyses of liquid hydrogen cycles

Abstract

Nomenclature

4.1 Introduction

4.2 Energy and exergy models of the liquid hydrogen system

4.3 Case study example

4.4 Case study results and discussion

4.5 Summary

References

Chapter five. Economic and environmental assessment of liquid hydrogen plants

Abstract

Abbreviations

5.1 Introduction

5.2 Economic analysis

5.3 Environmental analysis

5.4 Case study

5.5 Case study results and discussion

5.6 Summary

References

Chapter six. Optimization of hydrogen liquefaction processes

Abstract

6.1 Introduction to the optimization analysis

6.2 Optimization methodologies for H2 liquefaction systems

6.3 Objective function(s) and constraints

6.4 Case study 1: Optimizing the Mr composition

6.5 Case study 2: optimizing the operating conditions of the SMR-HPP

6.6 Summary

References

Chapter seven. Dynamic simulation of liquid hydrogen plants

Abstract

Nomenclature

7.1 Introduction

7.2 Dynamic simulation procedures

7.3 Equipment sizing

7.4 Control scheme configuration

7.5 Case study 1: dynamic simulation of multistream cryogenic heat exchangers

7.6 Case study 2: dynamic simulation of centrifugal compressor unit

7.7 Future pathways

7.8 Summary

References

Chapter eight. Innovations and advances of hydrogen liquefaction processes

Abstract

8.1 Introduction

8.2 Innovation and development approaches of liquid hydrogen processes

8.3 Case study: dual mixed refrigerant H2 liquefaction process

8.4 Case study results and discussion

8.5 Summary

References

Chapter nine. Hydrogen storage technologies

Abstract

Abbreviations

9.1 Introduction to hydrogen storage options

9.2 Storage of hydrogen as compressed gas

9.3 Storage of hydrogen as liquid hydrogen

9.4 Advances in hydrogen storage technologies

9.5 Techno-economic assessment of hydrogen storage and transportation

9.6 Boil-off gas management

9.7 Summary

References

Chapter ten. Liquid hydrogen distribution

Abstract

Nomenclature

10.1 Introduction to hydrogen transportation and distribution options

10.2 Applications and technologies related to liquid hydrogen transportation and distribution

10.3 Techno-economic evaluation of various pathways of hydrogen transportation and distribution

10.4 Challenges and solutions of liquid hydrogen transportation and distribution

10.5 Future directions

10.6 Summary

References

Chapter eleven. Liquid hydrogen safety and handling

Abstract

Nomenclature

11.1 Hazards of liquid hydrogen

11.2 Safety features of liquid hydrogen plants

11.3 Liquid hydrogen risk analysis and controls

11.4 Regulations, codes, and standards

11.5 Summary

References

Appendix

Appendix A. Example of energy and exergy analyses for H2 precooling process using a single mixed-refrigerant loop

Appendix B. Example of economic analyses for H2 precooling process using a single mixed-refrigerant loop

Appendix C. Example of ortho-para hydrogen convertor in a single mixed-refrigerant loop

Index

Copyright

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Chapter one

Current and future hydrogen liquefaction technologies—design and analysis

Abstract

Hydrogen global demand is projected to increase rapidly by 2050 because hydrogen is a clean energy carrier and enjoys several other advantages. Liquid hydrogen (LH2), in particular, is attractive, as it requires lower transportation and shipping load compared to other fuels due to its high gravimetric energy density. Technically, the gaseous H2 must be compressed to about 2000 bar to reach the same volumetric energy density as of LH2, which is incredibly difficult and impractical for safety standards. Economically, the cost of hydrogen storage in liquid form is less than half of the compressed gas form. However, the liquefaction process of H2 is an energy-intensive process and suffers from significant boil-off loss. Therefore in this chapter, the fundamentals and performance indicators of the hydrogen liquefaction processes are introduced. The recent advanced hydrogen liquefaction technologies are explained and compared and the future directions are discussed.

Keywords

Liquid hydrogen; cryogenic processes; mixed refrigerants; hydrogen liquefaction; dual-mixed refrigerant process

Abbreviation

CI Complexity index

DMR Dual-mixed refrigerant

GED Gravimetric energy density

GH2 Gaseous hydrogen

HLP Hydrogen liquefaction process

IRS Integrated Refrigeration and Storage

LH2 Liquid hydrogen

LNG Liquefied natural gas

Mr Mixed-refrigerant

MTPD Million tons per annum

OC Operational cost

OPC Otho-para converter

o-H2 Ortho-hydrogen

p-H2 Para-hydrogen

SMR Single-mixed refrigerant

TPD Tons per day

VED Volumetric energy density

Symbols

A capacity parameter of the equipment

COP Coefficient of performance

C_(BM,k) Cost of the base module

EXE Exergy efficiency, (%)

E_p Equipment purchase cost

FOM Figure of merit

F_(BM,k) Module cost factor

GRC Gross root cost, ($)

h Specific enthalpy, (kJ/kg)

K1,K2,K3 Cost constants

m Mass flow rate, (kg/s)

PBP Payback period, (years)

Q Heat transfer rate, (kW)

SEC Specific energy consumption, (kWh/kgLH2)

s Specific entropy, (kJ/kg-K)

TAC Total annualized cost, ($)

TCI total capital investment, ($)

W Work rate consumption or production, (kW)

Subscripts

Com Of a compressor

Exp Of an expander

FGH2 Feed gaseous hydrogen

PLH2 Produced liquid hydrogen in At the inlet of a component out At the outlet of a component

1.1 Introduction

Hydrogen (H2) is projected to be a key player in the future energy systems and liquid hydrogen (LH2), in particular, has a great potential to be used as an energy commodity (Ratnakar et al., 2021). Although H2 production was only about 70 million tons per annum (MTPA) in 2020, it is projected that the H2 demand could increase to 600 MTPA in 2050 (Eljack & Kazi, 2021). On the liquid H2 side, up to date, the worldwide LH2 capacity is about 360 tons per day (TPD). However, in view of the hydrogen future scenarios (mainly in transportation and industrial sectors), large-scale hydrogen liquefiers will be needed. For example, more than 260 hydrogen liquefiers with a total capacity of 102 MTPA would have to be located throughout Europe to meet the hydrogen demand in the transportation sector (Valenti, 2016). While hydrogen (in gas or liquid forms) enjoys several advantages that make it an attractive choice as a future fuel, such as abundancy, high energy density (mass basis), and clean energy carrier, the question is why to liquefy hydrogen?

From the energy point of view, H2 has the highest gravimetric energy density (GED, per unit mass) over common fuels as shown in Fig. 1.1. However, it has the lowest volumetric energy density (VED). For example, the VED of gaseous hydrogen (GH2) at 700 bar is seven times lower than that of gasoline, while its GED is 2.7 times larger than gasoline. Thus the low VED of the gas hydrogen (GH2) can be mitigated by liquefying hydrogen to increase the VED from 4.82 MJ/L (for GH2 at 700 bar) to 8.50 MJ/L (for LH2 at 1 bar). Although LH2 still has low VED than other fuels (3.7 times lower than gasoline), LH2 requires lower transportation and shipping load compared to other fuels for shipping the same quantity of energy (due to its high GED).

Figure 1.1 Comparison between the gravimetric and volumetric energy densities of mobility fuels according to their lower heating values.

From technical and economic perspectives, LH2 storage and distribution is one of the most viable methods rather than storing and distributing it as compressed hydrogen. Moreover, LH2 is preferred to GH2 when delivering large volumes over large distances, especially overseas (Okunlola et al., 2022). Technically, the GH2 must be compressed to about 2000 bar to get the same VED as of the LH2, which is incredibly difficult and impractical for safety standards in common applications. Economically, the cost of hydrogen storage in liquid form is $6/kWh compared to $15/kWh in compressed form at 700 bar or $13/kWh at 300 bar (Nazir et al., 2020). Despite the advantages of the LH2 compared to GH2, the hydrogen liquefaction process (HLP) of H2 is an energy-intensive process and consumes about 30% of the energy content of the liquefied H2. In addition, even with full insulation tanks, the LH2’s extremely low boiling point (i.e., 20.4 K) results in significant boil-off loss. Therefore researchers around the world have started several efforts to improve the performance of the hydrogen liquefaction and storage technologies. Several new innovative processes were recently introduced with significant reduction in the energy consumption (less than 6 kWh/kgLH2) compared to the existing liquefaction plants (12–15 kWh/kgLH2).

This chapter introduces the fundamentals of the HLPs in Section 1.2. Section 1.3 explains the various performance indicators used to evaluate the performance of the HLPs. Then, an overview of the current and recent advanced hydrogen liquefaction technologies is introduced in Section 1.4 and Section 1.5, respectively. Finally, the future directions of the hydrogen liquefaction technologies are discussed in Section 1.6.

1.2 Fundamentals of cryogenic liquefaction

Cryogenic liquefaction is the process of changing the phase of fluids (such as nitrogen [N2], oxygen, helium [He], and natural gas) from gaseous phase at atmospheric conditions (1 bar and 298 K) into a liquid phase at atmospheric pressure and cryogenic temperature (less than 123 K [-150°C]). The liquefaction process is accomplished using a sequence of compression, heat rejection, expansion, and heat absorption processes. The most fundamental liquefaction scheme is the single-pressure Linde–Hampson cycle as shown in Fig. 1.2A. It depicts the basic H2 liquefaction method according to the following mechanism: (1) the feed gas (state 1) is mixed with recycled gas (state 9) and compressed from near ambient pressure (state 2) to a high pressure (above H2 critical pressure [13 bar], state 3) in an intercooled manner. Then, after the final compression stage, the compressed flow is cooled to the ambient temperature by the cooler (process 3–4) and proceeds to a heat exchanger to be cooled down recuperatively (process 4–5) by the recycled gas (8–9). The cold stream is then throttled to near ambient pressure (isenthalpic process, 5–6) at which the hydrogen is partially liquefied at a cryogenic temperature of about 21 K. The LH2 is removed in the separator (state 7) while the remaining vapor is recirculated to the heat exchanger (state 8) and mixed with the feed gas to repeat the process.

Figure 1.2 Layout of (A) Linde–Hampson and (B) Claude cycles in the single-pressure configuration without precooling.

It should be noted that the basic Linde–Hampson cycle uses a valve for the throttling process and operates at a single, low-pressure with using the hydrogen as the working fluid. However, the expansion process could be conducted using an expander in an isentropic process, which mechanically extracts energy from the expanded fluid. This technique is implemented in a new scheme called Claude cycle as shown in Fig. 1.2B. To improve the performance of the simple single-pressure Linde–Hampson and Claude cycle, the expansion process could be split into two levels of low pressure in dual-pressure schemes. Moreover, a precooling process could be performed for the hydrogen stream before the recuperative heat exchanger.

However, these improvements increase the complexity of the process as discussed in the next subsection. Moreover, both Linde–Hampson and Claude cycles are considered as open cycles as they utilize the processed fluid (H2) as the working fluid. But the working fluid can be separated from the processed fluid as conducted in a scheme called cascade cycle. Cascade scheme is considered as a closed cycle and composed of several vapor-compression systems that utilize pure fluid in each loop (to obtain various temperature ranges) as shown in Fig. 1.3. Alternatively, the working fluid of the cascade cycle could be a mixture of refrigerants and circulated in a single loop over the entire temperature interval as shown in Fig. 1.4.

Figure 1.3 Layout of a cascade hydrogen liquefaction processes using pure refrigerant in each loop as working fluid.

Figure 1.4 Layout of a cascade hydrogen liquefaction processes using mixed refrigerants as working fluids in the precooling and liquefaction loops.

Up to date, mixed-refrigerant (Mr) cycles have achieved the best performance in terms of energy and exergy efficiencies as discussed in Section 1.5. However, their schemes have more complexity than all other available hydrogen liquefaction technologies. In summary, all HLPs could be categorized into three types of cycles: Linde–Hampson cycle, Claude cycle, and cascade cycle. The scheme of each cycle can be organized to operate the cycle at single-pressure or dual-pressure scenarios for the low-pressure side of the process. Also, a precooling process could be inserted to these schemes. Furthermore, the working fluid must be pure hydrogen (single fluid) in Linde–Hampson and Claude cycles and can be pure fluids or mixed refrigerants in cascade cycles. Finally, the expansion mechanism to get the cooling effect in the process could be performed by a throttling valve or expander. Fig. 1.5 summarizes the classifications of the HLPs based on their configurations, working fluids, and cooling effect mechanisms. In addition, it represents how these classifications applied to the available hydrogen liquefaction technologies.

Figure 1.5 Classifications of hydrogen liquefaction processes based on their configuration, working fluid, and cooling effect mechanism.

To evaluate the complexity of the various schemes of the hydrogen liquefaction cycles, the authors introduce a complexity index (CI) that is defined to indicate the degree of complexity of each cycle. This index is defined by giving a weighting value for each term under the classification chart such that CI for single pressure=1, dual pressure=2, precooled=3, single fluid=1, different pure fluids=2, mixed refrigerants=3, isenthalpic process=1, and isentropic process=2. Based on these values, we can get the CI of the cycle by summing the values of all applicable values in a specified scheme. For example, the single Linde–Hampson cycle has the following terms: single pressure=1, single fluid=1, and isenthalpic process=1, thus its CI is 3 (simplest scheme). For the cascade cycle shown in Fig. 1.4, it has the following terms: precooled=3, mixed refrigerants=3, and isentropic process=2, thus its CI is 8 (most complex scheme). The range of CI for each hydrogen liquefaction technology (cycle) is presented in Fig. 1.5. While the CI is increased remarkably from the Linde–Hampson cycle to the cascade cycle, the specific energy consumption (SEC) is significantly reduced to reach even less than 5 kWh/kgLH2 in cascade cycle compared to more than 30 kWh/kgLH2 in Linde–Hampson cycle. Thus detailed performance evaluation should be conducted for each proposed scheme to point out its feasibility in terms of energy, exergy, and economic perspectives. The basic performance indicators of the HLP are presented in Section 1.3.

1.3 Performance evaluation

Referring to the cascade Mr cycle as shown in Fig. 1.4 (as a general scheme), the performance evaluation of the HLP can be implemented using different thermodynamic and economic indicators including SEC, coefficient of performance (COP), figure of merit (FOM), exergy efficiency (EXE), and total annualized cost (TAC). In this section, the detailed definition and modeling of these indicators are discussed.

1.3.1 Thermodynamic performance evaluation

The HLP consumes large amounts of power to compress the working fluid usually in a multistage intercooled compression process. In Mr cycles, mechanical pumps are used to compress the liquid fractions of the working fluid to reduce the compression power and to maintain the efficient performance of the gas compressors. Furthermore, if the internal expansion processes are performed by expanders, then some mechanical power is recovered and should be considered in the evaluation of the net power consumption of the HLP. Based on that, the SEC of the HLP is generally defined as (Yin & Ju, 2020):

Equation (1.1)

where Equation is the mass flow rate of the product (LH2), and Equation , Equation , and Equation are the work rate of the compressor, pump, and expander, respectively. The work rate of each component is obtained by applying the mass and energy balance principles. For steady-state analysis with negligible kinetic and potential energy balance alternations, mass balance gives (Al-Ammari & Sleiti, 2022):

Equation (1.2)

And the energy balance gives:

Equation

(1.3)

The COP of the HLP is introduced to evaluate the performance of the liquefaction process in terms of the net power required for the heat removal. The removed heat from the feed gas can be calculated using the difference between the enthalpies of the feed gaseous hydrogen ( Equation ) and the produced liquid hydrogen ( Equation ) multiplied by the flow rate of the feed gaseous hydrogen ( Equation ). Thus the COP of the HLP is defined as:

Equation (1.4)

To evaluate the net actual consumed power compared to the minimum ideal power required for the liquefaction process, the definition of the overall exergy efficiency ( Equation ) of the HLP is used. The minimum ideal power is calculated based on the difference between the exergy rate of the produced LH2 and the exergy rate of the gaseous feed hydrogen. Thus the Equation is defined as:

Equation

(1.5)

It is worth mentioning that some studies use the definition of FOM instead of the EXE; however, both indicators have similar definitions except that the denominator of FOM is the total compression power without subtracting the expander power as:

Equation

(1.6)

1.3.2 Ortho-para hydrogen conversion

As shown in Fig. 1.6A and B, the molecular hydrogen (H2) exists in two different spin isomers that are called ortho-hydrogen (o-H2) and para-hydrogen (p-H2). In o-H2, nuclear spins are in the same direction while in p-H2, nuclear spins are in the opposite directions. The equilibrium of ortho-para composition is temperature dependent as shown in Fig. 1.6C. At room temperatures (300 K), it corresponds to approximately 75% o-H2 and 25% p-H2 and is called normal hydrogen, n-H2. In terms of liquefaction, the most important fact is that o-H2 has a higher energy content than p-H2. Consequently, heat is generated during the conversion from o-H2 to p-H2. In a few seconds or maximum minutes, hydrogen can be very quickly cooled and liquefied. As a result, the composition of LH2 will be the same as n-H2 as the natural ortho-to-para conversion occurring in a longer time than the liquefaction process. Therefore the conversion process will slowly continue in the storage tank and the heat generated eventually leads to complete evaporation of LH2. Consequently, ortho-para H2 conversion must be performed before the storage, preferably during the liquefaction process using ortho-para catalytic (OPC) converters as shown in Fig. 1.4. In this way, LH2 will be at equilibrium mixture at the liquefaction temperature (20 K) and hence be suitable for long-term storage. More importantly, the difference in the thermodynamic properties of the o-H2 and p-H2 must be considered through the analysis of the HLP. For example, in the calculation of the previous thermodynamic performance indicators, the LH2 ( Equation and Equation ) is used for p-H2 if the OPCs are used in the process.

Figure 1.6 Schematic of (A) ortho-hydrogen, (B) para-hydrogen spin isomers of molecular hydrogen, and (C) equilibrium hydrogen composition depending on temperature.

1.3.3 Composite curves

Composite curve is one of the useful tools for the analysis of the HLP (especially for the Mr cycle). It is a graphical visualization of the heat transfer flow through the heat exchangers (x-axis) versus the temperature of the hot and cold streams (y-axis). For example, the precooling process of the Mr HLP as shown in Fig. 1.4 is used to precool the hydrogen from the ambient temperature to 78 K (-195°C). The composition of the Mr used in this process significantly affects the energy consumption of the precooling process. To examine if the Mr composition is perfect or not, the composite curve is plotted as shown in Fig. 1.7A. Then, if there is a large gap between the hot-composite and cold-composite curves, this means that the Mr composition could be tuned or modified to get a better match between them as shown in Fig. 1.7B. In case of the five-components Mr, the SEC of the precooling process is about 2.58 kWh/kgLH2 and can be reduced to 1.08 kWh/kgLH2 (58% reduction) (Sleiti & Al-Ammari, 2022).

Figure 1.7 Composite curve of the hydrogen precooling process in the mixed-refrigerant cycle for (A) five-components and (B) seven-components mixed-refrigerant (Mr) compositions. Note: the composition of the Mr is presented in molar basis.

1.3.4 Economic evaluation

For the economic evaluation of the HLP, Guthrie’s method could be used to calculate the TAC of the plant. The first step is to obtain the equipment purchase cost ( Equation ) (Naquash, Riaz, et al., 2022):

Equation

(1.7)

where Equation is the capacity parameter of a component, and Equation , Equation , and Equation are the cost constants for each component as shown in Table 1.1.

Table 1.1

HLP, Hydrogen liquefaction process; Mr, mixed-refrigerant.

Once Equation is obtained, the cost of the base module is calculated as:

Equation (1.8)

where Equation is the module cost factor. The operational cost of each process is calculated as:

Equation

(1.9)

To compare the economic costs of the various HLPs, three economic indicators are used, which are the total capital investment (TCI), grass root cost (GRC), and the TAC, which are defined as:

Equation (1.10)

Equation (1.11)

Equation (1.12)

where Equation is the payback period and is typically set to 5 years.

1.4 Current operational and conceptual hydrogen liquefaction processes

This section presents an overview of the operational LH2 plants around the world. Moreover, all the conceptual HLP available in the literature are discussed.

1.4.1 Operational hydrogen liquefaction plants

As shown in Fig. 1.8, the United States has the largest share of the LH2 production with a total capacity of 214 TPD using nine plants with the production rate of 6–34 TPD as listed in Table 1.2. The second country with the large margin is Canada with the total capacity of 81 TPD. In both countries, the largest part of the LH2 is supplied by Air Products followed by Praxair. It is worth mentioning that hydrogen liquefaction plants are considered as large-scale if their production capacity is more than 30 TPD, medium-scale with a capacity between 5 and 30 TPD, and small-scale with a capacity of less than 5 TPD. Based on that, four large-scale LH2 plants are operated by Air Products with production rate between 30 and 34 TPD and Praxair has only one large-scale plant with a capacity of 30 TPD. These large-scale plants were based on the precooled Claude system with typical SEC of 12.5–15 kWh/kgLH2. While North America (United States and Canada) has about 84% of the current hydrogen liquefaction capacity, Europe has 4 plants with a capacity of about 30 TPD (7%), and Asia has 11 plants with a total capacity of about 31 TPD (8%). About 18.6% of the produced LH2 is used for aerospace applications, 33.5% is used in petroleum industry, and the rest is for other industries.

Figure 1.8 Total installed hydrogen liquefaction capacity per country.

Table 1.2

TPD, Tons per day.

The most recent large-scale hydrogen liquefaction plant was commissioned in 1997 and operated by Praxair (United States). Currently, the newest plant was built in Germany (Leuna) in 2007 with a capacity of 5 TPD using more efficient cold box (shown in Fig. 1.9) than that of the plant existed in Ingolstadt. A single GH2 stream is fed to Leuna plant from a separation plant of air (which is precooled by the N2 produced from that separation unit), the ortho-para converters are installed inside the heat exchangers, and there is no recycled hydrogen. Although the current hydrogen liquefaction capacity is about 355 TPD worldwide, which is very small as compared to liquefied natural gas (LNG) (800,000 TPD), the required liquefaction capacity for powering the projected industrial and transportation sectors is orders of magnitude than the current capacity.

Figure 1.9 H2 liquefier of Linde plant in Leuna. From Krasae-in, S., Stang, J.H. & Neksa, P. (2010). Development of large-scale hydrogen liquefaction processes from 1898 to 2009. International Journal of Hydrogen Energy, 35(10), 4524–4533. https://doi.org/10.1016/j.ijhydene.2010.02.109.

1.4.2 Conceptual hydrogen liquefaction processes

Alongside the growth of hydrogen market since 1960s, several conceptual plants were proposed with various capacities and competitive performances as summarized in Table 1.3 for the period from 1978 to 2022. Mostly, all of these proposed processes suggest the precooled scheme and technically differ in the techniques of the precooling process and the type of the working fluids. Statistically, three precooled schemes have the most research interest, which are N2 precooled, Mr precooled, and He precooled processes. The energetic and exergetic performances of these schemes are presented in Fig. 1.10.

Table 1.3