Development of an Oil Shale Retorting Process Integrated with

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Development of an Oil Shale Retorting Process Integrated with Chemical Looping for Hydrogen Production Qingchun Yang, Yu Qian, Yajun Wang, Huairong Zhou, and Siyu Yang Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.5b00999 • Publication Date (Web): 29 May 2015 Downloaded from http://pubs.acs.org on June 5, 2015

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Industrial & Engineering Chemistry Research

Development of an Oil Shale Retorting Process Integrated with Chemical Looping for Hydrogen Production

Qingchun Yang, Yu Qian, Yajun Wang, Huairong Zhou, Siyu Yang* School of Chemical Engineering, South China University of Technology, Guangzhou 510641

+For publication in I&EC Research

*Corresponding author: Professor Siyu Yang Ph.D. School of Chemical Engineering South China University of Technology Guangzhou, 510640, P. R. China. Phone: +86-20-87112056, +86-18588887467 Email: [email protected]

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Abstract

2

The increasing demand of crude oil is in conflict with the shortage of supply,

3

forcing many countries to seek for alternative energy resources. Oil shale is welcome

4

by many countries that are short of conventional fossil fuels. China mainly uses

5

retorting technology for shale oil production. Fushun-type oil shale retorting

6

technology takes the largest share in oil shale industry. However, this technology is

7

always criticized by its unsatisfactory economic performance. It is caused by many

8

reasons. One of the most important problems is inefficient utilization of retorting gas.

9

The idea of our research is to utilize the retorting gas to produce higher valued

10

chemicals. For this, chemical looping technology is integrated into the retorting

11

process for hydrogen production. This proposed process is modeled and simulated to

12

build its mass and energy balance. Techno-economic analysis is conducted and

13

compared to the analysis of the Fushun-type oil shale retorting process. Results show

14

that the exergy destruction of the proposed process is 235.62 MW, much lower than

15

that of the conventional process, 274.76 MW. In addition, the proposed process is less

16

dependent of shale oil price. Two shale oil price scenarios have been investigated,

17

showing that the proposed process can still make benefit, 10.62% ROI, at low shale

18

oil price. While the ROI of the conventional process is -2.07%.

19

Key words: oil shale retorting; chemical looping; hydrogen production;

20

techno-economic analysis 2


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1. Introduction

2

Oil shale is kerogen-rich rock with inorganic structure and is found in many

3

countries with substantial reserve.1 The United States, accounting for about 77% of

4

the world's oil shale, has the richest oil shale resources,2 followed by the Russia,

5

Brazil and China. Oil shale is one of the promising crude oil alternatives. With severe

6

energy shortage and big fluctuation in crude oil price, countries are in growing

7

interest in its exploration and exploitation. In the United States, there are several

8

demonstration plants in Colorado, Utah, etc.3 In China, there are some successful

9

operational plants in Fushun, Huadian, and Longkou.2 In the next 5-10 years, the

10

world's shale oil production may increase to 2.0 × 107 t. It can effectively relieve the

11

shortage of crude oil. Many countries are vigorously developing efficient,

12

environmental-friendly, and economical retorting techniques.

13

Current ex situ retorting technologies, involve Chinese Fushun-type retort,1

14

Brazilian Petrosix retort,4 Australian ATP retort,5 Estonian Kiviter and Galoter

15

retorts,6 have been mature and industrially implemented. Fushun-type retorting

16

technology has many advantages, such as strong adaptability, simple structure, and

17

reliable operation.1 A conventional Fushun-type oil shale retorting (OSR) process is

18

shown in Figure 1. It is set as the benchmark in this paper. Oil shale is converted into

19

shale oil, retorting gas, and char in the Fushun-type retort. The oil-gas mixture is

20

subsequently separated to obtain shale oil and retorting gas in the condensation and 3



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recovery unit. Part of the retorting gas is recycled to the retort to heat the retorting

2

reaction. The rest is used as fuel in the internal combustion engine to generate

3

electricity.

4

The composition of the retorting gas is shown in Table 1. Besides H2, CO and 7

5

CH4, it involves lots of N2 and CO2. Soot et al.

analyzed the comprehensive

6

utilization of retorting gas, and found that it needs a lot of energy for separation and

7

purification of retorting gas. Thus, retorting gas was often disposed as waste. To

8

improve the economic benefit of the OSR process, previous work1 and industry

9

practices used retorting gas for electricity generation. However, the unit heat value of

10

retorting gas produced by a Fushun-type retort is less than 3.5 MJ/Nm3. The

11

electricity generated by 1 m3 retorting gas is approximate to 1/12 of that by 1 m3

12

natural gas. The economic benefit improved by this way is not obvious.

13

With H2, CO and CH4 components, retorting gas has strong reduction. It can be

14

used as fuel gases of chemical looping hydrogen generation (CLH) technology or

15

steam methane reforming (SMR) technology. Compared to a conventional SMR

16

technology for hydrogen production, the CLH technology has many advantages, such

17

as: (i) The CLH process is relatively simple since it does not require additional gas

18

treatments (reforming, shift) and separation processes to produce pure hydrogen.8 A

19

potential for investment cost savings can be envisaged. (ii) The CLH process can

20

achieve self-heating balance. While the SMR reaction is a strongly endothermic

21

reaction. It needs a lot of extra heat. However, there is little waste heat in the OSR 4


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process. To meet the heat balance of the SMR reaction, it requires for burning

2

outsource fuels, such as oil shale, associated coal, etc. It is not cost-effective. Besides

3

the SMR process needs a lot of steam for reaction. But there is almost no surplus

4

steam for the SMR process in an OSR plant. Therefore according to the characteristics

5

of the OSR process, the CLH technology is selected in this paper.

6

The CLH technology has been applied to the process based on coal, 9

10

natural

7

gas13 and biomass14 since it was proposed. Xiang et al.

8

based hydrogen and electricity cogeneration process in which the CLH technology

9

used syngas as fuel gas. Results showed that the energy efficiency of the system is up

10

to 58.33%. Chiesa et al. 8 studied a hydrogen and electricity cogeneration process with

11

three chemical looping reactors. This process used methane as fuel gas. Fan and his

12

research team10-12 reported a series of researches on coal-based CLH technology. They

13

proposed to use hydrogen produced by a CLH process for electricity generation. They

14

have successfully built and put into operation two sets of small-scale demonstration

15

plants with 25 kW syngas chemical looping technology and a set of pilot plant with

16

250 kW high-pressure syngas chemical looping technology.12

studied a coal gasification

17

Our goal is to introduce this technology to the oil shale industry. Because the

18

composition of retorting gas is similar to coal-based syngas, it is feasible to use

19

retorting gas as fuel gas in CLH technology. In this case, an oil shale retorting process

20

integrated with chemical looping for hydrogen production (OSR-CLH) is proposed.

21

The CLH technology in the proposed process is to produce hydrogen. Outlet streams 5



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from the three reactors in the CLH unit are hot, and their heat can be recovered to

2

generate electricity and steam.15 The proposed process is modeled and simulated,

3

along with investigations on key operational parameters. The promising strengths of

4

the proposed process will be demonstrated by techno-economic analysis compared

5

with that of the Fushun-type process.

6

2. Chemical looping hydrogen generation technology

7

The schematic diagram of a chemical looping hydrogen generation (CLH)

8

process is shown in Figure 2.16 It is implemented by three reactors:17 a fuel reactor

9

(FR), a steam reactor (SR), and an air reactor (AR). In the fuel reactor, oxygen carrier,

10

i.e. metal oxide (MeOx), is reduced to lower valence state metal oxide (MeOx-a) by

11

fuel gas.8 Supposing that the fuel gases are CO, H2 and CH4, reduction reactions are

12

written as follows:

13

MeOx + a CO → MeOx-a + a CO2

(1)

14

MeOx + a H2 → MeOx-a + a H2O

(2)

15

MeOx + a/4 CH4 → MeOx-a + a/4 CO2 + a/2 H2O

(3)

16

In the steam reactor, the reduced carrier is partial oxidized to higher metal oxide

17

(MeOx-a+b), and the steam is converted to hydrogen according to the following

18

reaction:

19 20

MeOx-a + b H2O → MeOx-a+b + b H2

(4)

To provide the heat for the reactions in the fuel reactor, the air reactor is used to fully 6


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oxidize the carrier and regenerate oxygen carrier.18 This reaction is formulated as

2

follows:

3

MeOx-a+b + (a-b)/2 O2 → MeOx

4

In a CLH process, selecting an appropriated oxygen carrier is important.

5

Previous studies of oxygen carrier are mainly conducted on Ni, Fe, Cu, Co, Mn and

6

other transition metal oxide or their composite metal oxide.19 Rydén et al. 20 used NiO

7

/ MgAl2O4 as the oxygen carrier for natural gas chemical looping reforming process

8

in a fluidized bed reactor. Proll et al.

9

KW double circulating fluidized bed. Svoboda22 and Kang23 analyzed the

10

performance of Fe-Fe3O4, Ni-NiO and MnO-Mn3O4 oxygen carriers on hydrogen

11

production from the point of thermodynamics. They found that using the Fe-Fe3O4

12

oxygen carrier is the most efficient. Gupta et al.

13

oxides such as Ni, Cu, Cd, Co, Mn, Sn, and Fe. Fe2O3 is considered as the most

14

suitable oxygen carrier. In our research, Fe2O3 is used as the oxygen carrier for

15

process modeling and simulation.

16

3. The novel oil shale retorting process integrated with chemical

17

looping for hydrogen production

(5)

21

studied NiO/NiAl2O4 oxygen carrier in a 140

24

analyzed performance of metal

18

In this paper, the oil shale retorting process integrated with chemical looping for

19

hydrogen production (OSR-CLH) is proposed. It includes an oil shale retorting (OSR)

20

unit, a chemical looping hydrogen generation (CLH) unit and a power generation (PG) 7



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unit, as shown in Figure 3.

2

The OSR-CLH process uses the retorting gas produced by the OSR unit as fuel

3

gas for the CLH unit. H2, CO, CH4 and other gases in the retorting gas are firstly

4

oxidized to reduce Fe2O3 into Fe. Fe particles are reacted with hot steam to produce

5

Fe3O4 and hydrogen in the steam reactor. Fe3O4 particles are further oxidized to Fe2O3

6

in the air reactor. The output gas streams of the three reactors go into the power

7

generation unit to generate electricity and steam. The released energy from the

8

oxidation reaction in the air reactor is divided into two parts. One part is carried by

9

Fe2O3 particles and provided to the fuel reactor. The other part is carried by output gas

10

stream of the air reactor. It goes into the power generation unit to recover heat and

11

produce steam. The steam of the OSR-CLH process is recycled to the steam reactor.

12

4. Modeling and simulation of the OSR-CLH process

13

Modeling and simulation of the OSR-CLH process are done on ASPEN Plus

14

software (Version 7.2). The Liaoning Fushun oil shale is selected as the raw material.

15

The proximate and element analysis of the oil shale are shown in Table 2. The

16

processing scale of the OSR-CLH process is set as 375 t/h oil shale, referring to the

17

practice scale in the West Open Mines of Fushun Mine Group. Assuming that only 80%

18

oil shale particles satisfy the size required, thus the processing capacity of the retort is

19

300 t/h oil shale.

20

During the process design, the OSR-CLH process is divided into an oil shale

21

retorting (OSR) unit, a chemical looping hydrogen generation (CLH) unit, and a 8


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power generation (PG) unit. A simplified flow diagram of the OSR-CLH process is

2

shown in Figure 4. The key operational parameters for the simulation are summarized

3

in Table S1 in the Supporting Information.

4

4.1 Oil shale retorting process

5

Oil shale is defined as a mixture of water, minerals, organic matter (kerogen and

6

carbon residues). These components can be separately modeled as MIXED, SOLID,

7

and NC. RK-SOAVE (Redlich-Kwong-Soave) method is selected as physical property

8

method.

9

In the retort, oil shale is converted into retorting gas, shale oil, and char at 0.1

10

MPa and 520℃. We assume that only organic matters (kerogen) takes part in the

11

decomposition reaction. Kerogen is converted into bitumen and then to final products

12

at high temperature. Shale oil is simply formatted as C6H10. The retorting reaction can

13

be written as:

14 15

Kerogen → C6H10 + H2 + H2O + H2S + CO + CO2 + CH4 + C2H6 + C3H8

(6)

+ C4H10 + NH3 + Char

16

The kinetic equation for the decomposition is as follows: 1

17

dx − 26390 n n  E  T = k (1 − x ) = A exp  − a  (1 − x ) =2.81×1013 e (1 − x ) dt  RT 

(7)

18

where x is the concentration at a time t, kg/m3; k is the specific rate constant, s-1; n is

19

the order of the reaction; A is the apparent frequency factor, s-1; Ea is the apparent

20

activation energy, kJ/kmol; and R is the gas constant (R = 8.314 J/mol K). 9



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1

The retorting process of oil shale retorting is modeled as the continuously stirred

2

tank reactor by RCSTR model. The mixing stream from the retorting reactor consists

3

of shale oil, retorting gas, and char. Char is firstly separated out in a separator. Then

4

the mixing stream is washed in the washing tower to separate the retorting gas and the

5

shale oil. To get more shale oil, a part of the retorting gas is fed into the flash tank,

6

and the other part is fed into the cooling tower. The gas out of the flash tank as recycle

7

gas is recycled back to the retort. A part of the gas out of the cooling tower is used as

8

fuel gas for the furnace, and the other part is partially fed into the chemical looping

9

unit as feedstock. The solid phase is fed into the gasification reactor at 0.1 MPa and

10

850℃. The gasification is modeled by RGibbs model. The purified gasified gas is

11

recycled to the retorting reactor to provide heat for the retorting reactions. The more

12

detail modeling and simulation of the OSR unit can be found in our previous work.26

13

4.2 Chemical looping hydrogen generation unit

14

The CLH unit includes three reactors: a fuel reactor, a steam reactor, and an air

15

reactor. For simulation, the three reactors are based on the minimization of Gibbs free

16

energy concept. Solid particles are considered as solid solution phase and SOLID is

17

selected as the property method.

18

The retorting gas produced by the OSR unit enters into the fuel reactor to reduce

19

Fe2O3 to Fe, formatted as Eqs. (8) – (10). The temperature of the fuel reactor ranges

20

from 750℃ to 900℃.27 In the simulation, the temperature and the pressure of the fuel

10


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reactor are set to be at 870℃ and 3.0 MPa.27 The fuel gas is oxidized to CO2 and H2O.

2

The required heat for the fuel reactor is supplied by the solid particles from the air

3

reactor. Fe particles are fed to the steam reactor and reacted with hot steam. This

4

reaction is exothermic and generates a large amount of heat at 550-750℃. In the

5

simulation, Fe is oxidized to Fe3O4 (Eq. 11) at 720℃ and 3.0 MPa.18 Fe3O4 particles

6

are further oxidized to Fe2O3 in the air reactor (Eq. 12) at 1250℃ and 0.1 MPa. The

7

reactions in the air reactor are strongly exothermic. Part of this heat is carried out by

8

Fe2O3 particles and provided to the fuel reactor, while the rest is used to generate

9

electricity and steam. The three sets of reactions in these reactors can be found in the

10

work of Rydén and Arjmand.28 They are shown as follows.

11

In the fuel reactor

12

Fe2O3 (s) + 3CO (g) → 2Fe (s) + 3CO2 (g)

(8)

13

Fe2O3 (s) + 3H2 (g) → 2Fe (s) + 3H2O (g)

(9)

14

4Fe2O3 (s) + 3CH4 (g) → 8Fe (s) + 3CO2 (g) + 6H2O (g)

(10)

15

In the steam reactor

16

3Fe (s) + 4H2O (g) → Fe3O4 (s) + 4H2 (g)

17

In the air reactor

18

4Fe3O4 (s) + O2 (g) → 6Fe2O3 (s)

19

The outlet streams from the fuel reactor and steam reactor are both at high

20

temperature and high pressure.15 They can be used to generate electricity and steam.

21

After multi-stage compression and condensation, the process can generate 99.9 %

(11)

(12)

11



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purity hydrogen at 30℃ and 6 MPa.29

2

4.3 Analysis of key operational parameters

3 4 5

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Several key parameters of the novel process will be studied. They are retorting temperature and feeding rates of Fe2O3 and steam. Effect of retorting temperature

6

Retorting temperature has a significant effect on the yield of shale oil and

7

hydrogen. For studying this parameter, we firstly define the yield of shale oil (Yshaleoil)

8

and the yield of hydrogen ( YH 2 ) as follows.

9

10

Yshaleoil =

YH 2 =

m ( shale oil )

m ( oil shale )

× 100%

(13)

m (H2 ) × 100% m ( oil shale )

(14)

11

where m(shale oil), m(H2) and m(oil shale) indicate the mass flow rates of shale oil,

12

hydrogen and oil shale, t/h.

13

According to the simulation, the yields of shale oil and hydrogen rise as the

14

retorting temperature increases, as Figure 5 shows. The increasing rate keeps at a high

15

level in the temperature range between 420℃ and 520℃. The reason is that the

16

decomposition rate of oil shale increases quickly in this range. As the temperature

17

higher than 520℃, these two yields keep at high level without obvious increase. This

18

is because only a small amount of the remaining organics can be decomposed in this

19

temperature range. According to the analysis, the retorting temperature is set to 520℃

12


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in the following study.

2

Effect of Fe2O3 feeding rate

3

The Fe2O3 feeding rate in the fuel reactor is also a key parameter to make

4

efficient use of H2, CO and CH4. The effect of the Fe2O3 feeding rate on the outputs of

5

the fuel reactor is shown in Figure 6. The Fe particles increase when the Fe2O3

6

feeding rate increases from zero to 450 kmol/h. However, if the Fe2O3 feeding rate is

7

greater than 450 kmol/h, the Fe particles gradually decrease. The reason is that the Fe

8

particles are reacted with the Fe2O3 particles to produce FeO particles when all fuel

9

gas is consumed.17 To obtain the maximum production of hydrogen, the feeding rate is

10

selected as 450 kmol/h in the following studies.

11

Effect of steam feeding rate

12

To obtain the maximum hydrogen production, the Fe particles are oxidized to the

13

Fe3O4 particles as much as possible by excessive steam in steam reactor. The effect of

14

steam feeding rate on the main outputs of the steam reactor is shown in Figure 7. As

15

the feeding rate increases, more and more Fe particles are oxidized to Fe3O4 particles.

16

The amount of hydrogen gradually increases. If the steam feed rate is greater than

17

2000 kmol/h, all the Fe particles are consumed to produce Fe3O4 particles.

18

Consequently, the optimum steam feed rate is selected as 2000 kmol/h.

19

4.4 Simulation results

20

According to the study on the key parameters, the retorting temperature is fixed

13



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to 520℃, and the feed rates of Fe2O3 and steam are selected as 450 kmol/h and 2000

2

kmol/h. The compositions and conditions of the gaseous output streams in the

3

OSR-CLH process are shown in Table 3. In the oil shale retorting unit, 375 t/h oil

4

shale is fed into the retort to produce 15.63 t/h shale oil, 68.24 t/h remaining gas and

5

214.50 t/h ash. While in the OSR-CLH process, the retorting gas used as raw material

6

of the CLH unit can produce 1.58 t/h hydrogen (99.90% purity).

7

5. Technical and economic anlysis of the OSR-CLH

8

To manifest the advantage of the OSR-CLH process, we compare it with a

9

conventional OSR process. This comparison is based on the same production scale of

10

375 t/h oil shale and from both technical and economic points of view.

11

5.1 Technical analysis

12

The OSR and the OSR-CLH processes are poly-generation processes. Their

13

output streams contain chemical products (shale oil, H2) and electricity. Szargut30

14

suggests that it is recommendable to use exergy to analyze thermodynamic

15

performance of a poly-generation process, because exergy can measure the quality

16

and quantity of energy and chemical products. The standard exergies of oil shale and

17

shale oil are formulated as follows.1

18

θ eos = ∆hLθ + 2438 × ω

(15)

19

esoθ = 0.975 × ∆hHθ

(16)

14


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θ where eos is the standard exergy of oil shale, kJ/kg. ∆hLθ is the low heating value of

2

oil shale, kJ/kg. 2438 kJ/kg is the heat for water vaporization, ω is the mass fraction

3

of water in oil shale, %. esoθ is the standard exergy of shale oil, kJ/kg. ∆hHθ is the

4

high heating value of shale oil, kJ/kg. Referring to the work of Qian et al., 1 the low

5

heating value of Fushun oil shale is 5.43 MJ/kg, and the mass fraction of water is 5.0

6

wt %. The high heating value of Fushun shale oil is 40.8 MJ/kg. So we can calculate

7

the standard exergies of oil shale and shale oil. They are 5.55 MJ/kg and 39.75 MJ/kg.

8

The exergy of a stream consists of chemical exergy Exchem, physical exergy

9

Exphys, and mixing exergy △mixEx. It is formulated as Eq. (17).31

10

Exstream = Exchem + Exphys + ∆ mix Ex

11

The exergy balance of a process is shown in Eq. (18). The input exergy is equal

12

to the sum of product exergy Exprd, byproduct exergy Exbyprd, exergy loss Exloss, and

13

exergy destruction Exd: 31

14

∑ Ex = ∑ Ex

15

The exergy destruction can be calculated as follows.

16

Exd =∑ Exin − ∑ Exprd − ∑ Exbyprd − ∑ Exloss

17

Based on the Eqs. (15)-(19) and the simulation, the input-output streams exergies

18

of different units and the exergy efficiencies of the OSR and the OSR-CLH processes

19

are calculated and shown in Table 4.

in

prd

(17)

+ ∑ Exbyprd + ∑ Exloss + Exd

(18)

(19)

20

With the same processing capacity of oil shale, the exergy destruction of the

21

OSR and the OSR-CLH processes are 274.76 MW and 235.62 MW. The exergy 15



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Page 16 of 40

1

destruction of the OSR process is much more than that of the OSR-CLH process. This

2

is mainly because that the power generation unit in the OSR process has low

3

combustion efficiency, heat transfer efficiency and high irreversibility of combustion

4

reaction.32 In general, the overall exergy efficiency of an internal combustion engine

5

is only about 30%.1 Thus, a large part of exergy destruction occurs in the combustion

6

and the heat transfer. The exergy efficiency of the CLH unit can be more than 78%

7

because of the high conversion ratio of the fuel gas and the waste heat recovery.8 Thus,

8

the OSR-CLH process is more efficient than the conventional OSR process in energy

9

utilization.

10

11 12

5.2 Economic analysis The economic performance of the Fushun-type OSR and OSR-CLH processes was analyzed by capital cost, production cost and return on investment (ROI).

13

Analysis of capital cost: It consists of fixed capital cost and working capital cost.

14

Equipment cost is estimated by the exponential coefficient method, as formatted in Eq.

15

(20).33

16

I 2 = I1 (

Q2 sf ) Q1

(20)

17

where I1 and I2 are the reference and the practical equipment costs; Q1 and Q2 are the

18

correspondingly the reference and the practical scales; and sf is the production scale

19

factor. In this paper, sf is set to 0.67 suggested by Yang et al. 25

20

According to Eq. (20), the equipment cost and the scale of the reference one are 16


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1

required. In this paper, the reference equipment cost of the oil shale retorting unit

2

refers to our previous work.34 The reference equipment cost of the chemical looping

3

hydrogen generation unit refers to the literature.35 The power generation unit refers to

4

the literature by Chen at al.36 The total equipment cost of the OSR and the OSR-CLH

5

processes are 25.99 M$ and 31.63 M$. The rest costs, such as buildings and land cost,

6

engineering and supervision cost, and construction and contractor fee, are estimated

7

on the basis of their proportions to the total capital cost, 26 as shown in Table S2 in the

8

Supporting Information. The working capital cost is set to 20% of the total capital

9

referring to the work of Qian et al.

34

The total capital cost of the OSR and the

10

OSR-CLH processes are 100.60 M$ and 128.28 M$. The breakdown of the total

11

capital cost is shown in Figure 8. It is seen that the total capital cost of the OSR-CLH

12

process is 27.51% higher than that of the OSR process. It is mainly because that the

13

proposed process introduces two additional units, the chemical looping hydrogen

14

generation unit and the power generation unit.

15

Analysis of production cost: To calculate the total production cost (TPC) of the

16

OSR and the OSR-CLH processes, some assumptions are made and listed in Table S3

17

in the Supporting Information, following the works of Xiang et al.37 The TPC is

18

defined as the sum of the above components as shown in Eq. (21):37

19

TPC = CR + CU + CO&M + CD + CPOC + CAC + CDSC

(21)

20

CR is the raw material cost, CU is the utilities cost, CO&M is the operating and

21

maintenance cost, CD is the depreciation cost, CPOC is the plant overhead cost, CAC is 17



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1

the administrative cost, CDSC is the distribution and selling cost.

2

In this paper, the consumption of the raw materials and utilities are calculated

3

according to the simulation results described in Section 4. Their prices are referring to

4

the current market prices. The rest parts in the production cost are calculated

5

according to their proportions to the total production cost, referring to the works of

6

Qian et al.34 The straight-line method is adopted to calculate the depreciation cost

7

under the assumption of 20 years life time and 4% salvage value.

8

The total production costs of the OSR and the OSR-CLH processes are 80.13

9

M$/y and 98.59 M$/y. Their breakdown is shown in Figure 9. Because the raw

10

material of the OSR-CLH process includes oil shale and supplementary Fe2O3

11

particles, so the raw material cost of the OSR-CLH process is increased slightly. It is

12

also concluded that the cost of the OSR-CLH process is 23.04% higher than that of

13

the OSR process. It is mainly because the OSR-CLH process adds two new units.

14

However, the OSR-CLH process can bring more benefit than the Fushun-type OSR

15

process because of the high income from hydrogen. The detailed calculation of the

16

return on investment will be done in the next section.

17

Analysis of the return on investment: For the shale oil price depending on the

18

crude oil price, so the fluctuations of the crude oil price would inevitably lead to the

19

fluctuations of the shale oil price.38 In this paper, the return on investments of the

20

OSR and the OSR-CLH processes are compared at two scenarios. One uses a high

21

shale oil price, 800 M$/t, and the other uses the low shale oil prices, 445 M$/t. 39 18


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1

According to the simulation and the prices of the products, the total profits of the

2

OSR and the OSR-CLH processes are shown in Table 5. The return on investment

3

(ROI) is defined as the ratio of total net profit to total capital cost.40 Assumed the

4

enterprise income tax rate is 25%, the ROIs of the two processes are calculated and

5

shown in Figure 10. At the high shale oil price scenario, the ROI of the OSR-CLH

6

process increases from 31.02% to 36.57%. While at the low shale oil price scenario,

7

the ROI of the OSR-CLH process is 10.62%, much higher than that of the OSR

8

process, -2.07%. It is mainly because that the hydrogen produced by the chemical

9

looping unit can greatly increase income and significantly enhance the ability to resist

10

market price fluctuations. This proposed process will provide a new research direction

11

for oil shale retorting and deep processing of shale oil in future.

12

6. Conclusions

13

An oil shale retorting process integrated with chemical looping for hydrogen

14

production (OSR-CLH) is proposed in this paper. Combined chemical looping

15

technology, the proposed process utilizes remaining retorting gas of a Fushun-type oil

16

shale retorting (OSR) process to produce high price of hydrogen.

17

A techno-economic analysis of the proposed process is conducted based on the

18

modeling and simulation. The analysis is compared to that of the Fushun-type OSR

19

process. From the technical point of view, the proposed process is much lower at

20

exergy destruction than that of the OSR process. In contrast, from the economic point 19



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1

of view, the proposed process spends more capital cost and production cost with the

2

chemical looping hydrogen generation unit. However, the market price of hydrogen in

3

China is high. Thus, the same amount of oil shale can produce higher product value of

4

hydrogen in the proposed process than that of electricity in the OSR process.

5

Acknowledgements

6

The authors are grateful for financial support from the China NSF projects

7

(21136003 and 21306056), the National Basic Research Program (2012CB720504

8

and 2014CB744306).

9

Nomenclature

10

A = pre-exponential factor.

11

CR = the raw material cost, M$/y.

12

CU = the utilities cost, M$/y.

13

CO&M = the operating and maintenance cost, M$/y.

14

CD = the depreciation cost, M$/y.

15

CPOC = the plant overhead cost, M$/y.

16

CAC = the administrative cost, M$/y.

17

CDSC = the distribution and selling cost, M$/y.

18

Ex = exergy, MW.

19

Ea = activation energy, kJ/kmol.

20

I = project investment.

21

Q = production capacity.

22

R = gas constant, kJ/kmol·K.

23

T = temperature, K.

24

YH2 = the yield of hydrogen, %.

25

Yshaleoil = the yield of shale oil, %.

26

θ eos = standard exergy of oil shale, kJ/kg.

20


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1

esoθ = standard exergy of shale oil, kJ/kg.

2

∆hLθ = standard low heating value of oil shale, kJ/kg.

3

∆hHθ = standard high heating value of shale oil, kJ/kg.

4

k = reaction rate constants, s-1.

5 6

Abbreviations

7

AR = Air reactor.

8

CLH = Chemical looping hydrogen generation.

9

FR = Fuel reactor.

10

OSR-CLH = Oil shale retorting process integrated with chemical looping for hydrogen production.

11

OSR = Fushun-type oil shale retorting process.

12

PG = Power generation.

13

ROI = Return on investment.

14

SMR = Steam methane reforming.

15

SR = Steam reactor.

16

TPC = Total production cost.

17 18

Subscripts

19

chem = chemical.

20

byprd = byproduct.

21

d = destruction.

22

in = input.

23

n = reaction order.

24

prd = product.

25

phys = physical.

26

sf = scale factor.

27

t = time, s.

28

x = the concentration at a time t, kg/m3.

29 30

Greek letters

31

ω = mass fraction of water in oil shale, %.

21



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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1

Caption of Figures and Tables

2

Figures

3

Figure 1. Schematic diagram of the Fushun-type OSR process

4

Figure 2. Schematic diagram of chemical looping hydrogen generation process

5

Figure 3. Schematic diagram of the OSR-CLH process

6

Figure 4. Simplified flow diagram of the OSR-CLH process

7

Figure 5. Effect of retorting temperature on the yield of shale oil and hydrogen

8

Figure 6. Effect of Fe2O3 feeding rate on the outputs of the FR

9

Figure 7. Effect of steam feeding rate on the outputs of the SR

10

Figure 8. Total capital costs of the OSR and the OSR-CLH processes

11

Figure 9. Total production costs of the OSR and the OSR-CLH processes

12

Figure 10. Return on investments of the OSR and the OSR-CLH processes

13 14 15

Tables

16

Table 2. Proximate and elemental analysis of Fushun oil shale

17

Table 3. Simulation results of gaseous output streams of the OSR-CLH processes

18

Table 4. Exergy balance of the OSR and the OSR-CLH processes

19

Table 5. Price, production and income of the OSR and the OSR-CLH processes

Table 1. Composition analyses of retorting gas of Fushun-type oil shale retort

25



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1

2 3

Figure 1. Schematic diagram of the Fushun-type OSR process

26


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1

2 3

Figure 2. Schematic diagram of chemical looping hydrogen generation process

27



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1

2 3

Figure 3. Schematic diagram of the OSR-CLH process

28


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1

2 3

Figure 4. Simplified flow diagram of the OSR-CLH process

29



2 3

5.5 5 4.5 4 3.5 3 2.5 2 1.5 1

Yshaleoil YH2

0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1

yield of hydrogen (%)

1

yield of shale oil (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

420 450 480 510 540 570 600 retorting temperature (℃) Figure 5. Effect of retorting temperature on the yield of shale oil and hydrogen

30


Page 30 of 40

Page 31 of 40

1

molar flow rate (kmol/h)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1000 900 800 700 600 500 400 300 200 100 0

Fe H2 CO CH4 0

2 3

100 200 300 400 500 600 Fe2O3 (kmol/h)

Figure 6. Effect of Fe2O3 feeding rate on the main outputs of the FR

31



1 1200 1000

molar flow rate (kmol/h)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

800 600 400 Fe3O4 H2 Fe

200 0 0

2 3

500 1000 1500 2000 2500 3000 H2O (kmol/h)

Figure 7. Effect of steam feeding rate on the main outputs of the SR

32


Page 32 of 40

Page 33 of 40

1 140 total capital cost (M$)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Working capital and contingency Construction and contractor fee Engineering and supervision Buildings and land Instruments, piping and electrical Equipment and installation

120 100 80 60 40 20 0

2 3

OSR

OSR-CLH

Figure 8. Total capital costs of the OSR and the OSR-CLH processes

33



1 120 total production cost (M$/y)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Gereral expenses Plant overhead costs Fixed charges Operating & Maintenance Utilities Raw material

100 80 60 40 20 0

2 3 4

OSR

OSR-CLH

Figure 9. Total production costs of the OSR and the OSR-CLH processes

34


Page 34 of 40

Page 35 of 40

38.50 33.00 Return on investment (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


OSR OSR-CLH

27.50 22.00 16.50 11.00 5.50 0.00 -5.50

1 2 3

low price

high price

Figure 10. Return on investments of the OSR and the OSR-CLH processes

35



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1 2 3

4

Page 36 of 40

Table 1. Composition analyses of retorting gas of Fushun-type oil shale retort1 composition

N2

H2

O2

CO2

CO

CH4

Cn H m a

vol. (%)

54.9 - 63.2

9.9 - 11.8

0.4- 2.0

18.4 - 20.8

2.8 - 4.43

4.6 - 6.77

0.75 - 1.4

a: CnHm includes C2H4, C2H6, C3H8, C4H10, etc.

36


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1 2

Table 2. Proximate and elemental analysis of Fushun oil shale25 proximate analysis (wt. %, ar)

elemental analysis (wt. %, ar)

Moisture

Fix Carbon

Volatile matter

Ash

C

H

O

N

S

5.00

3.69

18.56

72.79

79.07

9.93

7.02

2.12

1.86

37



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Page 38 of 40

1 2

Table 3. Simulation results of gaseous output streams of the OSR-CLH processes retorting gas

recycle gas

FR-out

SR-out

AR-out

H2

temperature (℃)

46

46

870

720

1250

30

pressure (MPa)

0.1

0.1

3.0

3.0

0.1

6

mass flow (t/h)

85.30

248.64

115.92

18.98

18.86

1.58

N2

54.92

54.92

46.90

-

-

-

O2

0.40

0.40

0

-

-

-

CO2

20.84

20.84

29.05

-

-

-

CO

4.55

4.55

0

-

-

-

CH4

6.70

6.70

0

-

-

-

Cn H m

0.73

0.73

0

-

-

-

11.91

11.91

0

59.89

89.35

99.90

0

0

24.05

40.11

10.65

0.10

mole fraction (%)

H2 H2O

3

38


Page 39 of 40

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1

Table 4. Exergy balance of the OSR and the OSR-CLH processes items

OSR

OSR-CLH

exergy input

oil shale input

578.13

578.13

(MW)

utility input

14.89

19.36

total input

593.02

597.49

exergy output

shale oil

172.58

172.58

(MW)

electricity

19.92

14.16

H2 detrital shale loss destruction η (%)

0

51.61

115.63

115.63

9.73

7.89

274.76

235.62

51.95

59.24

2

39



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Page 40 of 40

1 2

Table 5. Price, production and income of the OSR and the OSR-CLH processes OSR item shale oil (t)

price ($) a

detrital shale (t) H2 (t) electricity (kWh) total income (M$/y)

a

OSR-CLH

production b

5

445 /800

1.25×10

5.80

7.50×105

3520 0.11

income a

－ 8

1.58×10

income

5

55.63a/100.00b

4.35

7.50×105

4.35

－

1.26×10

4

44.35

1.13×10

5

55.63 /100.00

17.38

1.25×10

12.43

77.36a/121.73b

116.76a/161.13b

-2.77a/41.60b

18.17a/62.55b

total profit (M$/y)

3 4

production b

a: at the low shale oil price scenario, 445 M$/t. b: at the high shale oil price scenario, 800 M$/t.

40


Development of an Oil Shale Retorting Process Integrated with

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