Integrated Process of Coke-Oven Gas Tri-Reforming and Coal

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An integrated process of coke-oven gas tri-reforming and coal gasification to methanol with high carbon utilization and energy efficiency Yu Qian, Yi Man, Lijuan Peng, and Huairong Zhou Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/ie503670d • Publication Date (Web): 12 Feb 2015 Downloaded from http://pubs.acs.org on February 18, 2015

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Industrial & Engineering Chemistry Research

An integrated process of coke-oven gas tri-reforming and coal gasification to methanol with high carbon utilization and energy efficiency Yu Qian*, Yi Man, Lijuan Peng, Huairong Zhou School of Chemical Engineering, South China University of Technology, Guangzhou, 510640

+For publication in Industrial & Engineering Chemistry Research

*Corresponding author: Phone: +86-20-87113046 Email: [email protected]

ACS Paragon Plus Environment


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ABSTRACT

2

The hydrogen to carbon (H/C) ratio of coal gasified gas ranges of 0.2-1.0, far

3

less than the desired value for the coal to methanol process. Therefore, a water gas

4

shift unit is needed to raise the H/C ratio, which results in a great deal of CO2

5

emission and carbon resource waste. At the same time, there is 7×1010 m3 coke-oven

6

gas (COG) produced in coke plants annually in China. The hydrogen-rich COG

7

consists of 60% hydrogen and 26% methane. However, massive of COG is utilized as

8

fuel or discharged directly into the air, which makes a waste of precious hydrogen

9

resource and causes serious environmental pollution. This paper proposes an

10

integrated process of coke-oven gas and coal gasification to methanol, in which a

11

tri-reforming reaction is used to convert methane and CO2 to syngas. The carbon

12

utilization and energy efficiency of the new process increase about 25% and 10%,

13

while CO2 emission declines by 44% in comparison to the conventional coal to

14

methanol process.

15 16

Keywords: coal gasification; coke-oven gas; tri-reforming; methanol; carbon

17

utilization efficiency

1


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1. INTRODUCTION

2

Methanol is one of the most important platform chemicals. Methanol production

3

in China is mainly based on coal. However, coal to methanol (CTM) process suffers

4

from high CO2 emission due to the high carbon contents of coal.1 In conventional coal

5

to methanol (CTM) process, coal is transformed into coal water slurry and then

6

gasified to crude syngas. The hydrogen-to-carbon (H/C) ratio of the crude syngas is

7

about 0.7, while the required H/C ratio for methanol synthesis is about 2.1. Therefore

8

the H/C ratio has to be adjusted.2 In the CTM process, a water gas shift (WGS) unit is

9

implemented to convert part of CO into H2 and CO2.CO2 and H2S are removed from

10

the shifted syngas in an acid gas removal (AGR) unit, then clean syngas enters

11

methanol synthesis unit to produce methanol.2 The CO2 derived from the gasifier and

12

the WGS unit is released into the atmosphere, which results in the waste of massive

13

carbon resources and negative environmental impacts.

14

Coke-oven gas (COG) is one of the byproducts of coking plants. It consists of

15

55-60 % H2，23-27 % CH4，5-8 % CO，with H/C ratio as high as 6.5.3 There are7×1010

16

m3 COG generated in China annually. However, only 20% of COG is burned as a fuel;

17

most of the gas is directly discharged into the atmosphere.4 It results in considerable

18

waste of resource and energy.

19

In consideration that coal gasified gas has high carbon contents while COG has

20

high hydrogen contents, they could be integrated to produce the methanol syngas with

21

suitable H/C ratio. Man et al.5 proposed a process of coal gasification syngas and 2



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1

COG for methanol and olefins production, with the merit of implementing dry

2

reforming of methane for adjusting the H/C ratio, as well as improving the carbon

3

utilization efficiency and mitigating CO2 emission. Yi et al.6 modeled and analyzed a

4

dual-gas process of coal gasified gas and coke-oven gas for poly-generation of

5

dimethyl ether (DME) and electricity. The analysis showed that the carbon utilization

6

efficiency was 64.8% and the energy efficiency was 62.3%. Compared with the single

7

production system, both the carbon utilization efficiency and the energy efficiency

8

increase by about 10%.

9

The above studies indicate that, coke-oven gas could be made of better use when

10

it is reformed to produce higher valued CO and H2. There are three common

11

approaches to convert methane from COG to syngas: steam methane reforming

12

(SMR), dry methane reforming (DMR), and methane partial oxidation (MPO). Three

13

fundamental reactions are shown in Eqs. (1) - (3).7

14

SMR: CH4 + H2O = CO + 3H2 △H = 247.3 kJ/mol

(1)

15

DMR: CH4 + CO2 = 2CO + H2 △H = 206.3 kJ/mol

(2)

16

MPO: CH4 + 0.5O2 = CO + H2 △H = - 35.6 kJ/mol

(3)

17

SMR and DMR are endothermic reactions with high energy consumption, while

18

MPO is an exothermic reaction. If the three reactions could be coupled, self-heating

19

would be good for energy-saving.

20

A tri-reforming of methane (TRM) to couple SMR, DMR, and MPO reaction

21

together in a single reactor is proposed8 and utilized to produce chemical in the 3


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industry scal by South Korea Gas Company (KOGAS)9. TRM is also a good way of

2

CO2 treatment in coal-based industry because it can convert the pollutant into the

3

useful syngas.10 Zhang et al.11 proposed a dimethyl ether (DME) production with

4

tri-reforming process for zero CO2 emission and 33% energy saving.

5

They have not been reported about integration of COG and coal gasified gas

6

coupled with TRM. Aimed to make use of COG and CO2 from coal gasification

7

syngas, this paper proposes a novel process of coke-oven gas assisted coal to

8

methanol (COG-CTM) with the tri-reforming unit. The novel process takes

9

advantages of hydrogen-rich COG to adjust H/C ratio of the syngas to a suitable range,

10

with appropriate energy consumption, for better carbon utilization and less CO2

11

emission.

12 13

2. INTEGRATION OF COG TRI-REFORMING AND COAL GASIFICATION

14

The schematic diagram of co-feed process of coke-oven gas tri-reforming and

15

coal gasification to methanol (COG-CTM) is shown in Figure 1. The upper part is a

16

conventional coal gasification to methanol process. In the gasification unit, coal water

17

slurry reacts with oxygen to create crude syngas. The crude syngas enters the WGS

18

unit which to be partially converted CO into H2 and CO2. Then it enters the AGR unit,

19

where CO2 and sulfide in the crude syngas are removed. Clean syngas (flow 6) is next

20

sent to the methanol synthesis unit to produce methanol.

4



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1

In the lower part of Figure 1, the COG is purified to remove H2S and CO2. Then

2

98% of methane (flow 3) and hydrogen (flow 8) are obtained by cryogenic separation.

3

CO2 derived from the acid gas removal unit and methane are introduced into the

4

tri-reforming unit to generate syngas (flow 7). Three flow of syngas (flow 6, flow 7,

5

flow8) are mixed to reach the desired H/C ratio, then enter the methanol synthesis

6

unit.

7

TRM unit is the key installation of the co-feed process Pan12 proposed a reaction

8

kinetic of tri-reforming with the Ni-based catalyst that has been extensively tested

9

under lab scale condition. The reaction kinetic equation is shown in Eqs. (4)-(5).12

10

dxi = ki ⋅ Pco2 dt

11

ki = Ae

12

where m and n are the reaction order, P is the equilibrium pressure, k is reaction rate

13

constants. The parameters of the reaction kinetic is given in Table S1 in the

14

Supporting Information.12

m ,i

( ) ⋅( P )

−

Ea i

n ,i

H 2O

RT

(4) (5)

15

Tri-reforming process is modeled using Aspen Plus (V7.2). The process of

16

tri-reforming is modeled by the minimum free energy of Gibbs Reaction model and

17

Peng-Robinson state equation is used as the equilibrium properties method followed

18

by the work of Zhang et al.13 discovered the feedstock ratio in tri-reforming process is

19

identified as 1:0.291:0.576:0.088 (CH4: CO2: H2O: O2). With this condition, the

20

tri-reforming process could attain the maximum H2 yield and CO2 conversion coupled

21

with a desired synthesis gas H/C ratio for the downstream methanol production and 5


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effective elimination of carbon formation. The simulation results of the mole fraction

2

of H2 and CO in the tri-reforming reactor outlet with different pressure and

3

temperature are plotted in Figure 2 and Figure 3. The H2 and CO composition

4

decrease with the pressure increase from 0.1 to 1 MPa at the same reaction

5

temperature. Therefore, 0.1 MPa is the most suitable for tri-reforming. It can also be

6

found that the H2 and CO composition increase with raising of the reaction

7

temperature from 773 to 1273 K. At the same time, the H/C ratio decreases with the

8

raising of the reaction temperature from 773 to 1273 K. It was found that the reaction

9

temperature of tri-reforming should be around 1073 K. In such conditions, the H/C

10

ratio of the tri-reforming syngas is suitable for methanol synthesis. And the H2 and

11

CO composition is nearly maximum. The impact of the reaction temperature on the

12

H/C ratio of the syngas at the outlet of the tri-reforming reactor is plotted in Figure 4.

13

In simulation of the integrated process, the coal handling scale of a Texaco coal

14

gasifier is around 0.15-0.65 Mt/y. If the gasifiers are operated in the mode of five

15

running and two spare, the coal handling scale would be 0.75-3.25 Mt/y. This paper

16

takes the average coal handling scale, 2 Mt/y, as the case study. Chinese government

17

requires for coking industry the production scale to be at least 1 Mt/y,14 which means

18

the coal handling scale should be up to 1.4 Mt/y. The coking plant with 6 Mt/y coal

19

handling scale is selected as the case study. The main operation parameters of the

20

integrated process are shown in Table S2 in the Supporting Information. Modeling

21

and simulation results are given in Table S3 in the Supporting Information, in which 6



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1

stream numbers refer to Figure 1. Modeling and simulation of the individual units in

2

the conventional coal to methanol have been conducted and presented in the authors’

3

previous work 5, 15.

4 5

3. PERFORMANCE ANALYSIS OF THE PROPOSED SYSTEM

6

The proposed COG-CTM process is characteristic of two key variables. One is

7

the feedstock ratio; another is the CO shift degree. The feedstock ratio refers to the

8

ratio of COG to gasification coal. Coke-oven gas is by-product of the coking process;

9

each ton of coal produces 0.75 t coke and 340 m3 coke-oven gas.16 The amount of the

10

COG is translated into the quantity of the coking coal. The feedstock ratio is defined

11

as the ratio of the processing capacity of the coking coal to the gasification coal, as

12

shown in Eq. (6).

13

α=

14

The CO shift degree means the degree of CO converted into CO2 in the WGS unit, as

15

shown in Eq. (7).

16

β=

17

where F stands for the mole flow rate of CO in a stream.

SCoal Coking

(6)

SCoal Gasification

FCO(before WGS) − FCO(after WGS) FCO(before WGS)

(7)

18

In the COG-CTM process, coal is the main feedstock, which is directly related to

19

the resource utilization efficiency, economic benefits and CO2 emission. Carbon is the

20

major element in coal. Carbon utilization efficiency can be used as an evaluation 7


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index to measure system performance17. It can be calculated from the ratio of output

2

and input effective carbon components of a process17. For the integrated process, coal

3

and COG are inlet effective compounds, methanol is outlet effective one. The carbon

4

utilization efficiency for the GaCTO,η , is defined as Eq (8).

5

6 7

f =

out Methanol in in Coal COG

F

+F

F

× 100%

(8)

where F is the mole flow rate of different materials. The energy efficiency is the ratio of energy of the target product to the total input

8

energy,18 as shown in Eq. (9).

9

φ=∑

Eout

∑E

×100%

(9)

in

10 Analysis of the energy efficiency is based on the target product low heat value of 11 methanol and the raw materials low heat value of coal and COG. 12

3.1. Scale Ratio of Coal Gasification to Coal Coking

13

In the integrated process, if the COG is insufficient, the H/C ratio of the syngas

14

cannot achieve the requirement of methanol synthesis. Therefore, the WGS unit is

15

needed for the syngas conversion. The feed ratio of the COG has a positive effect on

16

H/C ratio of the final syngas. With the increase of α, the H/C ratio and the carbon

17

utilization efficiency are both improved. When α=7, the H/C ratio of the syngas

18

reaches 2. When α＞7, excessive COG has little effect on carbon utilization efficiency.

19

The effect of α on H/C ratio of syngas and carbon utilization efficiency is plotted in

20

Figure 5. 8



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1

To achieve the required H/C ratio and ensure high carbon utilization efficiency,

2

α=7 is the ideal scale ratio. For the 2 Mt/y coal gasification plant, is needed 14 Mt/y

3

coking plant to match. However, for the typical coking plant with 6 Mt/t coal handling

4

scale (α=3), the H/C ratio of the syngas in the co-feed system is only around 1.5 due

5

to the limitation of the hydrogen resource, as shown in Figure 5. In view of this fact,

6

H/C ratio should be adjusted by changing the CO shift degree.

7

The integrated system for two schemes, the appropriate scale ratio and the ideal

8

scale ratio, are analyzed as followed.

9

3.2. Scheme 1: the COG-CTM Process with WGS Unit

10

As discussed earlier, the scale of coal coking is three time of the scale of the coal

11

gasification. It represents appropriate scale ratio of coal coking to coal gasification for

12

most of existing coking and gasification plants. The system is flexible to reform and

13

operate.

14

When coking coal to gasification coal ratio is 3, the WGS unit is still needed in

15

the process. The WGS reaction and the TRM reaction coordinate to adjust the H/C

16

ratio. The CO shift degree (β) affects significantly on the H/C ratio and the carbon

17

utilization efficiency. When without COG assisted in the process, part of CO in coal

18

gasified gas should be shifted at β=0.4-0.5 to obtain the required H/C ratio; When

19

COG assisted coal gasification process, the CO shift degree will drop to below 0.3.

20

The effect of β on the H/C ratio and the carbon utilization efficiency is shown in

21

Figure 6. As increase of β, more CO is converted to H2 and CO2, the H/C ratio 9


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increases. The carbon utilization efficiency increases first and then decreases. When

2

β=0.23, the H/C ratio is 2 and the carbon efficiency is 43%. When β＜0.23, the H/C

3

ratio is less than 2. Increase of β makes H/C ratio reach 2 and more element carbon is

4

converted into methanol. Once the H/C ratio reaches 2, increasing β is the waste of

5

hydrogen; more CO is converted into CO2 and released into atmosphere. It results in

6

decrease of the carbon utilization efficiency. Thus, for this new process, β should be

7

taken between 0.15-0.25.

8

3.3. Scheme 2: the COG-CTM Process without WGS Unit

9

When coking coal to gasification coal ratio is around 7, there is sufficient

10

hydrogen supplied by the COG tri-reforming. The WGS unit can be thus canceled in

11

the new COG-CTM process see Figure 4. As the WGS unit is no longer needed in the

12

COG-CTM process, the main operating parameters of the AGR unit and TRM unit

13

change accordingly. The simulation is conducted and results are as shown in Table S4

14

in the Supporting Information. If scale of the coal gasification is 2 Mt/y, the coking

15

scale is 14 Mt/y. There is still no such scale of coal coking plant in China. However,

16

this new COG-CTM process without the WGS unit can be used for planning new

17

industrial parks.

18

3.4. Carbon Utilization Efficiency and Energy Efficiency

19

Based on the 2 Mt/y scale of the coal processing, mass and energy consumption

20

of the COG-CTM processes with or without WGS are simulated and analyzed with

10



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1

Aspen Plus. A comparison of key efficiency index among COG-CTM, COG-CTM

2

without WGS, and CTM19, is shown in Table 1.

3

Compared to conventional CTM process, COG-CTM process only converted 23%

4

of CO to H2 and CO2. The carbon utilization efficiency increases from 40.7% to 45%,

5

CO2 emission decreases by 43.7%. Its total energy input is significantly reduced due

6

to the high carbon utilization efficiency. Much smaller amount of coal, as raw

7

material, is needed to produce the same amount of methanol. In consequence, the

8

energy efficiency increases 11.4%. For the COG-CTM process without WGS, the

9

carbon utilization efficiency increases from 40.7% to 55.2%. CO2 emission decreases

10

by 61.2%. Since the increase of the carbon utilization efficiency, the coal consumption

11

of the COG-CTM process without WGS is only 28% in comparison to the

12

conventional CTM process. The energy efficiency of the COG-CTM process without

13

WGS increases 16.8% compared to the CTM process.

14

The integrated process performs better when α is around 7. However, this α value

15

means the bigger production scale and more capital investment. If it is a planning for

16

an industrial park or an integrated project, the COG-CTM process without WGS with

17

α close to 7 could be promising and attractive.

18

3.5. Economic performance

19

The analysis of economic performance has been conducted for the COG-CTM

20

process with/without WGS unit, including total capital investment and production

21

cost, to validate its applicability at industrial scale. 11


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1

Analysis of total capital investment

2

The total capital investment includes fixed investment and variable cost. Fixed

3

investment is estimated by Eq. (10),20 according to the benchmark case shown in

4

Table S5 in the Supporting Information.

5

I 2 = θ ⋅ I1 ⋅ (

6

where I1 and Q1 are the fixed capital investment and the production capacity of the

7

current project; I2 and Q2 are the fixed capital investment and the production capacity

8

of the planned project; θ is the domestic-made factor; n is scale exponent, n=0.6 is a

9

common value for chemical processes.

Q2 n ) Q1

(10)

10

The components of the total capital investment could be determined according to

11

their ratios to the equipment investment. The ratios are shown in Table S6 in the

12

Supporting Information and the calculation follows Eq. (11)21

13

TCI = I ⋅ (1 + ∑ RFi )

(11)

i

14

where TCI the total capital investment, I is the fixed capital investment, and RFi is the

15

ratio factor of capital investment of component i.

16

The economic analysis shows the total capital investment of the CTM process is

17

about 1.55×109 CNY, COG-CTM process is 1.72×109 CNY, and the COG-CTM

18

process without WGS is 1.94×109 CNY. The total capital investment of COG-CTM

19

process (Scheme 1) is 10% higher than that of conventional CTM process. The main

20

reason for the increasing cost is because COG-CTM adds a COG clean and a methane 12



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1

separation unit. The total capital investment of COG-CTM process without WGS unit

2

(Scheme 2) is 24% higher than that of conventional CTM process. The co-feed

3

process removes the WGS unit, however the COG handling scale increases up to 2.4

4

times than scheme 1. This leads to the raise of capital investment of COG clean and a

5

methane separation unit. The distribution of total capital investment for the two

6

schemes is shown in Figure 8.

7

Analysis of production cost

8

The estimation of the production cost is based on the work of Peters22. The unit

9

price of raw material and utilities can be found in Table S7 in the Supporting

10

Information. The adopted prices of raw materials are the average prices of coal and

11

COG in 2012.5

12

The basis for comparison of the CTM and the COG-CTM processes are the costs

13

of production of one ton of methanol products. The production costs of 1 t of

14

methanol in the CTM is approximately 1840 CNY/t, the COG-CTM is 1980 CNY/t,

15

and the COG-CTM without WGS is 2040 CNY/t. The comparison of the costs for

16

both process is shown in Figure 9.

17 18

4. CONCLUSIONS

19

This paper proposes an integrated coke-oven gas tri-reforming and coal

20

gasification to methanol process, in which the tri-reforming unit makes the CH4 of

21

COG react with CO2 of coal gasification for the purpose of CO2 mitigation and 13


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1

efficiency improvement. The integrated process takes advantage of the wasted COG

2

in China’s coke industry, what allows to optimize the allocation of resources and

3

enhances the economic value of COG and CTM processes.

4

Two schemes of the integrated process are analyzed. (1) For integration of

5

existing industrial scale of coking plant and coal gasification plant, the scale ratio of

6

coal coking to coal gasification is designed as 3. The carbon utilization efficiency and

7

the energy efficiency of the integrated process is 45% and 62.4%, which increase by

8

4.3% and 11.4% when compared to conventional CTM process. (2) For a new

9

planning industrial park or an integrated project, the scale ratio of coal coking to coal

10

gasification can be designed as 7 and the WGS unit could be canceled in the

11

integrated process. The carbon utilization efficiency and the energy efficiency of the

12

integrated process is 55.2% and 67.8%, which increase by 14.5% and 16.8% when

13

compared to conventional CTM process.

14

The economic analysis shows that the production cost for the COG-CTM

15

Process with/without WGS Unit are 1980 CNY/t and 2040 CNY/t, which is 7-10%

16

higher than that for CTM process. However, this disadvantaged will be disabused if

17

the carbon tax is taken consideration in the future.

18 19

AUTHOR INFORMATION

20

Corresponding Author

21

* E-mail: [email protected], Tel: +86-20-87113046 14



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1 2

Notes The authors declare no competing financial interest.

3 4

ACKNOWLEDGMENTS

5

The authors are grateful for financial support from the China Natural Science

6

Foundation project (No. 21136003 & 21306056), the National Basic Research

7

Program (No. 2012CB720504 & 2014CB744306) and Guangdong Province NSF

8

team project (S2011030001366).

9 10

NOMENCLATURE

11 12 13 14 15 16 17 18 19 20

AGR COG-CTM CTM DMR H/C MPO SMR TRM WGS

21

Notations in Formulation

22 23 24 25 26 27 28 29 30

P m, n k S Ein, out F TCI I Q

Acid gas removal Coke-oven gas assisted coal to methanol Coal to methanol Dry methane reforming Hydrogen to carbon ratio Methane partial oxidation Steam methane reforming Tri-reforming of methane Water gas shift

Equilibrium pressure Reaction order Reaction rate constants Capacity of coal gasification or coal coking, t/a Energy of the target product and the total input energy Mole flow rate, mol/h Total capital investment Fixed capital investment Production capacity 15


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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

RFi f

Ratio factor of capital investment Carbon utilization efficiency, %

3

Greek Letters

4 5 6 7 8

α η Φ β θ

Capacity ratio of coal gasification to coal coking Carbon utilization efficiency Energy efficiency CO shift degree domestic-made factor

9 10

REFERENCES

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

[1] Yi, Q.; Fan, Y.; Li, W.; Feng, J. CO2 Capture and Use in a Novel Coal-Based Polygeneration System. Industrial & Engineering Chemistry Research 2013, 52, (39), 14231-14240. [2] Yang, S.; Yang, Q.; Li, H.; Jin, X.; Li, X.; Qian, Y. An Integrated Framework for Modeling, Synthesis, Analysis, and Optimization of Coal Gasification-Based Energy and Chemical Processes. Industrial & Engineering Chemistry Research 2012, 51, (48), 15763-15777. [3] Bermúdez, J. M.; Arenillas, A.; Luque, R.; Menéndez, J. A. An overview of novel technologies to valorise coke oven gas surplus. Fuel Process Technology 2013, 110, 150-159. [4] Razzaq, R.; Li, C.; Zhang, S. Coke oven gas: Availability, properties, purification, and utilization in China. Fuel 2013, 113, 287-299. [5] Man, Y.; Yang, S.; Zhang, J.; Qian, Y. Conceptual design of coke-oven gas assisted coal to olefins process for high energy efficiency and low CO2. Applied Energy 2014, 133, 197-205. [6] Yi, Q.; Feng, J.; Li, W. Y. Optimization and efficiency analysis of poly-generation system with coke-oven gas and coal gasified gas by Aspen Plus. Fuel 2012, 96, 131-140. [7] Cañete, B.; Gigola, C. E.; Brignole, N. B. Synthesis Gas Processes for Methanol Production via CH4 Reforming with CO2, H2O, and O2. Industrial & Engineering Chemistry Research 2014, 53, (17), 7103-7112. [8] Lee, S-H.; Cho, W.; Ju, W-S.; Cho, B-H.; Lee, Y-C.; Baek, Y-S. Tri-reforming of CH4 using CO2 for production of synthesis gas to dimethyl ether. Catalysis today 2003, 87, 133-137. [9] Chung, J.; Cho, W.; Baek, Y.; Lee, C. Optimization of KOGAS DME process from demonstration long-term test. Transactions of the Korean hydrogen and new energy society 2012, 23, 559-571. [10] Zhang, Y. S.; Cruz, J.; Zhang, S. J.; Lou, H. H.; Benson, T. J. Process simulation and optimization of methanol production coupled to tri-reforming process. International Journal of Hydrogen Energy 2013, 38, 13617-13630. [11] Zhang, Y.; Zhang, S.; Benson, T. A conceptual design by integrating dimethyl ether (DME) production with tri-reforming process for CO2 emission reduction. Fuel Processing Technology 2015, 131, 7-13. [12] Pan, W. Tri-reforming and combined reforming of methane for producing syngas with desired 16



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 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27

H2/CO ratio. PhD thesis. Pennsylvania State University, USA, 2002. [13] Zhang, Y. S.; Zhang, S. J.; Gossage, J. L.; Lou, H. H.; Benson, T. J. Thermodynamic analyses of tri-reforming reactions to produce syngas. Energy & Fuels 2014, 28, 2717-2726. [14] Ministry of Industry and Information Technology of China, Access conditions for coking industry, 2014 [in Chinese]. Available from (accessed 2014.12.10): http://www.miit.gov.cn/n11293472/n11293832/n11293907/n11368223/15919529.html [15] Yang, S.; Yang, Q.; Man, Y.; Xiang, D.; Qian, Y. Conceptual Design and Analysis of a Natural Gas Assisted Coal-to-Olefins Process for CO2 Reuse. Industrial & Engineering Chemistry Research 2013, 52, (40), 14406-14414. [16] Norinaga, K.; Yatabe, H.; Matsuoka, M.; Hayashi, J. Application of an Existing Detailed Chemical Kinetic Model to a Practical System of Hot Coke Oven Gas Reforming by Noncatalytic Partial Oxidation. Industrial & Engineering Chemistry Research 2010, 49, 10565-10571. [17] Man, Y.; Yang, S.; Xiang, D.; Li, X.; Qian, Y. Environmental impact and techno-economic analysis of the coal gasification process with/without CO2 capture. Journal of Cleaner Production 2014, 71, 59-66. [18] Luyben, W. L. Design and Control of the Dry Methane Reforming Process. Industrial & Engineering Chemistry Research 2014, 53, (37), 14423-14439. [19] Xiang, D.; Qian, Y.; Man, Y.; Yang, S. Y. Techno-economic analysis of the coal-to-olefins process in comparison with the oil-to-olefins process. Applied Energy 2014, 113, 639-647. [20] Scholz, M.; Frank, B.; Stockmeier, F.; Falß, S.; Wessling, M. Techno-economic Analysis of Hybrid Processes for Biogas Upgrading. Industrial & Engineering Chemistry Research 2013, 52, (47), 16929-16938. [21] Xiang, D.; Yang, S.; Liu, X.; Mai, Z.; Qian, Y. Techno-economic performance of the coal-to-olefins process with CCS. Chemical Engineering Journal 2014, 240, 45-54. [22] Peters, M. S.; Timmerhaus, K. D. Plant design and economics for chemical engineers. New York (USA): McGraw-Hill; 2002.

17


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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


FIGURES AND TABLES

O2

Coal

Sulfide, CO2

Coal Gasification

1

2

Water Gas Shift

6

Acid Gas Removal

9 Syngas

4

CO2 7

O2 Coke-oven gas

Gas Cleaning

Methane Separation

Methanol Synthesis

3

Trireforming 5

H2O 8

Figure 1. Schematic diagram of the COG-CTM process

18


Methanol


0.7 0.6 0.5 H2 mole fraction

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

0.4 0.3 0.2

0.1 Mpa

0.1

0.5 Mpa 1 Mpa

0 773

873

973

1073

1173

1273

Temperature (K)

Figure 2. Mole fraction of H2 with different pressure and temperature

19


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0.4

0.3 CO mole fraction

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


0.2

0.1 Mpa

0.1

0.5 Mpa 1 Mpa 0 773

873

973

1073

1173

1273

Temperature (K)

Figure 3. Mole fraction of CO with different pressure and temperature

20



0.7

12

H2 CO H/C ratio

0.6

10

0.5

8

0.4 6 0.3 4

0.2

H/C ratio

Mole fraction

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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2

0.1 0 773

873

973

1073

1173

0 1273

Temperature (K)

Figure 4. Parametric analysis of tri-reforming reaction temperature

21


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70

60 2 50 1.5 40 1 30

0.5

Carbon utilization efficiency (%)

2.5

H/C ratio (kmol/kmol)

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


20 0

1

2

3

4

5

6

7

8

9

10 11 12 13

Coking coal/gasification coal (t/t)

Figure 5. The effect of α on H/C ratio of syngas and carbon utilization efficiency

22



2.8 2.6 45 2.4 2.2 2

40

1.8 1.6 35 1.4

Carbon utilization efficiency (%)

50

3

H/C (kmol/kmol)

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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1.2 1

30 0

0.1

0.2

0.3

0.4

0.5

CO shift degree (kmol/komol)

Figure 6. The effect of β on H/C ratio and carbon utilization efficiency

23


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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


O2

Coal

Sulfide, CO2

Coal Gasification

1

5

Acid Gas Removal

8 Syngas

3

CO2

O2 Coke-oven gas

Gas Cleaning

Methane Separation

2

Methanol Synthesis

6

Trireforming 4

H2O 7

Figure 7. Schematic diagram of COG-CTM process without WGS unit

24


Methanol


7 Total capital investment (109 RMB)

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

6

construction and contractor's fee

5

buildings and land

engineering and supervision instruments,piping and electrical equipment and installation

4 3 2 1 0 CTM

COG-CTM

COG-CTM w/o WGS

Figure 8. Total capital investment

25


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2500

distribution and selling costs administrative costs plant overhead costs depreciation operating & maintenance utilities raw material

2000 RMB/t

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


1500

1000

500

0 CTM

COG-CTM

COG-CTM w/o WGS

Figure 9. Production cost

26



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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Table 6. Key Indicators Comparison of COG-CTM, COG-CTM without WGS, and CTM Item

COG-CTM

Input Coal (t/t methanol) COG (m3/t methanol) Water (t/t methanol) Electricity(kWh/t methanol) Steam (MJ/t methanol) Total energy input (MJ) Output Methanol energy (MJ) Energy efficiency (%) Carbon utilization efficiency (%) CO2 emission (t/t methanol)

COG-CTM w/o WGS

CTM

0.63 639 9.8 446 5893 36323

0.37 883 8.6 410 6060 33417

1.32 N/A 14 548 5403 44468

22660 62.4 45.0 1.61

22660 67.8 55.2 1.11

22660 51.0 40.7 2.86

27


Integrated Process of Coke-Oven Gas Tri-Reforming and Coal

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