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Research Papers: Fuel Combustion

# Novel Coal-Steam Gasification With a Thermochemical Regenerative Process for Power GenerationPUBLIC ACCESS

[+] Author and Article Information
Dandan Wang

Institute of Engineering Thermophysics,
Beijing 100190, China;
University of Chinese Academy of Science,
Beijing 100049, China
e-mail: wangdandan@iet.cn

Sheng Li

Institute of Engineering Thermophysics,
Beijing 100190, China;
University of Chinese Academy of Science,
Beijing 100049, China
e-mail: lisheng@iet.cn

Lin Gao

Institute of Engineering Thermophysics,
Beijing 100190, China;
University of Chinese Academy of Science,
Beijing 100049, China
e-mail: gaolin@iet.cn

Handong Wu

Institute of Engineering Thermophysics,
Beijing 100190, China;
University of Chinese Academy of Science,
Beijing 100049, China
e-mail: wuhandong@iet.cn

Hongguang Jin

Institute of Engineering Thermophysics,
Beijing 100190, China;
University of Chinese Academy of Science,
Beijing 100049, China
e-mail: hgJin@iet.cn

1Corresponding author.

Contributed by the Advanced Energy Systems Division of ASME for publication in the JOURNAL OF ENERGY RESOURCES TECHNOLOGY. Manuscript received January 4, 2018; final manuscript received April 7, 2018; published online May 7, 2018. Assoc. Editor: Abel Hernandez-Guerrero.

J. Energy Resour. Technol 140(9), 092203 (May 07, 2018) (9 pages) Paper No: JERT-18-1010; doi: 10.1115/1.4039978 History: Received January 04, 2018; Revised April 07, 2018

## Abstract

In this paper, a novel high-efficiency coal gasification technology is proposed in which a regenerative unit is applied to recover syngas sensible heat to generate steam; then, the high-temperature steam is used to gasify coke from a pyrolyzer. Through such a thermochemical regenerative unit, the sensible heat with a lower energy level is upgraded into syngas chemical energy with a higher energy level; therefore, high cold gas efficiency (CGE) is expected from the proposed system. aspenplus software is selected to simulate the novel coal gasification system, and the key parameters are validated by experimentation. Then energy, exergy, and energy-utilization diagram (EUD) analyses are applied to disclose the plant performance enhancement mechanism. It is revealed that 83.2% of syngas sensible heat can be recovered into steam agent with the CGE upgraded to 90%. In addition, with the enhancement of CGE, the efficiency of an integrated gasification combined cycle (IGCC) based on the novel gasification system can be as high as 51.82%, showing a significant improvement compared to 45.2% in the general electric company (GE) gasification-based plant. In the meantime, the irreversible destruction of the gasification procedure is reduced to 25.7% through thermochemical reactions. The increase in the accepted energy level (Aea) and the decreases in the released energy level (Aed) and heat absorption (ΔH) contribute to the reduction in exergy destruction in the gasification process. Additionally, since the oxygen agent is no longer used in the IGCC, 34.5 MW exergy destruction in the air separation unit (ASU) is avoided.

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## Introduction

Coal is one of the major energy resources worldwide because of its low price and huge reserves [1]. Coal accounts for 29.2% of the global primary energy consumption and accounts for approximately 40% of the world's electricity generation [2,3]. Since conventional coal utilization, such as direct combustion, is inefficient and environmentally unfriendly, it is necessary to develop efficient, economic, and clean coal conversion approaches. Coal gasification is regarded as such an approach. Coal gasification is a thermochemical process in which coal reacts with steam/oxygen or some other agents to produce syngas for further processing. Compared with direct combustion, via the gasification process, the contaminants in syngas are concentrated and can be eliminated more easily, and the utilization of coal can be more efficient. For many processing industries, such as liquid fuel or chemical production, integrated gasification combined cycle (IGCC) power generation, and poly generation systems, coal gasification is the key procedure of the entire plant. Thus, determining methods to improve the performance of gasification has attracted much interest and concern since the early 1920s, when this technology first became widespread [410].

Cold gas efficiency (CGE) is a quite vital parameter to measure the performance of a coal conversion process. CGE represents the ratio of the chemical energy of syngas to that of coal, as shown in Eq. (1). Improving the CGE of the gasifier corresponds to more chemical energy contained in coal being converted into the chemical energy of syngas; such an increased conversion is helpful to increase the efficiency of the whole IGCC or chemical production plant Display Formula

(1)$CGE=GsyngasLHVsyngasGcoalLHVcoal$

German Lurgi gasifier is well known as a type of fixed bed technology. After nearly 80 years of development, the third and fourth generations can reach a relatively high CGE (over 80%) with wide adaptability to coal. Fluid bed gasification is also an important technology that includes German High Temperature Winkler, U.S. U-gas, Kellogg Rust Westinghouse, and Kellogg Brown Root. With the increase in gasification pressure and decrease in heat dissipation in its development process, the highest CGE of fluid bed gasifiers is approximately 82% [4,5]. In addition, as the most commonly used entertained bed technologies, U.S. general electric company (GE) (Texaco, White Plains, NY) and Shell gasification can reach CGEs of 77.5% and 83% in the latest generation, respectively. In recent years, some new coal gasification technologies have been proposed, such as HT-L (Beijing, China) (CGE 80-82%) [6], EAGLE (Yokohama, Japan) (CGE 82%) [7,8], and two-stage entrained flow coal dry powder gasifier (CGE 83.2%) proposed by China Huaneng Group (Beijing, China) [9]. Nippon Steel & Sumikin Engineering Co., Ltd. (Tokyo, Japan), put forward an entrained flow gasifier with a two-stage reactor (ECOPRO®); according to the pilot plant testing, the CGE of this approach could reach 85% (the world's best level) [10]. The CGE development of main gasification technologies is shown in Fig. 1 in which the symbols in green, gray, and mauve represent the CGE changes of fixed bed, fluid bed, and entertained bed gasifiers, respectively.

Despite long-term development, the CGE of current gasification technologies is still limited to 75–83% and is difficult to increase, primarily because coal is partially oxidized to provide heat for gasification, and approximately 15–28% of the fuel chemical energy will be converted into the sensible heat of syngas instead of chemical energy in products [11], as shown in Fig. 2(a). Insufficient utilization of chemical energy also leads to large irreversibility in the gasification process, which accounts for approximately 20–30% exergy destruction in IGCC/coal to chemical plants. For an IGCC system, its efficiency could only reach up to 38–47.4% (based on GE 9F-class gas turbine) [12,13].

Generally, the sensible heat of syngas is recovered to produce steam for a Rankine Cycle for electricity generation. Note that the thermal efficiency of this bottom cycle of IGCC is only approximately 40%, which is much lower than the combined cycle (55%). Thus, a better utilization mode is to regenerate the high-temperature heat and make it re-enter chemical product through a thermochemical process for the combined cycle. When more physical energy is converted into chemical energy, higher CGE and IGCC efficiency can be expected.

Since water/steam is low cost and has high latent heat, it is appropriate for use both as a heat reoccupied medium and a gasification agent in our novel method. Moreover, the use of a steam agent can avoid the energy consumption and investment of an air separation unit (ASU). Researchers also found that steam has higher reaction activity and can produce syngas with a higher heating value than air or CO2 [14,15]. Wang et al. [16] discovered that when the water vapor content increased, the hydrogen in the syngas could be significantly enhanced from 37.67 g/kg-fuel to 74.58 g/kg-fuel. Karatas et al. [17] investigated the influence of gasification agents on the syngas products using a bubbling bed gasifier experimentally. The results showed that the lower heating value (LHV) of synthetic gas under steam atmosphere is double than that under the air/CO2 atmosphere. Koba and Ida [18] reported that the reaction rate of lignite-steam gasification is 2–5 times higher than that of CO2 gasification. Niu et al. [19] experimentally investigated the syngas products of pine-steam gasification and found that the H2 content can reach 47.7% at 950 °C. Aranda et al. [20] concluded that the conversion of high-ash coal is favored at a higher steam partial pressure and that more than 20% carbon could be quickly converted in the devolatilization stage. Huo et al. [21] conducted gasification experiments using a thermo-gravimetric analyzer and found that it has more effect on the char-steam gasification which is more affected by the pore diffusion and its initial rate is several times faster compared with CO2 gasification. Thus, in this work, steam is selected as the gasification agent and heat regenerative medium [22].

Few studies have been reported in the literature on syngas sensible heat regeneration (HR) in coal gasification. In this paper, a novel coal gasification technology used for IGCC is proposed in which a regenerative system is applied to recover syngas sensible heat to generate steam and then the high-temperature steam is used to gasify the coke from pyrolyzer, as shown in Fig. 2(b). Through such a thermochemical regenerative system, the sensible heat with a lower energy level is upgraded into syngas chemical energy with a higher energy level. Moreover, an ASU is unnecessary since the O2 agent is not required. After cooling and desulfur purification, syngas from the novel gasification system will be sent to a combined cycle unit for power generation.

In this study, the proposed coal gasification and IGCC system is simulated by aspenplus software, and the results are validated by the experimental data. The thermodynamic performance of the proposed method is compared with a conventional IGCC plant. Furthermore, the mechanism of CGE enhancement is examined through exergy and energy-utilization diagram (EUD) analyses.

## Description of an Integrated Gasification Combined Cycle Plant Based on Novel Coal Gasification

###### Design of the Novel System.

A proposed IGCC system based on a novel coal gasification technology is illustrated in Fig. 3(a). In the novel system, the feedstock is divided into two types: one type is used for gasification and the other type is for heating supply. First, the gasification coal is sent to a high-temperature pyrolyzer and converts into coke and hydrogen-rich gaseous products. Next, the gaseous products are sent into the #1 heat exchanger to preheat the gasification steam agent. Meanwhile, the coke from pyrolyzer is gasified at 1000 °C, 2.0 MPa with high-temperature steam [23]. The raw syngas generated mainly contains H2, CO, CO2, and H2O. Afterward, the sensible thermal energy of the high-temperature gasification syngas will be recovered via the #2 heat exchanger, increasing the temperature of the steam agent to approximately 550–600 °C. Both of the pyrolysis and coke-steam gasification processes are endothermic, and the heat is derived from an external coal combustion chamber. The cold gas cleaning unit (CGCU) is indispensable since the raw syngas contains small amounts of H2S and COS, which might cause equipment corrosion and environmental problems. After CGCU, the raw pyrolysis and gasification syngas will combust in the combustion chamber and produce high temperature flue gas to the gas turbine (GT) for electricity generation. Exhaust gas from GT will be used to start a Rankine cycle in the heat recovery steam generator (HRSG).

The main features of the novel system are as follows: (1) via the steam agent, the sensible thermal energy of synthesis gas re-enters the gasifier and is converted into chemical energy of the products through thermochemical reactions, which in turn effectively increases the CGE in the coal gasification process; (2) an air separation unit is not required because the oxygen agent is no longer used; and (3) coal is converted in stages in the novel process, where some components, especially the hydrogen-rich volatiles, can be easily released through pyrolysis compared with traditional one-step gasification approaches. The higher H2/CO ratio will be more propitious to chemical production processes.

###### Description of the Reference System.

A GE entrained flow gasifier is one of the most common types of gasifiers because it can work at high temperature and it applies to solid or liquid fuels with high carbon conversion [24]. In this work, an IGCC plant based on the GE process is selected as the reference system. The plant consists of five important parts: (1) a gasification unit, (2) a waste heat boiler (WHB), (3) an ASU, (4) a cold gas clean unit, and (5) a combined cycle that includes GT and HRSG.

Figure 3(b) illustrates the simplified process flow diagram. Coal is pulverized to small size and mixed with water to get coal-slurry (at a coal concentration of 63%), and then, the slurry is pumped into the gasifier with 98% pure oxygen provided by an ASU. The ASU adopts a cryogenic process and requires large electricity consumption for air compression and separation.

The gasifier is designed to be a down flow entrained bed and works at a high pressure. In the gasifier, the chemical reactions occur rapidly at a temperature over 1200 °C [25]. This raw syngas leaves the gasifier at 1346 °C and 3.0 MPa, and it is then sent to a WHB for heat recovery to generate steam for the Rankine cycle. Afterward, the midtemperature syngas (approximately 350 °C) is further cooled to satisfy the temperature requirement of desulfurization and conducted heat exchange with the cold clean gas from CGCU.

After desulfurization and purification, the cold clean syngas is reheated and then combusted in the chamber for electricity generation.

###### Operation Conditions and Main Assumptions.

The process of the novel conceptual IGCC plant and traditional IGCC based on the slurry-feed GE gasifier is simulated by Aspen Plus 11.0 software. aspenplus is a universal software that has a rich database of physical properties and assists industries to optimize their production flow and manufacturing support systems. In this work, a method using the Peng–Robinson state equation with Boston–Mathias modifications (PR-BM) is chosen as the global method [2629]. Coal is designated as a nonconventional component. The gasification process is simulated by the R-Gibbs block which can use minimizing Gibbs free energy to model chemical equilibrium. Since the R-Gibbs block cannot consider nonconventional components, coal should be divided into some elements such as carbon (C), hydrogen (H), oxygen (O), nitrogen (N), and sulfur (S) through the R-Yield model. The products content of R-Yield block should be equal to the origin feedstock and it is determined through the ultimate analysis. The feed inputs are of the same total amount in these two systems. The coal is Datong bituminous coal, and its ultimate analysis is illustrated in Table 1.

Gas turbine and HRSG with steam turbine (ST) in this paper are based on GE PG9351FA and a triple-pressure reheat steam water system, respectively [3032]. To simplify the simulation, it is assumed that the whole system operates at steady-state. The design conditions of the two systems are shown in Table 2.

## System Performance Evaluation Method and Criteria

Some performance criteria are presented for evaluation of the plant's performances.

Equations (2) and (3) illustrate the thermal and exergy efficiency of an IGCC plant, respectively, Display Formula

(2)$ηth=WNETGcoalLHVcoal$
Display Formula
(3)$ηex=WNETEXin$
Display Formula
(4)$Gcoal=Ggasi+Gheat$
Display Formula
(5)$WNET=WGT+WST−WAUX$

Gcoal is the total mass flow rate of total coal input. Gcoal includes the mass flow rate of gasification coal Ggasi and heating supply coal Gheat. WNET represents the net power output of the whole plant and LHVcoal is the lower heating value of coal. EXin represents the whole exergy input of the entire plant. In Eq. (5), WGT refers to the net power output of the gas turbine. WST denotes the power output of the steam turbine. WAUX is the auxiliary power supply for the pumps, compressors, etc.

The exergy consists of chemical and physical exergies, as illustrated in the following equation: Display Formula

(6)$e=eph+ech$

The specific physical eph can be calculated using Eq. (7), where h and h0 refer to the specific enthalpies of the steam flow at real and standard conditions, respectively; s and s0 denote the specific entropies of the steam flow at real and standard conditions, respectively, Display Formula

(7)$eph=(h−h0)−T0(s−s0)$

For different substances at a standard condition, the chemical exergy ech can be obtained in the literature [33,34]. For a solid fuel, such as coal, its specific exergy can be determined using the following equation: Display Formula

(8)$efuelch=(LHV+w%hw)φdry+9417Ys$

where LHV is the abbreviation for lower heating value of the fuel; w% and hw denote the mass fraction of moisture in the fuel and the latent heat of water at T0, respectively; φdry is a coefficient related to the composition of the solid fuel, and when the mass ratio of oxygen to carbon is less than 0.667, it can be calculated with Eq. (9); Ys is the mass fraction of sulfur in the fuel Display Formula

(9)$φdry=0.1182YhYc+0.061YoYc+0.0404YnYc+1.0437$

where Yh, Yc, Yo, and Yn represent the mass fraction of H, C, O, and N in the fuel, respectively.

Exergy analysis can describe the exergy destruction of each component in a whole system. For a control volume, the exergy balance at a standard condition can be described by the following equation [35]: Display Formula

(10)$E˙x=∑j=1m1−T0/TjQ˙j−W˙+∑l=1nm˙i,lei,l−∑k=1pm˙o,keo,k$

$E˙x$ refers to the exergy destruction corresponding to irreversibility of the control volume, kW; $∑j=1n(1−T0/Tj)Q˙j$ represents the heat exergy input or output in the control volume; $W˙$ is the work output or input in the control volume; T0 and Tj represent the environmental temperature (298.15 K) and the temperature of heat stream j, respectively; $Q˙j$ denotes the heat flow jth; $m˙i,l$ and $ei,l$ are the molar flow rate, kmol/s, and the specific exergy, kJ/kmol, of the inlet stream l, respectively; $m˙o,k$ and $eo,k$ represent the molar flow rate, kmol/s, and the specific exergy, kJ/kmol, of the outlet stream k, respectively.

## Thermodynamic Analyses and Energy Saving Mechanism

###### Compositions of Syngas.

Different from GE gasification, there are two flows of syngas from the pyrolyzer and the gasifier that will be mixed as fuel for the generation unit in the novel method. The compositions of clean syngas from GE and the novel gasification process are illustrated in Fig. 4.

The figure shows that H2 and CO account for a substantial portion of the syngas, with the contents being quite different in the two systems. The content of H2 is 33.9% in the slurry method, and it is 53.4% in the novel method. The CO contents are 53.5% and 41.1% in the GE and our novel method, respectively. Moreover, the CH4 in the novel gasification is obviously higher compared with the traditional approach.

In the novel system, performing pyrolysis and then gasification is one of the main reasons for the high H2 content. H2 in the pyrolysis gas accounts for 37% of the total amount. Another important reason is that H2O is used as the only gasification agent instead of O2, thereby changing the main chemical reactions in the gasification process.

It is generally thought that heterogeneous gas–solid reactions and homogeneous (gas phase) reactions both occurred in a coal/char gasification process, as given below:

Reactions between carbon and oxygen

$R1: C+1/2O2→CO, ΔH=−110.4 kJ/mol;R2: C+ CO2→2CO, ΔH=+173.3 kJ/mol;$

Reaction between carbon monoxide and oxygen

$R3: CO+1/2O2→CO2, ΔH=−283.7 kJ/mol;$

Reactions between carbon and steam

$R4: C+ H2O→H2+CO, ΔH=+135.0 kJ/mol;$

Carbon monoxide shift reaction

$R5:CO+ H2O→H2+CO2, ΔH=−38.4 kJ/mol;$

Hydrogenation of carbon

$R6:C+ 2H2→CH4, ΔH=−84.3 kJ/mol;$

Methane reaction

$R7:CO+ 3H2→CH4+H2O, ΔH=−219.3 kJ/mol$

where R1, R2, R3, and R4 are the main reactions in a GE slurry gasification process, whereas in the novel method, R4 plays the dominant role since steam is the only agent instead of oxygen. Therefore, the H2 content in syngas will be significantly increased, whereas CO will be reduced. Thus, the excess H2 will promote the hydrogenation of carbon (R6) and methane reactions (R7), thereby contributing to the increase in CH4 in the syngas.

According to the previous experiments of coal/coke-steam gasification [3639], the H2 content is always in the range of 49.5–65%, the CO content is in the range of 30–47.4%, CO2 accounts for nearly 2–15%, and CH4 is always lower than 5%. The simulation results in our work agree well with the experimental data, as shown in Table 3.

###### Thermal and Exergy Balance of Gasification Systems.

The steam obtained from heat exchangers #1 and #2 in the novel system can be sent directly to a steam turbine for electricity generation (steam-coal gasification with EG) or can be used only for gasification (steam-coal gasification with heat regeneration). These two options will be analyzed in this section to determine which option is better.

In Tables 4 and 5, thermal and exergy balances of GE gasification, steam-coal gasification with EG, and steam-coal gasification with HR are presented. Because O2 agent is required, extra power input and energy loss are found to occur in the ASU for the GE gasification system. In the steam coal gasification systems, regardless of the utilization mode of sensible heat adopted, the heating value of the syngas product is always higher than the reference GE system.

For the GE gasification system, the steam-coal gasification with EG system, and the steam-coal gasification with HR system, the total exergy outputs are 76%, 80%, and 85.5%, respectively. When the sensible heat is only used for the steam agent production, the system also shows a better exergy performance, primarily because through a thermochemical process, the physical energy has been converted into chemical energy of syngas and the irreversible destruction of the gasification procedure has decreased by 5% points compared with the mode of steam-coal gasification with EG.

###### Effects of the Regenerative Unit in the Novel System.

Figure 5 shows the utilization of sensible heat in syngas. The leftmost points indicate that sensible heat is only used for electricity generation in ST. The rightmost points indicate that sensible heat is only used for agent preheating. Because of the limit of the minimal temperature approach in the heat regenerative unit, the maximum recovered heat into steam agent is approximately 83.2%. At this moment, approximately 72.9 MW of the heat in syngas is recovered into the gasification agent, and the temperature of the gasification steam agent is increased to 849 K (576 °C). Moreover, 21% of the heating coal is saved, and the flow rate of the syngas will be increased to 37 kg/s.

It can be seen that as the ratio of sensible heat into chemical energy increases, the percentage of heating coal in the novel system decreases from 33.74% to 26.68%, as shown in Fig. 6. Moreover, the LHV of syngas increases to 24.07 MJ/kg-coal because more fuel is used for gasification instead of heating supply.

###### Thermal Performances of Power Plants.

In Fig. 7, the changes in the power outputs of the GT and the ST along with the CGE and thermal efficiency of the IGCC are illustrated [40]. When the ratio of sensible heat to chemical energy increases, the CGE of the novel gasification method gradually increases from 81.44% to 90.12%. Higher CGE indicates that more energy is sent to the gas turbine in IGCC; thus, the power output of GT is increased from 244.61 MW to 270.26 MW. Because the sensible heat into steam turbine is decreased, power output of ST will be reduced by 9 MW. This reduction is much smaller than the rise of the GT output. As a result, the thermal efficiency of the novel IGCC plant will be increased from 49.63% to 51.82% with the heat to chemical energy ratio increasing.

To achieve better performances of IGCC, it is recommended that sensible heat in syngas be only used for preheating gasification agent; this approach is selected in our following study.

The gasification coal in the novel system is less than that in the reference slurry system since an amount of coal is used for the heating supply. Nevertheless, the thermal performance of the novel IGCC plant is much better than that of the reference plant based on GE gasification, as shown in Table 6.

In the novel system, because of the thermal–chemical conversion through the regenerative unit, a higher H2 concentration in syngas is achieved and the CGE of the novel gasifier can be 1/7 higher compared with 76.9% in GE gasification. Since steam is no longer sent to the ST in the novel gasification method, the power generation of the ST will be decreased by 3.4% points. Moreover, because of the syngas chemical energy increase, the power generation of GT is increased to 270.25 MW, which is 5% points higher than the reference system.

Because an oxygen agent is no longer used in this novel system, 34.49 MW power consumption in the ASU is saved. In sum, the thermal efficiency of the novel IGCC system can be up to 51.64%.

###### Exergy Analysis of Power Plants.

The exergy analysis is conducted to identify the energy saving mechanism of the total novel plant [41,42]. Through Eqs. (6)(11), the exergy destructions of each unit are calculated; the results are illustrated in Table 7.

The exergy destruction analysis reveals the energy utilization of different units in the reference and novel IGCC systems. The results reveal that the exergy output in novel IGCC system can be increased by 50.03 MW, i.e., 14.4% compared with the reference system. The novel coal gasification process has a distinct advantage since 34.1 MW exergy destruction is avoided compared with the reference gasification unit. Moreover, eliminating the ASU corresponds to the removal of 34.5 MW exergy destruction from the total novel IGCC system compared to the reference system.

The exergy destructions in the combustion process and gas turbines are a slightly higher because more fuel is produced for electricity generation. In the novel system, because the WHB no longer provides steam for the steam turbine system, the circulation water is less than that of the GE-based plant, and the exergy destructions of the ST and the condensing process are slightly reduced. Overall, the exergy destruction of the novel IGCC system can be 11% less than that of the reference GE system.

###### Energy-Utilization Diagram.

The above analyses reveal that the optimization in coal gasification process is the key factor that is highly conducive to the system energy savings and efficiency improvement. Thus, in this section, an EUD is used to gain further insight into the energy utilization level of the traditional and novel gasification process.

The EUD methodology was developed by Ishida [43,44]. It can be described by the energy level A and the energy change quantity ΔH. The energy level A denotes the ratio of exergy change ΔE to energy change ΔH, as presented in Eq. (11), and it is an important parameter to measure the energy quality of donor or acceptor side in a process Display Formula

(11)$A=ΔEΔH$

In an energy transformation system, energy is released by the donor side and accepted by the acceptor side; thus, the area between energy donor and acceptor curves can represent the exergy destruction [45,46].

Figures 8(a) and 8(b) show the EUDs of the two gasification processes. The shadow represents the exergy destructions.

In the coal-slurry gasification, exothermal reactions (mainly R1 and R3) between carbon and oxygen provide heat for endothermic reactions (mainly R2 and R4) in the gasifier. Aed1 and Aed2 are the energy levels of R3 and R1, respectively, and their average value is approximately 1.02. Aea1, Aea2, and Aea3 represent the energy levels of the temperature rise processes of coal, oxygen, and water, respectively. Aea4 and Aea5 are the energy levels of endothermic reactions R2 and R4. The average energy level Aea of the acceptor side is approximately 0.61. Δε is the exergy destruction of heat dissipation in the coal-slurry gasifier and has a value of 39 MW.

In the novel coal gasification method, the heat for pyrolysis and the coke-gasification process is supplied by an external combustion chamber, the energy level Aed-n of which is approximately 1.005, which is slightly smaller than that of the reference process. Aea1-n and Aea2-n are the temperature rise process of heating coal and air in the external combustion chamber, respectively. Aea3-n, Aea4-n, Aea5-n, and Aea6-n represent the energy levels of the temperature rise process of gasification coal, the pyrolysis process, the temperature rise process of the steam agent, and the endothermic reactions in the gasifier, respectively. Because the steam agent has been preheated and the energy level of the endothermic reaction R4 in the novel gasification is higher than that of GE gasification, the average energy level Aea-n of the acceptor side will be upgraded to 0.682, which is 11.8% higher than that of the reference system. Moreover, ΔΦ and Δγ denote the heat dissipation and flue emissions from external combustion chamber, respectively, with values of 10.7 MW and 18.33 MW, respectively.

Another distinct difference between the two gasification processes is the change in the main absorbed heat ΔH. In the novel gasification method, the energy requirement for the agent temperature increase will significantly decrease, which mainly benefits from the heat regenerative unit. As a result, compared with coal-slurry gasification, the total absorbed heat in the novel method will decrease by 67.06 MW, i.e., 24%. Since the process energy quantity ΔH and the spacing between energy donor and acceptor both decline, the shadow area will be reduced. In conclusion, the irreversible destruction in the novel gasification procedure can be decreased by 26%, which clearly indicates the advantages of the novel gasification process.

## Conclusions

In this paper, we proposed a novel coal gasification system for IGCC power plants in which a regenerative unit is applied to recover syngas sensible heat to generate steam for the gasification of coke. Through energy and exergy analysis, the following conclusions are drawn:

To achieve better performances of IGCC, the sensible heat in syngas should be only used for preheating the gasification agent instead of sending it to a steam turbine. Through the thermochemical regenerative unit in the novel system, at most 83.2% of the heat can be recovered into the steam agent. The CGE can be up to 90.12%, which is 1/7 higher than the GE gasification. The efficiency of an IGCC plant based on the novel gasification system can be up to 51.82%, i.e., 6.6% points higher than the GE-based IGCC plant.

The exergy analysis reveals the energy saving mechanism of the novel system. The novel IGCC plant has a distinct advantage since 34.1 MW irreversible destruction in the gasification procedure and 34.5 MW exergy destruction in the ASU are avoided compared with the reference IGCC plant.

The coal gasification process is the key unit of the whole IGCC plant. The increase in the accepted energy level Aea-n and the decreases in the released energy level Aed-n and the absorbed heat ΔH are the main contributions to the reduction in exergy destruction in the novel gasification system.

The novel coal gasification technology proposed in this paper has a good thermodynamic performance and is a quite promising approach for highly efficient and clean coal utilization.

## Acknowledgements

• National Key R&D Program of China (No. 2016YFB0600803).

• National Nature Science Foundation of China (No. 51776197).

• Youth Innovation Promotion Association CAS (2016130).

## Nomenclature

• A =

energy level

• Aea =

energy level of the acceptor side

• Aed =

energy level of the donor side

• ASU =

air separation unit

• CGCU =

cold gas cleaning unit

• CGE =

cold gas efficiency

• e =

specific exergy at the actual conditions, kJ/kg

• ECH =

chemical energy, kW

• $E˙x$ =

exergy destruction, kW

• EXin =

whole exergy input, kW

• ech =

chemical specific exergy, kJ/kg

• eph =

physical specific exergy, kJ/kg

• EG =

electricity generation

• EUD =

energy-utilization diagram

• Gcoal =

total mass flow rate of total coal input, kg/h

• Gsyngas =

mass flow rate of syngas output, kg/h

• GE =

general electric company

• GT =

gas turbine

• h =

specific enthalpy at the actual conditions, kJ/kg

• hw =

latent heat of water at the standard conditions, kJ/kg

• h0 =

specific enthalpy at the standard conditions, kJ/kg

• HEX =

heat exchanger

• HR =

heat regeneration

• HRSG =

heat recovery steam generator

• IGCC =

integrated gasification combined cycle

• LHV =

lower heating value, kJ/kg

• s =

specific entropy at the actual conditions, kJ/kg

• s0 =

specific entropy at the standard conditions, kJ/kg

• ST =

steam turbine

• Tj =

temperature of heat stream j, K

• T0 =

temperature at the environmental conditions, K

• WAUX =

auxiliary power consumption, kW

• WGT =

power output of the gas turbine, kW

• WNET =

net power output, kW

• WST =

power output of the steam turbine, kW

• WHB =

waste heat boiler

• w% =

mass fraction of moisture in the fuel

• Yc/h/n/o/s =

mass fraction of carbon/hydrogen/nitrogen/oxygen/sulfur in the fuel

• ΔE =

exergy changes in a process, kW

• ΔH =

enthalpy changes in a process, kW

Greek Symbols
• $ηex$ =

exergy efficiency

• $ηth$ =

thermal efficiency

• $φdry$ =

coefficient related to the composition of the solid fuel

Subscripts
• ea-n =

energy acceptor side of the novel system

• ed-n =

energy donor side of the novel system

• gasi =

gasification

• heat =

heating supply

## References

IEA Coal Industry Advisory Board, 2000, Coal in the Energy Supply of China, International Energy Agency, Paris, France, pp. 1–110.
BP, 2016, “BP Statistical Review of World Energy,” BP Global, London, accessed Apr. 28, 2018,
EIA, 2017, “International Energy Outlook 2017,” United States Energy Information Administration, Washington, DC.
Patel, J. G. , 1980, “The U‐GAS® Process,” Int. J. Energy Res., 4(2), pp. 149–165.
Breault, R. W. , 2010, “Gasification Processes Old and New: A Basic Review of the Major Technologies,” Energies, 3(2), pp. 216–240.
CNMHG, 2012, “Introduction of HT-L Pulverized Coal Gasification Technology and Gasifier,” Changzheng Engineering Co., Ltd., Beijing, China.
Kenji, A. , 2015, “The Situation and Progress of the Osaki COOLGEN Blowing-Oxygen IGCC Project,” Nineth Sino Japanese Energy Saving and Environmental Protection Comprehensive Forum, pp. 5–23.
Kouji, O. , 2014, “Oxygen-Blown Coal Gasification System (<Special Articles> Current and Future Status of Integrated Coal Gasification Combined Cycle System),” J. Jpn. Inst. Energy, 93(7), pp. 624–630.
Xu, S. , Ren, Y. , Wang, B. , Xu, Y. , Chen, L. , Wang, X. , and Xiao, T. , 2014, “Development of a Novel 2-Stage Entrained Flow Coal Dry Powder Gasifier,” Appl. Energy, 113, pp. 318–323.
Ariyoshi, D. , Takeda, S. , Kosuge, K. , Mizuno, M. , and Kato, K. , 2016, “Development of High-Efficiency Coal Gasification Technology,” Clean Coal Technology and Sustainable Development, Springer, Singapore, pp. 617–619.
Matsuoka, K. , Kajiwara, D. , Kuramoto, K. , Sharma, A. , and Suzuki, Y. , 2009, “Factors Affecting a Team Gasification Rate of Low Rank Coal Char in a Pressurized Fluidized Bed,” Fuel Process. Technol., 90(7–8), pp. 895–900.
Brdar, R. D. , and Jones, R. M. , 2000, “GE IGCC Technology and Experience With Advanced Gas Turbines,” GE Power Systems, Schenectady, NY, Paper No. GER-4207.
Maurstad, O. , 2005, “An Overview of Coal Based Integrated Gasification Combined Cycle (IGCC) Technology,” Massachusetts Institute of Technology, Cambridge, MA, Report No. MIT LFEE 2005-002 WP.
Irfan, M. F. , Usman, M. R. , and Kusakabe, K. , 2011, “Coal Gasification in CO2 Atmosphere and Its Kinetics since 1948: A Brief Review,” Energy, 36(1), pp. 12–40.
Lv, P. , Yuan, Z. , Ma, L. , Wu, C. , Chen, Y. , and Zhu, J. , 2007, “Hydrogen-Rich Gas Production From Biomass Air and Oxygen/Steam Gasification in a Downdraft Gasifier,” Renewable Energy, 32(13), pp. 2173–2185.
Wang, R. , Huang, Q. , Lu, P. , Li, W. , Wang, S. , Chi, Y. , and Yan, J. , 2015, “Experimental Study on Air/Steam Gasification of Leather Scraps Using U-Type Catalytic Gasification for Producing Hydrogen-Enriched Syngas,” Int. J. Hydrogen Energy, 40(26), pp. 8322–8329.
Karatas, H. , Olgun, H. , and Akgun, F. , 2013, “Coal and Coal and Calcined Dolomite Gasification Experiments in a Bubbling Fluidized Bed Gasifier Under Air Atmosphere,” Fuel Process. Technol., 106, pp. 666–672.
Koba, K. , and Ida, S. , 1980, “Gasification Reactivities of Metallurgical Cokes With Carbon Dioxide, Steam and Their Mixtures,” Fuel, 59(1), pp. 59–63.
Niu, Y. , Han, F. , Chen, Y. , Lyu, Y. , and Wang, L. , 2016, “Experimental Study on Steam Gasification of Pine Particles for Hydrogen-Rich Gas,” J. Energy. Inst., 90(5), pp. 715–724.
Aranda, G. , Grootjes, A. J. , Van der Meijden, C. M. , Van der Drift, A. , Gupta, D. F. , Sonde, R. R. , Poojari, S. , and Mitra, C. B. , 2016, “Conversion of High-Ash Coal Under Steam and CO2 Gasification Conditions,” Fuel Process. Technol., 141(1), pp. 16–30.
Huo, W. , Zhou, Z. , Wang, F. , and Yu, G. , 2014, “Experimental Study of Pore Diffusion Effect on Char Gasification With CO2 and Steam,” Fuel, 131(1), pp. 59–65.
Jangsawang, W. , Klimanek, A. , and Gupta, A. K. , 2006, “Enhanced Yield of Hydrogen From Wastes Using High Temperature Steam Gasification,” ASME J. Energy Resour. Technol., 128(3), pp. 179–185.
Messenböck, R. C. , Dugwell, D. R. , and Kandiyoti, R. , 1999, “CO2 and Steam-Gasification in a High-Pressure Wire-Mesh Reactor: The Reactivity of Daw Mill Coal and Combustion Reactivity of Its Chars,” Fuel, 78(7), pp. 781–793.
Tola, V. , Cau, G. , Ferrara, F. , and Pettinau, A. , 2016, “CO2 Emissions Reduction From Coal-Fired Power Generation: A Techno-Economic Comparison,” ASME J. Energy Resour. Technol., 138(6), p. 061602.
Halama, S. , and Hartmut, S. , 2016, “Reaction Kinetics of Pressurized Entrained Flow Coal Gasification: Computational Fluid Dynamics Simulation of a 5 MW Siemens Test Gasifier,” ASME J. Energy Resour. Technol., 138(4), p. 042204.
Peng, D. Y. , and Robinson, D. B. , 1976, “A New Two-Constant Equation-of-State,” Ind. Eng. Chem. Fundam., 15(1), pp. 59–64.
Hassan, B. , Ogidiama, O. V. , and Khan, M. N. , 2017, “Energy and Exergy Analyses of a Power Plant With Carbon Dioxide Capture Using Multistage Chemical Looping Combustion,” ASME J. Energy Resour. Technol., 139(3), p. 032002.
Jin, H. G. , and Gao, L. , 2009, “Polygeneration System for Power and Liquid Fuel With Sequential Connection and Partial Conversion Scheme,” ASME Paper No. GT2009-59927.
Jin, H. G. , Gao, L. , Han, W. , and Yan, J. , 2007, “A New Approach Integrating CO2 Capture Into a Coal-Based Polygeneration System of Power and Liquid Fuel,” ASME Paper No. GT2007-27678.
Farmer, R. , 2013, Gas Turbine World 2013 GTW Handbook, Vol. 30, Pequot Publishing, Inc, Fairfield, CT, pp. 66–76.
Gao, L. , 2005, “Investigation of Coal-Based Polygeneration Systems for Production of Power and Liquid Fuel,” Ph.D. thesis, Institute of Engineering Thermophysics, Beijing, China.
Li, S. , 2012, “The Mechanism of Minimal Energy Penalty for CO2 Capture and the Study on Coal-Based Polygeneration System for Cogenerating Substitute Natural Gas and Power,” Ph.D. thesis, Institute of Engineering Thermophysics, Beijing, China.
Bejan, A. , 2006, Advanced Engineering Thermodynamics, Wiley, Hoboken, NJ.
Bakshi, B. R. , Gutowski, T. G. , and Sekulic, D. P. eds., 2011, Thermodynamics and the Destruction of Resources, Cambridge University Press, Cambridge, UK.
Li, S. , Jin, H. , Gao, L. , and Zhang, X. , 2014, “Exergy Analysis and the Energy Saving Mechanism for Coal to Synthetic/Substitute Natural Gas and Power Cogeneration System Without and With CO2 Capture,” Appl. Energy, 130, pp. 552–561.
Fan, S. , Xu, L. , Kang, T. J. , and Kim, H. T. , 2017, “Application of Eggshell as Catalyst for Low Rank Coal Gasification: Experimental and Kinetic Studies,” J. Energy. Inst., 90(5), pp. 696–703.
Ding, L. , Zhou, Z. J. , Huo, W. , and Yu, G. , 2015, “Comparison of Steam-Gasification Characteristics of Coal Char and Petroleum Coke Char in Drop Tube Furnace,” Chin. J. Chem. Eng., 23(7), pp. 1214–1224.
Duan, W. , Yu, Q. B. , Liu, J. X. , Wu, T. W. , Yang, F. , and Qin, Q. , 2016, “Experimental and Kinetic Study of Steam Gasification of Low-Rank Coal in Molten Blast Furnace Slag,” Energy, 111, pp. 859–86.
Duan, W. , Yu, Q. B. , Wu, T. W. , Yang, F. , and Qin, Q. , 2016, “Experimental Study on Steam Gasification of Coal Using Molten Blast Furnace Slag as Heat Carrier for Producing Hydrogen-Enriched Syngas,” Energy Convers. Manage., 117, pp. 513–519.
Srinivas, T. , Reddy, B. V. , and Gupta, A. V. S. S. K. S. , 2012, “Thermal Performance Prediction of a Biomass Based Integrated Gasification Combined Cycle Plant,” ASME J. Energy Resour. Technol., 134(2), p. 021002.
Zhu, Y. H. , Somasundaram, S. , and Kemp, J. W. , 2010, “Energy and Exergy Analysis of Gasifier-Based Coal-to-Fuel Systems,” ASME J. Energy Resour. Technol., 132(2), p. 021008.
Martinez-Patiño, J. , Serra, L. , Verda, V. , Picún-Núñez, M. , and Rubio-Maya, C. , 2016, “Thermodynamic Analysis of Simultaneous Heat and Mass Transfer Systems,” ASME J. Energy Resour. Technol., 138(6), p. 062006.
Ishida, M. , 1982, “Energy and Exergy Analysis of a Chemical Process System With Distributed Parameters Based on the Energy Direction Factor Diagram,” Ind. Eng. Chem. Proc. Des. Dev, 21(4), pp. 690–695.
Ishida, M. , 2002, Thermodynamics Made Comprehensible, Nova Science Publishers, New York.
Wu, H. D. , Li, S. , and Gao, L. , 2017, “Exergy Destruction Mechanism of Coal Gasification by Combining the Kinetic Method and the Energy Utilization Diagram,” ASME J. Energy Resour. Technol., 139(6), p. 062201.
Hofmann, M. , and Tsatsaronis, G. , 2016, “Exergy-Based Study of a Binary Rankine Cycle,” ASME J. Energy Resour. Technol., 138(6), p. 062003.
View article in PDF format.

## References

IEA Coal Industry Advisory Board, 2000, Coal in the Energy Supply of China, International Energy Agency, Paris, France, pp. 1–110.
BP, 2016, “BP Statistical Review of World Energy,” BP Global, London, accessed Apr. 28, 2018,
EIA, 2017, “International Energy Outlook 2017,” United States Energy Information Administration, Washington, DC.
Patel, J. G. , 1980, “The U‐GAS® Process,” Int. J. Energy Res., 4(2), pp. 149–165.
Breault, R. W. , 2010, “Gasification Processes Old and New: A Basic Review of the Major Technologies,” Energies, 3(2), pp. 216–240.
CNMHG, 2012, “Introduction of HT-L Pulverized Coal Gasification Technology and Gasifier,” Changzheng Engineering Co., Ltd., Beijing, China.
Kenji, A. , 2015, “The Situation and Progress of the Osaki COOLGEN Blowing-Oxygen IGCC Project,” Nineth Sino Japanese Energy Saving and Environmental Protection Comprehensive Forum, pp. 5–23.
Kouji, O. , 2014, “Oxygen-Blown Coal Gasification System (<Special Articles> Current and Future Status of Integrated Coal Gasification Combined Cycle System),” J. Jpn. Inst. Energy, 93(7), pp. 624–630.
Xu, S. , Ren, Y. , Wang, B. , Xu, Y. , Chen, L. , Wang, X. , and Xiao, T. , 2014, “Development of a Novel 2-Stage Entrained Flow Coal Dry Powder Gasifier,” Appl. Energy, 113, pp. 318–323.
Ariyoshi, D. , Takeda, S. , Kosuge, K. , Mizuno, M. , and Kato, K. , 2016, “Development of High-Efficiency Coal Gasification Technology,” Clean Coal Technology and Sustainable Development, Springer, Singapore, pp. 617–619.
Matsuoka, K. , Kajiwara, D. , Kuramoto, K. , Sharma, A. , and Suzuki, Y. , 2009, “Factors Affecting a Team Gasification Rate of Low Rank Coal Char in a Pressurized Fluidized Bed,” Fuel Process. Technol., 90(7–8), pp. 895–900.
Brdar, R. D. , and Jones, R. M. , 2000, “GE IGCC Technology and Experience With Advanced Gas Turbines,” GE Power Systems, Schenectady, NY, Paper No. GER-4207.
Maurstad, O. , 2005, “An Overview of Coal Based Integrated Gasification Combined Cycle (IGCC) Technology,” Massachusetts Institute of Technology, Cambridge, MA, Report No. MIT LFEE 2005-002 WP.
Irfan, M. F. , Usman, M. R. , and Kusakabe, K. , 2011, “Coal Gasification in CO2 Atmosphere and Its Kinetics since 1948: A Brief Review,” Energy, 36(1), pp. 12–40.
Lv, P. , Yuan, Z. , Ma, L. , Wu, C. , Chen, Y. , and Zhu, J. , 2007, “Hydrogen-Rich Gas Production From Biomass Air and Oxygen/Steam Gasification in a Downdraft Gasifier,” Renewable Energy, 32(13), pp. 2173–2185.
Wang, R. , Huang, Q. , Lu, P. , Li, W. , Wang, S. , Chi, Y. , and Yan, J. , 2015, “Experimental Study on Air/Steam Gasification of Leather Scraps Using U-Type Catalytic Gasification for Producing Hydrogen-Enriched Syngas,” Int. J. Hydrogen Energy, 40(26), pp. 8322–8329.
Karatas, H. , Olgun, H. , and Akgun, F. , 2013, “Coal and Coal and Calcined Dolomite Gasification Experiments in a Bubbling Fluidized Bed Gasifier Under Air Atmosphere,” Fuel Process. Technol., 106, pp. 666–672.
Koba, K. , and Ida, S. , 1980, “Gasification Reactivities of Metallurgical Cokes With Carbon Dioxide, Steam and Their Mixtures,” Fuel, 59(1), pp. 59–63.
Niu, Y. , Han, F. , Chen, Y. , Lyu, Y. , and Wang, L. , 2016, “Experimental Study on Steam Gasification of Pine Particles for Hydrogen-Rich Gas,” J. Energy. Inst., 90(5), pp. 715–724.
Aranda, G. , Grootjes, A. J. , Van der Meijden, C. M. , Van der Drift, A. , Gupta, D. F. , Sonde, R. R. , Poojari, S. , and Mitra, C. B. , 2016, “Conversion of High-Ash Coal Under Steam and CO2 Gasification Conditions,” Fuel Process. Technol., 141(1), pp. 16–30.
Huo, W. , Zhou, Z. , Wang, F. , and Yu, G. , 2014, “Experimental Study of Pore Diffusion Effect on Char Gasification With CO2 and Steam,” Fuel, 131(1), pp. 59–65.
Jangsawang, W. , Klimanek, A. , and Gupta, A. K. , 2006, “Enhanced Yield of Hydrogen From Wastes Using High Temperature Steam Gasification,” ASME J. Energy Resour. Technol., 128(3), pp. 179–185.
Messenböck, R. C. , Dugwell, D. R. , and Kandiyoti, R. , 1999, “CO2 and Steam-Gasification in a High-Pressure Wire-Mesh Reactor: The Reactivity of Daw Mill Coal and Combustion Reactivity of Its Chars,” Fuel, 78(7), pp. 781–793.
Tola, V. , Cau, G. , Ferrara, F. , and Pettinau, A. , 2016, “CO2 Emissions Reduction From Coal-Fired Power Generation: A Techno-Economic Comparison,” ASME J. Energy Resour. Technol., 138(6), p. 061602.
Halama, S. , and Hartmut, S. , 2016, “Reaction Kinetics of Pressurized Entrained Flow Coal Gasification: Computational Fluid Dynamics Simulation of a 5 MW Siemens Test Gasifier,” ASME J. Energy Resour. Technol., 138(4), p. 042204.
Peng, D. Y. , and Robinson, D. B. , 1976, “A New Two-Constant Equation-of-State,” Ind. Eng. Chem. Fundam., 15(1), pp. 59–64.
Hassan, B. , Ogidiama, O. V. , and Khan, M. N. , 2017, “Energy and Exergy Analyses of a Power Plant With Carbon Dioxide Capture Using Multistage Chemical Looping Combustion,” ASME J. Energy Resour. Technol., 139(3), p. 032002.
Jin, H. G. , and Gao, L. , 2009, “Polygeneration System for Power and Liquid Fuel With Sequential Connection and Partial Conversion Scheme,” ASME Paper No. GT2009-59927.
Jin, H. G. , Gao, L. , Han, W. , and Yan, J. , 2007, “A New Approach Integrating CO2 Capture Into a Coal-Based Polygeneration System of Power and Liquid Fuel,” ASME Paper No. GT2007-27678.
Farmer, R. , 2013, Gas Turbine World 2013 GTW Handbook, Vol. 30, Pequot Publishing, Inc, Fairfield, CT, pp. 66–76.
Gao, L. , 2005, “Investigation of Coal-Based Polygeneration Systems for Production of Power and Liquid Fuel,” Ph.D. thesis, Institute of Engineering Thermophysics, Beijing, China.
Li, S. , 2012, “The Mechanism of Minimal Energy Penalty for CO2 Capture and the Study on Coal-Based Polygeneration System for Cogenerating Substitute Natural Gas and Power,” Ph.D. thesis, Institute of Engineering Thermophysics, Beijing, China.
Bejan, A. , 2006, Advanced Engineering Thermodynamics, Wiley, Hoboken, NJ.
Bakshi, B. R. , Gutowski, T. G. , and Sekulic, D. P. eds., 2011, Thermodynamics and the Destruction of Resources, Cambridge University Press, Cambridge, UK.
Li, S. , Jin, H. , Gao, L. , and Zhang, X. , 2014, “Exergy Analysis and the Energy Saving Mechanism for Coal to Synthetic/Substitute Natural Gas and Power Cogeneration System Without and With CO2 Capture,” Appl. Energy, 130, pp. 552–561.
Fan, S. , Xu, L. , Kang, T. J. , and Kim, H. T. , 2017, “Application of Eggshell as Catalyst for Low Rank Coal Gasification: Experimental and Kinetic Studies,” J. Energy. Inst., 90(5), pp. 696–703.
Ding, L. , Zhou, Z. J. , Huo, W. , and Yu, G. , 2015, “Comparison of Steam-Gasification Characteristics of Coal Char and Petroleum Coke Char in Drop Tube Furnace,” Chin. J. Chem. Eng., 23(7), pp. 1214–1224.
Duan, W. , Yu, Q. B. , Liu, J. X. , Wu, T. W. , Yang, F. , and Qin, Q. , 2016, “Experimental and Kinetic Study of Steam Gasification of Low-Rank Coal in Molten Blast Furnace Slag,” Energy, 111, pp. 859–86.
Duan, W. , Yu, Q. B. , Wu, T. W. , Yang, F. , and Qin, Q. , 2016, “Experimental Study on Steam Gasification of Coal Using Molten Blast Furnace Slag as Heat Carrier for Producing Hydrogen-Enriched Syngas,” Energy Convers. Manage., 117, pp. 513–519.
Srinivas, T. , Reddy, B. V. , and Gupta, A. V. S. S. K. S. , 2012, “Thermal Performance Prediction of a Biomass Based Integrated Gasification Combined Cycle Plant,” ASME J. Energy Resour. Technol., 134(2), p. 021002.
Zhu, Y. H. , Somasundaram, S. , and Kemp, J. W. , 2010, “Energy and Exergy Analysis of Gasifier-Based Coal-to-Fuel Systems,” ASME J. Energy Resour. Technol., 132(2), p. 021008.
Martinez-Patiño, J. , Serra, L. , Verda, V. , Picún-Núñez, M. , and Rubio-Maya, C. , 2016, “Thermodynamic Analysis of Simultaneous Heat and Mass Transfer Systems,” ASME J. Energy Resour. Technol., 138(6), p. 062006.
Ishida, M. , 1982, “Energy and Exergy Analysis of a Chemical Process System With Distributed Parameters Based on the Energy Direction Factor Diagram,” Ind. Eng. Chem. Proc. Des. Dev, 21(4), pp. 690–695.
Ishida, M. , 2002, Thermodynamics Made Comprehensible, Nova Science Publishers, New York.
Wu, H. D. , Li, S. , and Gao, L. , 2017, “Exergy Destruction Mechanism of Coal Gasification by Combining the Kinetic Method and the Energy Utilization Diagram,” ASME J. Energy Resour. Technol., 139(6), p. 062201.
Hofmann, M. , and Tsatsaronis, G. , 2016, “Exergy-Based Study of a Binary Rankine Cycle,” ASME J. Energy Resour. Technol., 138(6), p. 062003.

## Figures

Fig. 3

(a) Simplified flow diagram of novel IGCC system and (b) simplified flow diagram of reference system

Fig. 2

(a) Heat flow diagram of traditional gasification and (b) heat flow diagram of proposed gasification with thermochemical regenerative process

Fig. 1

Development history of the CGE of coal gasification technologies

Fig. 4

Compositions of syngas in GE and novel system

Fig. 8

(a) EUD of gasification process in the reference system and (b) EUD of gasification process in the novel system

Fig. 5

Utilization of syngas sensible heat

Fig. 6

Percentage of heating coal and LHV of syngas

Fig. 7

Power output of GT/ST and thermal performances

## Tables

Table 1 Feedstock composition analysis [28,29]
Table 2 Design conditions
Table 3 Experiment data of coal/coke-steam gasification
Table 4 Thermal balance of gasification systems
Table 7 Exergy balance of the reference and novel IGCC system
Table 5 Exergy balance of the gasification systems
Table 6 Thermal performance of the reference and novel IGCC system

## Discussions

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