Resources and economic analyses of underground coal gasification in India

Resources and economic analyses of underground coal gasification in India

JFUE 8619 No. of Pages 8, Model 5G 8 November 2014 Fuel xxx (2014) xxx–xxx 1 Contents lists available at ScienceDirect Fuel journal homepage: www...

1MB Sizes 0 Downloads 270 Views

JFUE 8619

No. of Pages 8, Model 5G

8 November 2014 Fuel xxx (2014) xxx–xxx 1

Contents lists available at ScienceDirect

Fuel journal homepage: www.elsevier.com/locate/fuel 5 6

Resources and economic analyses of underground coal gasification in India

3 4 7

Q1

8

Anil Nivrutti Khadse ⇑ Department of Petroleum Engineering, Maharashtra Institute of Technology, Paud Road, Kothrud, Pune 411 038, India

9 10

h i g h l i g h t s

1 2 13 14

 The potential UCG coal resources in India are 120.666 billion tonnes.

15

 The potential UCG lignite resources in India are 20.980 billion tonnes.

16 17

 The UCG plant is analyzed by considering vertical wells UCG module.

18

 Capital cost and operating costs are estimated for 100 MW UCG power plant.

 An equilibrium model and an economic model are combined for UCG plant analysis.

19

a r t i c l e 2 5 1 3 22 23 24 25 26 27 28 29 30 31 32 33 34

i n f o

Article history: Received 27 November 2013 Received in revised form 15 October 2014 Accepted 21 October 2014 Available online xxxx

Q2

Keywords: Underground coal gasification Equilibrium model Economics India Coal Lignite

a b s t r a c t India has 298.914 billion tonnes of coal resources and 43.215 billion tonnes of lignite resources. Underground Coal Gasification (UCG) can be used to extract the deep and un-minable coal and lignite resources in India. Total 120.666 billion tonnes coal resource and 20.98 billion tonnes lignite resource are confined to the depth greater than 300 m which would be the potential resources for UCG. A simple approach has been developed for economic evaluation of UCG project. The UCG module can be considered to consist of two vertical wells. An equilibrium model based on elemental composition of coal is used to predict the gas quality and yield. Based on a single UCG module dimensions, syngas production and power generation per module are calculated. The capital and operating costs are estimated for 100 MW UCG power plant with the multiple UCG modules. Three Indian coal samples- one sub-bituminous coal (C) and two lignites (A and B) are used to estimate the capital and operating costs of 100 MW UCG power plant. The capital costs are in the range of $210–246 millions. The estimated costs of clean syngas production per GJ are $1.34, $0.90 and $1.73 for sample A, B and C respectively. The estimated electricity generation costs per MWh using UCG syngas are $24.27, $19.10 and $28.11 for sample A, B and C respectively. Ó 2014 Elsevier Ltd. All rights reserved.

36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51

52 53

1. Introduction

54

Energy is the prime driving force for the economic growth of the country. The Expert Committee on Integrated Energy Policy in its Report (IEPR 2006) has estimated that by 2032, primary commercial energy requirement in India would need to go up by 4–5 times, electricity generation installed capacity by 6–7 times and oil requirement by 3–6 times the current level [1]. To meet the estimated energy demand, an efficient and clean use of the available coal and lignite resources is required. The Underground Coal Gasification (UCG) offers a clean source of energy by converting coal/ lignite in-situ into syngas that can be used either as a fuel or as a chemical feedstock [2]. The UCG has the potential to utilize coal

55 56 57 58 59 60 61 62 63 64

⇑ Tel.: +91 20 30273400; fax: +91 20 25442770. E-mail address: [email protected]

and lignite resources which are inaccessible due to depth and are uneconomical to extract using the conventional mining methods [3]. The Former Soviet Union (FSU) was the first to begin largescale UCG pilot testing and commercial program in1930s. One of the UCG plant in Angren is operating for the last 50 years. The USA conducted 33 UCG trials in 1970s. After FSU and USA, UCG trials have been conducted in South Africa, China, Australia, Canada, New Zealand, Pakistan, and Europe during 1980–2010 [4]. In India, Oil and Natural Gas Corporation Ltd. (ONGC) has been planning for a UCG trial. The previous feasibility study shows that Indian coals which are at the greater depths are suitable for the UCG [2]. Many UCG projects are in the planning phase while a few are in the pilot phase. During planning phase of the UCG project, a quick estimation of gas produced in the UCG process is necessary for the project viability, using preliminary economic analysis. Several theoretical UCG models have developed for the prediction of UCG

http://dx.doi.org/10.1016/j.fuel.2014.10.057 0016-2361/Ó 2014 Elsevier Ltd. All rights reserved.

Please cite this article in press as: Khadse AN. Resources and economic analyses of underground coal gasification in India. Fuel (2014), http://dx.doi.org/ 10.1016/j.fuel.2014.10.057

65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80

JFUE 8619

No. of Pages 8, Model 5G

8 November 2014 2 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106

A.N. Khadse / Fuel xxx (2014) xxx–xxx

process performance in terms of gas composition and gas heating value [5–11]. The UCG models have also developed for prediction of UCG cavity growth during the gasification process [3,12–14]. The UCG models have developed based on two approaches, namely, free channel model and packed bed model [8]. These models involve various assumptions to simplify the complex UCG process. After simplification, the model calculations are time intensive and needs detailed information on coal properties, heat and mass transfer rates and kinetic parameters. In the absence of the detailed information, the thermodynamic equilibrium model is the best option for the prediction of gas composition and heating value since it requires only coal composition, reactant ratios, pressure and temperature [15]. The inputs required for the equilibrium model are elemental composition of coal, amount of coal and air and/or steam, temperature and pressure. In the analysis of UCG project viability, available coal/lignite resource, gas composition, gas yield per tonne, gas heating value and coal consumption rate are the important parameters. In this paper, resource analysis of coal and lignite in India is carried out based on the coal seam depth. For preliminary economic evaluation of UCG project, use of the equilibrium model combined with the simple economic model is proposed. Costs of syngas production and electricity generation are estimated based on capital and working costs available in the literature. Three different Indian coal samples - one sub-bituminous coal (C) and two lignites (A and B) are considered in these analyses.

107

2. Coal and lignite resources in India

108

2.1. Coal resources

109 110 111 112 113 114 115 116 117 118 119 120 121 122 123

Total geological resources of coal in India are 298.914 billion tonnes. The depth-wise distribution of the total resources indicate that the Indian coalfields (excluding Jharia) hold 175.609 billion tonnes up to 300 m depth from surface and 86.974 billion tonnes between 300 m and 600 m depth levels (Table 1) [16]. Jharia coalfield, in addition, contains 14.212 billion tonnes up to 600 m depth. The total coal resources between 600 m and 1200 m depth levels stand at 22.118 billion tonnes. State-wise distribution of Indian coal shows that Jharkhand is at first place in the list with 80.701 billion tonnes followed successively by Orissa (73.710 billion tonnes), Chhattisgarh (52.169 billion tonnes), West Bengal (31.283 billion tonnes), Madhya Pradesh (25.061 billion tonnes), Andhra Pradesh (22.206 billion tonnes) and Maharashtra (10.964 billion tonnes) [17]. These seven states contribute to 99.06% of total coal resource of India.

124

2.2. Lignite resources

125

The total geological resources of lignite in India stand at 43.215 billion tonnes. Of these, 6.180 billion tonnes are classified as ‘Proved’, 26.282 billion tonnes are classified as ‘Indicated’ and 10.752 billion tonnes are classified as ‘Inferred’ resources [18].

126 127 128

Considering the available depth-wise distribution of total lignite resources (Table 2), 5.705 billion tonnes of resources of Tamilnadu lignite fields occur within 150 m depth. Bulk of the lignite resources of Rajasthan (1.899 billion tonnes), Gujarat (0.707 billion tonnes) and Pondicherry (0.416 billion tonnes) are found to occur within 150 m depths. Thus, a total of 8.768 billion tonnes (20% of the total) of country’s lignite resources are confined within 150 m depth from the surface. Further 13.461 billion tonnes (31% of total) of the lignite resources occur between 150–300 m and 20.986 billion tonnes (49% of total) below 300 m depth. In addition to these, about 60 billion tonnes of lignite may likely to be contained within 800–1400 m depth in Kalol basin (Mehsana area), Gujarat.

129

3. Possible UCG reserves and resources in India

142

3.1. Coal

143

In India, total 120.666 billion tonnes coal is at a depth greater than 300 m in which proven coal reserves are 27.647 billion tonnes. Table 3 gives available total coal (resources) and proven coal (reserves) in the seven states of India at a depth range 300– 1200 m. If coal at a depth greater than 300 m is considered suitable for UCG, these are potential candidate for UCG extraction.

144

3.2. Lignite

150

The depth wise lignite distribution shows 49% lignite occurs at a depth greater than 300 m. If the same depth criterion is applied for lignite as that of coal (i.e. lignite at a depth greater than 300 m is suitable for the UCG), then about 20.986 billion tonnes lignite is available for UCG extraction in the two states of India (Table 3). About 60 billion tonnes of lignite may likely to be contained within 800–1400 m depth in Kalol basin (Mehsana area), Gujarat which would be the potential UCG resource in the future once the technology is proven at the shallow depths. The suitability of these vast coal and lignite resources may be studied by following approach. The technical process parameters such as gas composition, gas heating value and gas yield per tonne of coal are predicted using the thermodynamic equilibrium model. The inputs to the model are available information on depth, thickness and elemental composition of coal. The technical process parameters from the equilibrium model are combined with the simple economic model (economic model does not consider the time value of money, taxes and rate of return) gives the costs of clean syngas production and electricity generation based on the capital and working costs.

151

4. UCG module design

171

The design of UCG module is an important task since it affects project viability. In the simplest form, UCG module consists of

172

Table 2 Depth wise lignite resource in major lignite rich states [18]. State

Table 1 Depth wise coal resource of India (billion tonnes) (01.04.2013) [16]. Depth 0–300 0–600a 300–600 600–1200 Total a

Proved

Indicated

Inferred

Total

% Total

95.092 13.760 12.045 2.283

69.936 0.451 58.544 13.699

10.580 0 16.384 6.135

175.609 14.212 86.974 22.118

58.75 4.75 29.10 7.40

123.181

142.631

33.100

298.914

100.0

Only for Jharia coalfield for which break-up is not available.

Geological resources of lignite (billion tonnes) 0–150 m

1 2 3 4 5 6 7

Tamilnadu Rajasthan Gujarat Pondicherry Kerala J&K West Bengal Total

5.705 1.899 0.707 0.416 0.027 0.009 0.001 8768.14

150–300 m

>300 m

Total

8.433 3.012 2.014 0 0

20.208 0.777 0 0 0

0.001

0

34.347 5.689 2.722 0.416 0.027 0.009 0.002

13.461

20.986

43.215

Please cite this article in press as: Khadse AN. Resources and economic analyses of underground coal gasification in India. Fuel (2014), http://dx.doi.org/ 10.1016/j.fuel.2014.10.057

130 131 132 133 134 135 136 137 138 139 140 141

145 146 147 148 149

152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170

173

JFUE 8619

No. of Pages 8, Model 5G

8 November 2014 3

A.N. Khadse / Fuel xxx (2014) xxx–xxx Table 3 Coal and lignite resources at depth between 300 and 1200 m in major coal rich states. State

Geological resources of coal (billion tonnes) Proved

Coal 1 2 3 4 5 6 7

Jharkhand Odisha Chhattisgarh West Bengal Andhra Pradesh Madhya Pradesh Maharashtra Total

Lignite 1 Tamilnadu 2 Rajasthan Total

174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204

17.354 1.332 1.019 3.102 1.136 3.506 0.196 27.647

Total 37.126 26.546 13.596 18.070 9.333 12.552 3.440 120.666

considered in the equilibrium model and by-products formed in the actual process like light hydrocarbons, NH3 and H2S are neglected. Coal is assumed as CHxOy where x and y are dependent on the individual coals and can be determined from ultimate analysis. Coal is reacted with air and steam to give the products CO2, CO, H2, CH4 and H2O. The set of competitive reactions considered are – oxidation, steam gasification, methanation, boudouard and water gas shift reaction. Of these only an independent set of reactions is considered in the calculations. The general coal gasification reaction with air and steam is written as

205 206 207 208 209 210 211 212 213 214 215

216

mCHx Oy þ zðpO2 þ ð1  pÞN2 Þ þ kH2 O

20.208 0.777

¼ aCO2 þ bCO þ cH2 þ dCH4 þ eN2 þ f H2 O þ gC

20.986

one vertical injection well and one vertical production well as shown in Fig. 1. The UCG module design is the distance between injection and production wells, thickness of the coal seam and injection rate. The coal resources in the UCG module are calculated based on the area of module and thickness of the coal. In conventional room and pillar mining, coal recovery is typically 60% because some coal must be left in place to provide support for the overburden. The coal utilization estimated for the Hanna I experiment was reported to be 63% [19]. Coal conversion is assumed 60% similar to conventional room and pillar mining. Total coal resources in UCG module and coal conversion efficiency are used to get coal available for the gasification. Coal available for gasification and coal consumption rate will give an operational life of the UCG module. Equilibrium model is used for the predication of gas composition, gas heating value and gas yield per tonne of coal. Based on the gas heating values and efficiency of power plant, the number of the modules required for the power generation is calculated. The width and length of UCG module is assumed to be 50 m and the coal thickness required is 10 m. The spacing between the injection and the production well is 50 m. With the 60% coal conversion efficiency the coal gasified will be 20,445 tonnes. The life of the module is calculated using coal consumption rate. For example, the life of the module will be 259 days with coal consumption rate 78.75 tonnes per day, as in the case of Hanna-II Phase-III forward burn pilot stage [19]. Hanna-II Phase-III forward burn pilot stage results are used to validate the thermodynamic model since information is available in open literature and the test was run for considerable time with fair amount of coal consumption rate. The development of equilibrium model for UCG is described in details by Khadse [15]. The important gas components are

ð1Þ

218

where x and y are the H/C and O/C mole ratio, respectively. The moisture content of the coal is neglected and the product quality depends on x and y. m moles of coal, z moles of air, k moles of steam and a, b, c, d, e, f and g are moles of CO2, CO, H2, CH4, N2 and H2O and unreacted carbon respectively. Taking atom balances on carbon, oxygen, hydrogen and nitrogen, we obtain,

219 220 221 222 223 224 225

Carbon

m¼aþbþdþg

ð2Þ

226 228

Oxygen

m y þ 2pz þ k ¼ 2a þ b þ f

ð3Þ

229 231

m x þ 2k ¼ 2c þ 4d þ 2f

ð4Þ

232 234

ð5Þ

235 237

Hydrogen Nitrogen

zð1  pÞ ¼ e

The equilibrium relations for the three reactions (other than oxidation) are (1) Boudouard reaction

238 239 240

241

K e1 ¼

y2co Pt yco2

ð6Þ

(2) Steam gasification reaction

K e2

yco yH2 P t ¼ yH2 O

245 244 246

ð7Þ

(3) Methanation reaction

K e3

yCH ¼ 2 4 yH2 Pt

248 250 249 251

ð8Þ

The equilibrium constants are given by

DG0 ln K e ¼  RT

243

253 254

255

ð9Þ

Fig. 1. Vertical well UCG module [2].

Please cite this article in press as: Khadse AN. Resources and economic analyses of underground coal gasification in India. Fuel (2014), http://dx.doi.org/ 10.1016/j.fuel.2014.10.057

257

JFUE 8619

No. of Pages 8, Model 5G

8 November 2014 4

A.N. Khadse / Fuel xxx (2014) xxx–xxx

Table 4 Coal analyses [20,21].

Table 7 Analyses of three coal samples [15].

Fixed carbon Volatile matter Ash Moisture C H O N S

Hanna-II,III

WIDCo coal for LBK tests

34.1 32.6 23.7 9.5 74.3 6.0 16.6 1.9 1.0

35.5 28.5 14.4 21.6 76 4.7 18.7 0.1 0.4

Moisture Volatile matter Fixed carbon Ash C H N O S GCV (MJ/kg)

Table 5 Input parameters for the model [11].

Sample A (Lignite)

Sample B (Lignite)

Sample C (sub-bituminous coal)

5.01 27.39 51.25 16.01 64.72 3.72 1.10 8.47 – 19.22

13.42 45.51 23.15 17.89 50.84 5.38 0.33 18.33 0.83 16.57

9.53 20.23 66.17 4.05 75.47 1.89 0.02 6.80 – 20.96

Table 8 Gas compositions predicted for samples using equilibrium model.

Parameter

Hanna-II–III

LBK-1

LBK-4

LBK-5

Injection flow rate (mol/s) Injection molar compositions O2 H2O N2 Ratio H2O/O2 Injection temperature (K) Pressure (kPa) Duration (day) Coal consumed (tonnes)

73.4

9.4

5.4

2.6

0.21 0 0.71 0 400 779 39.34 3098

0.25 0.75 0 3 400 125 2.84 26.4

0.5 0.5 0 1 400 125 2.45 17.3

0.21 0 0.71 0 400 125 0.82 1.2

Coal

Hanna-II Phase III

Sample A

Sample B

Sample C

H2 CO CH4 CO2 N2 H2O

18.79 16.27 2.44 9.76 52.74 7.59

14.69 15.58 1.52 9.12 59.09 5.90

19.46 16.47 2.61 9.97 51.49 7.91

9.85 16.78 0.7 10.75 61.62 4.40

Table 6 Dry gas composition from model prediction and pilot test.

a b

Pilot Test

Hanna-IIPhase-III

LBK-I

Gas composition (%)

Pilota Modelb Pilota Modelb Pilota Modelb Pilota Modelb

CO2 CO H2 CH4

14.17 9.63 13.32 16.13 14.13 17.78 3.73 2.2

27.1 11 24.1 43.2 40.9 43.58 3.9 2.11

LBK-4

LBK-5

28.2 13.91 21.5 48.34 43.1 36.28 5 1.47

13.3 4.82 11.2 27.68 15.6 13.61 1.9 0.22

The actual gas composition from UCG pilot trial. The gas composition predicted using equilibrium model.

GCV (kJ/kg)

250 200 150 100 50

Field Trial Model

Q4

258 259 260 261 262

15 10 5 0

CO

CO2

H2

Hanna Model

16.27

9.76

18.79

CH4 2.44

Sample A

15.58

9.12

14.69

1.52

Sample B

16.47

9.97

19.46

2.61

Sample C

16.78

10.75

9.85

0.7

Fig. 3. Dry gas composition comparison for different coals.

300

0

Gas composition (%)

20

LBK1

LBK4

LBK5

Hanna-II-III

230

242

99

118

265.9

253.76

119.25

121.5

Fig. 2. Comparison of heating value from model prediction and pilot test.

where DG0 is the Gibb’s free energy (kJ/mol), T is the temperature in (K) and R is the universal gas constant in consistent units. The set of non-linear equation is solved for the gas compositions. The model is simulated in MATALB software using FSOLVE function which is used for the solution of a system of non-linear

equations. Hanna-II Phase-III forwards pilot burn phase which utilized sub-bituminous coal with air input and the LBK test with WIDCo sub-bituminous coal with air, steam and oxygen inlet are used to validate the model predictions. Coal properties and inputs are used in the equilibrium model are tabulated in Tables 4 and 5 respectively [20,21]. The Hanna UCG trials were conducted in US during 1973–1977 using air as the gasification agent. The operation duration of the Hanna-II Phase-III forward pilot burn phase is 39.34 days [20]. The Lawrence Livermore National Laboratory (LLNL) had conducted a series of experiments known as the large block experiments near Centralia, Washington at the Washington Irrigation and Development Company (WIDCO) coal mine in Centralia, WA in 1982. Five experiments (LBK-1, LBK-2, LBK-3, LBK-4 and LBK-5) were run with differences in steam/oxygen injection ratio as well as total flow rate changes and air injection. The LBK field experiments were operated for a short duration i.e. less than 3 days and used to study effect of inlet gas ratio on the gas composition [21]. The model predictions are compared with Hanna-I Phase-III forward pilot burn phase, LBK-1, LBK-4 and LBK-5 field pilot results in Table 6. The predicted gas compositions are comparable with the UCG pilot results considering the simplicity of the

Please cite this article in press as: Khadse AN. Resources and economic analyses of underground coal gasification in India. Fuel (2014), http://dx.doi.org/ 10.1016/j.fuel.2014.10.057

263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283

JFUE 8619

No. of Pages 8, Model 5G

8 November 2014 A.N. Khadse / Fuel xxx (2014) xxx–xxx

5

Fig. 4. General layout of UCG power plant (modified from [22]).

298

model. Model over predicts CO and under predicts CO2 in all the tests. The gas heating value is compared in Fig. 2. The predicted heat of combustion of the product gas is 4.97 MJ/m3 while the average heat of combustion of gas obtained in the Hanna-II, Phase-III test was 4.83 MJ/m3. The predicted heats of combustion of the product gas in case of LBK-1, LBK-4 and LBK-5 field pilot are 10.88, 10.38 and 4.88 MJ/m3 respectively. The corresponding field values for heat of combustion of the product gas are 9.41, 9.90 and 4.05 MJ/m3 for LBK-1, LBK-4 and LBK-5 field pilot respectively. The error in heating value prediction ranges from 3% to 20%. The error is the maximum (20%) in case of LBK-5 field pilot while it is the minimum (3%) in case Hanna-II Phase-III. Since design of power plant is based on heat of combustion, the model can be applied in the economic evaluations of power generation using the UCG.

299

4.1. Prediction of gas composition and heating value for Indian coals

300

Three different Indian coal samples – one sub-bituminous coal (C) and two lignites (A and B) are considered in these analyses. The analyses of three Indian coal samples are tabulated in Table 7 [15]. The ultimate analysis of these coal samples and operating parameters from Hanna-II-Phase III pilot are used to obtain gas composition, gas heating value and gas yield per tonne of coal. Table 8 gives the gas composition of the three coal samples A, Sample B and Sample C along with Hanna-II Phase-III. Fig. 3 shows the comparison of the dry gas composition for different coals. It shows that each coal has different gas composition based on its elemental composition. The gas heating value and gas yield change with the coal properties.

284 285 286 287 288 289 290 291 292 293 294 295 296 297

301 302 303 304 305 306 307 308 309 310 311

312

5. UCG layout design

313

The general layout of UCG and power plant is shown in Fig. 4 [22]. It consists of UCG modules, gas cleaning and power block. The plant is designed to generate 100 MW power. The efficiency of gas- based power plant is assumed 45% [23]. One module of Hanna-II–III produces 0.24 million cubic meters per day of syngas with heating value of 4.97 MJ/m3. The syngas from one module will generate 6.18 MW of power. Hence, to generate 100 MW, 16 UCG

314 315 316 317 318 319

modules are required. The life time of the module is 259 days, the required number of modules per year is 22. For start up, 16 modules will be ignited simultaneously to generate 100 MW power. The injection wells will be connected to injection pipeline which is connected to air compressor. All the production wells will be connected to production pipeline which will collect the gas and send to gas cleaning section. The cleaned gas will be used for power generation. If an area having width and length equal to 500 m each with 10 m thickness of coal is selected, then coal reserves would be 3.40 million tonnes with coal density 1363 kg/m3. In the UCG field, the UCG modules are made one after another keeping appropriate distance between the two modules. The optimization of the modules design can be possible. In the area of 500 m  500 m, 81 modules can be designed having dimensions 50 m  50 m keeping 2.5 m distance on both the sides. Fig. 5 shows the schematic of UCG Module layout in 500 m  500m area. This area will support coal for the 100 MW power generation for 5.06 years (see Fig. 6). Q3 Similar calculation made for three Indian coal samples (Table 7) and results are tabulated in Table 9. In this analysis, elemental analysis of the coal is the only variable which results in difference in gas composition, heating value and power generation capacity. Sample B which is lignite gives high heating value gas 5.14 GJ/m3 and power generation 6.56 MW per module among the three samples. Sample C gives the lowest heating value 3.35 GJ/m3 and 3.43 MW power generation per module. This may be co-related with oxygen and hydrogen content of these coal samples. Sample A contains 18.33% oxygen and 5.38% hydrogen while sample C contains 6.80% oxygen and 1.89% hydrogen. Fig. 5 shows the effect of hydrogen and oxygen content on gas heating value and power generation.

320

6. Economics analysis

351

6.1. Capital cost

352

The depth of the coal seam is assumed at 300 m and cost of injection and production wells are estimated based on the available information. The cost of drilling well is $630/m [24]. The capital cost of gas cleaning equipment for 54,503 m3/h

353

Please cite this article in press as: Khadse AN. Resources and economic analyses of underground coal gasification in India. Fuel (2014), http://dx.doi.org/ 10.1016/j.fuel.2014.10.057

321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350

354 355 356

JFUE 8619

No. of Pages 8, Model 5G

8 November 2014 6

A.N. Khadse / Fuel xxx (2014) xxx–xxx

Gas gathering and cleaning facility

P M-73

M-74

M-75

M-76

M-77

M-78

M-79

M-80

M-81

I M-64

M-65

M-66

M-67

M-68

M-69

M-70

M-71

M-72

P M-55

M-56

M-57

M-58

M-59

M-60

M-61

M-62

M-63

I M-46

M-48

M-47

M-49

M-50

M-51

M-52

M-53

M-54

500m

P M-37

M-38

M-39

M-40

M-41

M-42

M-43

M-44

M-45

I M-28

M-29

M-30

M-31

M-32

M-33

M-34

M-35

M-36

P M-19

M-20

M-21

M-22

M-23

M-24

M-25

M-26

M-27

I M-10

M-11

M-12

M-14

M-14

M-15

M-16

M-17

M-18

P M-3 50

M-1

M-2

M-3

M-4

M-5

M-6

M-7

M*8

M-9

50 I 500m Injection facility M= UCG Module I=Injection P=Production

Fig. 5. Schematic of UCG modules layout in 500 m  500 m area. 357 358 359 360

capacity is given in Table 10. In addition, the capital cost for gas turbine and HRSG is $29,890,000 for 21 MW power plant [25]. The capital cost is estimated using 0.6 factor method (Eq. (10)) for the each case in this study.

361 363 364 365 366 367

Cost ¼ Base Cost 



0:6

Capacity Base capacity

ð10Þ

The capital costs are converted in 2012 dollar using Chemical Engineering Plant Cost Index (CEPCI) which was 444.2 in 2004 and 584.6 in 2012 [26,27]. The results are tabulated in Table 11. The capital cost is in the range of $210–246 million.

6.2. Operating cost

368

The operating cost for UCG is taken as drilling cost required per year with 10% contingency. Operating cost for the total plant is taken as 4.5% of the total capital cost [23]. The results are shown in Table 10. The capital cost is in the range $210–246 million. In this analysis, depreciation, cost escalation royalty and other costs are not included for simplicity. The cost of gas production is in the range of 0.90–1.73 $/GJ and electricity generation is in the range of $19.10–28.18/MWh. It is observed that with same operating conditions and coal reserves, the gas quality, quantity and cost of gas production is different for different coals.

369

Please cite this article in press as: Khadse AN. Resources and economic analyses of underground coal gasification in India. Fuel (2014), http://dx.doi.org/ 10.1016/j.fuel.2014.10.057

370 371 372 373 374 375 376 377 378

JFUE 8619

No. of Pages 8, Model 5G

8 November 2014 7

A.N. Khadse / Fuel xxx (2014) xxx–xxx

Table 12 The costs of syngas production and electricity generation from Powder River Basin and Indiana studies [23,27]. Cost

UCG-Air

UCG-O2

UCG-O2-Steam

UCG operating (million $) Production cost ($/GJ) Electricity ($/MWh)

58.34(UCG) +179.1(PPa) 13.47 1.53 12

69.59 (UCG) 23.29 2.41 NA

108.61 (UCG) 30.92 3.26 NA

Indiana study for 250 MW plant Annual drilling Total annual O&M for UCG Production cost ($/GJ) Electricity ($/MWh)

60.8 68.8 7.65 86.30

28.4 36.9 4.54 64.30

– – – –

PRB study 200 MW plant Capital (million $)

a

PP = Power plant.

Fig. 6. Effect of hydrogen and oxygen content on gas heating value and power generation. Table 13 Comparison of estimated costs of syngas production and electricity generation with PRB and Indiana study [23,27].

Table 9 Process parameters. Coal Gas heating value (MJ/m3) Gas yield (m3/ton) MW power per module Number of modules for 100 MW Life of 500 m  500 m block (year)

Hanna-II Phase III

Sample A

Sample B

Sample C

4.97 3192 6.18 16

4.07 2798 4.44 23

5.14 3281 6.56 15

3.35 2628 3.43 29

5.06

3.52

5.40

2.79

Table 10 The capital cost of major equipment [25]. Equipment

Cost ($)

Air compressor Dust removal Gas Cooling Gas cleaning Sour water stripper Acid gas removal and Sulfur recovery Offsite and auxiliaries Buildings

4,321,000 2,629,000 2,373,000 2,812,000 2,979,000 10,800,000 14,583,000 2,913,000 3

Note: The costs are the plant of capacity 54,503 m /h and are reported in 2004 year.

Indiana study PRB study Hanna-II–III Sample A Sample B Sample C

Syngas ($/GJ)

Electricity ($/MWh)

7.65 1.53 0.96 1.34 0.90 1.73

86 12 19.64 24.27 19.10 28.11

The cost estimates of syngas production and electricity generation from Powder River Basin (PRB) sub-bituminous coal are given in Table 12 [23]. The average coal thickness and depth of PRB subbituminous coal are 34 m and 320 m respectively. Coal has the moisture content of 27.66% and ash content of 6.44%. In the PRB study, 65% module coal recovery, 81% gasification thermal efficiency and 45% turbine efficiency are considered. The cost of syngas production with air is $1.53/GJ and electricity generation using syngas produced using air is $12/MWh. The cost estimates in Indiana study [28] for syngas production with air and oxygen are $7.65/GJ and $4.54/GJ respectively (Table 12). The cost of electricity generation using syngas produced using air and oxygen is $86/MWh and $64.3/MWh respectively. The costs are sensitive to coal seam thickness and depth, UCG module design and reactant used in the gasification. Low rank

Table 11 Capital and operating cost estimates for 100 MW UCG power plant. Capital cost ($)

Hanna-II–III

Sample A

Sample B

Sample C

Drilling Air compressor Dust removal Gas cooling Gas cleaning Sour water stripper Acid gas removal & sulfur recovery Gas turbine and HRSG Offsite and auxiliaries Buildings Total

6,048,000 10,382,631 6,317,042 5,701,917 6,756,760 7,158,033 25,950,571 100,340,115 35,040,480 6,999,446 210,694,994

8,694,000 12,163,646 7,400,654 6,680,012 7,915,800 8,385,906 30,402,076 100,340,115 41,051,248 8,200,116 231,233,572

5,670,000 10,355,703 6,300,658 5,687,129 6,739,236 7,139,468 25,883,267 100,340,115 34,949,600 6,981,292 210,046,468

10,962,000 13,462,448 8,190,876 7,393,286 8,761,028 9,281,331 33,648,331 100,340,115 45,434,594 9,075,703 246,549,713

Operating cost ($) Drilling per year 10% UCG cost 4.6% of total plant Total

6,048,000 604,800 9,691,970 16,344,770

8,694,000 869,400 10,636,744 20,200,144

5,670,000 567,000 9,662,138 15,899,138

10,962,000 1,096,200 11,341,287 23,399,487

Unit cost of production Syngas ($/GJ) Electricity ($/MWh)

0.96 19.64

1.34 24.27

0.90 19.10

1.73 28.11

Please cite this article in press as: Khadse AN. Resources and economic analyses of underground coal gasification in India. Fuel (2014), http://dx.doi.org/ 10.1016/j.fuel.2014.10.057

379 380 381 382 383 384 385 386 387 388 389 390 391 392 393

JFUE 8619

No. of Pages 8, Model 5G

8 November 2014 8

A.N. Khadse / Fuel xxx (2014) xxx–xxx

409

bituminous coal having the moisture content of 5–7.5% and ash content of 7.5–12.5% is considered in the Indiana study. The coal thickness is 2–3.5 m and the coal depth is greater than 200 m. Coal to gas efficiency is assumed in the range of 45–50% and turbine efficiency is 70–80%. The estimated costs in this study are compared with the costs estimates from PRB and Indiana study in Table 13. Syngas production costs are found to be within a range, except for Indiana study in which coal seam thickness is 2.5 m. Similar to syngas cost, electricity generation costs in this study are found to be within range except for Indiana study. These costs are calculated with simplified assumptions and costs parameters available in the literature. These are the preliminary cost estimates and a detailed economic analysis will require reliable cost parameters from vendor/in-house company cost estimates.

410

7. Summary

411

443

Total geological resources of coal and lignite in India are 298.91 billion tonnes and 43.21 billion tonnes respectively. Total 120.66 billion tonnes coal resources and 20.98 billion tonnes lignite resources are confined to the depth greater than 300 m from the surface. These coal and lignite resources may be considered as the potential candidates for the UCG. The simple approach for preliminary economic evaluation of UCG project is developed in this study. The equilibrium model combined with simple economics analysis predicts the reasonable cost of syngas production and electricity generation. The equilibrium model predicts gas heating values of 4.07, 5.14 and 3.35 MJ/m3 for sample A, B and C respectively. The capital cost is in the range $210–246 million. In this analysis, depreciation, cost escalation royalty and other costs are not considered for simplicity. The preliminary economic analysis shows that the estimated costs of syngas production per GJ are $1.34, $0.90 and $1.73 for sample A, B and C respectively. The estimated electricity generation costs per MWh using UCG syngas are $24.27, $19.10 and $28.18 for sample A, B and C respectively. The variation in the syngas quality, quantity and cost of syngas production is observed based on coal properties considering all other parameters constant. Sample B which is lignite gives high heating value gas 5.14 GJ/m3 and power generation 6.56 MW per module among three samples. Sample C gives the lowest heating value 3.35 GJ/m3 and 3.43 MW power per module. This may be correlated with the oxygen and hydrogen content of these coal samples. Sample A contains 18.33% oxygen and 5.38% hydrogen while sample C contains 6.80% oxygen and 1.89% hydrogen. The parameters used in this approach are easily available in geological reports of the coal blocks. This approach may useful at screening stage. For realistic UCG project evaluation, dynamic UCG model with a detailed economics analysis need to be developed which require a detailed technical data from a pilot plant and cost estimates from the vendors.

444

References

394 395 396 397 398 399 400 401 402 403 404 405 406 407 408

412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442

445 446 447

[2] Khadse A, Qayyumi M, Mahajani S, Aghalayam P. Underground coal gasification: a new clean coal utilization technique for India. Energy 2007;32:2061–71. [3] Daggupati S, Mandapati R, Mahajani S, Ganesh A, Sapru R, Sharma R, et al. Laboratory studies on cavity growth and product gas composition in the context of underground coal gasification. Energy 2010. [4] Self S, Reddy B, Rosen M. Review of underground coal gasification technologies and carbon capture. Int J Energy Environ Eng 2012;3:16. [5] Thorsness CB, Greens EA, Sherwood A. A one dimensional model for in situ coal gasification. Lawrence Livermore National Laboratory Report, UCRL 52523, 1978. [6] Thorsness CB, Charles B. General-purpose, packed-bed model for analysis of underground coal gasification processes. Lawrence Livermore National Laboratory Report, Ucid-20731, 1985. [7] Thorsness CB, Kang SW. Further development of a general-purpose, packedbed model for analysis of underground coal gasification processes. Lawrence Livermore National Laboratory Report, Ucrl-92489, 1986. [8] Yang L, Liu S. Simulation on heat and mass transfer in the process of underground coal gasification. Numerical Heat Transfer Part A 2003;44:537–57. [9] Yang L. Study on the model experiment and numerical simulation for underground coal gasification. Fuel 2004;83:573–84. [10] Khadse A, Qayyumi M, Mahajani S, Aghalayam P. Reactor model for underground coal gasification channel. Int J Chem Reactor Eng 2006;4:A37. [11] Perkins G, Sahajwalla V. Steady-state model for estimating gas production from underground coal gasification. Energy Fuels 2008;22:3902–14. [12] Park K, Edgar T. Modeling of early cavity growth for underground coal gasification. Ind Eng Chem Res 1987;26:237–46. [13] Perkins G, Sahajwalla V. A mathematical model for the chemical reaction of a semi-infinite block of coal in underground coal gasification. Energy Fuels 2005;19:1679–92. [14] Prabu V, Jayanti S. Simulation of cavity formation in underground coal gasification using bore hole combustion experiments. Energy 2011;36– 10:5854–64. [15] Khadse A. Underground coal gasification: kinetics and process modeling. Ph.D. Thesis IIT Bombay, 2008. [16] Geological Survey of India. [last visited on 01.08.13]. [17] CMPDI. [last visited on 01.08.13]. [18] Geological Survey of India. [last visited on 01.08.13]. [19] US EPA. In-situ coal gasification: status of technology and environmental impact. EPA-600/7-77-045, May 1977. [20] Cena RJ, Thorsness CB. Lawrence liver more national laboratory underground coal gasification data base. Lawrence Livermore National Laboratory Report, UCID 19169, 1981. [21] Hills RW, Thorsness CB. Summary Report on large block experiments in underground coal gasification, Tono Basin, Washington. Experimental description and data analysis. Lawrence Livermore National Laboratory Report, UCRL 53305, vol. 1, 1982. [22] Zorya AYu, Kreynin EV, Sushentsova, BYu. What is necessary for transformation of a UCG enterprise into high efficient, stable and economically effective industrial production?. 4th UCGP conference, London, 2009. [23] Gas Tech. Viability of underground coal gasification in the ‘‘Deep Coals’’ of the Powder River Basin, Wyoming. ; 2007 [last accessed on 20.10.10]. [24] Oil and Gas Journal News. Essar West Bengal CBM drilling approved. ; 2011 [last accessed on 15.09.14]. [25] NETL. Gasification plant cost and performance optimization task 3 final report. DOE Contract No. DE-AC26-99FT40342, May 2005. [26] Economic Indicators. Chemical engineering plant cost index (CEPCI). Chemical Engineering, January 2008. [27] Economic Indicators. Chemical engineering plant cost index (CEPCI). Chemical Engineering, March 2014. [28] Indiana University study. Viability of underground coal gasification with carbon capture and storage in Indiana. ; 2011 [last accessed on 25.10.13].

448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519

[1] Kumar A, Kumar K, Kaushik N, Sharma S, Mishra S. Renewable energy in India: current status and future potentials. Renew Sustain Energy Rev 2010;14:2434–42.

Please cite this article in press as: Khadse AN. Resources and economic analyses of underground coal gasification in India. Fuel (2014), http://dx.doi.org/ 10.1016/j.fuel.2014.10.057