|Year : 2014 | Volume
| Issue : 2 | Page : 127-134
Coal as an Energy Source for Mitigating Energy Crisis in Pakistan
Muhammad Imran Rashid1, Sajid Naseem2, Naveed Ramzan3
1 Department of Chemical, Polymer and Composite Material Engineering, Center for Energy Research and Development, Lahore, KSK Campus, Pakistan; Department of Chemical Engineering, Priority Research Center for Energy, The University of Newcastle, New South Wales, 2308 Australia
2 Department of Polymer and Process Engineering, University of Engineering and Technology, Lahore, KSK Campus, Pakistan
3 Department of Chemical Engineering, University of Engineering and Technology, Lahore, KSK Campus, Pakistan
|Date of Web Publication||19-Sep-2014|
Muhammad Imran Rashid
Department of Chemical, Polymer and Composite Material Engineering, Center for Energy Research and Development, Lahore, KSK Campus, Pakistan; Department of Chemical Engineering, Priority Research Center for Energy, The University of Newcastle, New South Wales, 2308 Australia
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Pakistan is producing just 0.1% of its electricity from its coal resources. Electricity supply and demand gap in Pakistan is projected to increase rapidly till 2020. Pakistan has major reserves of lignite coal and similar coal has been used for electricity production in Greece, Turkey, Poland, and Germany. Natural gas and oil resources are also becoming meager in Pakistan, which stresses the use of coal gasification techniques for efficient energy generation. Underground coal gasification and fluidized bed combustion are appropriate choices for Pakistani low-grade Thar coal. Relatively high grade Makerwal and Lakhara coals can be gasified by integrated gasification combined cycle technology. Pakistan's abundant indigenous coal reserves can be used to produce fertilizer or different viable gaseous mixtures (producer gas, town gas, water gas, and synthetic natural gas). Syngas produced from coal can be used as an alternate of natural gas to run Pakistan fertilizer plants. Use of coal will also result in production of various chemicals for fertilizer (ammonia), textile (dyes, BTX, phenol, ethylene, and acetic acid) and transport (methanol, diesel, gasoline, liquefied petroleum gas) sectors. Retrofitting of existing oil fired plants, installation of new gasification plants and improving the efficiency of existing coal based power plants has become inevitable for future survival of Pakistan's economy.
Keywords: Coal, coal gasification, energy crisis, energy resources of Pakistan, gasification, integrated coal gasification, power generation, underground coal
|How to cite this article:|
Rashid MI, Naseem S, Ramzan N. Coal as an Energy Source for Mitigating Energy Crisis in Pakistan
. J Eng Technol 2014;4:127-34
| 1. Introduction|| |
Economic growth of any country depends on its electricity production and progress of a nation can be measured in terms of per capita consumption of electrical energy. The per capita energy use in Pakistan in 2011 was very low, 482 kg of oil equivalent compared to 2639 kg of oil equivalent for Malaysia and 2029 kg of oil equivalent for China  . Pakistan is facing huge crisis regarding electricity and natural gas. Only 60% people in Pakistan have access to electricity and they still face rotating blackouts  . Industrial, commercial and household sectors are affected severely from load shedding and especially fertilizer plants and textile industries keep on shutting down throughout the year. Most industrial sector cannot use petroleum oil as their input source for power because they have installed gas turbines which run on natural gas. Pakistan's 42 million ton reserves of crude oil and 853 billion cubic meter reserves of natural gas are much less than its coal reserves which are over 185.5 billion tones  . Significant depletion of natural gas reserves have occurred from 2008 to 2011  . Some hydroelectricity projects could not start due to political snag  . Pakistan has total coal reserves of >185.5 billion tones which can produce 100,000 MW of electricity  . These coal reserves can be utilized for electricity generation or to produce synthetic natural gas (SNG) which can be used to run gas turbines or for household applications or to produce liquid fuels  . [Figure 1] indicates that currently coal provide 10% share in overall energy mix which was just 6.5% in 2005 , .
Pakistan is producing just 0.1% of its electric power from all coal sources. This percentage is very low as compared to other countries. A comparison is shown in [Figure 2]  .
|Figure 2: Electricity production of different countries from all coal sources (2011-2012)|
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Pakistan's dependence on imported electricity and fuel can be reduced by using its coal reserves for power generation. Coal gasification techniques can efficiently produce energy from coal and simultaneously reduce greenhouse gas emissions by carbon capture. Low-grade and inaccessible coal can be utilized by recently developed gasification technologies such as underground coal gasification (UCG) which can commercially produce syngas for applications in power sector, as a fuel, and for chemicals production  .
| 2. Future Electricity Requirements in Pakistan|| |
Total installed electricity generation in the Pakistan was 22477 MW with 94385 GWh of gross generation on June 30, 2011. Thermal, hydal and nuclear are main sources of electricity generation in the country , . With passage of time, expected electricity demand will increase much more rapidly than expected available generation as shown in [Figure 3]. Gap between electricity supply and demand will be maximum in 2020  . On the other side, the electricity production from all coal sources in Pakistan from 1998 to 2011 has fallen drastically which is shown in [Figure 4].
|Figure 3: Projected electricity demand and supply of Pakistan (2008-2020)|
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Natural gas was one of the major sources of electricity generation in Pakistan in 2011 as shown in [Figure 5]. However, natural gas is also facing shortage in Pakistan in recent years which can be observed by negative growth rates in cement (−60), transport (−16.2), fertilizer (−12.1), power (−3.7), and industrial (0.0) sectors as indicated in [Table 1]  .
Pakistan should take prompt measures to cover electricity supply and demand gap and utilization of abundant indigenous coal reserves is inevitable at this stage.
| 3. Coal Reserves in Pakistan and Their Quality|| |
The Thar lignite deposits discovered in Pakistan in 1990's are spread over an area of 9000 km 2 and are 175,506 million tones as shown in [Figure 6]  . Poland, Germany and other countries has profitably used lignite coal for power generation. This coal calorific value was even lower than Pakistani Thar coal. Turkey has also successfully used their lignite coal reserves for electric power generation and lignite production is increasing with passage of time  . Lignite coal supply 78.4% of electricity requirements in Greece  .
Turkish lignite coals have average moisture of 40%  . Pakistani coals except Thar coal have moisture content below 25% as shown in [Figure 7]. These coals are even better than Turkish lignite coal and should be used for power generation.
| 4. Pakistan's Low-Rank/Low-Grade Coal Utilization|| |
Pakistan' low grade can efficiently be used by coal gasification. Gasification is a process by which coal can be converted into combustible gases. The gas usually consists of carbon monoxide, hydrogen and methane. Gasification processes can be divided into entrained bed, molten salt, fixed bed and underground gasification and fluidized bed processes  .
4.1 Fluidized bed combustion
Pakistani coals have high moisture content. High moisture fuels can be burnt by fluidized bed combustion technique. Studies have shown that low grade and high ash coal drawbacks can be rectified by gasifying it in fluidized beds  . Low-grade coal (peat or lignite), coal-mining wastes (culm, wood chips, solid biomass) and shredded tires can be burned in suitably designed fluidized-bed combustors. Less pre-treatment of coal is required for circulating fluidized bed (CFB) boilers. CFB boilers not only use high ash coal (50-60% ash) but are also suitable for multiple fuels (peat, wood waste, bark, oil)  . Hence, co-firing option can also be used with Pakistani coals. Control of NO x and SO 2 is much better in CFB boilers. NO x are controlled by using primary and secondary air while limestone is used to capture SO 2 . Almost 90% sulfur emissions can be captured using limestone sorbent.
4.2 Underground coal gasification
Pakistan lignite deposits have low-energy content and can be utilized by using UCG, thus eliminating the need for mining. If proper geological sites are selected for UCG, it will be very appropriate option for Thar coal. Combustion of deep coal seam results in high-Methane formations and resulting gas has more calorific value. UCG is a preferred choice for coal seams of over 150 m depth. Thar coal reserves are found at minimum depths of 150 m  and seem quite feasible for UCG. If coal has less calorific value (<12 MJ/kg) and high-volatile matter (>8%), then UCG is most suitable technology  . Pakistani coals have volatile matter greater than 20% [Figure 7] and are best candidates for UCG. In UCG process, two wells are drilled, among them one is used to inject oxygen/air and steam, while other is used to collect the recovered gases as shown in [Figure 8]. Electric coils or gas firing is used to ignite the coal seam and reaction is controlled by adjusting the oxidant flow to the underground gasifier.
Underground coal gasification not only use low-grade coal, but will also result in less greenhouse gas emissions as compared to conventional coal power plants.
| 5. Pakistan's High Rank/High Grade Coal Utilization|| |
Pakistan's relatively high-grade Makerwal and Lakhara coals can be utilized by an integrated gasification combined cycle (IGCC) plant which is represented schematically in [Figure 9].
|Figure 9: Schematic of integrated gasification combined cycle for power production|
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Pakistan's already installed coal-based electric plants efficiency can be improved in a number of ways which are listed in [Table 2]  .
Efficiency of IGCC plants can also be improved by Multistage Enthalpy Extraction Technology (MEET) and low-temperature coal gasification. MEET systems lowers the discharge rate of (liquid, solid, gaseous) wastes as compared to conventional coal power generation systems. It also improves the efficiency of process and provides better gas emission control systems  . In the MEET process refuse derived fuel (RFD) is used as an extra source along with other fuel sources. This fuel is fired and gasified at 1200°C temperature and the ratio is usually 20/80 (RDF/fossil fuel)  . MEET system can use multiple fuel (low-grade coal, corrugated boards, lumber, rubber, textile, sewage sludge, rubber materials) sources. In MEET system the efficiency is increased up to 45-50% using RFD  . Low-temperature gasification well below 1000°C is efficient and this process also provides less loss in chemical energy (LCE) smaller than 10%  . Hayashi proposed fixed bed gasifier separated from a pyrolyzer and these types of gasifiers make LCE <4%  . These techniques are quite suitable for Pakistani lignite and bituminous coals.
| 6. Coal As an Alternate of Natural Gas|| |
In 2012, power sector was a major consumer of natural gas (27.8%), followed by industrial sector (23%), domestic (20.3%), fertilizer (16.4%), compressed natural gas (9.2%), and others (3.30%). Negative growth rates in cement (−60), transport (−16.2), fertilizer (−12.1), power (−3.7) and industrial (0.0) sectors as indicated in [Table 1] show natural gas shortages. Hence, natural gas should be replaced with SNG. Coal can be gasified to produce different gaseous mixtures (producer gas, water gas, town gas, and SNG) which are very viable for industrial and domestic applications. Their composition is enlisted in [Table 3]  . Fixed bed Lurgi dry bottom gasifier is very suitable for producing syngas from lignite and this process is being used in Great Plains plants (North Dakota) and Sasol plants (South Africa)  . Pakistan should also use these processes to produce syngas from its lignite coal reserves. Fluidized bed gasifiers can also be employed to produce syngas rich with hydrogen from low-rank coals  .
Recently developed processes such as Bluegas™ process, fluid-bed methanation method and hydro-gasification process can produce SNG very economically  . Methane produced from these processes is of high-quality (CH4 >99%)  .
| 7. Uses of Coal|| |
Coal can be used to produce town gas, SNG, producer gas, water gas, medium BTU gas, low-BTU gas, fuel gas, ammonia gas, synthetic oils, coke, BTX mixtures, ethane, methanol, and electricity. Different methods by which coal can be converted into energy are given by King et al. [Figure 1]  .
7.1. Fertilizer production
Pakistan's low-rank coal can be utilized for fertilizer production. Organic, organomineral fertilizers and soil conditioners can be produced using the low-rank coal ,, . Makerwal coal remained in use for fertilizer production in Pakistan in 1950s. Iskandarabad fertilizer plant was established based on coal when natural gas was not available. Hydrogen was produced from coal gasification and nitrogen taken from atmosphere to produce ammonia gas. Currently many fertilizer plants in Pakistan are affected by natural gas shortages and their retrofitting on liquid fuels (methanol) is too costly. Pakistan should establish coal gasification plants to produce fertilizer using coal.
7.2. Town gas production
Coal can be used to produce the town gas which has wide range of applications in domestic, industrial and commercial sectors. It can be employed for heating, lighting and or substituting Liquefied petroleum gas (LPG) gas. If LPG is replaced with town gas, then LPG availability will increase for SNG production by mixing it with air.
7.3 Chemicals production
Coal can be used to produce wide variety of chemicals, important for industrial, power, textile and transport sectors. Chemicals which can be produced from coal are listed in [Table 4] ,, .
| 8. Coal Emissions Effect on Health and Environment|| |
Coal use also cause SO x , NO x , particulate matter (fly ash, bottom ash), greenhouse gases (N 2 O, CO 2 ), Organic compounds (polycyclic aromatic hydrocarbons) and trace elements (Sb, As, Be, Cd, Cr, Co, Ni, Hg, Pb, V, Mn) emissions. Health and environmental effects of these emissions are provided in [Table 5]. Electrostatic precipitators, bag house filters, flue gas desulphurization units and scrubbers using SO 2 sorbents can reduce these emissions. Low NO x burners and co-firing with biomass are also suitable options for emissions reduction. As indicated in [Figure 10] Green house gas emissions from coal are less in Pakistan than green house gas emissions from natural gas and oil, so due to its abundance and less emissions, coal is more preferable choice.
|Figure 10: Million tones CO2 emissions from coal, oil and natural gas (1980-2010)|
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| 9. Conclusion|| |
Electricity supply and demand gap in Pakistan is projected to increase to 27500 MW till 2020. Electricity generation from all coal sources has fallen from 0.8% in 1998 to 0.1% in 2011. Pakistan has major reserves of lignite coal and similar coal has been used for electricity production in Greece, Turkey Poland and Germany. Pakistan is merely producing 0.1% of its electricity from coal sources. Natural gas shortage and resources depletion has also increased the electricity crisis and caused permanent shut down of many industrial plants. All Pakistani coals except Thar have low-moisture content (<25%) and should be gasified for electric power or SNG production which can replace natural gas. UCG and fluidized bed combustion are appropriate choices for Pakistani low-grade Thar coal. Relatively high-grade Makerwal and Lakhara coals can be gasified by IGCC technology. Efficiency of IGCC plants can also be improved by MEET and low-temperature coal gasification. Efficiency of installed coal-based power plants can be increased by better combustion control, flue gases heat recovery, drying of low-rank coal and steam turbine design improvements. Coal can be used for production of fertilizer or different viable gaseous mixtures (producer gas, town gas, water gas and SNG). Syngas produced from coal can be used as an alternate of natural gas to run Pakistan's fertilizer plants. Use of coal will also result in production of various chemicals for fertilizer (ammonia), textile (dyes, BTX, phenol, ethylene, acetic acid) and transport (methanol, diesel, gasoline, LPG, fuel oil, motor oil, hydrogen) sectors.
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| Authors|| |
Prof. Dr. Naveed Ramzan is working as a Professor in Chemical Engineering Department, University of Engineering and Technology, Lahore Pakistan. He is Campus coordinator of Faisalabad campus (University of Engineering and Technology, Lahore) and is also chairman of the department of Chemical Engineering. He has published more than 90 research papers in various national and international journals. http://www.uet.edu.pk/faculties/facultiesinfo/facultyinfo?fac_id=27
Mr. M. Imran Rashid is working as Lecturer in Department of Chemical Engineering University of Engineering and Technology, KSK campus, Pakistan. He has four year working experience of a fertilizer plant and teaching experience of various universities. He has completed his M.Sc in 2011. He has published 5 research papers and two books. Currently, he is involved in teaching M.Sc Energy Engineering classes.
Mr. Sajid Naseem is working as Faculty in Department of Polymer and Process Engineering, University of Engineering and Technology, Lahore Pakistan. He has completed his M.Sc in Polymer Engineering in 2014. He has published 2 research papers in international journals.
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]