Introduction

Coal is used to generate 50% of U.S. electricity and about 40% of the electricity produced globally [1]. For China and India, the fraction of power that is based on coal is about 77% and 74% respectively [2], and it is growing. Because of its history, coal-based power generation in the absence of adequate controls can be a major emitter of air pollutants and thus is perceived as being dirty. CO2 emissions from coal-based power generation have now also become a major concern. This chapter addresses both of these issues but focuses on CO2 emissions and the implications to global climate change.

Total global CO2 emissions from coal-based power generation totaled almost 7.5 billion tonnes in 2007; this is about 30% of the global fossil-related CO2 emissions.

The findings included in this chapter do not necessarily reflect the view or policies of the Environmental Protection Agency. Mention of trade names or commercial products does not constitute Agency endorsement or recommendation for use.

CBE, Iowa State University, Ames, IA 50012, USA e-mail: [email protected]

F.T. Princiotta (ed.), Global Climate Change - The Technology Challenge, 51

Advances in Global Change Research 38, DOI 10.1007/978-90-481-3153-2_2, © Springer Science+Business Media B.V. 2011

Respectively, the U.S. and China emitted an estimated 5.9 and 6.7 billion tonnes of CO2 from fossil fuel combustion and cement production, of which about 1.9 billion tonnes and 2.3 billion tonnes of CO2 were from coal-based power generation in 2007 [3, 4]. Power plants are some of the largest single point source emitters; a typical 1,000 MWe coal-fired power emits over 6 million tonnes of CO2 per year. Examples of the annual CO2 emissions for selected large power plants in several countries are given in Table 2.1 [5, 6].

Coal is a critical fuel for power generation because it is abundant and cheap - $1-$2 per million Btu, compared with $4-$12 per million Btu for natural gas and oil. Coal is also very abundant with estimated proven global reserves of about 900 billion tonnes which is equivalent to about 160 years at current production rates [7]. The three largest coal consumers - China, the U.S., and India - have about half the global reserves of coal and have limited reserves of other fossil fuels. The U.S., with about 250 billon tonnes of recoverable coal reserves, has 27% of the world total [1]. Global primary energy demand is projected to grow by just over 50% by 2030, and world electricity demand is projected to double by 2030. Given this situation, coal-based power could account for a significant portion of this growth, but that is not assured. This will require that growth continues and coal-based technologies improve significantly with respect to their environmental footprint. Figure 2.1 shows the increase

Table 2.1 CO2 emissions from selected large coal-fired power plants

CO2 emissions,

Plant name Country million tonnes/year

Taichung

Poryong

Tuoketuo

Vindhyachal

Hekinan

Janschwalde

Miller

Gibson

WA Parish

Taiwan South Korea China India Japan Germany USA, Alabama USA, Indiana USA, Texas

37.5

34.4

29.5

800-

600-

W 200 o

-475

2000 2010 2020 2030

Fig. 2.1 Projected increase in coal-based power generation capacity by region to 2030 [1]

2000 2010 2020 2030

US&Canada China India Rest of World

Fig. 2.1 Projected increase in coal-based power generation capacity by region to 2030 [1]

in coal generating capacity as projected by the IEA [1]. Internal Chinese projections for growth in coal-based power generation exceed IEA projections, reaching about 1,050 GW in 2030 and about 1,400 GW by 2050 [8]. Actual annual growth rate of coal-based power generation in China exceeded 20%/year from 2000 to 2007, and significant further growth is projected (Fig. 2.1). The criticality of reducing the environmental footprint of and controlling CO2 emissions from coal-based power generation is obvious if these growth projections are to be realized. Further, most of this coal-based generation growth is in developing-world countries, which desperately need additional power generation to support economic growth, increase their standard of living, and reduce poverty.

This chapter focuses on the technologies for generating electricity from coal and on managing related emissions, particularly CO2 emissions. It addresses the cost and performance of power generation from coal, of criteria emissions control, and of CO2 capture and geologic sequestration (CCS) for different generating technologies. It is an update and expansion on a recent article by the author [9] and is based on a number of sources, particularly "The Future of Coal" [10], and recent comprehensive design work by Williams and co-workers at Princeton University, Princeton Environmental Institute [11]. Additional information is available in [12]. The impact of co-firing coal and biomass and of utilizing biomass alone on cost, performance, and CO2 emissions associated with power generation is also considered. These considerations utilize the same cost and operational bases across all technologies, including those in Chap. 3, to make the comparisons as relevant as possible.

The overall approach used here involved picking a point set of design and operating conditions at which to compare technologies. The design bases for the comparisons include:

• Each unit was a Greenfield unit with 500 MWe net generating capacity

• Each technology was designed to control criteria emissions to somewhat below today's best-demonstrated commercial performance.

• Costs were based on 2000-2006 detailed cost designs for the U.S. Gulf Coast; indexed to the mid-2007 construction cost environment as indicated by the Chemical Engineering Plant Cost Index. As indicated in Fig. 2.2, construction costs escalated rapidly from 2000, after a period of stability; mid-2007 CEPCI was a compromise level. Such rapid escalations as indicated by the HIS-CERA Index are likely not sustainable and could see self-correction when economic conditions change.

• Commercially demonstrated technologies were integrated, and cost estimates are for the Nth plant, where N is of order five to seven, for those technologies that are still evolving. This is meant to allow the learning's from the first couple of plants constructed to be engineered into future cycles of plants.

• Performance and costs are based on a single set of conditions for each technology and on the EPRI-recommended approach to calculate levelized cost of electricity (COE). Key economic and operating parameters are given in Table 2.2, and the properties of the feedstocks used, Illinois # 6, high-sulfur coal, and switch grass are given in Table 2.3.

180 170 160 150

X 110

130 120 110 100

2000 2001 2002 2003 2004 2005 2006 2007 2008

Year

Fig. 2.2 Recent increases in construction cost as represented by several construction cost indices. Indices normalized to 100 in 2000 (Courtesy EPRI [13])

Table 2.2 Key economic and operating parameters used in developing cost comparisons [11]

Base year for capital costs, Gulf Coast

Mid-2007

Capital change rate, % of TPI per year

14.40

Interest during construction (3 year), % of TPC

7.16

O&M, % of TPC per year

4.00

Capacity factor of coal plans

85%

Table 2.3 Key parameters of feedstocks used in

process analysis

[11, 12]

Coal, Illinois #6, Herrin

Coal price, $/GJ (HHV, as received)

1.71

Coal price, $/tonne, AR

46.4

HHV, MJ/kg (AR)

27.1

Wt% Carbon (AR)

63.7

Wt% Sulfur (AR)

2.51

Wt% Ash (AR)

9.7

Wt% Moisture (AR)

11.1

Biomass, Switchgrass

Biomass price, $/GJ (HHV)

5

HHV, MJ/kg (AR)

15.9

Wt% Carbon (AR)

40

Wt% Sulfur (AR)

0.08

Wt% Ash (AR)

5.3

Wt% Moisture (AR)

15

2000 2001 2002 2003 2004 2005 2006 2007 2008

Year

This provides an indicative cost comparison from technology to technology. Obviously, coal type, plant site and location, dispatch strategy, and a myriad of design and operating parameter decisions will affect cost and operation but are not explored here [10]. The same comments apply to the estimates of Chap. 3 and will not be repeated there. In both chapters, production costs are presented by category so that the impact of capital cost, feedstock cost, etc., can be evaluated. The important issue is comparison among technologies, including without CO2 capture and with CO2 capture and geologic storage. Technology and costs for CO2 transport and geologic storage are generation-technology independent, and costs are based on the CO2 quantity stored.

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