Authors: Jorgenson, RR; Lee, C; Nelson, R

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Jorgenson, RR, Lee, C & Nelson, R 2006, 'The Benefits of Paste for Coal Combustion Products (CCPs): A Case Study', in R Jewell, S Lawson & P Newman (eds), Paste 2006: Proceedings of the Ninth International Seminar on Paste and Thickened Tailings, Australian Centre for Geomechanics, Perth, pp. 191-207,

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In 2002, 24 percent of the world’s electricity was derived from coal-fired generation. According to the Energy Information Administration, the use of coal to provide for world-wide electrical needs will continue on a historical pattern of growth through 2025 (Figure 1). World-wide, the process of burning coal to produce electricity results in the generation of about 245 million tonnes of coal combustion products (CCPs) annually (EIA, 2005). Figure 1 World-wide coal-fired generation capacity by region (EIA, 2005) Coal combustion products generally consist of fine-grained materials such as flue gas desulphurization (FGD) sludge (scrubber sludge), gypsum (used to produce wallboard), bottom ash (coarse sand-like material), and fly ash (similar to cement). Historically, CCPs have been marketed for beneficial use or disposed adjacent to the generation facility, typically either by hauling as a semi-wet material or by sluicing to an impoundment as a low-density slurry. While considerable effort is being devoted world-wide to increasing the beneficial reuse of CCPs through new applications and increasing reuse volumes, large- volume disposal of CCPs continues to be and will remain an operational reality requiring operators to evaluate more cost-effective, environmentally appropriate designs that more efficiently use valuable natural resources. Gigawatts Emerging economies Transitional economies Mature market economies Paste2006–R.J.Jewell,S.Lawson,P.Newman(eds) ©2006AustralianCentreforGeomechanics,Perth,ISBN0-9756756-5-6 Paste2006,Limerick,Ireland 191 Since large-volume disposal has been, and will continue to be, an inevitable part of operating a coal-fired power plant, the industry would benefit by working to make disposal practices more efficient and cost- effective. Additionally, environmental stewardship and industry excellence provide additional motivation to improve CCP disposal methods. Even so, relatively little has changed with respect to CCP management strategies and the disposal practices implemented at coal-fired power plants in the past several decades. An innovative and cost-effective CCP disposal facility design involving fly ash paste/high-density slurry has been implemented at Great River Energy’s (GRE) Coal Creek Station (CCS), located in the United States near Underwood, North Dakota. The design goals are to transport and place unsold CCPs at the lowest possible cost and to provide for long-term stability in an environmentally appropriate design. The fly ash paste/high-density slurry design application, new to the energy generation industry in the United States, presents some distinct advantages over traditional CCP disposal methods in terms of operational costs and predicted environmental performance. Disposal costs are reduced by hydraulically conveying fly ash as a paste or high-density slurry via pipeline to the final deposition locations, thus avoiding the industry’s standard practice of multiple mechanical handling. Environmental performance is enhanced by reducing the average hydraulic head on the disposal facility’s liner system, thereby minimizing potential leakage into the subsurface. Although GRE’s system can handle paste, there are few economic or environmental advantages realized by operating the system with paste. As such, GRE prefers to operate the system with high-density slurry. However, for the purposes of this paper, the terms “paste” and “high-density slurry” are used interchangeably. This paper presents a case study of the evaluation of potential CCP management options at Great River Energy’s Coal Creek Station, summarizes the characteristics of GRE’s chosen containment design, describes the design and operation of a 90.7-tonne-per-hour fly ash paste/high-density slurry plant for surface disposal application, and presents challenges faced during paste plant design and operation. This paper does not provide a detailed discussion of material rheology, paste plant design constraints, paste plant electrical design, paste plant program logic control (PLC), paste pipeline design criteria and structural analysis, or operational issues associated with depositional practices.

American Coal Ash Association (ACAA) (2005) 2004 Coal Combustion Product Production and Use Survey, September 9, 2005,
Energy Information Administration (EIA) (2005) International Energy Outlook 2005, Report No. DOE/EIA-0484(2005), Release
Date: July 2005, Accessed: October 7, 2005, .
High Plains Regional Climate Center (HPRCC) (2005) Period of record general climate summary (temperature) for Underwood,
North Dakota (Station No. 328872), Accessed: October 10, 2005,
Paste2006,Limerick,Ireland 207
surfAce disPosAl

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