Performance and Cost Discussion

The output from the EPRI BIOPOWER model are used for the 1997 base case in Table 2. Heat and material balance data are detailed in Figure 4. The principal departure from the DeLong case is that DeLong uses heat from th e combined cycle for alfalfa processing and the alfalfa arrives at the plant with a moisture content of roughly 15% du e to in-field drying. The current case assumes that this same amount of heat is instead utilized for wood drying. The heat available is sufficient to reduce wood of approximately 24% moisture to the feed moisture content of 10%. Each additional 10% of feed moisture (i.e. 34% instead of 24%) carries a performance penalty of roughly 1.5 basis points . The feed moisture utilized will result in an average efficiency; proper management of herbaceous crops and some wood wastes can yield lower delivered feed moisture, while some wood feedstocks can be appreciably higher. The stea m cycle conditions in BIOPOWER are also somewhat more moderate than those employed in the DeLong study.

Plant availability is based on data in the EPRI TAG [6]. These data are derived from a number of plants currently i n operation. For coal gasification combined cycle plants that utilize essentially the same power island technology , availability is 85.7%. For biomass based wood-fired stoker plants (direct combustion steam boiler), the availabilit y is listed as 85%. The equipment in the power island characteristically has availability in excess of 89% in base loa d operations. Biomass gasification is, in many ways including the severity of process conditions, much simpler than coal gasification. Therefore, it seems that an 85% availability estimate for the entire biomass power plant i s

Fuel Gas

Cooler

HPStecm 70,909 Mc^h

HP Steam @ 5.86/468 MPa/C 235,013 Mqfh

Dolomite 1.7R6Ma/t^

Ash & Char 5,240 MgiFr

Steam to LBG

7,943 Mg/h

Dried Feed ' 1,167 Mgfcl

Fuel Gas

Cooler

HPStecm 70,909 Mc^h

HP Steam @ 5.86/468 MPa/C 235,013 Mqfh

Dolomite 1.7R6Ma/t^

Ash & Char 5,240 MgiFr

Steam to LBG

7,943 Mg/h

Dried Feed ' 1,167 Mgfcl

Moisture Loss 38.5 Mgfcl
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Solar Power

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