Amit Kumar, Jay B. Cameron, and Peter C. Flynn[2]

Department oaMechanical Enginee2ing,
Unive2bity oaAlberta, Edmonton,
Alberta, T6G 2G8, Canada,
E-mail: peter. alynn@ualberta. ca

Abstract

The cost of transporting wood chips by truck and by pipeline as a water slurry was determined. In a practical application of field delivery by truck of biomass to a pipeline inlet, the pipeline will only be economical at large capacity (>0.5 million dry t/yr for a one-way pipeline, and >1.25 million dry t/yr for a two-way pipeline that returns the carrier fluid to the pipeline inlet), and at medium to long distances (>75 km [one-way] and >470 km [two-way] at a capacity of 2 million dry t/yr). Mixed hardwood and softwood chips in western Canada rise in moisture level from about 50% to 67% when trans­ported in water; the loss in lower heating value (LHV) would preclude the use of water slurry pipelines for direct combustion applications. The same chips, when transported in a heavy gas oil, take up as much as 50% oil by weight and result in a fuel that is >30% oil on mass basis and is about two — thirds oil on a thermal basis. Uptake of water by straw during slurry trans­port is so extreme that it has effectively no LHV. Pipeline-delivered biomass could be used in processes that do not produce contained water as a vapor, such as supercritical water gasification.

Index Entries: Wood chips; pipeline; biomass; lower heating value; straw.

Introduction

Carbon-based power generation facilities do not typically rely on delivery of fuel by highway truck. Oil — and gas-fired plants rely on pipe­lines, and coal-based facilities typically either are located at the mine mouth or rely on rail or ship for fuel delivery. The reason for this is the high cost and high congestion that would be associated with delivery of large ton­nages of fuel to modern, large power plants.

Numerous biomass power plants are small and utilize truck delivery of fuel. However, in a previous work (1), we noted that optimum size for straw — and wood-based biomass power plants in a western Canadian set-

ting were 450 MW or greater for straw and wood from harvesting the whole forest, and that cost of power increased sharply at sizes below about 200 MW. For forest harvest residues (limbs and tops), which are more widely dispersed, the optimum size was 137 MW.

A 450-MW biomass power plant burning 2.1 million dry t/yr of wood chips would require 17 truck deliveries per hour at 20 t/truck (2). High­way transportation of fuel is a significant cost element, contributing at optimum power plant size 25, 14, and 38% of the total cost of power gen­eration from direct combustion of straw, wood from harvesting the whole forest, and forest harvest residues, respectively (1). In the present work, we evaluated pipeline delivery of biomass to a power generation plant, to avoid road congestion (and likely resistance by nearby residents), and to reduce overall fuel transportation cost.

Two carrier mediums are considered for biomass: water and oil. We review the inherent economics of truck vs pipeline transport, and then evaluate a case of field delivery of biomass by short-haul truck to a pipe­line terminal. We also evaluate the impact of water and oil absorption by the biomass fuel. Finally, we discuss the prospects for pipeline transport of biomass.

In this article, all costs are reported in year 2000 US dollars; Canadian dollars are converted to US at an exchange rate of 1.52 Cdn$/US$.