Processing Cost Analysis for Biomass Feedstocks

Badger, P. C.

Oak Ridge National Laboratory

关键词: Wood Wastes;    Biomass;    Fluidized Beds;    Processing;    Gasification;   

DOI  :  10.2172/814666
RP-ID  :  ORNL/TM-2002/199
RP-ID  :  AC05-00OR22725
RP-ID  :  814666

美国|英语

来源: UNT Digital Library

【 摘 要 】

The receiving, handling, storing, and processing of woody biomass feedstocks is an overlooked component of biopower systems. The purpose of this study was twofold: (1) to identify and characterize all the receiving, handling, storing, and processing steps required to make woody biomass feedstocks suitable for use in direct combustion and gasification applications, including small modular biopower (SMB) systems, and (2) to estimate the capital and operating costs at each step. Since biopower applications can be varied, a number of conversion systems and feedstocks required evaluation. In addition to limiting this study to woody biomass feedstocks, the boundaries of this study were from the power plant gate to the feedstock entry point into the conversion device. Although some power plants are sited at a source of wood waste fuel, it was assumed for this study that all wood waste would be brought to the power plant site. This study was also confined to the following three feedstocks (1) forest residues, (2) industrial mill residues, and (3) urban wood residues. Additionally, the study was confined to grate, suspension, and fluidized bed direct combustion systems; gasification systems; and SMB conversion systems. Since scale can play an important role in types of equipment, operational requirements, and capital and operational costs, this study examined these factors for the following direct combustion and gasification system size ranges: 50, 20, 5, and 1 MWe. The scope of the study also included: Specific operational issues associated with specific feedstocks (e.g., bark and problems with bridging); Opportunities for reducing handling, storage, and processing costs; How environmental restrictions can affect handling and processing costs (e.g., noise, commingling of treated wood or non-wood materials, emissions, and runoff); and Feedstock quality issues and/or requirements (e.g., moisture, particle size, presence of non-wood materials). The study found that over the years the industry has shown a good deal of ingenuity and, as a result, has developed several cost effective methods of processing and handling wood. SMB systems usually cannot afford to perform much onsite processing and therefore usually purchase fuels processed to specification. Owners of larger systems try to minimize onsite processing to minimize processing costs. Whole truck dumpers are expensive, but allow for faster and easier unloading, which reduces labor costs and charges by the haulers. Storage costs are a major factor in overall costs, thus the amount of fuel reserve is an important consideration. Silos and bins are relatively expensive compared to open piles used for larger facilities, but may be required depending on space available, wood characteristics, and amount of wood to be stored. For larger systems, a front-end loader has a lot of flexibility in use and is an essential piece of equipment for moving material. Few opportunities appear to exist for improving the cost effectiveness of these systems.