Abstract

We report on the progress of an ongoing project to investigate the performance and operating characteristics of a spark-ignition engine operating on fuel gas derived from the gasification of dairy-farm wastes. A small, 5-hp, Tecumseh engine has been modified to operate on low-BTU fuel gas. It is being thoroughly tested under a variety of input-fuel conditions that are representative of the fuel gas from an advanced manure-fueled gasifier. The test data gathered will be used to decide how best to integrate the engine with the gasifier in order to maximize the overall system conversion (manure-to-horsepower) efficiency.

Dairy farmers are faced with increasingly higher energy costs and tighter environmental regulations regarding the disposal of excess animal wastes. A feasibility study was recently completed to investigate using gasification technology to convert the dairy wastes into clean fuel gas for energy production [1]. The particular gasification system, using high-temperature, preheated air as the gasification medium, was found to operate very efficiently on manure feedstock, much more efficiently than conventional gasifiers. A compact, ceramic regenerative heater supplies the high- temperature air to the gasifier. The gasification system is compact enough that it could be transported to the farm for manure waste processing. The product gas is a suitable fuel for driving microturbines for electrical power generation or for use for other energy needs, thus helping to reduce the operating cost of the farm. Using information collected from an Upstate New York dairy farm, the study of Reference 1 also showed that applying the advanced gasification technology to process the wastes from this particular farm would produce enough syngas whose energy content is more than two times the farm's annual energy requirement. The present study is to assess the feasibility of using some of the surplus gasifier fuel gas for running farm-equipment engines.

In the first phase of our study, the operating characteristics of the SI engine are investigated using simulated fuel gas. The fuel is formulated from bottled gases. The composition and heating value of the syngas produced by the manure-fired gasifier will be a function of the initial manure property (moisture content, ultimate analysis, ash composition, etc.) and the gasifier operating condition (air preheat temperature, gasification temperature, etc.). In our engine tests, we can vary the composition of the simulated fuel gas to account for the influences of these gasifier parameters might have on the product gas properties, and in turn study the effect of these gasifier parameters might have on the performance of the downstream engine. Stable engine-operating regions, as a function of the engine parameters and fuel combustion characteristics of the fuel, are determined experimentally. The results show the sensitivity of the engine efficiency as a function of upstream gasifier's operating temperature, air-preheat temperature, and manure moisture. The test data gathered would help us decide how best to integrate the engine with the gasifier in order to maximize the overall system efficiency. An integrated, manure-fueled, gasifier-engine power train will be tested in a later phase of our project.

References

1. Pian, C.C.P. and Young, L., "Air-Blown Gasification of Dairy-Farm Wastes for Energy

Production," Bioenergy 2002, Boise, ID, September 2002.