Assessment of the technical and economic feasibility of coal sludge slurries

Conference · Thu Jul 01 04:00:00 EDT 1999

OSTI ID:20082299

Dooher, J

Over the past two decades, there has been considerable progress made in the technical developments relating to the utilization of coal in the form of a coal water slurry (CWS) both as a gasifier feedstock and as a furnace fuel. A very promising approach to utilizing CWS in an economical and cost effective manner is to use its basic technical advantage over coal, i.e. its behavior as a fluid as a method of introducing other ordinary unusable fuel sources such as sewage sludge or other solid Btu containing wastes. This can provide an economic advantage to CWS via waste disposal fees income as well as solving a vexing disposal problem. Sewage sludge presents severe disposal problems for municipalities across the country. The problem of sewage sludge disposal has reached crisis proportions in many areas of the country. Although the benefit of concentrating the sludge slurry for combustion is evident, there is a major technical barrier, which is related to the rheological properties of the sludge. It would appear that the solids in a sludge slurry consist of both colloidal-sized particles and larger open-structures which trap a significant amount of water. As the sludge is concentrated, it begins to lose its fluid properties at about 10% solids and becomes a filter cake at 15% solids which must be handled as a solid, i.e. belt feeders, etc. This poses problems for incineration because feeding concentrated sludge requires mechanical feeders and combustion of the sludge requires a considerable amount of excess air (40--50%) and significant quantities of auxiliary fuels. Direct combustion of sludge in a resource recovery facility or an incinerator also leads to high levels of uncontrolled emissions including particulates and metals such as cadmium, mercury, etc. Expensive emission controls are required to meet EPA limits. The net result is a considerable add-on expense to sludge disposal with little recovery of the inherent Btu value. The overall goal of this project was to determine the technical and economic feasibility of supplementing the fuel cycle by incorporating combustion of waste material as a component of a coal water slurry. The specific goals included: conduct a sewage treatment plant survey to select a sample for testing; determine the physical and chemical characteristics of hydrothermally treated material; develop an optimum coal water sludge slurry; and provide an economic analysis of the operating expenses and order of magnitude capital cost estimates.

• Research Organization: Adelphi Univ., Garden City, NY (US)
• OSTI ID: 20082299
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
09 BIOMASS FUELS
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
CHEMICAL PROPERTIES
COAL
ECONOMIC ANALYSIS
FUEL SLURRIES
HYDROTHERMAL ALTERATION
MUNICIPAL WASTES
PHYSICAL PROPERTIES
SEWAGE SLUDGE
WASTE MANAGEMENT
WATER