Resource Recovery From Municipal Solid Wastes

Volume II: Final Processing

Luis F. Diaz, George M. Savage, Clarence G. Golueke

• Publisher: CRC Press
• Year: 2018
• Print ISBN: 9781315897271
• eBook ISBN: 9781351093279
• Topic: Biological Sciences
• Subtopic: Environmental Science
• Index: Biological Sciences

This text includes two volumes discussing resource recovery form municipal solid wastes. Volume 2 discusses in more detail the final processing including; incineration, preparation and use of refuse-derived fuel, biological resource recoveyr, biogas production, hydrolysis and single cell protein and ethanol production, composting, environmental aspects, and landfill.

Chapter 1
Incineration

I. Introduction

A. Methods of Thermal Energy Recovery

Energy can be recovered directly from municipal solid waste (MSW) as heat, or the waste can be processed into a storable fuel. Direct recovery is accomplished by mass burning. Indirect recovery can take several forms and involve many different procedures, each of which may be fitted into one of the three categories: physical, thermal, and biological. In physical processing, the MSW is processed such that its combustible and noncombustible fractions are separated one from the other. The physical characteristics of the combustible fraction are further altered to enhance its utility as a fuel. The resulting combustible product commonly is termed "refuse-derived fuel" or simply "RDF". In thermal processing, usually termed "pyrolysis", the goal is to convert the waste almost entirely into a combustible gas. However, the usual outcome is a collection of solid, liquid, and gaseous products that are more or less combustible. The product from biological processing may be either gaseous or liquid, depending upon the system used. Descriptions and discussions of biological and thermal processing are presented in detail in other sections of this book.

Of the several thermal energy recovery processes, mass burning and RDF production are regarded as having the greatest potential, even though several obstacles may impede the attainment of the full realization of that potential. Some of the obstacles are technical in nature; others are related to marketing. Both types of obstacles can be overcome in part by using the heat energy to generate steam and then market it (steam) off-site for the generation of electricity, for heating and cooling, or for a combination of the two. However, such an approach is circumscribed by limitations that restrict its application to only a few localities. Consequently, public officials, particularly in large metropolitan areas, are forced to go on to the next potential solution, namely, on-site generation of electricity. A difficulty attending the generation of electricity is that the community or agency must construct a power plant and install transmission and distribution equipment. In short, the community would have to assume the functions of an electrical utility. Two alternatives to steam and electrical generation are (1) sell the fuel (RDF) to individual customers for use in power generation by them; or (2) sell the fuel to the local utility. The first approach could prove to be quite costly. On the other hand, with the second approach, not only would the utility benefit through the use of an inexpensive fuel, the disposal problem would also be significantly lessened. However, it should be noted that even though it would seem that utilities would be ideal users of RDF, certain technical, economical, and institutional issues remain to be resolved before the utilization becomes a common practice.

Incineration

The use of incineration as a means of disposing of municipal refuse is by no means a recent one, as is attested by the fact that it was described as a viable and ongoing practice in a book published in 1901.¹ The early interest in incineration stemmed from the fact that in terms of disposal, a maximum volume or weight reduction could be achieved. In the U.S. this early period of promise came to an all but complete end in the mid 1960s, a time when extremely few of the early incinerators were as yet in operation. The responsible problem was mainly one of an excessively large emission of particulates. However, it should be pointed out that the early popularity continued to be strong in western European nations. A major contributing factor to the continuation of the acceptance in Europe was the practice prevalent there of incorporating energy recovery into the incineration process. A belated recognition of the energy potential of incineration finally is bringing about a resurgence of interest in the practice in the U.S. An important factor in this recognition is the realization of the continuing increase in the heating value of refuse being brought about by a corresponding rise in the ratio of plastics and paper to food preparation wastes and garden debris. In recent years, Japan has taken the lead over Europe and the U.S. in terms of numbers and capacities of incinerators.

II. Technology

A. General Design Features

Key features of an incineration facility are (1) the tipping area; (2) the storage pit; (3) the equipment for charging the incinerator (typically, a crane or a front-end loader); (4) the combustion chamber; (5) the stack emission cleaning equipment; and (6) the boiler, if energy is to be recovered.

In a typical incinerator operation, the municipal solid waste (MSW) is discharged from collection vehicles either onto a tipping floor or directly into a storage pit. The pit serves a twofold purpose: (1) It permits the storage of an amount of refuse sufficiently large to ensure, if desired, a 24-hr/day, 7-day/week operation of the incinerator; and (2) it provides an area where large noncombustible items can be removed, and the remaining wastes can be blended into a fairly uniform and constant charge. The waste is transferred from the pit to a charging hopper. The charging hopper is designed to maintain a continuous feed of waste into the furnace. The waste falls from the hopper into the furnace and onto the furnace stoker, where combustion takes place.

The furnace is the essential element of an incineration system. It may be rectangular or cylindrical in shape, and may consist of only one chamber or may have a primary and a secondary chamber. The principal function of the secondary chamber is to provide the conditions needed to complete the combustion process. The size and shape of the furnace usually are determined by the manufacturer, and usually are based upon a number of parameters, among...

Table of contents

• Cover
• Title
• Copyright
• THE AUTHORS
• Contents
• Chapter 1 Incineration
• Chapter 2 Production and Utilization of Refuse-Derived Fuel
• Chapter 3 Biological Resource Recovery
• Chapter 4 Biogas Production
• Chapter 5 Hydrolysis and Single-Cell Protein and Ethanol Production
• Chapter 6 Composting
• Chapter 7 Environmental Aspects
• Chapter 8 Landfill—The Ultimate Disposal
• Index