Resource Recovery and Conservation最新文献

In this paper the role of the nitrogen industry in environmental pollution is characterized, and an ion exchange method for purification of waste water formed in the process of ammonia synthesis is proposed. The process consists of sorption of ammonium ions in the bed of a strong acid cation exchanger and regeneration with 50% and 33% solutions of sulphuric acid. It is shown that the ammonium sulphate obtained during regeneration can be used in the production of saltpetre. Addition of regeneration effluent to saltpetre increases the durability of saltpetre granules. The optimum dose is 1.6 eq H₂ SO₄/dm³ cation exchanger without significant difference in regeneration efficiency between 33% and 50% H₂SO₄. It appears this method has considerable economical advantages.

A practical systems-based methodology for the investigation of the environmental impact of alternative resource recovery strategies is described in application to the problem of used car tyre disposal. The study involved the construction of a computer-based model of the car tyre system and the use of this model to examine various scenarios. A short-term plan for dealing with the car tyre disposal problem in the United Kingdom is suggested from the model. This involves placing a greater emphasis on the recycling of re-usable tyre carcasses and on the use of reclaimed rubber, and the increased use of incinerators to generate power from those used tyres which would otherwise be tipped. The methodology itself is of quite general application and could be used in many other areas for resource or environmental impact analysis.

The key parameters controlling the size reduction of refuse have been identified as being flow rate, refuse moisture content, mass of material held within the shredder (the shredder holdup), residence time for material in the shredder, and the physical layout of the shredder. Product particle size distribution is a function of the feed particle size and the mean residence time, while the power requirements of the shredder are a function of the holdup and the moisture content of the refuse. Relations between the governing parameters are quantified and shown to be useful for predictive purposes. Factors influencing the design of shredders are also considered.

The Town of Hempstead has been operating energy from refuse plants since 1950. This paper presents the experience gained from the operation of the Town's two heat recovery plants specifically in the areas of boiler tube metal wastage, boiler fouling, particulate emission control, and maintenance and availability experience.

Almost 30 years ago the Town of Hempstead began a pioneering experience in waste heat extraction from mass burning of refuse at Merrick, New York. This plant incorporated waste heat boilers and produced power so as to be totally independent of the local power system. In 1962 our firm was authorized to design a second mass burning refuse incinerator with boilers and power generation for the Town of Hempstead at Oceanside, New York. This paper outlines the experience gained at these two installations over the past 30 years.

Design considerations for constructing a pilot anaerobic digester are presented. A 4.34 m³ pilot digester was constructed using these criteria. Operational guidelines are presented. Also included is an iterative technique for sizing an internal heat exchanger, suggestions for selecting pumps, meters, and other equipment, and an electrical control system that permits automation of the entire system. The pilot digester operated successfully for more than 4 years with swine manure as a feedstock at a loading rate of 4 kg volatile solids per m³ per day with a 15-day detention time at 35°C. Energy balances indicate that the overall energy efficiency of the digester is a function of ambient temperature surrounding the digester, amount of agitation, and amount of insulation.

Gasification means here the reaction of solid fuels with air to yield a low calorific value gas, suitable as a fuel. The solid fuels considered are agricultural and forest industry residues, biomass fuels. Biomass-derived gas is an alternative to natural gas.

A laboratory-scale downdraft gasifier was used to study the gasification properties of certain biomass fuels. The grate is the most critical part of the gasifier. Two designs were tested: a rotating eccentric grate and a perforated steel basket. The latter was specifically designed for use with granular fuels such as mulled walnut shells.

Batch tests were performed with different biomass fuels and at varying fuel consumption rates. Biomass fuel consumption rate was determined by mounting the gasifier on a platform scale and weighing it before and after a run. The composition of the generated gas and the mass and heat balances were determined. Substantial closure errors are reported. These are considered to be the result of tars in the gas which were not accounted for.

Yields varied from 75.5% in the case of walnut shells to 46% for rice hulls. With a biomass fuel consisting of a mixture of two sizes of walnut shells, yields in excess of 80% were recorded at high fuel consumption rates.

Some practical aspects concerning the gasification of biomass fuels and problems associated with cotton gin trash, rice hulls, and wood residues are discussed.

The technology of fuel gas production by anaerobic digestion, which has been available for many years, has only recently been recognized as a potential alternate energy source. Until recently, the emphasis of this technology has been the treatment of waste materials to eliminate pollution rather than the economically feasible recovery of methane, one of the products of anaerobic digestion. An application which shows promise to furnish energy is the digestion of animal residues. Experiments reported in the literature have shown the technical feasibility of the use of this technology with animal residues, and several reports have been issued recently which discuss the economics of fuel gas production by anaerobic digestion of animal residues. The objective of this review is to develop a detailed technical perspective of the scope of the anaerobic digestion process and the problems and prospects for exploitation to produce methane from animal residues. It is concluded that the technology of anaerobic digestion and the economics of this technology make fuel gas production from selected animal residues meritorious for development.