Incinerators design considerations

Raw material usages per ton of carbon disulfide are approximately 310 m of methane, or equivalent volume of other hydrocarbon gas, and 0.86—0.92 ton of sulfur (87,88), which includes typical Claus sulfur recovery efficiency. Fuel usage, as natural gas, is about 180 m /ton carbon disulfide excluding the fuel gas assist for the incinerator or flare. The process is a net generator of steam the amount depends on process design considerations. 

Design considerations and costs of the catalyst, hardware, and a fume control system are direcdy proportional to the oven exhaust volume. The size of the catalyst bed often ranges from 1.0 m at 0°C and 101 kPa per 1000 m /min of exhaust, to 2 m for 1000 m /min of exhaust. Catalyst performance at a number of can plant installations has been enhanced by proper maintenance. Annual analytical measurements show reduction of solvent hydrocarbons to be in excess of 90% for 3—6 years, the equivalent of 12,000 to 30,000 operating hours. When propane was the only available fuel, the catalyst cost was recovered by fuel savings (vs thermal incineration prior to the catalyst retrofit) in two to three months. In numerous cases the fuel savings paid for the catalyst in 6 to 12 months. 

The SCWO process is able to achieve destruction efficiencies for organic waste comparable with those attained by incineration technology, without the requirement of expensive dewatering equipment. The key to a successful SCWO process is a design that integrates various unit operations. Important design considerations include ... 

Because of the hazards of handling radioactivity, special consideration should be given to the following features of incinerator design (a) packaging, (b) feed device, (c) combustion chamber, (d) fly ash and particulate removal, (e) ash removal. 

To achieve a high degree of combustion of the waste feed in a combustion system it is necessary to ensure an adequate combustion temperature, a sufficient excess supply of air, an ample mixing of the air and the thermal decomposition gas, and an adequate reaction time. In a successful incinerator design, careful consideration is given to the provision of adequate excess air and the appropriate location of the air supplies the combustion temperature is carefully controlled the gas flow velocities through the combustion chamber are adequately low and the gas and solid waste residence times in the combustion chamber are of sufficient duration. 

Disposal of exhausted soHds can be easily overlooked at the plant design stage, particularly when these have no intrinsic value alternative disposal methods might include landfiU of inert material or incineration, hydrolysis, or pyrolysis of organic materials. Liquid, soHd, and gaseous emissions are aU subject to the usual environmental considerations. 

Applicability/Limitations Liquid injection incineration can be applied to all pumpable organic wastes including wastes with high moisture content. Care must be taken in matching waste (especially viscosity and solids content) to specific nozzle design. Particle size is a relevant consideration so that the wastes do not clog the nozzle. Emission control systems will probably be required for wastes with ash content above 0.5 percent (particulate control) or for halogenated wastes (acid gas scrubbers). 

Worldwide, there are numerous plasma system designs for treatment of all types of wastes. Economical considerations limit their commercial applications to the most profitable actions. Presently they commercially operate in Switzerland and Germany for low level nuclear waste vitrification, in France and the USA for asbestos waste vitrification, in the USA and Australia for hazardous waste treatment, in Japan and France for municipal fly ash vitrification. The most of installations is working in Japan because there 70% of municipal waste is incinerated and the ash can not be used as landfill. EU Regulations banning the disposal to landfill of toxic and hazardous wastes after year 2002 may cause wider use of plasma waste destruction technology in Europe. 

While earlier studies addressed the incineration of pesticides and pesticide wastes as such, most current efforts are focused on the general area of hazardous waste, as defined by the Resource Conservation and Recovery Act of 1976. This ongoing work is directly related to pesticide disposal, however, as pesticide waste is included in the category of RCRA hazardous waste. In fact, the presence of pesticides is a major consideration in a waste being designated as hazardous. 

Considerable design effort has been invested in the improvement of incineration systems. D.A. Tillman fEbasco Environmental) and associates report that "Rotary kilns have become the incinerators of choice for eliminating hazardous wastes in accordance with the U.S. Resource Conservation and Recovery Act, Superfund, and related legislation. ... 

The UMC applies to the addition to or erection, installation, alteration, repair, relocation, replacement, use or maintenance of heating, ventilating, cooling, refrigeration systems, incineration, or other miscellaneous heat-producing appliances. It also covers design. In effect, there is a considerable amount of overlap with NFPA 90A.9... 

Two small commercial incineration facility designs are under consideration. The first design involves a liquid injection incinerator and the second a rotary kiln incinerator. For the liquid injection system, the total capital cost (TCC) is 2.5 million, the annual operating costs (AOC) are 1.2 million, and the annual revenue generated from the facility R) is 3.6 million. For the rotary kiln system, TOC, AOC, and R are 3.5, 1.4, and 5.3 million, respectively. Using straight-line depreciation and the discounted cash flow method, which design is more attractive Assume a 10-yr facility lifetime and a 2-yr construction period. Note that the solution involves the calculation of the rate of return for each of the two proposals. 

Of importance to note was the considerable level of public involvement in the extensive tesbng and evaluation of potential technologies as alternatives to incineration for this application, and the strong public support demonstrated for SCWO. The program is currently in the design stage, with the expected completion date for the plant projected for 2011. 

Burners for commercial boilers vary considerably on the worldwide market in design, control scheme, and applications ranging from commercial snow melting and municipal solid waste incineration to water and space heating for hospitals, hotels, and restaurants. Most burners may be classified and described in terms of a few basic features or characteristics. Figure 19.2 illustrates the basic boiler burners classification. 

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