Waste Particle size

Particle size. The material handling properties of solid wastes are dependent upon particle size. This appfies as well to feed preparation and air pollution control which are affected by solid-waste particle size and cohesiveness. For wastes such as bulk soils, the amount of fines (from clay and silt) is critical for system design. Cohesiveness, which varies with moisture content, is important for Din and conveyor design. 

The information supplied above shows that waste composition, moisture content, waste particle size, waste density, temperature and pH will all affect both the extent and the rate of waste degradation.. However, very little of this knowledge has been utilised by landfill operators in their management of landfill sites until control of these parameters is attempted on an operational landfill, it will be impossible to know to what extent the bioreactor landfill can meet the... 

From a practical point of view, water field capacity and hydraulic conductivity are very important physical waste parameters. These properties determine the amount of leachate and their formation rate. Based on the values of these parameters the operational conditions for liquids recirculating inside the landfill can be determined. These parameters depend mainly on waste particle size and organic matter content, which determine pore size distribution and the porosity of the medium. Field capacity is the value of water content held in the material after the gravitational water has drained away. The field capacity of municipal solid waste varies over a wide range between 14-44%i v/v (Zeiss Major, 1992/93, Bengtsson et al. 1994). According to an evaluation by Reinhardt and Ham (1974) the volume of liquid addition, which allows a water field capacity in waste to be reached varies between 0.1-0.2 m per Mg of solid waste (25,000-50,000 gallons per 1,000 tons). 

Aerosol products are hermetically sealed, ensuring that the contents caimot leak, spill, or be contaminated. The packages can be considered to be tamper-proof. They deUver the product in an efficient manner generating Httie waste, often to sites of difficult access. By control of particle size, spray pattern, and volume deUvered per second, the product can be appHed directiy without contact by the user. For example, use of aerosol pesticides can minimize user exposure and aerosol first-aid products can soothe without applying painful pressure to a wound. Spray contact lens solutions can be appHed directiy and aerosol lubricants (qv) can be used on machinery in operation. Some preparations, such as stable foams, can only be packaged as aerosols. 

Specific gravity is the most critical of the characteristics in Table 3. It is governed by ash content of the material, is the primary deterrninant of bulk density, along with particle size and shape, and is related to specific heat and other thermal properties. Specific gravity governs the porosity or fractional void volume of the waste material, ie. 

Specific gravity is direcdy related to the bulk density of waste fuels prepared ia a variety of ways. Solid oven-dry (OD) wood, for example, has a typical bulk density of 48.1 kg/m (301b/ft ). In coarse hogged form, eg, <1.9-cm minor dimension, this bulk density declines to about24kg/m (151b/ft ). In pulverized form, at a particle size <0.16 cm, this bulk density declines to 16—19 kg/m (10—12 Ib/ft ). Similar relationships hold for municipal waste, agricultural wastes, and related fuels. 

Carbide lime is a waste lime hydrate by-product from the generation of acetylene from calcium carbide and may occur as a wet sludge or dry powder of widely varying purity and particle size. It is gray and has the pungent odor associated with acetylene (see Hydrocarbons, acetylene). 

Waste pretreatment Suspended solid less than 10 to 15 mg/L particle sizes equal to or less than 1 to 5 im (depends on the pressure may require changes in operating procedures. 

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). 

Applicability/Limitations Fluidized beds require frequent attention for maintenance and cleaning purposes. This treatment is ideal for slurries and sludges but not for bulky or viscous wastes. The waste particles should be of a certain size and be homogeneous. Wastes must have a low sodium content and a low heavy metal content. Some refractory wastes may not be fully destroyed since these units operate at low combustion temperatures (750 to 1000°C). 

Particle size distribution relating to gas cleaning is well understood in the industry. This section deals with general rules of thumb. Certain important issues not included in this section are flue gas desulfurization, flue gas denitrification, hazardous waste gas cleaning, waste incineration gas cleaning, and removal of CO2 from flue gas. All these topics have special requirements, which must be considered separately in the design process. 

The rotary kiln design allows for accepting a mix of high-chlorinated wastes (solvents, chlorinated tars, plastics). Such kilns are usually designed in relation to a specific optimal calorific value in the input. The input mix should be set in such a way that this optimal composition is approached (e.g., PVC waste and other waste streams with a lower calorific value). It is likely that a 100% input of PVC would lead to all kind of problems of temperature control due to its relatively high calorific value. Chlorine contents of over 50% can easily be accepted. A final demand is that the particle size should be 10 x 10 x 10 cm at maximum. This implies that sometimes waste has to be shredded before it can be put into the kiln. Other acceptance criteria have not been published in literature. 

Crushing and screening of the waste to the required particle size ... 

A number of reviews are already available on the above subject. Rothemeyer [50] discussed the effects of grinding and sieving on the particle size, stmcture, and distribution of powders obtained from waste rubber and also studied the effects of different powders on the physical properties of the... 

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