Solid waste continued process

In conclusion, the technology of total liquefaction of apple allows to work with a continuous process with less labour and faster than with a classical one, to get a high and constant yield during the whole processing season at a very high level (93- 95%), to get a pulp with a low content of solids (about 20% in volume) which can be centrifuged instead of pressed (lower investment in equipment), to decrease the quantity of waste pomace, to decrease the production costs. Liquefaction technology allows to process different fruits with the same process, at last to liquefy fruits for which no equipment had been developed to extract the juice or for which the use of pectinases did not allow to get juice such as tropical fruits. 

Life-cycle assessment methodology has been used since the 1960s with early studies that focused solely on energy usage and solid waste issues. This focus continued in life-cycle assessments performed during the oil crisis in the 1970s.86>87 The unique aspect of all of these initial studies was the early development and use of life-cycle data inventories with less emphasis on environmental risk impacts of the associated processes studied. A method published by the Royal Commission on Environmental Pollution in 1988, employing the Best Practicable Environmental... 

The recovery of heavy metals from solid waste poses more challenges. The Eastman Chemical Company process for the manufacture of acetic anhydride by the carbonylation of methyl acetate involves a proprietary process for the continuous recovery of rhodium and lithium from the process tar (see Section 4.6). 

Effective engineering design of the cracking reactor for waste plastic processing is very important since the carbonaceous solid residue is one of the cracking products (levels up to 10% or more) and its continuous removal from the reactor is necessary to ensure profitable running. Stirred vessel reactors which have augers in the bases to facilitate continuous char removal are presented. 

The fluidized-bed process shown in Figure 25.13 is a continuous waste treatment process [32]. The polymer can be fed directly into the fluidized bed. Volatile products leave the reactor with the gas stream. Solid products such as fillers and char can be removed by exchanging the bed material. In a temperature range between 510 and 730°C 38-49%... 

The PAC activated slndge system is a modified activated sludge process. PAC is added to the aeration tank where it is mixed with the biological solids. The mixed liquor solids are settled and separated from the treated effluent in a gravity clarifier. Polyelectrolyte will normally be added prior to the clarification step to enhance solids-liquid separation. If phosphorus removal is necessary, alum is often added at this point. Even with polyelectrolyte addition, tertiary filtration is normally required to reduce the level of effluent suspended solids. The clarifier nnderflow solids are continuously returned to the aeration tank. A portion of the carbon-biomass mixture is wasted periodically to maintain the desired solids inventory in the system. 

A continuous flow of the solid waste stream, from its initial feeding into the processing plant until its exit in the form of final products, is necessary so that separation is efficient and economically viable. Among other factors, the uniform and controlled feeding of process units and equipment as well as the continuous handUng of the products secure the efficient operation of a solid waste separation plant. 

LLNL performed an extended one-day (8 hr) test of the solids recirculation system, with continuous injection of approximately 0.035 gal/min of waste for a period of 7 hr. Over the injection period, 50 gal of waste was processed. Continuous on-line gas analysis tracked the progress of the experiment and quantified the decomposition products. 

A number of methods for PET methanolysis have been described in the patent literature, operating under both batch and continuous conditions. One of the major problems with the continuous process is the difficulty of introducing the solid polyester wastes into the methanolysis reactor working under high pressure. For this reason, methanolysis often takes place in batch systems, with all the problems and limitations associated with batch operation. 

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