Processing waste, utilization

In Chap. 10, modification of the process for reducing process waste was considered in detail. It also was concluded that to minimize utility waste, the single most effective measure would be improved heat recovery. The energy-targeting methods presented in Chaps. 6 and 7 maximize heat recovery for a given set of process conditions. However, the process conditions can be changed to improve the heat recovery further. 

The need to meet environmental regulations can affect processing costs. Undesirable air emissions may have to be eliminated and Hquid effluents and soHd residues treated and disposed of by incineration or/and landfilling. It is possible for biomass conversion processes that utilize waste feedstocks to combine waste disposal and treatment with energy and/or biofuel production so that credits can be taken for negative feedstock costs and tipping or receiving fees. 

An improved solvent extraction process, PUREX, utilizes an organic mixture of tributyl phosphate solvent dissolved in a hydrocarbon diluent, typically dodecane. This was used at Savannah River, Georgia, ca 1955 and Hanford, Washington, ca 1956. Waste volumes were reduced by using recoverable nitric acid as the salting agent. A hybrid REDOX/PUREX process was developed in Idaho Falls, Idaho, ca 1956 to reprocess high bum-up, fuUy enriched (97% u) uranium fuel from naval reactors. Other separations processes have been developed. The desirable features are compared in Table 1. 

Gas versus steam turbines can involve a major side study. The result can be different for the process and utility sides of the plant as shown in Reference 13. For the gas turbine case, simple cycle versus waste heat boilers can be studied. Usually, waste heat boilers will win out unless the plant is in a cheap gas country. If gas turbines are selected for power generation, black start capability is usually a good investment. 

Waste products from a number of commercial processes can be used as cheap and readily available fillers for PCM. For example, lightweight structural materials may be obtained by filling various low-viscous resins with waste materials [4, 5]. Also by adding fillers to reprocessed polymers it is possible to improve their properties considerably and thus return them to service [6]. This method of waste utilization is not only economically feasible but also serves an ecological purpose, since it will help to protect the environment from contamination. The maximum percentage of the filler should in these cases be such as to assure reliable service of the article made from the PCM under specified conditions for a specified period of time. 

The waste streams created by utility systems tend, on the whole, to be less environmentally harmful than process waste. Unfortunately, complacency would be misplaced. Even though utility waste tends to be less harmful than process waste, the quantities of utility waste tend to be larger than process waste. This sheer volume can then result in greater environmental impact than process waste. Gaseous combustion products contribute in various ways to the greenhouse effect, acid rain and can produce a direct health hazard because of the formation of smog. The aqueous waste generated by utility systems can also be a major problem if it is contaminated. 

Both concentrated and dilute waste were sent to a pair of John Zink thermal oxidizers equipped with adjustable venturi scrubbers for removal of particulates prior to stack discharge. Water process waste originating primarily from fermentation sectors was sent to the Carver-Greenfield evaporation system. The evaporator utilized a multistep oil dehydration process and was equipped with a centrifuge, waste heat boiler, and a venturi scrubber. The Clinton Laboratory reported an overall BOD and COD reduction of 90 and 99%, respectively, depending upon the configuration used. 

In 1996, Delphi estimated the cost of processing wastes at 2.50 to 10.00/kg. Among the factors listed as affecting cost were quantity of waste, labor rates, initial contaminant concentration, characteristics of residual waste, waste handling and pretreatment, amount of debris, utility/fuel rates, and target contaminant concentration (D13821G, p. 24). 

In summary, compared with earlier processes which utilize hazardous solvents and generate large waste streams, the carbonylation of chloropinacolone offers an environmentally and operationally advantaged process since it requires (r) very little excess amine or methanol, (fr) no extraneous reaction solvents, Hi) little or no extraction solvent, and (fr) the tributylamine coreactant and methanol components are readily recycled. This was accomplished while also demonstrating similar yields, shorter reaction times, and higher product concentrations which result in a significant reduction in the number of batches and time required to produce significant quantities of methyl pivaloylacetate. 

Horwitz, E.P., Kalina, D.G., Diamond, H Vandegrift, G.F., Schulz, W.W. The TRUEX process - a process for the extraction of the transuranic elements from nitric acid wastes utilizing modified Purex solvent. Solvent Extr. Ion Exch. (1985), 3 (1 2), 75-109. 

Horwitz, E. P., D. G. Kalina, H. Diamond, et al. 1985. The TRUEX Process - A Process for the Extraction of the Transuranium Elements from Nitric Acid Wastes Utilizing Modified PUREX solvent. Solvent Extr. Ion Exch. 3, 75-109. 

The direction of human activity is determined by the intensity of pollution, time the pollution lasted (waste utilization), cost of environmental cleaning, amount of investment in the renewal of resources and in the prevention of environmental pollution, investment in industry and agriculture, rate of natural resource expenditure, and search for new sources, etc. The hypothetical trends of these processes should be set in order to realize the predictions using the global model. 

The food processing industry produces extremely large quantities of wastes. It has been suggested that this industry could benefit from enzymatic processes for (1) more efficient utilization of raw materials (2) processing waste streams to produce marketable by-products (3) processing of raw... 

The surface properties of the aluminum oxide in aqueous solutions play an important role in the technology of dispersed system processing and utilization of wastes containing alumina oxides or hydroxides. The wide abundance and application of alumina oxide caused intensification of their investigations in colloid chemistry. Especially coagulation, flocculation, filtration and ion exchanging properties of the systems were examined. For all these processes, the electrical properties of the interface, that rule the accumulation and transportation of the charge, are very important. 

---