Utility systems, waste minimization

The utility system also creates waste through products of combustion from boilers and furnaces and wastewater from water treatment, boiler blowdown, etc. Utility waste minimization is in general terms a question of ... 

The sulfuric acid used to dry the chlorine is also sometimes a source of ammonia compounds. Finally, the plant utilities are likely sources. Plant water that has not been thoroughly purified has many opportunities to enter the process. Examples of these opportunities are the use of impure water to prepare treatment chemical solutions, flushing water on rotating machinery seals, water recycle from waste-minimization systems, and direct-contact cooling water. Steam and its condensate are also potential sources. The culprits here usually are the amines used as corrosion inhibitors in the steam system (Section 12.3.2). 

Chang and Wang (1996) described a multiobjective programming approach to waste minimization in the utility systems of chemical process, using the concept of global emissions of gaseous pollutants. This model merging economic and environmental concerns in the utility system synthesis was stated for fixed utility demands. 

Chang, C.-T. and Hwang, J.-R., 1996, A Multiobjective Programming Approach to Waste Minimization in the Utility Systems of Chemical Processes. Chem. Eng. Sci., 51(16), 3951-3965. 

The properties of the fuel salt used in these simulations are summarized in Table 7.2. The fuel salt considered in the simulations is a molten binary fluoride salt with 77.5 mol% of lithium fluoride the other 22.5 mol% is a mixture of heavy nuclei fluorides. This proportion, maintained throughout the reactor evolution, leads to a fast neutron spectrum in the core as shown in Fig. 7.2. Thus this MSFR system combines the generic assets of fast neutron reactors (extended resource utilization, waste minimization) and those associated with a liquid-fueled reactor. 

Contactor design is important in order to maximize the ozone-transfer efficiency and to minimize the net cost for treatment. The three major obstacles to efficient ozone utilization are ozone s relatively low solubility in water, the low concentrations and amounts of ozone produced from ozone generators, and the instability of ozone. Several contacting devices are currently in use including positive-pressure injectors, diffusers, and venturi units. Specific contact systems must be designed for each different application of ozone to wastewater. Further development in this area of gas-liquid contacting needs to be done despite its importance in waste treatment applications. In order to define the appropriate contactor, the following should be specified ... 

Hydrolysis. The hydrolysis of dialkyl and monoalkyl sulfates is a process of considerable interest commercially. Successful alkylation in water requires that the fast reaction of the first alkyl group with water and base be minimized. The very slow reaction of the second alkyl group results in poor utilization of the alkyl group and gives an increased organic load to a waste-disposal system. Data have accumulated since 1907 on hydrolysis in water under acid, neutral, and alkaline conditions, and best conditions and good values for rates have been reported and the subject reviewed (41—50). 

All of the disadvantages of throwaway flue gas treatment systems can be lessened considerably by minimizing the amount of waste material produced. This can be accomplished by the choice of an effective sorbent material and the use of sorbent recycle to increase utilization. In turn, sorbent recycle can be optimized by the use of a separation process to remove the spent sorbent from unreacted sorbent. As water usually contributes significantly to the mass of the waste produced, the dewatering characteristics of the waste material are important. Efficient dewatering will not only minimize water losses but also reduce the disposal space required. 

Civilian applications are numerous, but most funding of SCWO technology has stemmed from the military s need to find a safe and effective alternative to incineration of their wastes, as well as the need to clean up mixed wastes (radioactive and hazardous organic materials) at DOE weapons facilities. For better utilization of SCWO for its application to a wide range of waste types, a better fundamental understanding of reaction media, including reaction rates, reaction mechanisms, and phase behavior of multicomponent systems is required. Such an understanding would help optimize the process conditions to minimize reactor corrosion and salt... 

Compared to conventional chemical processes, the use of microbial systems offers the advantages of reduction of wastes as well as minimization of costs and pollutant gas emissions. In addition, the ability of utilizing renewable sources instead of non-renewable ones, turned industrial biotechnology into a key technology for the development of a sustainable chemical industry [9, 10],... 

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