Waste continued process

An important advantage of the electrochemical technique lies in its simplicity because metals are much easier to handle than metal halides and are always commercially available the consumption of the solvents is also much smaller than for conventional techniques [1639, 1612]. The electrochemical method allows the creation of a highly efficient, low-waste continuous process for commercial production of metal alkoxides [948]. 

Process operations. The third source of process waste we can classify under the general category of process operations. Operations such as start-up and shutdown of continuous processes, product changeover, equipment cleaning for maintenance, tank filling, etc. all produce waste. 

Sources of waste in process operations a. Start-up I shutdown in continuous processes... 

In continuous processes, all those sources of process waste associated with start-up and shutdown also apply to product changeover in multiproduct plants. 

In both batch and continuous processes, it may be necessary to clean equipment to prevent contamination of new product. Materials used for equipment cleaning often cannot be recycled, leading to waste. 

C. uti/is yeast is produced by either fed-batch or continuous processes. Aerated-agitated fermentors range up to 300 m total capacity and ate operated in the same manner as described for S. cerevisiae (2,5). C. utilis is capable of metabolizing both hexose and pentose sugars. Consequendy, papermiU wastes such as sulfite waste Hquot that contain these sugars often ate used as substrates. 

The raw potassium manganate(VI) from the secondary roaster or the Hquid-phase oxidizer contains a fair amount of insoluble material such as unreacted MnO and ore gangue. In most continuous processes, these insolubles are removed by sedimentation using thickeners or filtration and are disposed of as waste. 

Solution Polymerization. In this process an inert solvent is added to the reaction mass. The solvent adds its heat capacity and reduces the viscosity, faciUtating convective heat transfer. The solvent can also be refluxed to remove heat. On the other hand, the solvent wastes reactor space and reduces both rate and molecular weight as compared to bulk polymerisation. Additional technology is needed to separate the polymer product and to recover and store the solvent. Both batch and continuous processes are used. 

Continuous processes may be used for the production of yeast biomass. Raw Hquid feed is added continuously to the fermentor and an equal volume of fermentor Hquid is removed to harvest the yeast ceUs. These may be a single homogeneous fermentation in a stirred fermentor or two fermentors in series. Growth rates are high a typical dilution rate in the production of C. utilis on sulfite waste Hquor is 0.25, ie, one-fourth of the fermentor volume is harvested hourly. 

A three-step nitration process of toluene is described. The advantages of the modified process are reduced waste, less hazardous operation, reduced oleum requirement, partial replacement of coned HN03 with dil HN03, and higher rate of toluene flow into the reactor (Ref 86) The continuous process of H.C. Prime (Ref 73) for preparing TNT was studied by thin-layer chromatography on silica gel with a starch binder and a fluorescent indicator. The nitration... 

Adipic acid and HMDA are obtained from nylon-6,6 by die hydrolysis of die polymer in concentrated sulfuric acid (Fig. 10.7). The AA is purified by recrystallization and the HMDA is recovered by distillation after neutralizing die acid. This process is inefficient for treating large amounts of waste because of die required recrystallization of AA after repeated batch hydrolyses of nylon-6,6 waste. In a continuous process,5 nylon-6,6 waste is hydrolyzed with an aqueous mineral acid of 30-70% concentration and the resulting hydrolysate is fed to a crystallization zone. The AA crystallizes and the crystals are continuously removed from the hydrolysate. Calcium hydroxide is added to neutralize the modier liquor and liberate the HMDA for subsequent distillation. 

Both continuous and batch methods may be used in methanolysis. The batch mediod requires an autoclave, crystallizer, and centrifuge and a system for the melting and distillation of the DMT obtained. In the two-stage Hoechst continuous process, waste PET is melted and fed to a reactor. Preheated methanol is added to the autoclave, which is equipped with a mixer. The conversion reaches 70-90% in the first reactor, after which the reaction stream is introduced into a second autoclave at a lower temperature near the bottom, where it rises slowly and die higher density impurities settle at the bottom. The reaction stream leaves the second autoclave and its pressure is reduced to 0.3 MPa. On further reduction of the pressure and cooling, DMT precipitates and is subsequently purified.12... 

A further application of this technology will certainly be the fabrication of membranes of these materials. Membrane reactors have shown great utility in many systems, where one component of a reaction mixture can be separated by permeation through a membrane, thus driving a reaction forwards, by continuous separation. Such continuous processes can themselves save a great deal of waste. 

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. 

In a joint project between the Waste and Resources Action Programme (WRAP) and Coca Cola Enterprises in the UK it proved possible by redesigning bottle production to reduce the weight of 500 ml PET bottles by 8%. These lighter bottles meet all of the required performance standards, and when production reaches the full scale of 700 million p.a. will save 1400 tonnes of PET. This may seem to be a small improvement, but lightweighting of drinks bottles has been a continuous process for many years, and yet progress is still possible. 

These stages are usually merged into a continuous process. The process performs one or more of the following functions (i) production of a finished waste product and an enriched concentrate for further concentration (ii) production of a finished concentrate and a rejectable waste and (iii) production of a finished concentrate and a low-grade reject, plus a middling for additional treatment. 

Batch-type production processes, particularly those with small batch sizes, have less energy efficiency as compared to continuous processes. A typical example of a batch operation on a relatively small scale is the production of titanium in 1-ton batches of the metal. The energy efficiency of the process is much less than that of continuous methods such as iron being produced in a blast furnace, or even of large-scale batch methods such as basic oxygen steel-making. The heat losses per unit of production are much less in continuous and large-batch processes, and this also enables the waste heat from process streams to be used. 

AVM [Atelier de Vitrification de Marcoule] A continuous process for immobilizing radioactive waste by incorporation in a borosilicate glass. Developed at Marcoule, France, in 1972, based on the earlier PIVER process. In 1988, two larger vitrification plants were... 

Rieckmann, Th., Poly condensation and recycling of PET fibres and other PET waste by continuous processes, presentation given at the 5th Conference on Man-Made Fibres, Beijing, China, 1994. 

Process flow, photographic waste - Continuous Recorded... 

The innovative features of the system include proprietary reagents, the pug mill designed by Chemfix, and the continuous nature of the process. Because it is a continuous process, waste material can be treated more quickly, thus lowering the cost per ton of material treated. 

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