Alternate cleaning processes

The process of fuel polishing is used to clean contaminated fuel on marine vessels (Johnson, 1998). The contaminated fuel (including water and sludge) is pumped from the tank, filtered and then returned clean to the tank. Service companies can provide this service at larger ports or provide the necessary equipment for use on the boat. 

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In summary, the road between initial development of alternative cleaning processes and implementation of those processes into the production environment is often long and full of potential potholes. This is especially true when implementing those processes for precision cleaning where the parts are typically complex and expensive, and the results of changes are not immediately apparent. 

Metal phthalocyanines are easily synthesized by vapor-phase condensation of four molecules of dicyanobenzene in the presence of molecular sieves such as faujasites or A1PO-5 (123-126). This results in direct entrapment of the macrocycle inside the molecular sieve s channels and cages. There are also reports of ship-in-a-bottle synthesis of porphyrins in zeolites, but since porphyrin synthesis requires a mixture of pyrrole and an aldehyde instead of a single compound, porphyrin synthesis is a much less clean process than phthalocyanine preparation (127). Alternatively, soluble porphyrins or phthalocyanines can be added to the synthesis gel of, for example, zeolite X. This also results in entrapped complexes (128). 

To use an ultrasonic cleaner, immerse the item to be cleaned in the cleaning solution within the device s tank. There are general-purpose and industrial-strength cleaning solutions as well as specific cleaning solutions for jewelry, oxides, and buffing compound removers. Turn the ultrasonic cleaner on for several minutes, and see if your item is clean. If not, repeat the process and/or try an alternate cleaning method. After an item has been cleaned, rinse as you would with a soap and water wash. 

There is also an excellent web site, SAGE (http //clean.rti.org), that provides a comprehensive guide to pollution prevention information on solvent and cleaning process alternatives. The U.S. EPA Air Pollution Prevention and Control Division developed SAGE (Solvent Alternatives Guide). 

This section describes the conventional manned clean room a later section in this chapter will address alternative aseptic processing environmental control designs with somewhat different features and control measures. 

The post-W CMP cleaning with ammonia in the past has caused wafer surface defect issues. Is it possible for you to determine alternative cleaning chemistries for the post-W CMP process Explain why you think they will provide a more efficient process. 

The technique may be viewed as an alternative to the addition of cosolvents or modifiers (sometimes termed entraimrs) that are commonly used in supercritical fluid technology to enhance the polarity of the fluid. For cleaning processes, however, these cosolvents may be toxic or detrimental in various ways to the substrate. In addition, these modifiers are usually more difficult to separate downstream from the process due to their high volatility. In contrast, surfactants typically have very low volatility and thus interact to a much lesser degree with the substrate. Furthermore, they often dramatically improve the solubility of polar species, well beyond that of simple modifiers. 

In summary, the varied nature of substrates being cleaned and the contaminants present, and the required reliability of military and space hardware has led to the development and use of a wide variety of alternative materials and processes rather than a single ODS replacement solvent or process. Supercritical fluid is one of these alternative processes and the rest of this chapter discusses the trials and tribulations associated with implementation of supercritical fluid as a production cleaning process. 

The second process investigated was an alternative for a xylene cleaning process. The dual-cycle (two step) process, as described previously in this chapter, is used due to the nature of the contaminant being removed. Figure 7 shows a bar chart of the annual costs (normalized) for the two processes. Once again the key differences are in the equipment and consumables. 

In many cases, membrane processes seem to be the most energy efficient separation processes available for industry. However, the costs related to cleaning or replacement of membranes, the need for skilled personnel, and the associated turn down costs determine their economical feasibility. Table 40.1 lists the various electrically assisted membrane processes with the type of effluents that could be treated most efficiently by each process. For most of the electrically assisted membrane processes (1 ), it is expected that the treatment of effluents would be most feasible when ion or particle concentration is high. These are also the effluents where alternative purification processes require a significant part of the process cost to be spent upon membrane... 

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