Cleaning process chemicals

R. Kaesemann, H. Fahlenkamp The meaning of droplet-droplet interaction for the wet fluegas cleaning process. Chemical Engineering Technology, 25(7), 739-742 (2002). 

The cleaning process proceeds by one of three primary mechanisms solubilization, emulsification, and roll-up [229]. In solubilization the oily phase partitions into surfactant micelles that desorb from the solid surface and diffuse into the bulk. As mentioned above, there is a body of theoretical work on solubilization [146, 147] and numerous experimental studies by a variety of spectroscopic techniques [143-145,230]. Emulsification involves the formation and removal of an emulsion at the oil-water interface the removal step may involve hydrodynamic as well as surface chemical forces. Emulsion formation is covered in Chapter XIV. In roll-up the surfactant reduces the contact angle of the liquid soil or the surface free energy of a solid particle aiding its detachment and subsequent removal by hydrodynamic forces. Adam and Stevenson s beautiful photographs illustrate roll-up of lanoline on wood fibers [231]. In order to achieve roll-up, one requires the surface free energies for soil detachment illustrated in Fig. XIII-14 to obey... 

To an experienced operator trained in the handling of industrial chemicals, the dimers present Httle cause for concern in handling or storage. The finished polymer coating presents even less of a health problem contact with the reactive monomer is unlikely. In the ancillary operations, such as cleaning or adhesion promotion, the operator must observe suitable precautions. Before using the process chemicals, operators must read and understand the current Material Safety Data Sheets, which are available from the manufacturers. 

Process-side cleaning. Either chemical or mechanical cleaning on the inside of the tubes can readily be accomplished. 

Used for small duties, clean process, and only infrequent cleaning required. Vaporization is usually less than 30%, but less than 15% if the fractionator pressure is below 50psig. The viscosity of the reboiler feed should be less than 0.5 cp. Put a butterfly valve in the reboiler inlet piping. This type is used in nearly 100% of chemical plant thermosyphon applications (70% of petrochemical). 

Avoidance of use of solvents, abrasive powders or process chemicals for skin cleaning. Provision of overalls of an appropriate type and their frequent laundering either in-house or by an approved contractor, with a prohibition on their unauthorized removal from the workplace or use in e.g. canteens. Disposable overalls are appropriate in some situations. 

Wet chemical processes A gas-cleaning process that uses certain chemicals to ensure the maximum retention of a given pollutant in the cleaning fluid. 

Zhang, R, Busnaina, A. A., Reng, J., and Rury, M. A., Particle Adhesion Force in CMP and Subsequent Cleaning Processes," Proceedings, 4th International Chemical-Mechanical Planarization for ULSI Multilevel Interconnection Conference, Santa Clara, CA, Reb. 11-12,1999, pp. 61-64. 

Avoidance of use of solvents, abrasive powders or process chemicals for cleaning. 

In general, the cleanup of oiled shorelines has been by mechanical, labor-intensive means. The use of surfactants to deterge and lift the oil from the surface results in more complete and rapid cleaning. Not only is the cleaning process more efficient, but it can also be less environmentally damaging because potentially less human intrusion and stress on the biologic community occurs and because the chemicals can make the washing more effective at a lower temperature. 

After the cleaning process, other techniques are used to prepare the surface of the substrate for coating. Some techniques include drying, surface etching, and chemical surface preparation. Examples of chemical surface preparation include the formation of an oxide layer or the monolayer assembly of an adhesion promoter on the surface. These processes modify the surface of the substrates so as to facilitate the subsequent deposition process. In surface preparation, frequently, the hydrophilic/hydrophobic character of the surface is controlled to match the coating solution properties. For example, Van Driessche et al.19 reported on improving the wettability of Ni-4at%W tapes... 

Direct electrochemical reduction and oxidation treatment of pollution involving a mass-free reagent - the electron - is a very attractive idea, because it is a uniquely clean process, as (1) the reduction and oxidation take place at inert electrodes and (2) there is no need to add chemicals. The techniques of cathodic reduction/anodic oxidation of wastewaters containing dyes are relatively new and have drawn the attention of investigators in Japan, China, USA and Russia [55]. 

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