Cleaning efficiency

The models described in the following use only one parameter for the cleaning efficiency, which is thus a simplification that must be kept in mind when using these models. This works quite well as long as the efficiency value is the smallest one—e.g., the efficiency for the most penetrating particle size or the efficiency for the most penetrating gas concentration. 

The following differential equation (or something similar), derived from a mass balance for the room, is solved to find the correlation between flow rates, source rate, contaminant concentrations, cleaning efficiency, and time. 

From this equation it is clear that if either flow rate or cleaner efficiency for the recirculation system is zero, there will be no change in contaminant concentration. Also, a low flow rate can only be compensated to a small degree by a higher cleaning efficiency, but a low cleaning efficiency can be compensated to some degree by increasing the flow rate. 

This equation makes it quite easy to calculate necessary flow rate and cleaning efficiency for a local recirculation system (room air cleaner). 

Consider a fume control system with an overall hood fume capture efficiency of 60% and a fume cleaning efficiency of 99%. Calculate overall fume control system performance. 

The technology in the fume capture field Is not well developed, and performances of many capture systems are low and typically may be in the 30% to 60% range. There is a paucity of fundamental research and development in the fume capture field. In contrast, hundreds of million of dollars have iteen spent on research and development activities in the gas-cleaning area, which is mature and well developed. It is not uncommon to specify and to measure gas-cleaning equipment performances of over 99.9% colleaion efficiency. As shown in Eq. (13.75), the ovcTall fume control system performance is determined by the product of the capture efficiency and the gas-cleaning efficiency. This equation clearly shows the need to improve the efficiency of capture of the fume at the source in order to obtain significant improvements in the overall fume control system performance. 

Optimum droplet size The idea size of a water droplet in a centrifugal spray scrubber or spray tower to ensure the highest possible cleaning efficiency. 

Where a high cleaning efficiency is required it is sound practice to install a filter of lower performance upstream to trap the larger particles and prolong the life of the more expensive High Efficiency Particulate (HEPA) Air Filter. Two filters of equal merit placed in series will not be materially more efficient than one. 

The frequency of cleaning depends on the nature and concentration of the dust. Typical cleaning intervals vary from about 2 to 15 minutes. However, the cleaning action of the pulse is so effective that the dust layer may be completely removed from the surface of the fabric. Consequently, the fabric itself must serve as the principal filter media for a substantial part of the filtration cycle, which decreases cleaning efficiency. Because of this, woven fabrics are unsuitable for use in these devices and felt-type fabrics are used instead. With felt filters, although the bulk of the dust is still removed, an adequate level of dust collection is provided by the fabric until the dust layer reforms. 

Air scouring is often used with larger filters to improve the cleaning efficiency. The wash cycle is normally a reduced flow backwash in conjunction with air scouring, at the rate of 2 cu ft air/sq ft bed surface area/min, followed by a full-flow rinse with filtered water to resettle the bed. 

Van Asselt, A. J., Van Houwelingen, G., and Te Giffel, M. C. (2002). Monitoring system for improving cleaning efficiency of cleaning-in-place processes in dairy environments. Trans. IChemE 80(Pt. C), 276-280. 

Builders (LD, ADW, HC) Enhance cleaning efficiency of surfactant by reducing water hardness Calcium binding capacity Soil dispersibility Alkalinity Bleach stabilization and anticorrosion capability Zeolite Citrate Polycarboxylate Carbonate Sodium silicates 20-30% 0-4% 0- 5% 5-30% 1- 20%... 

The dual treatment in the Buhler botde-to-bottle process is an important aspect in food safety considerations. The bulk of the contaminants are removed in the extruder. However, the SSP process provides a back-up to remove any residual contaminants, which are now homogeneously distributed in the PET pellets. The cleaning becomes a well-defined and predictable diffusion controlled process, which is defined by pellet diameter, treatment temperature and time. The same parameters also regulate the SSP process. For products with similar reactivity, a known increase in molecular weight during the solid-state process will also provide a known cleaning efficiency. 

Developing Power Systems for the 2U Century - Fuel Cell/ATS Hybrid Systems, U.S. Dept, of Energy, National Energy Technology Center Office of Industrial Technologies, Project facts for Advanced Clean/ Efficient Power Systems, PS031.1099. 

The advantage of this strategy is thus the subsequent trapping of the metalate rearrangement product to provide a clean, efficient, and highly stereoselective route to the trisubstitued alkenes. 

Overhead Cleaning. A dryer is usually the first item on the seed-cotton side. One effect of a dryer is to increase the cleaning efficiency of cleaners. The dryer, though not a cleaner, is regarded as essential to the proper operation of cleaners. Dryers are discussed in more detail in the lint-cleaner section. 

Figure 2. Relationship between cleaning efficiency and combing ratio for three feed rates with constant saw speed (adapted from (37)).

Dryers in cotton gins have an Important effect on cleaning efficiency of lint cleaners and on dust generation in mills (33). 

The major factor that has influenced the development of fuel cells over the last few years is the worldwide concern of the enviromnental consequences of the use of fossil fuels in the production of electricity and for the propulsion of vehicles. Fuel cells seem to be the best solution for clean, efficient and non-hazardous energy. 

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