Cleaning cycle

Durable Antistatic Finishes. The difficulty with nondurable finishes, as far as the consumer is concerned, is that they are water-soluble and thus easily removed by washing. An effective antistatic finish must be durable and capable of withstanding repeated laundering and dry-cleaning cycles. 

FIG. 17-59 Three -compartment hag filter at various stages in the cleaning cycle, W xeel-nhrntor-F iye Inc.)... 

The cleaning cycles are usually controlled by a timing device which deactivates the section being cleaned. The dusts removed during cleaning are collected in a hopper at the bottom of the baghouse and then removed, through an air lock or star valve, to a bin for ultimate disposal. 

Cleaning cycle The total elapsed time from commencing to clean a section of the baghouse to commencing to clean that same section again. 

V = average filtering velocity (cm/s) t = operating time between cleaning cycles (s). 

Conditioned fabric maintains a relatively consistent dust-load deposit following a number of filtration and cleaning cycles. K may be more than 10 times the value of the resistance coefficient for the original clean fabric. If the depth of the dust layer on the fabric is greater than about inch (which corresponds to a fabric dust loading on the order of 0.1 Ibm/ft ), the pressure drop across the fabric, including the dust in the pores, is usually negligible relative to that across the dust layer alone. 

Under controlled conditions (e.g., in the laboratory), the inherent collection efficiency of fabric filters approaches 100 per cent. In actual operation, it is determined by several variables, in particular the properties of the dust to be removed, choice of filter fabric, gas velocity, method of cleaning, and cleaning cycle. Inefficiency usually results from bags that are poorly installed, torn, or stretched from excessive dust loading and excessive pressure drop. 

Figure 5.39. Characterization of the spillover species by photoelectron spectra of the Ols region taken from a 0.02 pm2 spot on the Pt surface (a) The residual O Is spectrum after the cleaning cycles (b) The Ols spectrum measured in 02 atmosphere (pO2=lxI0 6 mbar) (c) The Ols spectrum obtained during electrochemical pumping in vacuum with UWr = 1.1 V. R1 and R2 are the components which are formed by adsorption from the gas phase and by electrochemical pumping. The fitting components of the residual oxygen are shown with dashed lines. Photon energy = 643.2 eV, T 350-400°C.67 Reprinted with permission from Elsevier Science.

Figure 5.39a shows the residual O Is spectrum obtained in ultra-high-vacuum after repeated cleaning cycle at 350-400°C. It is clear that there is a significant amount of residual O on the Pt surface which cannot be removed with conventional cleaning procedures. This by itself suffices to prove the presence of the omnipresent backspillover-formed effective double layer on the vacuum exposed Pt surface. 

Table 4 summarizes the efficiency of membrane filtration as preliminary treatment in the hybrid process to obtain regenerated water for industrial reuse. Working with the adequate cleaning cycle to avoid fouling and to keep a constant flux (10 1 min ) important reduction in suspended solids (90%) and turbidity (60%) of the wastewaters is achieved but there is no significant reduction of other chemical or physical parameters, e.g., conductivity, alkalinity or TDS, or inactivation of E. coli. 

Choosing rigid, base-stable packings that can withstand the rigors of sanitization/cleaning cycles and be turned around relatively quickly... 

It is important to fully understand the physical cleaning cycle and the implications this has on the application of the methodologies. The same cleaning cycle is followed for both the mixing vessels and the intermediate storage vessels. 

Practically wastewater reuse in another cleaning cycle can only be done in steps two, three and four. The water from the first step has a very high contaminant concentration, and reuse of this water in another cleaning operation would not achieve significant wastewater reductions. The wastewater from the other three steps has relatively low concentrations of contaminants and reuse of the water is feasible. In the application of the derived methodologies to the case study, the last three steps were modelled as one processing step. 

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