Pulse cleaning cycle

Each filter has demonstrated the capacity to filter the full brine flow of 195 m3 h 1. The pressure drop through the filter medium is measured and monitored continuously. Typically, it is nearly constant over a 2-h filtration at 195 m3 h 1. Back-pulse cleaning restores the initial pressure drop from cycle to cycle, with only a slow increase over time. After 12 months running time, the initial pressure drop at the beginning of the filter cycle had increased by 0.6 bar. The filter membranes were chemically cleaned with 5 % hydrochloric acid. After a cleaning time of 2 h the filter was started again and the pressure drop was less than 0.1 bar greater than that of new filter socks. 

The operation cycle is a stepwise process. The essential steps are filling the vessel, filtration (service), back-pulse (cleaning), cake settling, and sludge discharge. In practice, the steps will vary in length from application to application, but all working operation sequences include these basic steps, which will be addressed in order. 

Three bulk (candle pieces) exposures at 850°C with and without water vapour were completed to cause microstructural changes in order to find out their possible role in changes in mechanical properties of materials. The coding and conditions of the bulk exposures are described in Table 1. The water vapour pressure in the exposures corresponded to the atmospheric pressure. Thermal cycling between 150 and 400 °C was done without water vapour in order to see the effect of thermal shock caused by back pulse cleaning and the phase transformation of silica. 

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 sei ve as the principal filter medium for at least a substantial part of the filtration cycle. Woven fabrics are unsuitable for such service, and felts of various types must be used. The bulk of the dust is still removed in a surface layer, but the felt ensures that an adequate collection efficiency is maintained until the dust layer has formed. 

Pulse-jet cleaning (above) uses a controlled blast of compressed air from the primary into the secondary nozzle, which is magnified by induced air being drawn into the bag. The sudden release of air causes the bag to expand fully, throwing the dust from the outer surface. Dislodged dust falls into the collection hopper. At right, types of duty cycles... 

Figure 13 Timing diagram for the clean HMBC experiment with an initial second-order and terminal adiabatic low-pass 7-filter.42,43 The recommended delays for the filters are the same than for a third-order low-pass J filter. <5 and 8 are gradient delays, where 8 — <5 + accounts for the delay of the first point in the 13C dimension. The integral over each gradient pulse G, is H/2yc times the integral over gradient G2 in order to achieve coherence selection. The recommended phase cycle is c/)n = x, x, x, x 3 — 4(x), 4(y), 4( x), 4(—y) with the receiver phase c/)REC = x, x.

Figure 6. Schematical representation of the moving-reaction-front model. A pulsing CO over O-precovered platinum. B Pulsing CO (excess) and Oj alternately over initial O-covered platinum. Gray O-covered White CO covered or clean platinum. The numbers denote the pulse cycle number.

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