Mechanical rapping

Mechanical rapping The mechanism that vibrates electrostatic precipitators or bag filters in order to remove the dust burden. 

An emerging newer boiler design is to follow the tail water-tube-walled combustion chamber by a long superheater, boiler convection section and economizer. This is called the dacha boiler (after the female dashund dog) because of its extended horizontal configuration with several flyash hoppers. This permits tube cleaning by mechanical rapping and eases the labor of tube replacement when needed. 

Excessive us of high-pressure steam soot blowers is a common source of tube erosion-corrosion. Other boiler cleaning methods less threating to boiler tubes are available such as mechanical rapping, shot cleaning, and compressed air soot blowing. 

In a dry precipitator to ensure that the collection process is continuous, after a period of time the collector electrodes are generally mechanically rapped to remove the deposited material. This time aspect, together with the frequency and intensity of the rapping, is important to minimize rapping re-entrainment and hence maximize collection efficiency. In wet precipitators, the particles are deposited on a film of running water or removed by flushing, while for mist precipitators, the droplets are usually selfdraining. 

Electrostatic precipitator Batch process load electrodes, then clean via wet spray or mechanical rapping. For particle conductivity between 10 and 0.01 reciprocal ohm m. Prefer negatively charged configuration. May need to adjust conditions to get particle conductivity into acceptable range. For particles >10 pm, use 38-m plate area per m /s gas flow 1 pm, use 100-m plate area per m /s gas flow 0.4 pm, use 120-m plate area per mVs gas flow. 

The process gases enter a forced-circulation-type waste heat boiler at 800-1000 °C. Several changes have been made to the mechanical rapping equipment and cooling pipe bundles of the boiler to improve the performance and maintenance access. The gases exit the waste heat boilers at a temperature of 300-350 °C and pass through the hot cyclone separators and electrostatic precipitators into the mercury removal towers. Two electrostatic precipitators are installed simultaneously in both lines to ensure continuous processing. 

Electrostatic precipitator Batch process load electrodes then clean via wet spray or mechanical rapping. For particle conductivity between 10" and 0.01 m. Prefer negatively charged configuration. May need to adjust conditions to get particle conductivity into acceptable range. 

D. s-Aaetyl-2(3B)-oxaaolone. The crude mixture of 3-acety1 4- and 5-chloro-2-oxazolidinone from Step C is placed in a 2-L, three-necked flask equipped with a thermometer, sealed mechanical stirrer, and gas discharge tube. The material is heated to 120°C with stirring, and the temperature is then slowly increased to 150 C and held there until the evolution of gas ceases (Note 10). The cooled, black reaction mixture is distilled at 20 nm. The fractions boiling up to 150°C are collected and redistilled through a 50-cm X 3-cm Vigreux column fitted with a variable take-off head. There is obtained 140-172 g (55-68%) of product, bp 108-112°C (24 mm), which solidifies, rap 35-37°C (Note 11). 

Electrodes in the center of the flow lane are maintained at high voltage and generate the electrical field that forces the particles to the collector walls. In dry ESPs, the collectors are knocked, or "rapped," by various mechanical means to dislodge the particulate, which slides downward into a hopper where they are collected. 

A recent study shows that the (RAP)IrH2 complex can catalytically convert alkane to alkene at temperatures ranging from 150 to 250 °C through an acceptorless, thermal reaction. Three suggested reaction mechanisms, associative (A), dissociative (D) and interchange (I) will... 

Semiclosed systems for handling solids often involve the use of big bags or tote bins. In these systems the solid is shipped in alarge (>1 t) container which is then lifted into place over a closed hopper or feed mechanism and a sealed connection is made. It is sometimes necessary to rap or agitate the big container to keep the solid moving and this action can result in deterioration or damage to the container or seals with consequent leaks. Also, there is some release of solids when containers are connected or disconnected as well as opportunities for dust generation. 

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