Air blowing

Another variation of the string discharge is the use of a thick plastic belt which is perforated by conical openings. The dmm is covered with filter cloth and the belt covers the cloth for the filtration and dewatering operations. The soHds fill the perforations in the belt and then leave the dmm with the belt to be discharged by air blow as pellets. This is an effective way of pelletising coarse mineral ores. 

Brines. About 65% of the iodine consumed in the world comes from brines processed in Japan, the United States, and the former Soviet Union (see Chemicals frombrine). The predorninant production process for iodine from brines is the blow-out process, which was first used in Japan. Iodine is present in brines as iodide, and its concentration varies from about 10 to 150 ppm. As shown in Figure 3, the recovery process can be divided into brine clean-up, iodide oxidation to iodine followed by air blowing out and recovery, and iodine finishing. 

The I2 formed stays in solution, exerting a certain vapor pressure, and is extracted from the brine in a countercurrent air blow-out process. The extracted brine leaves the extraction tower and is discarded or reinjected into the wells to avoid sinking of the soil. The iodine-loaded air is then submitted to a cocurrent desorption process by means of an acidic iodide solution to which SO2 is added. By this solution the iodine is reduced to iodide by the following reaction ... 

Dryers. A drying operation (see Drying agents) needs to be viewed as both a separation and a heat-exchange step. When it is seen as a separation, the obvious perspective is to cut down the required work. This is accompHshed by mechanically squeezing out the water. The objective is to cut the moisture in the feed to the thermal operation to less than 10%. In terms of hardware, this requires centrifuges and filters, and may involve mechanical expression or a compressed air blow. In terms of process, it means big crystals. 

Sulfur dioxide concentrations in oleum ate rarely specified or measured, but typical values are considerably higher than in acids of <99 wt % concentrations. This occurs because oleum is produced at relatively low temperatures in the presence of appreciable SO2 in the gas phase, thus lea ding to high solubihty. It is not possible to strip SO2 from oleums by air blowing, a technique that is ftequentiy appHed to product acids of <99% concentration. 

In the CIS pitch coke is made by carbonizing a hard coke-oven pitch in modified coke ovens. The hard pitch has an R-and-B softening point of 140—150°C and is made by air-blowing a mixture of medium-soft pitch and recycled coking oils. This feedstock is charged in the molten state over a period of 5 h and coked for 17—18 h at 1250—1300°C. The coke yield is 70%. Oils, which are recycled, amount to 20% by weight of the pitch fed. The gas yield... 

Table 4. Fractional Changes in Hardness of Asphalf upon Air-Blowing...

Batch Process. In the batch process (Fig. 5), the feedstock is preheated in a tube furnace or heater placed between the feedstock storage and the blowing vessel. The air supply is provided by a variety of blowers or compressors and a vertical-tower vessel is preferable for air-blowing. Knockout dmms, water scmbbers, incinerators, furnaces, and catalytic burning units have been used for fume disposal (32). Steam is used for safety and to ensure positive fume flow to the incinerator. 

Table 5. Air-Blowing of Fluxes With and Without Ferric Chloride and Phosphorus Pentoxide Catalysts...

If the cake is to be washed, the slurry heel can be blown from the filter and wash liquor can be introduced to refill the shell. If the cake tends to crack during air blowing, it may be necessaiy to displace the shiny heel with wash gradually so as never to allow the cake to diy. Upon the completion of filtration and washing, the cake is discharged by one of several methods, depending on the sheU and leaf configuration. 

Figure 31.9 A typical arrangement illustrating drying of enclosure through hot air blowing...

Inspection of electrical wiring if there is any (such as for space heaters, cold or hot air blowing, enclosure pressurizing or any other protective circuit)... 

Hydrocarbons Air blowing, barometric condensers, blind changing, blowdown... 

Identify and provide warnings Air blow lines Isolate and purge Fuel Gas... 

Combined systems extraction with additional supply air) It is advantageous to increase the range of the capture system by an additional supply system. The supply air blows the contaminated air toward the capture openings (see Section 10.4.6). 

For a push-pull system, the source is usually an open surface tank and the airflow acts as a horizontal curtain above the surface. In this case, the person could be anywhere as long as the system works as intended and the curtain is not broken. The curtain will be broken when parts or material are lifted out of or placed into the bath and the contaminants could be spread either through convection or because the supply air blows against the material or part. 

The function of the nebuliser is to produce a mist or aerosol of the test solution. The solution to be nebulised is drawn up a capillary tube by the Venturi action of a jet of air blowing across the top of the capillary a gas flow at high pressure is necessary in order to produce a fine aerosol. 

Ammonia/hydrazine passivator An alkaline hydrazine solution (pH over 9.0, 0.5% N2H2) provides a useful passivator. If there are concerns over the use of hydrazine, diethylhydroxylamine (DEHA), erythorbate, or carbohydrazide may be substituted. Air blowing improves the passivating effect. 

C15-0142. Red and white Ping-Pong balls with small Velcro patches are placed in an air-blowing machine like the ones used to scramble numbered balls in lottery drawings on TV. If red and white balls collide at the Velcro points, they stick together. When 20 red and 10 white balls are put in the machine, 4 pairs form after 2 minutes of blowing, (a) If 10 balls of each color had been placed in the machine, how many pairs would form under the same conditions (b) What if there were 20 red and 15 white balls (c) What if there were 10 red and 20 white balls (d) What if the machine had been crammed with 40 red and 20 white balls (e) Explain why the rates change with the numbers of balls. 

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