Recovered air

Use of pulsed air injection rather than continuous air injection may improve performance at many sites. After a system has been operating for a period of time, the concentration of contaminant in the recovered air declines. Continued injection of the same volume of injected air recovers less VOC. Injection of air in a pulsed pattern allows time for reestablishment of a greater concentration gradient toward air channels and a more uniform concentration throughout the contaminant plume area. When the system is resumed, volatilization is again the predominant removal mechanism. 

It is difficult to show a correct balance sheet for this operation. By recycling the air, the need for air filters is eliminated. On the other hand, the recovered air is always saturated with moisture, which would not be the case in most climates for... 

Recovering Air-Sensitive Products from Metal Atom Reactors... 

The use of recovered air is gradually being extended as more and more people accept data that properly purified indoor air can equal the purity of outdoor air, and on occasion can be purer. Certainly this is so in sections where smog and other industrial pollution prevail 13 and in more rural regions sufferers from hay fever and other allergies find recovered air preferable to outside air. 

There is nothing essentially difficult in the design and installation of a carbon purification system. Means must be provided to collect the air from all contaminated spaces and pass this at a proper velocity through adsorbers containing sufficient quantity of a suitable activated carbon. The purified recovered air is then returned to the living quarters. 

If air is used as stripping agent, further treatment of the stripped material will be necessary. The gas might be fed to an incinerator or some attempt made to recover material by use of adsorption. 

Condensable hydrocarbon components are usually removed from gas to avoid liquid drop out in pipelines, or to recover valuable natural gas liquids where there is no facility for gas export. Cooling to ambient conditions can be achieved by air or water heat exchange, or to sub zero temperatures by gas expansion or refrigeration. Many other processes such as compression and absorption also work more efficiently at low temperatures. 

This reaction has been used to recover tin from scrap tinplate.) Tin(IV) chloride is a colourless liquid, which fumes in air due to hydrolysis ... 

Large quantities of sulphur are recovered from petroleum and natural gas. Naturally occurring hydrogen sulphide, HjS, and that produced in the cracking and catalytic hydrogenation of petroleum is first removed by absorption and the regenerated gas is converted to sulphur by partial combustion with air, the overall reaction being,... 

The above method has now been largely replaced by a newer process, in which the substance 2-ethylanthraquinone is reduced by hydrogen in presence of a catalyst to 2-ethylanthraquinol when this substance is oxidised by air, hydrogen peroxide is formed and the original anthraquinone is recovered ... 

If a liquid which is being heated in a beaker or a conical flask catches fire, it is frequently sufficient to turn off the gas (or other source of heating) below and then at once to stretch a clean duster tightly over the mouth of the vessel. The fire quickly dies out from lack of air, and the (probably valuable) solution is recovered unharmed. 

Mix 30 g. (38 ml.) of iaopropyl alcohol with 450 g. (265 ml.) of constant boiling point hydriodic acid (57 per cent.) (Section 11,49,2) in a 500 ml. distilling flask, attach a condenser for downward distillation, and distil slowly (1-2 drops per second) from an air bath (compare Fig. II, 5, 3). When about half the liquid has passed over, stop the distillation. Separate the lower layer of crude iodide (80 g.). Redistil the aqueous layer and thus recover a further 5 g. of iodide from the flrst quarter of the distillate (1). Wash the combined iodides with an equal volume of concentrated hydrochloric acid, then, successively, with water, 5 per cent, sodium carbonate solution, and water. Dry with anhydrous calcium chloride and distil. The isopropyl iodide distils constantly at 89°. 

The filtrates from the decomposition of the brucine salts with dilute hydrochloride acid should be carefully preserved. The brucine Is recovered by the addition of an excess of dilute ammonia solution (1 4) if the solution becomes turbid before all the ammonia solution is added, introduce a little alcohol until the solution becomes clear. After several hours in an open beaker, filter oft the brucine, wash it well with cold water and dry it in the air. 

Method 1. Dissolve 76 g. of thiourea in 200 ml. of warm water in a 750 ml. or 1 litre round-bottomed flask. Dilute the solution with 135 ml. of rectified spirit and add 126-5 g. of benzyl chloride. Heat the mixture under reflux on a water bath until the benzyl chloride dissolves (about 15 minutes) and for a further 30 minutes taking care that the mixture is well shaken from time to time. Cool the mixture in ice there is a tendency to supersaturation so that it is advisable to stir (or shake) the cold solution vigorously, when the substance crystallises suddenly. Filter off the sohd at the pump. Evaporate the filtrate to about half bulk in order to recover a further small quantity of product. Dry the compound upon filter paper in the air. The yield of hydrochloric acid filter off the sohd which separates on cooling. Concentrate the filtrate to recover a further small quantity. The yield of recrystalhsed salt, m.p. 175° is 185 g. some of the dimorphic form, m.p. 150°, may also separate. 

Inhalation should be avoided. A group of six rats that were exposed to 64,000 ppm of methyl vinyl ether in air for 4 h were anesthetized. AH recovered and appeared normal after 72 h. One died after 96 h. The others survived the 2-week observation period without noticeable effect. 

Steps. Thermal-swing cycles have at least two steps, adsorption and heating. A cooling step is also normally used after the heating step. A portion of the feed or product stream can be utilized for heating, or an independent fluid can be used. Easily condensable contaminants may be regenerated with noncondensable gases and recovered by condensation. Water-iminiscible solvents are stripped with steam, which may be condensed and separated from the solvent by decantation. Fuel and/or air may be used when the impurities are to be burned or incinerated. 

Secondary alcohols (C q—for surfactant iatermediates are produced by hydrolysis of secondary alkyl borate or boroxiae esters formed when paraffin hydrocarbons are air-oxidized ia the presence of boric acid [10043-35-3] (19,20). Union Carbide Corporation operated a plant ia the United States from 1964 until 1977. A plant built by Nippon Shokubai (Japan Catalytic Chemical) ia 1972 ia Kawasaki, Japan was expanded to 30,000 t/yr capacity ia 1980 (20). The process has been operated iadustriaHy ia the USSR siace 1959 (21). Also, predominantiy primary alcohols are produced ia large volumes ia the USSR by reduction of fatty acids, or their methyl esters, from permanganate-catalyzed air oxidation of paraffin hydrocarbons (22). The paraffin oxidation is carried out ia the temperature range 150—180°C at a paraffin conversion generally below 20% to a mixture of trialkyl borate, (RO)2B, and trialkyl boroxiae, (ROBO). Unconverted paraffin is separated from the product mixture by flash distillation. After hydrolysis of residual borate esters, the boric acid is recovered for recycle and the alcohols are purified by washing and distillation (19,20). 

The principal disadvantage of absorption bleaching is the problem of disposal of spent bleaching clay. Oil absorbed on the clay is exposed to air and is generally too oxidized to recover. Furthermore, spontaneous combustion of the oil-laden clay is a possibiUty in a landfill. Incineration of the spent clay along with sohd municipal waste to recover otherwise wasted energy is an attractive possibiUty. 

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