Atmospheric drier pressure

An installation for the recovery of solvent (chiefly alcohol) by condensation is connected with a drier operating at a reduced pressure. The installation works at atmospheric pressure. It consists of two condensers cooled with cold water in which ether and alcohol (containing some water and ether) are condensed. From 10 to 25 kg of 95% alcohol is recovered per 100 kg of powder according to the season (more in winter). 

Drum driers can operate either at atmospheric pressure or under vacuum... 

Venus upper atmosphere is even drier than the lower atmosphere, and the average water-vapor mixing ratio above the clouds is only a few ppmv. The very low H2O mixing ratios were hard to explain until it was realized that Venus clouds are 75% sulfuric acid, which is a powerful drying agent. When dissolved in the acid, most of the water reacts with H2SO4 to form hydronium (HaO ) and bisulfate (HSO4) ions. As a result, the concentrations of free H2O in the acid solution and in the vapor over the acid are extremely low. The partial pressure of water at Venus cloud tops is lower than that over water ice at the same temperature. Thus, the clouds are responsible for the extreme dryness of Venus upper atmosphere, and play an important role in the photochemical stability of Venus atmosphere (see Section 1.19.3.3). 

Agitated batch driers consist of a jacketed cylindrical vessel with agitator blades designed to scrape the bottom and walls. They may operate at atmospheric pressure or under vacuum. Pasty materials that could not be handled in tumbling or fluidized-bed driers, may be successfully dried at rates higher than can be achieved in an oven. 

The dampness or dryness of air depends upon the pressure of the water vapour present compared with the maximum for the atmospheric temperature. The nearer the actual pressure of the water vapour present approaches to the maximum, the damper the air is, and, on the other hand, the farther apart the two pressures are the drier it is. When the water exerts the maximum vapour pressure for the atmospheric temperature and no more can be taken up, the air is said to be saturated. When damp textile materials are exposed to saturated air they cannot lose any moisture, but if they are in a dry state they can absorb water from the air. 

Carbon disulfide, CS2, used as a solvent in a chemical plant, is evaporated fi om the product in a drier to an inert gas (essentially N2) in order to avoid an explosion hazard. The vapor-N2 mixture is to be scrabbed with an absorbent oil, which will be subsequently steam stripped to recover the CS2. The CS2-N2 mixture has a partial pressure of CS2 equal to 50 mmHg at 24 °C (75 °F) and is to be blown into the absorber at essentially standard atmospheric pressure at the expected flowrate of... 

A feature of some feeder operations is that the product is delivered to a region that has a slightly different pressure to that in the supply zone. Other feeders deliver into ambient conditions that are unfavourable to sustained exposure of the feeder mechanism or to the product. Common examples are feeding from dust filters, into reaction vessels that have vapour-laden atmospheres and into the high-temperature atmospheres of kilns and driers. Discharge end bearings and seals of conventional screw feeders are vulnerable to such adverse atmospheric conditions. Exposed contact surtaces suffer condensation from steamy environments, and... 

Method of use. The chamber is evacuated and then warmed to 40 °C with hot air or steam to give an RH of 25-50%. Ethylene oxide is then injected into the chamber to a concentration of 400-1000 mg per litre and sterilising conditions maintained for 4—8 hours. The freeze-drier is then returned to atmospheric pressure and the ethylene oxide vented from the drier. An explosion-proof mixture of 60% ethylene oxide and 40% methyl bromide has been used for decontamination. Ethylene oxide has been more widely used in the USA than in the UK for sterilising freeze-driers. 

Dry and wet bulb temperatures can be measured with an aspirated or whirling Itygro-meter, and using a chart, the vapour pressure of the water in the atmosphere can be read off using the dry and wet bulb values. A wet bulb thermometer has the mercury in the bulb surrounded by wet cloth - the drier the air, the faster the evaporation of water and the lower the wet bulb temperature. 

In this type of system the gas flows from the high pressure cylinders through a pressure regulator to drier, filters, etc. and then to the cooler head itself where it expands with the cool gas being vented to the ambient atmosphere. 

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