Dehumidify

Carbon dioxide is used to increase the natural CO2 content of the beer and as counterpressure in tanks and filling machines. It must be free of water and any aroma. The consumption is 0—10 g/L of beer produced. In major breweries, carbon dioxide is bought in bulk, and in many breweries it is common practice to coUect the surplus CO2 from the fermentors to clean, dehumidify, and compress in a local CO2 plant which is easily automated. 

Installation of heat-exchange equipment to precool and dehumidify the feed gas to an absorber also deserves consideration in order to take advantage of the cooling effects created by vaporization of solvent in the lower sections of the tower. 

Figure 20-87 shows a typical production-size batch fluid-bed granulator. The air-handling unit dehumidifies and heats the inlet air. Heated fluidization air enters the processing zone through a distribu-... 

Gas absorption, sembbing desorption, stripping Humidifieation and water eooling Dehumidifieation and air eonditioning Drying of solids, solutions/slumes... 

Anhydrous An anhydrous material does not contain any water molecules. Many substances occur naturally as hydrates, compounds that have a specific number of water molecules attached to them. This water can often be removed by heating and/or vacuum to give the anhydrous material. Anhydrous materials can absorb water from their surroundings and find use as dessicants. Examples include those packets of silica gel you find in some consumer goods, as well as dehumidifying sachets used in clothes closets. When an anhydrous material reacts with water, this could release a large amount of heat, possibly leading to a heat or pressure buildup that could result in an explosion. 

Cooling and dehumidifying Decreased moisture content and specific volume, dry-and wet-bulb temperature, specific enthalpy, and % saturation Chilled-w arer wa.sher... 

Certain chemicals (sorbents) have the ability to absorb moisture from a gas they may be either solid or liquid. Performance of a chemical dehumidifi cation device depends on the sorbent used. The sorbent must t>e able to attract and remove the sorbate, such as water, from the gas stream, Stirbems absorb water on the surface of the material by adsorption or by chemically combining with water (absorption). If the unit is regenerative, the process is reversible, allowing water to be removed. This is achieved by a sorbent such as silica gel, alumina gel, activated alumina, lithium chloride salt, lithium chloride solution, glycol solution, or molecular sieves. In the case of nonregenerative equipment, hygroscopic salts such as calcium chloride, urea, or sodium chloride are used. 

If the vapor pressure of the sorbent in its active state is below that of the gas being dehumidified, moisture is absorbed from the gas stream. As the process continues, the sorbent liecomes diluted due to the moisture increase. See Fig, 9,17,... 

The selection of humidifiers or dehumidifiers must not be taken lightly, as many design factors have to be considered to ensure economic owning and operating costs. 

The influence of airflows from ventilating systems must also be considered. Processes using mediums of different physical qualities when mixed will have separation into different layers. Transmission of energy between molecules in flowing mediums takes place in the direction of the velocity. This strengthens the separation into parallel layers. The level of fluid in containers and tanks is due to stratification of horizontal temperature layers, while airflow after batteries, heat-recovery systems, and humidifiers or dehumidifiers will separate into parallel layers. 

FIGURE 9.57 A ventilation system for controlling the air temperature by humidifying and dehumidifying the air. 

A workbench makes use of a local air supply in conjunction with exhaust air to ensure good control of the contaminants generated on a bench process. The local exhaust removes the contaminants, while the local supply air protects the operator and/or the products against airborne contaminants. The local supply air improves the thermal environmental conditions by introducing cool dehumidified air in a hot environment. This ensures that the operator s thermal comfort is maintained in areas of high temperature, where full air conditioning of the entire workspace is nor economically feasible. 

HVAC The heating, ventilation and air conditioning system that circulates and delivers filtered, humidified or dehumidified, and cooled or warmed air to the interior of a building. 

Human activity such as coughing and sneezing wet or moist walls, ceilings, carpets, and furniture poorly maintained humidifiers, dehumidifiers, and air conditioners bedding household pets. 

HUMIDIFYING A DEHUMIDIFYING with no change in dry bulb is represented by a vertical line between the limits of the process. 

R-401B (22/152a/124) MP66 AlliedSignal DuPont CFC-12 R-500 Blend (moderate glide) Alkylbenzene or polyol ester Alkylbenzene or polyol ester or in some cases mineral oiF Transport Refrigeration retrofits Retrofits including air conditioners dehumidifiers Close to CFC-12. Use where evap. temperature below -10 F. 

Humidity (condensation) Dehumidifiers, insulation, ventilation, warmed surfaces... 

Dehumidifiers, in which air is passed first over the evaporator to remove moisture, and then over the condenser to re-heat and lower the humidity (see Figure 29.1). 

Figure 24.9 Cooling and dehumidifying coil - process line...

Example 24.11 If air is to he cooled and dehumidified, it may he found that the process line joining the inlet and outlet conditions does not meet the saturation line, e.g. in cooling air from 24°C dry hulh, 45% saturation, to 19°C dry hulh, 50% saturation, the process line shows this to he impossible in one step (Figure 24.11). The air must first be cooled and dehumidified to reach the right moisture level of 0.006 9 kg/kg and then re-heated to get it back to 19°C. 

Figure 24.11 Cooling with dehumidifying, followed by re-heat process lines...

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