Liquid equilibrium moisture content

Fiber-saturation point is the moisture content of cellular materials (e.g., wood) at which the cell walls are completely saturated while the cavities are liquid-free. It may be defined as the equilibrium moisture content as the humidity of the surrounding atmosphere approaches saturation. 

Capillary Flow Moisture which is held in the interstices of solids, as liquid on the surface, or as free moisture in cell cavities, moves by gravity and capillarity, provided that passageways for continuous flow are present. In drying, liquid flow resulting from capillarity applies to liquids not held in solution and to all moisture above the fiber-saturation point, as in textiles, paper, and leather, and to all moisture above the equilibrium moisture content at atmospheric saturations, as in fine powders and granular solids, such as paint pigments, minerals, clays, soil, and sand. 

Liquid Diffusion The movement of liquids by diffusion in sohds is restricted to the equilibrium moisture content below the point of atmospheric saturation and to systems in which moisture and solid are mutually soluble. The first class applies to the last stages in the drying of clays, starches, flour, textiles, paper, and wood the second class includes the drying of soaps, glues, gelatins, and pastes. 

The drying of wet granular beds containing non-porous particles, which are insoluble in the wetting liquid, has been extensively studied. The operation is presented as the relation of moisture content and time of drying in Fig. 5A. It should be noted that the equilibrium moisture content is approached slowly. A protracted period may be required for the removal of water just above the equilibrium value. This is not justified if a small amount of water can be tolerated in further procession establishing realistic drying requirements. 

Moisture content at 20°C and 52% relative humidity, the equilibrium moisture content of ethyl oleate is 0.08%. Solubility miscible with chloroform, ethanol (95%), ether, fixed oils, liquid paraffin, and most other organic solvents practically insoluble in water. 

Free moisture. This is the liquid in excess of the equilibrium moisture content for the specific temperature and humidity condition of the dryer. Practically, it is the liquid content removable at a given temperature and humidity. 

Since many chemicals are processed wet and sold dry, one of the more common manufacturing steps is a drying operation (13) which involves removal of a liquid from a solid by vaporization of the liquid. Although the only basic requirement in drying is that the vapor pressure of the liquid to be evaporated be higher than its partial pressure in the gas stream, the design and operation of dryers represents a complex problem in heat transfer, fluid flow, and mass transfer. In addition to the effect of such external conditions as temperature, humidity, air flow, and state of subdivision on drying rate, the effect of internal conditions of liquid diffusion, capillary flow, equilibrium moisture content, and heat sensitivity must be considered. 

The moisture contained in a wet solid or liquid solution exerts a vapor pressure to an extent depending upon the nature of moisture, the nature of solid, and the temperature. A wet solid exposed to a continuous supply of fresh gas continues to lose moisture until the vapor pressure of the moisture in the solid is equal to the partial pressure of the vapor in the gas. The solid and gas are then said to be in equilibrium, and the moisture content of the solid is called the equilibrium moisture content under the prevailing conditions. Further exposure to this air for indefinitely long periods will not bring about any additional loss of moisture. The moisture content in the solid could be reduced further by exposing it to air of lower relative humidity. Solids can best be classified as follows [12] ... 

Under these conditions, bed density is 500 kg/m and equilibrium moisture content is zero. Specific heat of the dry solids and liquid water are 1.0 and 4.2 kJ/kg°C, respectively. 

Stabilizing of the liquid moisture content for pure lysine an increase in air humidity from 50% to 60% increases by 1.5 times the equilibrium moisture content. If the relative humidity approaches 80%, the equi-... 

The most common additive to lignocellulosic composite panels other than resin is wax. Even small amounts 0.5-1%, act to retard the rate of liquid water pick up. This is important when the composite is exposed to wet environments for short periods of time. However, wax addition has little effect on long-term equilibrium moisture content. Flame retardants, biocides, and dimensional stabilisers are also added to panel products [4]. 

The equilibrium moisture content in an adhesive is dependent on the relative humidity. Henry s law states that at constant temperature the amount of a given gas dissolved in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid. This can be extended to molecular diffusion of a fluid in a polymer as the equilibrium quantity of a diluent within a polymer, c is proportional to the environmental activity of the diluent, aj,. 

Besides the fact that column equilibrium is not so readily disturbed by external effects like temperature and the moisture content of the eluent, bonded phases possess some additional advantages over conventional phases or those coated with a stationary liquid. These are ... 

Hydrated Zeolites. The zeolitic pellets are hydrated by equilibration at atmospheric moisture content. The cell is immersed in liquid air, and a minimum equilibrium temperature of — 120°C was obtained. At that temperature the conductivity and capacity of the samples are measured over the frequency range 200-107 Hz. After eliminating the cooling liquid, the temperature rises slowly (0.5°C/min). Measurements are performed continuously in the same frequency range during the. temperature rise up to room temperature. The results are near-equilibrium values, and the errors are assumed to be the same over the complete temperature range. The same procedure was applied by Mamy for dielectric measurements on montmorillonite 11). 

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