Free moisture, defined

Consider the drying of a wet solid under fixed drying conditions. In the most general cases, after an initial period of adjustment, the dry-basis moisture content X decreases linearly with time t following the start of the evaporation. This is followed by a nonlinear decrease in X with t nntil, after a very long time, the solid reaches its equilibrium moisture content X and drying stops. In terms of free moisture content, defined as... 

In order to determine whether a simple relationship exists in the falling-rate period, the unaccomplished moisture change, defined as ratio of free moisture in the solid at time 0 to total free moisture present at start of the falling-rate period (W - )/(W - W ), is plot-... 

The water in coal is bound in different forms to its constituents. It can be divided into three types (1) Free moisture, also referred to as external moisture, superficial moisture, or the primary moisture fraction, which is present in large cracks and capillaries. Water bound in this way retains its normal physical properties. (2) Inherent moisture, also referred to as internal moisture or the secondary moisture fraction, whose vapor pressure is lower, since it is absorbed within the pore structure of the coal. (3) Water of constitution, which is mainly combined with mineral matter normally present in coal. This water is generally driven off only at temperatures higher than those normally used for the determination of moisture content. Standard methods do not make use of these terms and define (1) the total moisture content of a coal and (2) the moisture content of the coal analysis sample. Total moisture determination must be made over the sample as received in the laboratory, in an air-proof recipient. The determination consists in drying in an oven at 105 °C till constant weight. Its value is of huge interest both in international and domestic coal trade (ISO 589, ASTM D3173). 

In another method an approximate straight line from the critical free moisture content to the origin at zero free moisture was assumed. Here the rate of drying was assumed to be a linear function of the free moisture content. The rate of drying R is defined by Eq. (9.5-3). 

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

If water losses from the surrounding area are a major component of the total evaporative losses of the pond, then soil moisture conditions will be expected to be high. Under non-limiting soil moisture conditions vegetative moisture losses are often defined as "potential" losses. Evaporative losses in this case would not be expected to differ greatly from free water evaporation. The literature recommends... 

Moisture in coal takes three forms (l)free or adherent moisture, essentially surface water (2) physically bound or inherent moisture (thai moisture held by vapor pressure and other physical processes) and (3) chemically bound water (water of hydration or combined" water). The ASTM defines total moisture as a loss in weight in an air atmosphere under rigidly controlled conditions of temperature, time, and air flow. Total moisture represents a measurement of all water not chemically combined. Total moisture is determined by a two-slep procedure, involving air-drying for removal of surface moisture from the gross sample, division and reduction of Ihc gross sample, and determination of residual moisture in the prepared sample. An algebraic calculation is used to obtain the total moisture value. 

Bituminous coal is a dense coal, usually black, sometimes dark brown, often with well-defined bands of bright and dull material, used primarily as fuel in steam-electric power generation, with substantial quantities also used for heat and power applications in manufacturing and to make coke. The moisture content of bituminous coal is usually less than 20% by weight. The heat content of bituminous coal ranges from 21 to 30 million Btu/ton on a moist, mineral-matter-free basis. 

Siloxanolate Catalysts. The initial step for the study of the kinetics of base-catalyzed siloxane equilibration reactions was the preparation of a number of well-defined siloxanolate catalysts. The catalysts were prepared separately, prior to the equilibration reactions, so that a homogeneous moisture-free system with a known concentration of active centers might be obtained. The catalysts studied included potassium, tetramethylammonium, and tetrabutylphosphonium siloxanolate. 

A relationship between peroxide value and anisidine number that is used to measure the rancidity level of fats and oils. It is defined as (2 X PV) + AN. It reflects total oxidation to date. Considered an impurity. High levels of moisture in an oil can lead to deterioration in storage. Soap can be formed when moisture is present in the crude oil and reacts with the free fatty acids and a catalyst (alkali ion), or it can result from incomplete removal of soap from washed refined oil. 

Note Data adapted from Ref. 67 are percent moisture-free wood. Data adapted from Ref. 66 are not defined in the English abstract and table. 

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