External moisture

External moisture that is not bonded to a particle of coal or other fuel. External moisture will ice in cold weather and lump fuel together in a solid mass. Where this occurs, thaw sheds may be used to heat the mass before further transport or use. 

During drying opn, samples of proplnt are sent to the lab to det if the required external moisture and volatile solvent contents have been reached. The desired external moist content for air-dried proplnts varies inversely as the size of the grain from ca 0.1 to 1.0%, while the total volatile content of the dried proplnt may vary from ca 3.5 to 7.5%, depending upon the web thickness - the heavier web proplnts having the greater solvent contents... 

A sample of water-dried powder was exposed to an atmosphere practically saturated with water vapor. Portions were removed each day one part was fired in the gun, and another part was analyzed for total volatile matter (TV) and for volatile matter driven off by an hour s heating at 100° (external moisture, EM). 

There appears really to be no method by which true external moisture may be determined, that is, no method by which only the surface moisture is removed in such fashion that the residual solvent in the powder is found to be the same both before and after the powder has been allowed to take up moisture. Samples of powder were taken and residual solvent was determined by the several methods indicated in the next table. The samples were exposed 2 weeks to an atmosphere practically saturated with water vapor, and residual solvent was again determined as before. The surprising result was secured in every case, as indicated, that the amount of residual solvent was less after the powder had been exposed to the moist atmosphere than it was before it had been exposed. Yet the powder had taken up large quantities of moisture during the exposure. It is clear that the exposure to the moist atmosphere had made the volatile matter of the interior of the grains more accessible to desiccating influ-... 

Method of Determining External Moisture and Residual Solvent Exposure to Water Residual solvent Exposure to Alcohol Residual solvent ... 

The Dry Furnace is a vessel containing the matter, the vessel in question not being put into water. The dissolution is effected by means of an external moisture. It takes place in a bladder and sand melting box. 

Drying of seed may be performed at room temperature with no additional equipment, or with hot-air dryer. The first stage of drying consists of the removal of external moisture from the fresh seeds. Internal water diffuses outward, evaporating in the external part of seeds. After a certain time, seeds reach a hygroscopic equilibrium state at which the moisture content remains constant. The equilibrium depends on ambient temperature and relative humidity of the surrounding air. Figure 15 is a representation of these values for different temperatures 10°C, 25°C, and 40°C [based on Mazza and Jayas (51)]. 

The stability and shelf-life of effervescent powders are essentially assured by protection against external moisture. Single-dose sachets are manufactured with suitable complexes to prevent premature reaction caused by external moisture or excess internal moisture from the granulation process. Special stability studies under different conditions are required for these powders. The dissolution time must be less than 3 min this is an index of stability. 

Another way of breaking and reforming Cr-surface bonds is hydrolysis, as is also shown in Scheme 3. Hydrolysis of Si-O-Cr bonds could occur though contact with external moisture or neighboring silanol groups. 

A second example concerns packaging in the food industry. The effectiveness of thin transparent wrapping (polymers) in protecting food depends on their ability to prevent the spread of pathogenic microorganisms, external moisture causing mold, and oxygen responsible for the oxidation of food. 

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). 

Some products for example have to be protected from light. Protection from external moisture, oxygen, light, micro-organisms, particles, fracture and deformation may be necessary. The medicinal product should not lose moisture or interact with the container in a way that would adversely affect the quality of the product. 

After expanding through the high-pressure turbine, the exhaust steam is wet and at saturation temperature. It is routed through two external moisture separator-reheater vessels where it is dried and superheated.. The external moisture separators reduce the moisture content of the high-pressure exhaust steam from approximately lOto 13 percent at the rated load to 0.5 percent or less moisture. It uses multiple vane chevron banks for the moisture removal. The moisture removed drains to a moisture-separator drain tank, from where it is pumped to the deaerator, which is at similar pressure to the steam entering the low pressure turbine. 

A package is made of three ears of com by placing them on a Styrofoam tray and enclosing them with Saran Wrap 0.01-mm thick. The exposed area is 400 cm. It is desired to keep moisture losses below 1% of the total water content estimated at 100 g per package for a shelf life of 10 days. Does the wrapping meet these requirements Assume a constant internal saturation vapor pressure of 23.8 mmHg (25dC) and zero external moisture. 

---