Moisture content cotton

Because the gin capacity is usually not sufficient to keep up with the harvesters, the harvested cotton is often stored in a compacted module and ginned at a later date. The type of storage or seed cotton processing may place additional constraints on the harvest process. If the seed cotton is to be placed in module storage, the cotton should not be harvested until the moisture content is 12% or less and the harvested seed cotton should be free of green plant material such as leaves and grass. 

Before nitration the moisture content of the purified linters is reduced to well below 5% since the presence of water will modify the progress of the reaction and tends to produce undesirable products. The drying operation is carried out by breaking open the cotton linters and passing along a hot air drier. 

Figure 5. Rate of heat evolution in wood and cotton. Experiments 70 C included heat of pyrolysis 80 C the material was moist, 130"C it was ovendry between 80" and 130 C, moisture contents are mentioned in %, unless the material was ovendry. 1 — Bowes (28) wood raspings heat values extrapolated from measurements at 190-335 C. 2 — Eriksson and...

High moisture content is the single biggest problem that arises because of improper harvesting. Cocke (23) concluded that cotton harvested at high moisture content was extremely difficult... 

Cotton of moisture content seven percent or less should not be dried. 

Cotton of moisture content eight percent or more should be dried. 

The temperature in the middle section was varied from 40°C -70 C as required to maintain a final cotton moisture content of 3-4%. The total water-to-fiber ratio was 55/1 for this experiment and represents a minimum for wetting under these conditions. 

Cellulose material, such as cotton or wood cellulose, is dried until the moisture content is below 1%, or in the pneumatic drier to ca. 2%, and then loaded into sealed sheet metal containers or bags, to cool to room temperature. 

Information in Table II describes the performance characteristics of typical seed cotton drying systems and Illustrates some of the effects of drying fibers to a level below the optimum. Generally, these data show that fibers ginned at moisture contents below 6 percent were shorter and produced lower yarn break factors than fibers ginned at moisture contents above 6%. Obviously, the amount of energy required for drying... 

If waste byproducts from the cotton ginning operation are not utilized in some manner, they create a disposal problem. Conversely, ginning waste is an excellent source of raw material that can be converted into energy, on-site, and utilized concurrently during the processing operation. Research has shown that the heat value of cotton gin waste averaged 7,928 Btu/lb (dry weight) or about 7,000 Btu/lb at 11% moisture content (17). 

The cotton and rayon used as fillers in solid oral dosage form containers may not meet pharmacopeial standards, but through appropriate tests and acceptance criteria for identification and moisture content, their adequacy should be shown. For example, rayon has been found to be a potential source of dissolution problems for gelatin capsules and gelatin-coated tablets. 

When cotton is treated with very dilute solutions of hydrogen chloride in an aprotic solvent such as benzene it suffers severe degradation. This is because the small amount of hydrogen chloride in the solvent is redistributed in the water adsorbed on the cotton, forming a very concentrated aqueous solution of hydrochloric acid [454]. At low moisture contents, the sites of the consequent hydrolysis are near the ends of the cellulose chains. The relation between DP and copper number therefore differs from that for normal aqueous hydrolysis. However, as the moisture content of the cotton increases, the type of hydrocellulose produced approaches that found with aqueous systems. 

The response of the cotton fiber to heat is a function of temperature, time of heating, moisture content of the fiber and the relative humidity of the ambient atmosphere, presence or absence of oxygen in the ambient atmosphere, and presence or absence of any finish or other material that may catalyze or retard the degradative processes. Crystalline state and DP of the cotton cellulose also affect the course of thermal degradation, as does the physical condition of the fibers and method of heating (radiant heating, convection, or heated surface). Time, temperature, and content of additive catalytic materials are the major factors that affect the rate of degradation or pyrolysis. 

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