Air drying plant

Dry compressed air is required for operating diaphragms in control valves for process streams, for flushing out residual liquids in pipe lines, for operating drain valves of certain reactors, for opening vent valves, etc. 

The main components of an air drying plant are as follows which shall be checked thoroughly while procuring the plant. 

Various methods are used for removal of moisture from compressed air (i) by absorption in silica gel and then regenerating it by electrical heating or by using heat of compression and (ii) refrigerated type for removing moisture by condensation. 

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Our standard procedure consisted of first defatting the air-dried plant material with n-hexane followed by extraction with solvents of increasing polarity starting from chloroform, chloroform-methanol 9 1, methanol, and water in a Soxhlet apparatus or at room temperature. Only in a few... 

The air-dried plants were ground and extracted with carbon dioxide in a high pressure apparatus equipped with 5 L volume extractor vessel. Fractionation of extracts was carried out by releasing the separation pressure at two stages. A more detailed description of the apparatus and extraction is given extensively elsewhere [5], 1000 g of the plant material was weighed accurately and supplied into the extraction vessel. The desired temperature and pressure were adjusted and CO2 feed was started. The accumulated product samples were removed and weighed at certain time intervals. Two or three parallel experiments were made at each extraction and separation circumstances. 

The alkaloids were extracted from air-dried plant material with ethanol, the ethanol extract concentrated, acidified with acetic acid and extracted successively with diethyl ether, ethyl acetate and chloroform to remove impurities. The acidic aqueous solution was made alkaline with ammonia and extracted with chloroform. After concentration this chloroform extract was gas chromatographed on a packed 3 % OV-17 column on Gas Chrom Q by temperature... 

The defatted, air-dried plant material is extracted with methanol, either cold or hot, or with 50% aqueous methanol at ambient temperature. Fresh plant materials have to be processed immediately after collection to prevent fungal growth and enzymatic hydrolysis of the saponins. During extraction, care should be taken as saponins may undergo transformation, e.g. esterification of acidic saponins, hydrolysis of labile ester groups or transacylation, etc. Often the crude extract is suspended in water and partitioned using ethyl acetate and -butanol successively. Most of the saponin constituents are found in the -butanol soluble fraction. However, the low-polar saponin constituents may be present in the ethyl acetate part while the most highly polar saponins may be found in the aqueous layer, as in the case of Saponaria officinalis [2],... 

Sparling, C.P. and Ross, D.J. (1 988) Microbial contributions to the increased nitrogen mineralization after air-drying. Plant and Soil 105, 153-157. 

Plant Samples. Air-dried plant samples were ground in a Wiley mill. Care was taken to avoid cross contamination between samples through the mill. Five hundred mg each of dried leaf sample were combusted... 

Check operation of air-drying plant (including proper switching on and off the compressor motor as per draw of air from outlet) and the complete pipelines for any leak. The pipelines should be strong enough to withstand high pressure. Check all air filters. 

Working of all utilities such as air-drying plant, thermic fluid heating systems, packaged steam boilers, diesel generator sets for emergency power supply,... 

Phytochemistry Leaves contain the diterpene alcohol lagochilin, 0.03 % essential oil, 11-14 % tannins, 7-10 mg% carotene, vitamin C, organic acids, calcium, and iron salts, and 0.6-0.7 % flavonoid glycosides. LagochiUn (1.98 %), tannins (2-2.7 %), ascorbic acid (106.29 mg%), carotene (4.39 mg%), and essential oils (0.083 %) were isolated from air dried plants (Akopov 1981). 

Sugar alcohols should be extracted immediately from fresh material to avoid their enzymatic degradation. Air-dried plant material and even material stored at deep freeze temperatures (— 25°C) over a long period should be avoided for the same reason. Plant material must be free of microbial infection and contamination. 

Various types of air drying plant ate available (i) Electrically heated, (ii) Refrigerated-type, (iii) Using the heat of compression. While the first two consume electricity for regenerating the dryer, the third type nses a part of the compressed hot air. 

The size of the equipment depends on the local atmospheric conditions. When specifying an air drying plant, detailed data on the local climate must be given to the sulphonation equipment supplier, so that the correct air drying plant is obtained. A typical air diying plant is depicted in figure 8. 

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