July, 1921
T H E JOURNAL OF INDUSTRIAL A N D ENGINEERING CHEMISTRI’
vided. The casings and runners of these pumps may be cast iron, but the shafts should be monel metal or steel with monel metal sleeves. Unless otherwise provided for, self-priming of the pumps should be insured by a by-pass from the impeller “eyes” to the respective vacuum receivers. The vertical distance from the solution pumps to the receivers should be as great as possible; the nearer the distance approaches 30 ft., the simpler the pump requirements become. A steam line should be connected to the strong brine line just beyond the outlet from Pump 1 to be used to clear the line in case of clogging with crystallized salts. VACUTJM PuMp-The vacuum on the system should be maintained by a dry vacuum pump. Its capacity should be approximately equivalent to a displacement of 4 cu. ft. of free air per min. for each sq. ft. of‘fdter area. COMBINED MOISTURE TRAP AND CONDENSER-Between the vacuum receivers and the vacuum pump there should be interposed a simple, vertical condenser, which will serve the double purpose of catching any entrained solution and condensing the vapors from the hot solution coming into the receivers. This will not only protect the pump, but will increase the efficiency of the vacuum system. Sea water will usually be available for the condenser. The condensate should pass through a “barometric leg” to a seal tank and be discarded. PIPES AND VALVES-Standard galvanized pipe may be used throughout the system, though cast-iron pipe would represent an ultimate saving in certain instances. I n any of the solution lines, the all-iron lubricated plug valve will give excellent service, also all-iron plug cocks of some designs and monel metal fitted valves can be used. RELATIVE POSITION O F APPARATUS-An ideal arrangement of the different apparatus would be such that the agitators, rotary filters, and vacuum receivers would all be on one floor level; for example, on the upper floor of a 2-story building. The solution pumps should be placed on the lower floor. The combined moisture trap and condenser should be a t such a height that the drain line from it to a seal tank located on the lower floor would be a “barometric leg.” The dry vacuum pump would be placed in any location desired and a t any convenient elevation.
EXTRACTION The minimum amount of water or other solvent which may be used in such a lixiviator is that which will hold as a saturated solution the amount of solute to be extracted; or else the amount of solvent which, mixed with the solids to be extracted, forms a sludge which will flow from the agitator to the tank of the filter. Where the solute is slowly soluble, the time of contact with solvent may be increased by increasing the length of the agitator. To the same end, more violent agitation therein may be obtained by the simple device of increasing the speed of rotation of the agitating paddles. More complete extraction is obtainable by increasing the number of stages or units; likewise by more completely dewatering the filter cake. OTHERAPPLICATIONS It is obvious that, where only extraction without the countercurrent feature is desired, it is necessary only to add fresh volumes of the extracting agent to each agitator and to discharge the filtrate wherever desired. This can be done without impairing the multiple stage and automatic feature of the apparatus. The principle and apparatus here described are applicable conversely to the purification of solutions with some solid adsorbing agent, such as bleaching or decolorizing carbon. I n the application of these materials, an excessive amount of the adsorbent must be used with a single application to
secure a complete bleaching or purification, while much smaller quantities may be used with the same purification if the material is applied countercurrentwise. This partially spent carbon can be induced to take up more impurities from a fresh portion of the solution to be purified; which is to say, that carbon which has lost its power to absorb impurities from a partially purified solution is still capable of taking up some impurities from an untreated solution. In such an apparatus as here described, the solution to be purified would take the place of the fresh water, and the fresh carbon, the unextracted kelp charcoal. Thus, the nearly spent carbon would be used finally to treat the crude solution entering the apparatus, and the fresh carbon, the almost completely extracted solution. The number of applications would be determined by the number of units, and time, temperature, and rate would all be easily adjusted over a wide range. The spent carbon finally would pass from the last filter to the reactivating apparatus. A limiting feature would be encountered in the treatment of solutions whose viscosities would preclude their filtration in vacuum filters. A similar apparatus likewise may be employed in the reactivation of carbon by the wet methods.
SUMMARY A continuous, automatic, countercurrent, multiple stage lixiviator is described, which is based on the employment of any one of the standard continuous rotary filters. The solids to be extracted are alternately extracted and filtered. They flow through the apparatus countercurrentwise against a stream of the leaching agent. The apparatus, developed for the extraction of potash salts and other values from kelp charcoal, is applicable to the washing or extraction of any materials that can be filtered on the standard vacuum filters. The efficiencies obtained and costs of operation are shown. Suggestions for various improvements are given.
National Research Council Research facilities of American industries are to be described in the forthcoming revision of Bulletin of the National Research Council, Number 2, “Research Laboratories in Industrial Establishments of the United States of America.” It is hoped that several hundred new names will appear in the revision. The demand for the first edition shows the wide interest in this subject, and the importance of having every laboratory which devotes even a portion of its time to research properly listed. The Council requests information from directors of research who have not already supplied it. The following data are wanted: name and address of firm and address of laboratory; name of director of research; number on laboratory staff (classified as chemists, engineers, bacteriologists, etc.) ; approximate proportion of time spent on research; chief lines of research: unusual features of equipment; research laboratory space; date of organization of research laboratory and annual expenditure for research. Confidential information is not desired. This material should be furnished as promptly as possible to the Research Information Service, National Research Council, 1701 Massachusetts Avenue, Washington, D. C. The fifth annual report of the Council has recently appeared. The program laid out a t the time of its reorganization from a wartime to peacetime organization in 1918-19 has so far been followed along its essential lines, the principal changes being ones of extension. During 1920 the Council has been an organization controlled by its own membership and supported by other than government aid. The Council, however, maintains close contact with government departments through its division of Federal relations.
