Search Documents

By Robert Schorr

PAGE 1. Introduction,........... 82 2. Characteristics of Briquettes,........ 87 3. The Manufacture of Coal- and Coke-Briquettes,.... 89 Binders, Organic and Inorganic,...... 90 Mixing,...........94 Presses, Continuous and Intermittent Action,....95 Cost of Briquettes and Sales-Prices in Various Countries,.. 99 4. The Manufacture of Peat-Briquettes,......101 Solid Peat-Slabs,.........101 Solid, Carbonized Peat-Briquettes,......103 Estimates of Cost of Operating Peat-Briquetting Plants,... 105 5. Manufacture of Mineral-Briquettes for Metallurgical Processes,.. 108 6. Manufacture of Artificial Stone-Masses,......112 7. Bibliography,...........115 Introduction. Briquetting is apparently a very simple operation, yet it has offered so many mechanical and chemical difficulties that it required almost a century to place it on a commercial basis. Since 1860, however, the progress has been steady and satisfactory, and to-day, for most of the European coal companies, the briquette-plant is a very profitable investment. Among the many applications of scientific knowledge to further economy by recovering and utilizing by-products and raw materials, there is possibly none which deserves the attention of Americans to a higher degree than briquetting. The recent miners' strike in Pennsylvania, which resulted in a scarce and irregular supply of coal at a high price, has advanced the possibilities for briquetting, and as a consequence public interest has grown rapidly. While the manufacture of coal-briquettes is not new in the United States, adverse conditions and sometimes lack of

Jan 1, 1905

By C. E. Kemp, A. B. Dyes

Results of a field research project on the thermal recovery of oil by movement of a combustion front are presented. This field test was conducted in the South Belridge field, This The war paitern was a Southsing1e 2.5-acre five-spot pattern in the 700-ft deep Tulare sand. Results of this project indicate the technical feasibility of producing high viscosity, low-grallity crude oils by thermal means. It was demonstrated that heavy oils could be moved rapidly over considerable distances by thermal drive, and that high percentage recoveries of oil could be effected. The bulk of the oil recovery came after arrival of the burning front at a production well. However, rapid corrosion and high-temperature failure of conventional pipe and equipment both below and above surface occurred. Stainless steels gave more satisfectory performance under these conditions than did conventional steels. Oxygen was seldom observed in gas from wells ahead of the burning front, and it appears that the front was continuous throughout the life of the experiment. INTRODUCTION During late 1953 and early 1954, industry-wide attention was focused on the thermal recovery of oil by movement of a combustion front through an oil zone. Two separate Oklahoma field tests were described in publications by Kuhn and Koch, and Grant and Szasz. To obtain basic information needed for making engineering and economic appraisals of commercial recovery of heavy oil by this thermal recovery method, a new field research projecta3,4 was started May 31, 1955. Twelve oil companies contributed to this project with General Petroleum Corp. as operator. Since combustion recovery experiments* with heavy oils in other areas had been conducted in small patterns,"' an important purpose of this test was to determine whether the process could be operated in a pattern of near-commercial well spacing. The south Belridge field, located 30 miles north of Taft, Calif., was chosen because its oil sands are similar to many heavy oil sands which typically have low primary recovery and leave a large amount of oil in place. such fields are not particularly suited for common secondary recovery methods. DESCRIPTION OF TEST SITE The test interval was a Tulare sand at a depth of about 700 ft. Nine test wells were drilled, cored and completed from Oct., 1955, through Jan., 1956. The initial pattern shown on the map, Fig. 1, consisted of an injection well (II)', four producing wells (1P-4P), and four observation wells (IT-4T). An old well (81) was also recompleted for use as an observation well. The area enclosed by the original four production wells was 2.5 acres; the distance from the injection well to each production well was 233 ft. During the combustion period, Well 5P was drilled to replace Well 2P, and Well 6P was drilled to replace Well 3P. The new wells were 25 ft beyond the old production wells along a diagonal from the injection well, and resulted in an increase in pattern area to 2.75 acres. Isopachs are shown in Fig. 1. The average thickness of the oil sand in the test pattern was 30 ft. Fig. 2 presents two cross sections through the test pattern. Oil sand is represented by white and claystone by gray. The dashed lines indicate layers of conglomerate grading to claystone. The sand thickness was fairly uniform throughout the test pattern except in the 1P area. The sand body dips gently from the northwest to southeast, about 3 degrees from horizontal. The sand is unconsoli-dated, and grades from very fine material to pebbles as large as 2 in. in diameter. Table 1 presents the average initial properties of the formation. The in-place porosity of 37 per cent was estimated from the porosity of coke-consolidated cores taken after combustion. Original core analyses data were adjusted to 37 per cent, giving pore volume saturations of 60 per cent oil, 37 per cent water, and 3 per

By Charles A. Colton

(Read at the Amenia Meeting, October, 1877.) THE results of a series of analyses extending over a period of three weeks at the Cedar Point Iron Company's furnace, Port Henry, New York, are given in Tables I and II. This furnace uses a very pure magnetite and Lehigh and Lackawanna anthracite. The flue leading the gas from the "down-comer" to the boilers was tapped by a a inch gas pipe, which carried the gas to the Orsat apparatus. The pressure of the gas not always being sufficient, owing to the small amount made, to force it into the apparatus, I omitted taking samples several days, and with the exception of the last three days of the campaign, made the analyses whenever opportunity offered. I find the Orsat apparatus, as described by Prof. Egleston,* to work very well, with one exception. The CO is not absorbed as readily in the ammonia-copper solution as he states in his description of the apparatus, as many as 50, and sometimes 60, passes being necessary to absorb all the CO. The power of absorbing rapidly increases as the solution is used, and this would indicate that the more oxygen it contains the quicker will it do the work. Probably the addition of a small amount of some oxidizing agent would remedy this. When the furnace was working in its normal condition, I had no occasion for using the filter, the amount of fume being so small as not to cause any inconvenience. The gas burned with the flame peculiar to CO, and contained just enough solid particles to give it a slight reddish tinge. * See Transactions, II, 226; V, 487, 621.

Jan 1, 1878

By O. B. Buchlen, J. W. Smith

The Coal Research Bureau of the School of Mines at West Virginia University, using an experimental flotation cell designated an airlift-cyclone was able to obtain a clean coal product containing 7.64% ash with 94% yield and 97% coal recovery. This favorable performance was obtained with the experimental flotation cell operating as a simulated three-stage unit on slurry taken from the fine coal circuit of a coal preparation plant. This experimental device, consisting of a sheet metal cyclone-like unit mounted on a U-shaped uplift pipe, uses a combined flotation and cyclone action to beneficiate the minus 14 mesh partially cleaned feed product. In addition to providing comparable analytical results, the airlift-cyclone possesses other attractive features among them being a low capital expenditure, utilization of moderate plant floor space, efficient operation on high density feed slurry, and absence of moving parts. The primary shortcoming of the experimental cell is its limited capacity. The Coal Research Bureau presently has under construction a larger unit which, it is hoped, will provide the capacity and quality to establish the airlift-cyclone as a commercially feasible unit. Froth flotation of fine coal is a practice which has only recently gained wide acceptance in this country. Various explanations can be put forth for this delayed acceptance of a very selective and efficient system of coal preparation. Among these reasons would be the advent of continuous mining machines resulting in the increased production of coal fines, the change in market patterns from domestic and rail consumers who did not want fines to a predominantly utility market which normally consumes fines, and also the imposition of legal restrictions in regard to stream pollution. However, the major detriment is probably the high cost involved both in installation and operation of the flo- tation unit and auxiliary systems. These facts assume greater emphasis when considering that froth flotation installations normally process a low quality feed product. A recent estimate' of installation costs including dryers, filters, and other auxiliary equipment for a flotation system was $5000 to $7000 per ton of capacity while the operating costs, exclusive of auxiliary equipment, were estimated at 10 to 306 per ton of feed. The Coal Research Bureau of the School of Mines at West Virginia University is currently developing a simplified froth flotation cell, designated an airlift-cyclone, which may provide considerable savings in capital and operating costs without sacrificing product quality or recovery. This experimental cell consists of three primary components: 1) a vertically mounted U-shaped pipe; 2) an air injector device; and 3) an integrally mounted cyclone-like unit (Fig. 1). A feed slurry is introduced at the top of one leg of the U-pipe while compressed air is injected near the base of the other leg. The air serves both to aerate the pulp and to cause it to flow upward into the base of the cyclone unit where the floated clean coal is separated from the reject material and unfloated coal which remains in slurry. The Coal Research Bureau's experimental airlift-cyclone is somewhat similar in principle to a flotation device developed by Russian engineers in the late 1950's. In tests upon a two-stage pilot-size device, the Russians obtained very favorable cleaning efficiencies.' However, later experience with production models demonstrated that rated capacities and acceptable product quality could not always be maintained.3 Because of these limitations, Russian engineers subsequently recommended that conventional, mechanical cells be used when cleaning difficult to float slurries. Engineers at the Coal Research Bureau felt that such a device utilizing the combined actions of a cyclone and a froth flotation machine offered numerous attractive features and merited investigation. Accordingly, a small capacity experimental airlift-cyclone was designed and, with the permission of the Christopher Coal Company Div. of Consolidation Coal Co., installed in Christopher's Humphrey preparation plant near Morgantown, West Virginia.

Jan 1, 1964

By W. A. Walker, G. W. Ostroot

An increase in the number of deep wells being drilled where extreme bottom-hole temperatures are encountered, and the anticipated drilling of wells where temperatures in the range of 500°F or higher may occur, has brought about a comprehensive investigation of cementing materials and of the techniques involved in their proper usage at these elevated temperatures. Included are developments in cements, retarders, weighting materials and other cement additives which make it possible to formulate a variety of compositions to help resolve the cementing problems of these extreme well conditions. The problems associated with the selection and testing of cements are discussed, and a resume of field results is included. Previous studies on strength retrogression indicate that caution should be exercised in the selection of a cementing composition for use in high-temperature wells. It now appears that, by the addition of silica flour as a stabilizing additive to certain cements, compositions covering a wide range of slurry densities can be designed to meet extreme well conditions without strength retrogression. Improvements in cement retarders make it possible to produce a four-hour thickening time at static temperatures up to 500°F. This temperature is considerably higher than conditions presently being encountered in drilling and completion work. Inert weighting materials, used to produce 20-lb/gal or heavier cement slurries, are reviewed. INTRODUCTION As the search for oil continues, the number of wells being drilled to depths of 10,000 ft or below has continued to increase over the past decade. During 1959, there were 50,893 wells drilled in the United States for a total of 209 million ft of hole. Of this total, approximately 4.45 per cent were drilled below 10,000 ft and 0.30 per cent below 15,000 ft, with a record depth of 25,340 ft recorded (Table 1). With the drilling of this record-shattering hole comes the question, "How deep can wells be drilled?".' Limitations with respect to equipment (surface and subsurface), cementing materials and techniques would cause some concern; however, a panel of experts have agreed that the U. S. oil industry has the equipment and know-how to drill a 50,000-ft hole. The greatest deterrent would be the 700°F temperature they would anticipate encountering at this depth. Although the number of wells drilled under what is generally considered hot-hole conditions (230°F and higher) has been relatively high, each well often presents distinctly individual problems and requires separate consideration and selection of special materials, techniques and equipment. At the present time there are over 30 additives and special cements available for use in "tailoring" a cementing composition for a specific well. It is not uncommon to use three or four different additives with the basic cement to produce the desired slurry characteristics. A generally accepted procedure is to make laboratory tests on selected cementing compositions prior to pumping them into wells deeper than 12,000 ft, or where static temperatures are in the range of 260°F or higher. In some instances, it is recommended that laboratory tests be made where less severe well conditions are encountered. Prior to selecting a cementing composition for a particular well, key personnel representing the operator, drilling contractor and service company should meet to determine that each individual is acquainted with every detail which might influence cementing results and to discuss the execution of the job. For cementing hot-holes, a number of factors must be evaluated before proceeding with the operation. Consideration must be given to the following. 1. Thickening time—The slurry must remain fluid for a sufficient length of time to allow displacement down the casing and up the annular space in a primary cementing job or, in squeeze-cementing, adequate thickening time for both the build-up of a satisfactory squeeze pressure and the reversing out of excess cement. The thickening time of standard retarded cements will often be too short under extreme temperature conditions, thus involving special formulations and requiring laboratory tests to determine the proper amount of additional retarder to obtain the desired pumpability.

The Institute conducts jointly with the American Society of Civil Engineers, 'American Society of Mechanical Engineers and American Institute of Electrical Engineers, certain activities as listed below, and is joint owner with them if certain properties. United Engineering. Trustees, Inc. When Mr. Carnegie made his gift which made possible a home for the engineering societies, a separate corporation was organized to act as a holding company and to manage the common property. This was long known as the United Engineering Society but the name has now been changed to one which more nearly reflects the real function of the corporation. It holds title to the Engineering societies Building and to various funds placed in its charge and is managed by a Board of Trustees of which three are chosen by each of the four societies, American Institute of Mining and Metallurgical Engineers, American Society of Mechanical Engineers, American Institute of Electrical Engineers and American Society of Civil Engineers, which own equal and undivided interests in the property. The land and building cost two million dollars. The interest of each of the Founders societies, aside from especial trust funds, is now valued at $493,352. The A. I. M. E. trustees are Arthur S. Dwight, J. V. N. Don and George D. Barron. The President of the Board is Francis Lee Stuart and the Secretary, Alfred D. Flinn.

Jan 1, 1929

The Institute conducts jointly with the American Society of Civil Engineers, American Society of Mechanical Engineers and American Institute of Electrical Engineers, certain activities as listed below, and is joint owner with them of certain properties. United Engineering Trustees, Inc. When Mr. Carnegie made his gift which made possible a home for the engineering societies, a separate corporation was organized to act as a holding company and to manage the common property. This was long known as the United Engineering Society, but the name has now been changed to one which more nearly reflects the real function of the corporation. It holds title to the Engineering Societies Building and to various funds placed in its charge and is managed by a Board of Trustees, of which three are chosen by each of the four societies, American Institute of Mining and Metallurgical Engineers, American Society of Mechanical Engineers, American Institute of Electrical Engineers and American Society of Civil Engineers, which have equal and undivided interests in the property. The land and building cost two million dollars. The interest of the Founders societies, aside from especial trust funds, is now valued at $1,987,793. The A. I. M. E. trustees are William H. Bassett, H. G. Moulton and R. M. Roosevelt. The President of the Board is Harold V. Coes and the Secretary, Alfred D. Flinn.

Jan 1, 1934

The Institute conducts jointly with the American Society of Civil Engineers, American Society of Mechanical Engineers and American Institute of Electrical Engineers, certain activities as listed below, and is joint owner with them of certain properties. United Engineering Trustees, Inc. When Mr. Carnegie made his gift which made possible a home for the engineering societies, a separate corporation was organized to act as a holding company and to manage the common property. This was long known as the United Engineering Society, but the name has now been changed. to one which more nearly reflects the real function of the corporation. It holds title to the Engineering Societies Building and to various funds placed in its charge and is managed by a Board of Trustees, of which three are chosen by each of the four societies, American Institute of Mining and Metallurgical Engineers, American Society of Mechanical Engineers, American Institute of Electrical Engineers and American Society of Civil Engineers, which have equal and undivided interests in the property. The land and building cost two million dollars. During the gear 1934, the constitution and By-laws of The United Engineering Trustees, Inc., were thoroughly revised and a better organization of its functions was affected: The Engineering Foundation and the Engineering Societies Library were made "departments? of the United

Jan 1, 1936

By Orr Hamilton

VALUATION of a mine is an approximation of its true cash value which requires the application of fundamental principles of economics. Mines are valued from necessity, for the following reasons: (a) Transfers of titles. (b) Dissolutions of partnerships or corporations. (c) Mergers of mining companies. (d) Appraisals for the purpose of State and Federal taxation. (e) Establishment of the fact of worth as a basis of loans. (f) Determination of values as frequently required in litigation. (g) Listing of stock for sale by a reputable stock exchange. For the majority of purposes a valuation is required as at the present time, but for some purposes valuations as of bygone times may more nearly reflect the intrinsic worth of a mine because its subsequent history can never be, entirely ignored, but valuations made as at the present time are better indicators of cash values. Many mines with great intrinsic worth have been sold for small cash prices. The object of legitimate mine valuations is to deter-mine salable value, or that price in cash at which a transfer of the property from a willing seller to a willing buyer might be consummated, assuming that both vendor and vendee have knowledge of all pertinent data and that the owner, is not forced to sell at a sacri-fice-the definitions of fair market value precluding a forced sale.

Jan 11, 1923

The Institute conducts jointly with the American Society of Civil Engineers, American Society of Mechanical Engineers and American Institute of Electrical Engineers, certain activities as listed below, and is joint owner with them of certain properties. United Engineering Trustees, Inc. When Mr. Carnegie made his gift which made possible a home for the engineering societies, a separate corporation was organized to act as a holding company and to manage the common property. This was long known as the United Engineering Society but the name has now been changed to one which more nearly reflects the real function of the corporation. It holds title to the Engineering Societies Building and to various funds placed in its charge and is managed by a Board of Trustees of which three are chosen by each of the four societies, American Institute of Mining and Metallurgical Engineers, American Society of Mechanical Engineers, American Institute of Electrical Engineers and American Society of Civil Engineers, which own equal and undivided interests in the property. The land and building cost two million dollars. The interest of each of the Founders societies, aside from especial trust funds, is now valued at $493,352. The A. I. M. E. trustees are Arthur S. Dwight, J. V. N. Derr and George D. Barron. The President of the Board is Francis Lee Stuart and the Secretary, Alfred D. Flinn.

Jan 1, 1923

The opening session was held on Tuesday evening, June 28th. Mr. F. S. Witherbee, of Port Henry, a member of the Local Committee, welcomed the Institute as follows: Mr. President and Gentlemen and (if I my also add) Ladies of the Institute: In the absence of the Chairman of our Local Committee it is my pleasant duty to give you a cordial welcome once more to the shores of Lake Champlain. I think some fourteen years have passed by since we last had the pleasure of receiving you at a meeting in this vicinity ; but the pleasure of that meeting still lingers in our memory; and the profit which we derived from your discussions and from your presence with us has made us heartily desirous to have you here again. If the truth must be known, we were for a time much embarrassed by the difficulty of providing adeqriate and comfortable shelter for the large number of friends whom we hoped (and, as this assembly indicates, had good reason for hoping) to receive. But the liberality and zealous co-operation of the Delaware & Hudson Canal Company and its hotel manager, in offering to open Hotel Champlain, at no little inconvenience, before the usual time, presented a solution of this difficulty, provided the date originally proposed for the meeting could be changed to a week later. This change was duly authorized; .and I think you will all agree with us that it was wise.. At all events, I am sure, I now need offer no apologies for the roof which covers yau. During the fourteen years which have elapsed since your last visit to us, great strides have been made in the industrial development of this country. The meetings of the Institute, held from one end of the land to the other, have permitted you to witness the transformation of small hamlets? like Birmingham, Ala., into populous and thriving industrial centers. You have seen the Minnesota and the

Jan 1, 1893

By James H. Boettcher

INTRODUCTION There are many and varied sources of finance available to the mining industry for exploration, development and/or the operation of mining projects and companies. These sources include equity from major as well as "penny" stock exchanges, precious metal mutual funds, private investor groups (from "grubstakes" to tax-oriented limited partnerships) and banks. The variety is representative of the fact that the world's capital markets are segmented and stratified according to risk-reward characteristics. This interrelationship is summarized in Exhibit I and 2 which relate (very approximately) various sources of finance to a typical mining project's life cycle and risk-return characteristics. The objective of this paper is to introduce, as it applies to the mining industry, a somewhat recent phenomenon represented by one of these capital markets segments referred to as "venture capital." Venture capital investing per se, which today is a multibillion dollars per annum investment business, goes back as far as Queen Isabela's backing of Columbus' "wild ideas." The real institutionalization of the venture capital process really began in earnest, however, after World War II. Today over 700 private venture capital sources (and more government related ones) exist providing funding to a range of industries, but typically related to the "high-tech" business. The table to the right shows industries financed by venture capital funds between 1980 and 1982. Conspicuous by its absence is, of course, mining which is not a great surprise since typical mining projects up until recently were large, required long lead times and were undertaken by established mining houses. Also, as most of you can appreciate, successful investing in the mining business requires a great deal of experience and understanding of the industry which most venture capital funds do not have. TARGETED RETURN The rate of return objective of most venture capital funds is, according to the legalized version, to realize a return which is "substantially in excess of that obtainable through conventional equity investments." One may say that a common objective of venture capital funds is to realize a 20% to 30% compound annual internal rate of return on capital over their life which is often ten years. [ ] This objective has been recently more feasible in the mining sector due to the development of smaller precious metal projects which cost less and are quicker to generate cash flow than the behemoth projects of the 1970s. In addition to precious metals, venture capitalists have invested or looked at a variety of other mining projects including ones as prosaic as a high margin "kitty litter" operation, sand-gravel and other industrial minerals operations, the leveraged buyouts of coal mines or mineral divisions of major energy or mining corporations, and even in in-situ copper or gold leaching ventures. A typical investment is in the range of $100,000 to $3,000,000 although some can go as high as 5,000,000. This implies a project size up to, say, 30,000,000 if a venture capital fund does it on its own. Larger projects can be done if the equity portion of the investment is syndicated with other investors.

Jan 1, 1985

By John C. Robison

INTRODUCTION Sensitivity analysis is a means of gauging the impact of individual risks on a financing. Key risks can occur in three time periods: - Feasibility, engineering and construction phase; - Start up phase (usually through completion); - Operating phase (post completion). If a company has agreed to cover these risks prior to completion, then less attention will be paid to the sensitivity of the project in the first two time periods. Since the operating phase of the project generates cash for both operations and debt service and generally does not begin until two to six years after the loan is signed, it is wise to look at scenarios other than the projected "base-case" scenario in order to determine the project's capability to operate successfully under a broad range of probable future events. Lenders are compensated at a fixed spread over their borrowing base and generally are not compensated if the project is successful beyond expectation. They are also subject to the loss of principal plus funding costs if the project performs below expectation. Because of this, lenders establish sensitivities around the parameters of conservative projections developed in the project feasibility studies and the cash flows resulting from these projections. The initial cash flow projections should demonstrate the project's ability to meet cash costs, debt service requirements (principal and interest), and still have sufficient cushion to cover contingencies such as strikes, price fluctuations, force majeur situations, etc. (See Schreiber, Chapter 10). The selection of the level of sensitivity analysis to be performed is the result of both objective criteria, including probabilistic analysis applied to the technical parameters, and, of equal importance, subjective criteria applied by the analysts, especially with regard to the economic and financial parameters impacting the project cash flows. RISK SENSITIVITY Assumptions used in the cash flow projections should be realistic. Risks identified by the lenders should be identified and cash flows prepared to assess whether these project risks are acceptable. Typical project risks include the following (see also Chapter 9): - Sufficient reserves - quantity and quality - Product price - Production level - Operating costs - Availability of energy and supplies - Transportation and infrastructure requirements and costs - Interest rate - Completion risks - Tax level - Political risks - Cost over-run risks - Operator experience - Management - Technological risks - Environmental permits and risks - Foreign exchange risks - Insurance coverage - Equity of sponsors - Inflation rate - Capital expenditure during project life In order to see the effect on the cash flow projections, each risk should be analyzed for its impact on the cash flow generating capacity of the project. Sensitivities can be examined to see if the resultant cash flow projection will meet the lenders minimum credit standards. 1.Reserve Sensitivity In general, lenders will not assume the reserve risk. However, it should also be noted that lenders receive loan proposals in which reserves range anywhere from proven to possible. Sensitivities are not generally run for various reserve levels and reserve estimates are either considered acceptable or not acceptable by the lenders.

Jan 1, 1985

By R. G. Wayland

SINCE the installation at Kropfmuehl, Bavaria, of a modern flotation concentrator in 1938, the flake and fine graphite from the Passau area can now be delivered in about any normal specified carbon content of any size range up to a flake averaging about 0.7 mm. The graphite finds a wide German and export market for crucible manufacture, pencil leads, dry cells and other uses. A controversy over the origin of the graphite deposits is being resolved in favor of syngenesis rather than epigenesis. The syngenetic theory is newly supported by the yet unpublished work of Hartmann of the Bavarian Geological Survey. Development work and exploration for graphite in the area may be changed in direction as the syngenetic theory is accepted. Crystalline graphite is produced in the area east of Passau near the junction of Germany, Austria and Czechoslovakia, as shown in Fig. 1. This is the only graphite area of importance in Germany, and Gra-phitwerk Kropfmuehl AG is the only operating firm in the area. The plant and mine are located at Kropfmuehl near Hauzenberg, Kreis Wegscheid, about 10 miles east of Passau. A narrow gage railway from the mine connects with the German Railway at Schaibing Bahnhof. The Pfaffenreuth mines date from about 1730. Until the early 20th century mining operations were carried out in a haphazard fashion. During World War I graphite mining and milling was increased, since it had to cover almost all of the crucible needs of the Central Powers. Between the wars some 11 mines were operated by two large and several small companies, but under the Nazis these were consolidated by 1938 into the Kropfmuehl enterprise. Kropfmuehl built a modern flotation mill to treat its own ores and small amounts of custom ores and tailings from the area. Since Graphitwerk Kropfmuehl AG was an I.G. Farbenindustry subsidiary, it has been under Military Government Property Control and probably will be sold to private German capital. Geology The country rock of the graphite area is part of the "kristallines Grundgebirge," the series of old gneissic and schistose rocks that constitutes the bed rock of most of the Bohemian basin and rims the Sudeten-land. The gneissic rocks of the graphite area are considered to have been metamorphosed during the Carboniferous period. They are bordered on the north by granite stocks and penetrated by numerous smaller granite and pegmatitic intrusive rocks, as shown in Fig. 1. The gneiss is classed as a micaceous, coarse-grained cordierite gneiss by most investigators. It is much metamorphosed by the granite, particularly in the north near the larger granite bodies. Interbedded in the gneiss are the graphite seams and lenses, and also beds and lenses of crystalline limestone containing disseminated graphite in noncommercial quantities. The gneiss, together with the included graphite and limestone seams and lenses, is cut and displaced by a number of granite sills of medium to fine grain and by a large number of diorite lamprophyre dikes and a few syenite-pegmatite dikes. The lamprophyre dikes are of various mineral compositions and textures, but many are banded and richly impregnated with pyrite; while the syenite-pegmatite dikes are coarse-grained with good crystals of titanite, pyroxene, uralite and other green amphiboles. Most investigators and the miners speak only of diorite and granite dikes cutting the graphite seams. The diorite dikes are later than the granite and some of the faulting, as is evident from Figs. 1 and 2. Individual graphite seams and lenses may be mined for thicknesses of several feet up to several scores of feet, and for distances of several hundred feet. The aggregate thickness of a series of some 20 seams of graphite, limestone and interbedded gneiss at Kropfmuehl is stratigraphically about 450 ft. Laterally, the graphite in a seam may pinch out or grade into crystalline limestone. Graphite crystals also are found disseminated in the gneiss itself, although in unmineable concentrations. The faults that cut the graphite seams carry graphite for some feet or tens of feet away from the seams, apparently mechanically. Similarily, the graphite lenses themselves often contain mechanically introduced inclusions of wall rock, probably from flowage during folding. Graphite crystals make up 10 to 30 pct of the fresh, mineable graphite lenses at Kropfmuehl, averaging about 20 to 25 pct after hand-sorting by the miners. In weathered lenses, the graphite concentration is said to be as high as 50 pct. The associated primary and hydrothermal minerals are dom-inantly feldspar and calcite, plus quartz, pyrrhotite, pyrite, biotite and occasional garnet, hornblende, sphalerite and galena. Associated secondary minerals include kaolin, nontronite, mangano-oxide-silicates (mog), adularia and chlorite. The superimposed suite of siliceous cementation minerals present consist largely of opal, chloropal, chalcedony, jasper, and hyalite. The kaolin is of special interest since it too was mined as early as 1730 and was used in the well-known Nymphenburg porcelain from 1756 on. The kaolin is derived from the gneiss and the syenite pegmatites. The crystals of graphite vary in size within a given seam, but in seams more than a mile away from the granite on the north the average crystal-linity is less coarse, lowering the commercial value. The lenses in the Kropfmuehl-Pfaffenreuth area are the most developed, and are the only ones with deep workings now accessible. Other similar crystalline graphite lenses are known from older workings at Habersdorf, Oberoetzdorf, Ficht, Diendorf, and

Jan 1, 1952

[Separates of all the Technical Publications published in 1930 are available at Institute headquarters. All the papers are on file in public, university and technical libraries, and when so indicated in the list, may be found in the Transactions.] Metal Mining Technical Publi- Title Author Meeting Tran~. cation Volume No. and Page* 264-A.29 Quicksilver Industry in 1929. Im- L. H. Duschak San Francisco T30, 283, 319 provements in the Metallurgy of C. G. Maier and Oct., 1929 Quicksilver and Symposium on The others Present Status of the Quicksilver Industry (With Discussion) (37) 271-A.30 Observation on Ground Movement R. E. Palmer New York T30. 168 and Subsidences at Rio. Tinto Feb.. 1930 Mines, Spain (20) 274-A.31 Development and Installation of the C.L.Berrien New York T30, 139, 166 Hawkesworth Detachable Bit (29) Feb., 1930 276-A.32 Protective Measures . Against Gas 0. A. Glaeser New York T30, 129. 167 Hazards at United Verde Mine (11) Feb., 1930 287-A.33 Use and Cost of Compressed Air (12) R. S. Lewis New York Feb., 1930 314-A.34 Miami Copper Company Method of F. W. Maclcnnan New York T30, 39, YO Mining Low-grade Orebody (44) Feb., 1930 319-A.35 How Human Beings Respond to W. J. McConnell New York Changing Atmospheric Conditions Feb., 1930 (9) 324-A.36 Vertical and Incline Shaft Sinking at Arthur B. Foote San Francisco T30, 87 North Star Mine (21) Oct., 1929 32bA.37 Governmental Control of the Pro- W. E. Colby New York duction and Sale of Mineral Re- Feb.. 1930 sources (With Discussion) (16) 333-A.38 Some Recent Developments in Open- E. E. Hunner New York T30, 106, 117 pit Mining on the Mesabi Range Feb.. 1930 (25) 334-A.39 Mining Methods and Costs at Presi- V. D. Howbert El Paso dio Mine of American Metal Co. of R. Bosustow Oct., 1930 Texas (15) 339-A.40 Operation of Pressure Fans in Series W. 8. Weeks New York (8) V. 6. Grishkevich Feb., 1931 364-A.41 Top Slicing with Filling of Slices as H. Willey El Paso Used at the Charcas Unit of Com- Oct., 1930 pania Minera Asarco, S. A. (17) 373-A.42 Drill Sampling and Interpretation of H. T. Matson New York Sampling Results in the Copper G. A. Wallis Feb.. 1931 Fields of Northern Rhodesia (17)

Jan 1, 1930

By Paul Averitt

require both time and money. Any attempt to secure a quick answer will yield a figure that very likely cannot be substantiated, and certainly will not yield information in the detailed form now desired. It will be about 10 years before a completely new estimate can be prepared for the coal reserves of the United States at our present rate of progress, though of course, much information will be available in the interim. We would like to present such information as we obtain in the form most acceptable to the industry, and to that end we are working closely with coal resource committees of the AIME, the National Bituminous Coal Advisory Council, and the Bureau of Mines. DISCUSSION G. H. Cady*—Mr. Averitt's description of the nature of the coal resources investigations of the United States Geological Survey and the progress of this work is very timely in view of the general interest in the subject of coal resources. The Federal Survey is obviously taking the "long view" with respect to the appraisal of the coal resources as part of the preparation of the general geological map of the country and the attendant determination of the quantity of all mineral and fuel resources. It is apparently for regional surveys of the conventional type that the detailed procedures employed by the Federal Survey are applicable. Even if so it is somewhat unexpected to find the same criteria for evaluation will be applied to the country as a whole. The work on coal resources appraisal has been proceeding at various rates in a number of coal producing states for various periods. Undoubtedly since there has been no common practice in the method of appraisal the states each have worked independently and independently of the Federal Survey, and each has adopted certain practices to meet local conditions. I do not know how much consideration has been given by the U. S. Geological Survey to these practices. It seems probable that such consideration might result in important modifications of the standards which apparently have been set up by the Federal group in line with local requirements. It is the practice in some state surveys to present the facts in regard to the occurrence and distribution of coal beds and their variations in thickness down to thicknesses of 1 to 1 1/2 ft in relatively narrow stages up to maximum thickness. It is then possible for any one using such figures to compile quantitative estimates of workable coal at various minimum thickness limits. This is a desirable objective where surveys are detailed and information correspondingIy good. However, vast quantities of coal lie in beds that are relatively thin about which little information is available and the quantity of such coal might affect the final appraisal to the extent of several thousand million, depending upon the minimum limitation observed. Thus in the case of Illinois a difference of 1 ft in average thickness of coal in the coal field would make a difference of approximately 35 billion tons in the estimated quantity present. One is dealing with a very large area and small differences in thicknesses are very irnportant in the overall picture. The estimate of 10 years to accomplish the sort of detailed appraisal outlined by Mr. Averitt is viewed somewhat skeptically and certainly would require many more trained geologists than seem to be available. The requisite detailed mapping and study are very time consuming not only because of the geological field work required, which is difficult in certain seasons, but also in order to assemble data from company and personal files, and to study drill records and cores, and to sample and analyze the coal. Unless the staff of geologists could be increased in the order of several hundred per cent the prospects are that the appraisal of the type suggested will require many decades not just one. The permanent value of such appraisal, however, is not questioned and it should be expedited as rapidly as means allow. Satisfactory appraisal is not easily achieved and will vary from time to time. The main function of a geological survey is to collect and present the facts that will make possible appraisal in terms of existing conditions by individuals, particularly engineers, qualified by training and expcrience for making such estimates. Thickness and character of the coal bed, nature of the overlying and underlying strata, position, thickness, and character of "partings," relationship to other coal beds, and a variety of other factors must be assembled by the geologist in order to present a complete picture of the geological setting. The economic and engineering factors are in general outside the field of geological experience. The geologist should see to it that the pertinent geological facts are available; much more information than simply thickness and depth of the coal beds is essential to meet all the requirements of appraisal in the future as well as at present. With respect to the present demand by engineers and coal mine operators and others for a rapid re-appraisal of the available coal resources, in the light of existing practices and those in immediate prospect, the Federal procedure of systematic mapping and appraisal is scarcely in line. It will be necessary for those particularly interested in having such an estimate made to establish standards with respect to the various factors involved so that the scope of the geological work can be definitely restricted for the various coal fields. There is little use in setting up general standards since no such standards will be applicable to all fields. Thus it is folly to establish a standard minimum thickness to be generally applicable which is one-half to one-third the minimum minable thickness in some fields. The greatest difficulty in appraisal of the presently actually workable coal bed lies in the variation in the importance placed on roof, floor, structural conditions, bedded impurities. sulphur content and other factors that affect judgment relative to the value of a coal bed. It is doubtful whether any appraisal will have universal approval in view of the variable factors involved. For this reason if none other, the facts should be carefully and painstakingly assembled after the manner of a systematic geological survey such as that advocated by Mr. Averitt. Only upon the basis of sucb information can reliable estimates be made in line with selected conditions. Paul AveRitt (author's repty)— In this paper I discussed, but did not define as such, two major phases of our activities on coal, which are closely related, and which normally we in the U. S. Geological Survey see as an integrated whole. It is understandable, therefore, that Dr. Cady should assume that my remarks applied only to the current work on coal reserves with which I am directly concerned. In view of Dr. Cady's discussion, however, I think a brief summary of the two phases of U. S. Geological Survey activities on coal will be appropriate. The long-term function of the U. S. Geological Survey on coal investigations is to make detailed geologic studies, involving the preparation of detailed geologic maps showing the outcrops and correlations of coal beds, direction and dip of coal-bearing rocks, nature and thickness of overburden, location of faults and fold axes, and similar features. Such studies also yield many measured sections of coal and associated strata, which show variations in the thickness of the beds, and the intervals between coal beds. Taken as a whole, detailed geologic studies provide much useful information for mine operators and engineers. As Dr. Cady points out, this type of geologic work is arduous and time consuming, but it provides the basic data that are necessary both in the development of our coal fields, and also in the preparation of coal-reserve estimates, which are discussed in the next paragraph. The U. S.

Jan 1, 1950

By H. W. Winkler, Discussion, V. L. Forsyth

The development of a new gar lift valve has removed many of the obstacles limiting over-all gas lift efficiency. The valve is pressure charged in place in a well, and operating pressure can be changed without pulling. Temperature and gas gradient compensation have been eliminated. Intermitting and constant flow installations, using conventional pressure-charged valves, are compared with designs incorporating the new automatic stabilizer controlled valve. Specific well performance data are presented. The means of obtaining and controlling multiple-point injection of gas are explained and contrasted with single point injection. The effect on small diameter strings and multiple string installations is discussed. The effect of flowing temperature gradient on a design using conventional pressure-charged valves, the limitations imposed by such temperature, and the obvious benefits which result from the use of automatic stabilizer controlled valves are shown. Reduction of gas requirements is stated mathematically and demonstrated with specific examples which are identified as to oil company and well. Increased fluid recovery resulting from greater drawdown is illustrated. The economic advantages are mentioned with emphasis on reduction of capital expenditures, as well as reduction in operating expenses. INTRODUCTION Much of the engineering and research work performed with gas lift has been based upon the supposition that under producing conditions gas would be injected at a single point in a well. Many tests were performed in determining the optimum size of the opening through which gas would be passed and the exact placement of the valve equipment. The objectives in a gas lift installation are to unload the well and to efficiently produce the well after it is unloaded. Until recently, the function of upper valves was simply to unload the well. An operating valve located at a proper place in a well served as a single injection point for lifting liquid to the surface. The basic problem in using such equipment is to arrive at operating depth with sufficient operating pressure to efficiently lift the liquid. Few gas lift installations are designed with all required well data available. However, regardless of the quality and availability of data, and regardless of the accuracy of the design, there is the practical problem of preparing and placing gas lift equipment in the well in exact accordance with the plans and intentions of the engineer. In recognition of these and many other problems, attention was directed toward a means of removing the need for temperature and gas gradient compensation, a way to change the gas lift installation to meet the changing requirements of the well itself, and a manner of compensating for changes in oil-water content, fluid volumes, PI, and bottom-hole pressure resulting from flood or repres-suring activity. A device which could actually set and change the operating pressure of gas lift valves in the well would meet most of these needs. There now exists a new gas lift valve which fulfills the original objectives and in so doing actually accomplishes much more. With this device, called an Automatic Stabilizer Controlled valve, there is an exact matching of valve operating pressure and well conditions. Gas is injected at more than one point in the well, thereby making controlled multiple-point injection of gas a reality. Installation calculations are materially simplified and the need for basic temperature and gas gradient data no longer exists. Section I—The Automatic Stabilizer Controlled Valve The operation of the ASC valve is more easily understood by first studying a conventional pressure-charged valve and then inserting the stabilizer element to observe the changes which result. Fig. 1 is a schematic of a conventional precharged pressure-operated valve. The pressure in the dome pd, acts downward, against the area of the bellows A,, to hold the valve closed. The resulting force Bf plus the spring effect of the bellows Sf represents the total force acting to close the valve. Correspondingly, the tubing pressure ptbg works upward against the port area Atbg and the casing pressure pc works upward against a portion of the area of the bellows

Jan 1, 1965

By Walter Rose

In a recent technical note, Owen Thornton&apos; suggests that wetting liquid relative permeability may be derived from the relationship: where Pd/Pc is the ratio of displacement pressure to capillary pressure at the wetting liquid satdration Sw, and I is the resistivity index at this saturation. Thornton shows that this expression gives values for relative permeability in good agreement with those experimentally determined by Leverett. We have recently developed another expression for krw which seems preferable to Equation 1 since it requires fewer experimental data for its verification. This equation may be derived in the following manner. Making use of the analogy between mass transfer of fluid in a porous medium and electrical conductivity through the fluid in the same medium, we can postulate a hydraulic formation resistivity factor analogous to an electrical formation resistivity factor. From Poiseuille&apos;s Law the resistivity to flow in a tube of radius R is of the form 8u/R², where is the viscosity of the fluid. Similarly7 the resistivity to flow in a porous medium of the same dimensions as the tube is given by D&apos;Arcy&apos;s Law as where k is the permeability of the medium. The hydraulic formation resistivity factor, Ff, is thus the quotient of these two resistivities, or: But permeability is defined by the KO-zeny equation as: where: r is the average pore radius of the porous medium, L. is the average tortuous length of the average pore, + is the porosity, and L is the bed length. This gives Fr as a function of the (La/L) .-.-.tortuosity ratio and porosity, or in explicit form: where: T = (La/L)&apos;, and N is the number of pores of radius, r, which will be found in any cross sectional area, x R&apos;. That is, N = R²/r². It will be clear from the foregoing considerations that the hydraulic formation fat. tor should be dependent on the value of R which in every case must be arbitrarily selected. By analogy, the hydrauiic formation factor, Fcf, characterizing the porous medium at Sw<1,will be given by: R² NT. where ke is the effective wetting liquid permeability obtaining at Sw<l, and Te is the square of the (Las/L) ratio defined by Thornton. Therefore, the hydraulic resistivity index, If, is: However, Thrnton gives I as: and it follows that: Equation 2, when checked against the data of wyckoff and Botset² and some of the Morse et al data³, gives comparisons as shown at the bottom of this page. Computations based on Leverett&apos;s data, quoted by Thorntaon, gives computed krw values somewhat lower than the experimental values. Moreover, other instances can be cited where we find that neither Equation 1 nor Equa tion 2 is checked by experimental data. The work of Botset&apos; on the Nichols Buff sandstone and Morse et a1 on oil wetted Bradford sandstone are such instances. A reason for these discrepancies may lie in the fact that if both Equations 1 and 2 are presumed always to give accurate values for krw, it follows that PC = Pd/Sw". Such an expression, it is well known, is too simple to describe accurately the capillary pressure behavior of all porous media. However, it is believed that a particular advantage resides on the use of Equation 2, since it is not dependent for its utility on a knowledge of the capillary pressures obtaining in dynamic flow svsterns. No practical technique for measuring the capillary pressures characterizing the fluid distributions in dynamic flow systems has yet been proposed. Acknowledgment is given to Dr. Paul D. Foote, executive vice-president of the Gulf Research and Development Company, for permission to publish this note. 1. Owen F. Thornton, "A Note on the Valuation of Relative Permeability," J. Pet. Tech., 1:7, Section 1, July, 1949. 2. R. D. Wyckoff arid H. G. Botset, "The Flow of Gas-Liquid Mixtures through Porous Media," Physics, 7:325-345, 1936. 3. R. A. Morse, P: L. Terwilliger, .and S. T. Yuster, "Relative Permeability Measurements of Small Core Samples," Oil and Gas J., 46:109-125, Aug. 23, 1947. 4. H. G. Botset, "Flow of Gas-Liquid Mixtures Through Consolidated Sand," Trans. AIME, 136:91, 1940.

Jan 1, 1949

By Walter Rose

In a recent technical note, Owen Thornton&apos; suggests that wetting liquid relative permeability may be derived from the relationship: where Pd/Pc is the ratio of displacement pressure to capillary pressure at the wetting liquid satdration Sw, and I is the resistivity index at this saturation. Thornton shows that this expression gives values for relative permeability in good agreement with those experimentally determined by Leverett. We have recently developed another expression for krw which seems preferable to Equation 1 since it requires fewer experimental data for its verification. This equation may be derived in the following manner. Making use of the analogy between mass transfer of fluid in a porous medium and electrical conductivity through the fluid in the same medium, we can postulate a hydraulic formation resistivity factor analogous to an electrical formation resistivity factor. From Poiseuille&apos;s Law the resistivity to flow in a tube of radius R is of the form 8u/R², where is the viscosity of the fluid. Similarly7 the resistivity to flow in a porous medium of the same dimensions as the tube is given by D&apos;Arcy&apos;s Law as where k is the permeability of the medium. The hydraulic formation resistivity factor, Ff, is thus the quotient of these two resistivities, or: But permeability is defined by the KO-zeny equation as: where: r is the average pore radius of the porous medium, L. is the average tortuous length of the average pore, + is the porosity, and L is the bed length. This gives Fr as a function of the (La/L) .-.-.tortuosity ratio and porosity, or in explicit form: where: T = (La/L)&apos;, and N is the number of pores of radius, r, which will be found in any cross sectional area, x R&apos;. That is, N = R²/r². It will be clear from the foregoing considerations that the hydraulic formation fat. tor should be dependent on the value of R which in every case must be arbitrarily selected. By analogy, the hydrauiic formation factor, Fcf, characterizing the porous medium at Sw<1,will be given by: R² NT. where ke is the effective wetting liquid permeability obtaining at Sw<l, and Te is the square of the (Las/L) ratio defined by Thornton. Therefore, the hydraulic resistivity index, If, is: However, Thrnton gives I as: and it follows that: Equation 2, when checked against the data of wyckoff and Botset² and some of the Morse et al data³, gives comparisons as shown at the bottom of this page. Computations based on Leverett&apos;s data, quoted by Thorntaon, gives computed krw values somewhat lower than the experimental values. Moreover, other instances can be cited where we find that neither Equation 1 nor Equa tion 2 is checked by experimental data. The work of Botset&apos; on the Nichols Buff sandstone and Morse et a1 on oil wetted Bradford sandstone are such instances. A reason for these discrepancies may lie in the fact that if both Equations 1 and 2 are presumed always to give accurate values for krw, it follows that PC = Pd/Sw". Such an expression, it is well known, is too simple to describe accurately the capillary pressure behavior of all porous media. However, it is believed that a particular advantage resides on the use of Equation 2, since it is not dependent for its utility on a knowledge of the capillary pressures obtaining in dynamic flow svsterns. No practical technique for measuring the capillary pressures characterizing the fluid distributions in dynamic flow systems has yet been proposed. Acknowledgment is given to Dr. Paul D. Foote, executive vice-president of the Gulf Research and Development Company, for permission to publish this note. 1. Owen F. Thornton, "A Note on the Valuation of Relative Permeability," J. Pet. Tech., 1:7, Section 1, July, 1949. 2. R. D. Wyckoff arid H. G. Botset, "The Flow of Gas-Liquid Mixtures through Porous Media," Physics, 7:325-345, 1936. 3. R. A. Morse, P: L. Terwilliger, .and S. T. Yuster, "Relative Permeability Measurements of Small Core Samples," Oil and Gas J., 46:109-125, Aug. 23, 1947. 4. H. G. Botset, "Flow of Gas-Liquid Mixtures Through Consolidated Sand," Trans. AIME, 136:91, 1940.

Jan 1, 1949

By M. L. Leonardi

THE Searles Lake orebody is located in the north- west corner of San Bernardlno County. It is a dry lake bed with an exposed salt surface covering an area of 12 square miles. Recoverable mineral values are contained in the mother liquor below the surface of the lake. Stratification in the lake bed has separated the brine into two bodies which dlffer in composition. Although liquor is processed from both bodies, this paper will discuss only the upper structure brine. Fig. 1 illustrates a typical cross-section of the two commercial orebodies. The orebody is composed of a porous salt deposit 70 to 90 ft deep. The upper structure is separated from the lower orebody by a 12 to 16-ft thick impervious mud seam, as shown in Fig. 1. These salt structures are composed of 55 pct solid-phase salts and 45 pct voids which are filled with the original mother liquor. The brine wells are drilled to the separating mud seam and cased to wlthin 10 ft of the bottom. This is done to draw the brine horizontally from the bottom of the structure. It is pumped with multistage centrifugal pumps Into the plant at the rate of 3 milllon gal per day. The first process that was successful was developed by Charles P. Grimwood for the recovery of potash. The first evaporator unit was built in 1916. In the early twenties, Dr. Morse worked out a process for the recovery of borax. This made the cycle more efficient, as the end liquor could be sent back to the evaporators rather than being sewered. In 1926 the American Potash & Chemical Corp. was formed as a new company, and the entire plant was remodeled. The plant at that time produced only potash, borax, and boric acid. Since then the American Potash & Chemical Corp. has added processes for the production of USP boric acid, refined potash, sulphate of potash, soda ash, salt cake, lithium concentrates, Pyrobor (Na2B4O7) bromine, phosphoric acid, and lithium carbonate. The main plant cycle may be depicted as a closed cycle, see Fig. 2. The raw material, brine, enters the cycle to be mixed with the end liquor, known as ML2, from the pentahydrate borax crystallizers. The mixture of these two forms evaporator feed. Evaporator feed is pumped to the evaporators where it is concentrated, with respect to potash and borax. In the same operation water vapor, sodium chloride, salt trap salt, and clarifier salt are removed from the cycle, see Fig. 3 for potash plant product. The evaporators produce a concentrated liquor which contains approximately 19.5 pct KCI. This liquor is diluted as it enters the potash plant to keep all salts, except potash (KCI, 97.0 pct) in solution. Here the moist potash leaves the cycle at 100°F. The end liquor, known as ML1, is pumped to the borax pentahydrate crystallizers, where crude borax pentahydrate is crystallized and removed as solid phase. The ML2 is sent back to pan feed to be reconcen-trated, see page 207. Note that the only water to leave the cycle is in the form of vapor and moisture in the solid phase products crystallized. Thus there is a constantly cycling volume of liquor to which brine is added. Since the volume of liquor cycled does not increase, the brine is, in effect, evaporated to dryness. This would be true if there were no liquor losses. But, as in all processes, there are always unavoidable and accidental losses which reduce the volume of cycling liquors. The losses must be made up with brine. The concentration process is the beginning and the end of the cycling liquors. In this process there are three evaporator units of the triple effect counter-current type, that is, there are three pans in each unit and the heat flows in one direction while the liquor flows the other way through the evaporator pans, see Fig. 4. During the evaporation process a great deal of sodium chloride, burkeite, some sodium carbonate monohydrate, and a little lithium-sodium phosphate are crystallized. The volume of these salts is so great that they must be removed as they are formed or the process would come to a standstill. Brine and recycled mother liquor No. 2 enter the third effect evaporator pan from the evaporator feed storage tanks, see Fig. 5. A steady flow of liquor is removed from the bottom of the No. 3 pan and is pumped through the No. 3 cone of the salt trap, a clear liquor being returned to the NO. 3 pan. A portion of this clear liquor is pumped to the second effect pan. This process is repeated in each pan. The liquor from the No. 2 pan is pumped through the No. 2 salt trap cone and returned to the No. 2 pan.

Jan 1, 1955