INDUSTRIAL AND E-VGINEERI-VG CHEMISTRY
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Vol. 19, No. 5
LIME SYMPOSIUM --
Papers liresented liefore the Division of Industrial and Engineering Chemistry a t the i3rd Meeting of the American Chernwal Society, Richmond, Va., April 11 to 16, 1927
The Problem of the Lime Industry’ James R. Withrow CIISMXCAL ENGINEBRING DEPARTMENT, T H E OHIOSTATB UNIVERSITY, COLUMBUS, OHIO
H E purpose of this symposium is to call sharply to the attention of the lime manufacturer (1) that there is a chemical industry; (2) that the chemical industry is permanently and irrevocably interwoven with our industrial development; (3) that while many ways of meeting coilstruction demands exist which may or may not affect the demand for lime, the construction business is after all a seasonal dne, while the chemical industry on the whole knows no seasons; (4) that this chemical industry has innumerable variations in its nature and raw material demands; ( 5 ) that the lime industry or any other industry will be well repaid for the time and effort spent in studying the raw material needs of the chemical industry; (6) that the chemical industry cannot consume any old kind of lime; ( 7 ) that to get the business which should come to the producer of the lowest cost alkali, the lime maker must study his consumer’s business, as every other chemical industry does, for the lime industry is a chemical industry. It is also the purpose of this symposium to call sharply to the attention of the chemical industry and of chemical workers (1) that the lime industry is also a chemical industryperhaps the oldest chemical industry; (2) that as a chemical industry it has all the problems and grief which make the life of the chemist and chemical engineer one long achievement in overcoming obstacles; (3) that therefore the producers of this most fundamental and lowest cost alkalilime-must get all the chemical cooperation the chemical industries can give, but also such price support as will insure the maintenance of essential standards of raw material effectiveness. Early Solutions of Lime Problems
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Lime production is an ancient art. I n common with other art it helped teach us modern chemistry. How long before the Egyptians and Hebrews the art of lime production was practiced we do not know. We do know, however, that the action of “alchemistry” and the “arts” upon each other led to the classic work of Black upon the relations between calcium carbonate, carbon dioxide, and lime. This cleared up in a modern sense the fundamental chemical principles underlyiiig lime production. Black’s first investigation after he graduated from the University of Glasgow, Scotland, under Cullen, was to discover the cause of the difference between limestone and lime. He lived between 1728 and 1799, and this problem was not only a difficult one for the existing status of the scientific method, but one of lasting fundamental importance in the industry. The old theory was that lime received its caustic properties from fire. It was thought that this causticity, obtained from the flame by which the lime had been burned, was then communicated by lime to the alkalies commonly made by the use of lime. By skilful work, Black showed the part played by carbonic acid gas in the change from limestone to lime, 1
Received March 29. 1927.
and he is therefore regarded as the discoverer of carbon dioxide. Black contributed other researches of importance to the lime industry, and also of greater importance to engineering in general. His brilliant discovery of latent heat was one of these. James Watt was his pupil and friend, so that the lime industry was early connected with important engineering discoveries and developments, as well as being present at the birth of modern chemistry and physics. The Problem of an Industry The problem of an industry is to meet the market demand for the product of that industry at a profit. Two points of view present themselves in this statement: (1) The business must justify investment. There must be a market sufficiently interested in the product to pay for its cost with (2) The a reasonable margin for profit to the producer. product must meet the market demand-must be satisfactory. The first point of view cannot become important until the major problems of the second are solved. Many problems will remain with the first after reasonable solution has been reached regarding the second. Developments in the one phase of this problem profoundly affect the other and neither can stand independent of the other. Failure to recognize this results in low profits or eventual disaster. The technical man cannot afford unduly to increase the overhead for research, engineering, or production costs. Neither can the financial and business end afford to neglect insurance against the future by adequate and constant research, even though all immediate problems may appear t o be solved. The business side cannot afford to dispense with the service to the customer involved in following up the use of its product in the market and even stepping over into solution of the other man’s problems. Wise manufacturers in the chemical industry have long observed that theirs is essentially a service industry and not the mere furnishing of products. The only use for these products is service; when those t o be served are in trouble from whatever cause, even though not connected with the chemical product, the condition is not healthy for our product. I n view of these facts, the chief purpose of this Lime Symposium will be to focus attention upon the problems of production in the lime industry. Problem of the Lime Industry The problem of the lime industry is to produce satisfactory lime at a profit. Does this statement tell the whole story? Is lime always the same? By no means. If all limes were alike, then the field for the sale or use of lime would be immediately defined. The business would be correspondingly limited and the problems of every one of us would be greatly simplified, both on the business as well as on the technical side.
May, l92i
IAVDUSTRIAL A N D ENGINEERING CHEXISTR Y
Siuce iiu twu limes are alike and even limes with practically identical chemical composition vary greatly in physical and other properties, require different handling in production, arid behave differently in the hands of the consuming industries, the problem of the lime industry is not a simple one. Zndless investigation will always be necessary with changing raw material and increasing demands for production, in addition to the normal engineering struggle toward perI'ection in production. The same situation will hold in every oonsurning industry, for a change in the quality of lime, either physical or chemical, may profoundly affect its value to the given industry. There is a corresponding benefit to the linie industry in spite of these difficulties for the very differences in the limes give opportunity for service to the most contradictory demands. The problem of the lime industry, then, has many phases or subdivisions. The obviously endless complexities of these minor probleriis may be divided into the following categories: Problems of the market and of the economics. Problems of the chemistry which can be utilized to meet I)oth the market and economic situation. i.3) Engineering which is made necessary by: ((LJ The chemistry utilized. ( b ) The market and economic situation. (1) 1.21
Every industry struggles with a similar situation. One method of conquering this situation is the adoption of exacting specifications. Specification
This is the era of siniplitied practice. The leadership of our great engineering Secretary of Coinmerce, hh. Herbert Hoover, in this matter is everywhere felt. The plowing, before this harvest, came through the earlier work of chemist and engineer on exacting specifications in the various industries. As a result of high diversity of the use of lime, particularly in highly specialized markets, the required properties varied from customer to customer. The first standards were adopted after niuch labor. The leader in this work was the American Society for Testing Materials. The Committee on Lime from the Industrial Division of the ,1MERICAN CHEMICAL SOCIETY was formed to cooperate with the A. S. T. M. The Bureau of Standards and the Kational Lime Association have also been active. The government Interdepartmental Conference on Chemical Lime during the past several years developed standard specifications. Eleven such have been issued up to June, 1925. These iunction as federal specifications and are also fundamental specifications for government manufacturing departments. The growth of the requireinent of purchase under specification has benefited both producer and consumer though causing much trouble, during development, for both. The manufacturer probably is benefited most, by well-developed specifications, so that he knows what is expected of him beyond peradventure. He can therefore figure costs accordiiigly and can meet with codidence any difficulty which the product encounters in the hands of a consumer. Problems of Market and Economics The problems of the market center largely around the uses to which lime is put in the arts. This meanstwo main markets-construction trades and the chemical industry. The problem of the economics of the lime industry centers around the fact of locality and availability of limestone occurrence, transportation to market, the cost of fuel, ,and, above all, the handicap of abundant and cheap raw material with superficially similar product and the psychological night-
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inare that everybody tliiiiks lie can make lime and believed it should therefore cost nothing. As a matter of fact, scarcely two limestone deposits are alike by nature. Situation and relation to markets still further complicate the matter. Obviously, investment in quarry and plant will vary within several hundred per cent per unit of production as with the utilizing of any natural resource. The influence of such an investment situation profoundly affects the economics of the situation and the extent of service which can be rendered to the market. Hydrated lime production is a problem-solution development which has greatly eased the general market problem. Utilization of spalls or their prevention are types of economic problems. The plasticity problem, rate of settling, activity, modification by burning conditions are all essentially market problems in that they determine the serviceability of the product. Increased knowledge of the properties of lime is doing a world of service in solving market problems. The whole lime industry profits by every such research which is conducted. Some of the papers in this symposium describe the market demand for lime or a few of the most important uses-important either because of volume or because of the service which the lime renders even if the volume is small. The National Lime Association has published an astonishingly large list of users and uses of lime in the arts. Problems of Chemistry The problems of the chemistry of the lime industry center around the fact that the liberation of carbon dioxide gas from carbonates, such as those of calcium and magnesium, to form lime is an endothermic reaction, and also that impurities in the stone may enter into such chemical changes that the physical properties of the resulting lime may or may not be thereby affected. The chemistry is therefore hightemperature chemistry, in which fusion must be held in check. The fundamental chemistry of lime preparation from calcium carbonate having been definitely settled and simplified by the researches of Black, practical lime production keeping these fundamentals clearly in mind can scarcely go astray. While it is true that lime production depends upon the chemical reaction or, rather, a series of reactions, the conditions of these reactions are so well understood that it could readily be maintained that there is no chemical problem in the lime industry. Also the conditions for the carrying out of these reactions lend themselves so readily to wellknown engineering means that as a rule no chemical complications arise from the adoption of these engineering devices. However, as happens even in the case of industries not directly based upon chemical reactions, it would be a mistake not to utilize chemical attention to the running of the lime business. For instance, it is well known that ordinary sugar or sucrose is not prepared by the chemist in the laboratory by chemical reactions. We long ago learned, however, that chemistry could be of great value in the manufacture or production of sugar. Chemistry furnishes two types of service in such a case-(1) the prevention of losses or wastage of a chemical nature which might occur during handling or manufacture; and (2) continuous control of manufacture for the furnishing of information as to the condition of the product at any stage of the process, thereby preventing heavy financial losses a t unexpected times as well as the constant small drains or losses which eat up profit. So too in the lime industry there are problems where chemistry can be useful. The main chemical problem here is the complete burning of the lime in such a way as not to overburn it. While this burning operation has been largely turned over to engineering de-
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vises or rnetliocls, this very fact will probably be ultimately found to be connected with the difference between success or failure in the application of many limes for specific uses. Even the solution of such a sensitive and elusive problem as plasticity will probably be eventually found to lie in a better chemical understanding of the changes which can or do occur during lime-burning. Obviously, there are a host of chemical problems which arise in connection with the use of lime in the various industries. The ground has only been scratched in this regard. The consumer has too long insisted upon paying no attention to lime because he considered it a crude raw material, cheap, and having properties which could not be modified and which must be accepted as it came, with such regret or satisfaction as its use brought forth. Anyone familiar with engineering would realize that the adoption of any engineering device in such a business raises a series of chemical questions. Progress has been made in the absence of chemical consideration only because much ingenuity has enabled us frankly to ignore what should really have been studied. Some kind of result has been obtained and production maintained, in spite of the lack of proper answers to questions of a chemical nature. Problems of Engineering
The problems of the engineering of the lime industry cluster around the engineering operations of mining, quarrying, transporting, crushing, sizing, calcining, cooling, minimizing atmospheric and moisture contact in storage and transportation, and conditioning for service. The industry is essentially a furnacing or fuel-consuming industry. Always the engineering secures results where suitable phenomena are available. Sever, however, do we remain long content with a given engineering solution to any question. The market and the economics continually raise new questions and force engineering development. ilny change in chemical process abruptly changes the engineering to carry out that chemistry. Often where we reach chemical limitations engineering skill enables us still to make progress. We must not forget, however, that when we reach engineering limits in the solution of our problems, frequently utilization of chemical. phenomena and methods will piece out where engineering falls short. I t is this see-saw in the utilization
or pitting against each other of cheniktry a d engineering which has given us our great industrial development. The development of the explosive industry illustrates how chemical methods have enormously lightened the engineering load in limestone-quarrying problems. S o w thn question of open-pit versus drift-mining is being fared and changes the whole situation, even as to explosive result,s, for fines will doubtless increase in volume. Se1ect)ing of stone by hand loading is so valuable in this industry that engineering economies are not desirable. The major engineering problems center around calcination. The question of kiln design is always moot. JVe continually get clearer ideas on this question, but we also develop the complication of the influence of the ultimate use of the lime. So there are still many open questions in kiln design, including the important one of low fuel economy. Kiln design and kiln efficiency still need chemical as well as engineering attention. Rotary kilns and sintering niachines give promise of a real future. The use of steam, carbon dioxide, and air in calcination is also moot. The growth of lime hydrate manufacture has eliminated many problems. The prejudice for lump lime against pulverized quicklime because of impurities in the lime and great liability t,o air-slaking is also thus overcome. Solution of the Lime Problem
The solation of the lime problem is well underway. It seems entirely solved in the case of many manufacturers and some consumers. Like every major chemical manufacturing problem, however, new phases of the problem or new questions must continually be faced. Raw material changes, transportation factors, changes in the consuiiiers' requirements-all make an endless job for the lime mariuf acturer . This symposium mill give an insight into the progress that has been made in the solution of various phases of the lime problem by a few of the thinkers and workers in this No one of them imagines that his job is completed. field. The problem of each, however, is not t'o produce any lime, but to produce the quality of lime which the market needs. The chemical industry constitutes an important and highclass portion of the market demand for lime.
The Consumer, the Market, the Lime Business, and the Chemical Industry' By Charles Warner LllARLbS 1vARh.E.R
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HIS syiiiposiuin reprebents a noteworthy effort t o bring to light more information and likewise to disclose the extended lack of information and the misinformation bearing upon this cheapest alkaline base with its hundredodd applications in the chemical industries. Even with the awakened interest and extensive research efforts of the past few years, bearing upon lime in its ramified uses, few seem to see that we are dealing with a situation involving thousands of possible combinations, though most of us realize that we are only just beginning to learn some of the really important and vital characteristics of lime which so considerably influence its satisfactory and ecoiioiiiical ure.
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Variations in Lime
There was a time when most industries thought they had learned all that it was necessary t o learn about lime for their 1 Received March
24, 1027
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particular purposes ~vlien t,liey hat1 secured the cliemical analysis and the price. Today we are just beginning to appreciate that there are many physical variations in thc different limes and their products due to differences in thc structure of the original rock, in the methods of burning. and in the manner of its slaking or hydration, which will cause wide variat,ions in its adaptability to the many industries now using it mea raw material. The same lime rock, sized and burned in two different ways. both methods being standard practices 'in various plants in this coli shown a difference of 40 per caent i n the effective1 use in a specific industry, and t,his in spite of the fact that, the high-efficiency lime showed by chemical analysis 2 per cent less available oxides. In many industries lime has not received the study it should have t o determine the particular characteristics needed for maximum benefit. This has probably been due
