I;1'DL-STRIAL 4 S D ELYGISEERISG CHEJIIIXTRY
Septeniher, 1926
porcelain or semi-porcelain type of glass pot was a wartime development in America, and it made possible the manufacture of glass types which could not be made in the clay pots previously available. The large-scale manufacture of industrial glass took a step forward when the pot was replaced by the tank, with its more favorable type of construction and smaller proportionate surface exposed to the corrosive action of the glass, and the tank has practically displaced the pot in all but the small-scale operations. But the demand for better refractories still is insistent, and has led in the past few years to more intensive study of the alumina-silica refractories. Here the scientific and technical developments have proceeded simultaneously, and it appears probable that in the mullite refractories we have achieved a n improvement of the first magnitude. The same group of refractories is well fitted to withstand high temperatures, and so will doubtless prove of benefit to other industries as well,
915
Advances in Glass Technology
The researches of Schott, and the progressive policy of the glass plant of Schott and Genossen in Jena, resulted in tremendous strides in glass technology in the last quarter of the nineteenth century, and gave the application of science to the industry an impetus which lasted well into the twentieth century. That impetus was apparently waning, however, and a t the outhreak of the European war the glass industry had apparently settled down into well-worn ruts. Under the pressure of necessity glass technology experienced a new awakening, which is now manifest in all of its branches. There are many signs that we are a t the dawn of a new era in our knowledge of glass, its properties and its constitution, which will surely result in improved glass compositions, improved methods of manufacture, and improved methods of treatment; for that has been the invariable and inevitable result of the application of the scientific method to technology.
Fifty Years of Gas Chemistry' By W. H. Fulweiler THE U. G . I. CONTRACTING Co., PHILADELPHIA, PA.
IFTY years ago the gas industry was devoted almost exclusively to illumination. There were a few rather crude stoves used for domestic cooking. Electricity had not appeared as a competitor and state commissions were still unknown. The illuminating value was the standard of quality and but little attempt was made to sell gas as a commodity. Since then there has been an almost complete revolution in the industry. Today probably less than onethird of the gas is used for illumination, the greater portion being used as a most convenient and efficient, source of heat in the home and for thousands of manufacturing operations. The illuminating value has disappeared as a standard of quality and has been replaced by the heating value, a change which started in Wisconsin in 1908. I n nearly all our states regulations concerning quality, service, and rates are under the supervision of state commissions. and practically every company has its new business department endeavoring to extend the use and to increase the sale of gas. The sale of gas per capita in the United States has increased about four times faster than the population, while the average price has been reduced from about $2.30 per thousand to a little over $1.00 per thousand and the average standard of quality has been changed from 16 candlepower coal gas to a 550 B. t. u. mixed gas. Sl'here formerly the companies in our various cities were individual organizations, today many of them are linked together by holding companies, with a resulting increase in the efficiency of management and operation.
F
Manufacture of Gas
Practically all the gas was formerly produced by the carbonization of coal, as carbureted water gas was just being introduced, while today this condition is reversed and the greater proportion is carbureted water gas, which is sold either alone or mixed with coal gas. I n the manufacture of coal gas the general trend of development has been towards the carbonization of coal in larger units and to a reduction in the labor required to effect this carbonization. Where coal gas was formerly made in 1
Received July 27, 1926
9-foot horizontal retorts holding 300 to 400 pounds of coal we have today coke ovens holding 10 tons per charge. Practically all the operations of handling the coal, charging i t into the retorts, and removing, sizing, and storing the coke are performed mechanically. The small individual producers for heating the retorts have given way to the large external producer serving a whole battery of retorts. The sensible heat that was formerly wasted in the products of combustion is now recovered in the waste-heat boiler and the hot coke is cooled in apparatus which permits recovering the heat as steam and produces a better quality of coke. Water Gas
The period under discussion has practically furnished the history of the development of the manufacture of carbureted water gas. With the exception of the Lowe process, the earlier processes have disappeared, and our modern carbureted water-gas apparatus has been developed to a very high degree of efficiency. The apparatus is operated by an automatic device, the steam and air are accurately measured, and the temperature is automatically controlled. The self-clinkering grate is just emerging from the development stage, and waste-heat boilers will furnish steam sufficient to operate the process from the sensible heat in the off-going gases. Bituminous coal can be used as fuel with the Pier process and heavy coke-bearing oils can be used in the checkerless carburetor, so that the high capacity and great flexibility of the process, low labor cost, and relatively abundant supply of enriching oil have all aided to make the manufacture of carbureted water gas the most generally used process. The development of the all-oil water-gas process as used on the Pacific coast has taken place during the period under discussion. This process, however, does not appear to be economical under the conditions prevailing a t present on the eastern seaboard. We cannot mention all the changes that have taken place in the condensing and purifying processes, but we can point out that with the change to the heating-value standard more
946
I - D U S T R I A L A N B ENGINEERING CHEMISTRY
rapid methods of cooling are in use. High-duty tubular condensers and the direct-contact type of washer cooler have been among the more recent developments. The Cottrell electrical precipitator for the removal of tar is one of the very promising recent inventions. The removal of the benzene homologs from gas, which is now compulsory in France and Italy and which was introduced very widely in this country during the war for the recovery of toluene, is still in use in some plants. I n this country, however, the oil-washing system has been most generally used in spite of the work being done on the use of activated charcoal and silica gel. There has been but little change in the methods or apparatus for the recovery of ammonia beyond the introduction of the direct method for the recovery of ammonium sulfate, which is in use in large plants. There is a great deal of interest in the possible substitution of gypsum for sulfuric acid in the manufacture of ammonia sulfate. The naphthalene problem, which was formerly one of the great difficulties in the operation of coal-gas plants, is now better understood and can be completely controlled by suitable scrubbing. The recovery of cyanogen from coal gas is another development of more recent times, but the present market value of cyanogen compounds has greatly reduced the possibility of profitable operation in this country. Lime was in general use for the removal of the sulfur compounds in gas, but was replaced by iron oxide with the more general introduction of water gas. There has been a great improvement in the design of purifiers, of the oxide itself, and in methods used for handling and revivifying the fouled oxide. At the present time the possibility of liquid purification is receiving considerable attention. I n one system the sulfur is recovered as free sulfur. There is still room for improvement looking to a reduction in the cost of operation. Practical trial is about to be made of the use of oxide in the dry powdered form. Whereas the earlier lime system of purification removed the carbon bisulfide, which forms the bulk of the so-called organic sulfur compound in gas, oxide of iron used as a purifying agent removed only the hydrogen sulfide, so that several processes have been developed for removing these fixed suifur compounds. These generally involve treating the gas with a catalyst which decomposes the carbon b i s u l f i d e a n d forms hydrogen sulfide, which is removed by a s u b s e q u e n t purification. Venturi and electrical metering devices are replacing the expensive drum type of s t a t i o n m e t e r . The waterless type of holder has been developed to r e p l a c e the very expensive type in which t h e gas is confined over a large tank filled with water. The waterless holder consists of a piston floating in a cylinder formed by the outer shell and i s r e n d e r e d gas-tight by a tar seal along the sides, any leakage beApparatus for Manufacture of Blue ing c o l l e c t e d a t the
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bottom and pumped back automatically to the top of the holder. The use of high pressures and the small steel mains in the distribution system is a modern development. I n some cases the pressures used are as high as 60 pounds per square inch and the mains may extend over 100 miles, thus permitting the supply to communities that would be impossible under the old system using lower pressures in cast-iron mains. Great advances have been made in the knowledge and manufacture of refractory materials so essential to the industry. The use of silica material for the high-temperature portions of coal-gas apparatus is almost universal. Improvements have been made in the linings for water-gas apparatus. The use of water-cooled linings will probably solve some of the more difficult problems. The change to the heating-value standard has eliminated the most of the condensable hydrocarbons from the gas, and this has resulted in greater corrosion in pipings, fittings, etc., and to apparently more rapid deterioration of meters. This subject is receiving a great deal of consideration a t the present time. New Gasification Processes
Among the newer processes that are receiving attention
at this time is that of low-temperature carbonization. While it was well known that certain types of coal could be distilled a t relatively low temperature for the production of “coal oil,” there was but little interest in the production of large quantities of liquid products, but about 1900 work on the effect of varying temperatures on coal was started by Parr in Illinois, and since that time a great deal of experimental work and many processes have been devised which involve the production of relatively large quantities, 15 to 20 gallons per ton of tar oils, with a smaller yield of gas of relatively high heating value and a coke that is more readily combustible than the coke hitherto produced. Much of this interest has been the result of the World War, which emphasized the desirability of a national supply of liquid fuels. The complete gasification of coal in a single vessel has also received a great den1 of attention, but the results have not been of great promise when we consider that the use of bituminous coal in the water-gas generator is, practically s p e a k i n g , t h e equivalent of complete carbonization. The use of oxygen in the gasification of coal is an interesting possibility for future development, as i t would m a k e t h e water-gas process c o n t i n u o u s . The difficulty due to the high cost of producing oxygen with our present apparatus has n o t y e t been solved, but a great advance has been made in the effic i e n c y of separating oxygen from the air by fractional distillaGas Provided with Waste Heat Boiler tion.
September, 1926
INDUSTRIAL A S D E-VGINEERING CHEMISTRY
There are a number of proposals for methods of utilizing oil as an enriching agent other than in carbureted watergas apparatus. One of these proposes to crack the oil in tube units, thus producing gasoline and a fixed gas of relatively high heating value. It is claimed that in this system there is a greater net return, considering the present high market value of gasoline, than where the oil is cracked in the usual apparatus. Another proposal having t o do with the enrichment of gas is the transformation of the carbon monoxide in blue gas into methane by the addition of hydrogen in the presence of a catalyst. An economic difficulty is the fact that there is loss of heating value of about 20 per cent in the reaction. The process has interest, however, in that it does permit the production of a gas a t any required heating value without requiring the use of oil, so that the commercial possibilities of the process are entirely dependent upon the relative cost of the coal and oil. TVithin recent years the large demand for hydrogen for various purposes has stimulated the development of several processes for producing hydrogen either from blue water gas by reaction of the steam and the catalyst or by heat treatment of coal gas. A great deal of thought and study is being given to the determination of the most efficient quality and composition of gas having in mind the requirements of great flexibility in send-out (as a result of the more extended use of gas for house-heating) and freedom from the use of oil for enrichment.
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The heat quantities involved have been studied and the general effect of temperature is now well understood. This work is intimately connected with the study of decomposition of pyrosynthesis of hydrocarbons under the influence of temperature, pressure, and time, and the earlier theories proposed by Bertholet had given way after the work of Haber, Wheeler, and Whittaker and his pupils. While much progress has been made, there is still an enormous field for further work, particularly in the application of our theoretical knowledge through the reactions as they occur in commercial practice where the large number of variables involved renders the experimental investigation extremely difficult. Improvements in Analytical Methods
The analytical methods as applied to the gas industry were well founded fifty years ago and our work since then has been primarily a refining one. There has been little change in the methods for the ultimate analysis of coal, but in the proximate analysis the method of the AMERICAN CHEMICAL SOCIETY has been quite widely used and it is regretted that the Fuel Research Board has found it necessary to introduce the determination in nitrogen.
Coal Investigations Important to the Industry
The past fifty years have been very fruitful in the work that has been done on many of the problems involved in the constitution of coal, the reaction involved in carbonization, and the decomposition and pyrosynthesis of hydrocarbons. While it is true that the foundations for many of the present views had been laid by the early workers, yet there were many points that were not well understood. Unfortunately, the gas industry can reap but little direct benefit from the vast amount of work that has been done on the constitution of coal. Investigations on the use of solvents, particularly by Wheeler in which he has indicated the existence of alpha, beta, and gamma constituents in coal, and the work of Parr and Fischer and others have been of assistance in explaining coking qualities. The study of the coking index that has been carried on since Richter’s early experizents, it is believed, will yield valuable results when applied to our American coal, and we should mention the interesting work that is being done by Lessing and Cobb and his pupils on the change in the products of heating coal by the addition of inorganic materials. The work of Parr and Powell on the occurrence of sulfur in coal has also been of value to the gas industry, and that of Parr and Audibert on the fusion point of coal may lead to useful results. We have little new knowledge regarding the effect of the ultimate composition of the coal on its gas-making qualities. Parr’s suggestion of classifying coal on the basis of the heating value of the so-called “unit coal” has been of assistance. Our knowledge of the mechanism of the carbonization of coal is practically all due to the more recent work, particularly since 1900, when Parr and his students commenced a study of the lowtemperature carbonization of coal. Thanks to the work of Parr, Porter, and others of the Bureau of Mines in this country and of Wheeler and Cobb and their students in England, we now have a much clearer picture of the reactions that occur in carbonization.
Modern Multiple-Pass, High-Duty Tubular Condenser
Improvements have been made in the technic and apparatus for the determination of heating value. One new development has been the standardization of methods for the determination of the softening point of ash, and this has served a very useful purpose in the selection of coals,. particularly where the coal or the coke made from it is used in the manufacture of carbureted water gas. The methods for the determination of ammonia have been little changed. The rather difficult determination of cyanogen has now been standardized. The development of accurate methods for the determination of naphthalene has aided in the solution of this vexatious problem. Brown has recently shown that indene and other hydrocarbons will affect the accuracy of the picrate method. The electrical method for the determination of naphthalene has been of great assistance where large numbers of determinations have to be made. The use of activated charcoal has been of great value in the determination of the light oils in gases. I n gas analysis we have seen the development of the Hempel type apparatus and the more recent development of the Bureau of Mines type, which permits a great saving of time in the making of an ordinary analysis. Many modifications of the reagents have been studied, but in the main there
INDUSTRIAL A N D ENGINEERING CHEMISTRY
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has been little change. I n this connection we should mention the work of Dennis and his pupils. The use of the slow combustion method for the determination of paraffins has almost entirely replaced the explosion method. It is well known that the ordinary method that is now practiced does not differentiate either the olefins present in the illuminants or the various members of the paraffin series which are ordinarily known as methane and ethane. Burrell’s work on the liquefaction and subsequent fractional distillation of the gases a t low temperature has
Vol. 18, No. 9
furnished the basis of a method that i t is hoped may result in commercial development. Tropsch, in Fischer’s laboratory, has devised a n apparatus in which it is said that a determination can be made in a day and it is hoped that future work will make it possible to reduce this time still further. I n view of the great technical advances of recent years and with the more wholesome public relations that now exist, the gas industry looks forward to the future as holding a greater promise than the past.
Paint and Varnish-Yesterday, Today, and Tomorrow’ By Maximilian Toch 443
FOURTHAvE., NEW YORK,N. Y.
T
HE earliest records in existence are those of the Egyp-
tians, who forty-five hundred years ago used about seven pigments and mixed them with lime and water for decorative purposes. With the exception of two, these were natural earth pigments-ocher, whiting, hematite, charcoal, and lampblack. There are some evidences that the Egyptians used powdered minerals, such as malachite, and the only artificial color that they applied was a material called fritts, which was powdered porcelain or glassware that had been colored with cobalt oxide. A thousand or fifteen hundred years later, when interior decoration was practiced, the Persians and the Egyptians used white of egg and boiled parchment as adherents for pigments. I n the ruins of Pompeii there are remnants of two paint shops, showing practically the same colors, excepting a red known now as Pompeian red, which was supposed to be a natural cinnabar. Oils
I n 1399, the Brothers Van Eyck published the information that decorative paint could be applied with a drying oil. It is conceded that this drying oil was linseed oil and for five hundred years practically no other oil was used on a large scale. To be sure, poppy oil was used in portrait painting, but its drying qualities are different than those of linseed oil, and today we are able to identify portraits that were painted with poppy oil because the crackle is much smaller than that of other drying oils. Up to 1900 or practically five hundred years after the invention of the Van Eycks, other oils, notably China wood oil, began to come into the paint and varnish industry, and last year some fifteen million gallons were used in a raw state, which would indicate that between thirty and fortyfive million gallons of paint and varnish were made of this very remarkable oil. The Chinese have been using this oil for centuries, never in its raw state, but always gently cooking i t until it became thick; but in America methods were discovered for producing waterproof paints and varnishes that had never been known before. I n addition t o this oil, large quantities of three varieties of fish oil are used. Soy bean oil has come to be constant, particularly for baking japans. Perilla oil is of great value for certain enamels, and corn oil, rape seed, and sunflower seed oil are regarded as drying or semidrying oils and can be used as substitutes. I n fact, the great demand for oil paints during the war, and the dearth of linseed and China wood oils brought out the fact that there are many drying oils which have a practical value. 1
Received June 4, 1926.
Pigments
For ages the only white pigment was white lead. Within the last seventy-five years zinc oxide has run a close second, and within the last twenty years lithopone, which is a barium sulfate-zinc sulfide double precipitate, has been used in such large quantities that the combined use of zinc oxide and lithopone is considerably greater than that of white lead. White lead, however, has its place and is a most excellent pigment, but for interior flat paints and for enamel paints zinc and lithopone are superior. Recently we have had titanium oxide precipitated with barium sulfate, which has even greater hiding power than white lead, but cannot as yet be used alone as an exterior paint. Antimony oxide is another new white pigment, but it is used abroad to a greater extent than in this country. Cadmium separated in the purification of zinc is now precipitated as sulfide, together with barium sulfate, making a cadmium lithopone that is permanent to light and heat and reasonable in price. The same progress is true of the organic lake colors. We have permanent reds now ten times stronger and infinitely lower in price than quicksilver vermilion. No one knows when an oil paint has become absolutely dry, because by the time it has thoroughly dried it probably has perished. This is because the catalytic action continues and i t is the cause of the decomposition of most paints. Lacquers
Five years ago hardly any ‘one thought of using a nitrocellulose lacquer composed either of scrap movie film or condemned large-caliber rifle powder, or directly nitrated cotton, but since that time, it is no exaggeration to state, millions of gallons of automobile lacquers have been used. The one great advantage of lacquer is that when it is dry it is completely dry and no further oxidation or catalytic action takes place. Lacquer, however, must today be applied by means of a spray under heavy air pressure, but the results obtained are marvelous for gloss, water resistance, and wear. But tomorrow there will be thousands and thousands of various sized cans on the market containing lacquer which can be brushed on, which will dry in half a n hour, and which will give infinitely greater satisfaction than any of the old-time enamels. These will not be pure nitrocellulose, nor will they be the amyl and butyl solvents usually used for spray purposes. The chemist has already found large varieties of solvents heretofore unused and hardly known, and scores of combinations of various resins are mixed perfectly with nitrocellulose solutions. As a first step the householder
