September, 1928
I S D CSTRIAL A S D EiVGINEERING CHEMISTRY
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Alternative Methods of Blue Gas Enrichment' R. V. Kleinschmidt ARTHLRD . LITTLE, IHC.,CAMBRIDGE, MASS.
ATER gas manufactured from solid fuel, such as gas per gallon having a total heating value of 100,000 E. t. u. coke, anthracite, or bituminous coal, and enriched This is rather more than is usually obtained in practice a t the by hydrocarbon vapors of high heating value, is present time from the partially cracked oils that are on the the most important form of manufactured gas in this country. market, so that the figures given favor present practice as Its widespread use is due to the flexibility of the process against any of the newer methods considered. and equipment which makes it possible to vary within wide The second enriching material which will be considered limits from hour to hour, if necessary, the amount of gas is coal gas. We shall assume for purposes of comparison that produced and to adjust closely the heating value of the gas. a good grade of gas coal will yield 5 cubic feet of 600 B. t. u. The standard operation until a short time ago consisted in gas per pound and 0.7 pound of coke. Low-temperature using coke for generator fuel and a straight-run gas oil which carbonization processes produce a gas of higher B. t. u. conwas cracked on hot checker brick in the carburetor and super- tent and consequently of greater enriching value. The K. S. G. process is expected to heater. This equipment has a good heat balance and is produce a gas of a t least Proper cooperation between oil refineries and gas 750 B. t. u. easily controlled. works would be of benefit both to the oil refineries and A third material which is In recent years the crackto the gas works. Such cooperation would result of considerable commercial ing of gas oils a t refineries in replacing a large percentage of the gas oil, now importance a t the present has resulted in a steady deused for enriching the gas, by refinery gases. The use time is natural gas, which terioration of the material of liquid butane depends largely on freight rates, which may be considered for the a v a i l a b l e for gas enrichat present are too high to permit its successful compresent purpose as having a ment, a large part of that depetition in the great gas-oil market of the northeastern heat content of 1000 B. t. u. livered to the gas works havsection of the country, but make it attractive to cerper cubic foot. ing already passed through tain scattered districts and to the gas-oil markets of the A very important matea preliminary cracking operMiddle West. Gas works of considerable size which rial to which attention will ation. At the same time are so situated that gas oil is still their best enriching be directed consists of the studies of the petroleum-rematerial should give careful consideration to the gases which are given off fining industry show that possibility of using vapor-phase cracking processes in during the process of refining large quantities of o t h e r order to obtain the maximum value of products from p e t r o l e u m both from the petroleum fractions are now the oil which they use. The use of coal gas mixed with initial crude stills and from being treated as waste proda small percentage of water gas and the sale of coke cracking operations. These ucts, which w i t h p r o p e r promises to increase in the northeastern district, gases vary in amount from handling could be made of thereby cutting down the amount of gas oil used. 30 cubic feet per barrel of great value to the gas inIn general, closer cooperation and more elaborate crude oil for a skimming dustry in replacing gas oil. refinement of petroleum products at the refineries to plant up to 250 feet per The recent development of yield ultimately useful products will be of advantage barrel in coke stills and the by-product coke ovens and both to the1oil companies and to the gas industry. same or greater amounts continuous vertical retorts f r o m c r a c k i n g processes. and the installation of a They vary widely in comcommercial plant for lowtemperature carbonization by the K. S. G. process have position and heating value on account of the wide variaalso turned the attention of the gas industry again to the tion in refinery practice. R e shall. however. consider that use of coal gas. This development has been hastened by when these gases have been stripped in a modern plant they the gradual recognition on the part of the public that gas have a heating value of not less than 1200 B. t. u. per cubic coke is a more dependable domefitic fuel than anthracite foot and might easily run as high as 1500, or even 1800, if the gases are not stripped of their butane and pentanes. coal. The possibility of releasing the gas industry entirely from I n this connection also a vapor-phase cracking plant may its dependence on the petroleum industry, with its uncertain be operated in conjunction with a gas works to give a high and rapid fluctuations in prices, has led to the study of so- yield of gas for enrichment and a controllable amount of gasocalled direct enrichment of blue gas by catalytic condensation line, which on account of its high antiknock properties can be readily sold to yield an attractive profit. of its constituents to form methane. Good discussions have appeared in the literature on each We shall consider, fifth, the very light fractions of natural of these possible substitutes for gas oil. There has, however, gasoline which are now being placed on the market as G. E. been no careful study of the relative conditions under which gasoline, and which are to be regarded chemically as mainly these various processes could be used advantageously. butane and isobutane with more or less propane and pentane according to the grade. This material is not only produced Enriching Materials during the process of stabilizing casinghead gasoline but is Among the available enriching materials is gas oil, which also stripped to some extent from the refinery gases mentioned will be the standard of comparison, and for purpose of illus- above. It has the highest B. t. u. per cubic foot of any hytration will be considered as giving 65 cubic feet of enriching drocarbon vapor that is commercially available a t the present time for gas enrichment. 1 Presented before the Division of Gas and Fuel Chemistry at the Finally, we have the direct production of methane by 75th Meeting of the American Chemical Society, S t . Louis, M o , April 16 It0 19,1928. catalysis from the blue gas itself. Professor Haslam stated be-
W
INDUSTRIAL AND ENGINEERING CHEMISTRY
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fore the SOCIETY several years ago that he had found it possible to produce a 520 B. t. u. gas by this method, with an energy loss of 20 per cent.2 By separating the high percentage of carbon dioxide formed, a more valuable enriching gas can be obtained and the by-product carbon dioxide could be used for the production of solid carbon dioxide for refrigeration. Relative Availability of Materials
The first consideration in connection with the above materials is their relative availability at the points of consumption. I n this connection we must consider the geographical location of the important centers of the water-gas industry. GAS OIL-Figure 1 shows the most important distriots in which gas oil is used for the enrichment of blue gas. By far the largest part of the gas oil employed for this purpose in the United States is used on the northern Atlantic seacoast, New York, New Jersey, eastern Pennsylvania, and the southern New England states. Three-quarters of the gas oil used for enrichment of water gas is used in the district indicated and one-third of the total is used in the immediate vicinity of Kew York City. In order, therefore, to affect the consumption of gas oil, it must be possible to deliver the competing material in New York and surrounding markets. Although there is no immediate danger of a shortage in gas oil, there is reason to believe that, in spite of present conditions, i t will soon be more profitably treated a t the refineries than it now is at gas works, so that it will be gradually withdrawn from the market with a rising price. COALGAs--Coal gas can probably be manufactured in any required quantity for many years to come. The economics of coal-gas production, however, are intimately connected with the market for the various by-products which are simultaneously produced-namely,. coke, coal tar, and ammonia. Coal gas will, in general, be available in quantities wherever there is a demand for coke for domestic use to replace anthracite or bituminous coal. A small quantity can be produced in any gas plant of considerable size, the resulting coke being used in the water-gas generators. Such a combination, referred to as a complete gasification plant, will produce without further enrichment a mixed gas of from 360 to 400 B. t. u., depending on the quality of coal used. Furt her enrichment will almost always be n e c e s s a r y , e i t h e r from rich hydrocarbon v a pors, or by an increase in the ratio of coal gas formed through the sale of coke. In any case, the use of coal nas implies a plant-of considerable magnitude close to a market which can absorb coke, tar, and ammonia as required. At present the use of coal gas is confined either to very large operations where a wide market for coke can be developed, and large coke oven plants can be operated as at Boston, or to smaller districts where the local demand for 2
See Haslam and
Fo res.,
Gaa Age-Record, 62, 615 (1923).
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domestic coke has been already actively developed, and where horizontal retorts or the more recently introduced verticalretort installations can be economically operated on account of the high value of the by-product coke. This is the case in anthracite-coal burning districts where high-grade domestic fuel is demanded. With the completion of the K. G. S. low-temperature carbonization plant in New Jersey, and the sale of the gas produced in it to the Public Service Company of New Jersey, there will be completed an important large-scale application of cooperative gas enrichment. NATURAL GAS-Natural gas is available in enormous quantities in certain parts of the country, where it is frequently sold at prices as low as 40 to 50 cents per thousand cubic feet at retail, and can be obtained for 20 cents per thousand or less in large quantities. Recent advances in pipe-line design and construction make possible the extension of the use of this gas for enrichment of water gas to a few of the present gas-oil markets such as Denver, St. Louis, and New Orleans, but at the main center of the water-gas industry, on the northern Atlantic coast, natural gas can play only a minor part in displacing gas oil. On the contrary, a proportion of blue gas is being used to supplement the diminishing supplies in the older natural gas fields of western Pennsylvania, Ohio, and Indiana. Since the important consuming region is located at a maximum distance from the important natural gas and oil fields, transportation is a vital factor which precludes to a large extent the use of natural gas and such refinery gases as are made in the vicinity of the oil fields. REFINERYGAS-Crude oil, however, is transmitted by pipe line direct to New York City, and the refineries at Bayonne, N. J., and Brooklyn, N. Y., are now handling sufficient oil so that their refinery gas output could almost take care of the enormous gas-oil requirement of the New York district. Similarly, the refineries at Wood River could furnish gas to supplant a large part of the gas oil now used in the St. Louis district. The fact that the gas-oil markets are largely concent r a t e d i n a few l o c a l i t i e s , where the consumption of gasoline and other p e t r o l e u m produ c t s i s also at a maximum, makes it seem logical to consider seriously the use of refinery gases for gas enr i c h m e n t . The m a i n obstacle to this use is lack of understanding of the exact value of the m a t e r i a l s i n question a n d i n a b i l i t y of companies which are perhaps competing in other fields to realize that cooperation in this respect would be to their mutual advantage. Gases from oil-refining operations are now commonly used as fuel for the refinery, but their value to the gas company is so great that it is almost imperative that the refineries located near large cities should in the near future sell these gases for enrichment purpose and burn solid or low-grade
I N D CSTRIAL A,VD E-YGINEERING CHEMISTRY
September, 1928
liquid fuel. This is already being done to some extent, notably at Philadelphia. Refinery gases are of such value to the gas works that the refinery could afford to replace them by bituminous coal a t practically 815 per ton. The gases may be used without stripping beyond the valuable gasoline constituents, if the refinery is located near the gas works. Refineries located in the oil fields, however, can produce butane and propane by proper strippirig methods from these gases and ship these in liquid form to more distant gas plants. Since the oil refinery is essentially a largescale operation, the use of refinery gases will be confined to the large cities where enormous quantities of manufactured gas are used while the liquid propane and butane fractions, which are more easily transported, can be used in the smaller gas works. CATALYTIC PROCESS-Finally, the availability of catalytic condensation processes depends upon their commercial development, which will probably be stimulated by any pronounced rise in the cost of hydrocarbons and the possibility of this method of enriching will be of great value in balancing prices of the other materials.
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pose of producing enrichment gases, the secondary products being motor fuel and tars which would seem to be no more difficult to dispose of than the present by-products of the gas industry. The use of vapor-phase cracking processes for this purpose has been given some attention within the past few years. In vapor-phase cracking processes it is possible to obtain large yields of gas and of light hydrocarbons suitable for motor fuel and relatively small yields of the heavy oils and tars. The objection sometimes raised, that the gases contain large percentages of unsaturated compounds which may tend to polymerize and yield solid or liquid condensation products, might be overcome in several ways, as by passing these gases through the superheater of the ordinary type of water-gas machines. Relative Costs of Gas Enrichment by Various Agencies
In order to avoid an error common in discussions concerning gas, so far as possible costs will be given per therm of total heat value rather than in terms of cubic feet of gas.
Equipment Required
The equipment required for the utilization of the various enriching materials considered is in general of great simplicity. The evaporating and mixing equipment necessary for the use of butane is extremely simple. The handling and storage of these volatile liquids require methods which, although unfamiliar to the present gas-plant engineer, have been fully developed in natural gasoline refineries. Coal and natural gas and refinery gases require only some form of effective mixing device. The equipment for direct production of methane is probably more complex and will act somewhat as a hindrance to its development. Advantages of New Methods
One great advantage of all the new methods noted, as compared with gas oil, is that the enriching material may be freed from sulfur before being mixed with the water gas, the efficiency of purification being thereby increased. Butane is available which contains no hydrogen sulfide and not over 0.5 grain of organic sulfur per 100 cubic feet of vapor. This corresponds to a gas oil having less than 3 parts per million of total sulfur. Table I-Relative
Value of Enriching Materials
Generator fuel at 25 cents per million B. t . u., efficiency SO%;,($6 per ton for 12,000 B. t . u. coal or coke) Gas oil efficiency, 100,000 B. t. u. per gallon (65 cubic feet) Heating value of finished gas, 400 500 600 800 1500 B. t . u. Using gas oil: Per cent of heat from bluegas 6 8 . 6 PRICE OF OIL Cents p e r gal. Cents 4 4.13 5 4.45 6 4.76 8 5.39 10 Compared with gas oil at 6
-------
~~
GA 5
Cents
Cenls
Cents
Cents
4.10 4.60 5.10 6.10
4.08 4.70 5.33 6.58
4.04 4.82 5.60 7.17 8.73
4.0 5.0 6.0 8.0 10.0
cents per gallon: HEATING VALEE PER VALUE B. 1. u.
Blue Coal Coal Natural Refinery Refinery Butane-
0
50.0 37.5 21.9 COSTPER THERM--------
M FT.
$0.126 0.320 0.415 0.571 0.698 0.900 6 . 6 7 cents per gal.
VALUEPER
THERM Cents 4.20 -5.33 .j,53 .5.71 3.82 6.00 6 26
The advantage of using hydrocarbons in the gaseous form is so great that it is well to give some attention to the possibility of operating a small oil refinerv" Drimarilv for the Dur. I
Figure 2
We must also bear in mind that the cost of distributing gas is a considerable proportion-one-third to one-half-of the total cost of the gas service, so that an increased demand might be more economically met in many cases by increasing the heating value of the gas rather than the volume supplied, even a t a higher manufacturing cost. The price charged per 1000 cubic feet would, of course, be adjusted to make the price per therm the same as before. In speaking of enrichment of blue water gas, there may be some misunderstanding as to the magnitude of the part played by the enriching medium. In order to produce a mixed gas of, say, 550 B. t. u. per cubic foot, it is necessary to supply a t least as many heat units in the form of enricher as in the form of blue water gas, and in the case of gas oil and most of the other enriching materials the heat sumlied in the enricher is rather more-than that supplied b y t h e blue gas. Figure 2 is a diagram indicating for various heating values of the final gas and of enrichment gas the percentage of the total heating value which is derived from the blue gas. It will be noted that a considerably higher percentage of heat can be
INDUSTRIAL AND E-VGINEERING CHEMISTRY
912
derived from blue gas if the enriching gas has a high heating value per cubic foot. This relation must be borne in mind when we consider the relative values of various types of enriching materials. We can show roughly the relative prices a t which the various materials can compete as gas enrichers under assumed conditions and more particularly bring out the fact that the value of these various materials for gas enrichment cannot be judged solely on a price per gallon or even on a price per therm of heat units basis, but must be looked at from the point of view of total cost of the final gas. We have computed the cost of the materials which enter into the production of gas of various heating values enriched by various methods and with various prices for the enriching materials and, based on gas oil a t six cents a gaIlon, we have obtained comparable prices for the various other substances. In a general discussion it is not possible to consider quantitatively all the various factors which will affect relative
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costs-such as the effect of various gravities of gas resulting from the various methods considered, the relative amount and value of by-products, the value of the various materials as reserve supplies more easily stored than gas, and the questions of plant safety and operating convenience. These questions must be considered by each plant engineer for his own operating conditions. Table I gives a comparison of values on a heat-unit basis, which must be modified to suit local conditions as mentioned above. The cost of catalytic condensation is not serious from the point of view of energy loss, but in this case careful consideration would have to be given to the design and cost of the equipment necessary to carry out the process. It should be noted, also, that the very high heating value of butane vapor per cubic foot makes its value per gallon from 10 to 12 per cent above that of gas oil, although its heating value has been assumed as only 6 per cent greater than the gases which can be obtained from a'gallon of gas oil.
Potassium Xanthate as a Soil Fumigant-11' E. R. deOng2 and Jocelyn Tyler3 UNIVERSITY OF CALXSORNIA, BERKELBY, CALIF.
The rate of decomposition of potassium xanthate, the inhibition of s e e d l i n g as measured by the evolution of carbon disulfide, is xanthate (KS2COCZHe) growth-a serious criticism of given when combined with hydrochloric acid and with as a soil fumigant was xanthate when used alone. the superphosphate of the fertilizer trade. Laboratory discussed two years ago4 from Acids in liquid form cannot measurements have been made of the rate of penetrathe chemical standpoint, and be used in a dilute state in tion of carbon disulfide into both loose and packed the biological effect was then soil on account of reaction sandy and heavy clay soils. d e t e r m i n e d with beetles. with soil bases, but under The toxicity of xanthate has been tested principally Since then, in addition to laboratory conditions t h e y against the root-knot nematode. It has been shown further chemical experiments, h a v e been combined with that a complete kill is possible in the laboratory with two years of field experiments, aqueous solutions of xanthate the different stages of the nematode, while good consupplemented by laboratory before applying to the soil. trol has been obtained in field experiments. tests, have been conducted on The best results have been the attemrked control of the obtained with applications of root-knot nematode, Caconema radicicola (Greef) Cobb = the powdered xanthate intimately mixed with the superHeterodera radicico2a (Greef) Muller. From this work phosphate of the fertilizer trade alone and with superfine conclusions have been reached as to the possible value of sulfur. xanthate for field use under limited conditions. These data COMPARATIVE VALUESOF CARBONDISULFIDEAND X ~ N also contribute to our general knowledge of soil fumiga- THATE-The advantages of xanthates as fumigants over tion. carbon disulfide itself are:
HE value of potassium
T
A
Chemical Considerations
The chemical and physical properties of xanthate, as affecting this problem, were reviewed in detaiI in the first paper so will be touched upon but briefly. Xanthates are compounds of xanthic acid, such as potassium ethyl or sodium ethyl xanthate, the free acid being unknown. On decomposing it releases carbon disulfide, to which apparently the toxicity is due. Decomposition occurs, however, very slowly in a neutral or basic medium: hence it has been found necessary to include an acid with all soil applications. This makes possible the maximum decomposition of xanthate in a variable length of time depending on the type of acid used. High concentrations of gas in the soil are thus made possible, while the early decomposition of the salt prevents Received April 2, 1928. 2 Present address, First National Bank Bldg., Berkeley, Calif. * The senior author reports the chemical phases of the subject, as well as the field work and beetle tests. The junior author contributes the laboratory data on nematode fumigations. IND. ENG.C H E M . , 18,:52 (1926). I
'
(1) High solubility in cold water, thus permitting the solution to be carried downward into the soil by irrigation water or heavy rains. Carbon disulfide when used alone does not permit of a uniform distribution through the soil and the gas does not penetrate downward readily into dense subsoil. Emulsions of carbon disulfide and water are now being used in the Japanese beetle work, but it is often inconvenient to make the emulsion and this may break before penetrating deep into the soil. (2) A graduated release of carbon disulfide from xanthate is possible, based upon the formula used, permitting either quick evolution of gas or a slow release prolonged over a period of 10 t o 12 days, while carbon disulfide volatilizes very quickly and dissipates at a corresponding rate except in heavy or in very wet soils. ( 3 ) Potassium xanthate is a safer chemical to handle than carbon disulfide, as it has no explosion hazard.
DECOMPOSITION OF XANTHATE-The rat€! O f decomposition of potassium xanthate (purity 95 per cent +) varies with the temperature but normally requires several hours to complete, even when in solution with equivalent amounts of acids. In soil work the amount of decomposition varies with the complex of the medium. It will be seen in Table
