INDUSTRIAL AND ENGINEERING CHEMISTRY
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I l l 1 1 1 / ) I ! 1 1 )
c
Temperature
Figure &Runs
'7osoline Curve / o o o
Straiqht
Vol. 18, No. 12
the use of the nickel carbonyl solution after the nickel had been converted to the colloidal state. It is apparent that under the conditions maintained in this work free metallic particles suspended in the combustion zone of the cylinder do not have a measurable effect in suppressing detonation. This evidence in its relation to Charch's theory is, however, only negative and there is still a possibility that the particles formed in situ by the decomposition of the metallo-organic compound may be in a state of temporary activation greatly superior to that of those otherwise prepared. With respect to Jolibois and Normand's hypothesis, it would seem that if the suppressive effect is due merely to the plating over of sharp points on the interior wall of the cylinder, some improvement should have been noted in our tests. Furthermore, these beneficial effects should be prolonged, for a short time a t least, after the feed of the antiknock is discontinued, instead of ceasing immediately as is actually the case.
o f cylinder wall- " C
Acknowledgment
w i t h Nickel Carbonyl a n d Its Derivatives
pared with ethyl lead is much lower than that reported in the literature. Curve 2, which coincides with curve 1: was obtained with
The authors wish to express their gratitude to the Internat,ional Nickel Company and to the Ethyl Corporation for help in procuring needed material.
Wood a s Gas-Making Material' By 0. F. Stafford UNIVERSITY OF OREGON,
H E use of wood as gas-making material is as old as the gas industry itself. History has it that Phillipe Lebon probably antedated William Murdoch in discovering the usefulness of gaseous products obtained in the destructive distillation of organic materials. Lebon obtained his gas from wood while Murdoch used coal. The Englishman, however, had made the more practical discovery, fiince coal is a better gas-making material than wood and certainly, as a rule, is more dependably available. These facts have determined the course of the industry. Perfectly good gas can be made from wood, but the advantage so lies with coal that wood can be used for making gas only where it can be obtained cheaply under circumstances making coal or oil less available. Since it happens here and there that just such circumstances do exist, the interest in gas from wood is not altogether an academic matter. In the paragraphs to follow the status of gas manufacture from wood is briefly set forth.
T
Closed Retort Processes
The most obvious method of making gas from wood is to follow the practice developed through long years for coal gas. Most often this has been done simply by using retorts designed, and even erected, for the carbonization of coal. In other instances the gas plant has been designed specifically with the idea of adaptability to the differences in character of wood compared with coal. In any event, due provision must be made for the acid character of the wood distillate. A disadvantage as compared with coal lies in the relative bulkiness of wood, which makes it impossible to charge as great a weight of material into a retort of given size On 1 Presented
under the title "Wood Waste as Gas-Making Material" before the joint session of the Divisions of Petroleum Chemistry and Gas and Fuel Chemistry a t the 70th Meeting of the American Chemical Society, Los Angeles, Calif., August 3 t o 8, 1925. Received July 8, 1926.
EUGENE, ORE.
the other hand, if the wood is quite dry the period required for complete carbonization is shorter, so that conditions may exist under which as much gas actually can be produced in a retort of given size by the use of wood as by the use of coal. Very little information is available regarding the hightemperature carbonization of wood in continuously fed vertical retorts or in retorts of the type used in by-product coke manufacture. For the production of wood gas upon a large scale these types of machines would seem to offer a very satisfactory procedure. In gas manufacture, just as in low-temperature carbonization, woody materials may be classed into the two broad groups, hardwoods and resinous woods. Both the quality and quantity of gas made from resinous woods, other things being equal, are superior, and in both respects the superiority increases with the resin content of the wood. HORIZONTAL RETORTBENCH-Typical of retort practice is an operation conducted for a time a t Auburn, Wash.,* where the following results were obtained in a bench not equipped for regenerative heating: Material
Hemlock mill waste, wet
Cu. ft./ 100 lbs.
B. r. u./
cu. ft.
400
A representative analysis of the gas is as follows: c02 Illuminants
co
CH4 HI Ng
* THISJOWRNAL, 7, 962 (1915).
Per cent 17.4 6.0 31.5 21.7 18.3 5.1
INDUSTRIAL A N D ENGINEERING CHEMISTRY
December, 1926
From the foregoing data it follows that the over-all thermal efficiency of the operation was about 45 per cent, assuming 20 per cent moisture in the forest wood and estimating its heating value a t 8800 B. t. u. per pound of absolutely dry material. Tar production was 10 to 15 gallons per ton of dry material, while the gross yield of charcoal was better than 500 pounds per ton. Gas was made a t the rate of 16,000 cubic feet per ton of absolute material, its heating value being 480 B. t. u. These yields compare very favorably with the production.of 11,000 cubic feet of 575 B. t. u. gas obtainable from a ton of good coal. In the case of the mill waste, the showing is apparently not so favorable, which may be due in large measure to a difference in moisture content. Even so, this very cheap form of wood (again assuming 20 per cent moisture content) gave the equivalent of practically 14,000 cubic feet of 475 B. t. u. gas, which after all is significant. In a well-designed installation operating costs should not be greater than in a coal-gas plant, especially since purification costs are very low. The carbonization period in this plant was about 100 minutes. IKTERNALLY HErlTED RETORTS-In a Series Of SemiCOmmercial retorting tests made by the writer the generator of a standard Lowe water-gas set was used as an internally heated retort. In this work an average yield of over 18,000 cubic feet of 480 B. t. u. gas was obtained per ton of absolute wood substance carbonized. The composition clf the product is represented by the following analysis:
con co
Hi CiHa CHI C~HI Na
Per cent 17.0 31.0 21.5 1.5 20.0 6.0 3.0
The procedure consisted in heating up the water-gas set by the use of coke. After refractories throughout the appliance reached incandescence, a charge of 1000 pounds of wood was introduced through the coke-charging door. The decomposition of the wood occurred rapidly, all vapors passing through the carburetor and superheater to the scrubber and thence through a stand-by station meter. The residual charcoal in the generator served to heat the set for a subsequent run, and so on. The yield of gas was higher than that reported from the horizontal retorts a t Auburn, owing probably to the more complete cracking of vapors. The composition of the two gases is strikingly similar. Absolutely dry Douglas fir mill waste such as was used in the above test runs has a heating value of about 8700 B. t. u. per pound. The thermal efficiency of the gasification was accordingly slightly over 50 per cent. KO tar was recovered and under the conditions of the experimental work all charcoal was consumed in warming up the retort for the next charge. Theoretically, there should be an excess of charcoal over that necessary for carbonization, so it is possible that more or less by-product charcoal might be obtained by this method in regular operation. Wood as a Substitute for Coal in Blue-Gas Machines
The successful utilization of bituminous coal in water-gas and blue-gas machines naturally has raised the question as to the availability of wood as gas-making material in a similar operation. Experimental work upon a semicommercial scale recently carried out under the observation of the writer indicates that the problem of making gas in this manner can be solved. These experimental runs were made in a machine designed for the purpose, although the designer had had no previous actual experience with wood and failed to anticipate aome of the conditions necessary for operating with this substance. It was not possible to meter the output, so accurate
1319
yield data are lacking. The estimated 25,000-cubic foot yield of 350 B. t. u. gas per ton of absolute wood substance may not seriously be in error, since it corresponds to a thermal efficiency of 50 per cent, which in a properly designed appliance possibly is attainable. The following analysis is typical of the quality of the product: COS C~HI 01
cn __
CHI Ha NS
Per cent 10.3 1.4 2.0 32 5
12.7 31.3 9.0
The material used was western yellow pine. A small amount of tar is to be expected as the only by-product. The gas resembles blue gas and accordingly is highly desirable. Again it is to be noted that the similar gas-making operation using 12,000 B. t. u. soft coal yields approximately but 35,000 cubic feet of gas of this quality. Producer Gas from Wood
There are in the literature many accounts of operations in which wood is made to serve as fuel for gas producers. Some of these operations have been entirely successful SO that there are existent reliable engineering data to serve in? designing and operating plants of this type. Reference will. be made here to but a single instance of producer operation. The example selected is an experimental project undertakea a t the University of Washington in the Mechanical Engineering Laboratory. The producer was a small one of the suction type, but the tests were made with extreme care and it is believed that they are fully representative of what would be encountered in large-scale practice. The material used was Douglas fir mill waste which yielded a gas having a heating value of 130 to 140 B. t. u. No analyses are reported and the gas was not metered. The product was used to operate an engine, however, and from the energy development, assuming 20 per cent efficiency for the engine, a thermal efficiency of 70 to 80 per cent was secured in the producer. Assuming the lower of these efficiencies as representative of dependable performance, it follows that a pound of absolute wood substance (say, 8700 B. t. u.) would yield 45 cubic feet of 135 B. t. u. gas at a cost for material (two dollars per ton of absolute wood substance) of about two cents per 1000 cubic feet. For comparison it may be stated that the cost of 135 B. t. u. gas made from 12,000 B. t. u. coal worth five dollars per ton in a producer operating a t 80 per cent efficiency would be 3.5 cents per 1000 cubic feet, material alone considered. Low-Temperature Carbonization of Wood
While the foregoing discussions have had reference exclusively to the carbonization of wood a t high temperatures. it is to be remembered that the wood distillation industry as conventionally carried on is a lowtemperature operation, its objective being the production, not of gas, but of charcoal and condensable vapors. This industry therefore seeks to maintain its retorts a t the lowest temperatures consistent with advantageous recovery of these latter materials. The result is a production of a small amount of gas heavily loaded with carbon dioxide. Both yield and quality of gas vary widely with momentary practice, the yield being usually from 2 to 3 cubic feet per pound of absolute wood substance, while the heating value ranges between 200 and 300 B. t. u. The following figures indicate composition in a general way: COY CQ CHI Hn CZHI,etc
Per cent 40 to 60 25 to 40 5 to 20 0 to 10 Oto 5
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Vol. 18, No. 12
Value of Low-Temperature Distillation By-products It is obvious that the low-temperature distillation of wood in itself is of but little interest from the point of view of gas An evaluation of the by-products of low-temperature manufacture since, even if the large proportion of carbon di- wood carbonization involves many variables. The charcoal oxide could be removed, the low yields would offer an in- obtained in low-temperature carbonization is usually in good superable obstacle to economic production. Where large- demand a t prices considerably in advance of the cost of other .scale production of either distillate or distillate and charcoal forms of fuel and to the extent that it could be marketed i s desirable, however, it is feasible to pass the low-temperature a t good figures should not be gasified. The value of crude gas through a bed of incandescent charcoal in machines of pyroligneous acid w ill be greater if it is produced from the either the blue gas or producer type and thereby, at the ex- usual hardwoods than if obtained from resinous woods. pense of an equivalent amount of charcoal, convert the car- The crude distillate from Douglas fir contains but 30 per cent bon dioxide into carbon monoxide. If wood distillate alone as much methanol and but 60 per cent as much acetic acid is desired the whole of the charcoal can in these operations as that from hardwood. The profitable recovery of these be converted into gas. substances from Douglas fir distillate by methods traditionIf in a two-stage operation of this sort the low-temperature ally used in the industry is hardly to be expected. Subgas were passed through a blue gas machine, the effect would stantial progress is being made with other methods, which be not only to reduce carbon dioxide to carbon monoxide but in large-scale operations should produce attractive returns. also to lower the hydrocarbon content of the gas, the hydrogen Conclusions content thereby undergoing a corresponding increase. The In the foregoing cursory survey of the status of gas proresulting product would resemble blue gas, and of course duction from wood the outstanding fact is that the several blue gas itself could be generated simultaneously, to any demethods of gas production which have been developed dursired extent. Making reasonable assumptions as to coning the past century for use with coal, find really a close version efficiencies, it is to be expected that as much as 25,000 parallelism where wood is to be carbonized or gasified. cubic feet of gas having a heating value of approximately Practice has demonstrated that thermal efficiencies in gas300 B. t. u. could be obtained in addition to the wood dismaking operations involving these two materials are much tillate of the low-temperature carbonization by use of a ton the same. Each material has its peculiarities and these must of absolute wood substance. be thoroughly understood before the technical details conThe alternative of passing the raw low-temperature gas cerned in successful gas-making can be carried out. Vastly through a charcoal producer should yield something like more has been done in the study of coal than has ever been 40,000 cubic feet of product having a probable heating value attempted with wood, but in spite of this fact there is a of 180 €3. t. u. Because of lower operating costs and higher sufficient accumulation of dependable experience to justify conversion efficiencies this procedure should offer economic the assertion that in the field of manufacture of low B. t. u. advantages in any situation where gas of this quality could gas the use of wood deserves much greater consideration be used. than usually is accorded it.
Determination of Metallic Lead in Metallurgical Products and Pigments' By Donald H. McIntosh RESEARCHLABORATORIES OB UNIVERSITY OF UTAH,IN CO~PERATION WITH U. S. BUREAUOF MINES,INTERMOUNTAIN EXPERIMENT STATION, S A L T LAKECITY, UTAH
T
HE method described is the result of an investigation to find a means of determining the extent of the reduction of lead ores and concentrates after a treatment with the reducing agents commonly used in metallurgical practice. In order to obtain definite data it was necessary to devise an accurate method for determining the amount of b a d that had been reduced to metal. The method, which is applicable to matte and slags, offers a means of determining the amount of metallic lead in these products and consequently will aid in determining the optimum settling conditions to be maintained in blast furnace practice. Where chemical processes that convert metallic lead into other forms are used, a method of determining how far that conversion has progressed will be of especial importance. Chemicals and Apparatus Sodium hydroxide solution, 50 cc. of 15 per cent, by weight 10 per cent silver nitrate solution, 10 cc. Concentrated sulfuric acid, 10 cc. 50 per cent alcohol solution, 15 cc. 1
Received June 19, 1926.
U. S.Bureau of Mines.
Published by permission of the Director,
Saturated ammonium acetate solution, 5 cc. Standard ammonium molybdate solution Tannic acid indicator solution Asbestos for Gooch filter Pyrex beaker (250 cc.) Erlenmeyer flask (250 cc.) Principle of Method
The properties of metallic lead upon which the method depends are its insolubility in sodium hydroxide solution and its solubility in silver nitrate solution. It was found by experiment that the silicate, carbonate, oxide, sulfate, and a part of the sulfide of lead were soluble in sodium hydroxide solution and could be removed by filtering, leaving a residue containing the metallic lead and the remainder of the lead sulfide. Under the conditions established as standard in the method, metallic lead is soluble and lead sulfide is insoluble in silver nitrate solution; consequently these two substances may be separated by treating with silver nitrate and filtering. The dissolved metallic lead in the filtrate may be determined by titrating with standard ammonium molybdate solution. After careful trial upon synthetic products the following procedure was found to give accurate results:
