SUCTION GAS AS A MOTOR FUEL.
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First Description of a New System which By John
UNDOUBTEDLY there is no lack of general interest in the subject of suction gas as a possible substitute for petrol as a motor fuel. — The recent prominence given to its discussion in THE COMMERCIAL MOTOR leads one to realize that the exposition of diverging views has an educational value which is all to the good if permanent results are to be attained. Without desiring to enter into controversy with any of the correspondents who have expressed views on this important matter, it is nevertheless thought that it will still further ventilate the subject if some of the issues are again brought under review and the ground work somewhat defined. In an article appearing in the issue of 13th June the present writer indicated 'that there exists substantial difficulties in the way of successfully applying suction gas to commercial lorries, and that the main trouble to be overcome lies in treating the volatile matters (tar carriers) in such a way that these are rendered into fixed or non-condensible gas, clean enough for use in the engines. Otherwise, trouble will be met and suction gas will prove to be unreliable. Nothing may be gained by belittling or ignoring the hard facts of the case and much is to be gained by a camlid gettogether discussion of past failures out of which success can probably be developed. There is always a certain amount of natural reservation when one has failed to attain the success aimed at, but, if the cause of each failure had been made as available to the world as is the practice when some success is reached, it would have shortened the path still to be traversed to better things.
This applies very aptly to the evolution of suction gas plants for any purpose whether for land, marine use, or vehicles. We find it stated by Major D. J. Smith, in the same issue of THE COMMERCIAL MOTOR, that bituminous coal cannot be successfully gassified in suction gas plants because of the presence of and the difficulty in dealing with the tarry matters produced ; while the statement is made that anthracite is practically free from tar. Both statements are only partially true and call for extension and definition.
The Difference Between Anthracite and Bituminous Coals.
Technically, it is customary to define anthracite as a special quality of coal which contains up to about 12 per cent. of volatile matters, whilst bituminous coal contains over 12 per cent. They diverge into these classes round about that point. There are low volatile bituminous coals and high volatile anthracites. The trouble is that each contains volatile matters which are more or less readily given off at distillation -temperatures, and, while elaborate washing will remove the bulk of the tar carried in the gas stream, it is the final traces and their accumulative effects that constitute the real trouble and difficulty which, as has been stated, have proved to be a barrier to the more widespread use of gas engines fed from suction gas plants. It is therefore clear that the sole reason why anthracite is used in nreference to bituminous coal B32
should be Applicable to Motor Vehicles. Stewart.
for this work is simply because the latter, although much more abundant and therefore cheaper, gives off more tarry matters which cannot be got rid of.
TO illustrate the practical point, in pre-war days the writer stumbled across a plant by a well-known maker in which Scotch anthracite at 16s. per ton had been used and abandoned for a higher grade anthracite at 26s. per ton to get rad of the troubles arising from tar evolved from the former. It was a question of degree, but not of having thereby reached perfection.
It is for the seine reason that internal-combustion gas engines remain in so backward a state in their application to marine MO, and the path along which the writer has travelled led to the formulation of ideas which hold quite definite prospects of not only getting rid of tar from anthracite but also from bituminous coal. It is necessary to state, however,. that because of the small size of generator .required for commercial lorries it has been decided to confine its use to anthracite or gasworks coke for the present because of the cleaner gas producable from such fuels.
The Systems Devised for Treating the Tarry Matters.
It has been stated that every updraught producer suffered from the disadvantage that the tarry matters driven off from the fresh change of fuel joined the stream of good clean gas which had been generated
from the fixed carbon or coke lower down and that the former contaminated the latter. In this system the air and steana, which support and regulate the process of combustion and gasification, pass from the i bottom upwards while the fuel passes n the opposite direction, i.e. from the top downwards, and is known as the " updraught system." It was at one time thought that, if the air was supplied at the top and caused to pass downwards in the same direction as the fuel and the gas to be led off at the bottom, then better results would be attaided. This second system is knewn as the " downdraught system." On the main principle of eliminating tar by its combustion within the generator it has points of advantage, but these did not outweigh its disadvantages. The disadvantages were that, as the gas was delivered at the base, where the ashes accumulated, the generator had to be stopped to dean out the ashes, otherwise air and gas uniting at the base when the bottom door was opened formed an explosive mixture. In addition, it proved impossible to prevent an important percentage of the fixed carbon of the fuel from getting mixed up with the ash.
A third system was introduced in which the fuel
was fed in at the bottom and the gas drawn aff at the top, the air and gas again travelling in the same direction as the fuel. This was known as the "underfeed system." This had the advantage of the cooler top, but it posseAsed most of the disadvantages of the dowhdraught system, particularly the mixing up of the ash and the coal in the lower region.
A two-generator system was tried in which one generator worked on the updraught and the tarry matters were drawn off from the top and caused to pass through the incandescent mass of coal in the second generator, the system being a reversible one, and may be called an " updraught-downdraught system."
Subsequently a single generator was invented to serve the same purpose, the generator being divided into two Chambers, one being a distillation chamber, the products rising in preeaure and forcing themselves dowewards through the incandescent mass of fuel in that chamber, thence up through the adjacent chamber in which gasification was proceeding on the upfira.ught principle. The primary object in this latter case was to provide a definite path through which the volatile products must pass before reaching the outlet pipe.
It had been demonstrated, by quite a number of prior " by-pass " forms, that separate treatment of the volatiles had failed because of the lack of definiteness of control over their path. But the "twochamber reversible distillation system" failed to reach the success expected for other and more obscure technical reasons, but the idea is particularly interesting as it was the product of the mind that had rendered the world a great service by the discovery i
that blast furnace gases were usable n gas engines and had thus saved the world millions sterling per annum.
The above does not by any means exhaust the different systems which have been devised, but they give the main outline of work done in methods of operation and construction which had the object of treating the tarry matters met with when using bituminous coal. Enough has been stated to justify the writer's former plea that the application of suction gas to motor vehicles is not a path strewn with roses. As mentioned at the outset, the difference between anthracite and bituminious coal is only a difference in degree of the main problem. The direct inference is that, had these efforts led to real solutions of the larger problem, they would, at the same time, have rendered it possible to provide a snore perfect apparatus for the lesser.
It is along this path that the writer has travelled— circumspectly, indeed, Because of the traps set for the unwary, but not without acquiring special insight into the problem and an appreciation of the economic
value of a sOlution to it. The need for invention is obvious, and it is recognized by all students, professors, and engineers conversant with gas engine and gas producer practice. It was with the same object as honest old Abernethy, viz., "to get me some gain," that this path was entered ; for, as Professor Luke of the U.S.A., dealing with the subject, wisely says:—" This success means not only a great deal for the man or group of men responsible for it, but far more to the country at large."
Seeking Another. Solution.
Reverting, then, to the principle of the generator which is divided into two chambers, one operating as a distillation chamber and the other as an -updraught chamber and reversible, the writer discovered that an important step had to be taken inasneuth as it was realized that that system could only defeat its own object. It was therefore determined to add another system to the prior list.
This consisted of a single-generator two-chamber reversible system, in which both the updraught and the down-draught principles are truly applied and definitely separated, so that the tarry matters are subjected to combustion always on the down-draught system while the up-draught system is simultaneously employed for the final gasification of the fixed carbon. A photograph of this generator is shown.
As a result of exhaustive investigation, it has been authoritatively proved that the proper treatment of the fixed carbon and the volatile hydro-carbon of the fuel presented opposed -conditions which it had hitherto been impossible to reconcile in one apparatus. The last-named system the writer has been able to demonstrate to be effective and workable as a system for treating bituminous coal. Unfortunately, for marine and motor lorry purposes it possessed two hindrances to its application, viz., reversibility and weight. Therefore, with the view of providing more advantageous means for marine use, the idea was formulated that the principle should be modified on lines which . would not require to be reversed, thus affording a means of reducing weight. It is this improved system which it is proposed to apply to motor vehicles to provide a substitute for petrol as fuel.
We would have been pleased to submit our designs to the scrutiny of the engineering world, but, at this stage, are prevented from doing so for reasons which are dependent -on foreign patent law. It is not, in our case any predilection for the secrecy which is said to afflict gas-producer designers at present.. But, granting the principle of operation to be sound and the resulting gas to be satisfactory for utilization is a means of power generation for motor vehicles, the methods of application of the apparatus is of interest, and is only feasible if the weights are less than normal practice, and this we claim to have attained.
It has been stated elsewhere that there is serious doubt aboutbeing able to accommodate a suction-gas plant on a 3-ton commercial vehicle. It is prbposecl to provide this accommodation by drawing hack the lorry body some 20 ins., or, in the case of new cars, the chassis could be lengthened to a like extent. The gas plant is then placed behind the driver's seat. The weight of the gas plant is therefore about evenly distributed between the front and rear axle. The scrubber is placed horizontally over the generator and exterior to the woodwork enclosing the gas generator. In this way the scrubber is exposed to the cooling effect of the air currents when the vehicle is travelling. The water to the scrubber is pumped to four sprays, and it outflows at the left-hand end to a pipe leading to a water tank secured -to the side of the chassis frame and under the lorry body. From this tank, which is a partial radiator for cooling the scrubber water, it flows into a reserve tank at the rear from which it is again circulated to the scrubber. A small water tank over the generator provides an independent water supply to the evaporator, but the overflow from the evaporator is led into the scrubber tank system: All levers and gas-producer control gear are conveniently arranged within easy reach of the driver or his mate in their sitting position, and sufficient coal may be stored under the driver's seat for, say, five or six hours run at full load. The levers referred to are, of course, only operated when it is required to start up or stop the generation of gas, as the process of gas making is continuous and dependent only on the continuous running of the engine and the free admission of air to the generator.
Application to Motor Vehicles Calls for High Efficiency.
It will be seen that, in the position proposed, the system is equally applicable to new or existing chassis, and its application in the case of cars at present driven by petrol is likely to be determined by considerations outside of the general character of the scheme. In fact, it amounts to this, that, if suction gas is rendered possible for a new and special type of car, it is possible of application to existing cars with, of course, a certain lowering of efficiency. It has been asserted by some writers that there is no doubt producer gas should prove to be the most successful and economical fuel for specially-constructed heavy vehicles but not so for existing petrol-driven lorries. Strangely enough, we approached the problem from the opposite end. It is noteworthy that, in any gasproducer scheme for this purpose, the prime object must be to produce a gas sufficiently clean for the purpose, for, on the cleanliness factor hangs the gascooling and cleaning plant, and, if the ordinary cleaning is to be done on a vehicle, it is almost certain that the water requirement for this purpose will render the system abortive. If cooling of the gases only is required, the scrubber water can be cooled and recirculated as is the case with the engine jacket water. On the other hand, if cleaning, especially tar and soot removal, is to be provided for, then the problem assumes a much more serious aspect. One therefore regrets to see recent illustrations of gas-generator plantsintended for application to motor vehicles, the inventors of which ignore the fact that the gas producer must, to be successful for this work, be so constructed that the gasification process is improved as well as thd structural details altered from prior equivalents. To attain the latter object without securing the former chemical effect, is misdirected ingenuity, which must prove disappointing to the originators. But this is no reason why invention, experiment and development should not be undertaken and officially encouraged when right lines are proposed, as in the case of compressed gas.
The more one realizes the present and future possible petrol stringency, the more important appears to be the case in favour of a suction gas solution to the problem. And inasmuch as the Fuel Administration of the U.S.A. finds it necessary to issue notice to the public of the Mississippi River region to cease using petrol on Sundays for passenger motorcars, motorcycles and motor boats, it seems that the time is rapidly approaching when our Government may find it expedient substantially to subsidize such inventors as can submit to the Gas Traction Committee sufficient evidence of reasonable expectations of good practical results as would warrant their recommendation and the issue of "Priority A" certificates for all work undertaken with their sanction. Indeed, it would not be difficult to chow that much less important work is regularly under way throughout the country, and that thereby the pitch has been queered for actual war work.
Anyone who overcomes the difficulty experienced in the transport work of the country by substituting town or producer gas for petrol or by providing,other substitute is doing real war work, for, if petrol is not forthcoming, strangulation of transport is effected while, the longer the war lasts, the worse railway rolling stock becomes and the more road transport will be required.
Moreover, development on these lines has, for this country with its great ooal supplies in lieu of petroleum fields, an economic value the magnitude of which it is difficult to visualize.