ALTERNATIVE FUELS FC M WAGON FUR NA CES.
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Comments on the Official T
lged by the Coal Controller.
The Coke Point of View : Mr. E. W. L. Nicol.
THE RESULTS OF comparative tests with coal and coke as fact for steam wagons, which were arranged by Mr. W. E. Hardy, Electrical Engineer, Bath, and published in the issue of 19thf September under the aegis of the Board of Trade (Coal Mines Department) arc very gratifying in that they tend to prove that gas coke is the most efficient and the only solid motor fuel which is absolutely smokeless. But the figures do not appear to be presented in a very fair or unbiased way, and I trust, therefore, that I may be permitted the following commentary on the tests as published with the view to correcting the unfavourable impression which the figures as presented will convey, to many of your readers, as to the utility of gas coke as fuel for steam wagons and for steam raising generally.
Comparative Calorific Values.
In stating •calorific values of solid fuels it is usual and necessary to indicate whether these values are given on the dry or on the wet basis. Ifi the tabulated figures the calorific valne of Welsh coal is given simply as 14,468 B.T.U. and that of cols.; as 8663 B.T.U. On the dry, or even on the wet basis, this latter figure is unaccountably low and considerably less than average quality coke breeze. The calorific power of average quality gas coke 'is about 12,000 B.T.U. as sold, including moisture and ash. The Technical Committee of the Royal Automobile Club give the calorific value of a sample of coke selected and tested by them as 12,468 B.T.U. (June, 1914), while Messrs. Brownlee and Green, Consulting Technical Chemists, Manchester, give the average of many tests as between 12,000 and 12,500 B.T.U. (" Engineering," July, 1918). The quality of coke, of. course, depends largely upon the coal from which it' is made ; but s;ihile the name of the BithOits Light and Coke Co. is given is the makers of the coke used on this occasion the fact is not revealed that this gas company is obliged, through the operation of the Coal Redistribution Order, to use locally procured Somerset coal, which is notoriously dirty and unsuitable for gas or -coke making. Containineas it does, 23 to 28 per cent. of ash,. Somerset coal nevertheless produces Coke of over 10,500 B.T.U. per lb. as sold, and contains only 3 to 4 per cent, of moisture. The lower figure (8663 B.T.U.) is no doubt due to moistureg absorbed after leaving the gasworks. As local repre'sentative of the Coal Controller, these circumstances probably are well known to Mr. Hardy.
Comparative Thermal Efficiency.
The actual evaporation, per lb. of Welsh coal is given as 7.2 lb. The temperature of the feed water is not stated, but assuming a 'feed temperature of 60 degrees 'ahr., the combined net thermal efficiency of boiler and fuel is, therefore, only 57.3 per cent., while that of gas coke (4.92 lb. evaporation) works out at 64.6 per cent. Bearing ii mind the wide difference in the price of Welsh coal and gas coke there would appear, therefore, to be good grounds for the B32 122 claim that gas coke is not only the cheapest but the most efficient motor fuel.
Unfavourable Conditions.
With few exceptions, steam wagons usually are equipped with narrow-spaced fire bars and blast nozzles designed for use with friable anthracite Welsh coal, and, therefore, are obviously unsuitable for either coke or bituminous coal. Now, as everybody knows, gas coke is about &ruble the bulk of Welsh coal. It natnrally'follosis that, in order to burn an equivalent quantity in a given time, it is necessary to maintain a coke fire about twice the depth usual for Welsh coal ; and in order to-force the air necessary for combustion through the relatively deep fuel bed, wide-spaced fire bars and increased draught pressure are essentiak. Similar conditions.have, in railway locomotive practice, been found necessary for bituminous coal. -Yet, in the comparative tests published, no mention is made as to whether these elementary conditions were provided. In these circumstances, the high average steam pressure maintained with coke on the upward steep gradient is all the more gratifying, but the steady loss of pressure on the down gradient can readily be understood. .
Coal for Lighting Up.
The use of coal for starting a coke fire, as found necessary on the trials described, is off-course quite unnecessary. As 'was pointed out by your correspondent, " C.W.B." (THE_ COMMERCIAL MOTOR, 19th September, 1918, page 87),a coke fire is started de novo quite as readily as a fire of Welsh coal on a suitable grate, but his suggestion cannot be accepted that, for use with coke, a specially-designed boiler is necessary. Competent authorities, like the makers of the Sentinel and Foden wagons, indiCate in their catalogues the suitability of either coal or coke as fuel for either vertical water tube or Imo, type boilers, and even 'strongly and patriotically advocate the use of coke for national and economical reasons (see " Sentinel-News," August, 1918). It is ail unfortunate circumstance that the wagon used for the purpose of these official tests, although a, -popular make, is not a representative type and having in view the vital importance of an efficient transport service and in the present fuel crisis the .utilization of locally-producedfuels, the subject is one that warrants the carrying out of a more comprehensive series of tests under equitable conditions.
E. W. L. Nicor,, Engineer and Fuel Expert, London Coke Committee, 84, Horieferry Road, S.W. 1. • {Since our article dealing with the official tests of North Country and Midland coals for steam wagon furnaces appeared, we have received from the Technical Adviser to the Coal Controller the figures relating to the calorific value of the "Selected Coke" used in the tests. The coke as received showed a calorific value of 8683 B.T.U., but when picked over to size the resulting sample showed a value of 10,019 B.T.U. Those who are keeping the article for future reference may with advantage make the alteration in the table.—En. "O.31.1
Covering Some Points of Doubt.
Certain points in connection with the series of tests arranged by the Technical Adviser to the Coal Controller have come up for criticism or comment, and there are apparently one or two misconceptions to remove.
Comments have been made upon the type of vehicle selected. The reason why the trials were car ried out on a Yorkshire wagon was that, of the large
number of complaints which had been receivedthy the Coal Controller, tile Majority referred particularly
to the Yorkshire wagon, whilst a much smaller number
referred to the Foden, and there is another not unimportant point to consider, and that is that the makers
of the Yorkshire wagon strongly advocate theuse of nothing but the best Welsh smokeless coal tor their furnaces.
With regard to the particular wagon employed, we asked for a photograph of the vehicle and, when we received it, an accompanying message miscarried. It was to tile effect that the photograph had been taken long before the trial, and showed the vehicle fitted with steel-tyred wheels, whereas, in the trials, it ran
on rubber-tyred wheels, and was suitably geared; because, of course, if it were-geared low for a vehicle
with steel-tyred wheels and intended to draw a trailer, the 6-ton load would not have imposed so severe a tax upon it.
The photograph, too, may have riven the impression that the wagon was new or nearly new, and that again would make a difference, but as a. matter of fact it had been at work for quite four years. One criticism that has been made is that the trials would have created a more favourable impression if they bad been carried out on a Foden or Garrett wagon under its full load on ordinary give-and-take roads, the wagon to have been in use for not less than two yeara and to have rim not less than 20,000 miles.
In reply to this, there is a wagon owner in Bath who runs Foden wagons on coal which is much inferior to Welsh -coal. They are two in number, one being seven years old and the other 'nine years old. They are steel-tyred, and have run over 50,000 muss each. They take loads daily of six tons of coal on the wagon, drawing a trailer with three tons, making a, total load of nine tons of coal. They rim daily over an extremely hilly route of nine miles, having to ascend a hill with a gradieat Of 1 in 12 on each journey from the colliery. The coal used is Priston, an inferior Somerset coal, which cannot be compared for an instant with Welsh coal.
The proprietor of the wagons is quite satisfied with Priston coal, and furthermore states that the only difference which he has experienced with the wagons
is that, with Priston coal, he -ages a little More than when he uses Welsh coal on the same journey:But,
of course, this is only what oneovoulel naturally expect, as the calorific value of Priston coal is much below that of the Welsh coal usually used for steam wagon purposes.
The wagons, without the trailer and carrying a, load of six tons of coal, frequently do a journey up
Lansdown Hill, Bath (1i miles). The hill has a gradient at one point of 1 in 61, and the journey is accounted an exceptionally arduous one. With Priston coal, however, steam is well-maintained all the way up the hill.
The proprietor of the wagons has tried Derby house coal and, with this (which many would class as being quite 'unsuitable for steam wagon use) has obtained better results even than with Priston coal.
Locomotive-type Fireboxes : Mr. G.
E. D. Rails.
I have read the article in THE COMMERCIAL MOTOR relating to the urrnparisons of fuel consumption and smoke intensity, carried out on a Yorkshire steam wagon under the authority of the Coal Controller.
I take it that these trials are for the purpose of convincing steam wagon owners that there are few, if any, drawbacks from using fuel other than Welsh smokeless steam coal.
The tests show that the Yorkshire coal is not so economical as Welsh, and that smoke is of greater intensity in the former than the latter. Under these conditions, it would appear that owners should be able to carry on their work without any great difficulty. In my opinion, the tests are not at all conclusive. They should embrace ether types of wagons, particularly those which are fitted with locomotive type fireboxes. I then venture to say, if the trials were carried out over a longer period, it would be found that the evil effects which accrue from using this fuel would soon be apparent, particularly with coke, for coke cannot be efficiently used on a presentday pattern steam wagon fitted with locomotive typo firebox.
I think the best solution of the difficulty would be to allot a percentage of Welsh coal to users of steam wagons who are exclusively engaged upon the transport of war material, for, surely, it is necessary that the transport of this should be as efficiently carried out here at home as it is at the Front.
These trials -may be instructive to some users, but to those who have had experience with steam wagons since their inception they are merely interesting. G. E. D. Rares, M.I.Mech.E., M.I.A.E., • Managing Director, The Birmingham and Midland Counties Transport Co., Ltd.
The Views of "Hephaestus." '
The afrticle in THE COMMERCIAL MOTOR of the 19th October, describing some official tests of sbft coals and coke on steam wagons, is very interesting as far as it goes, in that it shows the possibility of "carrying on" with these kinds of fuels. The complete charts would be extremely interesting, and I should like to know where copies of them could be obtained.
After reading carefully through the article, however, no information can be Lound dealing with the two fundamental factors in the combustion of fuel, i.e,, the type of fire grate and the draught. It is an axiom in steam raising that the furnace should be designed to suit the fuel, and no one 'furnace or grate bar is -equally good for all fuels ; ale() the intensity of the draught required, or, in other words, the amount of air supplied; varies with the kind and 'condition of the fuel and the thickness of the fire. Successfully to Use either bituminous coal or coke necessitates entirely different furnaces. The present problem, however, is to use these fuels in a boiler primarily designed exclusively for Welsh coal, and where possible alterations are very limited but the maximum degree of success can only be obtained by studying the conditions necessary for proper combustion, and applying these as far as it is practicable to do so.
HEMLESTIM.
[The charts -may be examined at the offices of THE COMMERCIAL MOTOR or by arrangement "with the Technical Adviser to the Coal Controller.—En.
140.M.11]