Operators Can Now Convert to Producer Gas with Confidence
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Ward and Morison in Excellent I. of F. Paper Summarize Mass of Valuable Producergas Knowledge. Water Filtration Strongly Advocated to Minimize Cylinder Wear
ON the strength of experience gained in over a million miles of service operation, it is submitted that much greater numbers of vehicles can be converted with confidence to producer gas. This statement is made by Messrs. W. J. Morison, M.I.A.E., of the Tilling Group, and S. G. Ward, Ph.D., F.Inst.F., of the Mining Department of the University of Birmingham, in an Institute of Fuel paper entitled " Practical Application of Gas Producers to Road Transport Including Passenger Service Vehicles," presented on April 30 last.
The paper constitutes an admirable treatise on this matter of vital importance. It is comprehensive, but not unduly long, in view of the large quantity of information it contains; furthermore, it reflects clear analytical thinking, a sure sense of proportion, and full belief on the part of its authors in the truth and soundness of the findings at which they have arrived. Even were the conclusions voiced with less conviction than they are, one could not lightly disregard the opinions of such authorities.
Rigid Economy Imperative Under the heading "Need for economy in the use of imported fuels for road transport," the authors recall a view expressed in 1938 by the Sub-Committee on Oil from Coal,. Committee for Imperial Defence, which was to the effect that it would be better, even in an emergency, to rely on imported liquid fuels than to erect expensive plants to manufacture liquid fuels. Now, they comment, under present conditions, it is imperative that rigid economy should be observed and the fullest use be made of indigenous fuels applicable to road transport. Unless the country make such preparations as the development of producer gas, they emphasize that if supplies from abroad were cut off, road transport would virtually be at a standstill.
Having pointed out the impracticability or limitations of other alternative fuels, Messrs. Morison and Ward review the pros and cons of producer gas. Among the latter are the weight, and the useful space that may be occupied, the low calorific value, cylinder wear, power loss, fuel difficulties and additional servicing. The former include easy storage of the fuel and long-range of operation, the fact that the gas is prepared on the vehicle and generated accord
ing to demand, lower cost than petrol, availability of fuel and the applicability of the fuel to compression-ignition engines.
These advantages far outweigh the drawbacks, they conclude.
Following a consideration of the main types of producer and of the dry and wet-blast principles, there is a short explanation of the process of gas generation and an account of the chemical reactions that take place. This section is particularly enlightening although definitely technical. Then 16 makes of plant are named, all of which have been tried out.
Composition of gas depends on five factors, they point out, type and composition of fuel, moisture content of the air entering the fuel bed, producer design and temperature of fire, the last being again dependent on design, nature of blast (wet or dry), rate of gas output and operating conditions_ , All this having been sorted out satisfactorily, one can the more easily follow the authors' detailed study of gas composition. Major constituents classed as fuel are carbonmonoxide, methane and hydrogen, and as diluents are carbon-dioxide, oxygen and nitrogen. In addition there are a number of sulphur compounds, cyanogen compounds, free and combined ammonia, tarry matter and suspended solids.
Corrosive Gas Constituents A great deal of research has obviously been devoted to a study of this latter group, and not the least interesting and valuable section of the paper is that in which these minor, but notably troublesome, constituents are dealt with. Furthermore, one appreciates the fact that the authors have thus put their knowledge at the disposal of the producergas industry, for the general benefit of the movement, As has probably been anticipated, the relation of these
impurities to cylinder wear is next investigated. Two years' typical wear in 7 or 8-litre engines was 0.001 in. in under 1,000 miles and in some cases in 150 miles.
It was thus decided by the authors that dust was not the main cause of wear, but corrosion. This led to their deciding that a wet gas washer would give better results than a dry filter. Tests proved that wear was much lower when a washer— although less efficient as a dust remover—was employed.
Prominence is given, in the paper, to the deduction that " the dust-content of the gas passing either a dry filter or a wet washer is not, per se, a measure of its relative potential efficiency in reducing the cylinder wear of-producer-gas propelled vehicles." 'It is pointed out, too, that this deduction affects producer design, filter design and fuel selection.
Among dry filters, they remark, is the electrostatic type, and this, of course, is incapable of removing corrosive gaseous compounds.
Seven desirable attributes of a gas-cleansing system are set "out. They are essentially practical, and clearly result from first-hand operating experience combined with scientific investigation.
A description of tests, test equipment, laboratory research, etc., makes enthralling reading. It is illustrated by diagrams including three graphs—two showing filtration effects against gas flow and the third indicating the relation between temperature of gas and sulphur removal.
Perhaps the second of these is the most interesting, in view of the authors' arguments. It indicates the weights respectively of dissolved solids, ammonia, sulphur and suspended solids removed, and the readings are plotted against total gas flow. It clearly reveals how the efficiency of the filter falls, the curves dropping steadily as the quantity of gas passed rises from 2,000 to 10,000 cubic ft.
Sulphur Only Partly Removed We deduce from the paper that sulphur is the most troublesome of the undesirables. In one passage, the authors state that a fuel containing 0.8 per cent. of sulphur will yield a gas containing 36 grams per 1,000 cubic ft. With anthracite doped with soda, however, 5-10 per cent, of the sulphur is retained in the ash. A similar quantity is found deposited in the cyclone filter and cooler tubes, whilst the wet washer removes 10-50 per cent, of the total. Thus 10 grams per 1,000 cubic ft. enter the engine. For the sake of comparison it is stated that, if the sulphur content of petrol be more than 0.1 per cent., corrosion becomes severe.
To explain why cylinder wear is so much reduced by wet washing, despite the incompleteness of the sulphur removal, the authors say that most of the ammonia is extracted and that this has a big influence in the right direction.
In the course of a description of the plant—based on the "Emergency" apparatus—developed and employed by the Tilling organization, the value of upper cylinder lubrication is also emphasized.
Among .the routine maintenance operations outlined, we note that the daily emptying and swilling out of the washer, immediately after service, is given prominence, and the filling of it before starting service. Daily cleaning of sparking plugs is also recommended. The whole of the maintenance operations, including top overhaul every 10,000 miles, costs only 0.3d. per mile.
An average figure for cylinder-wear rate under present conditions is 0.001 in. per 4,000 miles.
' The group is operating. 43 vehicles on producer gas and • two bus depots are exclusively run on this fuel, namely, Igaldon (Eastern National Omnibus Co., Ltd.), _where there are nine, and Cromer (the same concern), where there ate • 12. These two depots save 78,500 gallons of petrol a year, and their services average 48,000 miles per month. The fuel used is mainly anthracite treated with soda. Among otherifuels _tested it has been found , that Suncole , and Oco gave performances comparable with that of treated anthracite.
In a highly informative discourse on fuels, the types available and suitable and the important properties are detailed and summarized: It is specified that fuel should be highly reactive, dust-free and of suitable size. It must not be tar-forming. It should be low in ash, sulphur, nitrogen and chlorine, resistant to shatter and abrasion, of high bulk density, uniform in properties and readily available.
Gains from Activation of Fuel Activated anthracite, the authors state, is outstandingly the pest from several view points. Four important advantages result from treatment of anthracite by sodium carbonate.
On the subject of wet-blast, they point out that by its use the calorific value of the gas is increased but complications in design may be introduced.
To explain the slow progress of the producer-gas movement, the authors name lack of reliable data coupled with "the initial attitude of the Government," cost of conversion and the unsatisfactory fuel position. They conclude this section by remarking that it might be well if the Government imposed a restriction on the price of fuel and guaranteed not to impose taxation upon fuel.
In laying down recommendations for the immediate conversion of certain classes of vehicle, they state that " the portable gas-producer unit has passed out of its initial experimental stages and producer gas can now be regarded as a satisfactory substitute for imported fuels for certain classes of vehicle. The stage has certainly been reached where . . . a much larger number of vehicles should be converted."
They add that each thousand vehicles converted will save about four million gallons of petrol a year and utilize about 20,000 tons of home-produced solid fuel.
We are inclined to regard this paper as the most valuable contribution to the stock of literature available on producer gas that has yet appeared.