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COMPROMISES
a Stepping-si e in Progress
Selecting a Course Between the Obstacles that Cannot be Eliminated and Balancing Opposing Issues Form the Task that Has Got to be Tackled to
Achieve Success There are GoodProspects, Says Our Contributor, that with Confidence and Sincere Endeavour the Present Ugly Duckling May Ultimately Turn into an Elegant Swan
CONSIDERLNG the activity. in connection with producer-gas plants that there has been during the past 12 months, the official figure recently given of 650 vehicles now operating on this fuel on the roads of this country does not carry conviction. Some 10 companies have been engaged in the production of apparatus, so, if the figure be correct, the average output of each is 60. To those with intimate knowledge Of some of these companies, it would seem surprising if several of them had not individually approached the total figure.
There seems to be a tendency, in respect of the fuel for producer plants, to move away from anthracite and towards manufactured fuels of the low-temperature-coke type. Much research is in progress on cokes of low, high and medium temperature, and on the activation of these cokes by chemical means.
It is unfortunate that the fuel known as Stine°le should have gone off the market. In certain directions this fuel was more popular than Progasite It had, of course, the disadvantage of cokesgenerally of light weight per cubic foot, and was, therefore, bulky. It had, however, the definite advantage of reactivity, which showed itself in ease of lighting. Its index of this capacity was 0.02 against 0.035 of Progasite. In certain plants the power developed appeared to be higher, and the gas-filtering problem was no more difficult than with Progasite.
Many operators have been mixing Progasite and Suncole or other low-temperature-coke fuels to obtain the advantages of both. On the other hand, there are those who quite openly use anthracite, as 'they claim they cannot tell the difference between it and Progasite—except in price. • The disappearance of Suncoie was accompanied by. the appearance of several others of similar type. whilst it also left one or two existing like fuefs on the market.
Medium-temperature Process for Manufactured Fuels An attempt is being made to extend the manufacturedfuel market from cokes of the law-temperature process, to. which it has been limited up to the moment, in the direction of the high-temperature process, with the resulting production of a medium-temperature product. This course, naturally, would considerably increase the quantities of fuel available, but it would also be liable to increase the difficulties of filtering the gases for the protection of the engine against damage or destruction, and this risk is already sufficiently great.
To develop such a type of fuel means certain variations, in the processes of gas production 'and, consequently, increased research work on the part of the staffs of the gas-producing plants, which are already keyed up to meet war requirements. Furthermore, the activated cokes add another problem of equal magnitude to this one, so that some time .must elapse before any tangible results to transport operators can be available.
On the other hand, the difficulties of obtaining Progasite at the present time are such that any assistance in the form of an alternative fuel would be of great service. • It is a fact that the installation of a chemical and physical laboratory for the service of a purchasing department automatically puts up the quality of the materials delivered to the company installing the laboratory, even before the first drop of acid is poured into the test tubes. This does not necessarily imply Sharp practice on the part of the suppliers of materials; it might mean that they themselves considered it necessary, in such circumstances, to install their own laboratory (if they had not already got one) as an aid to more accurate knowledge of the materials being supplied to them, which they passed on to others.
Laboratories may be practical possibilities for large companies, but they certainly are not for the owners of small numbers of vehicles. The cost of installing and operating such an inspection system would be prohibitive.
It is doubtful if the collieries would accept the conclusions arrived at in these laboratories, though whether they would state the real reason for their objection is another matter. If they did so they would say that there is no practical means for ensuring a constant quality of fuel from coal Which varies from district to district, from colliery to colliery, and from different parts of the same colliery.
In addition, there is the conviction among operators that those are the actual conditions in the fuel industry, as many of them complain of varying qualities in different deliveries.
There is, of course, also the question of moisture in the fuel. The officially specified limitations of moisture content do not seem to have much practical meaning considering the exposure to atmospheric conditions during transit between the colliery and the consumer, and the alternating dry and wet periods of our weather conditions. Yet some plant makers specify that fuel must be dry—apparently a condition impossible consistently to maintain; consequently, if the plant be designed with this condition as a necessity, its success is imperilled from the start by its non-observance,
Conflicting Factors in Producer-gas Generation Like most things on -this earth, producer-gas-plant operation is the result of a number of compromises. A temperature high enough to generate a sufficient 'quantity of combustible gas, yet low enough to prevent the formation of clinker, and either low enough to prevent the distillation of tar or high enough to destroy it if it be produced, is an example of necessary compromises in this case.
Analysis of the gas at different tittles on the same rim indicates the wide variation in calorific values and in _percentages of gas. Two sets of figures are shown in an accorhpanying table.
Percentages.
Carbon dioxide, CO, 2.5 1.9 Carbon monoxide, CO ... 22.2 32.3 Hydrogen, H, ... 20.1 5.1 Methane, CH 2.0 nil Nitrogen, N, ... 53.2 60.7 B.Th.U. per cub. ft.
Calorific value 155 121
The first point that attracts attention is the poverty of the gas, 55.5 per cent. to 62.6 per cent. being inert. The French express their opinion of producer gas by calling it " gaz pauvre."
During the course of a 100-mile journey_ the calorific value of the gas which starts between 140 and 150 B.Th.U. per cubic ft.. deteriorates to between 117 and 122 B.Th.U. per cubic ft. Gas analyses during the journey show that the CO content gradually rises—from 22 to 30 per cent. or more—whereas the hydrogen content falls—from 15 or more to 5 per cent.—during the same _period. If there be any methane content it decreases from a maximum of 2 per cent, to nil.
Hydrogen content in the anthracite is between 2 and 4 per cent.; the other source of hydrogen is the moisture in the fuel, which the fuel specification permits up to 10 per cent. What it g.ctnally is is another matter.
)000 RPI1.
Poorer Gas as Hydrogen Content Diminishes
The fall in calorific value appears to coincide with the decrease in the hydrogen content of the gas, notwithstanding the increase in the quantity of carbon monoxide.
This fall in calorific value of the gas during the jour-' ney is well known to drivers because it becomes increasingly difficult to obtain sufficient' power from the engine to get the load to its destination, and much wangling of several levers and changing of gears to complete the journey.
The chief reason for this is that the whole of the fuel for the hundred-mile journey is stored in the same box as the fire zone of the producer, working at anything from 1,000 degrees C. to 2,000 degrees C. As it requires a temperature of only 600-700 degrees C. to dissociate hydrogen from water vapour, this is released long before carbon monoxide, which requires 1,000 degrees before any quantity is produced. Below this temperature carbon dioxide is also produced which reacts with hydrogen to produce methane; the decrease in the hydrogen content is accompanied by the gradual disappearance of methane. • At approximately the same temperature as the release of hydrogen, tar is also distilled, and unless the engine is to be clogged up, it must be extracted from the gas in the filtering system.
If the temperature of the fire zone be increased to 1,250-1,400 degrees C., the tar is disintegrated and becomes an addition to the fuel value of the gas. Some plant makers claim this reaction, even carrying the temperature up to 2,000 degrees C.
An unfortunate point in this procedure is that ash fuses in the same temperature range as that in which tar is disintegrated, forming clinker in the fire and upsetting gas production. It then becomes necessary to poke out the clinker and to clear the fire before efficient gas making becomes possible again. The accompanying chart shows the effect of these " clinker hollows " on the b.h.p. curve. It also indicates the comparison of the b.h.p. with petrol in the same -engine, which generally shows a 50 per cent. reduction, but the peak of the gas curve is generally lower by several hundred r.p.m. than -4he petrol-curve peak.
Dynamoineter Tests Query . Wet-blast Theory
In the matter of clinker, some makers claim that the explosive effect of the injection of water or steam into the fire zone breaks up the clinker formation. Others claim that water injection to the fire zone has the effect of adding to the calorific value of the gas, by reason of an increase of the hydrogen content. Dynamometer tests of plants using water compared with those which do not, fail to confirm this contention, as there is no increase in the b.h.p. due to water injection. The extra complication of the water injection does not appear to be justified on this score therefore, and it is also observed that clinker formation is not noticeably, affected either. The only system of gas cleaning known at present is to put obstacles in the path of the gas as it finds its way to the engine, and to try to persuade it to drop its impurities, much in the same way as we get in the path of a dog running away with a bone. The dog generally manages to hang on to his bone, and the gas behaves in much the same manner.
Various substances form these impediments—fabric bags, coke, wood and steel wool, water, oil, sisal, etc., in all sorts of combinations; but reports still come through of damage to and ruin of engines. There is no doubt that neglect in cleaning out the accumulated dust and other impurities from the scrubbers is a cause of engine deterioration. The greater, therefore, is the need for the invention of a fool-proof system to replace the defective one in use to-day. Turbulent washing is a promising recent development.
An interesting point in this system of impedance is that the more efficient it is, the greater, probably, will be the power drop in the engine due to the loss of volumetric efficiency.
The gradual filling up of the filters with coal dust, ash, tar, acids, sulphur, etc., has also the effect of decreasing engine performance, necessitating cleaning out to restore the power.
A completely different system of cleaning, which does not depend for its efficiency upon impedance of the gas, is under consideration in several quarters. This is an electrostatic system, used in town-gas production. The principle is that a high-voltage current acts upon the solid particles in the gas (which is passed through a chamber containing the electrodes), ionizing them so that they are attracted to the walls of the chamber and, along with the united particles of tar, now away out of the gas stream and are collected and deposited for removal.
is the Gas-cleaning Problem Solved ?
There is obviously no impedance with this system, and the current employed is infinitesimal, the voltage being of the same order as that of the usual ignition coil. It appears to offer a cleaning system greatly in advance of the comparatively medival methods in current use. [A brief description of this filter appeared in our issue dated October 4.—ED.] In the consideration of temperature of reaction referred to earlier, the wide variations in engine speed have not been taken into consideration. When we do this, it will be clear that the maintenance of the conditions discussed is subject to the changes brought about by these varying speeds, because the engine is the source of the draught which keeps the fire burning. It can be imagined what happens to the fire when the engine suddenly changes its speed from 500 to 3,000 r.p.m.; the temperature range will be enormous, passing through all the stages discussed above.
It will be seen that all the things mentioned can have happened by this engine action, and it is no wonder that the troubles of clinker formation, bad gas, red-hot producer and bunged-up filter all come in their turn to
make the driver say what I have heard him say of producer plants. When he has coasted down a long hill and opens up to climb the next one, he finds there is no, gas for him, because the fire temperature has gone too low, there being no draught to blow it. CO2 is all there is, which is no use to him,
When he has to get into low gear and race his engine to get up the' hill, he runs into the clinker zone of temperature, and has to get out and poke out the clinker. When he is tired at the end of the day and in the dark he is trying to coax the producer home on reduced power, he has struck the low-powered gas due to the fuel stores being in the furnace box, as already explained.
Roadside Attentions s that May be Needed He might even be forced to clean out his scrubbers on the roadside, as they may have got choked up with foreign matter before theirtime, owing to different, quality fuel; and he may find anything up to a gallon of water in the scrubbers.
With all these Possible troubles, the gas producer is, nevertheless, the only alternative to petrol available to carry on the medium and heavy transport duties so urgently needed. There are several other systems, but they are either experimental or limited in their application, or fuel is not readily available.
We have only to .recall what the beginnings of the petrol engine were to realize the results of sincere efforts put forward, often in opposition to the derision of others, to visualize that the present ugly duckling can quite possibly become the elegant swan of the story.
AZOTE.