Producer gas Proved in French West Africa
Page 34
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TRIALS with a producer-gas lorry I have been carried out in French West Africa with the object of determining (a) the possibility, during a period of hostilities and shortage of petrol, of Maintaining the transport of essential supplies to remote parts of the 'territory; (b) the performance of the producer-gas lorry on the difficult tracks and under the climatic conditions of the Sahara; (c) the feasibility of using charcoal produced from locally grown wood for generating gas. The results of the tests are of particular interest at the present juncture.
They were conducted in Mauritania, by M. Aubreville, Inspector General of Forests of 'French West Africa, on the Morocco track between Rosso and Mar, in one of the hottest months of the year and under most unfavourable conditions.
This track is particularly difficult, involving the' negotiation of considerable tracts of sand and dunes. The vehicle used . was a Latil 2i-tonner, equipped with a Poulenc producer and having coupled wheels which did not take kindly to the frequent deep ruts in the sand. Nevertheless, it gave a satisfactory performance, which, in M. Aubreville's opinion, was at least equal to that of a petrol lorry of equal power.
Striking Economy The load varied between 1 and tons and the amount of charcoal useu was about SS kilos. (84 lb.) to the 100 kiloms. (62 miles). Previous trials had already indicated that with 2 tons, the rate would not have exceeded 40 kilos. to the 100 kiloms., but for purposes of comparison, M. Aubreville used the figure of 45 kilos. (99 lb.). Even so, the economy was striking.
In working out the costs account was taken, in the case of petrol, of loss by evaporation—an important factor to be reckoned with in torrid climates.
The respective total costs on charcoal and on petrol amount to £2 3s. and £10 6s. The details are as follow: Cost of charcoal at 0.5 francs per kilo., for 1,440 kiloms. (900 miles), 324 francs ; of 14 litres of petrol, used for supplementary purposes, at 3.6 francs per litre, 50 francs, giving a total of 374 francs, that is about £2 Ss. Cost of petrol, using 35 litres per 100 kiloms, 1,814.4 francs, that
is about £6 10s, (In the original report 324 is given as 648, obviously in error.) Weight and bulk of fuel are, of course, factors to be considered. The charcoal required for the return trip would weigh 650 kilos. and the petrol 500 kilos. Charcoal is also more bulky. Loss by evaporation, however, and weight of containers are to the advantage of solid fuel.
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Whilst the tracks of French West Africa offer extremely bad conditions and no exaggerated claims are made on behalf of producer-gas vehicles, substitution of wood charcoal for petrol is an economic proposition. M. Aubreville envisages a chain of refuelling depots en route, concluding that there is reason to anticipate that, in the near future, the transport of heavy loads right through to Morocco, will be practicable, given suitably wide and heavy tyres. In such an event fuel economy is of great moment.
Charcoal From Local Wood The advent of hostilities, however, lends more than an academic interest to the experiments, because there is then not merely the question of economy, but also that of ensuring supplies. In this connection, the experience gained with this lorry, using charcoal produced from the wood of the gonakie tree (accacia off. nitotica), so common in Senegal, showed that it would be possible to revictual Atar by means of producer-gas lorries from Senegal, working from a depot at Rosso, even if refuelling depots en route had not been organized.
On the basis of a consumption of 650 kilos. of charcoal for the return journey Rosso-Atar-Rosso, a lorry of 2-5-i tons could carry the fuel necessary for two or three other vehicles in addition to its own supply. If depots were established beforehand, it would be possible, with almost as much facility as with petrol, to assure heavy transport through to Morocco, refuelling being accomplished from the resources of the local forests.
Prior to the maintrip from Rosso to Mar and back, M. Aubreville made a trial trip of 200 kiloms. (125 miles), using charcoal which he had produced at a small carbonization plant set up for the purpose.
The results on this trip were most promising. Consumption was low (32.5 kilos. (72 lb.) to the 100 kilometres outwards, and 30.5 kilos. (67 lb.) on the return, when the lorry was nearly empty). There was no slag or tar and the gas gave good acceleration.
Further trials were made between Dakar and St, Louis, a distance of 168 miles, this time with charcoal produced from the wood of the sourour (accede stemocurpa). In this case the load was
2 tons, and the 'travelling time 7 hrs.
3 mins., with 1 hr. 25 mills, rests. The average speed was 24 m.p.h., and the consumption 40.5 kilos. (89 lb.) to the 100 kiloms.
At the end of the trip the speed slackened so considerably that the lorry could do only 22 m.p.h. This was found to be due to the presence in the firebox of a lump of lime weighing 2 kilos. (4.4 lb.) which impeded the normal production of gas. The soil in the forest where this wood was grown contains a great deal of lime, and on long journeys the resulting residue from charcoal derived from this source becomes a nuisance.
Producer Cleaning The Poulenc generator used on the Latil lorry did not permit of easy cleaning en route, in addition to which the driver had been instructed to proceed, so far as possible, without raking out. Given a generator so constructed as to facilitate easy cleaning, the sourour charcoal, in spite of its lightness, may be regarded as quite satisfactory, whatever the length of the journey.
On the return, charcoal from soump wood (balanites Aegyptiaca) was used and gave remarkably good results. Only a handful of residue was found and the going was as good on arrival at Dakar as at the beginning of the journey—an indication that, with this fuel, long daily journeys could be run without the necessity of raking out en route.
In this case the load was 1.8 tons; travelling tune 6 hrs., plus 33-mM. rests; average speed 45 k.p.h. (28 m.p.h.); consumption 105 kilos. (231.5 lb.), 38.8 kilos. per 100 Idioms.
M. Aubreville concludes that the forests of Senegal and of Mauritania are potentially a rich ,source of supply and that their systematic exploitation, even under present conditions, would make possible an annual production of 2,000 tons of charcoal—enough to supply at least 100 producer-gas lorries, each travelling 30,000 kiloms. a year. He adds that the Forestry Service of Senegal will, in the near future, be in a position to deliver supplies at Thies, in sacks ready for use, at the price of 0.5 franc the kilo,