CARBURETTED WATER GAS.

Otago Daily Times, Issue 11455, 21 June 1899, Page 6

CARBURETTED WATER GAS.

' . PARTICULARS AS TO ITS CONST! ' TUENTS AND USE.

At the last meeting of the City Council a resolution was' carried instructing the Gas Committee to bring up a report as to the relative merits of carburetted water gas as compared with coal gas, the cost of manufacturing carburetted water gas, and the probable cost of any alterations or additions required to the -present works, to make them efficient fo: manufacturing it. As this would seem to imply that there is a probability of the City ' Council deciding on undertaking the manufacture of carburetted water gas in conjunction with coal gas, some particulars as to the composition, of the former, together witii an estimate of its approximate cost, will be of interest to our readers. > Carburetted water gas must not De confounded with water gas, as it is as different to "it as day is from night. As a matter o[ fact, carburetted water gas is very nearly akin to ordinary coal gas in its constituent elements, as will be seen by the following comparative analysis:— _ C ' ' Carburetted I | , ' Coal gas. , water gas. Per cent. Per cent. Hydrogen ' ..' .. 47.37 40.22 Xight. carburetted hydro-,-gen , ... ■■..;■ ~. 36.04 16.80 leavy hydro-carbons .. 4.97 8.72 .2arbon monoxide .. 6.00 '28.74 JSTitrogea ...... ... 4.63 5.38 Oxygen .. .. .. 0.99 0.14 The advantages claimed for carburetted water gas over coal gas are that it is more easily and cheaply made, while giving a superior; light; also, that for heating and for motive power, it is equal to ordinary pas. . Coal gas, as is well-known, is made by placing .bituminous coal in air-tight retorts, and subjecting'these to a high degree of temperature, thereby expanding, the gas contained in the coal and forcing it but. After leaving (lie re tort it is condensed;, scrubbed, and purified before being used by the consumer. Carburetted water gas is made bypassing steam through incandescent fuel contained in a furnace-pro-ducer or generator. At this stage it is water gas only. This gas is passed over a largo surface of highly refractory material in conjunction . with oils containing hydro-carbons, whi.ph arc first vapourised and then gasified and-form a chemical composition with the water gas. The new gas thus formed is called carburelted water gas. \ THE APPARATUS USED. In England at the present time the apparatus u'^ed for the manufacture of carburetted water gas is made on what is knownl, as the improved Lowe system, or a slight modification of it. The_ apparatus consists of a five-brick-lined generator; connected both above and below- Ihe fuel bed with the top of the carburetter, which.is also.lined with firebrick, the bpttom of which is connected laterally with the adjoining super-heater. The carburetting and super-heating chambers are filled with a chequer work of brick; and at Hie top of the super-heater is a valve for giving exit to the products'of the blasting. During the " run " this valve is closed, and the carburetted water gas h sent on to the scrubbers and purifiers by a side'pipe.. The oil used for earburelting the jjas—and which is usually that known as .Russian " Solar Distillate "— after having been heated by waste gases from the super-heater, is led into the carburetter, where it is introduced in the form of an atomised spray at right angles to the crosssection of the carburetter. The method of working is as follows:—An air blast is forced through the fuel in the generator, raising it to incandescence, while- the products pass on through the carburetter and super-heater, and, meeting a regulated air supply, are burnt off, and heat up the chequer brickwork, after which the products of combustion are allowed to.e?capeinto the chimney shaft. When the fuel is properly incandescent, and the superheater and, the carburetter at the required temperature, the air blast is shut off, the exitvalve in the carburetter closed, and steam admitted over and under the fuel bed. The resulting water gas passes to the carburettei, where it meets with the oil gas produced by the oil heated in the chequer work, and travels on to the condensers and the scrubbers. After a time the temperature in the generator falls, when the steam is cut off, and the fuel is again rendered incandescent by the air blast. This form of apparatus, and all allied ones for making carburetted water gas, have given the only marked success for the commercial utilisation of this gas, and this success must be put down to the doing away with the enormous loss, which, owing to the waste of tho producer gas, the other processes necessitated.

In all attempts to make water, gas, up .'to the end of 1897, the raising of the fuel to incandescence has practically always been obtained by using the air blast in go deep a bed of fuel that the carbon monoxide and residual nitrogen of the air formed the chief resultant products. The Delhvik process of making water gas necessitates the keeping the level •of the incandescent fuel in the • generators at a constant height. 'Under ■ the conditions the producer gas ceases to exist as a by product, and the products of the blow consist merely of- the ordinary non-combustible products of complete combustion—carbon dioxide and nitrogen—the result being that double the Quantity of water gas can be made ncr nound

of fuel than was before possible, and the extra heat generatedl minimises the period of blowing and enables runs of steaming to bo continued far longer than has been possible before. In the old " European" " process it was iiecepsary'to blow for noarly 10 minutes to bring tho fuel bed up to the right temperature, while Ihe period during which.(he incandescence was sufflciently great to decompose the whole- of the volume of tho steam used limited steaming from four to five minutes ; whereas in tho Dellwik process the period of blowing rarely exceeds two minutes; and it is possible to steam for from" seven to ten minutes according to the condition of the fuel. INCAN DESCENT MANTLES. Au even greater development will, however, probably be found during the next lew years, in the use of pure water gas for uut-dooi illumination by means'of incandescent mantles, and for the generation of power by means of suitable' gas motors. The successful introduction of water gas for these purposes entirely depends upon the cost of production, and whereas, under tho ' European" system, the water gas costs from 4cl to 6d per 1000 cubic feet, according to the size of the installation and the price ol iuel, the cost could now be reduced on a large installation of the Dollwili plant to below 3d. ' , , AN AUXTLIARy TO COAL GAS. It is not proposed that carburetted water gas should entirely supersede1 coal gas, but that it should be used as an auxiliary. The corporation gasworks are at present, too small to yield an adequate supply for the city s requirements. ' Carburetted water gus is made so rapidly that the holding capacity ol the works would be increased. It is claimed that by-mixing coal gas with a proportion of carburetted water gas, ■ the illuminating- power would be raised from 17 candle-power to 23 candle-power. Reverting again to the analyses given at the outset, it will be noticed that the most I marked difference in the composition of the | two gases is in tho proportion of carbonic I monoxide. Coal gas contains per .cent. ■ and carburelted water gas 28.74- per cent. i This is tho dangerous element in this pas. . Professor Lewes, chief superintending gas examiner to the corporation of the City of | London, says that it must he clearly borne in mind that carbon monoxide is the most dangerous gaseous poison there is, and the attempts made by some supporters. of carburetted water gas to gloss over this fact are as mistaken .as they, are mischievous. I'he only proper way to attack this question 19 to grasp the fact of the dangerous properties of this gas, and then so arrange the percentage of the town supply that only under abnormal and accidental "conditions, impossible to prevent, should it becomo dangerous; the same conditions being'equally a source of ■ danger • with the'ordinary gas supply. After making an elaborate calculation, Professor Lewes comes to the conclusion, that carburofted water gas can be mixed with coal gas'to the extent of 50 per cent, without incurring any, more • danger than is attendant on the use of coal gas. This gives a proportion of 17 per cent.° ot carbon monoxide,- and it should be clearly understood that it should not be exceeded. Under these conditions, the mixture is perfectly safe as a town supply.. It is worthy of note, however, that in America,-70 per cent, of/ the gas used for lighting is carburetted water gas,' 'and the remaining 30 per cent, coal gas.' Chicago and Boston both -use the carburetted water 'gas "in its pure state. ■ • ' THE QUESTION- OF COST-. The next question is that of cost. When ' this gas was installed at Blackburn in 1895, it was found that, the cost per 1000 ft. averaged about Is 2|d, which,was made up as follows: Cost of. oil,' 11.86 d: coke, 1.29 d: water, 0.48 d; wages, 0.73 d; wear and tear, 0.50 d. Put in another form, - the following shows the cost to manufacture 5,8C6,000 cubic feet during a full week's working: — Oil used, 19,268 gal at 3gd par gallon £291. 0 6J Coke used, 95 tons, 17ewt"lqi<,at 6s ' ' 8d per ton ... ■~ ..''.. '31 15 9 Water used, 472,000 gal at 6d per ' "lOOOgal •. ii 16' o Wages (manufactiire and" purifiea-. ti°n) •• .. ; ..,•... 17 19*9 Wear and tear, oil, waste, etc., estimated ... .. •-,... 121 5 3 The price of coke at the Dunedin Corporation gasworks at tho present time is 18s 6d, while oil for gas-making -purposes ( may bo imported duty free,' and might be "possibly got for 5d or 6d. This would bring up the price'per 1000 ft very considerably.- If, however, as is anticipated, -the working of the shale deposits at Orepuki- should -prove a success, the New .Zealand'Collieries'and Oil Syndicate may be in a position .to pub New Zealand crude petroleum on ,the market at a cheaper price than,that above-mentioned. In any case, the.cost of manufacturing carburetted water gas is not expected'by those who have looked into, tho' matter, to exceed Is 8d per 1000 ft. This/mixed with 50 per cent, of coal gas,' should permit pf a very considerable reduction on- the current rate. Further, tho saving in labour is immense. In the Belfast works,, where .the mehl'work in eight-hour shifts,- each operator will make from 250,000 to 300,000 cubic feet, so that to produce the required '6,000,000 ft per • diem, the services of 20 to 24- 'operators would be required. To make the same quantity of coal gas, that corporation had to employ 340 stokers. . ' - "

The nature of the work in the operation of water gas plant is very different from that required in the manufacture of coal' ga^. There is no se\eie labour, and the operator may keep himself clean and tidy. Few men not in good physical training can face the work of an oidinary gas stoker, but Uio light nature of the duties of ail 'operator in the working of a water gas plant render it possible for any mail of ordinary physique to engage in it, and carefulness, steadiness, and intelligence are characteristics- to ba looked for rather than great strength. , That carburctled water gas has found favour in other part? of the world may be seen by the fact that one comoany in Lon- ■ don makes 6,500,000 ft daily. Liverpool and 1 Manchester each consume. 3,500,000 ft, 'while I New York requires 11,000,000 daily. "