Tests and Notes on Operation of Gas Producers
The Grand Rapids, Mich., Hydraulic company has had experience with gas-producers and gas engines since November 1, 1906. The plant was installed at various times during the preceding six months, so that on date it consisted of two complete units, each unit comprising a producer, an engine, and a double-stage centrifugal pump, belt driven from gas engine. The first plant consisted of two 70-horsepower, suction gas-producers, two 60 horsepower engines, and two double stage centrifugal pumps. The engines were 15¾ by 28 in., with a maximum horsepower of about 70, when running at 190 revolutions per minute The producers had 26-in. circular grates. The pumps were 6-in, discharge, and were rated at 1,000,000 gal. per day of twenty-four hours against 200 ft. bead. It soon became apparent that the hydraulic company was in possession of producers that were too small for the engines, too small for pumps, too small for its business. With this unhappy combination, we naturally experienced considerable trouble. In remedying our trouble we lirst started at the producers, adding a large producer with a hi in. circular grate in April, 1907. f inally it was deemed best to re place the original plant in its entirety with a larger plant. The contract was let during 1908, and called fur one additional producer of hi in. circular grate, two 100-horsepower engines, and two triple stage, centrifugal pumps. In Decern her, 1908, u was decided to change the type of pumps, and, instead of buying centrifugal pumps, the contract was let for two triplex pumps. AH of the new machinery was finally installed during March, 1909. l ull value of the old plant was allowed by the Minneapolis Steel and Machinery company, the contractors, when the new plant was purchased.
GENERAL OPERATION OK OAS PRODUCERS.
It is assumed that the gentlemen present are familiar with the operation of a gas producer plant, as the same was clearly brought out at recent conventions of this association. However, briefly. the operation is as follows: Anthracite coal of pea si/e is used, and the tire blown by one of the blowers, until such time as the gas tests out at the various test cocks as being suitable. Ihe products of combustion escape to the atmosphere through a pipe: no stack being necessary. As soon as there is suitable gas at the engine test cock, the blower is stopped, and the plant is ready to be put in operation, provided that you have sufficient air on hand. Manufacturers state in their catalogues that 90 lb. is sufficient: but our experience has shown that HO is nearer the figure. The suction stroke of the engine is the only draught that the producer has. This draws air and steam through the producer, the steam being furnished by the vaporiser, and the air through a pipe leading to the grate. The result is the formation of gas containing carbon monoxide, car bon dioxide, nitrogen, hydrogen, marsh gas, etc. The carbon monoxide is wliat you are after. These gases pass through the producer to the scrubber, entering the scrubber at the bottom. The scrubber is tilled with coke, and a water spray is attached from the top, so that the gas comes in contact with water and coke, which tends towards purifying it and withholding any particles of carbon that may have come over from the producer. The gas then goes from the top of the wet scrubber direct to a tank near the engine, or, in some cases, it first passes through the dry scrubber, a low tank in which there are several trays containing excelsior, corncobs, sawdust, or some other constituent that tends to dry the gas, which will withhold any impurities that may pass through the wet scrubber.
It is my endeavor to furnish as near as possible, a practical paper rather than scientific, and for that reason the manner in which we operate our plant will be given. We use anthracite pea coal. Pennsylvania coal, known on the market as Cross Creek, which is purchased through local dealers. This coal, though comparatively clean and free of slate, is screened again before being used in the producer. We feed the producer every second hour, but poke it only once every twenty-four to forty-eight hours, opening the grate-doors to do this. We run the plant continuously twenty four hours per day and Sunday. using one unit. Whenever necessary, in order to maintain the pressure, the second engine and pump are put in operation. We can operate both engines off either producer for a short time, although we find it more satisfactory to have both producers in commission, when running both engines. The plant is arranged, so that either producer can operate either or both engines through either or both scrubbers. In starting the engine, we always aim to have 140 lb. pressure in the air tank ,and a hot spark-plug. The first impulse we give with air, and at the proper cycle we generally give a second shot of air, simply as a precaution. We find that we can invariably start the first time by doing this. In starting, we always leave the ash-bed doors of the producer open. This is done, so as to prevent a blowback, which would follow, in case the inlet-valve were held open by a piece of carbon. The cylinder is oiled by means of the pump, while all other bearings are properly oiled, either by cups or by running through oil wells. Once the engine is in operation, the operator has to take the usual precautions of examining all oil cups, bearings and cooling devices. We have the engine so arranged that it can be speeded up or lowered while in operation, this being done by means of a heavy spring of considerable tension, which is used to throttle or open up the governor valve.
No friction-clutch is used on the pumps. Each pump is equiped on the charge-side with an airchamber. a 10-in. check-valve and a 10-in. gatevalve. The discharge and suctions arc connected tip by two 6-in. bypass lines, on which arc located a 6-iti. discharge-screw and yoke, bypass valve and a 6-in. relief-valve. The 6-in. relief-valve works automatically, blowing off when the pressure is 9.1 ib. There is a vacuum-chamber on tin suction side. The bypass is used in place of a friction-clutch in starting up the pump. When an engine is started, the force-main pressure is withheld from the pump by a 10-in. check-valve. Before starting, the 6-in. relief-valve is opened wide. The suction-line is primed through *n 2-in. line, there being a 12-in. Ludlow foot-valve on each suction-line. As soon as the engine is up speed, the pump raises the pressure, so that the cheek-valve opens, and at this time the operator closes the 6-in. bypass valve, ft takes about five minutes for the engine to get up to its proper speed and the pump to begin pumping water.
Labor.—A great source of trouble is inability to get the proper men as operators. Wc have bad. all told, in various capacities in our olant. for the past two and one-half years over twenty four different men on the pay roll. It has been a case of “hire and fire,” until wc managed to get the present force together, all of whom have been with us. with one exception, better than a year. We usually found that a man who had any knowledge of an automobiline or a gasoline engine, would set himself up as a gas engine operator, and, in nearly all cases, demanded wages far and above that paid to steam men. for the same class of work We were turnished several men by the manufacturers: but these did not prove satisfactory. We bad men with six weeks’ experience operating gas engines, demanding 890 per month and getting it for a short time, as for a while wc were completely at the merev of this class of labor. The labor condition has improved considerably, so that now it is not as hard a proposition to get experienced men.
Salvage—Salvage is an absolute necessity, in order to fulfil guarantees, where the producer operating is smaii. When we had the 26-in. producers. we poked these producers every hour and bad to open the doors and clean the grates. In consequence, there was a large loss of good coal fire, which, after cooling wc screened, and put back in the producer. Tn the large producer we now have, we poke so seldom that there is little or no coal salvage, as all of the product removed from the producer, is in the form of ash.
Poke-Holes.—When the present large producers were first installed, they were equiped with poke-holes at various elevations round the circumference. They had. also, four poke-holes at a level with the grate, our past experience having taught us that it was easier to clean fire at short intervals through small poke-holes, than it was to open the large doors. As things now are, we do not use these poke-holes at all, except occasionally to examine the interior of the producer, to see at what point our fire is. Each producer is equiped with poke-holes at the top, through which we had intended cleaning the sides of the interior brick work in the producer. Our experience has taught us that it is well, if your producer is of sufficient capacity, to leave the producer absolutely alone, except to add coal, when needed, and to poke the fire as little as possible. The top poke-holes are used now, only when cleaning a cold producer.
Vaporisers.—-Out; No. 8 producer is provided with a steel water pan on top, instead of a separate vaporiser. We have not had an opportunity to test the two vaporisers, so as to show which is superior, as the No. 7 producer has a separate vaporiser. The steel vaporiser on No. 8 has given excellent satisfaction and furnishes steam in sufficient quantities to make good gas. In the vaporiser of No. 7, which is moulded like a water-tube boiler, we have had to replace the tubes once in eighteen months, because they had been eaten away by the gas. The reason given by the – manufacturers for abandoning the saparate vaporiser, was that a separate vaporiser steams more slowly. They also seem to be in need of repair oftener than the steel vaporiser.
Dry Scrubbers.—We abandoned the dry scrub her, as we felt that their presence caused the engine to work harder, and. bv screening the coal in advance, we were satisfied that the dry scrubbers’ use was nullified. We also thought that the dry scrubber, unless absolutely airtight, would interfere with the operation of the engine and was the one dangerous point in the system, where there was a possibility of an explosion. By doing away with the dry scrubber, the operator is able to use more air in bis mixture of gas and air at the engine.
Cylinder-Heads.—Our cylinder-heads are water-cooled : but it is permissible to run them warm, without there being any danger. The water that we serve is not a soft water, and for that reason wc allow it to run more freely, so as to do away with the possibility of plugging a valve, the annular space with scale, and we found it necesasry to have absolutely airtight valves between the producers.
Valves.—When the small producers were in operation, our piping was not what we wanted, inasmuch as we contemplated a larger producer later, so, on a number of occasions, we had ex plosions, due to the fact that there would be lire in the small producers at the time we were blowing up the large producer. The gas being blown over from the large producer through leaking valves in the small producer eventually meant trouble. This has since been obviated on the new plant. All valves should be tested twice each month.
Grates.—The grates in the small producers have a tendency to burn out quickly, and we found it necessary to renew the grates in both small pro ducer.s twice. We have not found this condition in the large producers, one of which has been in operation more or less since 1907.
Repairs.—Tn a general way w’c found the repairs on the producer to be very slight. Barring the possibility of prate-renewals and renewal of fire-door liners, there is little or nothing to be provided for. In the event that the operator lets his fire get too near the top, some trouble maybe experienced. The top might possibly crack, or rivets might be burned sufficiently to permit of air-leaks at the top of the producer, and. under these conditions, it is next to imposible to get the gas of the proper quality.
Necessary Extras.— ft is always well to have on band one each of the following: Spark-plugs, trip-rods, magnetos, a quantity of mica washers to be for insulation in the spark-plug and extra springs necessary in connecting up the ignition mechanism. An extra crank-pin box is also a convenience. An extra valve for the gas-cock should be kept on hand, as occasionally the valve will set. and. in trying to open it, it is possible that the handle would be broken off. This has happened on one occasion with tts.
The Hydraulic company has a spring-water supply carried by the gallery system to a central suction-well through 2.r>00 ft. of 20-in. tile line, with open joints. This tile line run through gravel and clay, the joints, of course, being closed where the line passes through the clay. The suction-well is brick, built on an iron shoe, and is 20 ft. in diameter and 20-ft. deep. The well is 125 ft. from the pumping station. There are three 12-in. suction-lines and one 8-in. line running to the puntping station. The 8-in. line is not now in commission, having been formerly used with one of the centrifugal pumps. Two of the trixplex pumps are connected each to a 12-in. line, and a Blake compound steam pump of 1,500,000 gal. capacity is connected to the other 12-in. line. We have, also, a Deane compound condensing steam pump which can be used, and this gets its supply from one of the 12-in. suctions that is connected to one of the Deane triplex pumps. The pumps discharge into the 12-in. force-main which pumps direct into the system. There is a standpipe located 3 miles from the plant, which is used as a storage for any surplus. The average pressure, excepting in summer, is 85-90 11)., in summer, 90-110 lb.
“Paper read at the 29tli annual convention of the American Waterworks Assn.; June, 1909.
CONTRACT AND TEST PRELIMINARIES.
The contract betwen the Minneapolis Steel and Machinery company and the Grand Rapids Hydraulic company called for the installation of 2 100-horsepower, Muenzel, gas engines, 1 No. 8 Muenzel gas-producer, having 46-in. grates (the No. 7 producer had been installed a year before), 2 3-stage centrifugal pumps, each with a capacity to pump 1,000,000 gal. of water in twenty-four hours at gauge pressure of 120 lb. at the pump. Each engine was guaranteed to be capable of operating to its full capacity each pump. The company guaranteed that each engine would deliver 1-horsepower per hour on 1 lb. of pea anthracite coal on any load between 75 to 100horsepower, and on 1J4 lb. on any load between 50 to 75-horsepower, provided the coal had a calorific value of not less than 13,500 b.t.u. The engines were guaranteed to regulate within 2 per cent, of normal, under all natural changes of load. It was also guaranteed that the banking of the fire should not require more than 20 lb. of coal per hour. The No. 8 producer was guaran teed to he equal in capacity, workmanship and material to the No. 7 producer, purchased in January, 1907. The usual guarantee as to workmanship and material for one year was given. The contractor was relieved of the pump-guarantee, when it was decided to install triplex pumps, instead of triple-stage centrifugal pumps. The pumps were guaranteed by the manufacturer, the Deane Steam Pump company, to deliver 1,184 gal. per minute against 100 lb. pressure, at 40 R.P.M. An efficiency-guarantee of 78 per cent, was made, also, the usual guarantee as to workmanship and material.
The object of the test was to determine, if all these guarantees had been fulfilled, and, also, to determine the general efficiency of the plant. The producers are known as the No. 7 and No. 8 Muenzel producers. Both producers have the same size grate-area, 46-in. in diameter; but die No. 7 producer has a 56-in. fire-pot, and the No. 8 a 48-in. fire-pot. The No. 7 producer’s overall diameter is 6 ft. 6 in. and (lie No. 8 5 ft. 10 in. The No. 7 producer is 10 ft. 3 in. high, and the No. 8 7 ft. 6 in. The No. 7 producer has a sparate vaporiser, and the No. 8 has a superimposed vaporiser. The No. 8 producer has a removable grate-platform, the grate-platform and ashpit sliding out on rails. The No. 7 producer has not this arrangement, as it consists of one complete shell. Only wet scrubbers are installed; these arc cylindrical steel shells, each 3 ft. in diameter, and 10 ft. high. The starting devices consist of a type A. Olds gasoline engine 2(4horsepower, a blower, and a single cylinder aircompressor, the air-storage tank being 24 in. by 5 ft. The engines are the Muenzel, single cylinder. 4-cycle, with 18¾-⅛11. cylinder and 28-in. stroke. One engine is right, the other lefthand. Each engine is guaranteed to be 100-horsepower capacity, at 190 revolutions per minute. The pumps are the vertical, double-acting, triplex pumps of the Deane type, one right and one lefthand. Each has a 12-in. stroke, and 11-in. cylinder. The pumps arc belt-driven from the engines, the belts being 14-in., double, extra heavy stock, running 30 to 33 oz. to the foot, and are made of short oak tanned leather. The gas engine pulleys are 86 in. in diameter and the belt pulleys 80 in. The pumps are geared 4.64 to 1.
The test was conducted on June 1, 2 and 3 by five writer, who represented the Grand Rapids Hydraulic company. J. J. Wernette, a mechanical engineer, of Grand Rapids, represented the Minneapolis Steel and Machinery company.
It was the intention to test one of the producers from cold start, and the second, which was in operation at the beginning of the test, was to have been tested from a hot start. The producer, however, that was then under fire had been running steadily for eleven days previously, and it began to show signs of a deterioration of gas, the engine lagging occasionally. Fearing a possible shutdown in the middle of the test, it was decided to clean this producer also, and test both plants from a cold start. Being cross-connected the conditions at the time of the start, necessitated running No. 1 engine from No. 2 producer. Upon completion of the 24-hour run, No. 1 producer was put in operation and furnished the gas to drive No. 2 pump.
As the test was made under working conditions, and, as we are required to operate twentyfour hours daily, we were unable to determine definitely the brake horsepower. We assumed a mechanical efficiency of 85 per cent. The test was then made by firing each producer in turn, running each approximately twenty-four hours, and then pulling the fire and weighing the salvage. The No. 2 producer was given two runs— one of approximately twenty-four hours and one of about three hours. Between these runs the producer was banked. This was done, so that we could make a bank-test. It was impossible for us to determine the slip of the pumps. The pumps are new and have been in operation only two months. A close examination failed to show any great slippage. So that the slippage of pumps was asumed at 5 per cent., which we think is an outside figure. Our standpipe is sev eral miles away from the pumps, and the sys tern is direct pumping, with the standpipe to take care of the surplus, so that, although we could pump into the standpipe, it would not give us any indication, inasmuch as there are many heavy users on the main line, before it reaches the standpipe.
The gauges, meters and scales used during the test were tested and found to be correct. In determining stand by loss, the No. 2 producer, after completing its first run, was thoroughlyshaken, the lower doors opened at the grate, and all ash and clinker that could be removed. The height of the coal above tingrate was then measured. The producer was allowed to stand, all doors and poke-holes being closed tight, and no coal added for twenty hours, at which time the prodtlcer was again thoroughly shaken down and the height above grate measured. The difference was 2 in., and, knowing the interior diameter of the fire-pit, the cuticle contents were determined These 2 in. of coal burned were considered as dry partially burned coal, and a determinationw.-is made to get at the weight per cubic foot. After each producer had made its run, the fire was pulled. No account was taken of the ash, as we simply wished to determine the value of the salvage—meaning the coal that we can again use in the producer. As soon as the fire was pulled; the hot coal was thoroughly wet down. A determination was made to get at the difference in weight between a cubic foot of dry unburned coal and dry partially burned coal, and wet partially burned coal, and it was found that the wet coal weighed 8.3 per cent, more tliaif the dry partially burned coal, and the dry partially burned coal weighed 3.3 per cent, less than the unburned coal. For making this determination the net value of the salvage, considered as good coal was determined.
No. 1 pump, when put in operation, caught its prime, and started pumping water in five minutes. No. 2 pump did the same thing in four minutes The tests were considered to have begun at the time the pumps started doing work. The time the engines were running light was considered as stand by loss. Tt was necessary to shut down, in order to remove the reducing motion from the engine. The reducing motion was removed ; and the engine was put in operation; and the pumps were started pumping in seven minutes, which, however, is an unusual record. Following the completion of the test on No. 1 producer and the drawing of the fire, the producer was thoroughly cleaned, refilled with coal and put back in operation in three hours and twenty-four minutes. This necessitated the handling of all the salvage, and the filling of the producer for the new run with approximately 1 ton of coal, all of which had to he handled in buckets, carrying 80 lb. each. This is given to give an idea of how soon a producer of this size can be put in operation.
We were unfortunate in that the revolutioncounter on pump No. 2 got out of order during the middle of the run. Careful determinations, however, had been made of the R.P.M. of the engine, the pump-pulley and the pump-crank. From these readings an average of the R.P.M. of the pump was obtained. We had an accurate determination of the R.P.M. of pump No. 1, and pump No. 2 was found to be within .6 of a stroke per minute the same as pump No. 1. A comparison of the R.P.M. of the two pumps during the time that the counter on pump No. 2 was in working order showed that during the corresponding hours pump No. 1 was running at a slightly greater speed than pump No. 2. This slightly increased speed of pump No. 1 over pump No. 2 was constant throughout the first twelve hours of the test, and for that reason we believe that the final R.P.M. of pump No. 2, which is slightly under that of pump No. 1 is correct. All readings were taken from thirty minutes, except when the counter of pump No. 2 became out of order, after which readings of the R.P.M. of this pump were taken at fifteen minutes duration. No effort was made to determine the amount of water that the vaporisers and scrubbers used separately. A test similar to that had been made at different times, and we wanted to get an idea of how much water was used for all purposes throughout the plant, except domestic uses.