In the development of central power plants and the reduction of the cost of power, the producer-gas power plant is an important factor. In this connection the question of locating such plants directly at the mines is well worth careful and unbiased attention in the engineering profession. The advantages to be derived from such a location have already attracted the commercial interests of Europe. As examples worthy of thoughtful consideration, the general conditions of operation of three typical European installations are here described:
Plant A.—This plant, although not situated directly at the mines, is but a short distance away, and the company owning the plant also owns the mines from which the fuel is secured. The plant is of the Mond by-product type and consists of eight pressure producers of 2,500 horsepower each. The fuel used is a run-of-mine bituminous coal said to contain 8 to 9 per cent ash and 1 to 2 per cent sulphur. This would indicate that they are utilizing the best grades of coal from their own mine in the local gas plant and allowing the lower grades to remain unmined, a fact which I verified before leaving the plant.
The plant is designed for the recovery of the sulphate of ammonia and for supplying gas to the neighboring towns for both metallurgical and power purposes. As one unit is always held in reserve, the plant is called 16,000 horsepower. The main distributing line is 3 feet in diameter, and at the time of my visit there were 37 miles of main, the longest single run being 6½ miles. Each producer gasifies, on an average, 20 tons of coal per twenty-four hours. The report of the engineer in charge indicates that the plant had been in operation twenty-four hours a day, seven
days a week, for two and one-half years without a shut down.
Plant B.—This plant, which is located in the center of a peat bog, proved of especial interest. It has a capacity of 300 horsepower only, and is about 3 miles from the town to which the electric current is supplied. One-half of the plant (150 horsepower) was installed in 1904 and the remainder in 1906. This is probably the first as well as the smallest producer-gas installation to be located at the mine and transmit high-voltage current to a point some distance away. This installation, in 1909, consisted of two suction producers (special peat type) rated at 150 horsepower each, and two horizontal twin single-acting four-cycle gas engines of 150 horsepower each, direct connected to alternating-current three-phase generators, which were running splendidly in parallel at the time of my visit. The 3,000-volt current is transmitted to the town, where it is used during the day for lighting shops and for shop motors. At night the plant supplies the lights for the streets and residences. The charge for residence light is 9 cents per kilowatt hour. Both units are in operation from 5:30 a. m. to 6 p. m., and one continues to 11 p. m. each day.
A 35-horsepower peat machine is used for preparing the fuel. This is driven by an electric motor supplied with current from the power plant on the bog. As only 750 tons of dry peat are required per year there is no attempt to work the plant to its maximum. Local farmers are employed and they work as little or as much as they please, as there is no difficulty in getting out all the peat needed for a year during the working season, which in this locality is from April 15 to September 1. As a result 14 men are employed more or less of their time. They receive about 50 cents per day each and get out about 20 tons of peat per day.
Coal at this point in Europe costs $3.75 per ton. The dry peat delivered on the operating platform of the producer plant costs only 80 cents per ton.
Plant C.—This plant is installed at the collieries. At the time of my visit it was under full operation, using roof slabs that gave little indication, on casual inspection, of containing any combustible material. It was claimed that this fuel averaged over 60 per cent ash—a claim which seemed entirely reasonable. At the time of this visit (1908) the producers were not only supplying a number of furnaces with gas, but were also operating a 1,000-horsepower and a 250-horsepower gas engine. A 500-horsepower engine was being added to the equipment. The engines in use were direct connected to electric generators. The 10,000-volt current is used for operating the local mine machinery and also for furnishing lights for neighboring towns and power for a street railroad. The plant was reported to be using over 100 tons of this low-grade fuel per day.
Favorable Conditions in the United States.
In the United States cheaper power is constantly sought. The water-power possibilities of the country are being realized and the hydro-electric power plant is a wholesome cause of competition. The supply of fuel of marketable grades is not unlimited. Prices for such fuel must necessarily increase. The cost of transporting coal from the mines is high, and the possibility of obtaining a sufficient supply of cars to handle low-grade fuels is questionable. The power demands of the country are increasing, and this power must be developed at a reasonable cost. The time is approaching when the cheapest fuel obtainable must be used to the best economic advantage in order to develop power at a unit cost consistent with commercial progress.