Capacity of Jet in Scrubber.

In the old layout used, the pump was limited to a suction of 1,100 to 1,200 gallons per minute of warm water. There were fifty-seven sprays, utilizing approximately 1,500,000 gallons in twenty-four hourse.

The new layout has two pumps, with a suction line for cold water from the Bay. There are eighty-seven sprays in the scrubber, each at seventy pounds

CHUTE AND DIGESTERS AT THE BARREN ISLAND GARBAGE PLANT.

THE GARBAGE IS COOKED BY STEAM UNTIL THE GREASE
PARTICLES ARE DISLODGED AND THE MASS IS

READY TO GO TO THE PRESSES.

pressure, passing thirty-one gallons per minute each, or twenty-seven hundred gallons per minute, in all, a total approximately of 4,000,000 gallons in twentyfour hours.

21,100,000 gallons a day

Total pump capacity The garbage is delivered at the plant by scows, from which it is unloaded by grab buckets, operated by derrick, and discharged into scraper conveyors running to the top floor of the digester buildings. From the conveyors it is discharged through swivel spouts to the chutes leading to the digesters. When same are filled, covers are clamped airtight and steam at seventy pounds pressure

is turned in for about two hours; it is then turned off and digestion takes place on the principle of the fireless cooker. This fireless cooker process takes about two hours, when seventy pounds steam is again turned on to complete the process-the entire period takes six or seven hours. While the garbage is being cooked, the gases and vapors are carried through vent pipes to digester vent tanks; and the cooked garbage is discharged into receiving tanks underneath. From these tanks it is passed through one of three presses, where most of the water and grease is separated from the solids, the former flowing through a conduit into grease-separating basins, from which the grease is pumped into storage tanks and the water flows into the Bay.

On leaving the presses, the solids are carried by a conveyor to primary dryers, and from these by another conveyor to the percolators or extractors; while the vapors and gases from the primary dryers are led to a gas chamber and scrubber and from this the gases go to the chimney. The dried material, after leaving the percolators, is carried by conveyors to secondary dryers, the gases from which go to the gas chamber, while the dried "tankage" is taken by conveyors and cars to the tankage storage building, and held ready for shipment.

Going back to the gases and vapors from the digesters-these, after passing through the digester vent tanks with their six-inch jet condensers, are led to a blow-off tank, where the water is separated and discharged into the Bay, and the insoluble gases are led to the furnaces of the primary dryers, thence passin, with the combustion gases from the dryer furnaces, to the dryers, scrubbers, and then to the chimney, before which they are mixed with tar vapor.

The digesters are housed in two buildings, known as the New York building and the Brooklyn building, respectively, the former containing sixty-eight digest

AND GREASE ARE PRESSED FROM THE COOKED GARBAGE AND
RUN THROUGH DRAINS TO THE SEPARATING BASINS.

ers and the latter one hundred and four. Each digester is approximately six feet in diameter and eighteen feet high, constructed with a cone bottom, which is connected to a receiving tank by a large gate valve and nozzle on the bottom of each digester. After the steam has been applied for from six to ten hours, depending upon the condition of the material, the garbage fabric is broken down and the material thoroughly sterilized and digested. The top of each digester has a two-inch vent line for relieving the pressure on the digester after the material has been digested. During the cooking period this vent line is closed by a valve, around which the gases are by-passed by a three-eighths-inch pipe.

The digesters in the New York building are arranged in two batteries, thirtysix on the north side and thirty-two on the south side, with a main vent line six inches in diameter from each battery, to which the two-inch vent lines from the individual digesters are connected. The general arrangement in the Brooklyn building is the same. The two six-inch vent lines in each building are carried to the end of the building, where they discharge into the digester vent tank.

Three types of presses are used in the New York building-roller, steam and hydraulic, but only steam presses in the Brooklyn building, where there is one steam press and one receiving tank for each group of four digestors. The three types of presses vary in design and operation. The roller press is constructed with large cast-iron rolls set in pairs. The bottom of the receiving tank consists of a slated steel apron or belt which, when the press is operating, carries a layer of material between the rolls. The pressure on the rolls is obtained by large steel springs. As the material moves forward, the water and free grease are pressed out, flowing through a conduit to grease-separating basins.

The solids are delivered at the front of the roller press into conveyors which deliver them to the drying building, the whole operation being carried on in closed apparatus. The steam press is constructed with two coned ends, flanged to a center cylinder section with a perforated internal lining. When closed, the press is filled with material from the receiving tank. When filled, 'the con

nections are closed and live steam at high pressure is applied, which presses the material, driving the water and free grease through the perforated lining, and through pipe connections to a conduit leading to grease-separating basins. When the pressing has been completed, the two cone ends of the press are disconnected from the center of the cylinder and elevated, permitting the material to be discharged. The material is enclosed during the pressing and exposed only when discharged on the floor and in the conveyor leading to the dryer building. In the case of the hydraulic presses the material is drawn from the receiving tanks and placed in burlap bags, which are then piled in racks. When a rack has been filled it is placed under the press, which compresses the material, the water draining from it and flowing to the conduit leading to the grease-separating basin. The garbage is exposed during the time of building up the racks and during the pressing, and considerable steam and vapor is given off. The pressed material is carried by conveyors to the dryer building, where it is fed into primary direct-heat dryers, which consist of a large circular shell with a furnace at the feed end. As the dryer revolves the material cascades, coming in contact with the combustion gases from the dryer furnace, thus evaporating the moisture in the material. The dried material is discharged at the rear of the dryer into conveyors, which carry it to the percolating building. In this building it is placed in extractors, where the grease remaining in the material is extracted by means of a solvent. The material is then carried by conveyors back to the dryer building and passed through secondary dryers, which are similar to the primary ones, when it is ready for shipment.

The grease extracted by the presses, together with the water, flows into separating basins, where the grease floating upon the water is removed and pumped into storage tanks.

The vapors and gases from the dryers, both primary and secondary, enter a large continuous chamber at the rear which is connected to the chimney by a flue. Between the chamber and chimney is a steel two-compartment scrubber, in which the gases are passed through water spray to condense and take up the

soluble gases. This scrubber was placed in operation in the latter part of 1914. The water from the scrubber is conveyed to catch basins, where the tankage dust from dryers is allowed to settle; this dust tankage is re-dryed. The tankage collected from the scrubber amounts to several tons a day. The chimney is of concrete, seventeen feet in diameter, and two hundred and twenty-five feet high, has a pressure of 6/10 inches, and not only takes care of the gases from the dryers, but also serves the majority of the boilers of the boiler plant.

The entire process of garbage reduction as practiced at this plant is illustrated in the following diagram:

Scows, GRAB BUCKETS, SCRAPER CONVEYORS AND SWIVEL SPOUTS

SEPARATING BASINS

GREASE

WATER

ANDGASES

DIGESTERS

TANKS

GREASE

PERCOLATOR

GREASE
STORAGE TANKS.

DRIED

MATERIAL

READY FOR SHIPMENT

SECONDARY TANKAGER

DRYERS

JANKAGE STORAGE

GAS CHAMBER AND SCRUBBER

WATER

ANDGASES

DIAGRAM OF PROCESS OF TREATMENT.

The products of the reduction of garbage at this plant are:

Fats.-Fats are put through cold presses to remove stearine and stearic acid used for the manufacture of candles. Tar is removed from the fats, which is said to be better than coal or Carolina tar for roofing purposes. Glycerine from fats is used in the manufacture of explosives.

Red Oil (commercial oleic acid,―oleine).—Best market is in the woolen industry as a lubricant for wool; also used for the manufacture of soaps.

Tankage (screened).—Tankage forms the basis for fertilizer and is prepared according to the requirements of soil and plant. This fertilizer must have fixed proportions of nitrogen (ammonia), potash and bone phosphates. This garbage tankage fertilizer has a great value as it absorbs nitrogen and potash and holds the same until the growing plant is ready to receive them. It is most valuable in southern states on account of sandy soil, as it is not readily soluble and absorbed by the earth. The process of disintegration and solution depends upon the action of plant life, not on the presence of water only, so that it is a lasting fertilizer, whose benefits last from six to ten weeks. The presence of grease in fertilizer delays its assimilation by plants.

GASES

INSOLUBLE

GASES

GASES