In the case of common printings and writings, which form the great bulk of the paper made, the possibility of one mill competing against another, apart from the important factor of the cost of freight, coal, and labour, is almost entirely determined by the economy resulting from the introduction of modern machinery.

The equipment of an up-to-date paper mill, therefore, comprises all the latest devices for the efficient handling of large quantities of raw material, the economical production of steam, and the minimum consumption of coal, matters which are of course common to most industrial operations, together with the special machinery peculiar to the manufacture of paper.

The amount of material to be handled may be seen from the table on page 215, which gives the approximate quantities for the weekly output of a common news and a good printing paper.

Economy in Coal Consumption.—The reduction to a minimum of the amount of coal required for a ton of paper has been brought about by the use of appliances for the better and more regular combustion of the coal, such as mechanical stokers, forced and induced draught, the introduction of methods for utilising waste heat in flue gases by economisers, and the waste heat in exhaust steam and condensed water by feed-water heaters, the adoption of machines for securing the whole energy of the live steam by means of superheaters, adequate insulation of steam mains and pipes, high pressure boilers, and engines of most recent design.

The firing of steam boilers is now conducted on scientific principles, the coal being submitted regularly to proper analysis for calorific value, the evaporative power of the boilers being determined at intervals by adequate trials, the condition of the waste flue gases being automatically

Table showing the Materials required for News and Printings.

The Sarco Combustion Recorder.—This instrument is a device which automatically records the percentage of carbonic acid gas in the waste gases from boiler furnaces. The flue gases are analysed at frequent and regular intervals, and the results of the analysis can be seen on a chart immediately, so that it is possible to determine the effect of an alteration in the firing of the boilers within two minutes of its taking place. The apparatus is rather complicated, but the principle upon which it is based is simple.

Measured quantities of the flue gases are drawn into graduated glass tubes and brought into contact with strong caustic soda solution, which absorbs all the carbonic acid gas. The remaining gases not absorbed by the caustic soda are automatically measured and the percentage of carbonic acid gas registered on the chart.

The use of suitable boiler feed-water is also an important factor in modern steam-raising plant. The hot condensed water from the paper machine drying cylinders, and exhaust steam from the engines and steam-pipes, is returned to the stoke-hole to be utilised in heating up the cold water which has been previously softened by chemical treatment.

Water Softening.—The water softeners available on the market are numerous, and as each possesses special advantages of its own, it would be almost invidious to select any one for particular notice.

They are based upon the principle of mixing chemicals with the water to be treated, so as to precipitate the matters in solution and give a boiler feed-water free from carbonates and sulphates of lime and magnesia. The chemicals are added in the form of solutions of carefully regulated strength to the water, which flow in a continuous stream into a tank. The flow of the water and chemical reagent is adjusted by previous analysis.

The various machines differ in details of construction, and in the methods by which the mixing of the water and reagents is effected. The object to be achieved is the complete precipitation of the dissolved salts and the production of a clear water, free from sediment, in an apparatus that will treat a maximum quantity of water at a cheap rate per 1,000 gallons.

The process needs proper attention. The addition of reagents in wrong proportions will do more harm than good, and possibly result in hardening the water instead of softening it. The following may be quoted as an example:—

Treatment required: 1·8 lbs. of lime, 0·2 lbs. soda ash per 1,000 gallons. Apparently 5·5 lbs. of lime were being used and no soda (Stromeyer).

Superheated Steam.—The effective application of the energy of the high pressure steam is probably one of the most important problems in paper mill economy. The use of superheated steam is being extended in every direction, and, in addition to the advantages obtained in the steam engine itself, its wider possibilities for the boiling of esparto, wood, and fibres generally have been noted. The following case may be quoted as the result of a trial at a paper mill, showing for stated conditions the advantages of superheated steam:—

This appears to show a saving of 12 per cent.

Gas Producers.—The substitution of gas for steam in the paper mill has not yet proved a success. The fact that heat is required for the drying cylinders of a paper machine, and that the heat is most cheaply and readily obtained in the form of exhaust steam from the engines driving the paper machine, militates considerably against economies which might otherwise be possible. The difficulties of heating such cylinders, or rather of properly controlling and regulating the temperature by any other means than steam, may easily be surmised.

Gas engines of over 200 h.-p. seem to give considerable trouble at present, but no doubt in course of time the required improvements will be effected.

It is generally supposed that gas producers can only be economical when utilised for the production of gas on a large scale, and for distribution to engines of smaller capacity than the main steam engine required in a paper mill. The peculiar conditions of the manufacture of paper do not appear to be favourable to the adoption of the gas producer system in its present form.

Motive Power.—The paper-maker has taken advantage of every modern improvement in steam engines for the purpose of reducing the cost of motive power. Amongst other alterations in this direction the use of a high speed enclosed engine and the employment of the modern steam turbine may be noted.

In the enclosed engine the working parts are boxed in by a casing fitted with oil-tight doors. The cranks and connecting rods splash into the oil, which is thus thrown about in all directions, so as to ensure sufficient lubrication. Another feature of this engine is the variable speed, and it is possible to run the paper machine at speeds varying from 100 to 500 ft. per minute without the use of change wheels.

Electrical Driving.—The application of electricity for motive power has made steady advances in the paper mill. At first it was limited to the driving of machinery in which variations of speed or load were not required to any large extent, but of recent years beating engines, calenders, and paper machines have all been fitted with electrical drives.

The following details relate to the installation at the Linwood Paper Mills:—

The installation consists of 250-K.W. steam dynamos. The engines are Willan's high speed triple expansion, working with a boiler pressure of 250 lbs. per square inch at the stop valve, the steam being superheated to give a temperature of 500° Fahr. at the engine. By means of jet condensers a vacuum of 25 to 25½ inches is obtained on the engines. The two boilers are of the Babcock type, and have 3,580 square feet of heating surface each. The furnaces have chain grate stokers, and the boilers are arranged with their own superheaters. The motor equipment consists of eight 80, two 50, and ten 25 B.H.P. motors.

Six of the 80 B.H.P. drive the beating engines, and it has been found that the motors readily respond to an overload of 50 per cent. without beating or other trouble. To remedy the excessive and sudden variation a belt drive was adopted. An 80 motor drives the pulp refining engine. The two paper-making machines have each two motors, one a 25 and a 50 and the other two 25 B.H.P. motors. The speed can be regulated with exactitude. The auxiliary plant of the paper-making machine, pumps, agitators, etc., is worked from lines of shafting driven by motors.

Calender motors are of the variable speed type, being designed to run from 100 revolutions per minute to 600 revolutions per minute. Variations from 300 to 600 revolutions per minute can be regulated by the shunts, the loss being negligible. Several of the motors are geared up to the various machines, as is the case with the calender.

As regards cost, the capital outlay on the 500-K.W. generating plant, including engines, dynamos, boilers, condensers, steam pipes, filters, etc., and all engine room accessories, was £9,500.

In addition to the above, the plant also contains a Parson's steam turbine of 1,000 K.W., driving two continuous current dynamos.

The Eibel Patent.—One of the most important improvements in connection with the manufacture of newspaper is the Eibel process, designed to increase the speed of the machine and to reduce the amount of suction at the vacuum box. In the ordinary machine the wire has usually been arranged to move in a horizontal plane. In some machines means have been provided for adjusting the breast-roll end of the wire to different elevations to provide for dealing with different grades of stock, but the wire has never hitherto been so inclined as to cause the paper stock to travel at a speed, under the action of gravity, to equal or approximate the speed of the wire. In all previous methods of working, the wire has for a considerable portion of its length, starting from the breast-roll, drawn the stock along in consequence of the wire moving much faster than the stock, and the stock has waved, or rippled, badly near the breast-roll end of the wire. This has gradually diminished until an equilibrium has been established and an even surface obtained, but not until the waving or rippling has ceased at some considerable distance from the breast-roll have the fibres become laid uniformly, and the machines have therefore necessarily been run slowly to give ample time for the water to escape and for the fibres to lie down so as to make them a uniform sheet. In many cases the breast-roll has been raised 14 or 15 inches, and the stock rushes, as it were, downhill.

As, during the formation of the paper, the stock and the wire practically do not move relatively to each other, there is no drag of the stock upon the wire; consequently there is a more rapid and uniform drainage of the water from the stock, the full influence of the “shake” is made effective to secure uniformity in the distribution and interlocking of the fibres, and the regularity of the formation of the paper is not disturbed by waves or currents, which would otherwise be caused by pull of the wire upon the stock.

This ingenious device is now working successfully in many paper mills.

Machinery.—In setting out the plant necessary for a paper mill which is designed to produce a given quantity of finished paper, the manufacturer takes into consideration the class of paper to be made and the raw material to be employed. The following schedule has been prepared on such a basis:—

Plant and Machinery for High-class Printings.

Paper.

High-class printings made of wood pulp and esparto, used alone or blended in varying proportions as required. Quantity, 250 tons weekly.

Raw Material.

Esparto; chemical wood pulp.

Quantity: esparto, about 200 tons; wood pulp, 150 to 160.

China clay and usual chemicals.

In the estimation of materials required for the production of about 250 tons of paper, it is assumed that the 200 tons of esparto fibre will yield 90 tons bleached esparto fibre, and that the mechanical losses which take place during manufacture are counterbalanced by the weight of china clay added to the pulp. These conditions naturally vary in different mills, but such variations do not affect the schedule of machinery.

Unloading Sheds.

2 steam or electric cranes for handling fibre, clay, alum, bleach, rosin, coal, and finished paper.

1 3-ton weighbridge.

1 5-cwt. platform scales.

Steam Plant.

6 8-ft. by 30-ft. Lancashire boilers.

Fuel economiser.

Feed-water pump and tank.

Water softening apparatus.

1 500-h.-p. main steam engine, for fibre departments and beater floor.

Chemical Department.

Hoist for clay, alum, bleach, lime, &c.

4 causticising pans, 9 ft. diameter, 9 ft. deep.

2 storage tanks.

2 chalk sludge filter presses.

2 clay-mixing vats, 6 ft. diameter, 6 ft. deep.

1 starch mixer, 6 ft. diameter, 6 ft. deep.

1 size boiler, 8 ft. diameter, 8 ft. deep.

3 size storage tanks, 1,000 gallons each.

3 bleach-mixing vats.

3 bleach liquor settling tanks.

2 clear bleach liquor storage tanks.

1 alum dissolving tank.

Recovery Department:—

Soda.

1 multiple effect evaporating plant.

1 rotary furnace. 4,2]

4 lixiviating tanks, 2,000 gallons each.

2 storage tanks for clear liquor from lixiviating tanks, 20,000 gallons capacity.

Fibre.

2 tanks for receiving machine backwater.

2 Fullner's stuff catchers, or some other system of treating backwater.

2 filter presses.

Esparto Department.

1 esparto duster.

Travelling conveyer for cleaned esparto.

6 Sinclair vomiting boilers, each of 3 tons capacity.

2 measuring tanks for caustic liquor.

4 washing engines, 15 cwt. capacity.

6 Tower bleaching engines.

1 presse-pÂte.

10 galvanised iron trucks.

Wood Pulp Department.

4 pulp disintegrators and pumps.

4 Tower bleaching engines.

4 washing tanks or drainers.

6 galvanised iron trucks.

Beater Floor.

8 1,200-lbs. beating engines.

2 Marshall refiners.

6 galvanised iron trucks.

Paper Machine Room.

2 paper machines, 106 in. wide, with stuff chests, strainers, and engines complete.

1 paper machine, 120 in. wide, with stuff chests, strainers, and engines complete.

Patent dampers for each machine.

Calendering Room.

2 110-in. supercalenders. 4,2]

2 100-in. supercalenders.

2 6-reel cutters.

1 200-h.-p. main steam engine.

Finishing Room.

Sorting tables.

Packing press.

Weighing machine.

Repairs Department.

Usual repair outfit, such as lathes, planing machine, drilling tools, etc.

Blacksmith's shop outfit.

Carpenter's shop outfit.

Calender roll grinder.

Water Supply.

Main storage tank, 50,000 gallons capacity.

Water pumps.

Piping and connections to various departments.

Bell's patent filters (if necessary).