480 THE COLLIERY GUARDIAN. March 9, 1917. In the case of cast iron tubbing, however, even with the best back-filling of concrete and grouting put in under wet conditions, there will still exist cavities con- taining water under pressure and having a corrosive action varying in degree, for which allowance must be made in the design of the tubbing, according to the life required of it. Underground Dams. High-pi essure cementation has been proved to possess great advantage in closing off underground feeders of water in connection with underground dams. In the first place, dams which have been constructed to meet unexpected inrushes of water have been put in with all possible speed, and sometimes there is not sufficient time to allow of the constructional work becoming properly matured and set before being subjected to water pressure. The consequence is a le tkage may occur through many places, and although such places may be very small in area, their very smallness does not allow of any further operation being carried out to close them under the older methods. In such cases high-pressure injection of cement would solve the difficulty, as it is possible to fill up such minute crevices in either brickwork or concrete. Some recent dams have been constructed upon the principle of forming what may be termed a tight plug at the site of the dam, by means, of the thorough cementation at high pressure of all rubble filling used in their construction, and also of all crevices and breaks in the sides, roof, or floor before any water pressure has to be met with. In such a way the constructional work can be thoroughly tested and be assumed to have a good factor of safety before any attempt is made to close off the water. Underground Fires In a manner similar to that in which it has been found possible to close up the finest of water-bearing fissures by means of the injection of a small percentage mixture of cement and water und^r high pressure, so it has been proved that air-leakage can be stopped through the cementation of brick walls or tbe lining of roadways, and the area affected can be satisfac orily sealed up. In n;any underground fires in roadways this leakage is the sole source of trouble and heat. Perhaps to a certain extent the temperature has been kept in hand with the aid of sand-filling, clay, or other materials; but it is usually found to be practically impossible to close off all leakage of air in this way, so that the situation is usually a permanent source of anxiety. If, however, a substantial lining is constructed and carried through such a fire area, this lining, even if it cannot be constructed absolutely airtight in the first instance, can nevertheles be made airtight by means of pressure injection. Among collieries in this country where this difficulty has been satisfactorily dealt with may be mentioned Griff, Exhall, and New digate collieries in the Warwick- shire coalfield, and a similar case now being dealt with in South Wales. Defective Boreholes. Sometimes boreholes in their progress to a required feeder of pure water have to pass through one or more beds containing inferior or corrosive water. After a time it may be found that the lining tubes in these boreholes become entirely corroded at the points in contact with the bad water, with the result that tbe borehole is useless. In such cases the upper feeders of bad water can be successfully closed off altogether by means of cementation, without the aid of any tubing, and the pure-water feeder again recovered. A similar case to the above has been already successfully dealt with in the Yorkshire coalfield in a comparatively short time. Defective Shaft-lining. Many old shafts in this country have been sunk and lined with ordinary brickwork through water-bearing measures, the water being originally collected as far as possible in water garlands. In course of time, however, the original waterways become choked up, the result being that wetness of the shaft gives rise to serious inconvenience. In other cases in course of time, through various reasons, water which has originally been closed off by means of tubbing is found to have broken through the ground below the tubbing crib, and shows itself in the brickwork below such tubbing. In the majority of these instances it is quite possible and practicable to close such water completely off and bring the shaft again to its original state of dryness. In addition to the above-mentioned conditions of wet walling, the writer would mention the case of broken segments in tubbing in which the broken tubbing-plates have been satisfactorily repaired. When the deforma- tion of the shaft is not serious, by careful application of cementation alone the replacement of defective plates has been rendered unnecessary and all leakage success- fully stopped. The great advantage is obvious, as if such plates had to be removed and replaced, the main feeders of water behind the tubbing would have to be dealt with during the progress of repairs. In dealing with the subject of cementation, the question of detailed comparative cost in connection with shaft-sinking has not been dwelt upon, on account of the variety of conditions which exist in different cases. Further information on this side of the question will no doubt be given in individual descriptions of some of the sinkings in future papers. It is somewhat difficult to give any generalised idea of comparative cost, as the main factors upon which the cost depends are those of the quantity of water expected, the total depth at which water will be encoun- tered, and the consequent rate of progress. When considerable quantities of water are met with at great depths, and the use of sinking pumps and tubbing is necessary, the advantage in cost to be obtained by adopting cementation is more apparent. BRIQUETTING BY THE DUTCH OIL PROCESS.* By W. P. Frey. The problem of briquetting coal, especially anthracite, involving as it does the utilisation of enormous quan- tities of fine material now wasted, has been the subject of long years of laboratory investigation and practical experiment. Owing chiefly to the difficulty in finding a cheap but efficient and non-objectionable binder, com- mercial success has been attained but recently. Within the past few years, however, vast strides have been made in both the technical and practical sides of the problem, and to-day the commercial briquette is actu- ally on the market, forming a potent addition to the fuel supply. ■ In general, the difficulties in briquetting concern the application and treatment of the binder selected and its relation to the material to be briquetted. The range of available briquetting material .is wide. Briquettes have been made from peat. The vast lignite deposits in the West should eventually lend themselves to the process. Bituminous coal briquettes are now being manufactured at several plants. Coke breeze is another material of interest. Each brings its own treatment problem, which can be solved only by serious study and experiment. As for the binder, it may be safely stated, after years of investigation with tar, pitch, “ sulphite pitch ” (waste liquor from paper mills), and a host of patented formulae and combinations ranging from complex organic pro- ducts to simple cement, that the most practical binder for all classes of fuel briquettes, from the standpoint of economy consistent with efficiency, is the heavy residue of petroleum (melting point about 160 degs. Fahr.) Paddle Mixer 16"Belt Press- Oil Car heating Shed ^Rotary {Screen /Z Screw Conveyor 'iZ "Screw Conveyor Mixer Building Fig. 1.—Cross Sections of Press and Mixer Buildings. 6- 16 Bell Conveyor \faddle fcr-' H I2.000-GALLON TANK u Z Handy Gate Valve ■G,Z Overflow I a ® I EL tofgddle Mixer I P* dive I -y Steam Pump Intake 0 5 10 15 20 25 OIL CAR HEATING SHED 1-----------1----1---L—1--------1 Fig. 2.—Arrangement of Oil Supply. known as hydrolene, used in connection with the Dutch oil process. This is controlled by the General Briquetting Company, of New York, and is in opera- tion at the works of the Lehigh Coal and Navigation Company at Lansford, Pennsylvania. The original plant was completed in 1909, and went into operation at. once, the product being manufactured with a tar pitch binder. It was rebuilt in 1911, and operated until the spring of 1915, using the same material. In the latter part of 1915 the process involving the use of the hydrolene oil installed by the Malcolmson Briquette Engineering Company and the General Briquetting Company was introduced. Subsequent operation has been based on this process. The entire operation naturally divides itself into four departments, each a distinct operation :—■ (1) The preparation of the raw fine fuel : (a) Drying, (5) screening, (c) cleaning. (2) The preliminary handling of the oil binder. (3) The mixing and in ter-compounding of the coal, dust, and' oil : (a) Paddle mixer, preliminary mixing; (6) edge runner, combination grinding, and inter-com- pounding. (4) The pressing of the coal and oil flux into briquettes : (a) Final fluxing, (b) feeding, (c) pressing, (d) final cleaning, ie) loading. Preparing the Coal. The fine coal, or silt, is first cleaned at the breaker by a combination of jigging and washing. It is then despatched to the briquetting plant in cars. The wet silt is dumped into a track hopper, and conveyed to the dryer drums. These dryers are of the rotary single- shell type, made by the Vulcan Iron Works, of Wilkes- Barre, Pennsylvania. The fuel is No. 3' buckwheat coal, or an approximate equivalent. The temperature at the end of the drum varies from 350 to 500 degs. Fahr., according to conditions. The fuel consumption varies according to the size and moisture of raw material from 5 to 20 tons per 100 tons dried. From the dryer the fine coal is conveyed to the screens and sized in preparation for the final cleaning * Coal Age. process. The material contains 1 to 2 per cent, of moisture—the maximum allowable for this stage of the process. The screens divide the fuel into four different sizes, to which the air separators are adjusted. The ensuing cleaning, or separation, is performed by a set of four Damon air separators. It is possible to reduce the impurities by 10 per cent, with this equip- ment, but the best practice, from the point of view of economy, is to extract about 6 per cent. There are times when even with an extraction as low as 6 per cent., 45 per cent, combustible matter is left in the waste. When the adjustment is made for a 10 per cent, extraction, 65 per cent, of good coal may be carried into the waste. This is too much from the standpoint of efficiency. For reasons of economy, and because of the dust nuisance, it is now the tendency to eliminate the dry air separation, and to depend entirely upon the wet process for cleaning employed at the breaker. Although the dry air process is still in use, a by-pass has been installed whereby the operation of the whole separator plant may be omitted. However, too much stress cannot be laid upon the importance of the preparation of raw material. Many failures in briquetting can be traced to lack of attention to this detail. At the plant of tbe Lehigh Coal and Navigation Company so much importance is attached to the silt preparation that every car of raw material and of finished briquettes is sub- jected to careful sampling and chemical analysis. The briquettes are not supposed to run above 16 per cent, in ash. The Oil Used. The hydrolene oil (Sun Company, of Philadelphia) is a black material which melts between 160 and 170 degs. Fahr. This is delivered in tank cars of about 30 tons capacity. As the material is solid at ordinary tempera- tures, the first process, after the car is received in the shed, is the heating of the oil in the car by means of steam. When the oil has been liquefied, it is delivered through the steam-jacketed pipe, seen in fig. 2. A Kinney rotating plunger pump, type SD, is located in this line. This has worked with entirely satisfactory results. By alternating at will the valves B and C in the pipe line, the oil can be drawn either from the car pipe or the 12,000gals, storage tank H. The oil, just before pass- ing through the pump, encounters a steam-jacketed strainer, which eliminates any possible foreign matter. From here the oil passes up the steam-jacketed pipe- line D to the feeder tank E. As the oil used is a mixture of complex hydrocarbons of varying viscosity, there is a constant tendency toward the separation of a portion of the oil' and consequent clogging. Constant agitation is the best preventive of this evil. It is therefore advisable to keep the feeder tank E practically full at all times. To take care of the overflow, a pipe line is run to the storage tank H. This tank has a capacity of 12,000 gals., which is ample to take care of any surplus. From the feeder tank E, the pipe-line F takes the oil to the paddle mixer, which forms the beginning of the next step in the process. Mixing. This third step in the briquetting is really the most delicate stage of the whole process. Upon, the proper proportioning and compounding of the two elements involved final success depends. And in this propor- tioning and compounding are involved many delicate adjustments, each installation having features peculiar to itself. It may therefore be said that no definite hard and fast rules can be laid down. It is necessary, in all new lay-outs, to study and experiment with the arrange-, ment of each stage of the process before the proper and ideal method can be reached. The apparatus in which the coal and oil meet is known as the “ paddle mixer.” In the Lansford plant it is a horizontal steel trough, about 35 ft. long and 21 in. wide. A 3| in. square shaft revolves in the centre, carrying