;g -c> :o ■s ;S * (Q U1 § Q * Q U I u s: w , O ? h * W (14 P □2 £ O H P 3 S * § ®e---- fct£ y— w nr-nn M |i H II Hi p N iir\ □jfvt I1 xE^vJk tei r , _ ^raSE0 I ft! I a ■ THE COLLIERY GUARDIAN. to the waste liquor valve in the ordinary manner. This lime chamber further acts as a reservoir for the lime sludge, and is provided with doors, so that it can be easily cleaned out. The liming apparatus consists of a rectangular wrought iron tank, which is divided into two compart- ments, so that the actual milk of lime will overflow from the one to the other and feed the pumps, whilst the sludge will remain in the first compartment. The lime is placed in the wire baskets, and slacked with the spent liquor from the still; from the tank it runs by gravitation to the pumps, whence it is forced at boil- ing temperature to the mixer. The lime pump is extremely simple. The milk of lime, in filling the pump body, causes a steel float to rise, which works an automatic valve. When the pump is full, this valve shuts off the supply and admits steam, which forces the contents to the mixer; the float in falling, shuts off the steam, and re-opens the supply, whereupon the operation is repeated. The pump can be adjusted to any required rate, the whole operation being automatic, and requiring practically no attention. The saturators are of the closed type, and are made in all sizes for makes of two tons up to 25 tons per day. They are constructed throughout of solid plate chemical lead, encased in stout pitch pine laggings, and designed to supersede the old method of hand fishing, the sul- phate being discharged, as made, by means of a lead ejector and deposited on the drainer. Lead catch boxes and baffle boxes are provided to prevent any acid or sulphate escaping. These stand on a timber platform, supported by means of angle irons carried from the base of the saturator. The saturators stand on wooden trays covered with . chemical lead, which in turn stand on brick wells, act- ing as a foundation and also as a reservoir for the mother liquor, which can be returned to the saturators by means of a steam injector. The centrifugal drying machines, driven by a steam engine or electric motor, are constructed with a self- contained cast iron frame and solid spindle, with basket made in stout copper sheets, with inner copper lining. The basket revolves in an outer monitor or safety case of solid plate chemical lead, encased in a stout pitch pine lagging strongly bound with wrought iron bands, etc., provision being made for the mother liquor to return to the mother liquor pot. This machine should be erected on a platform or working stage covered with lead sheets, on which loose floor boards are laid. The salt, after treatment in the centrifugal machine, is dropped through the centre dis- charge cyalve of the copper basket directly on to the elevator conveyor, and delivered to the stores without any handling. Fig. 2 illustrates plant for carrying on Wilton’s direct process in small works, where the capital expenditure on the installation of a sulphate of ammonia plant on the ordinary type would not in most cases be justified in view of the small quantity produced. Coal is carbonised in the retort house in the usual manner. The gas drawn away by the exhauster is cooled for the removal of tar and virgin liquor. A com- bined condenser and tar extractor is installed, if required, which may be placed in a convenient position. In the ordinary process of purification, the gas would next pass through water washers or scrubbers, but in the direct recovery system these are thrown out of action, and the gas passes instead through an acid washer filled with weak sulphuric acid, which absorbs all the ammonia, forming concentrated sulphate of ammonia liquor. The gas leaving the washer goes on to the ordinary oxide purifiers, and into the holders. The virgin or hydraulic main liquor is treated with lime, and the ammonia gas passes into the acid washer, and is recovered in the same manner. In this way all the ammonia is converted into sulphate liquor, and as the latter accumulates it is pumped by air pressure into a feed tank, and evaporated down to salt in an open pan, the salt being fished out, drained, and dried by the waste heat, thus rendering a lead- lined store unnecessary. It has been found that sulphate is produced with the same amount of steam that was formerly necessary for working the rotary washers, and without any additional labour. One of the advantages of the system is the greatly reduced effluent, as there are only about 10 gals, per ton of coal per day. A semi-direct sulphate of ammonia plant is also made, in which the gas is first washed with sulphuric acid for the recovery of the ammonia, as on a direct plant, but the resultant mother liquor is pumped to a saturator, it is worked up into sulphate of ammonia in the manner with the ammonia recovered from the liquor. _____________________________ where usual virgin Grimsby Coal Exports.—During the week ended March 24 the coal exported from Grimsby consisted of 615 toms to Treport. During the corresponding week of last year the total was 10,904 tons foreign. Organisation of Science.—Delegates from the Institution of Mining Engineers, Institution of Mechanical Engineers, Institution of Electrical Engineers, Institution of Civil Engineers, Institution of Chemistry, Society of Chemical Industry, British Association, Chemical Society, Geological Society, and many other bodies attended a conference con- vened by the Royal Society last week with reference to organising scientific effort in this country. A committee was appointed to draft a scheme for establishing a conjoint board of scientific societies for the purpose of : (1) Promoting the co-operation of those interested in pure or applied science; (2) supplying a means by which the scientific opinion of the country may, on matters relating to science, industry, and education, find effective expression.; (3) taking such action as may be necessary to promote the application of science to our industries and to the service of the nation ; (4) discussing scientific questions in which international co-operation seems advisable. A a u z a o Q. < tr O Q O < 6 a u a t/> m Z I UJ