The brine, as it requires to be concentrated, is run into the pan from the battery tank. Live steam is admitted into the jacket and the brine in the copper boils, the excess water being driven off as steam. After the brine has been concentrated sufficiently and has cooled down, it is drained off to the brine pump and reabsorbed into the system. In large plants where a considerable amount of moisture is absorbed by the brine as the air passes over the battery, the brine has to be frequently concentrated. In this case the method shown in fig. 761 is used. In the diagram, A is a steam-jacketed copper pan similar to that just described; B is a tank which contains the hot brine just concentrated, and D is a warm brine tank. When the apparatus is at work, a charge of cold brine is put into A and concentrated to the proper density; it is then discharged hot into B. Cold brine requiring to be concentrated flows from the battery tank through the pipe C and through the coils in B into the tank D. In passing through the coils it is warmed by the hot brine in the tank, and when it enters D is already hot. The concentrated brine is correspondingly cooled. The coil in the tank D thus becomes a heat interchanger and saves fuel by warming up the cold brine. This interchanger may be of the open-air type, and if this is adopted, the hot brine is further cooled by the action of the atmosphere. The cooler is usually just below the level of the battery tank, and the brine is gravitated through the coil in B into the tank D, the supply being regulated by the valve shown. In this case it has, of course, to be returned to the tank by a pump. When the concentrator is not in continuous use the tank D may be omitted. In practice the copper A is fitted with a bonnet to catch and carry off the steam. 1 Messrs the Haslam Foundry and Engineering Company, Ltd., Derby. CHAPTER X. DISTILLED WATER. Introductory. It is only in recent years that ice, in this country, has been used to any extent for table purposes, and, the demand being small, the imported clear natural ice has been sufficient to supply all wants. Ice drawn from the deep Norwegian or Canadian lakes is probably as pure as natural ice can be, but, unfortunately, as the demand has increased, ice has been placed on the market, both here and in the United States, which has been harvested from less commendable sources. As a result, inquiries have been made and a demand has sprung up for hygienic ice, or, in other words, artificial ice made from pure distilled water. It is due to the fact that this demand can be readily and economically met that a great impetus has recently been given to the establishment of ice factories. The early manufacturers of ice were quite content to turn out an article which was cold, and nothing else. No special care was taken to make the ice either pure or clear, and the cans were filled direct from the public water supply, or with water pumped from a well sunk on the premises. Given a pure water supply, it is quite possible to make marketable ice direct from the water by agitating it during freezing, so as to expel the air, and there have been many inventions for this purpose. They are, however, very nearly all open to some objection or other, the majority being cumbersome in themselves, unreliable in their performance, and very much in the way when the cans have to be taken out of the tanks. Many of them also have to be carefully watched to prevent their being frozen in. Clear ice can be made from ordinary water by means of the plate system, and more or less clear ice by means of the cell system. With this latter it is found that the lower the temperature, the more cloudy the ice, and vice versâ, and both systems are open to objection on account of the length of time that the blocks take to freeze, and consequently the size of the plant which is necessary for a given output. All the troubles relative to these systems can be avoided by distilling and de-aërating the water before it is put into the freezing-cans. This process has met with great success, and its objects may be summarized as follows: 1. The de-aëration of the water. 3. The making, with absolute safety from contamina- saving the expense of buying the water from the public supply. There is no doubt that the public prefer clear ice to semi-opaque ice, and that they will be willing to pay a higher price for it; also there is a commercial value attached to the expression "Ice made from pure distilled water," as signifying freedom from pathogenic bacteria. The distilling plants used in ice factories may be divided into two large classes: 1. Those using the exhaust steam from the engines, and 2. Those using live steam in multiple effect evapo rators. Exhaust Steam Distilling Plant. The distilling plant which is most commonly used in ice factories is shown diagrammatically in fig. 77. In this arrangement the distilled water is obtained by condensing and purifying the exhaust steam from the engines, live steam being added to make up any deficiency. In the diagram, the exhaust steam from the refrigerating engines and other machinery comes up the pipe A, which is fitted with an automatic relief valve, loaded so as to give the steam a back pressure of about 5 lbs. on the square inch, and also for use in case it is necessary for any reason to exhaust direct to the atmosphere. When the distilling apparatus is in use this valve is closed, and the exhaust steam is passed through the steam-scrubber B, where it is robbed of its grosser impurities, such as lubricating oil, etc., and enters the feed-heater C, which may be of some well-known type, such as the Berryman. From this it passes into the surface condenser D. As there is no vacuum, no air-pump is required. The condensing water is the waste from the condensers of the refrigerating agent. As soon as the steam is condensed it runs off into the reboiler E, where it is violently reboiled by a steam-coil. Any air it may have absorbed is driven off, and the grease which has been passed by the steam-scrubber, and other solid matter, rises to the surface and is skimmed off through the pipe E. Preferably the skimmer should be |