446 MODERN GASWORKS PRACTICE
densers shown in Fig. 274 are capable of dealing with. about four million cubic feet of gas per diem. The cold water enters the condenser near the point of exit of the cooled gas and flows up one vessel and down the other in a direction opposite to that of the gas, the outlet for the water being near the inlet for crude gas. By varying the amount of circulating water a more uniform condensation is obtained under the varying conditions of the atmosphere tlian is possible in the ordinary air condenser. The tubes are 3 inches diameter inside and 40 feet long, expanded into the top and bottom tube plates.
For the purpose of eliminating a large portion of the naph thaien e and for the prevention of deposits in the tubes, tar-spraying devices are fitted on the top of every tube, as shown in the enlarged detail. This consists of a tar-distributing box at top, with scaled nozzles provided with “ spreaders ” or crown Castings for distri-
Fis. 275.—Connections for Cakpentbb’s Condenser.
buting a tliin film of light tar down the inside surfaces of the gas tubes, the warm tar being pumped into the upper box for this purpose. The gas on. ascending or descend-ing slowly through the tubes is washed by this means, and any deposition of naphtha-lene flows away along with. the Condensed tar and liquor into a receptacle provided for it in the lower portion of the vessel. A steam-jacketed seal pipe and a run-off pipe are provided as shown. The lieated water, after passing through the condensers, is usually circulated through separate air-cooling towers and used continuously over and over again. In most cases tar spraying is not carried on continuously, but for short intermittent periods throughout the day.
The condensers are usually arranged in batteries of any number up to twelve, and are connected up so as to be reversible, as shown in Fig. 275. It will be seen that any possibility of error in operating the valves is guarded against by coupling up the latter by means of gearing. The water valves are arranged in precisely the same männer as those for the gas.