Modern Gasworks Practice

110 MODERN GASWORKS PRACTICE system was never experimented with on anything approaching a large scale, and to-day it is merely of historical interest. West and Wild System J. West and his collaborator have attempted to solve the mechanical diffi-culties of tlie contimious method. while at the same time providing a high, gas yield and a coke of goocl quality. They have found by investigation and experiment that in order to obtain satisfactory results it is necessary that the retorts should be main-tained practically fully charged at the miet end throughout normal working, that they should be of flattened cross section, approaching that employed in coke-oven construction, and that they should be tapered towards their outlet end. At the same time it has been found that the coal, immediately it enters the hot zone of the retort, must be submitted to a very high temperature in Order that the outer portion or envelope of the charge may be carbomzed extremely rapidly and taken through, the “ tacky ” condition as quickly as possible. In this männer a carbonized envelope is produced around the charge, which facilitates its passage, with the avoidance of ■coagulation or cohesion from end to end. At the inlet end of each retort is attached a chamber in which a plunger is actuatecl by hydraulic power. Each chamber receives its supply of coal from an overhead storage pouch, and is fitted witli a special valve to prevent the escape of gas. When the piston is withdrawn to its extreme outward position coal falls into the space in front of it, and as the piston travels slowly forward the coal is forced. into the retort. West has found that by ensuring that the fresh coal charge is bronght up against the previous charge before the latter is sufficiently carbonized to prevent eohesion of the old and new charges, the plunger is enabled to force the whole mass of material in the retort towards the discharging end, and to effect simultaneous charging and discharging without the material wedging itself up. At the outlet end of each retort was originally attached a downwardly extending chamber very similar to those employed in the Glover-West vertical installations, and this formet! a storage vessel through which the coke was discharged by gravity at intp.rmittp.nt periods through a hermetically sealed door of the usual construction. In the most ■common practice the horizontal retort is provided with a gas take-off at either end, but in the new system the gas travels along the retort and is removecl by an ascension pipe fixed at the top of the coke chamber. The introduction of the vertical retort, which lends itself to the delicate control ■of temperatures, has been responsible for the idea of establishing zones of diffo-ring temperatures, a practice which is always to be condemned in the ordinary intermittent systems of carbonization. Uniformity of temperature, however, is no longer an essential feature when a continually moving charge is under consideration, and so it is not surprising to find that West arranges in his new system for three zones of different degrees of temperature throughout the retorts. In the first zone, which extends along the inlet length of the retort, the most intense heating is arranged for by bringing about combustion of the producer gas at this point. Then follows a length of intermediate temperature, heated by circulation of the hot products of