Modern Gasworks Practice

CHAPTER IV THE CONTROL OF HORIZONTAL RETORT SETTINGS The problem of the starting-up, working, and regulation of retort-bench producers is one with which the gas engineer is continually face to face ; and there are few more trying ordeals than that of warming-up to present-day heats, and afterwards main-taining such heats with regularity. First, it has to be realized that in the case of new work, or settings which have previously been in use, but have been let down, the range of temperature through which they have to be raised is as much as 1,300° C., when considering the retorts, and about 400° C. higher as far as the combustion chamber and its immediate surroundings are concerned. Hence, if damage is to be avoided, more than ordinary care must be given to the procedure known as “ slow fires.” Rapid temperature rises are the sure forerunners of cracks and opening joints, whilst particular attention is essential with many of the modern forms of regenerators designed on elaborate lines for bringing about an interchange of heat between the waste gases and secondary air. STARTING-UP RETORT SETTINGS The working life of a retort bench depends in no small degree upon the manner in which it is dried out and brought up to working temperature. No hard and fast rules as to the length of time which is required for the operation can be laid down, as so much depends upon whether the brickwork of the setting is entirely new or whether it has only been. relaid in parts. As regards the time required for bringing new work into operation, a series of typical conditions are discussed below1:— (1) Entirp. new bench, including new regenerators, furnace, main arch, etc. Time for clrying—at least four weeks, the fire being gradually increased in size after the first week. After this period another six days should be taken to bring the bench up to working heats. (2) Bench reconstructed from furnace-arch level, new main arch. Time for clrying—at least three weeks. Six days to bring up to working heats. When the main arches are new it will be found advisable to leave two or three pockets re.a.ching down from the top of the spandril to the crown of the arch. These pockets will then provide an outlet for all the moisture issuing from the spandril brickwork, and they will prevent cracks occurrmg in the arch rings and in the brickwork above. The pockets may be filled up when working heats have been attained. 1 Attention may be drawn to the recsnt practice of the South Metropolitan Gas Company, who have found no ill-effects in pioking up working heats in 36 hours. 125