WATER GAS
It should be emphasized that the above figures were obtained under conditions of constant steam flow. That is to say, the flow of steam was the same during each minute of the 6-minute period, an unscientific practice which. is allowed to prevail on the majority of water-gas plants. One of the main causes of poor quality gas is the fact that steam is usually permitted to pass through the fuel-bed in unrestricted quantities, without any thought as to the theoretical amount which. is reqttired. The introduction of steam-flow meters has done a good deal towards remedying the trouble; but the difficulty with a -water-gas plant lies in the faet that, from the beginning of the gasmaking “ run ” onwards, a gradual cooling of the fuel-bed is taking place, so that its capacity to decompose steam is far less in the later periods than in the earlier minutes of the “run.” In the past, little attention has been given to the fact that as the steam valve is full-open during the whole period, the supply of steam remains constant in spite of the gradual decrease in the temperature of the fuel. It is, accordmgly, towards the end of the gasmaking period that inerts begin to make their appearance in large quantities, while in addition a considerable amount of fuel is wasted in providing excess steam from which no gas is obtained.
AUTOMATIC CONTROL OF STEAM
Fig. 445 illustrates an automatic governor 1 which is designer! to reduce, without any attention from the operator, the flow of steam in accordance with the gradual reduction in temperature of the fuel-bed. In the main steam supply pipe to the
Fig. 445.—-Automatic Steam Controlleb.
1 The author’s patent, ' 16311/19.