Galois structure of K-Groups of rings of integers

Molten slag from a furnace, particularly that produced by the combustion of solid fuel, is cooled to a solid from by discharging the slag so as to form a layer and maintaining the layer in a cooling liquid the surface of which is below the upper surface of the molten layer until this layer has solidified. Fig. 1 shows a suitable apparatus. The molten material leaving the furnace flows through secondary combustion chamber 11, is discharged through slag outlet 10 in a uniform stream and is directed through enclosure 12 into tank 13. This tank is full of water, the level of which is maintained substantially constant by means of a valved water inlet connection 18 and an adjustable overflow gate 20, and it also contains a pan-type conveyer 21 disposed as shown with the molten ash receiving surface 22 of the upper run of the conveyer situated immediately, e.g. approximately half an inch, below the water level 23. The slag falls on to 21 and is then transported horizontally through the water into an extension 32 of the tank 13 where the conveyer rises gradually so that the now solidified slag comes out of the water and is discharged into container 35. At this point, the slabs of solidified slag are broken by pneumatic or hydraulic hammer 37 into smaller pieces that are discharged by conveyer 36 through a sealing-feeding device 65 for delivery to an associated crusher (not shown). In another embodiment (Fig. 3, not shown) the slag as it comes off the first conveyer is discharged through a shoot into a rotary breaker which further reduces the size of the slag pieces and is also perforated to allow pieces of selected size to fall on to a shaking grate. On here the slag is submitted to further cooling by passing air from an inlet through the grate and thence through the rotary breaker by which means the air used is preheated, and after cleaning via dust separators is discharged through a duct for use in the combustion process. The slag pieces from the surface of the grate and the fines which fall through to a conveyer situated beneath the grate are discharged on to a further conveyer for disposal. If the amount of slag issuing from the furnace is too great for the primary conveying system, it overflows and is granulated in the initial tank from which it can be removed. Specification 552,747 is referred to.