Home › G › Greiner Patent Cupola

Greiner Patent Cupola

This remarkable cupola is thus described by the patentee: "The novelty of the invention consists in a judicious admission of blast into the upper zones of a cupola, whereby the combustible gases are consumed within the cupola and the heat utilized to preheat the descending charges, thereby effecting a saving in the fuel necessary to melt the iron when it reaches the melting zone. In order to fully explain the principle of its workings, we will suppose a cupola of the ordinary design, with a single row of tuyeres or air inlets. The incoming air burns the coke in front of the tuyeres to carbonic-acid gas, a combination indicating perfect combustion. As this gas ascends through the incandescent coke above, most of it is converted into carbonic oxide by the absorption of an equivalent of carbon. The result of the combustion is, therefore, a gas mostly composed of carbonic oxide (CO), indicating an imperfect utilization of the fuel, as one pound of carbon burned to carbonic acid (CO2) will develop 14,500 heat-units; whereas the same amount of carbon burned to carbonic oxide (CO) will only develop 4480 heat-units, or less than one third of the heat developed by perfect combustion. "To avoid this loss of heat additional tuyeres have been placed at a short distance above the lower tuyeres to introduce air to consume the carbonic oxide (CO), but such arrangement does not have the desired effect, because the material at that place in the cupola has a very high temperature, consequently the entering air also ignites the coke, so that the action at the lower tuyeres is simply repeated, and carbonic oxide (CO) again formed at a short distance above."

This led Mr. Greiner to the following conclusions: "In every cupola there must be a point above which the descending materials have not yet reached the temperature necessary for the ignition of the solid fuel, while the ascending combustible gas is still warm enough to ignite when brought into contact with air. It is clear that air, if properly admitted above that point, will cause the combustion of the carbonic oxide (CO) without igniting the coke. "But if all the air necessary for the combustion of the carbonic oxide (CO) be admitted at one place or in one horizontal row of tuyeres, the heat developed will very soon raise the temperature so as to set fire to the coke, producing loss of carbon as before. Hence the upper blast must not be introduced on a horizontal plane, but through a number of small tuyeres, arranged (either in the form of a spiral or otherwise) so as to embrace the higher zones of the cupola, and must be regulated, both as to pressure and arrangement and dimensions of pipes, according to the capacity of each particular cupola. "The combustible gases are thus burned without heating the coke to incandescence, and the heat thus developed utilized to preheat the iron and the coke, so that they reach the melting zone at a higher temperature and require less heat to effect the melting." See CUPOLA; COMBUSTION. Grids is the name sometimes given to core-irons made similar to a grate of cast iron and used for sustaining bodies of sand which extend beyond the edge of a lifting-plate, etc., in green-sand work; also with and without prickers for dry-sand cores. In the former instance they may be made to serve a good purpose. By bolting or clamping the back edge to the lifting-plate the extending mould is as firmly held as if it rested on the plate itself. They also constitute a method of tying green-sand drawbacks, etc., far superior to tie-rods. See TIE-RODS; CORE-IRON; DRAWBACK.