Regenerative heat exchanger

A hot blast stove is a regenerator with fixed mass storage. It is used to provide the hot blast for the blast furnace process. With the use of blast furnace gas heat for air preheating a significant fuel saving is achieved.

Cowper

The blast stoves mostly used are named after the inventor and developer of regenerative heat exchange Edward Alfred Cowper. Cowper working with a temporal change ( heating - cooling ). They consist of cylinders with a height of about 50 m with a diameter of 10 m. These containers are made of a combustion chamber and a storage chamber, which is lined with refractory bricks. The top gas is concentrated and combusted, which led thereby dissipated and resulting hot exhaust of the storage blocks in the combustion chamber with gas. The stones are heated and passed when the hot blast stove is switched to fresh air, this heat again. The thus heated air is called the hot blast, which is then passed at a temperature of about 1300 ° C in the rest of the furnace. The preparation of some pig iron as ferromanganese and ferrosilicon have only become possible with the hot wind technology.

By far the largest and most important part of the Cowper take the trim stones, the latticework, a. This lattice forms the storage mass for heat and is constructed of refractory bricks. The thicker these conglomerates are formed, the longer the heating phase must be selected and the more heat can be stored.

In addition to this grid slot is the much smaller focal shaft in which, for example, blast furnace gas burns and produces a hot combustion gas. This flows from the top through the latticework down and gives it its heat to the storage mass from. After changing air flows, called at the cottage industry " Wind ", by the lattice from bottom to top and is heated to high temperatures, which is blown as a " hot wind " in the blast furnace. When blown into the furnace as constant as possible the hot blast temperature of about 1200 ° C is necessary. For this to be ensured at an ever- cooling hot-blast stoves, a mixed wind is generated by the addition of unheated outside air. Here, a time- constant part decreasing outdoor air is passed through a bypass on the hot blast stoves, and is mixed with the hot wind. Thus reached a controllable and almost temperature- constant wind flow to the blast furnace. At the end of each wind period of hot wind from the hot blast stoves, without admixture of outside air should still satisfy the required temperatures.

Types of regenerators

There are Cowper with internal and external lying burning shaft. In one design, the burning shaft is located in the interior of the lattice, while the other design of these is outside and mounted separately. The hot blast stove with an external burning shaft can be seen clearly on its two cylindrical buildings that rise to almost 50 meters into the air.

The alternative design is the integration of the combustion shaft into the shell of the hot stove to an internal combustion chamber. The advantage of an internal combustion shaft is reduced, the heat dissipation the surroundings. But is offset by a more difficult maintenance of the built- burning shaft. As a major disadvantage of the internal combustion shaft is a common cracking in masonry between the combustion chamber and latticework mentioned. This " short circuits" occur mainly at the bottom of the dividing wall, because in this region of the internal shaft side, the highest temperatures are reached during the heating. On the other hand, the wall in the wind phase is most cooled to the lattice site. These thermal stresses can lead to cracking, which disturb the Cowperbetrieb sensitive.

Also, because in the course of time the requirements for very high wind temperatures were more important has been reinforced have been transferred to the design of an external combustion shaft. This construction has the advantage that the grid slot significantly more trim pieces can be accommodated, the heating surface thus becomes larger and as the wind power can be increased again.