GB2127948A - Hot blast stove - Google Patents

Abstract

A hot blast stove or air heater, in particular for blast furnaces, comprises a chamber (3) having a refractory lining (not shown), a first sheet metal shell (1) and outside the first shell (1) a second outer sheet metal shell (5) made up of welded sections. The shells (1, 5) are separated by spacers arranged flanking the welded joints and the gap (6) between the shells and between the spacers is filled with an acid-proof cast material (22) which covers the weld seams, and a free flowing dry material (23) fills the gap (6) elsewhere. In order to avoid excessive pressure in the space (6) in the double shell and to prevent condensate attacking the outer sheet metal shell (5), the space (6) between the two sheet metal shells is connected via a piping system (24) to the space below the grid chamber (2). The cast material is based on an epoxy resin with quartz addition. <IMAGE>

Description

SPECIFICATION Hot blast stove The invention relates to hot blast stoves, particularly for blast furnaces.

Such hot blast stoves may have a refractory lining and a sheet metal casing which is welded together for example from sheet metal sections and is constructed at least in part as a hollow double shell. The double shell may be formed by arranging a second outer sheet metal shell around a first inner sheet metal shell enclosing the refractory lining and filling the space between the two sheet metal shells with a free-running dry material. The inner surface of the outer sheet metal shell optionally has an acid-proof coating based on epoxy resin and the ridges of welded joints of the outer sheet metal shell may be covered by an acid-proof cast material based on an epoxy resin with a quartz addition which is provided in the space between the two sheet metal shells.Spacers may be provided in the space between the two sheet metal shells optionally flanking the vertical welded joints of the outer sheet metal shell and the cast material is provided between the spacers, such a construction is shown in the present Applicant's Patent No. (Patent Application No.

) (Our Case 3226), whose entire content is incorporated herein by reference.

In the co-pending application of the present applicants which is referred to above and which relates to a hot blast stove renovated by means of a double shell with the space filled, it is possible in the case of undamaged old sheet metal shells for excess pressure to build up in the space in the double shell at least partially as a result of decomposition of the synthetic filling at high temperatures, the increased temperatures being caused by defective old brickwork.

It is an object of the present invention to develop a hot blast stove of the type proposed in such a way that excessive pressures do not build up in the space in the double shell of the hot blast stove, while at the same time avoiding attack on the new sheet metal shell by any condensation.

According to the present invention, there is provided a hot blast stove having a refractory lining and a first sheet metal shell outside the lining, and outside the first shell, at least over part of its extent, a second outer sheet metal shell forming a hollow double shell enclosing the refractory lining, the two shells being separated by spacers, the space between the two sheet metal shells being occupied by a free-running dry material and on the inside ridges of welded joints of the outer shell by an acid-proof cast material based on an epoxy resin with quartz addition, the space between the two sheet metal shells being connected via a piping system to the space below the grid chamber.

In this way an excess pressure caused by synthetic material decomposing at high temperatures and endangering the inner sheet metal casing cannot build up. The connection of the space between the two sheet metal shells to the space below the grid chamber means that the pressure in the space between the sheet metal shells is always greater than the pressure in the combustion chamber by the hot blast stove pressure loss (approximately 500 to 700 mm WS) on the blast side. As a result no damaging condensate can enter the space between the two shells even if fractures subsequently occur in a section of the sheet metal casing. The pressure equalisation system means that even in normal operation a synchronised pressure build-up in the space between the two shells and the interior of the hot blast stove is ensured during the discharge phase.During the relatively short discharge operation (approximately 100 seconds) of the hot blast stove the blast pressure can easily escape from the space in the double casing so that an old inner sheet metal shell need not be strained by external pressure.

Preferably, the spacers are arranged flanking the vertical welded joints of the outer sheet metal casing and the cast material is provided between the spacers to define individual casing chambers between the two shells and the piping system connects the individual casing chambers to each other and to the space below the grid chamber.

With such a construction it is not possible for a pressure build-up in the individual chambers to occur due to the pressure equalisation of the double shell chambers relative to each other. The reduction in pressure always occurs in a short interval of time in the interior of the hot blast stove. If the old inner sheet metal shell has leaks, the entry of corrosive substances into the space in the double casing is prevented.

Preferably, in order to prevent dust particles from the dry filling in the space between the shells from being blown out in the course of the discharge operations, the piping system opens into the space between the two sheet metal casings via nozzle-like tap pipes. By means of a suitable nozzle shape combined with suitable positioning of the tap pipes, the rate of flow out of the space between the shells can be effectively controlled.

The invention may be carried into practice in various ways and one embodiment will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a partial vertical section through a hot blast stove with the refractory lining removed for clarity; Figure 2 is the portion within the chain line section A of Fig. 1, to a greater scale and reduced length; Figure 3 is a partial horizontal cross-section through the double shell at a vertical welding seam of the outer shell; Figure 4 is a schematic side view of a hot blast stove having a double shell; Figure 5 is a section through the double shell (broken away) in the region of a nozzlelike tap pipe of the piping system; and Figure 6 is a schematic plan view of the combustion chamber and the grid chamber (partially broken away) with the piping system.

In the hot blast stove shown a sheet metal shell 1 surrounds a grid chamber of checker brick shaft 2, a combustion chamber 3 and a cupola 4 which connects the two chambers of the hot blast stove with an exterior combustion chamber. The refractory lining enclosed by the sheet metal shell 1 is not shown for the sake of clarity.

The sheet metal shell 1, which is composed of shell sections in a known manner, has a second outer shell 5 in the region of the combustion chamber 3, into which flames extend during the heating phase of the grid structure located in the grid chamber 2, so that a double shell 1, 5 is formed with a gap 6 between them. The outer shell 5 like the inner shell 1, is made up of shell sections 5a to 5e resting on top of one another, and each of these sections comprises two half annular sections 7 and 8 (Fig. 3). All the joints between the sections are connected by welding the seams 9 and 10 after placing welding strips 11 behind them. U-section shaped spacers 1 2 are secured to the inner shell 1 and extend vertically on either side of the vertical welding seams 9, thus defining the gap 6.

The U-shaped profile is filled with a setting elastic mass 1 3.

At its lower end, the outer shell 5 is sup ported by means of a horizontal welding seam 25 on a base ring 14 which in turn is firmly welded to the inner shell 1 and to an annular flange 1 5 attached to the shell 1. A corresponding top ring 16, also welded to an annular flange 1 7 and to the shell 1 holds the upper end of the outer shell 5 by means of a further horizontal welding seam 18.

The upper part of the outer shell 5 has filling pipes 20 which are closable by means of caps 1 9 and there are also pressure vents 21 extending into the gap 6 at its highest point in the region into which the filling pipes 20 extend. Both the filling pipes 20 and the pressure vents 21 are uniformly distributed over the periphery of the shell 5.

The gap 6 between the shells 1 and 5 has two types of filling, one castable, chemically setting and acid resistant material 22 (which has the same composition as the elastic mass 13) and one free-running dry material 23. The cast material 22 comprises 110/o epoxy resin, 13% special tar with hardener and 76% quartz and in which the grain size proportions of the quartz are 38% wt. of O to 1 mm and 38% by wt. of over 1 mum as spherical grains.

The dry material comprises 80% by wt.

SiC/graphite, 5% by wt. MgO and 15% by wt. BaSO4. The acid resistant cast material 22 is located along the welded seams 9 and 10 whitst the dry material 22 fills the intermediate spaces.

The back-filling of the two materials 22 and 23 occurs sequentially. After locating the first shell section 5a, a base layer 24 of cast material 22 is laid in position, leaving the spaces between the spacers 12 including the welding seams free. When this has set, dry material 23 is filled on the base layer 24, using vibrators up to about 150mm below the upper edge of the section 5a in the spaces which do not include welding seams. Thereafter, the vertical welding seam spaces between the spacers 12 are filled with cast material 22 up to the height of the section.

Subsequently, the mounting of the second section Sb is carried out and the space 6 is filled with cast material 22 up to about 150mm above the horizontal welding seam 10 which connects the sections 5a and 5b.

As soon as this has set, the back-filling process is repeated in accordance with the scheme described above.

The last section 5e, which is mounted without any spacers 12 in the space 6, is filled only with cast material 22. This is poured in through the filling pipes 20 and is continued until material begins to leave through the pressure vents 21.

Fig. 4 shows a hot blast stove in side view with a checker brick shaft or grid chamber 2 and a combustion chamber 3 which are enclosed by an old or existing sheet metal shell 1 (in need of renovation). The grid chamber 2 and the combustion chamber 3 of the hot blast stove are connected to each other by a cupola 4.

As shown in Fig. 5 the inner sheet metal shell 1 is enclosed by a new outer sheet metal shell 5 leaving a space 6 and the space 6 is filled with a combination of a free-running dry material and an acid-proof cast material, as is described in greater detail in relation to Figs.

1 to 3 and in the abovementioned co-pending patent application No. (our case 3226).

The individual double casing chambers 25 of the space 6 between the sections of cast material are connected via a piping system 24 to the space below the grid chamber 2 as shown in Figs. 4 and 6. As is shown particu larly in Fig. 2, the piping system 24 opens via noule-like tap pipes 26 into the space 6 in the double shell.

Claims (3)

1. A hot blast stove having a refractory lining and a first sheet metal shell outside the lining, and outside the first shell, at least over part of its extent, a second outer sheet metal shell forming a hollow double shell enclosing the refractory lining the two shells being separated by spacers, the space between the two sheet metal shells being occupied by a freerunning dry material and on the inside ridges of welded joints of the outer shell by an acidproof cast material based on an epoxy resin with quartz addition, the space between the two sheet metal shells being connected via a piping system to the space below the grid chamber.

2. A hot blast stove as claimed in Claim 1 in which the spacers are arranged flanking the vertical welded joints of the outer sheet metal casing and the cast material is provided between the spacers to define individual casing chambers between the two shells and in which the piping system connects the individual casing chambers to each other and to the space below the grid chamber.

3. A hot blast stove as claimed in Claim 1 or Claim 2 in which the piping system opens into the space between the two sheet metal shells via nozzle-like tap pipes.