US3735970A

US3735970A - Method and apparatus for equalizing the gas pressures of sluice chambers and furnace zones of shaft furnaces, particularly blast furnaces

Info

Publication number: US3735970A
Application number: US00133895A
Authority: US
Inventors: U Genge
Original assignee: Demag AG
Current assignee: Mannesmann Demag AG
Priority date: 1970-04-04
Filing date: 1971-04-14
Publication date: 1973-05-29
Anticipated expiration: 1990-05-29
Also published as: NL7104317A; FR2085848B1; AT319296B; GB1331553A; FR2085848A1; DE2016205A1

Abstract

In such a pressure equalizing method in which raw top gas from the furnace zone is first purified and then fed into the sluice chamber, in a first pressure equalizing stage, the sluice chamber is filled with purified top gas directly from the purification zone, as from a purifier which the raw top gas is fed. In a second pressure stage, there is added, to the sluice chamber, a relatively small volume of top gas at furnace pressure to complete pressure equalization between the sluice chamber and the furnace zone. This latter top gas is drawn from a storage space communicating with the furnace zone and provided with labyrinth means effecting removal of dust from the top gas. A conduit, provided with a check valve, communicates with the sluice chamber, and a first line, connected to the purifier and provided with a control valve, and a second line, connected to the storage space and likewise provided with a control valve, are connected in parallel to the conduit communicating with the sluice chamber. A control device controls the sequential operation of the two control valves in the first and second lines.

Description

TJnited States Patent 91 [111 3,735,97@ Genge [451 May 29, 1973 [54] METHOD AND APPARATUS FOR EQUALIZING THE GAS PRESSURES OF SLUICE CHAMBERS AND FURNACE ZONESv OF SHAFT FURNACES, PARTICULARLY BLAST FURNACES Ulrich Genge, Mexico Inventor: Monclova Coah,

Assignee: Demag AG, Duisburg, Germany Filed: Apr. 14, 1971 Appl. No.: 133,895

Foreign Application Priority Data References Cited UNITED STATES PATENTS 1/1967 Mohr ..266/31 Primary Examiner--Gera1d A. Dost Attorney-John J McGlew and Alfred E. Page [57] ABSTRACT In such a pressure equalizing method in which raw top gas from the furnace zone is first purified and then fed 7 into the sluice chamber, in a first pressure equalizing stage, the sluice chamber is filled with purified top gas directly from the purification zone, as from a purifier which the raw top gas is fed. In a second pressure stage, there is added, to the sluice chamber, a relatively small volume of top gas at furnace pressure to complete pressure equalization between the sluice chamber and the furnace zone. This latter top gas is drawn from a storage space communicating with the furnace zone and provided with labyrinth means effecting removal of dust from the top gas. A conduit, provided with a check valve, communicates with the sluice chamber, and a first line, connected to the purifier and provided with a control valve, and a second line, connected to the storage space and likewise provided with a control valve, are connected in parallel to the conduit communicating with the sluice chamber. A control device controls the sequential operation of the two control valves in the first and second lines.

9 Claims, 4 Drawing Figures Patented May 29, 1973 3,735,970

3 Sheets-Sheet 1 ULRIQ H GENGE Patented May 29, 1973 3 Sheets-Sheet 2 lnz/emor:

ULR\C H GENGE 1 METHOD AND APPARATUS FOR EQUALIZING THE GAS PRESSURES OF SLUICE CHAMBERS AND FURNACE ZONES OF SHAFT FURNACES, PARTICULARLY BLAST FURNACES BACKGROUND OF THE INVENTION Known shaft furnaces, such as blast furnaces, for example, have, at the furnace head, a seal formed by two or more bells and two or more throat cups or disks. The two bells arepositioned one above the other, with the upper bell being the smaller and serving to distribute the charge material on the larger lower bell. The larger lower bell is adapted to the furnace diameter, the material being distributed on the circular charging surface.

. The distributing function is therefore determining for the selection of the different bell diameters.

Due to the thermal stress, it is unfavorable to make the lower bell larger, but the distribution of the material determines the working of the furnace and thus the output. Consequently, the distributing function overrules the scaling function.

Nevertheless, because the pressure has been increased in recent times, a good seal at the throat of blast furnaces has gained in importance. The higher gas pressure in the furnace zone of blast furnaces and other furnaces, which operate even with negative pressure (brick-burning furnaces), promotes the chemicalphysical processes. Thus, a higher pressure in blast furnaces has a positive effect on the process of iron ore reductiomHowever, higher requirements are stipulated for the sealing effect of the throat stoppers.

In the case of two-bell throat stoppers, the two bells can be actuated only when the pressure above and below in the sluice chamber formed by a throat cup or disk is the same. Therefore, if the upper bell is opened,

.atmospheric pressure must prevail in the throat cup therebelow, that is, the pressure previously present therein must have been lowered by release of gas.

On the other hand, the pressure in the sluice chamber must be more or less the same as the furnace zone pressure, if it is to be possible to openthe lower throat hell with an economically acceptable expenditure of energy. For each furnace zone charge, as well as .for the charging of the larger bell, pressure equalization in the sluice chamber located between the two bells is necessary. In principle, the gas used for this purpose may be the gas originating from the furnace or may be gas from an external source.

I The furnace gas of blast furnaces is heavily dustladen, but it is correspondingly inexpensive and requires little additional equipment. However, the dust entrained in the blast furnace top gas causes a great deal of wear at the packing or sealing seats of bells and throat cups. Unless it is possible to effect a very extensive pressure equalization between the sluice chamber Because of the entrained dust, rapidly flowing gas increases the wear effect. Usually such flow cannot be prevented if only for the reason that the bells warp under thermal stress. Exact pressure equalization is therefore an important measure for the maintenance of the seal at throat stoppers. It is very difficult to obtain a sufficiently quick and also still exact pressure equalization in a two-bell or multi-bell throat stopper. The gas originating from the furnace must be subjected at least to a preliminary dust removal, in order not to damage the valves which determine the pressure in the line. Consequently, there occurs, as a rule, an inevitable pressure loss in the dust separator, which would justify the use of dust-free gas from an external source.

Dust-free gas from an external source, present at high pressure in the plant system, for example, nitrogen, offers advantages of trouble-insensitive operation, insofar as the wear of the closing elements is affected thereby. However, the expense of regulation and production are very high, because safety measures must be taken to protect the sluice chambers from pressures far beyond the design values. Uncertainty persists even if expensive safety measures are taken, because of the rough nature of blast furnace operation.

When using top gas, produced by the furnace, for increasing the pressure in the sluice chamber, the top gas hitherto has been purified, because otherwise the wear is too high. Depending on the type of purification in different available dust separators, a pressure drop, relative to 'the furnace gas pressure, occurs. In some of the furnaces that have been constructed, the available pressure is considered sufi'icient. However, in others additional compression has been provided but again, for various reasons, only purified top gas is permissible for this.

-Both methods for pressure equalization in the sluice chamber have certain shortcomings. In the first case, the mentioned high gas velocities occur at the packing seats of the bells and cups. Also, when using packing valves whose packing seats lie outside the path of the charged material, the dust is disagreeable. Consequently, wear to a greater or less extent always exists. In the second case, the additionally required compression leads to continual high operating cost and to da'nger to the equipment parts since, for reasons of the compressor size and the relatively short pressure equalization times, the operation must be effected with pressures beyond the design pressure of the throat stopper. The wear is particularly heavy when throat stoppers using bells are still used for distributing the material in the furnace zone.

SUMMARY OF THE INVENTION This invention relates to equalizing the gas pressure of sluice chambers and furnace zones of shaft furnaces and, more particularly, to a novel, improved, simplified and less expensive method and apparatus for effecting such pressure equalization, and which provides for an exact pressure equalization.

Simply to accept the pressure difference with all its disadvantages is known. It is also known how to insert a compressor in the pure-gas system, which increases the pressure to such an extent that, simultaneously with the opening of the shut-off elements, the necessary gas acceleration is attained.

In accordance with the invention, however, in a first pressure equalization stage, the sluice chamber is filled with purified top gas directly from the purifier and, in

- second stage, a compressor is used, the compressor is very small and it is possible to process already available pure gas. If raw or stack gas from the furnace zone is used, the conditions are much more favorable because of the small quantity or volume. These measures permit a number of improvements, and it is of particular advantage to be able to accelerate a residual gas quantity of higher pressure.

The method of pressure equalization embodying the invention makes use of the realization that, after filling of the sluice chamber with purified top gas from the line system downstream of the gas purification, but before the furnace pressure control element, the pressure difference with respect to the furnace pressure has a maximum value of 2000 mm H 0, and usually only 500 to 1000 mm H O. The furnace gas volume portion, which is necessary to obtain, in the sluice chamber, the same pressure as in the furnace zone, is then only a few cubic meters, as the following calculation proves:

Sluice chamber volume less volume v 20 m of the charge materials Gas temperature r 50C Operating pressure p 3.0 ata Pressure difference dp 1000 mm H Atmospheric pressure p, 1.0 ata Difference volume to attain furnace head pressure dV, [Nm] a. Gas quantity to attainment of the pressure p 2.9 ata:

V 20 X (273/323) X (2.9/1.0) 49.05 Nrn b. Gas quantity to attainment of the pressure p 3.0 ata:

v 20 x 273 323 3.0/1.0 50.70 Nm v, V V,, 1.65 Nm This calculation relates to a furnace zone pressure of 2 ata. Consequently, it is sufficient to provide 1.65 Nm in the second pressure stage at a pressure of 2 ata. In practice, this filling up of the sluice chamber represents only a pulse controlled as to time, the gas quantity being limited automatically.

It is further advantageous if raw gas is taken from the furnace zone as the top gas for the second pressure stage, with the raw gas being stored, before being added to the sluice chamber, and thus quieted. The disadvantage of the wearing effect of the dust particles is avoided by their simple separation from the raw gas. This separation takes place while the raw gas is at rest, and this step of the invention is particularly valuable. In fact, if the dust particles participate in the high acceleration, they form dangerous abrasives at initially high flow velocities (far above 100 m/sec). The great kinetic energy of the dust particles, whose grain diameter may be up to mm, causes, in particular, high abrasion at pipe bends and individual resistances, such as valves, for example. Certain dusts, such as coke, fines, are moreover outstanding for their high hardness.

A simple separation by quieting the flow is further augmented by storing a quantity of crude gas which is greater, by a multiple, than that necessary for the pressure equalization process. The separation of the dust particles from the crude gas additionally can be augmented by maintaining a lower flow velocity in the storage zone during the second pressure stage.

The apparatus for performing the process includes a storage zone for raw top gas and connected to the furnace zone. From this storage zone, a closable conduit extends to the sluice chamber of the throat stopper, and this closable conduit can additionally be supplied with pure gas from a top gas purifier. In addition to its function of storing raw or stacked gas, the storing zone serves as an accumulator. The last residue of the planned quantity of sluice gas can be forced into the sluice chamber at an accelerated rate. By means of a pressure wave, the filling of the sluice chamber is facilitated.

To increase the safety of operation, the supply lines of the purifier and the crude gas reservoir, which are connected in parallel with each other, are provided with respective shut-off elements before the entrance to the sluice chamber. Thus, in case of defects, it is possible to switch over from one inflow valve to the other. In addition, the parallel connection permits precisioncontrolling of the succession of pressure waves of pure gas and of raw or stack gas roughly freed from dust.

In accordance with another feature of the invention, separation of the dust is effected in a raw gas reservoir which is provided with catch basins for the dust contained in the stack gas. It is thus possible for the operator of the equipment either to retain the dust in the basins or merely to return the dust into a riser which carries the crude or raw gas. Another possibility is to return the dust to the furnace head elsewhere through a separate dust tube. v

The invention also provides that the pure gas line and the raw gas line have greatly differing diameters, with the raw gas line having the larger cross-section. As a result, the raw gas flows at a greatly reduced velocity and, owing to this, the dust particles fall out of the raw gas more easily.

An object of the invention is to provide an improved method for equalizing the gas pressures of sluice chambers and furnace zones of shaft furnaces.

Another object of the invention is to provide an improved apparatus for performing the method.

A further object of the invention is to provide such a method and apparatus by means of which an exact pressure equalization can be effected.

Another object of the invention is to provide such a method and apparatus in which, during pressure equalization, the sluice chamber is initially filled with purifled gas after which there is added, to the sluice chamber, a small volume of furnace gas at the furnace zone pressure.

For an understanding of the principles of the invention, reference is made to the following description of typical embodiments thereof as illustrated in the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 is a somewhat schematic elevation view of a blast furnace provided with the apparatus of the invention and having a throat stopper whose sluice chamber is provided with dampers;

FIG. 2 is a somewhat schematic partial elevation view illustrating the apparatus of the invention as applied to a shaft furnace having a bell-type throat stopper;

FIG. 3 is a graphical illustration of the gas volume dV (Nm at constant volume in the sluice chamber, as a function of different pressure differences, plotted with relation to the furnace throat pressure; and

FIG. 4 is a diagram for the gas volume, at constant pressure difference p (mm H O) as a function of the volume in the sluice chamber V (m*).

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, the sluice chamber 1 and furnace zone 2 of a blast furnace are arranged one above the other for the purpose of gas pressure-loss-free' admission of the charge material from the free atmosphere into the furnace zone 2. Through an aperture, which is illustrated in FIG. 1 as closed with a sealing valve or damper 3, the charge material passes into sluice chamber I, where it accumulates on

dampers

4 and 5 until released by an aperture illustrated as closed with a sealing damper 6. Distribution of the material occurs on a distributor bell 7 arranged in the furnace head, but alternatively other distributing devices may be provided.

The top gas, forming in the furnace zone 2, is discharged through

gas discharge pipes

8, 9, 10 and 11, arranged around the circumference of the furnace, and leading to explosion or safety valves 14. Another discharge pipe 12, also provided with the safety valve 13, serves for blowing off upon stopping of the operation or beginning of the operation. From the gas discharge pipes, the raw or stack gas passes through gas discharge pipe into the purifier 16, from which the purified furnace gas flows through a throttle wall 17 toward the pure gas consumers.

The sluice gas, in sluice chamber 1, can be let off or discharged through discharge line 19 and valve 20 when sealing damper 3 is'to be opened to admit the charge material. The pure gas, which is not yet expanded, can flow through a conduit or line 18, upstream of the throttle valve 17, and which line is controlled by a shut-off means 21. A control pulse occurs only when, for the purpose of pressure equalization be- ,tween sluice chamber 1 and furnace zone 2, the pressure difference is to be equalized. As will be explained, this control pulse is applied to the valve or shut-off means 21. The raw gas, flowing through

gas discharge pipes

8, 9, 10, 11 and 15 into purifier 16, undergoes a pressure drop, depending on the characteristics of the discharge pipes and the purifiers. The pure gas therefore is available, at shut-off means or valve 21, at a lower pressure.

In accordance with the invention, a storage space 22 is provided and is supplied with raw gas through a conduit 23 connected to the furnace zone 2, for example through one or more of the

discharge pipes

8, 9, l0 and 11. The raw gas cannot flow through storage space 22, as it is blocked by a shut-off means or valve 24. During accumulation of the raw gas in storage space 22, the dust particles fall out of the mass of raw gas moving over the labyrinth sheets 25, or similar catch basins, having projections 26. If conduit 23 extends upwardly and outwardly at a steep angle, the dust falls back into gas discharge pipe 9 and into furnace zone 2.

If pressure equalization now becomes necessary, shut-off valve 21, for the pure gas, is opened to fill sluice chamber 1 through the then open check valve 27. As soon as the pure gas pressure begins to decrease, there occurs the opening of the shut-off valve 24 and the dust-free raw gas flows up into the conduit 28. Be-

fore this, shut-off valve 21 is closed, by control device 29, so that a cycle takes place under the control of pulses provided by control device 29 which measures the pressure differences. Vent valve 30 on branch line 31 serves to vent the pipe system after stoppages.

Proportioning of the gas quantities need not occur through a common conduit 28. However, it is advantageous to connect pure gas line 18 and raw gas line 32 in parallel to conduit 28.

Lines

18 and 32 may have different diameters, with raw gas line 32 havinga much greater diameter or cross-section at 33 than pure gas line 18. The ratio of the diameters and cross-sections is established in accordance with the rate of flow and the desired pressures.

In the embodiment of the invention shown in FIG. 2, the throat stopper consists of three

bells

34, 35 and 36. Together with cups37 and 38, these form sluice chambers 1. Pure gas line 18 and raw gas line 32 deliver gas into the upper sluice chamber 1 separately. Otherwise, the process of pressure equalization is the same as described for FIG. 1.

From FIGS. 3 and 4, there can be seen the values for the residual gas volumes of the second pressure stage for different pressures of the pure gas. Pressure differences result in dependence on the use of certain purifiers. The residual gas volumes resulting for different pressures, depending on the throat stopper size, can be seen in FIG. 4.

While specific embodiments of the invention have been shown and described in detail to illustrate the ap plication of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is:

1. In a method for equalizing the gas pressures of sluice chambers and furnace zones of shaft furnaces, particularly blast furnaces, in which raw top gas from the furnace zone is first purified and then fed into the sluice chamber, the improvement comprising, in a first pressure equalization stage, filling the sluice chamber with purified top gas directly from the purification zone; and, in a second pressure stage, adding, to the sluice chamber, a relatively small volume of top gas at furnace pressure to complete pressure equalization between the sluice chamber and the furnace zone; the top gas added in the second pressure stage comprising raw gas delivered directly from the furnace zone to a storage zone, in which the raw gas remains quiescent; the top gas for the second pressure stage being delivered from the storage zone to the sluice chamber.

2. In a method for equalizing the gas pressures of sluice chambers and furnace zones of shaft furnaces, particularly blast furnaces, in which raw top gas from the furnace zone is first purified and then fed into the sluice chamber, the improvement comprising, in a first pressure equalization stage, filling the sluice chamber with purified top gas directly from the purification zone; and, in a second pressure stage, adding, to the sluice chamber, a relatively small volume of top gas at furnace pressure to complete-pressure equalization between the sluice chamber and the furnace zone; the top gas added in the second pressure stage comprising raw gas delivered directly from the furnace zone to a storage zone, in which the raw gas remains quiescent; the top gas for the second pressure stage being delivered from the storage zone to the sluice chamber; the rate of flow of gas to the sluice chamber, in the second pressure stage, being lower than the rate of flow of purified top gas to the sluice chamber during the first pressure equalization stage.

3. In a method for equalizing the gas pressures .of sluice chambers and furnace zones of shaft furnaces, particularly blast furnaces, in which raw top gas from the furnace zone is first purified and then fed into the sluice chamber, the improvement comprising, in a first pressure equalization stage, filling the sluice chamber with purified top gas directly from the purification zone; in a second pressure stage, adding, to the sluice chamber, a relatively small volume of top gas at furnace pressure to complete pressure equalization between the sluice chamber and the furnace zone; the top gas added in the second pressure stage comprising raw gas delivered directly from the furnace zone to a storage zone, in which the raw gas remains quiescent; the top gas for the second pressure stage being delivered from the storage zone to the sluice chamber; and removing dust from the raw gas during flow of the raw gas from the furnace zone into the storage zone.

4. In a method for equalizing the gas pressures of sluice chambers and furnace zones of shaft furnaces, the improvement claimed in claim 1, in which the quantity of raw gas stored in the storage zone is a multiple of the quantity of top gas necessary to effect pres sure equalization in the second pressure stage.

5. In apparatus for equalizing the gas pressures of sluice chambers and furnace zones of shaft furnaces, particularly blast furnaces, of the type in which raw top gas from the furnace'zone is first purified and then fed into the sluice member, and including throat stopper means selectively operable for charging material from the sluice chamber into the furnace zone, the improvement comprising, in combination, means forming a storage zone, for holding quiescent raw top gas, communicating with said furnace zone; closable conduit means controlling connection of said storage zone to the sluice chamber associated with said throat stopper means; a raw gas purifier connected to said furnace zone; and means operable to supply purified top gas from said purifier to said sluice chamber.

6. In apparatus for equalizing the gas pressures of sluicechambers and furnace zones of shaft furnaces, the improvement claimed in claim 5, including a conduit connected to said sluice chamber; a check valve in said conduit blocking flow from said sluice chamber through said conduit; respective supply lines connecting said purifier and said storage zone means to said conduit outwardly of said check valve; and respective shut-off means interposed in each supply line; said supply line connecting said storage zone means to said conduit constituting said closable conduit means.

7. In apparatus for equalizing the gas pressures of sluice chambers and furnace zones of shaft furnaces, the improvement claimed in claim 6, in which the supply line connecting said storage zone means to said sluice chamber has a much greater flow area than does the supply line connecting said purifier to said sluice chamber.

v8. In apparatus for equalizing the gas pressures of sluice chambers and furnace zones of shaft furnaces, particularly blast furnaces, of the type in which raw top gas from the furnace zone is first purified and then fed into the sluice chamber, and including throat stopper means selectively operable for charging material from the sluice chamber into the furnace zone, the improvement comprising, in combination, means forming a storage zone, for raw top gas, communicating with said furnace zone; closable conduit means controlling connection of said storage zone to the sluice chamber associated with said throat stopper means; a raw gas purifier connected to said furnace zone; means operable to supply purified top gas from said purifier to said sluice chamber; and dust separators and retainers in said storage zone means operable to separate and collect dust from the raw gas entering said storage zone means from said furnace zone.

9. In apparatus for equalizing the gas pressures of sluice chambers and furnace zones of shaft furnaces, the improvement claimed in claim 6, including a control device controlling opening of said shut-off means, and subjected to the respective pressures in said sluice chamber and said furnace zone.

Claims

2. In a method for equalizing the gas pressures of sluice chambers and furnace zones of shaft furnaces, particularly blast furnaces, in which raw top gas from the furnace zone is first purified and then fed into the sluice chamber, the improvement comprising, in a first pressure equalization stage, filling the sluice chamber with purified top gas directly from the purification zone; and, in a second pressure stage, adding, to the sluice chamber, a relatively small volume of top gas at furnace pressure to complete pressure equalization between the sluice chamber and the furnace zone; the top gas added in the second pressure state comprising raw gas delivered directly from the furnace zone to a storage zone, in which the raw gas remains quiescent; the top gas for the second pressure stage being delivered from the storage zone to the sluice chamber; the rate of flow of gas to the sluice chamber, in the second pressure stage, being lower than the rate of flow of purified top gas to the sluice chamber during the first pressure equalization stage.

3. In a method for equalizing the gas pressures of sluice chambers and furnace zones of shaft furnaces, particularly blast furnaces, in which raw top gas from the furnace zone is first purified and then fed into the sluice chamber, the improvement comprising, in a first pressure equalization stage, filling the sluice chamber with purified top gas directly from the purification zone; in a second pressure stage, adding, to the sluice chamber, a relatively small volume of top gas at furnace pressure to complete pressure equalization between the sluice chamber and the furnace zone; the top gas added in the second pressure stage comprising raw gas delivered directly from the furnace zone to a storage zone, in which the raw gas remains quiescent; the top gas for the second pressure stage being delivered from the storage zone to the sluice chamber; and removing dust from the raw gas during flow of the raw gas from the furnace zone into the storage zone.

4. In a method for equalizing the gas pressures of sluice chambers and furnace zones of shaft furnaces, the improvement claimed in claim 1, in which the quantity of raw gas stored in the storage zone is a multiple of the quantity of top gas necessary to effect pressure equalization in the second pressure stage.

5. In apparatus for equalizing the gas pressures of sluice chambers and furnace zones of shaft furnaces, particularly blast furnaces, of the type in which raw top gas from the furnAce zone is first purified and then fed into the sluice chamber, and including throat stopper means selectively operable for charging material from the sluice chamber into the furnace zone, the improvement comprising, in combination, means forming a storage zone, for holding quiescent raw top gas, communicating with said furnace zone; closable conduit means controlling connection of said storage zone to the sluice chamber associated with said throat stopper means; a raw gas purifier connected to said furnace zone; and means operable to supply purified top gas from said purifier to said sluice chamber.

6. In apparatus for equalizing the gas pressures of sluice chambers and furnace zones of shaft furnaces, the improvement claimed in claim 5, including a conduit connected to said sluice chamber; a check valve in said conduit blocking flow from said sluice chamber through said conduit; respective supply lines connecting said purifier and said storage zone means to said conduit outwardly of said check valve; and respective shut-off means interposed in each supply line; said supply line connecting said storage zone means to said conduit constituting said closable conduit means.

7. In apparatus for equalizing the gas pressures of sluice chambers and furnace zones of shaft furnaces, the improvement claimed in Claim 6, including a control device controlling opening of said shut-off means, and subjected to the respective pressures in said sluice chamber and said furnace zone.

8. In apparatus for equalizing the gas pressures of sluice chambers and furnace zones of shaft furnaces, particularly blast furnaces, of the type in which raw top gas from the furnace zone is first purified and then fed into the sluice chamber, and including throat stopper means selectively operable for charging material from the sluice chamber into the furnace zone, the improvement comprising, in combination, means forming a storage zone, for raw top gas, communicating with said furnace zone; closable conduit means controlling connection of said storage zone to the sluice chamber associated with said throat stopper means; a raw gas purifier connected to said furnace zone; means operable to supply purified top gas from said purifier to said sluice chamber; and dust separators and retainers in said storage zone means operable to separate and collect dust from the raw gas entering said storage zone means from said furnace zone.

9. In apparatus for equalizing the gas pressures of sluice chambers and furnace zones of shaft furnaces, the improvement claimed in claim 8, in which the supply line connecting said storage zone means to said sluice chamber has a much greater flow area than does the supply line connecting said purifier to said sluice chamber.