Patent ID: 12235047

DETAILED DESCRIPTION

A preferred embodiment of the method will be described applied in the context of a shaft furnace, generally a blast furnace. Such a shaft furnace is partially shown inFIG.1, comprising a lower part with a hearth portion10where iron and slag are collected, and a shell having an inner wall12forming a generally cylindrical barrel which extends upwardly from the hearth portion10. For a better understanding, reference14represents part of the furnace interior volume, wherein, in operation, burden material (not shown) is charged.

As shown inFIG.1, the inner wall12comprises portions of different diameters. From the hearth portion10to the top, the shaft furnace comprises a tuyere surrounding16, a bosh portion18, a belly portion20and a stack portion22. Above the stack portion22, the shaft furnace further comprises a throat and a charging installation (not shown) for charging material into the shaft furnace.

The inner wall12is covered by a lining of heat protection elements, such as e.g. cooling staves24. The cooling staves24are further covered by a lining of refractory material26in the tuyere surroundings16and bosh portion18of the inner wall12. In other embodiments, the inner wall may be covered by a different lining or by more than one lining with heat refractive material and/or cooling elements.

The cooling staves24are generally arranged in rows of adjacent staves mounted on top of one another from the tuyere surroundings16to the top of the stack portion22. The cooling staves24may have different shapes and material and comprise a cooling circuit (not shown) for circulating a cooling fluid therein.

The method for protecting the inner wall12of the shaft furnace according to one preferred embodiment of the disclosure comprises one step of providing a plurality of injection devices28through the inner wall12of the shaft furnace. The injection devices28are configured to inject protective material30into the shaft furnace. The injection devices28are advantageously provided over the circumference of the shaft furnace and distributed in rows to cover all the portions of the inner wall12. The quantity and position of the injection devices28may vary depending on the shape and dimensions of the inner wall12, and on the type of injection device28used.

The injection device28may comprise any appropriate device and may be designed according to the type of protective material that will be injected into the shaft furnace. The injection devices28are schematically represented inFIG.1comprising a straight injection lance32and a supply apparatus34. The injection lance32comprises an open end36in the furnace interior14and forms a canal between the supply apparatus34and the interior14of the shaft furnace. The supply apparatus34is configured to route the protective material from storage means (not shown) through the injection lance32into the interior14of the shaft furnace.

The injection devices28are provided from the outside of the shaft furnace and are fed through the inner wall12. Connection of the injection devices28may be obtained by any suitable means, such as for example by welding.

As shown inFIG.1, the open ends36of the injection lances32may be arranged at different orientations depending on their location in the inner wall12. The orientation is adapted in relation with the local inclination of the inner wall12. The inner wall12in the bosh portion18of the furnace is slanted toward the exterior of the shaft furnace and, accordingly, the injection lances32passing through the inner wall of the bosh are preferably essentially horizontal. In the belly portion20, the inner wall12is essentially vertical and the open ends36of the injection lances32are arranged at an angle relative to the horizontal, pointing down into the furnace interior14. In the stack portion22, the inner wall12is slanted toward the interior of the shaft furnace, narrowing the shaft furnace width until the throat. In the latter portion of the inner wall12, the injection lances32are roughly vertical.

FIGS.2to5show different embodiments wherein the open end36of the injection lance32is provided in different locations relatively to one cooling stave24.

InFIGS.2to5, the cooling stave24has a hot face40facing the interior of the furnace and a cold face38facing the inner wall12of the shaft furnace. The hot face40of the cooling stave24comprises a profile with ribs42and grooves44. The cold face38of the cooling stave24is connected to the inner wall12by any suitable means (not shown). Here, a gap46is provided between the cold face38and the inner wall12. The gap46may be filed with a refractory material. The gap46comprises a spacer48between the cooling stave24and the inner wall12that is configured to maintain the cooling stave24at a predetermined distance from the inner wall12. A passage for the injection lance32is preferably arranged in the spacer48in order to protect the injection lance32from the refractory material. In these embodiments, the installation further comprises a guiding pipe50used to guide the injection lance32on the outer side of the inner wall12.

In the four embodiments ofFIGS.2to5, the injection device28is provided with an injection lance32essentially perpendicular to the cooling stave24. The skilled person will understand that the orientation of the injection lance32may be different without changing the location of the open end36of the injection lance32.

In the embodiment as shown inFIG.2, the injection lance32passes through the cooling stave24and opens into a groove44of the stave profile.

In the embodiment ofFIG.3, the injection lance32passes through the cooling stave24and opens into a rib42of the stave profile.

In the embodiments ofFIGS.4and5, the cooling stave24further comprises a ledge52protruding from its hot face40. The ledge52is generally provided in order to disturb a flow of burden material along the cooling stave24. The ledge52is also configured to retain burden material on top of it and to allow formation of a localized material layer that protects the cooling stave24from abrasion.

In the embodiment ofFIG.4, the injection lance32passes through the cooling stave24and opens into the hot face40of the cooling stave24at a location above the ledge52.

In the embodiment ofFIG.5, on the other hand, the injection lance32passes through the cooling stave24and opens into the hot face40of the cooling stave24at a location below the ledge52.

In operation, the injection devices28are used for injecting the protective material into the shaft furnace. Such injection may be carried out on demand, in such a manner that the protective material builds up to form a protection wall between the interior of the furnace and the furnace wall.

The protective material30comprises here solid material carried by a fluid carrier. The solid material may for example comprise slag, coal, ore sinter, refractory material, mills scales or pellet, to have a limited impact on the reaction inside the shaft furnace. For the same reasons, the fluid carrier may for example comprise blast furnace clean gas or N2.

Once injected, the protective material30simply flows down along the hot face40of the cooling staves24by gravity and covers the surface of the inner wall12, thereby forming an accretion layer54on the hot face40of the cooling staves24. As shown inFIG.1, in the tuyere surroundings16and bosh portion18, the accretion layer54is formed on the lining of refractory material26to protect or further protect the cooling staves24.

When burden material is charged into the shaft furnace, it comes into contact with the accretion layer54, suppressing abrasion effects to the cooling staves24. To minimize a potential abrasion effect caused by the protective material30flowing over the cooling staves24, the protective material30may comprise granular material of e.g. round shape.

The protective material30is further injected on demand before the cooling staves become exposed to the burden material. During furnace operation, the burden material continuously flows down to the hearth of the shaft furnace. The flow of burden material carries along particles of the protective layer, reducing the thickness of the accretion layer54. The protective material30may therefore be injected at a certain flow rate to maintain a predetermined minimum thickness of protective layer between the burden material and the staves24. If a more rapid thinning of the accretion layer54is detected in a particular region of the shaft furnace, the injection of protective material30may be regulated to increase the amount of protective material through a selected injection device in order to compensate for such localized thinning.

The protective material30can be injected through N2gas at a predefined pressure depending on the pressure of burden material at the open end36of the injection lance32. This is particularly advantageous if the protective material30is in granular form. If the protective material30is however in a larger solid form, such as e.g. slag, coal, ore, sinter, refractory material, mills scales or pellet, it may be more advantageous to inject the protective material30mechanically. To this effect, the injection device may e.g. comprise a piston for pushing the protective material into the shaft furnace.

In embodiments, the protective material30may comprise solid blocks of material successively injected into the furnace, or different protective material may be successively injected. For example, the method may comprise a first step of injecting a layer of fluid material; then injecting solid material into the layer of fluid material.