EP0746595B1 - Method for repairing at high temperatures industrial facilities including a structure made of refractory materials. - Google Patents

Abstract

A method for repairing industrial facilities at high temperatures using at least one prefabricated element (1) made of mullite-crystallized refractory product with an alumina content of 30-80%, preferably 50-80%, made of refractory materials securely attached to the structure (11) of the facility by using an oxygen-containing carrier gas stream to spray a mixture of particles capable of exothermically reacting with the oxygen and particles of a refractory material, whereby a coherent refractory mass (14) is formed in situ for attaching said element to said structure.

Description

The present invention relates to a repair process and / or partial construction at hot industrial facilities including a structure in refractory materials, in particular installations operating by indirect heating using flues, such as coke oven batteries, according to which at least one element is used prefabricated in refractory materials which are secured with said structure by reactive projection, by means a carrier gas stream containing oxygen, a mixture of particles which can react exothermically with oxygen and particles of refractory material, preferably inert.

As in installations industrial, as defined above, the structures made of refractory materials, which are generally siliceous and silica in nature, must always be maintained at a temperature above 300 ° C to avoid their weakening by polymorphic transformation, hot repair processes have long been proposed for their repair. These processes can also be used for partial constructions such installations, in particular to modify a existing structure by adding a wall or a conduit evacuation of burnt gases for example.

This is how silica bricks glassy, characterized by a very low coefficient of dilation, have been developed and implemented conventional way to make such repairs to hot. However, it was noted that these repairs were not gas tight, especially in the case batteries of coke ovens.

French patent FR 2541440-B1 (Glaverbel) describes a hot repair process using, on the one hand, such bricks of vitreous silica and, on the other hand, a ceramic welding process for make the joints of the new masonry and the full reloading of the structure (GB 1.330.894 and GB 2.110.200 A from Glaverbel). In this process, the bricks of glassy silica preferably have a chamfer for facilitate the creation of joints.

In another patent using the same ceramic welding process (DE 3643420 A1, Fosbel Europe), full thickness repair bricks are this time fitted and then brought to temperature before filling the space between the old and the new masonry by ceramic welding without however fully recharge the area repaired by welding ceramic.

In general, although the glassy silica bricks, when brought to high temperature, start a slow process of crystallization (in cristobalite and tridymite), they do not keep their sensitivity to creep when they are subjected to a load at high temperature.

This effect is observed in coke ovens where repairs of this type in the vicinity of the flues show noticeable subsidence after some time commissioning.

One of the essential purposes of this invention aims to propose a new method to remedy to the aforementioned drawbacks calling into question the reliability of this type of repair or partial construction and this in a relatively simple and economical way justified.

To this end, the invention provides a method of hot repair of industrial installations comprising a structure of refractory materials (11) of a siliceous nature, in particular installations operating by indirect heating using flues (10), such as batteries of coke ovens, according to which use is made of at least one prefabricated element (1) made of refractory materials which is secured to said structure (11) by projection, by means of a stream of carrier gas containing oxygen, a mixture of refractory particles and particles which can react exothermically with oxygen chosen from the group formed on the one hand, by the following metals: Al, Si, Mg, Ca, Fe, Cr, Zr , Sr, Ba and Ti, and, on the other hand, by the compounds of these metals which can, by decomposition, form with oxides derived from these metals, mixed oxides, so as to constitute a binding phase for the abovementioned particles in refractive material shut up, these particles of a refractory material making it possible to form in situ a coherent refractory mass (14) fixing the above-mentioned element to the structure of refractory materials and being formed by at least one of the oxides chosen from the group comprising SiO ₂ , Al ₂ O ₃ , ZrO ₂ , MgO, Cr ₂ O ₃ , TiO ₂ , CaO, characterized in that one uses, on the one hand, a prefabricated element (1) in a refractory product with mullitic crystallization having a content in alumina of between 30 and 85% and preferably between 50 and 80% of alumina, and, on the other hand, a mixture of particles which can react exothermically with oxygen and of particles of a refractory material, the composition of which is such as to form in situ a refractory mass (14) which is compatible with the composition and the coefficient of thermal expansion of the above-mentioned element (1) and of the structure (11) to which this mass (14) must be attached, and this taking into account the requests ions to which the latter will be subjected under working conditions.

According to an embodiment particular of the invention, for installations including heat treatment chambers heated to using flues, we place on the side of these the aforementioned prefabricated element and on the side of the heat treatment we will apply the refractory mass consistent above.

We also describe an element prefabricated for repair or partial construction hot industrial installations comprising a structure in refractory materials, in particular installations operating by indirect heating using flues, such as coke oven batteries, which may in particular be suitable for implementing the aforementioned process.

This prefabricated element is characterized by the fact that it is based on a refractory product to Mullitic crystallization with alumina content between 30 and 85% and preferably between 50 and 80% alumina and which preferably has a prismatic shape rectangular, one of the faces of which is provided with means for perform mechanical attachment with a refractory mass coherent formed by reactive projection on this face.

Other details and peculiarities of the invention will emerge from the description given below, by way of nonlimiting example, with reference to the drawings attached, of some particular embodiments of the process according to the invention and a prefabricated element allowing to implement this method.

Figure 1 is a sectional view along line I-I of FIG. 2, of a prefabricated element suitable for implementing the method according to a preferred embodiment of the invention.

Figure 2 is a front view of the prefabricated element.

Figure 3 shows a section vertical portion of coke oven wall repaired by the implementation of the method according to the invention.

Figure 4 is a horizontal section partial reconstruction of part of flues according to the method of the invention.

Figure 5 shows a graph showing the expansion curve in% as a function of the temperature of different refractory products.

In these figures, the same numbers of reference relate to analogous items or identical.

The present invention therefore also relates to well hot repair of industrial plants comprising a structure of refractory materials that the hot reconstruction of part of such installations industrial and hot modifications to them.

More concretely, the process, following the invention is based on the dissociation of stresses encountered at the exchange wall of heat from a structure of refractory materials industrial installation. Thus, according to the invention, we considers the stresses exerted on this wall, on the one hand, on the heating side where, for example, the flues, and on the other hand, on the opposite side of this wall where is the heat treatment chamber.

The invention is therefore applicable in all industrial facilities where such situation occurs.

However, since the ovens coke constitute industrial installations where repairs to the heat exchanger walls must regularly performed, the description given below will be limited to this particular application.

To physically perform the above-mentioned dissociation, appeal is made to the place where the repair of the wall in question must take place, two separate materials which are joined so as to achieve this place a "bi-layer" sign. So on the side of the flue, we use a refractory product well suited to requests encountered at this location. However, side of the heat treatment chamber we will form a refractory lining well adapted to the stresses which are their own.

According to the invention, on the side, flue, prefabricated elements in one product mullitic crystallization refractory having a alumina content between 30 and 85% and preferably between 50 and 80% alumina (the remainder being essentially formed of silica), which is secured to the wall to be repaired on the side of the treatment chamber thermal by projection, by means of a gas stream carrier containing oxygen, a mixture of particles of exothermically oxidizable material and particles of refractory material. The composition of this mixture is chosen in such a way as to form a mass in situ refractory that is compatible with the composition and coefficient of thermal expansion, on the one hand, of the element and, on the other hand, the original masonry, and this taking into account the stresses to which this mass will be subject to working conditions.

It has been found that this element prefabricated has the advantage of having good strength thermal shock, while ensuring refractoriness, high mechanical strength and creep resistance in a wide range of temperatures.

Furthermore, in an unpredictable way, it has been found that it is possible simply by a judicious choice of the components of the mixture and their content in the latter, to form by reactive projection of this mixes a coherent refractory mass, which has a excellent compatibility with prefabricated elements used and the original masonry of the wall to be repaired, whether in terms of thermal expansion, refractoriness only from the point of view of chemical behavior.

In addition, according to the invention, although the refractory mass thus deposited by reactive projection on the prefabricated elements can have a nature chemical different from that of these elements, this mass refractory constitutes with these elements a very good interface.

Advantageously, the granular fraction of inert refractory particles based on oxides such as: SiO ₂ , Al ₂ O ₃ , ZrO ₂ , MgO, Cr ₂ O ₃ , TiO ₂ , CaO, can be used under different mineralogical varieties and / or associated forms, according to the technological interest, and the pulverulent fraction composed of oxidizable particles of metallic nature such as: Al, Si, Mg, Fe, Cr, Zr, Ti can be used in certain particular embodiments, such as those described in the international patent application PCT / BE92 / 00012 of the same holder, having the international publication number WO 92/19566, chemical substances which, by decomposition, form, with the oxides derived from the oxidizable particles, mixed oxides so as to constitute a binding phase for inert refractory particles. The term “chemical substance” should be understood to mean in particular metallic peroxides, such as CaO ₂ , MgO ₂ , BaO ₂ , SrO ₂ or metallic salts such as AlCl ₃ , SiCl ₄ , MgCl ₂ .

By refractory particles based on the oxides mentioned, it is necessary to understand their different mineralogical varieties such as tridymite, cristobalite and silica glass for SiO _{2 as} well as associated forms like zircon ZrSiO ₄ , spinel MgAl ₂ O ₄ , zirconia stabilized with CaO or MgO, the solid solution Al ₂ O ₃ -Cr ₂ O ₃ in any proportion, etc., which each have a particular technological interest depending on the application envisaged.

When the aforementioned structure, that is to say the original masonry, is essentially in siliceous refractory, as is generally the case with walls of coke ovens, a mixture of particles is used oxidizable and refractory for reactive projection which are chosen in such a way as to form a mass consistent refractory which is also essentially siliceous.

According to the invention, it was again found that by choosing the nature and relative content different oxidizable and refractory components of mixture to form a refractory mass by projection reactive which, at working temperature, in particular at 1200 ° C, has a relative expansion difference overall compared to that of the prefabricated element less than 0.5%, and in particular for repairs or reconstructions extending over at least 2 meters, less than 0.3%, good compatibility is obtained with the prefabricated elements defined above, which ensures perfect adhesion of this mass as well to the old masonry of the wall to be repaired than the prefabricated elements on which it is applied on the thermal chamber side.

The attachment between the coherent mass projected refractory and the prefabricated elements is further favored by providing, on the latter, on the side of the heat treatment chamber, means for producing mechanical attachment between it and the mass projected refractory.

The prefabricated element suitable for carrying out the following process the invention, as shown in the figures, in particular in Figures 1 and 2, is formed from a prismatic block rectangular 1, the side 2 of which is intended to be directed to the heat treatment chamber is provided with means for producing, in addition to the ceramic bond obtained by reactive projection, mechanical locking with the refractory mass applied to this face 2. In this particular embodiment these means are formed by a mortise-shaped notch 3 extending parallel to the longitudinal edges of this block over the entire the length of the latter and substantially in the middle of its side 2.

In addition, this block advantageously has at its upper 4, lower 5 and lateral 6 and 7 faces, corresponding fitting means, so that allow precise and stable dry stacking of several blocks 1 on top of each other. As shown to Figures 1 to 3, these interlocking means are: on the faces lower 5 and lateral 7, a groove 8 extending also over the entire length of these faces and, at the faces upper 4 and side 6 opposite, a rib corresponding 9 can engage in a groove 8 of a stacked block.

Examples are given below concrete of realization allowing to illustrate more the subject of the invention.

Example 1

This example concerns the repair of a partition wall between flues and a room thermal coke ovens as shown schematically to Figure 4 attached.

The damaged area of the wall to be repaired was first cleaned to clear the parts healthy of its structure.

The wall to be repaired had a 11 cm total thickness, while the thickness of the blocks 1 was 5 cm.

Repair or reconstruction proper started with the face on the side of the flue 10. Prefabricated blocks 1, as shown in Figures 1 and 2, having an alumina content of the order of 50%, were laid dry on top of each other so that the rib of a determined block engaged in the groove of an adjacent block superimposed.

Once the building in mullitic blocks erected, the junction between the new masonry, formed by these blocks 1, and the old masonry 11 of the wall as well as the covering of the face 2 of the blocks directed towards the heat treatment chamber 12 were produced by reactive spraying in an oxygen stream containing 13% by weight of Si with an average diameter of 20 μm, 12% by weight of CaO ₂ with an average diameter of 10 μm and 75% of SiO ₂ , in the form of tridymite and cristobalite with an average diameter of 300 µm.

This reactive projection was continued until the total thickness of the area repaired wall had the same thickness as the wall to be repaired.

Thanks to good impact resistance thermal of the mullitic blocks 1, according to the invention, these could be brought directly from the temperature ambient at the place of installation.

The repaired area, which restored the profile and the thickness of the old masonry 11, was therefore consisting of masonry 13 of mullitic nature on the side flue 10 and a siliceous refractory layer 14 formed by reactive projection, firmly linked to blocks 1 by ceramic bond and mechanical anchoring in notches 3 on the side of the heat treatment chamber.

Figure 4, which is a section partial horizontal, shows a variant of this example 1 and concerns the partial reconstruction of a flue 10.

This variant stands out somewhat compared to the example shown in Figure 3 by the fact that a connection must be made between the repaired area and the transverse walls 15 of the flue 10.

To do this, we cut blocks 1 to dimension and bevel so that you can form where the transverse walls meet the wall separation with heat treatment chamber 12 a slot 16 with inclined edges in which the mass refractory 14 formed by reactive projection can easily inserted to link the walls transverse to the above-mentioned partition wall, and in particular to blocks 1 used for repairing this last.

Example 2

This example mainly concerns the repair of large areas of an exchange wall of heat between flues and a treatment chamber thermal. It can therefore be the illustrated case as well by FIG. 3 than that illustrated by FIG. 4.

Since repair block 1, for example for a coke oven, must both resist thermal shock during installation and move closer to the expansion plan, masonry behavior original 11 in silica bricks and that of the layer refractory 14 formed by reactive projection, it has been found, in a rather unforeseen way, as already indicated above, that a block 1 of mullitic nature represents a interesting compromise to satisfy these two requirements antagonistic.

However, when the length of the area to repair is important (several meters) a variant of the invention consists in using a mixture of repair to be projected, in which one has replaced, within of the refractory charge, part of the silica crystallized (cristobalite and tridymite) by a fraction of vitreous silica, the particle size of which is included between 100 and 500 µm and preferably between 200 and 400 µm.

The graph shown in Figure 5 gives different expansion curves of the products involved in repair and hot reconstruction industrial facilities.

Thus, curve A relates to the expansion in% as a function of the temperature of a crystallized silica brick, curve B relates to the refractory mass 14 obtained by reactive spraying of a mixture corresponding to the formulation given in Example 1, curve C is that of the mullitic block 1, curve D is that of a glassy silica brick and, finally, curve B 'is that of a refractory mass obtained by reactive projection of a mixture corresponding to the following formulation : Components Weight (%) Average particle diameter (µm) Yes 13 20 CaO ₂ 12 10 SiO ₂ crystallized (Tridymite + cristobalite) 50 300 Glassy SiO ₂ 25 300

This set of expansion curves shows that curves A and B practically coincide by so we can expect the repair to be of silica bricks, on which we form a refractory mass obtained from the above-mentioned mixture free of vitreous silica, will not present any problem of dilation point of view.

On the other hand, if we consider the curves B and C we see that there is a relatively important between these two curves.

However, it was found that the invention, and as moreover results from example 1, that despite this gap, in an entirely unpredictable way, practical tests have shown that there is a perfect compatibility between the two products concerned for conventional repairs and reconstructions envisaged.

If we consider, finally, the curve B ', it is found that the addition of vitreous silica to the mixture at projecting significantly reduces the gap between curve C of the mullitic block and curve B 'relating to projected mixture.

Therefore, the benefit of this addition is to reduce the mechanical stresses, to the working temperature, which may result from a disagreement thermal over a long interface, without this addition has a negative influence on mechanical properties of the repaired area.

It is understood that the invention is not not limited to particular embodiments of concrete examples but that other variants may be envisaged in the context of the invention, both in this which concerns the shape and dimensions of the blocks mullitics and the means to achieve mechanical anchoring possible refractory mass projected 14 on side 2 of these blocks. Thus, the mortise-shaped notch 3 does not for example not necessarily extend to the edges longitudinal of side 2 but could for example extend obliquely or perpendicularly to these edges. So instead of forming continuous grooves across the entire length of the repaired area, the 3 notches in the assembled blocks could form interrupted grooves.

The same is true for the mixture of particles intended to form, by reactive projection, the refractory mass 14 on the face 2 of blocks 1, which could vary within wide limits.

Indeed, both the chemical nature and particle physics entering this mixture that the relative report of the quantities used for each of the components of this mixture may vary within limits relatively wide as long as care is taken to avoid this projected refractory mass can by reaction chemical degrade blocks 1 and that total expansion of this mass and blocks at working temperature does could cause the refractory mass to drop out blocks 1. The allowable difference between these expansions largely depends on the surface to be repaired. So, for relatively small areas a larger gap it is accepted that when the surface to be repaired is relatively large where it is necessary to ensure that the dilations are as close as possible to each other. Finally, the prefabricated element 1 may have a hole, of preferably of rectangular section, facilitating the manipulation of the element during its installation.

Claims (11)

1. Process for hot repair of industrial installations comprising a structure made of refractory materials (11) of siliceous nature, in particular installations operating by indirect heating by means of flues (10), such as coke furnace batteries, according to which use is made of at least one prefabricated element (1) made of refractory materials which are joined to said structure (11) by projecting a current of carrier gas containing oxygen, a mixture of refractory particles and particles which can react exothermically with oxygen, which are selected, on the one hand, from the group consisting of Al, Si, Mg, Ca, Fe, Cr, Zr, Sr, Ba and Ti, and, on the other hand, from compounds of these metals which can form, by decomposition, with the oxides obtained from these metals, mixed oxides, so as to constitute a binding phase for the aforesaid particles of refractory material, thus permitting a coherent refractory mass (14) to be formed in situ, fixing the aforesaid element to the structure made of refractory materials and being formed by at least one of the oxides chosen from group comprising Si0₂, Al₂O₃, ZrO₂, MgO, Cr₂O₃, TiO₂ and CaO, characterised in that said process uses, on the one hand, a prefabricated element (1) made from a refractory material with mullitic crystallisation and having an alumina content of between 30 and 85%, and preferably between 50 and 80%, and, on the other hand, a mixture of particles which can react exothermically with oxygen, and of particles of a refractory material whose composition is such as to form in situ a refractory mass (14) which is compatible with the composition and the coefficient of thermal expansion of the aforesaid element (1) and structure (11) to which said mass (14) is to be fixed, taking account of the stresses to which said mass will be submitted under working conditions.
2. Process according to claim 1, characterised in that the aforesaid prefabricated element (1) is joined to the structure made of refractory materials which are siliceous in nature, by projection of a mixture formed on one hand of particles of Si which can react exothermically with the oxygen, and, on the other hand, of refractory particles containing (possibly) silica and at least one of the aforesaid compounds, which can, by decomposition, form with the silica mixed oxides, so as to constitute the aforesaid binding phase.
3. Process according to claim 2, characterised in that for the compounds of the metals mentioned above use is made of at least one of the peroxides in the group formed by CaO₂, MgO₂, BaO₂, SrO₂ and/or the salts of these metals, such as AlCl₃, SiCl₄ or MgCl₂.
4. Process according to any of claims 1 to 3, characterised in that, when the aforesaid structure is essentially made of siliceous refractory, use is made of a mixture of oxidisable and refractory particles which can form a coherent mass of refractory which is also essentially siliceous.
5. Process according to any of claims 1 to 4, characterised in that use is made of a mixture of refractory and oxidisable particles, which, when projected using a current of carrier gas makes it possible to form a coherent refractory mass with a total expansion difference of less than 0.5% at 1200 °C relative to that of the prefabricated element, and of less than 0.3% for repairs or reconstructions extending over at least 2 m in particular.
6. Process according to any of claims 1 to 5, characterised in that, for installations comprising heat treatment chambers (12) heated by means of flues (10), the aforesaid prefabricated element (1) is placed on the side of said flues and said coherent refractory mass (14) is applied on the heat treatment chamber side.
7. Process according to claim 6, characterised in that the refractory mass (14) is applied in the form of, on the one hand, a sealing and bonding joint between the prefabricated element (1) and the aforesaid structure (11), and, on the other hand, a coating which covers said prefabricated element on the heat treatment chamber side (12).
8. Process according to claim 7, characterised in that use is made of a prefabricated element (1) with, on the heat treatment chamber side (12), means (3) for forming a mechanical bound between said element (1) and the aforesaid refractory mass (14).
9. Process according to claim 8, characterised in that said means comprise at least one notch (3), essentially in the form of a mortise.
10. Process according to any of claims 1 to 9, characterised in that, when use is made of several superimposed prefabricated elements (1), said elements have means (8, 9) for fitting into one another on their contact faces (4, 5).
11. Process according to any of claims 7 to 10, characterised in that, by means of the aforesaid prefabricated element (1) and the coating formed of the aforesaid refractory mass (14), a wall or portion of wall is created with all or at least half the thickness being formed by said prefabricated element (1), with the other part of this thickness being formed by the aforesaid coating (14) covering said element (1) on the heat treatment chamber side.

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