SE1851441A1

SE1851441A1 - Method for curing a form-supported refractory coating of an intermediate vessel

Info

Publication number: SE1851441A1
Application number: SE1851441A
Authority: SE
Inventors: Kyösti Ruotanen; Markku Miettinen
Original assignee: Bet Ker Oy
Priority date: 2016-04-25
Filing date: 2017-04-20
Publication date: 2018-11-21
Also published as: FI20165356A; SE543183C2; WO2017187013A1; FI127578B

Abstract

The invention relates to a method for curing a form-supported refractory coating of an intermediate vessel. The method comprises mounting a form inside the intermediate vessel, dosing a refractory coating mass essentially in dry existence to the space between an inner surface of the intermediate vessel and an outer surface of the form and applying microwave energy to the refractory coating mass in order to stabilize the mass and bound it to the inner surface of the intermediate vessel.

Description

Method for curing a form-supported refractory coating of an intermediatevessel Technical field of the invention The invention relates to curing a form-supported refractory coating of an interme-diate vessel. Specifically, the invention relates to a method curing a refractorycoating of an intermediate vessel with microwave energy.

Background of the invention Varying types of intermediate vessels are used for transferring and containing mol-ten metal. Such intermediate vessels, also known as tundishes or dummy basins,require an inner surface layer that is a refractory coating, which is bound to a morepermanent back-up lining.

Different methods for curing a form-supported refractory coating of an intermediatevessel are known. ln these methods a mould or a form is mounted inside the in-termediate vessel so that an inner surface of the intermediate vessel and an outersurface of the form are opposite to each other and a space is left between the twosurfaces for applying refractory coating material. ln the known methods the form isheated by using flame or electrical heating elements or by blowing hot air into acavity of the inner form. Superheated steam and infrared radiators may be utilizedfor heating the inner form as well. ln these solutions air inside the cavity of theform is heated and the heated air in turn heats the structure of the form.

EP1622848 describes a method that applies the heat from back-up lining, eitherthe dense refractory castable or brick lining behind the coating layer, without anyexternal heating devices. The form is typically composed of steel. From the heatedstructure of the form the heat further transfers to a refractory coating materialdosed to the space between the inner surface of the intermediate vessel and outersurface of the form. The heat cures the refractory coating material after which theform can be removed.

These known methods based on heating the form have certain disadvantages andlimitations. The known methods require relatively high temperatures for the air in-side the cavity of the form. Commonly temperatures over 300°C are required foreffective curing process, which requires significant amount of energy. Most of the known methods except the one according to EP1622848 are most effective whenthe back-up lining of the intermediate vessel is relatively cool (less than approxi-mately 150 °C of temperature). The known methods based on heating the formlack capability to control the conduction of the heat to a certain spot or target.

Also methods based on applying earth-moist refractory coating mix to the surfaceof backup lining are known. ln these solutions the refractory coating mass ismounted to the inner surface of the intermediate vessel by using a screw-typemixer and a form made of metal. Resins and curing agents are added to the drymix refractory coating mass base in solution form, to compose an earth-moistcoating mix. ln some cases citric acid alone is used as the binder. This causes theearth-moist refractory coating mass to bind also to a relatively cold (under 10 °C oftemperature) inner surface of the intermediate vessel and no heating of the form isneeded. This type of binder solutions are also applied in foundries for manufactur-ing sand forms and cores.

Using dry or earth-moist installed refractory coating masses often require vibratingor rodding for reaching suitable and acceptable thermomechanical strength for thecoaüng.

Further, EP1622848 describes a coating mass, a dry matter composition and amethod for applying a coatings mass onto a relatively cold (under 10 °C of tem-perature) backup lining surface. This resolution requires also a screw-type mixerand curing time after which the form can be removed is relatively long, approxi-mately 30 minutes.

Also these solutions have certain disadvantages. First of all, the screw-type mixersare expensive tools and cause high investment and maintenance cost. Further,resins or curing agents applied to dry mix refractory coating masses can be harm-ful for both environment and health wise. Finally, vibrating dry installed refractorycoating masses requires vibrating motors attached onto the form as well as con-necting electrical cables to the form, causes increased noise level and weakensheat insulation.

Microwave technique can be applied to heating a variety of materials and pro-cessing materials. The microwave technique has been used in several differentapplications from heating food in a microwave oven to sintering foundry sandforms and cores, and water evaporation (dry-out) of aqueous refractory castables.

Microwave technology is replacing some of the traditional heating technology thatis based on bringing heat to a surface of the object to be heated and the thermalconductance based heat transfer phenomena is then responsible for transferringthe heat into the inner parts of the object. A fundamental feature of the microwaveradiation is that certain suitable materials can be warmed with microwave radiationor heated so that the heat is generated at the same time in the whole volume ofthe object (so called volumetric heating). Thus, the heating energy will be usedmore effectively than in conduction based heating.

Summary of the lnvention The object of the present invention is to provide an energy-efficient solution forcuring a refractory coating of an intermediate vessel.

Also, the object of the present invention is to provide a solution for curing the re-fractory coating of the intermediate vessel when a temperature of an inner surfaceof the intermediate vessel, so called back-up lining or permanent lining, is relative-ly cold. Relatively cold can be understood as a temperature range under 150 °C inthe context of the present invention. Relatively cold can also be understood as atemperature range from 100°C to 150 °C in the context of the present invention.

Further, the object of the present invention is to provide an environment-friendlysolution for curing the refractory coating of the intermediate vessel.

Moreover, the object of the present invention is to provide a solution for curing therefractory coating of the intermediate vessel that reduces the need to use sub-stances harmful for human and environment during or after the curing of the re-fractory coating.

Finally, the object of the present invention is to provide a solution for curing the re-fractory coating of the vessel that fastens the rotation of intermediate vessels andforms necessary for assembling the refractory coating in their process of use.

The objects of the present invention are fulfilled by providing a method for curing aform-supported refractory coating of an intermediate vessel, the method compris-ing- mounting a form comprising at least an outer surface and an inner surface,inside the intermediate vessel comprising an inner surface and an outer sur- face so that the inner surface of the intermediate vessel and the outer surfaceof the form are positioned opposite to each other and a space is left betweenthe inner surface of the intermediate vessel and the outer surface of the saidform; and - dosing a refractory coating mass essentially in dry existence to the spacebetween the inner surface of the intermediate vessel and the outer surface ofthe form, wherein the method further comprises applying microwave energy to thedosed refractory coating mass and removing the form after applying micro-wave energy to the refractory coating mass.

Some advantageous embodiments of the present invention are disclosed in de-pendent claims.

The basic idea of the invention is as follows: An intermediate vessel comprises aninner surface and an outer surface. To enable handling of hot materials such asmolten metal inside intermediate vessel, the inner surface of the back-up lining, in-stalled into the intermediate vessel, requires an insulating refractory coating massto be assembled onto it with the aid of a form. Varying compositions of form-supported refractory coating masses exist. The form or mold is mounted inside theintermediate vessel so that the outer surface of the form and the inner surface ofthe intermediate vessel are positioned opposite to each other and a space is leftbetween the inner surface of the intermediate vessel and the outer surface of theform. The refractory coating mass is dosed to the space between the inner surfaceof the intermediate vessel and the outer surface of the form. To cure and hardenthe refractory coating mass so that it also bounds to the inner surface of the inter-mediate vessel, microwave energy is applied, thus enabling heating of the coating.Heating the refractory coating mass with microwave energy causes the refractorycoating mass to stabilize into a suitable coherence and is being bound to the innersurface of the intermediate vessel. ln one advantageous embodiment of the invention the temperature of the innersurface of the intermediate vessel is between 10 °C and 100 °C when applying themicrowave energy. ln the context of the present invention the previous tempera-ture range can be considered cold. ln another advantageous embodiment of the invention the temperature of the innersurface of the intermediate vessel is less than 150°C when applying the micro- wave energy. ln the context of the present invention such temperature range canbe considered relatively cold. However, the present invention may be applied tothe intermediate vessels in cases where the temperature of the inner surface isover 150°C. Also, the present invention may be applied to the intermediate vesselsin cases where the temperature of the inner surface is between 10°C and 200 °C.lf the temperature of the inner surface is less than 100°C, more microwave energyis necessary for curing refractory coating mass. ln the third advantageous embodiment of the invention the form is comprised of amicrowave transparent material. Also, the form may comprise one or more isola-tion structures to prevent spreading of microwave radiation outside the target(while microwave energy is applied to cure the refractory coating mass). Further,the form may comprise a support structure that also guides the microwave radia-tion. ln the fourth advantageous embodiment of the invention the form is comprised ofmaterial acting as a susceptor. The material of form may be, for exemplary pur-poses only, silicon inﬁltrated silicon carbide. ln the fifth advantageous embodiment of the invention the form is comprised of amicrowave transparent material and the mix material or some of its componentsacting as a susceptor. ln the sixth advantageous embodiment of the invention the refractory coating massis dosed in granular form. The refractory coating mass may be relatively dry massby its composition while it is applied to the surface of back-up lining. Relatively drymeans hereby that the coating mix does not contain water in liquid existence justprior to applying onto back-up lining, but, may contain a tiny amount of dust sup-pressants that are composed of hydrocarbons in liquid form. Further, one or moresusceptor substances may be added to the refractory coating mass for boostingheat production. One or more susceptor substances may be added to the refracto-ry coating mass for boosting heat production under microwave radiation. Suchsusceptor substances comprise at least one of the following: essentially hydrouschloride, sulfate, phosphate and carbonate salts of Mg, Ca, Na and K, hydroxides,essentially earth-alkali and iron hydroxides, hydrous natural or man-made miner-als, graphite, metal powders, essentially fine aluminum powder, essentially fineferrous powder, iron-bearing spinel powders, essentially magnetite powder, sug-ars, resins, phenolic resin, starch derivative substances and Silicon carbide.

Further scope of applicability of the present invention will become apparent fromthe detailed description given hereafter. However, it should be understood that thedetailed description and specific examples, while indicating preferred embodi-ments of the invention, are given by way of illustration only, since various changesand modifications within the spirit and scope of the invention will become apparentto those skilled in the art from this detailed description.

Brief description of the drawingsThe present invention will become fully understood from the detailed description given herein below and accompanying drawings which are given by way of illustra-tion only, and thus are not limitative of the present invention and wherein Fig. 1 shows an exemplary cross-sectional representation of an intermediatevessel and an inner form; andFig. 2 shows an exemplary flow chart representing main method steps ac- cording to the invention.

Detailed description ln the following description, considered embodiments are merely exemplary, andone skilled in the art may find other ways to implement the invention. Although thespecification may refer to “an”, “one; or “some” embodiment(s) in several locations,this does not necessarily mean that each such reference is made to the same em-bodiment(s), or that the feature only applies to a single embodiment. Single fea-ture of different embodiments may also be combined to provide other embodi-ments.

Figure 1 shows an exemplary cross-sectional representation of an intermediatevessel (10-11) and an inner form (13-15). An intermediate vessel (10-11) com-prises an inner surface (11) and an outer surface (10). To enable handling of hotmaterials such as molten metal with the intermediate vessel (10-1), the inner sur-face (11) of the intermediate vessel (10-11), also known as back-up lining, re-quires a refractory coating mass to be assembled onto it.

Assembling the refractory coating mass to the inner surface (11) of the intermedi-ate vessel (10-11) is assisted with a form (13-15). The form (13-15) comprises anouter surface (14). The form (13-15) may also comprise an outer surface (14) and an inner surface (13). The form (13-15) is mounted inside the intermediate vessel(10-11) so that the outer surface (14) of the form (13-15) and the inner surface(11) of the intermediate vessel (10-11) are positioned opposite to each other anda space (12) is left between the inner surface (11) of the intermediate vessel (10-11) and the outer surface (14) of the form (13-15). Suitable supporting structuresand/or tools may be used for mounting the form (13-15) inside the intermediatevessel (10-11). The thickness of the coating may vary between 30 and 120 mm,depending on the metallurgical process related.

Further, the form (13-15) can be comprised of a microwave transparent material.Advantageously, the form (13-15) may comprise one or more isolation structuresto prevent spreading of microwave radiation outside the target to which microwaveenergy is applied to cure the refractory coating mass for curing it. The form (13-15) may, more advantageously, also comprise a support structure (15) that alsoguides the microwave radiation.

More advantageously, the form can be comprised of material acting as a suscep-tor. The material of form may be, for exemplary purposes only, silicon infiltrated sil-icon carbide. The form (13-15) may comprise isolation to prevent spreading of mi-crowave radiation outside the target to which microwave energy is applied to curethe refractory coating mass for curing it. The form (13-15) may, more advanta-geously, also comprise a support structure (15) that also guides the microwave ra-diation.

Finally, the form (13-15) can be comprised of a microwave transparent material orthe form can be comprised of material acting as a susceptor. The form (13-15)may comprise isolation to prevent spreading of microwave radiation outside thetarget to which microwave energy is applied to cure the refractory coating mass forcuring it. The form (13-15) may, more advantageously, also comprise a supportstructure (15) that also guides the microwave radiation.

Figure 2 shows an exemplary flow chart representing main method steps accord-ing to the invention. References to elements of Figure 1 are made. Process forcuring a refractory coating of the intermediate vessel (10-11) is started in step 20.To enable handling of hot materials such as molten metal with the intermediatevessel (10-11), the inner surface (1 1) of the intermediate vessel (10-11), so calledback-up lining, requires a refractory coating mass to be assembled onto it. ln step 21 the form (13-15) is mounted inside the intermediate vessel (10-11) toenable assembling the refractory coating to the inner surface (11) of the interme-diate vessel (10-11). The form (13-15) is arranged inside the intermediate vessel(10-11) so that the inner surface (11) of the intermediate vessel (10-11) and theouter surface (14) of the form (13-15) are arranged opposite to each other. Theform (13-15) is arranged inside the intermediate vessel (10-11) so that the innersurface (11) of the intermediate vessel (10-11) and the outer surface (14) of theform (13-15) are arranged opposite to each other and a space (12) is left betweenthe inner surface (11) of the intermediate vessel (10-11) and the outer surface(14) of the form (13-15). ln step 22 the refractory coating mass is dosed to the space between the innersurface (11) of the intermediate vessel (10-11) and the outer surface (14) of theform (13-15). The refractory coating mass is dosed to the space between the in-ner surface (11) of the intermediate vessel (10-11) and the outer surface (14) ofthe form (13-15) in order to be bound to the inner surface (11) of the intermediatevessel (10-11) to form a layer of refractory coating for the intermediate vessel(10-11).

The composition of one or more binder substances of the refractory coating massmay be essentially inorganic. Also, the composition of one or more binder sub-stances of the refractory coating mass may be essentially organic. Further, thecomposition of one or more binder substances of the refractory coating mass maybe essentially organic or inorganic. Moreover, one or more susceptor substancesmay be added to the refractory coating mass for boosting heat production. Suchsusceptor substances comprise at least one of the following: essentially hydrouschloride, sulfate, phosphate and carbonate salts of Mg, Ca, Na and K, hydroxides,essentially earth-alkali and iron hydroxides, hydrous natural or man-made miner-als, graphite, metal powders, essentially fine aluminum powder, essentially fineferrous powder, iron-bearing spinel powders, essentially magnetite powder, sug-ars, resins, phenolic resin, starch derivative substances and Silicon carbide.

Advantageously, the refractory coating mass may be applied in granular existence.The refractory coating mass may be essentially dry mass by its composition. ln step 23, in order to cure the refractory coating mass so that it bounds to the in-ner surface (11) of the intermediate vessel (10-11), microwave energy is appliedto the dosed refractory coating mass. The dosed refractory coating mass is heated and cured with microwave energy in order to cure the refractory coating mass. Thedosed refractory coating mass is heated with microwave energy. Heating thedosed refractory coating mass with microwave energy causes the said refractorycoating mass to stabilize into a suitably firm coating and is being bound to the in-ner surface (11) of the intermediate vesse| (10-11). After the refractory coatingmass is stabilized into the suitably firm refractory coating and is bound to the innersurface (1 1) of the intermediate vesse| (10-11), the form (13-15) can be removed.

The temperature of the inner surface (11) of the intermediate vesse| (10-11) is,advantageously, between 10 °C and 100 °C when applying the microwave energyto it. ln the context of the present invention such temperature range can be con-sidered cold. However, the temperature of the inner surface (11) of the intermedi-ate vesse| (10-11) may be less than 150°C when applying the microwave energy.ln the context of the present invention such temperature range can be consideredrelatively cold. Further, the present invention may be applied to the intermediatevessels in cases where the temperature of the inner surface is over 150°C. Thismay shorten the time needed for curing the refractory coating. The temperature ofthe inner surface (11) of the intermediate vesse| (10-11) may even be between 10°C and 200 °C when applying the microwave energy. The colder the surface of theback-up lining, then the more microwave energy is necessary for curing the coat- ing.

Moreover, the form (13-15) is comprised of a microwave transparent material. Al-so, the form (13-15) may comprise an isolation structures to prevent spreading ofmicrowave radiation outside the target while microwave energy is applied to curethe refractory coating mass. The form (13-15) may also comprise a support struc-ture to guide the microwave radiation between the inner surface (11) of the inter-mediate vesse| (10-11) and the outer surface (14) of the form (13-15) while mi-crowave energy is applied to cure the refractory coating mass. The support struc-ture to guide the microwave radiation between the inner surface (11) of the inter-mediate vesse| (10-11) and the outer surface (14) of the form (13-15) may enablemore effective application of the microwave energy. The support structure to guidethe microwave radiation between the inner surface (11) of the intermediate vesse|(10-11) and the outer surface (14) of the form (13-15) may enable more effectiveapplication spreading of microwave radiation to the refractory coating mass. Thesupport structure to guide the microwave radiation between the inner surface (11)of the intermediate vesse| (10-11) and the outer surface (14) of the form (13-15) PCT/FI2017/0503021 O may enable more effective application spreading of microwave radiation to the re-fractory coating mass and fasten the curing of the refractory coating mass. ln step 24 the refractory coating mass is stabilized into the suitably firm refractorycoating and is bound to the inner surface (11) of the intermediate vesse| (10-11).The refractory coating mass is stabilized into the suitably ﬁrm refractory coatingand is bound to the inner surface (11) of the intermediate vesse| (10-11) after ap-plication microwave energy to the heat mass according to step 23. The form (13-15) can now be removed. The form (13-15) can be removed after applying micro-wave energy to the refractory coating mass. The form (13-15) can be removed af-ter applying microwave energy to the refractory coating mass when the refractorycoating mass is stabilized into the suitably firm refractory coating and is bound tothe inner surface (1 1) of the intermediate vesse| (10-11). ln step 25 the curing process is ﬁnished. The form (13-15) has been removed andthe intermediate vesse| (10-11) is ready to be used with the refractory coating.

Some exemplary test results regarding application of the method according to theinvention are herewith provided for varying types of refractory coating masses thatmay be used for intermediate vessels (10-11). The exemplary test results de-scribe type of refractory coating mass mix, amount of mix, main binder substanceused, applied efficiency, duration of heating with microwave energy and reachedCold Compressive Strength (CCS) after application of microwave energy to the re-fractory coating mass. These results have been obtained with the following set-upand equipment: Panasonic NN-SD microwave oven with rotating platform and fre-quency of 2,45 GHz and a small size sample form with outer surface made of plas-tic and inner surface made of silicone, featuring a miniature size intermediate ves-se| (10-11). Temperatures of inner parts for the said sample intermediate vesse|have been over 100°C while applying the microwave energy. The said inner partsin general comprise parts between the inner surface (11) and the outer surface(10) of the intermediate vesse|. Surface temperatures for the obtained refractorycoating between 80°C and 100°C after application of the microwave energy to therefractory coating mass in manner of step 23 were measured.

According to first example (“Example 1”) olivine-rich refractory coating mass that isapplied as a dry mix having composition comprising approximately 56 % of MgOand 1% of graphite is used. The amount of mix is 500 g, no compacting is appliedto the mass and the mix density as installed is approximately 1.7 g/cm3. The main PCT/FI2017/0503021 1 binder Substance is crystalline magnesium sulphate heptahydrate of 6 w-%. Ap-plied efficiency is 1000 W and duration of heating with microwave energy wasthree (3) minutes. CCS of 0.8 MPa is achieved after application of heating the de-scribed refractory coating mass of this Example 1 with microwave energy for three(3) minutes.

According to a second example (“Example 2") olivine-rich refractory coating massthat is applied as a dry mix having composition comprising approximately 56 % ofMgO and 1% of graphite is used. The amount of mix is 500 g, no compacting isapplied to the mass and the mix density as installed is approximately 1.7 g/cm3.The main binder substance is crystalline magnesium sulphate heptahydrate of 6w-%. Applied efficiency is 500 W and duration of heating with microwave energywas three (3) minutes. CCS of 0.4 MPa is achieved after application of heating thedescribed refractory coating mass of this Example 2 with microwave energy forthree (3) minutes.

According to a third example (“Example 3”) olivine-rich refractory coating massthat is applied as a dry mix having composition comprising approximately 56 % ofMgO. Further, graphite applied in Examples 1 and 2 is replaced with 200M MgO-powder in the dry mix. The amount of mix is 500 g, no compacting is applied to themass and the mix density as installed is approximately 1.7 g/cm3. The main bindersubstance is crystalline magnesium sulphate heptahydrate of 6 w-%. Applied effi-ciency is 1000 W and duration of heating with microwave energy was three (3)minutes. CCS of 0.5 MPa is achieved after application of heating the described re-fractory coating mass of this Example 3 with microwave energy for three (3)minutes.

According to a fourth example (“Example 4") olivine-rich refractory coating massthat is applied as a dry mix having composition comprising approximately 50 % ofMgO. The amount of mix is 500 g, no compacting is applied to the mass and themix density as installed is approximately 1.7 g/cm3. The main binder substance iscrystalline magnesium sulphate heptahydrate of 5 w-%. Applied efﬁciency is 1000W and duration of heating with microwave energy was seven (7) minutes. CCS of0.7 MPa is achieved after application of heating the described refractory coatingmass of this Example 4 with microwave energy for seven (7) minutes.

According to a fifth example (“Example 5") MgO-rich dry installed tun-dish dispos-able coating mix having composition comprising MgO-content of 82% is used as PCT/FI2017/0503021 2 refractory coating mass. The amount of mix is 500 g, no compacting is applied tothe mass and the mix density as installed is approximately 1.8 g/cm3. The mainbinder substance is epsom salt 5 w-% in crystal form. Applied efficiency is 1000 Wand duration of heating with microwave energy was eight (8) minutes. CCS of 0.8MPa is achieved after application of heating the described refractory coating massof this Example 5 with microwave energy for eight (8) minutes.

According to a sixth example (“Example 6”) MgO-rich dry installed tun-dish dis-posable coating mix having composition comprising MgO-content of 82% is usedas refractory coating mass. The amount of mix is 500 g, no compacting is appliedto the mass and the mix density as installed is approximately 1.8 g/cm3. The mainbinder substance is epsom salt 5 w-% in crystal form. As an additive 0.05% atom-ized aluminium powder is applied. Applied efficiency is 1000 W and duration ofheating with microwave energy was four (4) minutes. CCS of 0.8 MPa is achievedafter application of heating the described refractory coating mass of this Example5 with microwave energy for four (4) minutes.

According to a seventh example (“Example 7”) MgO-rich dry installed tun-dish dis-posable coating mix having composition comprising MgO-content of 82% is usedas refractory coating mass. The amount of mix is 500 g, no compacting is appliedto the mass and the mix density as installed is approximately 1.7 g/cm3. The mainbinder substance is phenolic resin of 4 w-%. Applied efficiency is 700 W and dura-tion of heating with microwave energy was eleven (11) minutes. CCS of 0.8 MPais achieved after application of heating the described refractory coating mass ofthis Example 7 with microwave energy for eleven (11) minutes. The measured sur-face temperature for the refractory coating is 80°C after application of heating thedescribed refractory coating mass of this Example 7 with microwave energy foreleven (11) minutes.

As becomes clear from the examples presented herewith, the CCS after applyingmicrowave energy is increased while the efficiency is increased. Further, as be-comes apparent from the examples presented herewith, the CCS after applyingmicrowave energy is increased while the radiation time is increased. Also, as be-comes clear from the examples presented herewith, the CCS after applying mi-crowave energy is increased while the efficiency and radiation time is increased.Furthermore, the acceptable CCS value is obtained in a shorter period of time ifadditional susceptors, like graphite or aluminum powder, for example, are appliedin the mix formula. At least 0.3 MPa CCS value is commonly adequate for ena- WO 2017/187013 PCT/FI2017/0503021 3 bling the form removal and the intermediate vessel's transport and preheatingtreatment prior to steel casting process in real steelmaking factory conditions.

Some advantageous embodiments according to the invention were describedabove. The invention is not limited to the embodiments described. The inventionalidea can be applied in numerous ways within the scope defined by the claims at-tached hereto.

Claims

WO 2017/187013 PCT/FI2017/0503021 4 Claims

1. A method for curing a form-supported refractory coating of an intermediatevessel (10-11), the method comprising - mounting (21) a form (13-15) comprising at least an outer surface (14) and aninner surface (13), inside the intermediate vessel (10-11) comprising an inner sur-face (11) and an outer surface (10) so that the inner surface of the intermediatevessel (11) and the outer surface of the form (14) are positioned opposite to eachother and a space (12) is left between the inner surface of the intermediate vessel(11) and the outer surface of the said form (14); and - dosing (22) a refractory coating mass essentially in dry existence to the space(12) between the inner surface of the intermediate vessel (11) and the outer sur-face of the form (14), characterized in that, the method further comprises applying microwave energy tothe dosed refractory coating mass (23) and removing the form (13-15) after apply-ing microwave energy to the said refractory coating mass (24).

2. The method according to claim 1, characterized in that a temperature of theinner surface of the intermediate vessel is between 10 °C and 200 °C when apply-ing the microwave energy.

3. The method according to claim 1, characterized in that the form (13-15) iscomprised of a microwave transparent material.

4. The method according to claim 1, characterized in that the form (13-15) iscomprised of material acting as a susceptor.

5. The method according to claim 1, characterized in that the form (13-15) iscomprised of a microwave transparent material and material acting as a susceptor.

6. The method according to claims 3, 4 or 5, characterized in that the form (13-15) further comprises one or more isolation structures to prevent spreading of mi-crowave radiation while microwave energy is applied.

7. The method according to claim 1, characterized in that the refractory coatingmass is in granular existence. WO 2017/187013 PCT/FI2017/050302

8. The method according to claim 1, characterized in that the method furthercomprises adding at least one susceptor substance boosting heat production tothe refractory coating mass by microwave energy.

9. The method according to claim 8, characterized in that the at least one sus-ceptor substance boosting heat production comprises at least one of the following:essentially hydrous chloride, sulfate, phosphate and carbonate salts of Mg, Ca, Naand K, hydroxides, essentially earth-alkali and iron hydroxides, hydrous natural orman-made minerals, graphite, metal powders, essentially ﬁne aluminum powder,essentially fine ferrous powder, iron-bearing spinel powders, essentially magnetitepowder, sugars, resins, phenolic resin, starch derivative substances and Siliconcarbide.