Body of a process furnace

Abstract

A body of a process furnace for reforming, steam boilers and heating up starting materials is made of steel and comprises an internal lining inside the body and an outer coating outside the body. The outer coating is discrete, structurally heterogeneous and presents a mixture of water (from 60 to 30 vol. %) and polymers with fillers (from 40 to 70 vol. %). Used as the fillers are expanded perlite or microspheres. The thickness of the outer coating is from 0.4 to 2.0 mm. Technical results of the structure is lowering heat loss from the body.

Claims

1. A body of a process furnace for reforming, steam boilers and heating up starting materials, the body being made of steel and comprising an internal lining inside the body and an outer coating outside the body, the outer coating being discrete, structurally heterogeneous and comprising a mixture of water (from 60 to 30 vol. %) and polymers with fillers (from 40 to 70 vol. %), thus lowering heat loss from the body.

2. The body per claim 1, wherein the fillers include expanded perlite.

3. The body per claim 1, wherein the fillers include microspheres.

4. The body per claim 1, wherein thickness of the outer coating is from 0.4 to 2.0 mm.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0034] Details, features and advantages of the present invention will be explained in the ensuing description of the embodiments thereof and accompanying drawings, in which:

[0035] FIG. 1 illustrates an example of an enclosure structure of the body of the process furnace for heating up starting materials;

[0036] FIG. 2 shows an example of an enclosure structure of the body of the process furnace for primary crude oil processing;

[0037] FIG. 3 depicts an example of an enclosure structure of the body of the process furnace for heating up starting materials with an additional protective coating; and

[0038] FIG. 4 reflects an example of an enclosure structure of the body of the process furnace for primary crude oil processing with an additional protective coating.

[0039] Denoted in the drawings are the following positions: 1—a body of the furnace; 2—an outside frame; 3—an integrated structure of the internal lining and thermal; 4—an outer coating of the body and frame of the furnace with a discrete composition, heterogeneous by the structure thereof, the composition having thickness of no more than 2.0 mm and comprising, for example, water and a mixture of acrylic polymers and fillers dispersed therein and comprising 40-70% of the volume of the whole composition.

DETAILED DESCRIPTION

[0040] The technical solution relates to the body of process furnaces and can be used at the metallurgic, chemical and petroleum refining facilities for energy usage reduction and enhancement of the personnel's safety, as well as for additional protection of the process furnace metallic frame from unfavorable environment factors. Designs of the process furnace known in the art conduce, to a degree, and mainly due to the use of internal lining, the lowering of heat transfer from the body of process furnace. However, as it follows from the analysis of the prior art, the problem of decreasing the fuel consumption to compensate for the heat loss from the body has not yet been solved. Increasing the thickness of the furnace lining results in either decreasing the internal space of the furnace leading to the reduction of the output thereof, or in the increase of outer dimensions of the furnace resulting in the increase of the cost of the process furnace.

[0041] In the proposed invention, a discrete composition, heterogeneous by the structure thereof and no more than 2.0 mm in thickness, is applied to an outside surface of the enclosure structure (the process furnace body), the composition lowering radiation heat loss while being transparent for heat monitoring of the body. This composition though applied to the outside surface of the process furnace body is not a thermoprotective coating and does not perform functions thereof.

[0042] Cited as examples of such discrete compositions can be compounds comprising water and a mixture of acrylic polymers and fillers dispersed therein and making from 40 to 70% of the whole composition, or a mixture of latexes and expanded perlites dispersed therein (from 40 to 70% of the whole composition), or a mixture of latexes and microspheres dispersed therein (from 40 to 70% of the whole composition).

[0043] Developed at the surface of the body after the polymerization of the compound is a layer of a discrete, heterogeneous coating possessing, as compared with the materials of the process furnace body and frame, lower heat transfer and heat conductivity.

[0044] The minimal thickness of the coating is limited by the spreading capacity of the composition of the coating. For example, for compositions using microspheres as a filler, the spreading capacity is no less than 0.2 mm, whereas it is no less than 0.4 mm for those using expanded perlite as a filler. Maximal thickness of the coating, namely 2.0 mm, is limited by fire safety regulations for particularly hazardous facilities.

[0045] Where the mixture is less than 40% of the whole composition, discrete properties of the coating surface sharply deteriorate. In case it is more than 70%, linear stretching of the finished coating decreases, thus lowering service time of the coating.

[0046] It is only where the quantity of the polymers and fillers is between 40 and 70% that the heat transfer from the surface of the material decreases. Formed is a discrete surface rather than the entire one. The discrete structure of the material has lower heat transfer and conductivity as compared with the entire one. At the same time, the above-identified thickness of the coating prevents the process furnace body metal from overheating and does not get in the way of controlling the condition of the body visually. Also, fire safety requirements with regard to the process furnace structure are met herewith as well.

[0047] FIG. 1 exemplifies the process furnace structure for heating up starting materials.

[0048] The enclosure structure of this process furnace comprises a layer of internal lining of fire-brick protected from inside by a thermostable filler. There is also an integrated structure of a steel casing of the body and frame. The steel casing of the body and frame is covered with an antirust compound and a protective enamel. Brands and technical characteristics of the materials used for the process furnace, which depend on the process furnace operation condition requirements, vendor capacity, and the cost of the materials used, have no impact on the proposed design.

[0049] FIG. 2 shows an example of the process furnace structure used for primary crude oil processing.

[0050] The enclosure structure of this process furnace comprises a layer of internal lining of mineral wool mats protected from inside by a thermostable filler and layers of thermal from mineral wool boards. There is also an integrated structure of a steel casing of the body and frame. The steel casing of the body and frame is covered with an antirust compound and a protective enamel. Brands and technical characteristics of the materials used for the process furnace, which depend on the process furnace operation condition requirements, vendor capacity, and the cost of the materials used, have no impact on the proposed design.

[0051] In both above examples, the end element is the steel casing. It is known that steel has high value of heat transfer, and protection paint does not decrease the value of heat transfer.

[0052] Heat transfer coefficient is a value characterizing the rate of heat dissipation, and it is defined by the ratio of the current of heat released by a surface to the temperature difference between this surface and adjacent environment. A design heat transfer coefficient, according to the Building code (CNR (Construction Norms and Rules) 2.04.14-88, as applied, appendix 9) is equal to 35 W/m.sup.2° C.

[0053] An open metallic (or brick or concrete) surface possesses high value of the heat transfer coefficient which is due to physical properties of the materials used for the process furnace body. The object of the proposed design is to change physical structure of the outer heat dissipating surface that would result in decreasing heat transfer therefrom. In doing so, the possibility of visual monitoring of the process furnace body surface condition should be kept, and the overheating of the body should be avoided.

[0054] Generally, the enclosure structure comprises three basic elements—a body, a frame securing the integrity of the body, and an internal lining (potentially with thermal elements). In some cases, a strengthened design of the lining, such as in open-hearth furnaces, serves as the body and frame as well.

[0055] Unlike the traditional body structure comprising the internal lining (thermal) and body with frame, the proposed process furnace enclosure structure comprises four elements: a body 1, a frame 2, an aggregate 3 of internal lining and thermal, and an outer protective coating 4, no more than 2.0 mm in thickness, formed by a discrete composition, heterogeneous by structure thereof, such as water and a mixture of acrylic polymers and fillers dispersed in water and containing from 40 to 70% of the total volume of the composition.

[0056] Examples of these compositions are water and a mixture of acrylic polymers and fillers dispersed therein and containing from 40 to 70% of the total volume of the composition; or water and a mixture of latexes and expanded perlite (the mixture containing from 40 to 70% of the total volume of the composition) dispersed therein; or water and a mixture of latexes and microspheres (from 40 to 70% of the total volume of the composition) dispersed therein.

[0057] Due to lower, as compared with that of the material of the process furnace body, heat transfer and heat conductivity of the additional coating of the enclosure structure of the process furnace, heat loss from the body and frame of the process furnace into the atmosphere decreases.

[0058] Thus, the proposed design results in lowering fuel consumption to compensate for the heat loss from the process furnace body into surrounding air.

[0059] The maximal thickness of the protective coating, equal to 2 mm, is limited by the necessity to assure visual monitoring of the condition of the process furnace surface.

[0060] The limiting of the volume of the polymers and filler used in the protective coating to 40-70% of the total volume results from the finding that if their volume is less than 40%, the decrease of the heat transfer from surface is insufficient and does not outweigh the prior expenses, whereas where the volume of the mixture of polymers and filler is more than 70% of the total volume, the capacity of the protective coating to linear stretching decreases, resulting in the destruction of such coating after the furnace shutdown.

[0061] A mixture of butadiene-styrene latex, acrylic polymers, ammonia, and water with a mixture of such fillers as expanded perlite, quartz, zinc oxide and titanium dioxide can serve an example of the composition of the protective coating according to the proposed design.

[0062] Weight percentage of a solvent (water) is 47%, weight percentage of nonvolatile substances is 53%, the latter comprising 28% of polymeric components and 25% of noncombustible inorganic components, the nonvolatile inorganic components comprising 25% of silicon oxide, 28% of titanium oxide, 19% of calcium oxide, 20% of zinc oxide, 5% of potassium oxide, and 3% of ferrous oxide.

[0063] It was established as a result of the research of the characteristics of the protective coating of the above-identified composition that the density of the coating is 410 kg/m.sup.3; specific heat capacity is 1.120 kJ/kg ° C.; the coefficient of heat transfer is 2.0-3.0 W/m.sup.2° C.; coating combustibility—CC1.

[0064] For comparison, the coefficient of heat transfer from a metallic surface to surrounding air, according to the Building code (CNR 2.04.14-88, as applied, appendix 9) is equal to 35 W/m.sup.2.Math.° C.

[0065] Compared below are two variants of calculation of heat loss from the process furnace body—without the protective coating and with the same.

[0066] Variant 1 with no protective coating (FIG. 1).

[0067] Heat transfer resistance where

[00001]$R=\frac{1}{\alpha 1}+\frac{\delta }{\lambda }+\frac{1}{\alpha 2},$

α1—heat absorption coefficient—50 W/m.sup.2° C.
δ—thickness of the enclosure structure—0.2 m
λ—average heat conductivity coefficient for the whole enclosure structure—1.0 W/m.sup.2° C.
α2—coefficient of heat transfer from the surface—35 W/m.sup.2° C.
R—design resistance to heat transfer—0.25 m.sup.2° C./W.

[0068] Heat loss from the structure under consideration where

[00002]$-q=\frac{t-t3}{R},$

t—ambient temperature inside the furnace—800° C.
t3—temperature of surrounding air—0° C.
q—design heat loss—3144 W/m.sup.2.

[0069] Variant 2 with protective coating (FIG. 3).

[0070] Note: to simplify the comparable estimation, the change of thickness of the enclosure structure and of the heat conductivity resulting from applying the protective coating is not taken into account.

[0071] Heat transfer resistance where

[00003]$R=\frac{1}{\alpha 1}+\frac{\delta }{\lambda }+\frac{1}{\alpha 2},$

α1—heat absorption coefficient—50 W/m.sup.2° C.
δ—thickness of the enclosure structure—0.2 m
λ—average heat conductivity coefficient for the whole enclosure structure—1.0 W/m.sup.2° C.
α2—coefficient of heat transfer from the surface—3.0 W/m.sup.2° C.
R—design resistance to heat transfer—0.55 m.sup.2° C./W.

[0072] Heat loss from the structure under consideration where

[00004]$-q=\frac{t-t3}{R},$

t—ambient temperature inside the furnace—800° C.
t3—temperature of surrounding air—0° C.
q—design heat loss—1446 W/m.sup.2.

[0073] The change of heat transfer of the enclosure structure of the process furnace according to the present invention makes it possible to have heat loss from the process furnace body 2.2 times lower.