ES2566983B1 - Heat exchange condenser for smoke condensation - Google Patents

Abstract

Heat exchange condenser for smoke condensation. # The present invention relates to a heat exchange condenser comprising carbon steel tubes coated by a custom made enamel. In addition, the present invention relates to the use of the heat exchange condenser for smoke condensation, particularly for highly corrosive from, for example, thermal power plants, combustion engines, oil refineries, energy recovery plants, cement kilns and / or glass industries.

Description

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Heat exchange condenser for smoke condensation

DESCRIPTION

The present invention relates to a heat exchange condenser comprising carbon steel tubes coated by a custom made enamel. In addition, the present invention relates to the use of the heat exchange condenser for the condensation of fumes, particularly for highly corrosive fumes from, for example, thermal power plants, combustion engines, oil refineries, energy recovery plants, furnaces cement and / or glass industries.

STATE OF THE TECHNIQUE

Heat exchange condensers are those devices that convert a fluid into a gaseous state into a liquid state, transferring heat in the process. These condensers are mainly composed of a metal casing and metal tubes, the most common use case being that in which the cooling fluid circulates inside the tubes and the gaseous fluid circulates outside the tubes coming into contact with the housing These condensers can be designed based on multiple configurations in which elements such as fins or turbulators can be included that allow to enhance the efficiency of heat exchange.

In general, these types of heat exchange condensers are not suitable for the condensation of fumes from highly corrosive components. Few solutions can be found in the bibliography, which are economically expensive. In addition, the heat exchange efficiencies of the condensers are low and their useful life limited.

In the market you can find condensers with teflon tubes that are arranged inside a stainless steel housing. Teflon is a suitable material for corrosive environments both acidic and alkaline. However, the heat transfer in these teflon condensers is low and its use is discouraged for temperatures above 260 ° C, the temperature from which it decomposes.

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Therefore, it is necessary to develop new high efficiency heat exchange condensers that serve the different chemical environments that can be generated in the industry and are economically viable.

DESCRIPTION OF THE INVENTION

The heat exchange condenser of the present invention has as its main objective:

• recover the residual heat by heating the cooling liquid for, for example, the generation of electricity, such as domestic hot water, as a heat source for drying raw materials in the industry, etc.

• Clean highly corrosive fumes from thermal power plants, combustion engines, oil refineries, energy recovery plants, as well as cement kilns and glass industries avoiding environmental pollution.

• recover water after neutralizing condensate acids, for example for reuse in industrial processes.

The present invention relates to a heat exchange condenser of high efficiency and with a long service life comprising carbon steel tubes coated, on its inner face, by an enamel whose formulation is designed and manufactured to measure in function of the composition of fumes to condense, particularly highly corrosive fumes from different industrial sectors.

The condenser of the present invention can work effectively when the temperature of the fumes to be condensed is between -150 ° C and -175 ° C having to adjust the temperature of the refrigerant fluid to a lower value than desired, a value between 20 ° C and 30 ° C lower than the smoke condensation temperature. The condenser of the present invention can also work effectively when the temperature of the fumes to be condensed is between 700 ° C and 800 ° C, the temperature of the refrigerant fluid must also be adjusted for the correct operation of the condenser. Hence, an advantage of the capacitor of the invention is that it is

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valid for a wide range of smoke condensation temperatures, from -175 ° C to 800 ° C.

In a first aspect, the present invention relates to a heat exchange condenser characterized by

• comprising a set of pipes through which fumes circulate to condense;

• where the pipes are arranged inside a housing;

• where a cooling fluid circulates through the space between the housing and the tubes;

• and where each tube is made of carbon steel and is covered by its inner face, optionally by its outer face, by an enamel.

In the present invention, the condenser comprises a set of tubes where each tube is made of carbon steel, that is, it is a steel tube with a carbon percentage of between 0.003% and 1.4%. Preferably the carbon percentage is between 0.003% and 0.3%.

This carbon steel tube is covered by an enamel on its inner face. It is a continuous but not homogeneous coating. Due to the degassing of the substrate and internal reactions of the coating, during cooking with, for example the clays, said coating develops a characteristic amorphous structure of fine bubbles that, although it does not affect the chemical resistance of the same, contributes to the improvement of mechanical properties such as elasticity, resistance to impact breakage and scratch.

The enamel contains a percentage by weight in terms of the following equivalent oxides of:

• between 50% and 55% of SiO2,

• between 12.5% and 14% of Na2O,

• between 6% and 7% of K2O,

• between 14% and 15.5% of B2O3,

• between 5% and 8% of TiO2, and

• between 1% and 3% CoO.

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In a preferred embodiment, the enamel also contains additives selected from SiO2, CoO, TiO2 and a combination thereof, and wherein said enamel contains a weight percentage in terms of the following equivalent oxides:

• between 55% and 63.5% of SiO2,

• between 8.75% and 11.4% of Na2O,

• between 4.4% and 5.5% of K2O,

• between 10% and 12.7% of B2O3,

• between 4.5% and 11.25% of TiO2, and

• between 0.9% and 3.75% CoO.

Preferably the enamel has a thickness between 100 pm and 300 pm. More preferably the enamel has a thickness between 140 pm and 160 pm.

The heat exchange condenser of the present invention is characterized in that it has an inlet and outlet of a cooling fluid.

The heat exchange condenser of the present invention is characterized in that it has a smoke inlet and a smoke and condensate outlet.

In a preferred embodiment of the condenser of the invention, each carbon steel tube is coated both by its inner face and its outer face by the enamel described above, both without and with the additives selected from SiO2, TiO2, CoO and a combination thereof. This situation is ideal when not only are corrosive fumes, but also the cooling fluid is, for example when the cooling fluid is seawater, brackish water or water from some industrial discharge.

Another aspect of the invention relates to the use of the heat exchange condenser mentioned above for the condensation of fumes from any industry, for example from thermal power plants, combustion engines, oil refineries, energy recovery plants, as well as furnaces. of cement and glass industries.

In a preferred embodiment, the heat exchange condenser mentioned above, which comprises an enamel with additives selected from

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SiO2, TiO2, CoO and a combination thereof and with a term content of equivalent oxides of

• between 55% and 63.5% of SiO2,

• between 8.75% and 11.4% of Na2O,

• between 4.4% and 5.5% of K2O,

• between 10% and 12.7% of B2O3,

• between 4.5% and 11.25% of TiO2, and

• between 0.9% and 3.75% CoO.

It is used for condensation of highly corrosive fumes. In the present invention, "highly corrosive smoke" means smoke that comprises

• at least 6% of COx, where x = 1 or 2 or

• at least 37ppm of NOx, where x = 1 or 2 or

• at least 25 ppm SOx, where x = 2 or 3 or

• at least 25 ppm of HCl or

• a combination thereof.

Additives added to the base enamel are responsible for protecting carbon steel in these highly corrosive environments.

Throughout the description and the claims the word "comprises" and its variants are not intended to exclude other technical characteristics, additives, components or steps. For those skilled in the art, other objects, advantages and characteristics of the invention will be derived partly from the description and partly from the practice of the invention. The following examples and figures are provided by way of illustration, and are not intended to be limiting of the present invention.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 Longitudinal section of a tube of a heat exchange condenser with and without enamel.

FIG. 2 a) Scanning electron microscope images of the heat exchange condenser tube of Example 1; b) Enlargement of the scanning electron microscope image of a heat exchange condenser tube of Example 1, interface between the carbon steel substrate and the enamel;

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FIG. 3 Results of the profile of a heat exchange condenser tube of example 1; a) carbon steel substrate; b) enamel.

FIG. 4 Hardness test results of a heat exchange condenser tube of example 1.

FIG. 5 Heat exchange condenser comprising the following elements:

1. Housing

2. Smoke inlet

3. Smoke and condensate outlet

4. Moorings

5. Distributor

6. Tubes

7. Fitting: cooling fluid inlet and outlet

8. Deflector

EXAMPLES

The invention will now be illustrated by tests carried out by the inventors, which demonstrates the effectiveness of the tubular heat exchanger of the invention.

Example 1:

Preparation of a tube of a heat exchange condenser

It was split from a carbon steel tube with a carbon weight percentage of 0.12%. To ename the interior of the carbon steel tube, grinding is carried out in a ball mill of a borosilicate glass (60% - 61%) to which clay (3% - 3.7%) has been added ), silica (4% - 6%), borax (0.15%), sodium nitrite (0.15%) and water (30% -31.7%). A fluid and homogeneous paste is formed, called "slipper", which is screened until an average particle size of between 40 pm and 200 pm is obtained. This paste was deposited on the inner side of the steel tube using the technique called Flow-coating in English. Finally, the

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vitrification treatment of the set (paste applied on the carbon steel tube) and dried. The treatment consists of heating the assembly to temperatures above 700 ° C so that the enamel acquires its vitreous character.

As an example of realization, a composition of the enamel was prepared in terms of equivalent oxides of:

• 52.9% of SiO2,

• 13.2% of Na2O,

• 6.6% of K2O,

• 14.6% of B2O3,

• 7.5% TiO2, and

• 2.1% CoO.

and a density of 1.74 g / l.

Characterization of tubular heat exchanger

In order to characterize the prepared heat exchange condenser tube, the following tests were carried out:

In Fig. 1, a longitudinal section of two heat exchange condenser tubes can be seen, one covered by an enamel and the other uncoated, after both tubes have been subjected to fumes from an energy recovery plant of urban solid waste .

Fig. 2 shows scanning electron microscope images of the condenser tube of the example, where a continuous enamel is observed. The thickness of this coating is 150 pm. Figure 2b) clearly shows the interface between the carbon steel substrate and the enamel, responsible for the chemical-mechanical adhesion of the coating

Fig. 3 a-b shows the results of profilometry, for the carbon steel substrate (a) and for the enamel (b). The figure shows how the roughness of the coating / enamel is practically zero, so that the adhesion of corrosive particles is avoided.

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The enamel hardness is analyzed by Vickers hardness test (Figure 4), obtaining a value of 793 HV, higher than the average value of a carbon steel.

Young's modulus or module of longitudinal elasticity characterizes the behavior of an elastic material, according to the direction in which a force is applied. For the enamel of example 1, an elastic modulus value of 87 GPa was obtained.

The abrasion resistance by the Taber abrasion test, in which the mass loss Aw is measured after the action of an abrasive wheel for 10,000 cycles, has resulted in a mass loss value of 58 mg for the substrate, while for the enamel the loss value has been 3 mg, which shows a greater effectiveness of the enamel.

The impact resistance of the enamels, as well as the adhesion of said coatings / enamels to the carbon steel substrate were measured according to EN1020-9, which consists in the application of the force corresponding to a mass of 1.5 Kg released. from a height of 750 mm on the enamel itself. Under these conditions the adhesion obtained was grade 1, with the enamel completely adhered to the substrate.

Corrosion Resistance Tests

Figure 5 shows the heat exchange condenser used for these tests. The capacitor comprises the following elements:

1. Housing

2. Smoke inlet

3. Smoke and condensate outlet

4. Moorings

5. Distributor

6. Tubes

7. Fitting: cooling fluid inlet and outlet

8. Baffles: Set of baffles with chamfers located in different sections in the longitudinal direction inside the housing that direct the cooling fluid increasing its efficiency.

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The condenser is composed of 19 tubes (6) similar to those described above.

For the performance of the test, an approximate flow rate of 76 kg / h of fumes composed mainly of the following corrosive agents was passed through the condenser tubes: 68 ppm NO, 6.33% CO2 and 68 ppm NOx from an energy recovery plant for urban solid waste.

After the condensation of the fumes, the components that have been in contact with the pipes have been among others:

• 66.8 mg of SO42 "/ L

• 35.2 mg of Cl "/ L

• 0.15 mg of F "/ L

• 1.01mg of NO3 "/ L

Regarding the acid pH value of these condensates, it should be noted that it is 3.65.

As can be seen in Figure 1, the enamel coated tube after the tests remains unchanged, that is, it does not show any chemical attack.

Claims (12)

5 10 fifteen twenty 25 30 35 1. Heat exchange condenser characterized by • comprising a set of pipes through which fumes circulate to condense; • where the pipes are arranged inside a housing; • where a cooling fluid circulates through the space between the housing and the tubes; • and where each tube is made of carbon steel and is covered by its inner face, optionally by its outer face, by an enamel. 2. Condenser according to claim 1, wherein the carbon percentage of the carbon steel tube is between 0.003% and 1.4%. 3. Condenser according to claim 2, wherein the carbon percentage of the carbon steel tube is between 0.003% and 0.3%. 4. Condenser according to any one of claims 1 to 3, wherein the enamel contains a weight percentage in terms of the following equivalent oxides of: • between 50% and 55% of SiO2, • between 12.5% and 14% of Na2O, • between 6% and 7% of K2O, • between 14% and 15.5% of B2O3, • between 5% and 8% of TiO2, and • between 1% and 3% CoO. 5. Condenser according to claim 4, wherein the enamel also contains additives selected from SiO2, CoO, TiO2 and a combination thereof and wherein said enamel contains a percentage by weight in terms of the following equivalent oxides: • between 55% and 63.5% of SiO2, • between 8.75% and 11.4% of Na2O, • between 4.4% and 5.5% of K2O, • between 10% and 12.7% of B2O3, 5 10 fifteen twenty 25 30 • between 4.5% and 11.25% of TiO2, and • between 0.9% and 3.75% CoO. 6. Condenser according to any one of claims 1 to 5, wherein the enamel has a thickness of between 100 pm and 300 pm. 7. Condenser according to claim 6, wherein the enamel has a thickness between 140 pm and 160 pm. 8. Condenser according to any one of claims 1 to 7, characterized in that it has an inlet and outlet of a cooling fluid. 9. Condenser according to any one of claims 1 to 8, characterized in that it has a smoke inlet and a smoke and condensate outlet. 10. Condenser according to any one of claims 1 to 9, wherein each tube is made of carbon steel and is coated, by its inner face and its outer face, by an enamel. 11. Use of the condenser according to any of claims 1 to 10 for smoke condensation. 12. Use of the condenser according to claim 11 for the condensation of highly corrosive fumes, wherein said smoke comprises • at least 6% of COx or • at least 37ppm of NOx or • at least 25 ppm of SOx or • at least 25 ppm of HCl or • a combination thereof.