WO2017089637A1

WO2017089637A1 - Heat exchange condenser for condensing smokes

Info

Publication number: WO2017089637A1
Application number: PCT/ES2016/070823
Authority: WO
Inventors: Javier ESQUIROZ; José María VERGARA; Josemari MUÑOZ
Original assignee: Sartech Engineering,S.L.; Ertxin 359, S.L.; Fundación Cidetec
Priority date: 2015-11-25
Filing date: 2016-11-18
Publication date: 2017-06-01
Also published as: ES2566983B1; ES2566983A1

Abstract

The present invention relates to a heat exchange condenser which comprises carbon steel tubes coated with a custom-made enamel. The invention further relates to the use of the heat exchange condenser for condensing smokes, particularly for highly corrosive smokes coming, for example, from thermal power stations, combustion engines, oil refineries, energy recovery plants, cement kilns and/or glass industries.

Description

HEAT EXCHANGE CONDENSER FOR CONDENSATION OF

SMOKE

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 smoke condensation, 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 in 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 smoke condensation of highly corrosive components. Few solutions can be found in the literature, 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 capacitors 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 their use It is discouraged for temperatures above 260 ° C, the temperature from which it decomposes.

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 coolant for, for example, the generation of electricity, such as domestic hot water, as a source of heat for drying raw materials in 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 according to 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 condense is between 700 ° C and 800 ° C, it has also been of adjusting the temperature of the refrigerant fluid for the correct operation of the condenser. Hence, an advantage of the condenser of the invention is that it is 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 tubes 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, while not affecting the chemical resistance thereof, 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 Si0 ₂ ,

• between 12.5% and 14% of Na ₂ 0,

• between 6% and 7% of K ₂ 0,

• between 14% and 15.5% of B ₂ 0 ₃ ,

· Between 5% and 8% of Ti0 ₂ , and • between 1% and 3% CoO.

In a preferred embodiment, the enamel also contains additives selected from Si0 ₂ , CoO, Ti0 ₂ 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 Si0 ₂ ,

• between 8.75% and 1 1, 4% of Na ₂ 0,

• between 4.4% and 5.5% of K ₂ 0,

• between 10% and 12.7% of B ₂ 0 ₃ ,

· Between 4.5% and 1 1, 25% of Ti0 ₂ , and

• between 0.9% and 3.75% CoO.

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

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 capacitor of the invention, each tube of carbon steel is coated both on its inner side and its outer side by enamel described above, both without and with additives selected from Si0 _2, Ti0 _2, 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 an 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 condenser heat exchange mentioned above, one which comprises an enamel selected from Si0 _2, Ti0 _2, CoO and a combination thereof and containing additives in term of oxide equivalents

Between 55% and 63.5% of Si0 ₂ ,

• between 8.75% and 1 1, 4% of Na ₂ 0,

• between 4.4% and 5.5% of K ₂ 0,

• between 10% and 12.7% of B ₂ 0 ₃ ,

• between 4.5% and 1 1, 25% of Ti0 ₂ , 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 HCI or

• a combination thereof.

The 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 features 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 microscopy images of the heat exchange condenser tube of Example 1; b) Magnification of the microscopy image scanning electronics of a heat exchange condenser tube of example 1, interface between the carbon steel substrate and the enamel;

FIG. 3 Profilesometry results 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 glaze the inside 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 a "slip", which is screened until an average particle size of between 40 μηι and 200 μηι. This paste was deposited on the inner side of the steel tube by the technique called Flow-coating in English. Finally, the vitrification treatment of the whole (paste applied on the carbon steel tube) and dried was carried out. The treatment consists of heating the assembly to temperatures above 700 ° C so that the enamel acquires its vitreous character.

As an exemplary embodiment, an enamel composition was prepared in terms of equivalent oxides of:

• 52.9% of Si0 ₂ ,

13.2% of Na ₂ 0,

• 6.6% of K ₂ 0,

• 14.6% of B ₂ 0 ₃ ,

• 7.5% of Ti0 ₂ , and

• 2.1% CoO.

and a density of 1.74 g / l.

Characterization of the 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 observed, one covered by an enamel and the other uncoated, after both tubes have been subjected to fumes from an energy recovery plant for urban solid waste .

Fig. 2 shows scanning electron microscopy images of the condenser tube of the example, where a continuous enamel is observed. The thickness of this coating is 150 μηι. 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 ab 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 virtually nil, so adhesion of corrosive particles is avoided.

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 modulus 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 Δω 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 EN 1020-9, which consists in the application of the force corresponding to a mass of 1.5 Kg launched 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. The condenser is composed of 19 tubes (6) similar to those described above.

For the conduct of the test, an approximate flow rate of 76 kg / h of fumes composed mainly of the following corrosive agents has been passed through the condenser tubes: 68 ppm NO, 6.33% C0 ₂ and 68 ppm NO _x 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 S0 ₄ ^2_ L

• 35.2 mg of CI7L

• 0.15 mg of F7L

• 1.01 mg of N0 ₃ 7L

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 tube coated with the enamel after the tests remains unchanged, that is, it has no chemical attack.

Claims

Heat exchange condenser characterized by

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

• where the pipes are arranged inside a housing;

Condenser according to claim 1, wherein the carbon percentage of the carbon steel tube is between 0.003% and 1.4%.

Condenser according to claim 2, wherein the carbon percentage of the carbon steel tube is between 0.003% and 0.3%.

Condenser according to any one of claims 1 to 3, wherein the enamel contains a percentage by weight in terms of the following equivalent oxides of:

• between 50% and 55% of Si0 ₂ ,

• between 12.5% and 14% of Na ₂ 0,

• between 6% and 7% of K ₂ 0,

• between 14% and 15.5% of B ₂ 0 ₃ ,

• between 5% and 8% of Ti0 ₂ , and

• between 1% and 3% CoO.

Condenser according to claim 4, wherein the enamel further contains additives selected from Si0 ₂ , CoO, Ti0 ₂ 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 Si0 ₂ ,

• between 8.75% and 1 1, 4% of Na ₂ 0,

• between 4.4% and 5.5% of K ₂ 0,

• between 10% and 12.7% of B ₂ 0 ₃ , • between 4.5% and 1 1, 25% of Ti0 ₂ , 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 between 100 μηι and 300 μηι.

7. Condenser according to claim 6, wherein the enamel has a thickness between 140 μηι and 160 μηι. 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. 1 1. Use of the condenser according to any one of claims 1 to 10 for smoke condensation.

12. Use of the condenser according to claim 1 for the condensation of highly corrosive fumes, wherein said smoke comprises

at least 6% of CO _x or

at least 37ppm of NO _x o

at least 25 ppm of SO _x or

at least 25 ppm of HCI or

A combination of them.