New use of a material combination in chemical looping combustion applications

Abstract

The present disclosure is in the field of reducing carbon dioxide by carbon capture technology. The present disclosure is therefore directed to the use of a component consisting of a specific material combination to be used in chemical looping combustion applications. This disclosure also pertains to a plant including a chemical looping combustion reactor comprising said component.

Description

[0001] NEW USE OF A MATERIAL COMBINATION IN CHEMICAL LOOPING COMBUSTION APPLICATIONS

[0002] TECHNICAL FIELD

[0003] The present disclosure is in the field of reducing carbon dioxide by carbon capture technology. The present disclosure is therefore directed to the use of a component consisting of a specific material combination to be used in chemical looping combustion applications. This disclosure also pertains to a plant including a chemical looping combustion reactor comprising said component.

[0004] BACKGROUND

[0005] Chemical looping combustion (CLC) is a process which uses two or more reactions to perform oxidation of hydrocarbon-based fuels, for example an oxygen-carrying compound (normally a metal) is first oxidized in the air forming an oxide. This oxide is then reduced using a hydrocarbon as a reducer in a second reaction.

[0006] In recent years, the interest in CLC has increased as the process has been shown to be useful as a carbon capture technique due to the fact that the two redox reactions of the process generate two intrinsically separated gas streams, one stream from the air reactor consisting of atmospheric N2 and residual O2, but essentially free of CO2; and one stream from the fuel reactor predominately containing CO2and H2O with very little diluent nitrogen. The air reactor gas may be discharged to the atmosphere causing minimal CO2pollution. The reducer exit gas contains almost all of the CO2generated by the system and as water vapor can easily be removed via condensation, a stream of high concentration of CO2will be obtain, thus capturing carbon.

[0007] During the combustion of fuel of biomass origin in the fuel reactor, there will be a release of alkali compounds, and these compounds will be transported to the air reactor and thus create a corrosive environment in this reactor. Alkali corrosion is a severe type of corrosion which few materials can withstand and there is therefore a need to find a solution to this problem.

[0008] The present invention therefore aims at providing a solution which will reduce or even eliminate corrosion for components used in chemical looping combustion reactors. SUMMARY

[0009] An aspect of the present disclosure is thus to provide a use of a component comprising an outer layer in the form of a tube or a coating of an iron-chromium-aluminium, FeCrAI, alloy having a composition of

[0010] 9 - 25 weight% Cr;

[0011] 2.5 - 8 weight% Al;

[0012] 0 - 5 weight% Mo; the balance being Fe and normally occurring impurities, and optionally other intentionally added alloying elements and an inner layer of a stainless steel or a nickel-based alloy as a construction component for a chemical looping combustion reactor. Thus, said component may be used as a construction component for a chemical combustion reactor. Further, more than one construction component may be used in the chemical combustion reactor.

[0013] The inventors have surprisingly found that an iron-chromium-aluminium alloy (FeCrAI alloy) as defined hereinabove or hereinafter will be able to form an alumina (AI2O3) layer during operation at a temperature range of 600 to 800 °C. This layer will protect of the component from alkali compounds and thereby corrosion which especially occurs during operation. This finding is very surprising as FeCrAI alloys normally do not form a protective alumina layer at these temperatures in the presence of alkali.

[0014] The present disclosure also provides plant, said plant includes a chemical looping combustion reactor comprising one or more components as defined hereinabove or hereinafter. According to embodiments, the one or more components as defined hereinabove or hereinafter may be positioned in or close to the air reactor and by using said one or more components, corrosion will be prevented or at least reduced.

[0015] Further, the present disclosure also provides a process for reducing carbon dioxide emission by carbon capture technology, said process comprises using one or more components as defined hereinabove or hereinafter in a chemical looping combustion reactor. According to embodiments, the one or more components is positioned in or close to the air reactor.

[0016] Additionally, the present invention provides a process for reducing CO2 emission when burning biofuels using a chemical looping combustion reactor wherein the process comprises contacting an alkali compound with one or more equipment part of an air reactor which has been made from or contain a component or at least one component as defined hereinabove or hereinafter. Brief description of the figures

[0017] Figure 1 shows a schematic description of a chemical looping combustion reactor (CLC) showing an air reactor denoted I and a fuel reactor denoted II;

[0018] Figure 2 shows the mass gain result of the tests performed.

[0019] Detailed description

[0020] The present invention provides a use of a component comprising an outer layer in the form of a tube or a coating of an iron-chromium-aluminium, FeCrAI, alloy having a composition of

[0021] 9 - 25 weight% Cr;

[0022] 2.5 - 8 weight% Al;

[0023] 0 - 5 weight% Mo; the balance being Fe and normally occurring impurities, and optionally other intentionally added alloying elements and an inner layer of a stainless steel or a nickel-based alloy as a construction component for a chemical looping combustion reactor.

[0024] It is thus the outer layer of the component as defined hereinabove or hereinafter which is in contact with the alkali compound(s). Thus, said component may be used as a construction component in a chemical combustion reactor. Also, more than one construction component may be present in the chemical combustion reactor. According to embodiments, the component as defined hereinabove or hereinafter is positioned in or close to the part of the chemical looping combustion reactor which is an air reactor.

[0025] According to embodiments, the stainless steel or the nickel-based alloy is selected from the group of materials which are used for high-pressure applications. The stainless steel may be selected from the group consisting of austenitic stainless steels comprising chromium in the range of from 18 to 30 weight% and nickel in the range of from 10 to 50 weight%. Examples, but not limiting of such alloys, are an alloy sold under the trade name Sanicro® 25 (S31035) or alloys sold under the name of 310HCbN alloy (S31042), or NF709 alloy (S31025), also known as Alloy 709. Further, the nickel-based alloy is selected from the group consisting of nickel-based steel comprising of 15 to 30 weight% chromium and more than 40 weight% nickel. Examples, but not limiting of such alloys are alloys known as Alloy 617 (UNS 6617) and HR6W alloy (UNS N6675). When ranges are disclosed in the present disclosure, such ranges include the respective end values of the range, unless explicitly disclosed otherwise. Similarly, when an open range is disclosed, the open range also include the single end value of the open range, unless explicitly disclosed otherwise.

[0026] According to embodiments, the content of Al in the FeCrAI alloy may be from 3-7 weight%. According to embodiments, the content of Cr in the FeCrAI alloy may be from 9-13 weight% or from 20.5 - 25 weight%. According to embodiments, the content of Mo in the FeCrAI alloy may be from 1-4 weight%.

[0027] According to embodiments, the FeCrAI alloy may additionally comprise the following elements in weight% (wt%):

[0028] Y 0.05-0.60;

[0029] Zr 0.01-0.40;

[0030] Hf 0.05-0.50;

[0031] Ta 0.05 - 0.50;

[0032] Ti 0-0.10;

[0033] C 0.01-0.05;

[0034] N 0.01- 0.06 N;

[0035] O 0.02-0.100;

[0036] Mn 0.05- 0.50 Mn;

[0037] P 0-0.08P;

[0038] S 0- 0.005 S.

[0039] According to embodiments, the FeCrAI alloy may additionally comprise the following elements weight% (wt%):

[0040] C 0.01-0.1;

[0041] N 0.001-0.1;

[0042] O 0.02-0.10;

[0043] B 0-0.01;

[0044] Mn 0-0.5;

[0045] Y 0-2.2;

[0046] Sc+Ce+La 0-0.2;

[0047] Ti 0-1.7;

[0048] Zr 0 - 0.4;

[0049] Nb 0-0.4;

[0050] V 0-0.1; Hf+Ta+Th 0-0.3.

[0051] According to embodiments, the FeCrAI alloy may additionally comprise the following elements weight% (wt%):

[0052] C 0.01-0.1;

[0053] N 0.001-0.1;

[0054] O <0.2;

[0055] Si 1.0 to 3;

[0056] Mn <0.4;

[0057] Mo + W<4;

[0058] Y <1.0;

[0059] Sc, Ce, and / or La < 0.2;

[0060] Zr < 0.40;

[0061] RE < 1.0.

[0062] According to embodiments, the FeCrAI alloy may additionally comprise the following elements weight% (wt%):

[0063] C 0.01-0.1;

[0064] N 0.001-0.1;

[0065] O <0.2;

[0066] Si 0.1 to 3;

[0067] Mn <0.4;

[0068] Mo + W<4;

[0069] Y <1.0;

[0070] Sc, Ce, and / or La < 0.2;

[0071] Zr < 0.40;

[0072] RE < 1.0.

[0073] According to embodiments, the coating may be applied using thermal spraying or welding or cladding.

[0074] According to embodiments, the component is a cladding tube having an outer cladding layer of a FeCrAI alloy. When the FeCrAI alloy is in the form a tube, it will form the outer tube of the tube, such as the outer layer of a composite tube. A composite tube consists of two different alloys which have been metallurgically bonded together to achieve good thermal transfer properties. The metallurgically bond may be achieved through co-extrusion or hot drawing. According to embodiments, the component as defined hereinabove or hereinafter may be a superheater tube. The term "superheater tube" is usually used for a tube which, during operation, is in contact with steam on one side and hot combustion gas(es) on the other side.

[0075] According to embodiments, the layer of FeCrAI alloy as defined hereinabove or hereinafter may have a thickness in the range of 0.1 to 10 mm.

[0076] Figure 1 shows the basic concept for a chemical looping combustor reactor which uses two reactors. However, there may be more than two reactors. The reactor with reference sign I is the air reactor and reactor with reference sign II is the fuel reactor. The oxidised metal a) is transferred to the fuel reactor II from the air reaction I and the reduced metal b) is transferred to the air reactor I from the fuel reactor II. An air stream will enter the air reactor c) and O2 depleted air will flow from the air reactor d). A flow of air / steam and CO2 e) will enter the fuel reactor and H2O and CO2 f) will flow from the fuel reactor II. H2O will be separated from CO2 using for example condensation The CO2 which thus be captured.

[0077] The invention will be described in more detail below in the non-limiting Examples. The invention, however, is not limited to the exemplifying embodiments discussed but may be varied within the scope of the appended claims.

[0078] Examples

[0079] The following experiments were performed in order to simulate a CLC air reactor environment.

[0080] The materials used in the examples were:

[0081] Sample 1 - a steel sold under the trademark Sanicro’ 25;

[0082] Sample 2 - an FeCrAI alloys sold under the trademark Kanthal’ EF101;

[0083] Sample 3- an FeCrAI alloys sold under the trademark Kanthal’ EF100; and Sample 4 - an FeCrAI alloys sold under the trademark Kanthal’ APMT.

[0084] The nominal compositions (weight%) are presented in Table 1:

[0085] Table 1 Chemical composition of the alloys investigated (in weight%). The balance is iron in all cases and unavoidable impurities.

[0086] Alloy Cr Al Ni C Si Mn Other

[0087] 1 22.5 25 0.06 0.33 0.5 Co,Cu,W,Nb,N

[0088] 2 12.4 3.7 0.02 1.25 0.10 RE 3 10.1 4.0 0.02 0.3 0.2 RE

[0089] 4 21.3 4.9 0.03 0.4 0.2 Mo, RE

[0090] Coupons of the alloys were used and prior to exposure, the edges of the coupons were ground with SiC paper P1000 and the surfaces of coupons were ground and then polished down to 1 pm with a diamond suspension until a mirror-like surface was achieved.

[0091] The exposures were performed using a horizontal tube furnace with a sintered alumina tube (inner diameter: 40 mm). The samples were exposed to a gas composition of 5% O2 + 3% H2O + N2 bal. with and without 16 ppm KOH at 700 °C and for a period of 168 hours. A total of three samples were exposed in parallel for each corrosion test. The gas flow was set to 2.5 cm / s. The humidity of the gas was established by coupling a water bath (set at 24 °C which corresponds to 3% H2O by volume) in the gas stream. The water vapor was introduced to the dry gas through a Nation membrane FC 125-240- 5MP from Perma Pure, prior to entering the horizontal tube furnace.

[0092] Continuous KOH(g) in the gas stream was achieved by placing an alumina boat, containing K2COa(s), upstream of the samples at a maximum temperature of 698 °C. At the selected conditions K2COa(s) is expected to react with water vapor forming KOH(g). By positioning the K2COa(s) containing alumina boat upstream of the samples and at slightly lower temperature, condensation of K2COa(s) on the samples was prevented. The temperature of the designated position of the K2CO3 boat and the samples were measured prior to each exposure.

[0093] The furnace was flushed with 5% O2 + 3% H2O + N2 bal. at 900 °C overnight prior to the exposure and the K2CO3 boat and samples were first introduced into the furnace as the temperature reached 698°C and 700 °C, respectively. The mass gain of the exposed samples was recorded using a Sartorious™ balance with microgram resolution as soon as they reached room temperature.

[0094] Results from mass gains are presented in Figure 2 and as can be seen from Figure 2 all three FeCrAI alloys are able to form protective alumina scales which is shown by the low mass gain. The presented results further suggest that KOH(g) significantly accelerates the corrosion of the stainless steel by rapidly destroying the protective Cr-rich oxide scale, resulting in the formation of a multilayer oxide scale with inferior protective properties while the FeCrAI alloys retained a protective Al-rich oxide scale irrespective of the presence of KOH(g).

Claims

Claims1. A use of a component comprising an outer layer in the form of a tube or a coating of an iron- chromium-aluminium, FeCrAI, alloy having a composition of9 - 25 weight% Cr;2.5 - 8 weight% Al;0 - 5 weight% Mo; the balance being Fe and normally occurring impurities, and optionally other intentionally added alloying elements. and an inner layer of a stainless steel or a nickel-based alloy as a construction component for a chemical looping combustion reactor2. The use of a component according to claim 1, wherein the component is positioned in or close to the part of the chemical looping combustion reactor which is an air reactor.

3. The use according to claim 1 or claim 2, wherein the stainless steel or the nickel-based alloy is selected from the group of materials which are used for high-pressure applications.

4. The use according to anyone of claims 1 to 3, wherein the stainless steel is selected from the group consisting of austenitic stainless steels comprising chromium in the range of 18 to 30 weight% and nickel in the range of 10 to 50 weight%.

5. The use according to anyone of claims 1 to 3, wherein the nickel-based alloy is selected from the group of nickel-based alloys consisting of nickel-based alloys comprising 15 to 30 weight% chromium and more than 40 weight% nickel.

6. The use according to anyone of proceeding claims, wherein the content of Al in the FeCrAI alloy is more than 3 - 7 weight%.

7. The use according to anyone of proceeding claims, wherein content of Cr in the FeCrAI alloy is from 9 - 13 weight% or from 20.5 - 25 weight%.

8. The use according to anyone of proceeding claims, wherein the content of Mo in the FeCrAI alloy is from 1 - 4 weight%.

9. The use according to anyone of proceeding claims, wherein the FeCrAI alloy additionally comprises the following elements in weight%:Y 0.05-0.60;Zr 0.01-0.40;Hf 0.05-0.50;Ta 0.05 - 0.50;Ti 0-0.10Ti;C 0.01-0.05;N 0.01-0.06;O 0.02-0.10;Mn 0.05-0.50;P 0-0.08;S 0-0.005; or wherein the FeCrAI alloy additionally comprises the following elements in weight%C 0.01- 0.1 C;N 0.001- 0.1 N;0 0.02-0.100;B 0-0.01B;Mn 0-0.5Mn;Y 0-2.2Y;Sc+Ce+La 0 - 0.2;Ti 0-1.7;Zr 0 - 0.4;Nb 0-0.4;V 0-0.1;Hf+Ta+Th 0 - 0.3; or wherein the FeCrAI alloy additionally comprises the following elements in weight%:C 0.01-0.1;N 0.001-0.1;O <0.2;Si 1.0-3;Mn <0.4;Mo + W<4;Y < 1.0;Sc, Ce, and / or La < 0.2;Zr < 0.40;RE < 1.0 or wherein the FeCrAI alloy additionally comprises the following elements in weight%:C 0.01 - 0.1;N 0.001 - 0.1;0 <0.2;Si 0.1 to 3;Mn < 0.4;Mo + W < 4;Y < 1.0;Sc, Ce, and / or La < 0.2;Zr < 0.40;RE < 1.0.

10. The use according to anyone of proceeding claims wherein the coating has been applied using thermal spraying or welding or a cladding.

11. The use according to any one of claims 1 to 10, wherein the FeCrAI alloy is in the form a tube and forms a part of a composite tube.

12. The use according to anyone of proceeding claims, wherein the component is a superheater tube.

13. A plant comprising a chemical looping combustion reactor wherein said reactor comprises one or more of the components as defined in any one of claims 1 to 12.

14. A process of reducing carbon dioxide emission by carbon capture technology, said process comprises using one or more of the components as defined in any one of claims 1 to 12.

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