Magnesium-Iron Complex oxide for Separating and Purifying Carbon Dioxide and Fabrication Method thereof

Abstract

A method is provided for making a magnesium(Mg)-iron(Fe) complex oxide. The MgFe complex oxide is used for separating and purifying carbon dioxide (CO.sub.2). The present invention solves the problem of using iron ore in chemical looping combustion. The present invention comprises the following steps: At first, iron ore and magnesium nitrate (Mg(NO.sub.3).sub.2.6H.sub.2O) are impregnated for reaction. After sieving within a fixed range of size, calcination is processed to obtain the MgFe complex oxide. Not only the problem of using iron ore in chemical combustion loop is effectively solved; but also the whole procedure can be looped for a long time with a high CO.sub.2 conversion rate.

Claims

1. A method of fabricating a magnesium(Mg)-iron(Fe) complex oxide for separating and purifying carbon dioxide (CO.sub.2), comprising steps of (a) obtaining a source powder of iron ore and magnesium nitrate (Mg(NO.sub.3).sub.2.6H.sub.2O), wherein magnesium nitrate has a concentration of 1020 mole percents (mol %); (b) adding deionized water to said source powder to be stayed still for one day at a room temperature to form a mixed solution; (c) drying said mixed solution and sieving said mixed solution within an effective particle size range to form a mixed powder, wherein said effective particle size range is 0.1770.297 millimeters (mm); and (d) processing calcination under an atmosphere containing air to form a power of MgFe complex oxide.

2. The method according to claim 1, wherein, in step (b), said mixed solution is obtained with impregnation.

3. The method according to claim 1, wherein, in step (c), said mixed solution is dried at a temperature of 6080 Celsius degrees ( C.).

4. The method according to claim 1, wherein, in step (d), said calcination is processed at a temperature of 11001300 C.

5. The method according to claim 1, wherein, in step (d), said calcination is processed for a time of 2-4 hours.

6. The method according to claim 1, wherein, in step (d), said MgFe complex oxide comprises a ferric oxide (Fe2O3) and magnesium ferrite (MgFe2O4).

7. The method according to claim 1, wherein said MgFe complex oxide obtains a bamboo-like structure on a surface through 50 loops of a redox reaction at a high temperature under an atmosphere containing a synthesis gas, and said MgFe complex oxide obtains an increased gas-solid reaction between said synthesis gas and said MgFe complex oxide to maintain a steady CO.sub.2 conversion ratio for a long time.

8. The method according to claim 7, wherein said high temperature is a temperature of 900 C.20%.

9. The method according to claim 7, wherein, in said loops of said redox reaction, air is used in oxidation, carbon monoxide (CO) is used in reduction, and said CO has a composition ratio of 510%.

10. The method according to claim 7, wherein, after said 50 loops of redox, said CO2 conversion ratio is 8085%.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The present invention will be better understood from the following detailed description of the preferred embodiment according to the present invention, taken in conjunction with the accompanying drawings, in which

[0008] FIG. 1 is the view showing the preferred embodiment according to the present invention;

[0009] FIG. 2 is the view showing the X-ray diffraction pattern of the magnesium(Mg)-iron(Fe) complex oxide;

[0010] FIG. 3 is the view showing the carbon dioxide (CO.sub.2) conversion ratios of the MgFe complex oxide after the 50 loops of the redox reaction;

[0011] FIG. 4 is the view showing the surfaces observed through electron microscopy before and after the redox reactions; and

[0012] FIG. 5 is the view showing the bamboo-like structures of the MgFe complex oxide.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0013] The following description of the preferred embodiment is provided to understand the features and the structures of the present invention.

[0014] The present invention provides an improved technology. By adding a small amount of metal for modifying an iron-based oxide, iron ore can be effectively used in a chemical combustion loop for significantly enhancing reaction performance. Please refer to FIG. 1, which is a view showing a preferred embodiment according to the present invention. As shown in the figure, the present invention is a method of fabricating a MgFe complex oxide for separating and purifying CO.sub.2, comprising the following steps:

[0015] (a) Obtaining source powder 11: A source powder of iron ore and magnesium nitrate (Mg(NO.sub.3).sub.2.6H.sub.2O) are obtained.

[0016] (b) Forming mixed solution 12: Deionized water is added to the source powder to be stayed still at a room temperature for one day to form a mixed solution.

[0017] (c) Forming mixed powder 13: The mixed solution is dried and sieved within an effective particle size range to form a mixed powder.

[0018] (d) Obtaining final product 14: Calcination is processed under an atmosphere containing air to form a power of MgFe complex oxide.

[0019] Thus, a method of fabricating a MgFe complex oxide for separating and purifying CO.sub.2 is obtained.

[0020] In step (a), magnesium nitrate added has a concentration of 1020 mole percents (mol %). Then, the iron ore powder and the magnesium nitrate powder are mixed with impregnation to be dissolved in deionized water in step (b) and stayed still at a room temperature for one day to form a mixed solution. In step (b), a magnet can be used for constantly stirring until the solution is mixed evenly.

[0021] Then, in step (c), the mixed solution is dried and then sieved within an effective particle size range to form a mixed powder. Therein, the mixed solution is placed in an oven and heated to 6080 Celsius degrees ( C.) for drying. To be used in a fluidized bed reactor, the effective particle size range for sieving is set at 0.1770.297 millimeters (mm). The dried and sieved mixed powder is calcined in step (d). Under an atmosphere containing air, the calcination is processed at a temperature of 11001300 C. for a time of 24 hours. The powder obtained after the calcination is the powder of MgFe complex oxide fabricated according to the present invention.

State-of-Use 1: Identifying MgFe Complex Oxide Through X-Ray Diffraction

[0022] Please further refer to FIG. 2, which is a view showing an X-ray diffraction pattern of a MgFe complex oxide. As shown in the figure, an analysis of an X-ray diffraction result demonstrates that the compositions of the MgFe complex oxide fabricated according to the present invention are a ferric oxide (Fe.sub.2O.sub.3) and magnesium ferrite (MgFe.sub.2O.sub.4), where the magnesium ferrite has a spinel structure.

State-of-Use 2: Testing CO.sub.2 Conversion Rate of MgFe Complex Oxide with Laboratory-Grade Single Fluidized Bed Reactor

[0023] Please further refer to FIG. 3, which is a view showing CO.sub.2 conversion ratios of a MgFe complex oxide after 50 loops of a redox reaction. As shown in the figure, a MgFe complex oxide is processed through redox reactions without adding inert oxide. Carbon monoxide (CO) is introduced as a reducing gas, and the air is introduced as an oxidizing gas. Therein, CO has a composition ratio of 510 percents (%), and the reaction is processed at a temperature of 900 C. As results show, in 50 loops of redox reaction using the MgFe complex oxide, CO.sub.2 concentrations are low in the first 2-3 loops and then are maintained at a constant value. The reason is that the first 2-3 loops are activation reactions for the MgFe complex oxide. After the activation reactions, the MgFe complex oxide can maintain a stable CO.sub.2 conversion ratio of 8085% without significant declination in the 50 loops.

State-of-Use 3: Observing Surfaces Through Electron Microscopy Before and After Redox Reactions

[0024] Please further refer to FIG. 4 and FIG. 5, which are a view showing surfaces before and after the 50 loops of redox reactions observed through electron microscopy; and a view showing bamboo-like structures of the MgFe complex oxide. As shown in the figures, surfaces of the MgFe complex oxide formed after redox reactions are analyzed by using electron microscopy (3000 and 7000). Therein, pictures noting as (a) and pictures noting as (b) are the macroscopic and microscopic surfaces observed through electron microscopy before and after the redox reactions. In the pictures, bamboo-like structures are formed on the surfaces of the MgFe complex oxide after the redox reactions. In FIG. 5, the bamboo-like structures thus formed obtain significant size for the MgFe complex oxide to maintain the good gas-solid reaction. Thus, good reactivity is maintained after the redox reactions for solving the problem of traditional chemical looping combustion of unmodified iron-based oxide. Therein, the problem in the chemical looping combustion is that aggregation may easily happen in the redox reaction to decrease CO.sub.2 conversion ratio.

[0025] Thus, the MgFe complex oxide fabricated according to the present invention has the bamboo-like structure formed on the surface to increase the gas-solid reaction between the MgFe complex oxide and air for maintaining a stable CO.sub.2 conversion ratio in reactions for a long time.

[0026] To sum up, the present invention is a method of fabricating a MgFe complex oxide for separating and purifying CO.sub.2, where the problem of traditional chemical looping combustion using iron ore is solved for maintaining a high CO.sub.2 conversion ratio within loops of redox reaction for a long time.

[0027] The preferred embodiment herein disclosed is not intended to unnecessarily limit the scope of the invention. Therefore, simple modifications or variations belonging to the equivalent of the scope of the claims and the instructions disclosed herein for a patent are all within the scope of the present invention.