Preparation method of a bifunctional composite oxygen carrier

Abstract

The invention discloses a preparation method of a bifunctional composite oxygen carrier, which includes: successively crushing, washing with deionized water, filtering, drying, and crushing and screening again the iron-containing sludge ash and the calcium-containing sludge ash respectively to obtain the iron-containing sludge ash powder and the calcium-containing sludge ash powder; adding the iron-containing sludge ash powder and the calcium-containing sludge ash powder into a nitric acid solution respectively and stirring, and then carrying out vacuum filtration to obtain the pickled solution of the iron-containing sludge ash and the pickled solution of the calcium-containing sludge ash, as well as the pickled residue of the iron-containing sludge ash and the pickled residue of the calcium-containing sludge ash; mixing, drying, grinding, sintering, and crushing the pickled residue of the iron-containing sludge ash and the pickled residue of the calcium-containing sludge ash in sequence to prepare an inert carrier; mixing the pickled solution of the iron-containing sludge ash and the pickled solution of the calcium-containing sludge ash, and then adding the inert carrier to obtain a suspension, and adjusting the pH to 7.0 with NH3·H2O; drying, roasting, cooling, and crushing the neutral suspension in sequence to prepare the bifunctional composite oxygen carrier. The preparation method of the invention is simple, the raw materials used are industrial solid wastes, and the preparation cost is relatively low. It not only realizes the resource utilization of industrial solid wastes, but also the prepared oxygen carrier has the characteristics of high reaction activity and high product selectivity.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical looping gasification and resource utilization of industrial sludge ash, and particularly relates to a preparation method of a bifunctional composite oxygen carrier. Background Art

[0002] Chemical looping gasification is considered a new type of energy conversion technology, which usually uses metal oxides as oxygen carriers and heat carriers between the fuel reactor and the air reactor. In the chemical looping gasification technology, the fuel and the oxygen carrier come into contact to undergo an oxidation-reduction reaction to form syngas, and the reduced oxygen carrier is oxidized and regenerated by air to restore the lattice oxygen of the metal oxide. This gasification method avoids the direct contact between the fuel and the air. On the one hand, it can prevent the formed syngas from reducing its calorific value due to dilution by nitrogen in the air, and on the other hand, it can reduce the difficulty of separating and capturing carbon dioxide. Therefore, the chemical looping gasification technology has a very broad application prospect.

[0003] Currently, the oxygen carriers used for chemical looping gasification mainly come from natural ores, artificial synthesis, and solid waste, etc. With the acceleration of the industrialization process and the expansion of production scale, a large amount of industrial sludge is generated. During the disposal process, iron-containing flocculants or calcium oxide are usually added for dehydration conditioning. Therefore, the ash after industrial sludge disposal often contains more elements such as iron and calcium, which can be used as effective components of the oxygen carrier in chemical looping gasification, while the remaining components such as SiO2 and Al2O3 can be used as inert carriers for preparing the oxygen carrier.

[0004] If the iron, calcium and other components contained in industrial sludge ash are used alone or directly as the oxygen carrier for chemical looping gasification, there are often problems such as low reaction activity and poor product selectivity. If used in combination, on the one hand, it can undergo an oxidation-reduction reaction with the fuel, and on the other hand, it can absorb the CO2 component in the reaction products, significantly promoting the performance of the chemical looping gasification reaction. The present invention provides a preparation method of a bifunctional composite oxygen carrier, which efficiently combines the functions of transferring lattice oxygen and absorbing carbon dioxide of iron-containing sludge ash and calcium-containing sludge ash respectively, not only can significantly improve the reaction performance of chemical looping gasification, but also can obtain high-quality syngas products. Summary of the Invention

[0005] Aiming at the problems of low reaction activity and poor product selectivity when industrial sludge ash is directly or alone used as the oxygen carrier for chemical looping gasification, the present invention proposes a preparation method of a bifunctional composite oxygen carrier.

[0006] The present invention is realized by the following technical solutions: A preparation method of a bifunctional composite oxygen carrier according to the present invention includes the following steps: Step 1, successively crush, wash with deionized water, filter, dry, and crush and screen again the iron-containing sludge ash and the calcium-containing sludge ash to obtain iron-containing sludge ash powder and calcium-containing sludge ash powder; Step 2, add the iron-containing sludge ash powder and the calcium-containing sludge ash powder obtained in Step 1 to a nitric acid solution and stir, and then perform vacuum filtration to respectively obtain an iron-containing sludge ash pickling solution, a calcium-containing sludge ash pickling solution, an iron-containing sludge ash pickling residue, and a calcium-containing sludge ash pickling residue; Step 3, mix, dry, grind, sinter, and crush in sequence the iron-containing sludge ash pickling solution and the calcium-containing sludge ash pickling residue obtained in Step 2 to prepare an inert carrier; Step 4, mix the iron-containing sludge ash pickling solution and the calcium-containing sludge ash pickling solution obtained in Step 2, add the inert carrier obtained in Step 3 to obtain a suspension, and adjust the pH to 7.0 with NH3·H2O to obtain a neutral suspension; Step 5, dry, calcine, cool, and crush in sequence the neutral suspension obtained in Step 4 to prepare the bifunctional composite oxygen carrier.

[0007] Further, in the above preparation method of the bifunctional composite oxygen carrier, in Step 1, wash the iron-containing sludge ash and the calcium-containing sludge ash with deionized water respectively, and the ash-water ratio is 1.0 g:(20 - 50) mL.

[0008] Further, in the above preparation method of the bifunctional composite oxygen carrier, in Step 2, add the iron-containing sludge ash powder and the calcium-containing sludge ash powder to the nitric acid solution respectively, and the ash-acid ratio is 1.0 g:(20 - 50) mL.

[0009] Further, in the above preparation method of the bifunctional composite oxygen carrier, in Step 2, the molar concentration of the nitric acid solution is 1.0 - 2.0 mol / L.

[0010] Further, in the above preparation method of the bifunctional composite oxygen carrier, in Step 3, the sintering temperature of the pickling residue is 1000 - 1200 °C and the sintering time is 3 - 5 hours.

[0011] Further, in the above preparation method of the bifunctional composite oxygen carrier, in Step 4, the volume ratio of the iron-containing sludge ash pickling solution to the calcium-containing sludge ash pickling solution is 100 mL:(50 - 200) mL.

[0012] Further, in the above preparation method of the bifunctional composite oxygen carrier, in Step 5, the calcination temperature is 900 - 1000 °C and the calcination time is 3 - 5 hours.

[0013] The present invention has the following advantages compared with the prior art:

[0014] (1) Preparing a bifunctional composite oxygen carrier using industrial sludge ash can achieve the resource utilization of waste and reduce the impact on the ecological environment;

[0015] (2) Jointly preparing a bifunctional composite oxygen carrier from iron-containing industrial sludge ash and calcium-containing industrial sludge ash is beneficial to solving the problems of low reaction activity and poor product selectivity when used alone or directly;

[0016] (3) The iron and calcium elements in industrial sludge ash are used as effective components of the bifunctional composite oxygen carrier, and SiO2, Al2O3, etc. are used as inert carriers to construct a bifunctional composite oxygen carrier, significantly improving the chemical looping gasification reaction performance. Description of the Drawings

[0017] Figure 1 is a schematic diagram of a preparation method of a bifunctional composite oxygen carrier of the present invention;

[0018] Figure 2 is an XRD diffraction pattern of the bifunctional composite oxygen carrier containing iron and calcium sludge ash prepared in the embodiment of the present invention. Detailed Embodiments

[0019] The following detailed description of the embodiments of the present invention is given on the premise of the technical solution of the present invention. The detailed implementation manners and specific operation processes are given, but the protection scope of the present invention is not limited to the following embodiments.

[0020] Example 1

[0021] As Figure 1 shown, a preparation method of a bifunctional composite oxygen carrier is characterized by including the following steps:

[0022] Step 1, respectively crushing, washing with deionized water, filtering, drying, and then crushing and screening the iron-containing sludge ash and the calcium-containing sludge ash to obtain iron-containing sludge ash powder and calcium-containing sludge ash powder.

[0023] Specifically, washing the iron-containing sludge ash and the calcium-containing sludge ash with deionized water respectively, the ash-water ratio can be 1.0 g:(20 - 50) mL, preferably 1.0 g:(30 - 40) mL. In the actual process, after crushing the iron-containing sludge ash and the calcium-containing sludge ash, in order to make the subsequent operation effect better, it is also necessary to further grind, which can be achieved by a ball mill or an ultrafine grinder. In this embodiment, the iron-containing sludge ash and the calcium-containing sludge ash are respectively crushed and ground to a particle size less than or equal to 80 microns.

[0024] Step 2: Add the iron-containing sludge ash powder and calcium-containing sludge ash powder described in Step 1 to nitric acid solution respectively and stir, then perform vacuum filtration to obtain iron-containing sludge ash pickling solution, calcium-containing sludge ash pickling solution, iron-containing sludge ash pickling residue and calcium-containing sludge ash pickling residue respectively.

[0025] Specifically, add the iron-containing sludge ash powder and calcium-containing sludge ash powder to nitric acid solution respectively. The ash-to-acid ratio can be 1.0 g:(20 - 50) mL, preferably 1.0 g:(30 - 40) mL. In the actual process, when nitric acid washes the iron-containing sludge ash powder and calcium-containing sludge ash powder respectively, stirring is required. A magnetic stirring device can be used, with the rotation speed set at 300 - 500 rpm (revolutions per minute), the washing temperature controlled at 60 - 80 °C through a water bath, and the stirring time being 10 - 20 hours. The molar concentration of the nitric acid solution is 1.0 - 2.0 mol / L, preferably 1.5 - 2.0 mol / L.

[0026] Step 3: Mix, dry, grind, sinter and crush the iron-containing sludge ash pickling residue and calcium-containing sludge ash pickling residue described in Step 2 in sequence to prepare an inert carrier.

[0027] The pickling residue is used as the inert carrier of the oxygen carrier. If the roasting temperature is too low and the time is too short, the low-volatility components in the pickling residue cannot be removed completely and the structure is not consolidated enough, so it cannot be used as a stable inert carrier. Therefore, in the actual process, the sintering temperature is 1000 - 1200 °C, preferably 1050 - 1150 °C, and the sintering time is 3 - 5 hours, preferably 4 - 5 hours.

[0028] Step 4: Mix the iron-containing sludge ash pickling solution and calcium-containing sludge ash pickling solution described in Step 2, add the inert carrier described in Step 3 to obtain a suspension, and adjust the pH to 7.0 with NH3·H2O to obtain a neutral suspension.

[0029] Specifically, mix the iron-containing sludge ash pickling solution and calcium-containing sludge ash pickling solution. The volume ratio of the two can be 100 mL:(50 - 200) mL, preferably 100 mL:(100 - 200) mL. In the actual process, in order to make the added inert carrier mix fully with the suspension formed by the acid solution, a magnetic stirring device can be used, with the rotation speed set at 300 - 500 rpm (revolutions per minute), the washing temperature controlled at 60 - 80 °C through a water bath, and the stirring time being 10 - 20 hours.

[0030] Step 5: Dry, roast, cool and crush the neutral suspension described in Step 4 in sequence to prepare a bifunctional composite oxygen carrier.

[0031] To prepare a bifunctional composite oxygen carrier with stable structure and excellent performance, the solid matter after drying the neutral suspension should be fully oxidized and solidified. Therefore, the calcination temperature of the oxygen carrier is 900-1000°C, preferably 950°C, and the calcination time is 3-5 hours, preferably 5 hours.

[0032] Example 2

[0033] 100 parts of iron-containing sludge ash (Fe2O3: 53.37%) and 100 parts of calcium-containing sludge ash (CaO: 67.50%) were fully crushed and ground, sieved to obtain a particle size of less than or equal to 80 microns, fully washed with deionized water at an ash-water ratio of 1.0g:30mL, filtered, dried and sieved to obtain iron-containing sludge ash powder and calcium-containing sludge ash powder. The washed iron-containing sludge ash powder and calcium-containing sludge ash powder were respectively added to a nitric acid solution with a concentration of 2.0mol / L and an ash-acid ratio of 1.0g:30mL, stirred in a magnetic stirrer at a speed of 300rpm and a water bath temperature of 75°C for 15 hours, and then filtered to obtain a pickling solution and a pickling residue.

[0034] The pickling residues were uniformly mixed, dried, ground, sintered at 1050°C for 4.0 hours, and then crushed to obtain an inert carrier. Further, the iron-containing sludge ash pickling solution obtained above was mixed with the calcium-containing sludge ash pickling solution at a volume ratio of 100 mL:100 mL, and then the inert carrier was added, and the mixture was fully stirred to obtain a suspension, and the pH was adjusted to 7.0 with NH3·H2O to obtain a neutral suspension.

[0035] The neutral suspension is dried and calcined in sequence, the calcination is carried out in a muffle furnace at a temperature of 950° C. for 5 hours, and after cooling, it is crushed and sieved to obtain a dual-functional composite oxygen carrier.

[0036] Example 3

[0037] The iron-containing sludge ash pickling solution after washing with nitric acid and the calcium-containing sludge ash pickling solution were mixed in a volume ratio of 100 mL:150 mL to prepare a bifunctional composite oxygen carrier. The other operating procedures were the same as those in Example 2.

[0038] Example 4

[0039] The iron-containing sludge ash pickling solution after washing with nitric acid and the calcium-containing sludge ash pickling solution were mixed in a volume ratio of 100 mL:200 mL to prepare a bifunctional composite oxygen carrier. The other operating procedures were the same as those in Example 3.

[0040] Example 5 (X-ray diffraction test)

[0041] The bifunctional composite oxygen carriers obtained in Example 2, Example 3, and Example 4 were subjected to X-ray diffraction test; Figure 2X-ray diffraction patterns of the dual-functional composite oxygen carriers prepared from the acid-washed solutions of iron-containing sludge ash and calcium-containing sludge ash at volume ratios of 100 mL:100 mL, 100 mL:150 mL, and 100 mL:200 mL, respectively. From Figure 2 it can be seen that the dual-functional composite oxygen carriers have diffraction peaks of components such as Ca2Fe2O5, CaFeO4, Fe2O3, SiO2, and Al2O3.

Claims

1. A preparation method of a bifunctional composite oxygen carrier, characterized in that, It includes the following steps: Step 1: Crush, wash with deionized water, filter, dry, and crush and screen again the iron-containing sludge ash and calcium-containing sludge ash respectively to obtain the iron-containing sludge ash powder and calcium-containing sludge ash powder respectively; Step 2: Add the iron-containing sludge ash powder and calcium-containing sludge ash powder described in Step 1 to the nitric acid solution respectively and stir, then carry out vacuum filtration to obtain the pickled solution of iron-containing sludge ash and pickled solution of calcium-containing sludge ash, and the pickled residue of iron-containing sludge ash and pickled residue of calcium-containing sludge ash respectively; Step 3: Mix, dry, grind, sinter, and crush the pickled residue of iron-containing sludge ash and pickled residue of calcium-containing sludge ash described in Step 2 in sequence to prepare an inert carrier; Step 4: Mix the pickled solution of iron-containing sludge ash and pickled solution of calcium-containing sludge ash described in Step 2, add the inert carrier described in Step 3 to prepare a suspension, and adjust the pH to 7.0 with NH3·H2O to obtain a neutral suspension; Step 5: Dry, calcine, cool, and crush the neutral suspension described in Step 4 in sequence to prepare a bifunctional composite oxygen carrier.

2. The preparation method of a bifunctional composite oxygen carrier according to claim 1, characterized in that, In Step 1, wash the iron-containing sludge ash and calcium-containing sludge ash with deionized water respectively, and the ratio of ash to water is 1.0 g:(20 - 50) mL.

3. The preparation method of a bifunctional composite oxygen carrier according to claim 1, characterized in that, In Step 2, add the iron-containing sludge ash powder and calcium-containing sludge ash powder to the nitric acid solution respectively, and the ratio of ash to acid is 1.0 g:(20 - 50) mL.

4. The preparation method of a bifunctional composite oxygen carrier according to claim 1, characterized in that, In Step 2, the molar concentration of the nitric acid solution is 1.0 - 2.0 mol / L.

5. The preparation method of a bifunctional composite oxygen carrier according to claim 1, characterized in that In Step 3, the sintering temperature of the pickled residue is 1000 - 1200 °C and the sintering time is 3 - 5 hours.

6. The preparation method of a bifunctional composite oxygen carrier according to claim 1, characterized in that, In Step 4, the volume ratio of the pickled solution of iron-containing sludge ash to the pickled solution of calcium-containing sludge ash is 100 mL:(50 - 200) mL.

7. The preparation method of a bifunctional composite oxygen carrier according to claim 1, characterized in that, In Step 5, the calcination temperature is 900 - 1000 °C and the calcination time is 3 - 5 hours.

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