Calcium-based composite material as well as preparation method and application thereof

Abstract

The invention discloses a calcium-based composite material as well as a preparation method and application thereof. The preparation method comprises the following steps: cleaning and drying high-porosity straw biomass charcoal particles; mixing the biochar particles with calcium peroxide, and enabling the powdery calcium peroxide to enter pores of the biochar through vibration to obtain the biochar loaded with the calcium peroxide; mixing the calcium peroxide-loaded biochar particles and calcium hydroxide-containing minerals according to a certain proportion to obtain a calcium-based composite material; the calcium-based composite material is added into dried sludge, the adding amount accounts for 5-15 wt.% of the dry basis mass of the sludge, then a lignin binder is added, compression molding is performed, the calcium-based composite material is added in the pyrolysis process, the sulfur fixation rate can be larger than 60%, most of nitrogen is converted into ammonia, hydrogen cyanide is greatly reduced, synergistic sulfur fixation and nitrogen control in sludge pyrolysis are achieved, and the sulfur fixation and nitrogen control efficiency is improved. And the emission of pollution gas is reduced.

Description

Technical Field

[0001] The invention relates to a method for realizing sulfur fixation and nitrogen control with a calcium-based composite material, and in particular to a method for realizing synergistic sulfur fixation and nitrogen control in sludge pyrolysis by using a calcium-based composite material composed of calcium peroxide-loaded biochar particles and calcium hydroxide-containing minerals. Background Art

[0002] With the development of the economy and society, the improvement of sewage treatment volume and standards, and the rapid growth of sludge production. Sludge not only contains a large amount of carbon, nitrogen, phosphorus, sulfur and other recyclable substances, but also contains a large number of pathogens, microplastics and heavy metals and other toxic and harmful substances, which means that while recycling sludge, the release of pollutants must be strictly controlled. In 2022, the Ministry of Housing and Urban-Rural Development issued the "Implementation Plan for Harmless Treatment and Resource Utilization of Sludge", emphasizing the harmless and resource utilization of sludge. Sludge pyrolysis technology can eliminate pathogens, realize the qualitative and quantitative transformation of sludge components, and maximize the energy recovery rate, providing a promising harmless utilization method for sludge treatment.

[0003] Sludge contains a large amount of elements such as C, N, S, P and K. Under the pyrolysis environment, S and N in the sludge can be easily converted into sulfur-containing and nitrogen-containing gases, such as H2S, HCN, etc., which increases the risk of air pollution. By adding calcium hydroxide and / or calcium oxide during the pyrolysis process, sulfur can be converted into calcium sulfide and part of calcium sulfate to achieve sulfur fixation and reduce the release of sulfur-containing pollutants such as H2S. It can also catalyze the decomposition of HCN and convert nitrogen into NH3, thereby achieving sulfur fixation and nitrogen resource conversion. However, due to the generation of water vapor during the pyrolysis process, part of the calcium sulfide becomes unstable under the action of water vapor and decomposes to produce H2S gas; on the other hand, conventional calcium hydroxide and / or calcium oxide materials are also difficult to significantly reduce the release of HCN. Summary of the invention

[0004] Purpose of the invention: In view of the defects of the prior art, the purpose of the present invention is to provide a calcium-based composite material and a preparation method and use thereof.

[0005] Technical solution: The first aspect of the present invention provides a method for preparing the calcium-based composite material, comprising the following steps:

[0006] (1) Selecting high-porosity straw biochar particles, washing and drying them;

[0007] (2) mixing the biochar particles with calcium peroxide so that the powdered calcium peroxide enters the pores of the biochar to obtain biochar particles loaded with calcium peroxide;

[0008] (3) The calcium peroxide-loaded biochar particles and the calcium hydroxide-containing mineral are mixed in a certain proportion to obtain a calcium-based composite material.

[0009] Furthermore, the straw biochar raw material is organic waste or sawdust, preferably wheat or corn waste or sawdust.

[0010] Furthermore, the porosity of the straw biomass charcoal particles is between 40% and 90%.

[0011] Furthermore, the loading amount of calcium peroxide on the biochar is 30-80 g / 100 gC.

[0012] Furthermore, the calcium hydroxide-containing mineral is one or a mixture of calcium oxide, calcium hydroxide, carbide slag, and red mud.

[0013] Furthermore, the mass ratio of the biochar particles loaded with calcium peroxide to the calcium hydroxide-containing mineral in the calcium-based composite material is 3 to 5:1.

[0014] The second aspect of the present invention provides a calcium-based composite material prepared by the method.

[0015] The third aspect of the present invention provides the use of the calcium-based composite material, which is added to the dried sludge, and then a lignin binder is added, and then the sludge is pressed and pyrolyzed and carbonized.

[0016] Furthermore, the calcium-based composite material is added in an amount of 5 to 15 wt.% of the dry sludge mass; and the lignin binder is added in an amount of 5 to 15 wt.% of the dry sludge mass.

[0017] Furthermore, the lignin binder is lignin or lignin residue after hydrolysis of straw.

[0018] The novel calcium-based composite material provided by the present invention is used for synergistic sulfur fixation and nitrogen control in sludge pyrolysis. The novel calcium-based composite material is composed of biochar particles loaded with calcium peroxide and calcium hydroxide-containing minerals. Calcium peroxide is loaded in the pores of high-porosity straw biochar particles, and slow oxygen release of calcium peroxide can be achieved during pyrolysis. Under the joint action of calcium hydroxide, it is beneficial to oxidize sulfur elements into more stable sulfate ions, effectively improving the pyrolysis sulfur fixation efficiency. At the same time, the active CaO produced by the decomposition of calcium peroxide in the calcium-based composite material and the joint catalytic effect of calcium hydroxide are utilized to control the directional conversion of nitrogen into NH3 during sludge pyrolysis, and catalyze the decomposition and conversion of HCN. NH3 in the pyrolysis gas can be recycled in the pyrolysis gas purification link. In sludge pyrolysis, the synergistic sulfur fixation and nitrogen control of the novel calcium-based composite material improves the sulfur fixation efficiency, effectively reduces the emission of polluted gases, and realizes the recovery of valuable elements, which has broad commercial application potential.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The raw materials used in the calcium-based composite material disclosed in the present invention are easily available, the dosage is low, and the sulfur fixation and nitrogen control effects of sludge pyrolysis can be significantly enhanced.

[0021] 2. The calcium-based composite material provided by the present invention uses straw biochar particles as a carrier of calcium peroxide, which can load a large amount of calcium peroxide in the pores of biochar, allowing the biochar particles loaded with calcium peroxide to become slow oxygen releasers during pyrolysis. After calcium peroxide releases oxygen, the product calcium oxide reacts with sulfur produced by sludge pyrolysis to form calcium sulfide, which is further oxidized by the oxygen released by calcium peroxide to become more stable calcium sulfate, thereby increasing the sulfur fixation rate.

[0022] 3. The calcium hydroxide mineral in the calcium-based composite material can catalyze the conversion of nitrogen in the sludge into NH3 and a small amount of HCN. The calcium oxide produced by the decomposition of the loaded calcium peroxide can catalyze the decomposition of HCN and convert HCN into NH3. The produced NH3 can be recycled in the pyrolysis gas purification link. The use of calcium-based composite materials in sludge pyrolysis achieves the effect of sulfur fixation and nitrogen control, greatly reducing the emission of sulfur- and nitrogen-containing polluted gases. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be further described below.

[0024] Example 1

[0025] A method for realizing synergistic sulfur fixation and nitrogen control in sludge pyrolysis by using calcium-based composite materials, wherein biochar particles with a porosity of 60% are selected, cleaned and dried, calcium peroxide is loaded into the pores of the biochar by vibration mixing, and the biochar loaded with calcium peroxide and a calcium hydroxide-containing mineral are mixed at a mass ratio of 3:1 to obtain a calcium-based composite material. According to the different inorganic content of the dried sludge, 5-15wt.% of the calcium-based composite material and 5-15wt.% of the sludge dry basis mass of the sludge are added as a lignin binder, and after compression molding and drying, an anaerobic pyrolysis treatment is performed.

[0026] The sulfur fixation rate of the sludge after pyrolysis is greater than 60%, and the gaseous nitrogen-containing products are mainly NH3 and HCN, among which the HCN yield drops from 3.5% without the addition of calcium-based composite materials to 0.8%.

[0027] Example 2

[0028] Biochar particles with a porosity of 70% are selected, cleaned and dried, calcium peroxide is loaded into the pores of the biochar by vibration mixing, and the biochar loaded with calcium peroxide and a calcium hydroxide-containing mineral are mixed at a mass ratio of 4:1 to obtain a calcium-based composite material. According to the different inorganic content of the dried sludge, 5-15wt.% of the calcium-based composite material and 5-15wt.% of the sludge dry basis weight are added as a lignin binder, and after compression molding and drying, an anaerobic pyrolysis treatment is performed.

[0029] The sulfur fixation rate of the sludge after pyrolysis is greater than 62%, and the gaseous nitrogen-containing products are mainly NH3 and HCN, among which the HCN yield drops from 3.5% without the addition of calcium-based composite materials to 0.5%.

[0030] Example 3

[0031] Biochar particles with a porosity of 80% are selected, cleaned and dried, calcium peroxide is loaded into the pores of the biochar by vibration mixing, and the biochar loaded with calcium peroxide and a calcium hydroxide-containing mineral are mixed at a mass ratio of 5:1 to obtain a calcium-based composite material. According to the different inorganic content of the dried sludge, 5-15wt.% of the calcium-based composite material and 5-15wt.% of the sludge dry basis mass of the sludge are added as a lignin binder, and after compression molding and drying, an anaerobic pyrolysis treatment is performed.

[0032] The sulfur fixation rate of the sludge after pyrolysis is greater than 62%, and the gaseous nitrogen-containing products are mainly NH3 and HCN, among which the HCN yield drops from 3.5% without the addition of calcium-based composite materials to 0.5%.

[0033] The above embodiments:

[0034] The straw biochar raw material is organic waste or sawdust, preferably wheat or corn waste or sawdust.

[0035] The porosity of straw biomass charcoal particles is between 40% and 90%.

[0036] The loading amount of calcium peroxide on biochar is 30-80g / 100gC.

[0037] The calcium hydroxide-containing mineral is one or a mixture of calcium oxide, calcium hydroxide, carbide slag and red mud.

[0038] The mass ratio of calcium peroxide-loaded biochar particles to calcium hydroxide-containing minerals in the calcium-based composite material is 3 to 5:1.

[0039] The addition amount of the calcium-based composite material accounts for 5-15wt.% of the dry sludge mass; the addition amount of the lignin binder accounts for 5-15wt.% of the dry sludge mass.

[0040] The lignin binder is lignin or lignin residue after hydrolysis of straw.

[0041] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any technician in the relevant technical field, without departing from the scope of the technical solution of the present invention, makes any form of equivalent replacement or modification to the technical solution and technical content disclosed in the present invention, which does not depart from the content of the technical solution of the present invention and still falls within the protection scope of the present invention.

Claims

1. A method for preparing a calcium-based composite material, characterized in that: The following steps are involved: (1) Selecting high-porosity straw biochar particles, washing and drying them; (2) mixing the biochar particles with calcium peroxide so that the powdered calcium peroxide enters the pores of the biochar to obtain biochar particles loaded with calcium peroxide; (3) The calcium peroxide-loaded biochar particles and the calcium hydroxide-containing mineral are mixed in a certain proportion to obtain a calcium-based composite material.

2. The method for preparing the calcium-based composite material according to claim 1, characterized in that: The straw biomass charcoal raw material is organic waste or sawdust, preferably wheat or corn waste or sawdust.

3. The method for preparing the calcium-based composite material according to claim 1, characterized in that: The porosity of the straw biomass charcoal particles is 40-90%.

4. The method for preparing the calcium-based composite material according to claim 1, characterized in that: The loading amount of calcium peroxide on biochar is 30-80g / 100gC.

5. The method for preparing the calcium-based composite material according to claim 1, characterized in that: The calcium hydroxide-containing mineral is one or a mixture of calcium oxide, calcium hydroxide, carbide slag or red mud.

6. The method for preparing the calcium-based composite material according to claim 1, characterized in that: The mass ratio of the calcium peroxide-loaded biochar particles to the calcium hydroxide-containing minerals in the calcium-based composite material is 3 to 5:

1.

7. The calcium-based composite material prepared according to the method according to any one of claims 1 to 6.

8. The use of the calcium-based composite material according to claim 7, characterized in that: The calcium-based composite material is added to the dried sludge, and then a lignin binder is added, and then the sludge is pressed and shaped, and then pyrolysis and carbonization are performed.

9. The use according to claim 8, characterized in that The addition amount of the calcium-based composite material accounts for 5-15wt.% of the dry sludge mass; the addition amount of the lignin binder accounts for 5-15wt.% of the dry sludge mass.

10. The use according to claim 8, characterized in that The lignin binder is lignin or lignin residue after straw hydrolysis.