Calcium-based composite material, method for its production and use

Abstract

The application discloses a calcium-based composite material and a preparation method and application thereof, and comprises the following steps: cleaning and drying high-porosity straw biomass charcoal particles; mixing the biomass charcoal particles with calcium peroxide, and making the powder calcium peroxide enter the pores of the biomass charcoal by vibration to obtain biomass charcoal loaded with calcium peroxide; mixing the biomass charcoal particles loaded with calcium peroxide and calcium hydroxide-containing minerals in a certain proportion to obtain the calcium-based composite material; the calcium-based composite material is added into dried sludge, the adding amount is 5-15 wt.% of the mass of the dry base of the sludge, and then a lignin binder is added, and the sludge is pressed into a shape; in the pyrolysis process, the adding amount can reach a sulfur fixation rate of more than 60%, most of the nitrogen is converted into ammonia, and hydrogen cyanide is greatly reduced, so that the sludge pyrolysis is realized in a manner of synergistic sulfur fixation and nitrogen control, and the emission of pollution gas is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for realizing sulfur fixation and nitrogen control by calcium-based composite materials, in particular to a calcium-based composite material composed of calcium peroxide-loaded biomass charcoal particles and calcium hydroxide-containing minerals, and a method for realizing simultaneous sulfur fixation and nitrogen control in sludge pyrolysis. BACKGROUND

[0002] With the development of economic society and the improvement of sewage treatment capacity and standards, the production of sludge is rapidly increasing. Sludge contains not only a large amount of carbon, nitrogen, phosphorus, sulfur and other recyclable materials, but also a large amount of pathogenic bacteria, microplastics and heavy metals, 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 "Sludge Harmless Treatment and Resource Utilization Implementation Plan", which emphasizes the harmless and resource utilization of sludge. Sludge pyrolysis technology can eliminate pathogens, realize the conversion of sludge components, and maximize energy recovery, providing a harmless utilization method with great application prospects for sludge treatment.

[0003] Sludge contains a large amount of C, N, S, P and K elements. Under pyrolysis conditions, S and N in sludge are easily converted into sulfur-containing and nitrogen-containing gases such as H2S and HCN, increasing the risk of air pollution. By adding calcium hydroxide and / or calcium oxide during pyrolysis, sulfur can be converted into calcium sulfide and part of calcium sulfate, achieving sulfur fixation and reducing the release of H2S and other sulfur-containing pollutants. At the same time, HCN can be catalytically decomposed and nitrogen can be converted into NH3, thereby achieving sulfur fixation and resource conversion of nitrogen. However, due to the presence of water vapor during pyrolysis, part of the calcium sulfide is destabilized by water vapor and decomposes to produce H2S gas. On the other hand, conventional calcium hydroxide and / or calcium oxide materials are difficult to significantly reduce the release of HCN. SUMMARY

[0004] The purpose of the present application is to provide a calcium-based composite material, a preparation method and use thereof, aiming at the defects of the prior art.

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

[0006] (1) Select high-porosity straw biomass charcoal particles, wash and dry;

[0007] (2) Mix the biomass charcoal particles with calcium peroxide, so that the calcium peroxide powder enters the pores of the biomass charcoal, obtaining calcium peroxide-loaded biomass charcoal particles;

[0008] (3) Mix the calcium peroxide-loaded biomass charcoal particles and calcium hydroxide-containing minerals in a certain proportion to obtain a calcium-based composite material.

[0009] Further, the straw biomass charcoal raw material is organic waste or sawdust, preferably wheat, corn waste or sawdust.

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

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

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

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

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

[0015] The third aspect of the present application provides the use of the calcium-based composite material, which is added to the dried sludge, and then a lignin binder is added, and after being pressed into a shape, pyrolysis carbonization is performed.

[0016] Further, the addition amount of the calcium-based composite material accounts for 5-15 wt.% of the dry basis mass of the sludge; and the addition amount of the lignin binder accounts for 5-15 wt.% of the dry basis mass of the sludge.

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

[0018] The novel calcium-based composite material provided by the present application 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 a calcium hydroxide-containing mineral. The calcium peroxide is loaded in the pores of the high-porosity straw biochar particles, and in the pyrolysis, the slow oxygen release of the calcium peroxide can be realized, which is beneficial to the oxidation of sulfur elements into more stable sulfate under the joint action of calcium hydroxide, effectively improving the pyrolysis sulfur fixation efficiency. At the same time, the active CaO produced by the decomposition of calcium peroxide and the catalytic effect of calcium hydroxide in the calcium-based composite material are used to control the directional conversion of nitrogen into NH3 and the decomposition and conversion of HCN in the sludge pyrolysis process. NH3 in the pyrolysis gas can be recycled in the pyrolysis gas purification link. In the sludge pyrolysis, the synergistic sulfur fixation and nitrogen control by the novel calcium-based composite material improve the sulfur fixation efficiency, effectively reduce the emission of pollutant gases, realize the recovery of valuable elements, and have broad commercial application potential.

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

[0020] 1. The calcium-based composite material disclosed in the application uses raw materials that are easy to obtain and has low dosage, which can significantly enhance the effect of sulfur fixation and nitrogen control in sludge pyrolysis.

[0021] 2. The calcium-based composite material provided by the application uses straw biochar particles as a carrier for calcium peroxide, which can load a large amount of calcium peroxide in the pores of the biochar, so that the biochar particles loaded with calcium peroxide become slow oxygen release agents in the pyrolysis process. After calcium peroxide releases oxygen, the product calcium oxide reacts with sulfur generated by sludge pyrolysis to form calcium sulfide, which is further oxidized to more stable calcium sulfate by the oxygen released by calcium peroxide, thereby improving 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 generated by the subsequent decomposition of the loaded calcium peroxide can catalyze the decomposition of HCN, converting HCN into NH3. The generated NH3 can be recycled in the pyrolysis gas purification link. The use of the calcium-based composite material in sludge pyrolysis achieves the effect of sulfur fixation and nitrogen control, greatly reducing the emission of sulfur and nitrogen-containing pollutants. DETAILED DESCRIPTION

[0023] To make the purpose, technical solutions and advantages of the application clearer, the technical solutions of the application will be further described below.

[0024] Example 1

[0025] The method for realizing the synergistic sulfur fixation and nitrogen control in sludge pyrolysis using a calcium-based composite material selects biochar particles with a porosity of 60%, cleans and dries them, and loads calcium peroxide into the pores of the biochar by vibration mixing. The biochar loaded with calcium peroxide and the calcium hydroxide mineral are mixed in a mass ratio of 3:1 to obtain the calcium-based composite material. According to the different inorganic content of the dried sludge, 5-15 wt.% of the calcium-based composite material and 5-15 wt.% of the lignin binder are added to the sludge dry basis, and then the sludge is subjected to anaerobic pyrolysis treatment after being pressed and dried.

[0026] After pyrolysis, the sulfur fixation rate in the sludge is greater than 60%, and the nitrogen-containing gas products are mainly NH3 and HCN, of which the HCN yield decreases from 3.5% without calcium-based composite material to 0.8%.

[0027] Example 2

[0028] The biochar particles with a porosity of 70% are selected, washed and dried, and calcium peroxide is loaded into the pores of the biochar by vibration mixing. The biochar loaded with calcium peroxide and the 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 contents of the dried sludge, 5-15 wt.% of the calcium-based composite material and 5-15 wt.% of the lignin binder based on the dry mass of the sludge are added, and after compression molding and drying, anaerobic pyrolysis treatment is performed.

[0029] After pyrolysis, the sulfur retention rate in the sludge is greater than 62%, and the gaseous nitrogen-containing products are mainly NH3 and HCN, of which the HCN yield decreases from 3.5% without calcium-based composite material to 0.5%.

[0030] Example 3

[0031] The biochar particles with a porosity of 80% are selected, washed and dried, and calcium peroxide is loaded into the pores of the biochar by vibration mixing. The biochar loaded with calcium peroxide and the 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 contents of the dried sludge, 5-15 wt.% of the calcium-based composite material and 5-15 wt.% of the lignin binder based on the dry mass of the sludge are added, and after compression molding and drying, anaerobic pyrolysis treatment is performed.

[0032] After pyrolysis, the sulfur retention rate in the sludge is greater than 62%, and the gaseous nitrogen-containing products are mainly NH3 and HCN, of which the HCN yield decreases from 3.5% without calcium-based composite material to 0.5%.

[0033] In the above examples:

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

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

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

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

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

[0039] The calcium-based composite material is added at a dosage of 5-15 wt.% based on the dry mass of the sludge; and the lignin binder is added at a dosage of 5-15 wt.% based on the dry mass of the sludge.

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

[0041] The above are only preferred embodiments of the present application, and do not have any limiting effect on the present application. Any person skilled in the art can make any form of equivalent replacement, modification or change to the technical solutions and technical contents disclosed in the present application without departing from the scope of the technical solutions of the present application, and still belongs to the protection scope of the present application.

Claims

1. A method for preparing a calcium-based composite material, characterized in that, Includes the following steps: (1) Select high porosity straw biochar particles with a porosity of 40-90%, and clean and dry them; (2) The biochar particles obtained in step (1) are mixed with calcium peroxide powder, and the calcium peroxide is introduced into the pores of the biochar by vibration to obtain biochar particles loaded with calcium peroxide, wherein the loading amount of calcium peroxide is 30-80g / 100gC. (3) The calcium peroxide biochar particles obtained in step (2) and the calcium hydroxide minerals are mixed at a mass ratio of 3 to 5:1 to obtain a calcium-based composite material.

2. The preparation method according to claim 1, characterized in that, The raw materials for the straw biochar are wheat and corn waste or wood chips.

3. The preparation method according to claim 1, characterized in that, The calcium hydroxide-containing mineral is one or more of calcium oxide, calcium hydroxide, carbide slag, or red mud.

4. A calcium-based composite material prepared by the method according to any one of claims 1-3.

5. The use of the calcium-based composite material according to claim 4 in the synergistic sulfur fixation and nitrogen control process of dried sludge pyrolysis, characterized in that, include: The calcium-based composite material is added to the dried sludge at an amount of 5-15 wt.% of the dry sludge weight, and then lignin binder is added at an amount of 5-15 wt.% of the dry sludge weight. After being pressed and molded, the mixture is subjected to anaerobic pyrolysis carbonization. The pyrolysis process achieves a sulfur fixation rate of more than 60% and reduces the HCN yield to below 0.8%.

6. The use according to claim 5, characterized in that, The lignin binder is the lignin residue after straw hydrolysis.