CN114873599A - Method for preparing calcium silicate from desulfurized gypsum - Google Patents
Method for preparing calcium silicate from desulfurized gypsum Download PDFInfo
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- CN114873599A CN114873599A CN202210650580.3A CN202210650580A CN114873599A CN 114873599 A CN114873599 A CN 114873599A CN 202210650580 A CN202210650580 A CN 202210650580A CN 114873599 A CN114873599 A CN 114873599A
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- desulfurized gypsum
- calcium silicate
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- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/20—Silicates
- C01B33/24—Alkaline-earth metal silicates
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- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
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- C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
- C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
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Abstract
The invention provides a method for preparing calcium silicate by using desulfurized gypsum, and relates to the technical field of solid waste recycling treatment. The preparation method takes the desulfurized gypsum as a raw material and realizes the preparation of calcium silicate through the steps of drying, mixing, pelletizing, roasting and the like. The method utilizes the silicon carbide to obviously reduce the decomposition temperature and the treatment energy consumption of the desulfurized gypsum, simultaneously reduces the requirements on production equipment, obtains the calcium silicate capable of being used as a building material, and realizes the high-efficiency recovery of sulfur resources in the desulfurized gypsum.
Description
Technical Field
The invention relates to the technical field of solid waste recycling treatment, in particular to a method for preparing calcium silicate from desulfurized gypsum.
Background
The desulfurized gypsum is used for removing SO in sulfur-containing waste gas in industrial production 2 The generated by-product, namely the desulfurized gypsum in China, mainly comes from coal-fired power plants and the steel industry. In recent years, with the increasing demand of electricity and steel output in China, the pressure of treating sulfur-containing waste gas is increasing. The calcium-based wet Flue Gas Desulfurization (FGD) is one of the most widely used, economically and environmentally friendly treatment technologies, and blows sulfur-containing flue gas into a lime-limestone mixture, in which SO is generated 2 And Ca (OH) 2 Reacting and oxidizing to generate calcium sulfate to obtain the hydrous desulfurized gypsumThe main component is similar to natural gypsum, generally CaSO 4 ·2H 2 And O. FGD technology for treating one ton of SO 2 2.7 tons of desulfurized gypsum are generated, while China is a large country mainly for steel production and coal-fired thermal power generation, and the quantity of the desulfurized gypsum generated per year exceeds 1 hundred million tons. Therefore, the reasonable utilization of the desulfurized gypsum which is a huge solid waste resource is very important.
At present, the current situation of desulfurized gypsum treatment in the steel industry of China is mainly direct stacking or landfill, which not only occupies precious land resources and threatens environmental safety, but also wastes sulfur resources greatly. The acid preparation and the cement co-production are one of the utilization modes of the desulfurized gypsum, namely SO is decomposed by utilizing high temperature 2 And CaO, SO 2 The method is used for preparing sulfuric acid, and CaO is used for cement production. The characteristic of high direct calcination decomposition temperature of the desulfurized gypsum enables the treatment energy consumption to be very high, although a certain amount of carbon is added to reduce the decomposition temperature of calcium sulfate, liquid phase and CaS are easily generated at the calcination temperature of over 900 ℃, the air permeability of materials is affected, and the desulfurization effect is poor. And a large part of desulfurized gypsum is directly used as a material for building and roadbed backfilling, so that the sulfur resource in the desulfurized gypsum is not effectively recycled, and the resource is wasted.
Disclosure of Invention
In order to solve the problems, the invention provides a method for preparing calcium silicate by using desulfurized gypsum so as to solve the problems of huge stockpiling amount and low utilization rate of sulfur-containing gypsum. The method for preparing calcium silicate by using desulfurized gypsum comprises the following steps:
(1) and (3) drying: respectively drying the desulfurized gypsum and the silicon carbide;
(2) mixing materials: mixing the dried desulfurized gypsum and the silicon carbide, adding water, and carrying out ball milling to obtain a mixture;
(3) pelletizing: drying the mixture, adding water to pelletize, and drying the pellets after ageing for 24 hours;
(4) roasting: and roasting the dried pellets to obtain a calcium silicate-containing gypsum desulfurization product.
Further, CaSO in the desulfurized gypsum in the step (1) 4 ·0.5H 2 Content of O≧95％。
Further, the silicon carbide in the step (1) comprises SiC and SiC-Al 2 O 3 SiC-C or SiC-SiO 2 。
Further, the content of beta-SiC in the silicon carbide in the step (1) is more than or equal to 98 percent.
Further, the drying temperature in the step (1) is 70-90 ℃, and the drying time is 12-24 hours. Preferably, the drying temperature in the step (1) is 75-85 ℃, and the drying time is 16-18 h.
Further, in the step (2), the weight ratio of the desulfurized gypsum to the silicon carbide is 5-8:2-5, and the addition amount of water is 5-10% of the total weight of the desulfurized gypsum and the silicon carbide.
Further, the mass ratio of the material balls in the step (2) is 2: 1, the ball milling time is 3-6 h, and the ball milling speed is 90-120 r/min. Preferably, the ball milling speed in the step (2) is 100 r/min.
Further, the adding amount of water in the step (3) is 5-10% of the total weight of the mixture, the diameter of the pellets is 5-8 mm, the drying temperature is 55-65 ℃, and the drying time is 12-24 h. Preferably, the drying time in the step (3) is 12-24 h.
Further, in the step (4), the roasting temperature is 800-1200 ℃, the heating rate is 5 ℃/min, and the heat preservation time is 1-3 h. Preferably, the roasting temperature in the step (4) is 800-1000 ℃.
Further, the roasting process of the step (4) is performed under an air atmosphere, a nitrogen atmosphere, a carbon monoxide atmosphere or a hydrogen atmosphere.
Compared with the prior art, the invention has the beneficial technical effects that:
(1) according to the invention, by adding the silicon carbide with reducibility, the decomposition temperature and the treatment energy consumption of the desulfurized gypsum are reduced, and the requirements on production equipment are reduced;
(2) the invention avoids the problems of influence on material permeability, poor desulfurization effect and the like caused by easy generation of liquid phase and CaS in the roasting process of the desulfurized gypsum;
(3) the method has the advantages that a large amount of sulfur resources in the desulfurized gypsum are efficiently recovered, and the potential threat to the environment is reduced;
(4) the invention obtains calcium silicate which is a gypsum desulfurization product with high added value, and the calcium silicate can be widely used as a building material.
Drawings
The invention is further illustrated in the following description with reference to the drawings.
FIG. 1 is a process flow for preparing calcium silicate from desulfurized gypsum according to the present invention;
FIG. 2 is an XRD pattern of a sample obtained in example 1 of the present invention;
FIG. 3 is an XRD pattern of a sample obtained in example 2 of the present invention;
FIG. 4 is an XRD pattern of a sample obtained in example 3 of the present invention;
FIG. 5 is an XRD pattern of a sample obtained in example 5 of the present invention.
Detailed Description
The invention provides a method for preparing calcium silicate by using desulfurized gypsum, which comprises the following steps:
(1) and (3) drying: respectively drying the desulfurized gypsum and the silicon carbide;
(2) mixing materials: mixing the dried desulfurized gypsum and the silicon carbide, adding water, and carrying out ball milling to obtain a mixture;
(3) pelletizing: drying the mixture, adding water to pelletize, and drying the pellets after ageing for 24 hours;
(4) roasting: and roasting the dried pellets to obtain a calcium silicate-containing gypsum desulfurization product.
In one embodiment, CaSO is contained in the desulfurized gypsum in the step (1) 4 ·0.5H 2 The content of O is not less than 95%.
In one embodiment, the silicon carbide in step (1) is SiC or SiC-Al 2 O 3 SiC-C or SiC-SiO 2 。
In one embodiment, the content of the beta-SiC in the silicon carbide in the step (1) is more than or equal to 98 percent.
In one embodiment, the drying temperature in the step (1) is 70-90 ℃, and the drying time is 12-24 h.
In one embodiment, the drying temperature in the step (1) is 75-85 ℃, and the drying time is 16-18 h.
In one embodiment, the weight ratio of the desulfurized gypsum to the silicon carbide in the step (2) is 5-8:2-5, and the addition amount of the water is 5-10% of the total weight of the desulfurized gypsum and the silicon carbide.
In one embodiment, the mass ratio of the material balls in the step (2) is 2: 1, the ball milling time is 3-6 h, and the ball milling speed is 90-120 r/min.
In one embodiment, the ball milling speed in the step (2) is 100 r/min.
In one embodiment, the adding amount of the water in the step (3) is 5-10% of the total weight of the mixture, the diameter of the pellet is 5-8 mm, the drying temperature is 55-65 ℃, and the drying time is 12-24 h.
In one embodiment, the drying time in the step (3) is 12 to 24 hours.
In one embodiment, the roasting temperature in the step (4) is 800-1200 ℃, the heating rate is 5 ℃/min, and the heat preservation time is 1-3 h.
In one embodiment, the calcination temperature in the step (4) is 800 ℃ to 1000 ℃.
In one embodiment, the firing process of the step (4) is performed under an air atmosphere, a nitrogen atmosphere, a carbon monoxide atmosphere, or a hydrogen atmosphere.
The technical solution provided by the present invention is further illustrated by the following examples.
Example 1
Method for preparing calcium silicate from desulfurized gypsum
(1) The desulfurization gypsum and the silicon carbide are dried in a drying oven at 85 ℃ for 18 hours in advance, the dried desulfurization gypsum and the silicon carbide are mixed according to the mass ratio of 3:1, the mixture is put into a ball mill and fully mixed for 3 hours, and the rotating speed of the ball mill is 100 r/min; 5-8:2-5
(2) Adding 10% of water into the uniformly mixed sample to make pellets, wherein the diameter of the pellets is 5-7 mm, and then putting the pellets into a drying oven to dry for 20 hours at 60 ℃;
(3) and (3) placing the manufactured pellets into a muffle furnace to be roasted in the air atmosphere, setting the temperature rise rate to be 5 ℃/min, selecting the roasting temperature to be 950 ℃, and preserving the heat for 1h at the highest temperature.
Through detection, the desulfurization rate of the roasted product is 67%, and the yield of calcium silicate is 69% of the theoretical value. XRD analysis of the product was carried out, and the results are shown in FIG. 2. As can be seen from FIG. 2, CaSiO was produced in a large amount in the sample 3 Phase, also a certain content of CaSO is present 4 It is shown that under the condition, the desulfurization achieves obvious effect, but the desulfurization is not thorough.
Example 2
The difference from example 1 is that: the mass ratio of the desulfurized gypsum to the silicon carbide is 2: 1.
The detection shows that the desulfurization rate of the roasted product is 84 percent, and the yield of the calcium silicate is 87 percent of the theoretical value. XRD analysis of the product was carried out, and the results are shown in FIG. 3. As can be seen from FIG. 3, CaSiO was produced in a large amount in the sample 3 Phase, CaSO 4 The amount of the additive is small, which shows that the desulfurization effect is obvious and thorough under the condition, and the addition amount of the SiC is proper.
Example 3
The difference from example 1 is that: the mass ratio of the desulfurized gypsum to the silicon carbide is 1: 1.
The detection shows that the desulfurization rate of the roasted product is 95 percent, and the yield of the calcium silicate is 98 percent of the theoretical value. XRD analysis of the product was carried out, and the results are shown in FIG. 4. As can be seen from FIG. 4, CaSiO was produced in a large amount in the sample 3 Phase, CaSO 4 The amount of the catalyst is small, so that the desulfurization effect is obvious and thorough under the condition, but the addition of the SiC is excessive.
Example 4
(1) Before mixing and sample preparation, firstly drying the desulfurized gypsum and the silicon carbide in a drying oven at 85 ℃ for 18 hours in advance, mixing the dried desulfurized gypsum and the silicon carbide according to the mass ratio of 3:1, putting the mixture into a ball mill, and fully and uniformly mixing the mixture for 3 hours, wherein the rotating speed of the ball mill is 100 r/min;
(2) adding 10% of water into the uniformly mixed sample to make pellets, wherein the diameter of the pellets is 6-8 mm, and then putting the pellets into a drying oven to dry for 20 hours at 60 ℃;
(3) and (3) placing the well-made pellets into a muffle furnace to be roasted in the air atmosphere, wherein the heating rate is 5 ℃/min, the roasting temperature is 850 ℃, and the heat preservation is carried out for 1h at the highest temperature.
The detection shows that the desulfurization rate of the roasted product is 49 percent, and the yield of the calcium silicate is 50 percent of the theoretical value.
Example 5
The difference from example 4 is that: the mass ratio of the desulfurized gypsum to the silicon carbide is 2: 1.
The detection shows that the desulfurization rate of the roasted product is 56 percent, and the yield of the calcium silicate is 58 percent of the theoretical value. XRD analysis of the product was carried out, and the results are shown in FIG. 5. As can be seen from FIG. 5, CaSiO was produced in a large amount in the sample 3 Not much phase, SiC and CaSO 4 The existence of a large amount of the sulfur-containing catalyst proves that the good desulfurization effect can be obtained at 850 ℃.
Example 6
The difference from example 4 is that: the mass ratio of the desulfurized gypsum to the silicon carbide is 1: 1.
Through detection, the desulfurization rate of the roasted product is 65%, and the yield of calcium silicate is 66% of the theoretical value.
The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.
Claims (10)
1. A method for preparing calcium silicate from desulfurized gypsum is characterized by comprising the following steps:
(1) and (3) drying: respectively drying the desulfurized gypsum and the silicon carbide;
(2) mixing materials: mixing the dried desulfurized gypsum and the silicon carbide, adding water, and carrying out ball milling to obtain a mixture;
(3) pelletizing: drying the mixture, adding water for pelletizing, and drying after the pellets are aged for 24 hours;
(4) roasting: and roasting the dried pellets to obtain a calcium silicate-containing gypsum desulfurization product.
2. The method for preparing calcium silicate from desulfurized gypsum according to claim 1, wherein CaSO is contained in desulfurized gypsum of step (1) 4 ·0.5H 2 The content of O is more than or equal to 95 percent.
3. The method for preparing calcium silicate from desulfurized gypsum according to claim 1, wherein the silicon carbide in step (1) is SiC or SiC-Al 2 O 3 SiC-C or SiC-SiO 2 。
4. The method for preparing calcium silicate from desulfurized gypsum according to claim 1, wherein the content of β -SiC in the silicon carbide in the step (1) is not less than 98%.
5. The method for preparing calcium silicate from desulfurized gypsum according to claim 1, wherein the drying temperature in step (1) is 70 ℃ to 90 ℃ and the drying time is 12h to 24 h.
6. The method for preparing calcium silicate from desulfurized gypsum according to claim 1, wherein the weight ratio of desulfurized gypsum to silicon carbide in step (2) is 5-8:2-5, and the amount of water added is 5-10% of the total weight of desulfurized gypsum and silicon carbide.
7. The method for preparing calcium silicate from desulfurized gypsum according to claim 1, wherein the mass ratio of the pellets in the step (2) is 2: 1, the ball milling time is 3-6 h, and the ball milling speed is 90-120 r/min.
8. The method for preparing calcium silicate from desulfurized gypsum according to claim 1, wherein the amount of water added in step (3) is 5% -10% of the total weight of the mixture, the diameter of the pellets is 5 mm-8 mm, the drying temperature is 55 ℃ -65 ℃, and the drying time is 12 h-24 h.
9. The method for preparing calcium silicate from desulfurized gypsum according to claim 1, wherein the calcination temperature in step (4) is 800-1200 ℃, the heating rate is 5 ℃/min, and the holding time is 1-3 h.
10. The method for preparing calcium silicate from desulfurized gypsum according to claim 1, wherein the calcination process of step (4) is carried out in an air atmosphere, a nitrogen atmosphere, a carbon monoxide atmosphere or a hydrogen atmosphere.
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Citations (4)
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| CN101041439A (en) * | 2007-03-01 | 2007-09-26 | 武汉理工大学 | Method for preparing grammite and sulfuric acid by employing waste slag phosphogypsum |
| CN103864024A (en) * | 2014-03-17 | 2014-06-18 | 武汉科技大学 | Method for catalytic decomposition of phosphogypsum |
| CN107162010A (en) * | 2017-05-25 | 2017-09-15 | 内蒙古仁创沙漠资源利用研究院有限公司 | The hydrated calcium silicate for synthesizing the method for hydrated calcium silicate and being synthesized by this method |
| CN108821300A (en) * | 2018-08-06 | 2018-11-16 | 东北大学 | One kind preparing CaSiO by discarded silicon slag3Method |
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- 2022-06-09 CN CN202210650580.3A patent/CN114873599A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101041439A (en) * | 2007-03-01 | 2007-09-26 | 武汉理工大学 | Method for preparing grammite and sulfuric acid by employing waste slag phosphogypsum |
| CN103864024A (en) * | 2014-03-17 | 2014-06-18 | 武汉科技大学 | Method for catalytic decomposition of phosphogypsum |
| CN107162010A (en) * | 2017-05-25 | 2017-09-15 | 内蒙古仁创沙漠资源利用研究院有限公司 | The hydrated calcium silicate for synthesizing the method for hydrated calcium silicate and being synthesized by this method |
| CN108821300A (en) * | 2018-08-06 | 2018-11-16 | 东北大学 | One kind preparing CaSiO by discarded silicon slag3Method |
Non-Patent Citations (3)
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| 张延大;: "风积沙制备水化硅酸钙的工艺研究", 中国非金属矿工业导刊, no. 04, pages 6 - 8 * |
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| 鲁海琳: "脱硫石膏制备硅酸盐水泥的研究", 中国优秀硕士学位论文全文数据库（电子期刊）工程科技Ⅰ辑, no. 6, pages 015 - 115 * |
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