A method for efficiently catalyzing and oxidizing calcium sulfite in desulfurization ash by a hydrothermal method

Abstract

The application discloses a kind of high-efficiency catalytic oxidation desulfurization ash calcium sulfite method of hydrothermal method, by with steel slag powder and copper sulfate catalyst in lower temperature hydrothermal condition to semi-dry method desulfurization ash unstable sulfite SO3 2‑ Catalytic oxidation is carried out, which can significantly reduce the content of unstable sulfite SO3 2‑ In semi-dry method desulfurization ash, so that it can be better applied in the field of building materials, has higher stability. At the same time, since steel slag powder belongs to solid waste, the cost is low, and the amount of catalyst can be reduced, which is a waste-to-waste treatment method for low-cost and efficient conversion of CaSO3 in desulfurization ash at low temperature, which is beneficial to the resource utilization of desulfurization ash and steel slag, and has important significance for environment and sustainable development.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of resource utilization of industrial solid waste, and particularly relates to a method for efficiently catalytically oxidizing calcium sulfite in desulfurization ash by a hydrothermal method. BACKGROUND

[0002] The semi-dry desulfurization ash is a byproduct of the semi-dry sintering flue gas desulfurization process, and its composition is very complex, especially containing unstable calcium sulfite (CaSO3) which will gradually oxidize into calcium sulfate in the natural environment, causing volume expansion. If the semi-dry desulfurization ash is directly used to produce building materials, the quality of the products will be affected. Therefore, the semi-dry desulfurization ash is a difficult-to-treat industrial solid waste, and is mainly disposed by piling up and discarding, causing waste of resources and space.

[0003] In order to solve the instability problem of the semi-dry desulfurization ash, it is necessary to convert the unstable CaSO3 into stable CaSO4. A large number of studies have found that in order to obtain a high conversion efficiency, a catalytic oxidation reaction needs to be carried out under the conditions of high temperature, water and catalyst. However, on the one hand, CaSO3 will decompose SO2 at high temperature, thereby polluting the environment; on the other hand, a large amount of catalyst needs to be used in the catalytic oxidation reaction, which greatly increases the cost of desulfurization ash treatment, and brings great limitation to the resource utilization of the desulfurization ash. Therefore, it is necessary to develop a method for low-cost and efficient conversion of CaSO3 in desulfurization ash at a lower temperature. SUMMARY

[0004] Based on the technical problems existing in the background art, the present application provides a method for efficiently catalytically oxidizing calcium sulfite in desulfurization ash by a hydrothermal method.

[0005] The method for efficiently catalytically oxidizing calcium sulfite in desulfurization ash by a hydrothermal method provided by the present application can be carried out by mixing the semi-dry desulfurization ash with steel slag powder and copper sulfate and then carrying out a hydrothermal reaction.

[0006] Preferably, the content of CaSO3 in the semi-dry desulfurization ash is 10-15wt%.

[0007] Preferably, the content of Fe2O3 in the steel slag powder is 20-30wt%.

[0008] Preferably, the mass ratio of the steel slag powder to the semi-dry desulfurization ash is (1-1.5):1.

[0009] Preferably, the mass of the copper sulfate is 0.3-0.6% of the mass of the semi-dry desulfurization ash.

[0010] Preferably, the temperature of the hydrothermal reaction is 100-150℃.

[0011] Preferably, the time of the hydrothermal reaction is ≥24h.

[0012] The application further discloses a building cementing material, which is obtained by drying the solid substance after the product obtained by the method is subjected to solid-liquid separation.

[0013] The application has the following beneficial effects:

[0014] Steel slag is a by-product of the steelmaking process and also belongs to difficult-to-treat industrial solid waste. The fundamental reason restricting the large-scale resource utilization of steel slag is its poor stability, and the unstable component thereof is free calcium oxide (f-CaO), which will cause volume expansion after hydration. Steel slag has a certain oxidizing property, and the content of iron oxide is usually used to represent the oxidizing capacity thereof. Unstable sulfite SO3 2- in semi-dry desulfurization ash is easily oxidized by iron ions with oxidizing property in steel slag under hydrothermal conditions at high temperature and high pressure, and is thus converted into stable sulfate SO4 2- On this basis, the application can catalyze and promote the oxidation reaction by adding an appropriate amount of specific catalyst copper sulfate, which can have a synergistic effect with the effective catalytic and oxidizing components in steel slag powder, greatly improve the conversion rate of CaSO3 in semi-dry desulfurization ash, and even achieve the effect of complete conversion of CaSO3. Meanwhile, the unstable f-CaO in steel slag can be fully hydrated under hydrothermal conditions at high temperature and high pressure, and thus be eliminated.

[0015] In summary, the application catalyzes and oxidizes the unstable sulfite SO3 2- in semi-dry desulfurization ash under hydrothermal conditions at a lower temperature by using steel slag powder and copper sulfate catalyst, obtains semi-dry desulfurization ash without CaSO3, and makes the semi-dry desulfurization ash have higher long-term stability and be better applicable to the field of building materials. Meanwhile, since steel slag powder belongs to solid waste and has low cost, the amount of catalyst can be reduced, and the application is a waste-to-waste treatment method for efficiently converting CaSO3 in desulfurization ash at a lower cost under a lower temperature, which is conducive to the resource utilization of desulfurization ash and steel slag, and has important significance for the environment and sustainable development. DETAILED DESCRIPTION

[0016] Hereinafter, the technical solutions of the application will be described in detail through specific embodiments.

[0017] Embodiment 1

[0018] 0.9 g of semi-dry desulfurization ash with a CaSO3 content of 12 wt% is weighed, 0.9 g of steel slag powder with an Fe2O3 content of 25 wt% and an f-CaO content of 4.3% and 0.0045 g of copper sulfate are added and uniformly mixed, and then placed in a hydrothermal kettle, 30 mL of water is added, the kettle cover is tightened, and the hydrothermal reaction is carried out in a 150℃ oven for 24 h.

[0019] Example 2

[0020] Take 0.9 g of semi-dry desulfurization ash with CaSO3 content of 12wt%, add 1.35 g of steel slag powder with Fe2O3 content of 25wt% and f-CaO content of 4.3%, and 0.0045 g of copper sulfate, mix uniformly, then place in an autoclave, add 30 mL of water, tighten the cover, and place in a 150°C oven for hydrothermal reaction for 24 h.

[0021] Example 3

[0022] Take 0.9 g of semi-dry desulfurization ash with CaSO3 content of 10wt%, add 1 g of steel slag powder with Fe2O3 content of 20wt% and f-CaO content of 1%, and 0.0027 g of copper sulfate, mix uniformly, then place in an autoclave, add 30 mL of water, tighten the cover, and place in a 100°C oven for hydrothermal reaction for 24 h.

[0023] Example 4

[0024] Take 0.9 g of semi-dry desulfurization ash with CaSO3 content of 15wt%, add 1 g of steel slag powder with Fe2O3 content of 30wt% and f-CaO content of 5%, and 0.0054 g of copper sulfate, mix uniformly, then place in an autoclave, add 30 mL of water, tighten the cover, and place in a 120°C oven for hydrothermal reaction for 24 h.

[0025] Example 5

[0026] A building cementitious material is obtained by filtering and drying the hydrothermal reaction product obtained in Example 1.

[0027] Example 6

[0028] A building cementitious material is obtained by filtering and drying the hydrothermal reaction product obtained in Example 2.

[0029] Comparative Example 1

[0030] Take 0.9 g of semi-dry desulfurization ash with CaSO3 content of 12wt%, place in an autoclave, add 30 mL of water, tighten the cover, and place in a 150°C oven for hydrothermal reaction for 24 h.

[0031] Comparative Example 2

[0032] Take 0.9 g of semi-dry desulfurization ash with CaSO3 content of 12wt%, add 4 g of steel slag powder with Fe2O3 content of 25wt% and f-CaO content of 4.3%, and 0.0045 g of copper sulfate, mix uniformly, then add 30 mL of water, stand for aging for 24 h, then filter and dry.

[0033] Comparative Example 3

[0034] 0.9 g of semi-dry desulfurization ash with a CaSO3 content of 12 wt% was weighed, 4 g of steel slag powder with a Fe2O3 content of 25 wt% and a f-CaO content of 4.3% was added and mixed uniformly, and then 0.0045 g of copper sulfate was added and mixed uniformly. Then, the mixture was kept at 150°C, and after cooling, it was ready.

[0035] Comparative Example 4

[0036] 0.9 g of semi-dry desulfurization ash with a CaSO3 content of 12 wt% was weighed, 4 g of steel slag powder with a Fe2O3 content of 25 wt% and a f-CaO content of 4.3% was added and mixed uniformly, and then the mixture was placed in an autoclave, 30 mL of water was added, the cover was tightened, and the autoclave was placed in an oven at 150°C for hydrothermal reaction for 24 h, and then it was ready.

[0037] Comparative Example 5

[0038] 0.9 g of semi-dry desulfurization ash with a CaSO3 content of 12 wt% was weighed, 4 g of steel slag powder with a Fe2O3 content of 25 wt% and a f-CaO content of 4.3% was added and mixed uniformly, and then 0.0045 g of iron sulfate was added and mixed uniformly. Then, the mixture was placed in an autoclave, 30 mL of water was added, the cover was tightened, and the autoclave was placed in an oven at 150°C for hydrothermal reaction for 24 h, and then it was ready.

[0039] Comparative Example 6

[0040] 0.9 g of semi-dry desulfurization ash with a CaSO3 content of 12 wt% was weighed, 4 g of steel slag powder with a Fe2O3 content of 25 wt% and a f-CaO content of 4.3% was added and mixed uniformly, and then 0.0045 g of manganese sulfate was added and mixed uniformly. Then, the mixture was placed in an autoclave, 30 mL of water was added, the cover was tightened, and the autoclave was placed in an oven at 150°C for hydrothermal reaction for 24 h, and then it was ready.

[0041] Comparative Example 7

[0042] 0.9 g of semi-dry desulfurization ash with a CaSO3 content of 12 wt% was weighed, 4 g of steel slag powder with a Fe2O3 content of 25 wt% and a f-CaO content of 4.3% was added and mixed uniformly, and then 0.0045 g of nickel sulfate was added and mixed uniformly. Then, the mixture was placed in an autoclave, 30 mL of water was added, the cover was tightened, and the autoclave was placed in an oven at 150°C for hydrothermal reaction for 24 h, and then it was ready.

[0043] Comparative Example 8

[0044] 0.9 g of semi-dry desulfurization ash with a CaSO3 content of 12 wt% was weighed, 4 g of steel slag powder with a Fe2O3 content of 25 wt% and a f-CaO content of 4.3% was added and mixed uniformly, and then 0.0045 g of zinc sulfate was added and mixed uniformly. Then, the mixture was placed in an autoclave, 30 mL of water was added, the cover was tightened, and the autoclave was placed in an oven at 150°C for hydrothermal reaction for 24 h, and then it was ready.

[0045] Test case

[0046] The impurity content in the desulfurization ash and steel slag powder treated in Examples 1-4 and Comparative Examples 1-8 was tested respectively, and the results are shown in Tables 1 and 2:

[0047] Table 1

[0048]

[0049]

[0050] Table 2

[0051]

[0052] The experimental results show that by adding steel slag and copper sulfate to semi-dry desulfurization ash and then using a hydrothermal synergistic catalytic oxidation method, the CaSO3 in the semi-dry desulfurization ash can be completely converted into CaSO4, and the f-CaO in the steel slag is completely eliminated. The product treated by this invention is completely free of unstable components f-CaO and CaSO3, and can be directly used as a building cementitious material with excellent long-term stability.

[0053] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for the high-efficiency hydrothermal catalytic oxidation of calcium sulfite in desulfurization ash, characterized in that, The semi-dry desulfurization ash is mixed with steel slag powder and copper sulfate, and then subjected to a hydrothermal reaction; the hydrothermal reaction temperature is 100~150℃ and the time is ≥24h. The CaSO3 content in the semi-dry desulfurization ash is 10~15 wt%; The Fe2O3 content in the steel slag powder is 20~30 wt%; The mass ratio of the steel slag powder to the semi-dry desulfurization ash is (1~1.5):1; The mass of the copper sulfate is 0.3 to 0.6% of the mass of the semi-dry desulfurization ash.

2. A building cementitious material, characterized in that, The product obtained by the method described in claim 1 is obtained by solid-liquid separation and drying of the solid material.

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