阅读说明：本技术 一种炼钢除尘灰中游离氧化钙的消解方法 (Method for digesting free calcium oxide in steelmaking fly ash ) 是由 任张超 于英杰 于 2020-08-12 设计创作，主要内容包括：本发明涉及固废处理技术领域,尤其涉及一种炼钢除尘灰中游离氧化钙的消解方法。该消解方法主要包括以下步骤：将炼钢除尘灰置于消解容器中,用二氧化碳置换消解容器中的气体,然后注入饱和水蒸气,在特定压力和温度条件下消解,再用预冷的二氧化碳置换消解容器内的气体并降温。该消解方法不需要过高的反应温度和压力,且所需反应时间更短,消解效率高,有利于在生产中实现对炼钢除尘灰的规模化消解。消解后所得炼钢除尘灰粒度分布均匀,且单质铁不会在消解过程中被过多氧化,便于炼钢除尘灰的资源化利用和其中单质铁的回收。(The invention relates to the technical field of solid waste treatment, in particular to a digestion method of free calcium oxide in steelmaking fly ash. The digestion method mainly comprises the following steps: and (3) placing the steelmaking fly ash into a digestion container, replacing gas in the digestion container with carbon dioxide, then injecting saturated steam, digesting under the conditions of specific pressure and temperature, replacing the gas in the digestion container with precooled carbon dioxide, and cooling. The digestion method does not need overhigh reaction temperature and pressure, has shorter reaction time and high digestion efficiency, and is beneficial to realizing the large-scale digestion of the steelmaking fly ash in production. The steelmaking fly ash obtained after digestion has uniform particle size distribution, and the simple substance iron is not oxidized too much in the digestion process, thereby facilitating the resource utilization of the steelmaking fly ash and the recovery of the simple substance iron.)

1. A digestion method of free calcium oxide in steelmaking fly ash is characterized by comprising the following steps:

s1, placing the steelmaking fly ash into a digestion container, and replacing gas in the digestion container with carbon dioxide until the oxygen content in the gas in the digestion container is less than 1% v/v;

s2, injecting saturated water vapor into the digestion container and adjusting the concentration of carbon dioxide to ensure that the molar weight of water molecules in the saturated water vapor is 50-80% of the molar weight of the carbon dioxide, and the pressure in the digestion container is 0.16-0.2 MPa;

s3, raising the temperature in the digestion container to 150-250 ℃, keeping the temperature for 15-30 min, replacing the gas in the digestion container with carbon dioxide precooled to 5-10 ℃ under the condition that the pressure in the digestion container is kept to be 0.16-0.2 MPa, and cooling the steelmaking dedusting ash to 60-80 ℃.

2. The method for digesting free calcium oxide in steelmaking fly ash according to claim 1, wherein the method for replacing gas in the digestion vessel with carbon dioxide is: and injecting carbon dioxide after vacuumizing the digestion container, and repeating the operation until the oxygen content in the gas in the digestion container is less than 1% v/v.

3. The method for digesting free calcium oxide in steelmaking fly ash according to claim 1, wherein a stirring device is provided in said digestion vessel, and said operation of injecting saturated steam in S2 is performed under stirring.

4. The method for digesting free calcium oxide in steelmaking fly ash according to claim 1, wherein the temperature rise rate in S3 is 50-80 ℃/min.

5. The method for digesting free calcium oxide in steelmaking fly ash according to claim 1, wherein the temperature reduction rate in S3 is 90-110 ℃/min.

6. The method for digesting free calcium oxide in steelmaking fly ash according to any one of claims 1 to 5, wherein the method further comprises S4, and the operation of S4 is as follows: when the steelmaking dust removal ash is kept at 60-80 ℃ for 10-15 min, introducing saturated steam, so that the molar weight of water molecules in the saturated steam is 35-45% of the molar weight of the carbon dioxide; and (3) heating to 110-120 ℃, keeping the temperature for 15-30 min, replacing gas in the digestion container with carbon dioxide precooled to 2-5 ℃, and cooling the steelmaking precipitator dust to 20-40 ℃.

7. The method for digesting free calcium oxide in steelmaking fly ash according to claim 6, wherein the temperature rise rate is 60-90 ℃/min.

8. The method for digesting free calcium oxide in steelmaking fly ash according to claim 6, wherein the rate of temperature reduction is 100-120 ℃/min.

Technical Field

The invention relates to the technical field of solid waste treatment, in particular to a digestion method of free calcium oxide in steelmaking fly ash.

Background

The steelmaking fly ash is a byproduct in the steelmaking process and can be used as a concrete admixture or aggregate for building materials. However, the steelmaking fly ash contains more free calcium oxide (f-CaO), so that the steelmaking fly ash is easy to absorb water to generate volume expansion, and the steelmaking fly ash expands and pulverizes during hydrolysis to increase the volume by 1-2 times, so that the steelmaking fly ash can crack concrete engineering, roads, building material products and the like when being used as a building material, and therefore, the steelmaking fly ash needs to be cleared up the free calcium oxide during resource utilization.

At present, the traditional digestion methods mainly comprise a hot splashing method, a water quenching method, an air quenching method, a hot stewing method and the like. Compared with other methods, the heat stewing method has the advantages of shortest required time, strong adaptability and minimum requirement on operation space. However, free calcium oxide in the steelmaking fly ash is generally generated by the early-stage reaction of steelmaking₂S, etc. of the package, C₂S and free calcium oxide are compact in structure, so that even if a hot stewing method is adopted, the content of the free calcium oxide can be reduced to below 2% within 2 to several hours under the high-temperature condition and high-pressure environment of hundreds of ℃ and the high-temperature and high-pressure resistance of equipment is high, and certain potential safety hazards exist in high-temperature and high-pressure operation. The iron in the steelmaking fly ash is oxidized in the high-temperature and high-pressure hot stewing process, so that the phase composition is changed, and the raw material stability and the iron recovery during the resource utilization are influenced. If the temperature or pressure adopted during the thermal stewing is low, dozens of hours or even days are needed to dissolve the content of the free calcium oxide to be less than 3 percent. Moreover, the product obtained by the hot-braising method has extremely uneven granularity and needs to consume a large amount of energy to be crushed in subsequent treatment.

Disclosure of Invention

Aiming at the problems that the digestion of the steelmaking fly ash needs long time, potential safety hazards exist at high temperature and high pressure, iron in the steelmaking fly ash can be oxidized, and the granularity of the obtained product is not uniform, the invention provides a digestion method of free calcium oxide in the steelmaking fly ash.

In order to achieve the purpose of the invention, the embodiment of the invention adopts the following technical scheme:

a digestion method of free calcium oxide in steelmaking fly ash specifically comprises the following steps:

s1, placing the steelmaking fly ash into a digestion container, and replacing gas in the digestion container with carbon dioxide until the oxygen content in the gas in the digestion container is less than 1% v/v;

s2, injecting saturated water vapor into the digestion container and adjusting the concentration of carbon dioxide to ensure that the molar weight of water molecules in the saturated water vapor is 50-80% of the molar weight of the carbon dioxide, and the pressure in the digestion container is 0.16-0.2 MPa;

s3, raising the temperature in the digestion container to 150-250 ℃, keeping the temperature for 15-30 min, replacing the gas in the digestion container with carbon dioxide precooled to 5-10 ℃ under the condition that the pressure in the digestion container is kept to be 0.16-0.2 MPa, and cooling the steelmaking dedusting ash to 60-80 ℃.

Compared with the prior art, the digestion method adopted by the invention does not need overhigh reaction temperature and pressure, obviously reduces the requirement on equipment, has small potential safety hazard of production, needs shorter reaction time, and is more favorable for realizing large-scale digestion of steelmaking fly ash in production.

According to the digestion method, firstly, in S1, carbon dioxide is enabled to penetrate into the steelmaking fly ash in a mode of replacing gas in a digestion container by the carbon dioxide, on one hand, oxygen among steelmaking fly ash particles and in pores inside the particles can be replaced, and the oxidation of iron components in the steelmaking fly ash in the subsequent digestion process is reduced, on the other hand, when free calcium oxide generates calcium hydroxide when meeting water, the carbon dioxide can react with the obtained calcium hydroxide to generate calcium carbonate more quickly, the content of the free calcium oxide is reduced, and the unreacted calcium hydroxide can promote the fragmentation of a caking product;

then saturated steam is input in S2, the molar ratio of carbon dioxide to water can ensure that carbon dioxide and calcium hydroxide completely react, the hydrolysis degree of free calcium oxide is insufficient when the content of carbon dioxide is too high, and the water content of the reaction system is too low, so that the reaction is not easy to carry out; if the content of carbon dioxide is too low, the carbonation of calcium hydroxide can not be completely finished;

the pressure range of 0.16-0.2 MPa and the temperature range of 150-250 ℃ in S3 can promote the reaction of water molecules and free calcium oxide to generate calcium hydroxide, further the calcium hydroxide and carbon dioxide react to generate calcium carbonate, and the free calcium oxide is carbonated to be stabilized, and the obtained calcium carbonate is stable under the reaction conditions of the temperature and the pressure and is not easy to be decomposed into calcium oxide again;

make the dust removal ash caking and form the calcium hydroxide cover film on the surface after the water is met to free calcium oxide in steelmaking dust removal ash, hinder moisture further infiltration, this application is through dispelling the gas in the container with the carbon dioxide replacement of precooling in S3, can make the outside of caking product shrink fast, the moisture that stays on caking product surface continues to see through this cover film under 0.16 ~ 0.2 MPa' S pressure simultaneously and gets into inside free calcium oxide, react with calcium oxide and generate calcium hydroxide and expand, make the caking product cracked, make and clear up the reaction and continue to go on, thereby further reduce the content of free calcium oxide in the steelmaking dust removal ash.

The carbon dioxide in the method can be selected from carbon dioxide generated in the production of steel enterprises, so that the purposes of consuming carbon dioxide and reducing greenhouse gas emission in the process of digesting free carbon oxide are achieved, and the method is beneficial to green and environment-friendly production.

After the digestion by the digestion method, the content of free calcium oxide in the steelmaking fly ash can be reduced to below 1%, the particle size distribution is uniform, the subsequent direct utilization is convenient, the elemental iron cannot be excessively oxidized in the digestion process, and the elemental iron in the digested steelmaking fly ash can be recovered by means of magnetic separation and the like.

Preferably, the method of displacing gas in the digestion vessel with carbon dioxide is: and injecting carbon dioxide after vacuumizing the digestion container, and repeating the operation until the oxygen content in the gas in the digestion container is less than 1% v/v. The vacuumizing mode is more favorable for the deep penetration of carbon dioxide into the gaps in the steelmaking fly ash.

Preferably, a stirring device is arranged in the digestion vessel, and the operation of injecting saturated water vapor in S2 is carried out in a stirring state. Saturated steam is injected in the stirring state, so that the steelmaking fly ash can be more fully contacted with water and carbon dioxide, and the reaction is more thorough.

Preferably, the temperature rise rate in S3 is 50-80 ℃/min. In the digestion method, the temperature rising rate can obtain higher digestion efficiency.

Preferably, the cooling rate in S3 is 90-110 ℃/min. In the digestion method of the invention, the temperature reduction rate enables the particle size distribution of the obtained digestion product to be more uniform.

Preferably, the digestion method further comprises S4, and the operation of S4 is: when the steelmaking dust removal ash is kept at 60-80 ℃ for 10-15 min, introducing saturated steam, so that the molar weight of water molecules in the saturated steam is 35-45% of the molar weight of the carbon dioxide; and (3) heating to 110-120 ℃, keeping the temperature for 15-30 min, replacing gas in the digestion container with carbon dioxide precooled to 2-5 ℃, and cooling the steelmaking precipitator dust to 20-40 ℃. The operation can further digest the residual free calcium oxide, so that the content of calcium oxide in the obtained steelmaking fly ash is lower, and the recycling of the steelmaking fly ash is more convenient.

Preferably, the temperature rise rate is 60-90 ℃/min.

Preferably, the cooling rate is 100-120 ℃/min.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

In order to better illustrate the embodiments of the present invention, the following examples are further illustrative.