阅读说明：本技术 一种基于机械化学强化的铬渣湿法解毒方法 (Chromium slag wet detoxification method based on mechanochemical strengthening ) 是由 陈窈君 吕正勇 李来顺 闵玉涛 苗竹 朱湖地 倪鑫鑫 任贝 安振杰 崔新刚 于 2020-04-08 设计创作，主要内容包括：本发明公开了一种基于机械化学强化的铬渣湿法解毒方法,包括：将铬渣与硫铁矿加入球磨机中进行湿磨,铬渣与硫铁矿在球磨的作用下进行一次机械化学还原处理；向一次还原反应后的铬渣料浆中加入酸化剂,溶出酸溶性六价铬；向酸化后的铬渣料浆中加入还原剂,进行二次还原处理。本发明根据硫铁矿在碱性条件下可以降低浆液pH值、有效还原Cr(VI)等特点,设计了在铬渣球磨阶段同时加入硫铁矿进行还原的工艺,一方面可以降低浆液pH值,减少后续铬渣浆液酸溶时酸化剂的添加量；另一方面可以充分利用球磨的机械化学作用,将六价铬还原反应的时间提前,并且减少在还原解毒阶段还原剂的添加量,能够极大地降低运行时间和运行成本。(The invention discloses a wet detoxification method of chromium slag based on mechanochemical strengthening, which comprises the following steps: adding the chromium slag and the pyrite into a ball mill for wet milling, and carrying out primary mechanochemical reduction treatment on the chromium slag and the pyrite under the action of the ball mill; adding an acidifier into the chromium slag slurry after the primary reduction reaction to dissolve out the acid-soluble hexavalent chromium; and adding a reducing agent into the acidified chromium slag slurry for secondary reduction treatment. According to the characteristics that the pH value of the slurry can be reduced and Cr (VI) can be effectively reduced in the pyrite under the alkaline condition, and the like, the process that the pyrite is added at the same time in the chromium slag ball-milling stage for reduction is designed, so that on one hand, the pH value of the slurry can be reduced, and the addition amount of an acidifier in the subsequent acid dissolution of the chromium slag slurry is reduced; on the other hand, the mechanical and chemical action of ball milling can be fully utilized, the time of hexavalent chromium reduction reaction is advanced, the addition amount of a reducing agent in the reduction detoxification stage is reduced, and the running time and the running cost can be greatly reduced.)

1. A chromium slag wet detoxification method based on mechanochemical strengthening is characterized by comprising the following steps:

adding the chromium slag and the pyrite into a ball mill for wet milling, and carrying out primary mechanochemical reduction treatment on the chromium slag and the pyrite under the action of ball milling;

adding an acidifier into the chromium slag slurry after the primary reduction reaction to dissolve out the acid-soluble hexavalent chromium;

and adding a reducing agent into the acidified chromium slag slurry for secondary reduction treatment.

2. A chromium slag wet detoxification method according to claim 1, wherein in the primary mechanochemical reduction treatment:

the mass ratio of the pyrite, the chromium slag and the water is (0.07-0.15) to 1:1, and the time of ball milling and one-time mechanochemical reduction treatment is 1-1.5 h.

3. The wet detoxification method of chromium slag as claimed in claim 1, wherein the slurry of chromium slag after the primary reduction reaction is subjected to cyclone separation before acidulant is added;

the cyclonic separation comprises: and (3) carrying out cyclone separation on the chromium slag slurry after the primary reduction reaction in a cyclone separation device, carrying out subsequent acidification and soaking on the chromium slag slurry with the granularity smaller than 200 meshes in a stirring tank, and returning the chromium slag with the granularity larger than 200 meshes to the ball mill for wet grinding again.

4. The wet detoxification method of chromium slag as claimed in claim 3, wherein the acidifying agent is added to the slurry of chromium slag in the agitation tank while agitating, and the slurry is acidified and soaked until the pH of the slurry is stabilized below 5.5, to dissolve out the acid-soluble hexavalent chromium.

5. A chromium slag wet detoxification method as claimed in claim 4, wherein said acidifying agent comprises one of sulfuric acid, hydrochloric acid, nitric acid and phosphoric acid, and the mass ratio of said acidifying agent to chromium slag is (0.4-0.6): 1.

6. The wet detoxification method of chromium slag as claimed in claim 1, wherein the mass ratio of the reducing agent to the chromium slag is (0.2-0.3): 1.

7. A chromium slag wet detoxification method as claimed in claim 1, wherein the reaction time of the secondary reduction treatment is between 1 and 2 hours, and the secondary reduction reaction is followed by aging for 5 to 6 hours.

8. A chromium slag wet detoxification method as claimed in claim 1, wherein said reducing agent comprises one of ferrous sulfate and sodium metabisulfite.

9. The chromium slag wet detoxification method as claimed in claim 8, wherein the chemical reaction formula of the chromium slag wet detoxification method is as follows:

reducing water-soluble hexavalent chromium under alkaline conditions:

3Fe²⁺+Cr₂O₇ ^2-+8H₂O→Cr(OH)₃↓+Fe(OH)₃↓+4H⁺；

dissolving out acid-soluble hexavalent chromium:

2CaCrO₄+4H⁺→2Ca²⁺+H₂Cr₂O₇+H₂O；

reducing acid-soluble hexavalent chromium:

when the reducing agent is ferrous sulfate, CrO₄ ^2-+3Fe²⁺+8H⁺→3Fe³⁺+Cr(III)+4H₂O；

Or the like, or, alternatively,

when the reducing agent is sodium metabisulfite, 4CrO₄ ^2-+3S₂O₅ ^2-+14H⁺→4Cr(III)+6SO₄ ^2-+7H₂O。

10. The chromium slag wet detoxification method as claimed in claim 1, wherein the chromium-containing slurry after the secondary reduction reaction is pumped to a filter press for solid-liquid separation, and the filtrate enters a circulating water tank and returns to the wet ball milling process of the chromium slag for recycling.

Technical Field

The invention relates to the technical field of harmless treatment of chromium slag, in particular to a wet detoxification method of chromium slag based on mechanochemical strengthening.

Background

The chromium slag is solid waste generated in the production process of chromium salt and metal chromium, and Cr (VI) in the chromium slag enters a water environment when being soaked in water to cause serious pollution and influence on human health. Cr (VI) contained in the chromium slag has 100 times of toxicity higher than that of Cr (III), stimulates respiratory tracts and digestive tracts, and can cause acute respiratory tract stimulation, allergic asthma and respiratory tract injury by inhaling dust or smoke containing Cr (VI) compounds, and is also manifested by nasal septum ulcer, perforation and respiratory system cancer. Meanwhile, Cr (VI) is corrosive and can cause damage to human skin to form chromium skin ulcer. Cr (VI) also has systemic toxic effects, and can cause blood dysfunction and bone failure. The main harmful substances in the chromium slag are calcium chromate (carcinogen) and water-soluble hexavalent chromium (virulent), and the chromium slag is a strong alkaline substance, so that the chromium slag which is piled for a long time is washed by rainwater, and then causes pollution to surface water and underground water, and the production and the life of local residents are seriously influenced. The chromium slag is directly stacked on the soil, and the pollution of the high-content chromium on the soil cannot be ignored. The chromium pollution degree of the soil of the chromium slag piling yard is serious, which causes the soil pollution of larger areas at the periphery and the underground deep part, and some depths even reach the underground bedrock.

At present, the chromium slag is treated by the following two ways, namely comprehensive utilization and detoxification discharge. The chromium residue detoxification mainly comprises dry detoxification, biological detoxification, solidification detoxification, wet detoxification and the like.

The chromium residue dry detoxification refers to a method for reducing Cr (VI) in the chromium residue into Cr (III) and fixing the Cr (VI) by using reducing substances under a high-temperature condition; the dry detoxification method mainly comprises dry detoxification of a rotary kiln, treatment of chromium slag in a cyclone furnace, sintering of the chromium slag for iron making, brick making and the like. The dry detoxification of chromium slag has the problem of large amount of flue gas generated by an incineration system, and smoke and dust removal equipment is required to be added for preventing secondary pollution, so that the capacity of tail gas treatment equipment is required to be relatively large, and the running cost of the system is relatively high.

The biological detoxication treatment technology of chromium slag is to reduce Cr (VI) into Cr (III) by utilizing the efficient reduction of chromate reducing bacteria, but because the chromium slag has complex components, lacks of nutrient substrates for bacterial growth and is alkaline, the growth and the propagation of microorganisms are difficult in the extreme environment.

The detoxification treatment by the chromium slag solidification method means that the chromium slag is fixed or sealed in a final product taking a solid as a matrix by cement at normal temperature by adopting a physical or chemical method, the product has high permeability resistance, and cement is mostly adopted as a curing agent. The cement solidification method needs to add a considerable amount of cement, has high power consumption and high cost, and is not suitable for the national conditions of China.

The wet detoxification of chromium slag refers to a method of reducing Cr (VI) in chromium slag into Cr (III) by using a reducing substance in a liquid medium and fixing the Cr (VI) or fixing the Cr (III) by using a precipitator. The wet detoxification treatment technology of the chromium slag is simple, the equipment is easy to select, and detoxification is thorough; however, the solid-liquid separation and dissolution time is long, and the dosage of the medicament is large, so the treatment cost is high.

Disclosure of Invention

Aiming at the defects of the chromium slag detoxification process, the invention provides a chromium slag wet detoxification method based on mechanochemical strengthening.

The invention discloses a wet detoxification method of chromium slag based on mechanochemical strengthening, which comprises the following steps:

adding the chromium slag and the pyrite into a ball mill for wet milling, and carrying out primary mechanochemical reduction treatment on the chromium slag and the pyrite under the action of ball milling;

adding an acidifier into the chromium slag slurry after the primary reduction reaction to dissolve out the acid-soluble hexavalent chromium;

and adding a reducing agent into the acidified chromium slag slurry for secondary reduction treatment.

As a further improvement of the present invention, in the primary mechanochemical reduction treatment:

the mass ratio of the pyrite, the chromium slag and the water is (0.07-0.15) to 1:1, and the time of ball milling and one-time mechanochemical reduction treatment is 1-1.5 h.

As a further improvement of the method, the chromium slag slurry after the primary reduction reaction needs to be subjected to cyclone separation before the acidulant is added;

the cyclonic separation comprises: and (3) carrying out cyclone separation on the chromium slag slurry after the primary reduction reaction in a cyclone separation device, carrying out subsequent acidification and soaking on the chromium slag slurry with the granularity smaller than 200 meshes in a stirring tank, and returning the chromium slag with the granularity larger than 200 meshes to the ball mill for wet grinding again.

As a further improvement of the invention, the chrome slag slurry in the stirring tank is stirred and added with the acidifier, and the mixture is acidified and soaked until the pH value of the slurry is stabilized below 5.5, so that the acid-soluble hexavalent chromium is dissolved out.

As a further improvement of the invention, the acidifying agent comprises one of sulfuric acid, hydrochloric acid, nitric acid and phosphoric acid, and the mass ratio of the acidifying agent to the chromium slag is (0.4-0.6): 1.

As a further improvement of the invention, the mass ratio of the reducing agent to the chromium slag is (0.2-0.3): 1.

As a further improvement of the invention, the reaction time of the secondary reduction treatment is 1-2h, and the secondary reduction reaction is followed by aging for 5-6 h.

As a further improvement of the invention, the reducing agent comprises one of ferrous sulfate and sodium metabisulfite.

As a further improvement of the invention, the chemical reaction formula of the wet detoxification method of the chromium slag is as follows:

reducing water-soluble hexavalent chromium under alkaline conditions:

3Fe²⁺+Cr₂O₇ ^2-+8H₂O→Cr(OH)₃↓+Fe(OH)₃↓+4H⁺；

dissolving out acid-soluble hexavalent chromium:

2CaCrO₄+4H⁺→2Ca²⁺+H₂Cr₂O₇+H₂O；

reducing acid-soluble hexavalent chromium:

when the reducing agent is ferrous sulfate, CrO₄ ^2-+3Fe²⁺+8H⁺→3Fe³⁺+Cr(III)+4H₂O；

Or the like, or, alternatively,

when the reducing agent is sodium metabisulfite, 4CrO₄ ^2-+3S₂O₅ ^2-+14H⁺→4Cr(III)+6SO₄ ^2-+7H₂O。

As a further improvement of the method, the chromium-containing slurry after the secondary reduction reaction is pumped to a filter press for solid-liquid separation, and the filtrate enters a circulating water tank and returns to the wet ball-milling process of the chromium slag for recycling.

Compared with the prior art, the invention has the beneficial effects that:

the method adopts two-time reduction detoxification on the chromium slag, wherein the first reduction is that a reducing agent pyrite is added in the wet ball milling stage of the chromium slag, the chromium slag and the pyrite are subjected to mechanochemical reduction reaction under the action of ball milling, water-soluble hexavalent chromium dissolved out during crushing can be reduced, and the addition amount of the reducing agent and the reduction time during the second reduction are reduced; in addition, in the alkaline medium reaction of pyrite, because of Fe²⁺And Fe³⁺With OH^-Consuming OH by the binding of^-Therefore, the pH value of the slurry can be reduced by adding the pyrite, the dissolution and the acid production of the pyrite are promoted by utilizing the mechanical action, the pH value in a reaction system is reduced, and the subsequent acid dissolution of the chromium slag slurry is reducedThe amount of the acidifying agent added is not particularly limited. The second reduction is that the acid-soluble hexavalent chromium of the chromium slag slurry is fully dissolved out in an acid environment, and then reducing agents such as ferrous sulfate, sodium pyrosulfite and the like are added to reduce the acid-soluble hexavalent chromium of the chromium slag into trivalent chromium, and the hexavalent chromium in the chromium slag can be fully detoxified by a two-step reduction method.

According to the invention, pyrite is added in the wet ball milling stage to reduce the water-soluble hexavalent chromium, the mechanochemical action of the ball milling is fully utilized, the reduction reaction is promoted, the reduction reaction time and the addition of a reducing agent are reduced, the pH value of the system is reduced, and the addition of an acidifying agent is reduced.

Drawings

FIG. 1 is a flow chart of a wet detoxification method of chromium slag based on mechanochemical strengthening according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

The invention is described in further detail below with reference to the attached drawing figures:

the invention relates to a chromium slag wet detoxification method based on mechanochemical strengthening, which has the design principle that:

the process is characterized in that pyrite is used for carrying out primary reduction detoxification on Cr (VI) in the chromium slag on the basis of the traditional wet detoxification, and according to the characteristics of the pyrite under the alkaline condition, such as capability of reducing the pH value of slurry and effective reduction of Cr (VI), the process for reducing by adding pyrite in the chromium slag ball-milling stage is designed, so that on one hand, the pH value of the slurry can be reduced, the addition amount of an acidifier in the subsequent acid dissolution of the chromium slag slurry is reduced, on the other hand, the mechanochemical action of ball milling can be fully utilized, the time of hexavalent chromium reduction reaction is advanced, the addition amount of a reducing agent in the reduction detoxification stage is reduced, and the running time and the running cost can be.

Based on the design principle, the invention provides a chromium slag wet detoxification method based on mechanochemical strengthening, which comprises the following steps: adding the chromium slag and the pyrite into a ball mill for wet milling, and carrying out primary mechanochemical reduction treatment on the chromium slag and the pyrite under the action of the ball mill; adding an acidifier into the chromium slag slurry after the primary reduction reaction to dissolve out the acid-soluble hexavalent chromium; and adding a reducing agent into the acidified chromium slag slurry for secondary reduction treatment.

Specifically, the method comprises the following steps:

as shown in FIG. 1, the invention provides a wet detoxification method of chromium slag based on mechanochemical strengthening, which comprises the following steps:

step 1, adding chromium slag, pyrite and water into a ball mill for wet milling, and carrying out primary mechanochemical reduction treatment on the chromium slag and the pyrite under the action of the ball mill; wherein the content of the first and second substances,

the chromium slag and the pyrite can be added simultaneously, or the chromium slag can be added firstly, and then the pyrite can be added; before adding, the grain diameter of the chromium slag is larger than 200 meshes, and the grain diameter of the pyrite is 300 meshes. The invention adopts a ball mill to carry out wet grinding, and aims to: when the chromium slag is ball-milled and crushed, water-soluble hexavalent chromium is dissolved out, and the hexavalent chromium reduces the water-soluble hexavalent chromium in the slurry, namely the chromium slag and the pyrite are subjected to mechanochemical reduction reaction under the action of ball milling; meanwhile, the dissolution and the acid production of the pyrite are promoted by utilizing the mechanical action, the pH value in a reaction system is reduced, and the addition amount of an acidifier is reduced.

Furthermore, the mass ratio of the pyrite, the chromium slag and the water is (0.07-0.15) to 1:1, the time of ball milling and one-time mechanochemical reduction treatment is 1-1.5h, and the preferable treatment time is 1 h.

Step 2, enabling the chromium slag slurry after the primary reduction reaction to enter a cyclone separation device for cyclone separation, enabling the chromium slag slurry with the granularity smaller than 200 meshes to enter a stirring tank for subsequent acidification and soaking, and returning the chromium slag with the granularity larger than 200 meshes to a ball mill for wet grinding again; wherein the content of the first and second substances,

step 2 is a step of selecting addition or deletion according to actual requirements, and the particle sizes can be determined to reach the preset particle sizes by prolonging the ball milling time; meanwhile, the particle sizes with different meshes can be selected for separating the chromium slag during the cyclone separation.

Step 3, adding an acidifying agent into the chromium slag slurry while stirring, acidifying and soaking until the pH value is stabilized below 5.5, and dissolving out acid-soluble hexavalent chromium; wherein the content of the first and second substances,

the acidifying agent comprises one of sulfuric acid, hydrochloric acid, nitric acid and phosphoric acid, and the mass ratio of the acidifying agent to the chromium slag is (0.4-0.6): 1.

Step 4, adding a reducing agent into the acidified chromium slag slurry for secondary reduction treatment; wherein the content of the first and second substances,

and adding a reducing agent into the acidified and soaked chromium slag slurry, uniformly mixing, and carrying out secondary reduction treatment to reduce the dissolved hexavalent chromium into trivalent chromium so as to achieve the aim of detoxifying the chromium slag.

The reducing agent comprises one of ferrous sulfate and sodium metabisulfite. The mass ratio of the reducing agent to the chromium slag is (0.2-0.3): 1.

The reaction time of the secondary reduction treatment is 1-2h, preferably 2 h; so as to reduce the acid-soluble hexavalent chromium in the chromium-containing slurry to form trivalent chromium

After the secondary reduction reaction, curing for 5-6h, preferably 6 h; the time of acidification soaking and reduction detoxification is increased, and the detoxification effect is stabilized.

Step 5, pumping the chromium-containing slurry subjected to the second reduction to a filter press for solid-liquid separation, and feeding the filtrate into a circulating water tank to return to the wet ball milling process of the chromium slag for recycling; and (5) conveying the filter-pressed mud cakes to a region to be detected.

In order to intuitively reflect the process of the wet detoxification method of the chromium slag, the chemical reaction formula of each step of the method is as follows:

reducing the water-soluble hexavalent chromium under the alkaline condition related to the step 1:

3Fe²⁺+Cr₂O₇ ^2-+8H₂O→Cr(OH)₃↓+Fe(OH)₃↓+4H⁺；

dissolving out acid-soluble hexavalent chromium related to the step 3:

2CaCrO₄+4H⁺→2Ca²⁺+H₂Cr₂O₇+H₂O；

reducing the acid-soluble hexavalent chromium related to the step 4:

when the reducing agent is ferrous sulfate, CrO₄ ^2-+3Fe²⁺+8H⁺→3Fe³⁺+Cr(III)+4H₂O；

Or the like, or, alternatively,

when the reducing agent is sodium metabisulfite, 4CrO₄ ^2-+3S₂O₅ ^2-+14H⁺→4Cr(III)+6SO₄ ^2-+7H₂O。