CN105903562A - Method for extracting iron ore concentrate from flyash - Google Patents

Abstract

The invention relates to a method for extracting iron concentrate from fly ash. The technical scheme is: dry-type magnetic separation of fly ash in a screw dry-type magnetic separator with a magnetic field strength of 0.3-0.5T to obtain rough concentrate and dry tailings. Add water to the coarse concentrate and place it in a wet magnetic separator with a magnetic field strength of 0.16-0.2T, and wet magnetic separation to obtain wet magnetic separation concentrate. Put the wet magnetic separation concentrate, or the mixture of the wet magnetic separation concentrate and the second-stage tailings obtained in the subsequent process, into a ball mill, and after adding water, ball mill until the particle size is less than 0.045mm, accounting for 70~90wt%, to obtain a finely ground pulp. Put the finely ground pulp into a wet magnetic separator with a magnetic field strength of 0.06-0.1T to obtain a first-stage concentrate. The first-stage concentrate is added to a wet magnetic separator with a magnetic field strength of 0.04~0.08T for second-stage weak magnetic separation to obtain iron concentrate and second-stage tailings. Second stage tailings return to step three. The invention has the characteristics of simple process, energy saving, high grade iron concentrate and high iron recovery rate.

Description

A method for extracting iron concentrate from fly ash

technical field

The invention belongs to the technical field of fly ash utilization. Specifically relates to a method for extracting iron concentrate from fly ash.

Background technique

Fly ash is a dust-like substance collected from the flue gas of pulverized coal boilers, and it is a bulk solid waste discharged from modern coal-fired power plants. As a country that uses coal as its main energy source, China relies on coal-fired power generation for a considerable part of its power supply. At present, the total amount of fly ash produced by coal combustion has exceeded 1 billion tons, and it is increasing at a rate of 80 to 100 million tons per year. my country has become the largest ash discharge country in the world. Poor handling of fly ash will not only pollute the air, soil and water, but also occupy a large amount of land, causing great negative pressure on the social economy and the ecological environment. Therefore, how to turn waste into treasure and make efficient utilization of fly ash resources is a problem that cannot be ignored.

The utilization of domestic fly ash is usually mainly to produce basic building materials such as cement and concrete, or it is directly used for backfilling. The technical level and economic added value of these methods are relatively low. Moreover, iron, aluminum and some valuable metals in fly ash have not been effectively recovered.

Recovering iron from fly ash can enrich the iron minerals dispersed in fly ash and use it in iron and steel metallurgy to improve the utilization rate of resources. On the other hand, it can greatly reduce the iron content in fly ash and broaden the utilization range of fly ash. For example, for the zeolite industry and rubber product industry that use fly ash as raw material, the iron in fly ash is a harmful impurity. remove. Therefore, extracting iron concentrate powder from fly ash is a more economical and reasonable utilization method.

The recovery and treatment of iron in fly ash mainly includes the following aspects:

The first is fly ash iron removal, that is, the iron minerals in fly ash are used as the object of iron removal, usually through acid-dissolving treatment, the iron in fly ash enters the solution in the form of Fe ions, and then is discharged with the waste liquid. The iron in fly ash is simply removed but not effectively utilized.

Iron removal from high-alumina fly ash (Cao Jian et al. Experimental research on iron removal from high-alumina fly ash. Bulletin of Mineral, Rock and Geochemistry, 2010.3), the fly ash was calcined at 900°C for 2 hours for decarburization, and then the concentration of hydrochloric acid was Under the conditions of 20%, liquid-solid ratio of 5:1, temperature of 80°C and stirring time of 60 minutes, although the iron removal rate reached over 80%, iron minerals were not recovered and a large amount of acid was consumed.

"A Method for Efficiently Removing Iron from Fly Ash" (CN201510174024.3) patented technology, this technology sequentially undergoes reduction, magnetic separation, and hydrochloric acid leaching of fine powder of fly ash, although the powdered coal with Fe content less than 0.02% is obtained Ash, but not related to iron recycling.

Second, the iron in fly ash is recovered as a by-product. The iron ore powder in fly ash is not used as the main product. It is generally recovered through a magnetic separation. The recovered iron ore is not of high grade and it is difficult to meet the smelting requirements.

"Extraction of carbon powder, iron ore powder, primary fly ash and secondary fly ash preparation process from fly ash" (CN201210183445.9) patented technology, this technology puts the fly ash raw material through the first micro-bubble flotation And the second micro-bubble flotation and magnetic separation can be separated and recovered to obtain carbon powder, iron ore powder, first-grade fly ash and second-grade fly ash, and the fly ash only needs one stage of magnetic separation to obtain iron ore powder, iron ore powder The quality of mineral powder is not high.

The third is to recover iron ore powder through wet magnetic separation, although wet magnetic separation process can obtain higher iron grade. However, the wet magnetic separation process consumes a lot of water resources, and about 90wt% of the fly ash will be discharged as wet tailings, which not only occupies land and pollutes the environment, but also reduces the activity of building materials in the tailings, affecting subsequent utilization.

Fly ash undergoes two-stage magnetic separation (Zhou Qiuling et al. Application and Exploration of Fly Ash Iron Separation Process. Water Conservancy, Electric Power and Labor Protection, 1998), and iron concentrate with iron grade greater than 50% can be obtained, but the concentrate iron grade is not high , SiO ₂ content is still high.

Fly ash raw materials are subjected to magnetic separation of one coarse, one fine, and one sweep (Tang Yun et al. Experimental Research on Iron Separation of Power Plant Fly Ash. Mining Research and Development, 2008), although the iron grade can be obtained at 50.95% and the recovery rate is 46.41% iron ore concentrate, but there are problems such as high water consumption, high energy consumption and land occupation.

The fourth is to recover iron ore powder through dry magnetic separation, which is to separate directly from the dry ash conveying pipeline or the ash storage tank without adding water during the iron separation process. Although this method has simple process, less equipment and low energy consumption, gangue minerals are easily mixed in iron concentrate, resulting in low iron grade of the product, and the current fly ash magnetic separation equipment is not mature enough, which affects the dryness of fly ash. The effect of type magnetic separation.

Huaneng Yimin Power Plant in Hulunbeier City, Inner Mongolia conducted a test of dry recovery of iron powder from fly ash (Geng Lansheng. Feasibility of dry recovery of fly ash and iron powder in coal-fired power plants. Fly Ash, 2009), although iron powder can be obtained Iron concentrate with a grade greater than 50%. However, it still contains high gangue minerals, and it is difficult to meet the smelting requirements.

Contents of the invention

The invention aims to overcome the defects of the prior art, and aims to provide a method for extracting iron concentrate from fly ash with simple process, energy saving, high iron grade of iron concentrate powder and high iron recovery rate.

In order to achieve the above object, the concrete steps of the technical solution adopted in the present invention are:

Step 1. Evenly add fly ash to the screw dry magnetic separator for dry magnetic separation. The magnetic field strength of the dry magnetic separation is 0.3-0.5T to obtain rough concentrate and dry tailings.

Step 2, adding water to the rough concentrate to a concentration of 15 to 20wt% to obtain a rough concentrate slurry, adding the rough concentrate slurry to the first wet magnetic separator for wet magnetic separation, the magnetic field strength of the wet magnetic separation 0.16 ~ 0.2T, to obtain wet magnetic separation concentrate and wet magnetic separation tailings.

Step 3. Put the wet magnetic separation concentrate, or the mixture of the wet magnetic separation concentrate and the second-stage tailings obtained in the subsequent process, into a ball mill, add water to a concentration of 40 to 50 wt%, and ball mill until the particle size is less than 0.045mm accounts for 70~90wt% to obtain finely ground pulp.

Step 4: Put the finely ground pulp into the second wet magnetic separator for a stage of weak magnetic separation, the magnetic field strength of the stage of weak magnetic concentration is 0.06-0.1T, to obtain a stage of concentrate and a stage of tailings.

Step 5: Add the first-stage concentrate to the third wet magnetic separator, and perform the second-stage weak magnetic separation, the magnetic field strength of the second-stage weak magnetic separation is 0.04-0.08T, and obtain the iron concentrate and the second-stage tailings. Second stage tailings return to step three.

The fly ash: TFe is 5-15%, magnetite accounts for 45-70wt% of the total iron content, _SiO2 content is 40-60wt%; the content of the fly ash particle size less than 0.074mm is 50-75wt% %.

Owing to adopting above-mentioned method, the present invention has following positive effect compared with prior art:

1. Due to the dry magnetic separation of fly ash, the present invention can remove 70-80% of the dry tailings at one time. In addition to high efficiency, the dry tailings can also be directly used as building materials, avoiding the need for pulverized coal The activity and uniformity of the ash will decrease after it gets wet; in addition, the wet magnetic separation of the fly ash can effectively remove the gangue minerals entrained by the coarse concentrate in the dry magnetic separation.

2. In the present invention, due to the ball milling of the fly ash, the iron-containing fly ash particles achieve a higher dissociation degree, and the iron-containing minerals and gangue minerals are effectively separated. Iron concentrate grade.

3. In the present invention, due to the high iron content, large magnetic iron content and coarse particles of the tailings in the second stage, in order to effectively separate the iron minerals and gangue minerals, they are returned to the third step for ball milling, which significantly improves the iron recovery rate.

4. The present invention not only overcomes the problems of large water consumption, wet discharge tailings occupying a lot of land and polluting the environment for single wet magnetic separation, but also solves the problem that the grade of iron concentrate powder iron of single dry magnetic separation is not high. The complementary advantages of dry magnetic separation and wet magnetic separation are realized, and the best process effect is obtained.

5. The iron recovery rate of the iron concentrate extracted by the present invention is 53-55%, and the TFe is 54-56%; the iron grade of the dry tailings after dry magnetic separation is reduced to below 3%.

Therefore, the invention has the characteristics of simple process, energy saving, high iron grade of fine iron concentrate and high iron recovery rate.

detailed description

Example 1

A method for extracting iron concentrate from fly ash. The specific steps of the implementation mode of this embodiment are:

Step 1. Evenly add fly ash to the screw dry magnetic separator for dry magnetic separation. The magnetic field strength of the dry magnetic separation is 0.3-0.35T to obtain rough concentrate and dry tailings.

Step 2, adding water to the rough concentrate to a concentration of 15 to 20wt% to obtain a rough concentrate slurry, adding the rough concentrate slurry to the first wet magnetic separator for wet magnetic separation, the magnetic field strength of the wet magnetic separation It is 0.16-0.17T, and wet magnetic separation concentrate and wet magnetic separation tailings are obtained.

Step 3. Put the wet magnetic separation concentrate, or the mixture of the wet magnetic separation concentrate and the second-stage tailings obtained in the subsequent process, into a ball mill, add water to a concentration of 40 to 50 wt%, and ball mill until the particle size is less than 0.045mm accounts for 70~80wt% to obtain finely ground pulp.

Step 4: Add the finely ground pulp into the second wet magnetic separator, and perform a stage of weak magnetic concentration, the magnetic field strength of the stage of weak magnetic concentration is 0.06-0.07T, and obtain a stage of concentrate and a stage of tailings.

Step 5: Add the first-stage concentrate to the third wet magnetic separator, and perform the second-stage weak magnetic separation, the magnetic field strength of the second-stage weak magnetic separation is 0.04-0.05T, and obtain the iron concentrate and the second-stage tailings. Second stage tailings return to step three.

The fly ash described in the present embodiment is the dry discharge fly ash of a certain coal-fired power plant in Northwest China: TFe is 8-15%, magnetite accounts for 55-70wt% of the total iron content, and SiO content is _40-50wt %; The content of the fly ash with particle size less than 0.074mm is 50-65wt%.

The iron recovery rate of the iron concentrate extracted in this embodiment is 53-53.5%, and the TFe is 55.5-56%. The iron grade of the dry tailings after dry magnetic separation is reduced to 2.2-2.4%.

Example 2

A method for extracting iron concentrate from fly ash. The concrete steps of the method described in this embodiment are:

Step 1. Evenly add fly ash to the screw dry magnetic separator for dry magnetic separation. The magnetic field strength of the dry magnetic separation is 0.35-0.4T to obtain rough concentrate and dry tailings.

Step 2, adding water to the rough concentrate to a concentration of 15 to 20wt% to obtain a rough concentrate slurry, adding the rough concentrate slurry to the first wet magnetic separator for wet magnetic separation, the magnetic field strength of the wet magnetic separation It is 0.17～0.18T, and wet magnetic separation concentrate and wet magnetic separation tailings are obtained.

Step 3. Put the wet magnetic separation concentrate, or the mixture of the wet magnetic separation concentrate and the second-stage tailings obtained in the subsequent process, into a ball mill, add water to a concentration of 40 to 50 wt%, and ball mill until the particle size is less than 0.045mm accounts for 70~80wt% to obtain finely ground pulp.

Step 4: Add the finely ground pulp into the second wet magnetic separator for a stage of weak magnetic separation, the magnetic field strength of the stage of weak magnetic concentration is 0.07-0.08T, to obtain a stage of concentrate and a stage of tailings.

Step 5: Add the first-stage concentrate to the third wet magnetic separator, and perform the second-stage weak magnetic separation, the magnetic field strength of the second-stage weak magnetic separation is 0.05-0.06T, and obtain the iron concentrate and the second-stage tailings. Second stage tailings return to step three.

The fly ash described in this embodiment is the same as in Embodiment 1.

The iron recovery rate of the iron concentrate extracted in this embodiment is 53.4-53.8%, and the TFe is 55.2-55.6%. The iron grade of the dry tailings after dry magnetic separation is reduced to 2.3-2.6%.

Example 3

A method for extracting iron concentrate from fly ash. The concrete steps of the method described in this embodiment are:

Step 1. Evenly add fly ash to the screw dry magnetic separator for dry magnetic separation. The magnetic field strength of the dry magnetic separation is 0.4-0.45T to obtain rough concentrate and dry tailings.

Step 2, adding water to the rough concentrate to a concentration of 15 to 20wt% to obtain a rough concentrate slurry, adding the rough concentrate slurry to the first wet magnetic separator for wet magnetic separation, the magnetic field strength of the wet magnetic separation It is 0.18～0.19T, and wet magnetic separation concentrate and wet magnetic separation tailings are obtained.

Step 3. Put the wet magnetic separation concentrate, or the mixture of the wet magnetic separation concentrate and the second-stage tailings obtained in the subsequent process, into a ball mill, add water to a concentration of 40 to 50 wt%, and ball mill until the particle size is less than 0.045mm accounts for 80~90wt% to obtain finely ground pulp.

Step 4: Put the finely ground pulp into the second wet magnetic separator, and perform a stage of weak magnetic concentration, the magnetic field strength of the stage of weak magnetic concentration is 0.08-0.09T, and obtain a stage of concentrate and a stage of tailings.

Step 5: Add the first-stage concentrate to the third wet magnetic separator, and perform the second-stage weak magnetic separation. The magnetic field strength of the second-stage weak magnetic separation is 0.06-0.07T to obtain the iron concentrate and the second-stage tailings. Second stage tailings return to step three.

The fly ash described in the present embodiment is the dry discharge fly ash of a certain coal-fired power plant in North China: TFe is ₅ ~ 12%, magnetite accounts for 45 ~ 60wt% of the total iron content, and SiO content is 50 ~ 60wt%; The content of the fly ash with particle size less than 0.074mm is 60-75wt%.

The iron recovery rate of the iron concentrate extracted in this embodiment is 53.4-53.6%, and the TFe is 54.3-55%. The iron grade of the dry tailings after dry magnetic separation is reduced to 2.7-3%.

Example 4

A method for extracting iron concentrate from fly ash. The concrete steps of the method described in this embodiment are:

Step 1. Evenly add fly ash to the screw dry magnetic separator for dry magnetic separation. The magnetic field strength of the dry magnetic separation is 0.45-0.5T to obtain rough concentrate and dry tailings.

Step 2, adding water to the rough concentrate to a concentration of 15 to 20wt% to obtain a rough concentrate slurry, adding the rough concentrate slurry to the first wet magnetic separator for wet magnetic separation, the magnetic field strength of the wet magnetic separation 0.19 ~ 0.2T, to obtain wet magnetic separation concentrate and wet magnetic separation tailings.

Step 3. Put the wet magnetic separation concentrate, or the mixture of the wet magnetic separation concentrate and the second-stage tailings obtained in the subsequent process, into a ball mill, add water to a concentration of 40 to 50 wt%, and ball mill until the particle size is less than 0.045mm accounts for 80~90wt% to obtain finely ground pulp.

Step 4: Put the finely ground pulp into the second wet magnetic separator, and perform a stage of weak magnetic concentration, the magnetic field strength of the stage of weak magnetic concentration is 0.09-0.1T, and obtain a stage of concentrate and a stage of tailings.

Step 5: Add the first-stage concentrate to the third wet magnetic separator, and perform the second-stage weak magnetic separation, the magnetic field strength of the second-stage weak magnetic separation is 0.07-0.08T, and obtain the iron concentrate and the second-stage tailings. Second stage tailings return to step three.

The fly ash described in this embodiment is the same as in Embodiment 3.

The iron recovery rate of the iron concentrate extracted in this embodiment is 54.1-55%, and the TFe is 54-54.6%. The iron grade of the dry tailings after dry magnetic separation is reduced to 2.5-2.8%.

Compared with the prior art, this specific embodiment has the following positive effects:

1. Due to the dry magnetic separation of fly ash in this specific embodiment, 70-80% of the dry tailings can be thrown away at one time. In addition to high efficiency, the dry tailings can also be directly used for building materials, avoiding the The activity and uniformity of the fly ash will decrease due to getting wet; in addition, the wet magnetic separation of the fly ash can effectively remove the gangue minerals entrained by the coarse concentrate in the dry magnetic separation.

2. In this specific embodiment, due to the ball milling of the fly ash, the iron-containing fly ash particles achieve a higher degree of dissociation, and the iron-containing minerals and gangue minerals are effectively separated, and then through two stages of weak magnetic concentration, Increased iron concentrate grade.

3. In this specific embodiment, due to the high iron content of the tailings in the second stage, large magnetic iron content and coarse particles, in order to effectively separate iron minerals and gangue minerals, they are returned to step three for ball milling, which significantly improves the iron recovery rate .

4. This specific embodiment not only overcomes the problems of large water consumption, wet discharge tailings occupying a large area and polluting the environment for single wet magnetic separation, but also solves the problem of low-grade iron concentrate powder iron for single dry magnetic separation. The complementary advantages of dry magnetic separation and wet magnetic separation are realized, and the best process effect is obtained.

5. The iron recovery rate of the iron concentrate extracted in this specific embodiment is 53-55%, and the TFe is 54-56%; the iron grade of the dry tailings after dry magnetic separation is reduced to below 3%.

Therefore, this specific embodiment has the characteristics of simple process, energy saving, high grade iron concentrate and high iron recovery rate.

Claims (2)

1. the method extracting iron ore concentrate from flyash, it is characterised in that comprising the concrete steps that of described method:

Step one, being homogeneously added into by flyash in screw dry magnetic separator, carry out dry type magnetic separation, the field strength of dry type magnetic separation is 0.3～0.5T, obtains rough concentrate and dry type mine tailing；

Step 2, described rough concentrate adds water to concentration is 15 ~ 20wt%, obtain coarse-fine ore pulp, being added by described coarse-fine ore pulp and carry out wet magnetic separation in the first wet magnetic separator, the magnetic field intensity of wet magnetic separation is 0.16～0.2T, obtains wet magnetic separation concentrate and wet magnetic separation mine tailing；

Step 3, the compound of the two-stage nitration mine tailing described wet magnetic separation concentrate or described wet magnetic separation concentrate obtained with subsequent technique are placed in ball mill, and adding water to concentration is 40 ~ 50wt%, are milled to granularity and account for 70 ~ 90wt% less than 0.045mm, obtain fine grinding ore pulp；

Step 4, adding in the second wet magnetic separator by described fine grinding ore pulp, it is selected to carry out one section of weak magnetic, and the selected magnetic field intensity of one section of weak magnetic is 0.06～0.1T, it is thus achieved that one section of concentrate and one section of mine tailing；

Step 5, one section of concentrate being added in the 3rd wet magnetic separator, it is selected to carry out the weak magnetic of two-stage nitration, and the selected magnetic field intensity of the weak magnetic of two-stage nitration is 0.04 ~ 0.08T, it is thus achieved that iron ore concentrate and two-stage nitration mine tailing；Two-stage nitration mine tailing returns step 3.

The method extracting iron ore concentrate from flyash the most according to claim 1, it is characterised in that described flyash: TFe is 5 ~ 15%, and magnetic iron ore accounts for 45 ~ 70wt% of all iron content, SiO₂Content is 40 ~ 60wt%；The described flyash granularity content less than 0.074mm is 50 ~ 75wt%.