阅读说明：本技术 一种铬铁矿无钙焙烧提取铬的方法 (Method for extracting chromium from chromite by calcium-free roasting ) 是由 段静 商琴 侯礼强 陈明轩 廖荣 陈丹 程西川 于 2021-03-17 设计创作，主要内容包括：本发明公开了一种铬铁矿无钙焙烧提取铬的方法,包括以下步骤：将铬铁矿、纯碱、添加剂按一定比例混合均匀；将混匀后的物料加氢氧化钠的水溶液造球；将制好的球布入转底炉或辊道窑中,在富氧条件下进行焙烧；将焙烧后的熟料经过湿磨、过滤、洗涤,得到铬酸钠浸出液和残渣。本发明选用的添加剂廉价易得,能显著提高铬的转化率；没有引入新的成分进入残渣,同时使铁元素在残渣中富集。采用本技术后,残渣中Cr-2O-3和Fe-2O-3的含量分别可以达到2wt％以下和60wt％以上,可直接与铁矿石混合作为炼钢原料,使残渣的资源化利用价值大大增加。(The invention discloses a method for extracting chromium from chromite by calcium-free roasting, which comprises the following steps: mixing chromite, soda ash and an additive uniformly according to a certain proportion; pelletizing the uniformly mixed material by adding an aqueous solution of sodium hydroxide; distributing the prepared balls into a rotary hearth furnace or a roller kiln, and roasting under the condition of oxygen enrichment; wet grinding, filtering and washing the roasted clinker to obtain sodium chromate leaching solution and residue. The additive selected by the invention is cheap and easy to obtain, and can obviously improve the conversion rate of chromium; no new components are introduced into the residue while the iron element is enriched in the residue. After the technology is adopted, Cr in the residue 2 O 3 And Fe 2 O 3 The content of the slag can respectively reach below 2 wt% and above 60 wt%, and the slag can be directly mixed with iron ore to be used as a steelmaking raw material, so that the resource utilization value of the slag is greatly increasedAnd (4) increasing.)

1. A method for extracting chromium from chromite by calcium-free roasting is characterized by comprising the following steps:

(1) mixing chromite, soda ash and additive powder uniformly according to a certain proportion;

(2) pelletizing the uniformly mixed material by adding an aqueous solution of sodium hydroxide;

(3) distributing the prepared balls into a rotary hearth furnace or a roller kiln, and roasting under the condition of oxygen enrichment;

(4) wet grinding, filtering and washing the roasted clinker to obtain sodium chromate leaching solution and residue.

2. The method for extracting chromium from chromite by calcium-free roasting according to claim 1, wherein the chromite contains Cr as a main component₂O₃And Fe₂O₃Wherein Cr is₂O₃42～50wt％、Fe₂O₃28～34wt％。

3. The process for calcium-free roasting extraction of chromium from chromite ore according to claim 1, wherein the additive is an oxide or hydroxide of iron; or an ore containing an oxide or hydroxide of iron as a main component; or waste residues with iron oxides or hydroxides as main components; or any combination of the above.

4. The method for extracting chromium from chromite by calcium-free roasting according to claim 1, wherein in the step 1, the chromite, the soda ash and the additive are 150-200 meshes of powder; the mass ratio of the components is 100 to (70-90) to (3-20), preferably 100 to (75-85) to (5-13).

5. The method for extracting chromium from chromite by calcium-free roasting according to claim 1, wherein return slag is also added in the step 1; the return slag is the residue, wherein Fe₂O₃58～70wt％、Cr₂O₃1.2～1.9wt％。

6. The method for extracting chromium from chromite by calcium-free roasting according to claim 1, wherein the mass ratio of sodium hydroxide to soda ash in the step 2 is 1: 7-10, preferably 1: 8-9.

7. The method for extracting chromium from chromite by calcium-free roasting according to claim 1, wherein the pellet obtained in the step 2 has a particle size of 5-16 mm and a water content of 8-15 wt%.

8. The method for extracting chromium from chromite by calcium-free roasting according to claim 1, wherein the pellets in step 3 sequentially pass through a preheating zone, a high temperature zone and a cooling zone after entering the rotary hearth furnace or the roller kiln.

9. The method for extracting chromium from chromite by calcium-free roasting according to claim 1, wherein in the step 3, the roasting temperature is 800-1100 ℃ and the roasting time is 1-5 h; preferably, the temperature of the high-temperature zone is 950-1050 ℃, and the roasting time is 2-4 h; pure oxygen is filled during high-temperature roasting.

10. The method for extracting chromium from chromite by calcium-free roasting according to claim 1, wherein the residue Cr in the step 4₂O₃And Fe₂O₃The content of (A) is respectively less than 2 wt% and more than 60 wt%; a part of the returnStep 1 is used as return slag, and the other part is used as a steelmaking raw material for resource utilization.

Technical Field

The invention belongs to the technical field of inorganic salt production, and particularly relates to a method for extracting chromium from chromite by calcium-free roasting.

Background

In the field of chromium salt production, pollution of hexavalent chromium to the environment and harm to practitioners are always difficult problems to be solved urgently in the industry. With the improvement of environmental protection requirements and the continuous promotion of green chemical concepts, the traditional calcium-containing roasting process is basically replaced by the advanced calcium-free roasting technology in China in recent years. The calcium-free roasting has small slag discharge amount, avoids generating calcium chromate with carcinogenic risk and becomes a necessary trend for the industrial development of chromium salt. However, in view of the current industrial technology, there are some areas where the calcium-free roasting process needs to be improved. On one hand, in the treatment mode of preventing sintering, although the returned slag is adopted to replace the calcium filler, the problems of low production efficiency and overlarge energy consumption cannot be solved fundamentally; meanwhile, as the reaction raw materials are diluted by a large amount of fillers, the effective contact area between reactants is reduced, the oxidation rate of chromium is further influenced, and effective resources are not fully utilized; in addition, in the recycling of the residues, because the chromium element in the raw materials is not fully reacted, the internal chemical structure is not completely destroyed and decomposed, the distribution of each component in the residues is complex, the separation difficulty among the elements is high, the available iron element is not effectively enriched, the resource utilization difficulty is high, and some enterprises even need additional cost to carry out harmless treatment on the iron element. On the other hand, the traditional roasting process uses equipment which is a rotary kiln, the chromite, the soda ash and the return slag are continuously turned over in the kiln in the form of powder for reaction, and because the proportion of the chromite, the soda ash and the return slag is greatly different, segregation to a certain degree can inevitably occur, so that the materials are not mixed uniformly, and the oxidation rate of chromium is influenced finally. On the whole, the conversion rate of chromium in the calcium-free roasting is still at a lower level, generally about 70-80%, the resource utilization rate needs to be improved, the limitation of return slag on the production efficiency and the energy consumption restrict the improvement of the productivity and the control of the cost, and in addition, an economical and feasible industrial scheme is not formed for the treatment of the residue, so that the calcium-free roasting process has a great promotion space on the basis.

Among these, there is an improvement in which additives are added to the reaction mass. On one hand, the reaction temperature can be reduced, the energy consumption can be saved, on the other hand, the oxidation of chromium components can be promoted, and the conversion rate can be improved, such as Chinese patent CN201210127841.X, Chinese patent CN201710712467.2 and the like. However, in the above-mentioned techniques, the segregation problem which is common in the actual rotary kiln production is not considered, and the effect of the additive is greatly reduced after the segregation of the mixed powder occurs.

Another method is to change the form of the reaction materials, i.e. to change the traditional powder into non-filler granulation, ball pressing, etc., as in Chinese patent CN 201410299115.5. By adopting the mode, the precipitation of liquid phase quantity can be avoided under the condition of no filler, and the production efficiency is improved; secondly, compared with powder, the components of the material after granulation and ball pressing are more stable and uniform, and segregation is effectively avoided. However, due to the limitation of technical conditions and process requirements, the compression strength of the pellets is limited, and the pellets are inevitably damaged to a certain extent in the roasting process in the rotary kiln to form powder, and finally, the problems of sintering and ring formation are generated, so that the continuous production is influenced.

In conclusion, the improvement of the chromite calcium-free roasting process in the prior art is in a pilot plant test or a pilot plant test stage, and the economical efficiency, the practicability and the feasibility do not meet the industrial requirements yet, so that certain defects exist in all aspects. Therefore, a new calcium-free roasting process with low cost, high conversion rate and high productivity, which can be industrialized on a large scale, is urgently needed to be developed so as to realize the high-efficiency utilization of resources and make the recycling of the chromium slag have higher economic value.

Disclosure of Invention

The invention aims to provide a method for extracting chromium from chromite by calcium-free roasting, and simultaneously realizes a calcium-free roasting process with large-scale industrialization, low cost, high conversion rate and high production efficiency; the invention also aims to greatly reduce the content of chromium element in the chromium slag, realize the enrichment of iron element in the chromium slag while extracting chromium and thoroughly solve the problem of resource treatment of the chromium slag.

In order to realize the purpose, the technical scheme is as follows:

a method for extracting chromium from chromite by calcium-free roasting comprises the following steps:

(1) mixing chromite, soda ash and an additive uniformly according to a certain proportion;

(2) pelletizing the uniformly mixed material by adding an aqueous solution of sodium hydroxide;

(3) distributing the prepared balls into a rotary hearth furnace or a roller kiln, and roasting under the condition of oxygen enrichment;

(4) wet grinding, filtering and washing the roasted clinker to obtain sodium chromate leaching solution and residue.

According to the scheme, the chromite mainly comprises Cr₂O₃And Fe₂O₃Wherein Cr is₂O₃42～50wt％、Fe₂O₃28～34wt％。

According to the scheme, the additive is an oxide or hydroxide of iron; or an ore containing an oxide or hydroxide of iron as a main component; or waste residues with iron oxides or hydroxides as main components; or any combination of the above. Such as iron ore concentrate, hematite, pigment iron red.

According to the scheme, in the step 1, the chromite, the soda ash and the additive are 150-200 meshes of powder; the mass ratio of the components is 100 to (70-90) to (3-20), preferably 100 to (75-85) to (5-13).

According to the scheme, return slag is also added in the step 1; the return slag is the slag with basically stable components after reaction circulation is carried out for multiple times, wherein Fe₂O₃58～70wt％、Cr₂O₃1.2 to 1.9 wt%. In the case of adding the return slag, the mass ratio of the chromite to the soda ash to the additive to the return slag is 100 to (70-90) to (3-20) to (10-50), and preferably 100 to (75-85) to (5-13) to (10-20).

According to the scheme, the mass ratio of the sodium hydroxide to the sodium carbonate in the step 2 is 1: 7-10, and preferably 1: 8-9.

According to the scheme, the pellet obtained in the step 2 has the particle size of 5-16 mm and the water content of 8-15 wt%.

According to the scheme, the pellets in the step 3 enter a rotary hearth furnace or a roller kiln and then sequentially pass through a preheating zone, a high-temperature zone and a cooling zone. Wherein the preheating zone preheats and dries; carrying out high-temperature zone roasting reaction; and cooling the cooling zone to prepare for discharging.

According to the scheme, in the step 3, the roasting temperature of the high-temperature zone is 800-1100 ℃, and the total roasting time is 1-5 h; preferably, the temperature of the high-temperature zone is 950-1050 ℃, and the total roasting time is 2-4 h.

According to the scheme, pure oxygen is filled in the step 3 during high-temperature roasting.

According to the scheme, the residue Cr is obtained in the step 4₂O₃And Fe₂O₃The content of (A) is respectively less than 2 wt% and more than 60 wt%; one part is returned to the step 1 as return slag, and the other part can be used as a steelmaking raw material, a slagging agent or a cement mineralizer.

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

(1) the selected additive is cheap and easy to obtain, and the conversion rate of chromium can be obviously improved; no new components are introduced into the residue while the iron element is enriched in the residue. Cr in residue in traditional calcium-free roasting technology₂O₃And Fe₂O₃The content of (B) is usually around 8 wt% and 45 wt%. After the technology is adopted, Cr₂O₃And Fe₂O₃The content of the slag can reach below 2 wt% and above 60 wt%, and the slag can be directly mixed with iron ore to be used as a steelmaking raw material, so that the resource utilization value of the slag is greatly increased.

(2) The method reduces or avoids the use of return slag, improves the working efficiency and reduces the energy consumption of the existing calcium-free roasting process when the return slag is continuously circulated. In the traditional calcium-free roasting technology, the raw material is in the form of powder, and in order to prevent sintering, the addition amount of return slag is 2 times or even higher than that of chromite. After the technology adopts the pelletizing or ball pressing process, the return slag can not be added into the raw materials or only the return slag with the total amount of 50wt percent of the chromite at most is added into the raw materials, so that the production capacity of equipment is improved, and the heat energy consumed by continuous circulation of a large amount of return slag in high-temperature roasting (about 1000 ℃) to water leaching chromium (about 100 ℃) is also avoided.

(3) The method avoids the segregation of the materials through granulation (or ball pressing and cake pressing) and static roasting equipment, so that the materials are more uniformly distributed and contacted more fully during the reaction, and the function of the additive is effectively exerted; meanwhile, the gap in the spherical material can fix the amount of liquid phase separated out by reaction, and the materials can be effectively prevented from being bonded in a proper temperature range.

Detailed Description

The following examples further illustrate the technical solutions of the present invention, but should not be construed as limiting the scope of the present invention.

The invention provides a method for extracting chromium from chromite by calcium-free roasting, which mainly comprises the following steps:

(1) mixing chromite, soda ash and an additive uniformly according to a certain proportion;

(2) pelletizing the uniformly mixed material by adding an aqueous solution of sodium hydroxide;

(3) distributing the prepared balls into a rotary hearth furnace or a roller kiln, and roasting under the condition of oxygen enrichment;

(4) wet grinding, filtering and washing the roasted clinker to obtain sodium chromate leaching solution and residue.

Wherein the chromite mainly comprises Cr₂O₃And Fe₂O₃Wherein Cr is₂O₃42～50wt％、Fe₂O₃28～34wt％。

The additive is an oxide or hydroxide of iron; or an ore containing an oxide or hydroxide of iron as a main component; or waste residues with iron oxides or hydroxides as main components; or any combination of the above. Such as iron ore concentrate, hematite, pigment iron red.

Cr in residue in traditional calcium-free roasting technology₂O₃And Fe₂O₃The content of (B) is usually around 8 wt% and 45 wt%. By adopting the method, Cr in the obtained residues₂O₃And Fe₂O₃The content of the slag can reach below 2 wt% and above 60 wt%, and the slag can be directly mixed with iron ore to be used as a steelmaking raw material, so that the resource utilization value of the slag is greatly increased.

In the specific implementation process, the chromite, the soda ash and the additive in the step 1 are powder materials, and the powder materials are 150-200 meshes; the mass ratio of the components is 100 to (70-90) to (3-20), preferably 100 to (75-85) to (5-13).

The invention also comprises the condition that the return slag is added in the step 1; the return slag is the slag with basically stable components after reaction circulation is carried out for multiple times, wherein Fe₂O₃58～70wt％、Cr₂O₃1.2 to 1.9 wt%. In the case of adding the return slag, the mass ratio of the chromite to the soda ash to the additive to the return slag is 100 to (70-90) to (3-20) to (10-50), and preferably 100 to (75-85) to (5-13) to (10-20).

In the step 2, the mass ratio of the sodium hydroxide to the sodium carbonate is 1 to (7-10), preferably 1 to (8-9). The obtained pellets have the particle size of 5-16 mm and the water content of 8-15 wt%.

And 3, the pellets enter a rotary hearth furnace or a roller kiln and then sequentially pass through a preheating zone, a high-temperature zone and a cooling zone. Wherein the preheating zone preheats and dries; carrying out high-temperature zone roasting reaction; and cooling the cooling zone to prepare for discharging. The high-temperature zone roasting temperature is 800-1100 ℃, and the total roasting time is 1-5 h; preferably, the temperature of the high-temperature zone is 950-1050 ℃, and the total roasting time is 2-4 h. Pure oxygen is filled during high-temperature roasting.

4, using a part of the residue in the step 1 as return slag; the rest can be directly recycled.

Example 1

A method for extracting chromium from chromite by calcium-free roasting comprises the following steps:

(1) grinding the chromite, the soda ash, the additive and the return slag to 150-200 meshes, and uniformly mixing according to a certain proportion. Wherein the chromite is mainly composed of Cr₂O₃45.67wt％、Fe₂O₃30.46 wt%; return slag main component Fe₂O₃60.30wt％、Cr₂O₃1.39 wt%; the additive is iron ore concentrate; the mass ratio of the chromite, the soda ash, the additive and the return slag is 100: 85: 5: 20.

(2) Adding the sodium hydroxide aqueous solution into the uniformly mixed material for pelletizing. Wherein the mass ratio of the sodium hydroxide to the sodium carbonate is 1: 9; the pellet particle size is 8-14 mm, and the water content is 14.95 wt%.

(3) And (3) distributing the prepared balls into a roller kiln, and roasting under the oxygen-enriched condition. The temperature of a preheating zone in the roasting equipment is 600-800 ℃, the temperature of a high-temperature zone is 800-1050 ℃, the temperature of a cooling zone is 1050-850 ℃, and the residence time is 40min, 60min and 20min respectively. Pure oxygen is introduced into the reactor at a high temperature zone.

(4) Wet grinding, filtering and washing the roasted clinker to obtain sodium chromate leaching solution and residue. Wherein the extraction rate of chromium is 92.58%; fe in the obtained residue₂O₃60.47wt％、Cr₂O₃1.41wt％。

Example 2

A method for extracting chromium from chromite by calcium-free roasting comprises the following steps:

(1) grinding the chromite, the soda ash, the additive and the return slag to 150-200 meshes, and uniformly mixing according to a certain proportion. Wherein the chromite is mainly composed of Cr₂O₃48.92％、Fe₂O₃28.73%; return slag main component Fe₂O₃58.49％、Cr₂O₃1.62 percent; the additive is hematite; the mass ratio of the chromite, the soda ash, the additive and the return slag is 100: 88: 20: 10.

(2) Adding the sodium hydroxide aqueous solution into the uniformly mixed material for pelletizing. Wherein the mass ratio of the sodium hydroxide to the sodium carbonate is 1: 7; the pellet has a particle size of 5-12 mm and water content of 10.94 wt%.

(3) And (3) distributing the prepared balls into a roller kiln, and roasting under the oxygen-enriched condition. The temperature of a preheating zone in the roasting equipment is 650-1000 ℃, the temperature of a high-temperature zone is 1000-1100 ℃, the temperature of a cooling zone is 1100-900 ℃, and the residence time is 160min, 80min and 60min respectively. Pure oxygen is introduced into the reactor at a high temperature zone.

(4) Wet grinding, filtering and washing the roasted clinker to obtain sodium chromate leaching solution and residue. Wherein the extraction rate of chromium is 95.30 percent; fe in the obtained residue₂O₃59.49wt％、Cr₂O₃1.29wt％。

Example 3

A method for extracting chromium from chromite by calcium-free roasting comprises the following steps:

(1) will be provided withThe chromite, the soda ash, the additive and the return slag are ground to 150-200 meshes and uniformly mixed according to a certain proportion. Wherein the chromite is mainly composed of Cr₂O₃49.86％、Fe₂O₃31.57 percent; return slag main component Fe₂O₃66.31％、Cr₂O₃1.59 percent; the additive is a mixture of iron ore concentrate and pigment iron oxide red; the mass ratio of the chromite, the soda ash, the additive and the return slag is 100: 90: 16: 50, wherein the mass ratio of the iron ore concentrate to the pigment iron oxide red is 1: 3.

(2) Adding the sodium hydroxide aqueous solution into the uniformly mixed material for pelletizing. Wherein the mass ratio of the sodium hydroxide to the sodium carbonate is 1: 8; the pellet particle size is 6-10 mm, and the water content is 12.47 wt%.

(3) And (4) distributing the prepared balls into a rotary hearth furnace, and roasting under the oxygen-enriched condition. The temperature of a preheating zone in the roasting equipment is 700-950 ℃, the temperature of a high-temperature zone is 950-1050 ℃, the temperature of a cooling zone is 1050-900 ℃, and the residence time is 20min, 30min and 10min respectively. Pure oxygen is introduced into the reactor at a high temperature zone.

(4) Wet grinding, filtering and washing the roasted clinker to obtain sodium chromate leaching solution and residue. Wherein the extraction rate of chromium is 90.99%; fe in the obtained residue₂O₃61.55wt％、Cr₂O₃1.81wt％。

Example 4

A method for extracting chromium from chromite by calcium-free roasting comprises the following steps:

(1) grinding the chromite, the soda ash and the additive to 150-200 meshes, and uniformly mixing according to a certain proportion. Wherein the chromite is mainly composed of Cr₂O₃42.21wt％、Fe₂O₃34.01 wt%; the additive is pigment iron oxide red; the mass ratio of the chromite, the soda ash and the additive is 100: 70: 3.

(2) Adding the sodium hydroxide aqueous solution into the uniformly mixed material for pelletizing. Wherein the mass ratio of the sodium hydroxide to the sodium carbonate is 1: 10; the pellet particle size is 9-16 mm, and the water content is 8.12 wt%.

(3) And (4) distributing the prepared balls into a rotary hearth furnace, and roasting under the oxygen-enriched condition. The temperature of a preheating zone in the roasting equipment is 700-850 ℃, the temperature of a high-temperature zone is 850-1050 ℃, the temperature of a cooling zone is 1050-900 ℃, and the residence time is 40min, 80min and 20min respectively. Pure oxygen is introduced into the reactor at a high temperature zone.

(4) Wet grinding, filtering and washing the roasted clinker to obtain sodium chromate leaching solution and residue. Wherein the extraction rate of chromium is 93.90%; fe in the obtained residue₂O₃60.88wt％、Cr₂O₃1.62wt％。

Example 5

A method for extracting chromium from chromite by calcium-free roasting comprises the following steps:

(1) grinding the chromite, the soda ash and the additive to 150-200 meshes, and uniformly mixing according to a certain proportion. Wherein the chromite is mainly composed of Cr₂O₃46.62wt％、Fe₂O₃32.78 wt%; the additive is iron ore concentrate; the mass ratio of the chromite, the soda ash and the additive is 100: 80: 7.

(2) Adding the sodium hydroxide aqueous solution into the uniformly mixed material for pelletizing. Wherein the mass ratio of the sodium hydroxide to the sodium carbonate is 1: 9; the pellet particle size is 7-13 mm, and the water content is 9.31 wt%.

(3) And (3) distributing the prepared balls into a roller kiln, and roasting under the oxygen-enriched condition. The temperature of a preheating zone in the roasting equipment is 700-900 ℃, the temperature of a high-temperature zone is 900-1050 ℃, the temperature of a cooling zone is 1050-950 ℃, and the residence time is 50min, 100min and 20min respectively. Pure oxygen is introduced into the reactor at a high temperature zone.

(4) Wet grinding, filtering and washing the roasted clinker to obtain sodium chromate leaching solution and residue. Wherein the extraction rate of chromium is 93.90%; fe in the obtained residue₂O₃62.74wt％、Cr₂O₃1.50wt％。

Example 6

A method for extracting chromium from chromite by calcium-free roasting comprises the following steps:

(1) grinding the chromite, the soda ash and the additive to 150-200 meshes, and uniformly mixing according to a certain proportion. Wherein the chromite is mainly composed of Cr₂O₃47.72wt％、Fe₂O₃30.69 wt%; the additive is a mixture of hematite and pigment iron red; the mass ratio of the chromite to the soda ash to the additive is 100: 85: 15, wherein the mass ratio of the hematite to the pigment iron red is1∶4。

(2) Adding the sodium hydroxide aqueous solution into the uniformly mixed material for pelletizing. Wherein the mass ratio of the sodium hydroxide to the sodium carbonate is 1: 10; the pellet particle size is 9-16 mm, and the water content is 11.32 wt%.

(3) And (4) distributing the prepared balls into a rotary hearth furnace, and roasting under the oxygen-enriched condition. The temperature of a preheating zone in the roasting equipment is 700-1000 ℃, the temperature of a high-temperature zone is 1000-1050 ℃, the temperature of a cooling zone is 1050-900 ℃, and the residence time is 60min, 100min and 20min respectively. Pure oxygen is introduced into the reactor at a high temperature zone.

(4) Wet grinding, filtering and washing the roasted clinker to obtain sodium chromate leaching solution and residue. Wherein the extraction rate of chromium is 94.57%; fe in the obtained residue₂O₃63.93wt％、Cr₂O₃1.57wt％。