Bayer process alumina online desulfurization control method

Abstract

The invention discloses a Bayer process aluminum oxide online desulfurization control method, which comprises the following steps of: controlling the total sulfur content of precise ore blending of high-sulfur ore and low-sulfur ore to be 0.50-0.70%, performing grade grading on bauxite according to an aluminum-silicon ratio (A / S), oxidizing low-valence sulfur into high-valence sulfur by using an oxidizing substance as an online desulfurizing agent in a dissolution stage, and removing the high-valence sulfur from the low-valence sulfur by using the oxidizing substance as an online desulfurizing agent. High temperature-low calcium regulation and control are carried out according to corresponding silicon ratio (A / S) grading, so that synergistic coupling regulation and control of dissolution temperature-ash calcium-silicon ratio (C / S)-bauxite silicon-containing mineral form is realized to promote discharge of high-valence sulfur in the sodium aluminate solution along with red mud; according to the method, the negative bivalent sulfur in the Bayer process system can be quickly oxidized into high-valence sulfur, and the high-valence sulfur can be quickly discharged from the Bayer process system, so that the adverse effect caused by sulfur accumulation of the Bayer process system is eliminated, the desulfurization effect is improved, the sulfur-containing control limit of bauxite is widened, and the maximum utilization of high-sulfur bauxite resources is realized.

Description

Technical Field

[0001] The invention relates to an online desulfurization control method for Bayer process alumina, and belongs to the technical field of online desulfurization in the process of producing alumina by the Bayer process. Background Art

[0002] With the gradual depletion of domestic bauxite resources, the grade of bauxite is getting worse and worse, and the impurity sulfur content in bauxite is getting higher and higher. In particular, the sulfur content of bauxite in Maochang, Qingzhen, Guizhou is basically above 1.5%, and can reach up to 3.0%. The proven reserves of high-sulfur bauxite resources exceed 200 million tons. The sulfur in bauxite ore mainly exists in the form of pyrite. In the process of producing alumina by Bayer process, the sulfur in bauxite is mainly in the form of low-valent S 2- Enters into the Bayer process sodium aluminate solution in the form of S 2- The presence of S in the sodium aluminate solution is extremely detrimental to the Bayer process alumina production. 2- The accumulation of sulfur seriously affects the operation and control of key links such as dissolution, sedimentation, evaporation, and decomposition, causing corrosion of system equipment, causing the iron content of alumina products to exceed the standard, and reducing the quality of alumina products. High-sulfur bauxite desulfurization methods such as ore dressing desulfurization, roasting desulfurization, and microbial desulfurization can prevent sulfur in the ore from entering the Bayer process alumina production system from the source. However, this method has complex process flow and high investment costs and has not yet been widely promoted and applied in industry. Therefore, there is no relatively mature process in China to directly use high-sulfur bauxite to produce alumina. At present, domestic alumina companies mainly use high-sulfur bauxite and low-sulfur bauxite in combination. The online desulfurization method in the alumina production process has the advantages of simple process flow, easy operation, and no need for additional process investment, and is widely used in industry. The online desulfurization methods in the alumina production process include oxidation method, barium salt precipitation method, zinc precipitation method, etc. Due to the high prices of barium salts and zinc substances, desulfurization is not economical and has not been promoted and applied. The sodium nitrate oxidation desulfurization method is widely used by domestic alumina companies and is also a relatively mature desulfurization technology. However, the main function of this method is to oxidize the negative divalent sulfur in the sodium aluminate solution into high-valent sulfur. If the high-valent sulfur in the sodium aluminate solution is not discharged in time, it will cause the total sulfur to accumulate in the sodium aluminate solution, thereby inhibiting the conversion efficiency of negative divalent sulfur to high-valent sulfur, thereby reducing the desulfurization effect, resulting in the sulfur control limit of bauxite being limited. At present, the sulfur content of bauxite in most domestic alumina companies can only be controlled at about 0.4%. When the sulfur content of bauxite exceeds 0.4%, production will be seriously affected. In this case, the sulfur content of bauxite cannot be further improved, which will cause a large amount of high-sulfur bauxite resources to be idle, making it impossible to effectively utilize the high-sulfur bauxite resources.

[0003] That is, a Bayer process alumina online desulfurization control method is needed, which can not only quickly oxidize the negative divalent sulfur in the Bayer process system into high-valent sulfur, but also quickly discharge the high-valent sulfur from the Bayer process system, thereby eliminating the adverse effects of sulfur accumulation in the Bayer process system, improving the desulfurization effect and broadening the sulfur content control limit of bauxite ore, and realizing the maximum utilization of high-sulfur bauxite resources. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a Bayer process alumina online desulfurization control method, which can quickly oxidize the negative divalent sulfur in the Bayer process system into high-valent sulfur, and quickly discharge the high-valent sulfur from the Bayer process system, thereby eliminating the adverse effects of sulfur accumulation in the Bayer process system, improving the desulfurization effect and widening the sulfur control limit of bauxite ore, and realizing the maximum utilization of high-sulfur bauxite resources; it can overcome the shortcomings of the prior art.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] The invention discloses an online desulfurization control method for alumina using the Bayer process. The method controls the total sulfur content of high-sulfur ore and low-sulfur ore to be 0.50-0.70% by precisely blending the ore, and grades the bauxite according to the aluminum-silicon ratio (A / S). In the dissolution stage, an oxidizing substance is used as an online desulfurizing agent to oxidize low-valent sulfur into higher-valent sulfur. High-temperature-low-calcium regulation is performed according to the corresponding silicon ratio (A / S) classification, so as to achieve the coordinated coupling regulation of dissolution temperature-bleaching calcium-silicon ratio (C / S)-bauxite silicon-containing mineral morphology, so as to promote the discharge of higher-valent sulfur in the sodium aluminate solution along with red mud.

[0007] The above-mentioned steps of coordinated coupling regulation of dissolution temperature-lime calcium silicon ratio (C / S)-bauxite silicon-containing minerals are as follows:

[0008] S1: By adjusting the control ratio of different silicon-containing minerals in bauxite to achieve a sodium silicate slag red mud phase structure that is more conducive to chemical coupling with sulfate;

[0009] S2: Using oxidizing substances as online desulfurization agents to oxidize low-valent sulfur into higher-valent sulfur;

[0010] S3: Through high temperature-low calcium coupling regulation, the higher-valent sulfur in the sodium aluminate solution is promoted to enter the sodium silicate slag and red mud discharge system to achieve the balance of total sulfur in the Bayer process system.

[0011] As mentioned above, the dissolution temperature control range is 260-270°C, and the ash-calcium-silicon ratio (C / S) range is 0.6-1.1. Within this temperature control range, high temperature-low calcium control methods are adopted according to different bauxite grades.

[0012] The above-mentioned high temperature-low calcium control method is adopted according to different bauxite grades: the bauxite used is mainly domestic monohydric bauxite, and its aluminum-silicon ratio (A / S) control range is 4.0-8.0. For every 1.0 increase in the aluminum-silicon ratio (A / S) of bauxite, the corresponding optimal lime-calcium-silicon ratio (C / S) increases by 0.10-0.15.

[0013] The above-mentioned method comprises the following steps: a method for controlling online desulfurization of alumina by the Bayer process, wherein when alumina is produced by the Bayer process, the amount of lime added is controlled in stages by online monitoring, and the specific steps are:

[0014] (1) The bauxite raw materials are blended, homogenized, and ground into bauxite powder;

[0015] (2) Calculate the aluminum-silicon ratio based on the content of aluminum oxide and silicon dioxide in the bauxite powder to determine the grade of the bauxite;

[0016] (3) According to the grade of bauxite, select the best lime-calcium-silicon ratio (C / S), and accurately calculate the amount of lime to be added based on the best lime-calcium-silicon ratio grade data.

[0017] The aforementioned oxidizing substance is calcium nitrate.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] 1. The present invention adopts high temperature-low calcium control methods according to different bauxite grades, which is beneficial to increase the total sulfur content in red mud, and can also ensure the dissolution effect of bauxite, and realize the synergistic coupling control of dissolution temperature-lime calcium silicon ratio (C / S)-bauxite silicon-containing mineral morphology to promote the discharge of higher-valent sulfur in sodium aluminate solution with red mud.

[0020] 2. Through the coordinated coupling regulation of dissolution temperature-ash-calcium-silicon ratio (C / S)-silicon mineral morphology of bauxite, the utilization of high-sulfur bauxite is realized, breaking through the limitation that the total sulfur content of the industry's blended ore can only be controlled at about 0.4%, and further improving the upper limit of bauxite sulfur content control. The total sulfur content of high-sulfur ore and low-sulfur ore can be accurately controlled in the range of 0.50-0.70%, achieving a breakthrough in the industry, and can increase the use of high-sulfur ore. The annual use of high-sulfur bauxite exceeds 1 million tons, and the large-scale use of high-sulfur bauxite has been initially realized, which better solves the problem of the use of high-sulfur bauxite.

[0021] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] none DETAILED DESCRIPTION

[0023] The preferred embodiments of the present invention are described in detail below. It should be understood that the preferred embodiments are only for illustrating the present invention, rather than for limiting the protection scope of the present invention.

[0024] The invention discloses an online desulfurization control method for alumina by Bayer process. The method controls the total sulfur content of accurate ore blending of high-sulfur ore and low-sulfur ore within a range of 0.50-0.70%, so that the total sulfur content in the bauxite ore is in a relatively stable state; the bauxite is graded according to the aluminum-silicon ratio (A / S); in the dissolution stage, an oxidizing substance is used as an online desulfurizing agent to oxidize low-valent sulfur into higher-valent sulfur; and high-temperature-low-calcium regulation is performed according to the corresponding silicon ratio (A / S) classification, so as to achieve the coordinated coupling regulation of dissolution temperature-bleed calcium-silicon ratio (C / S)-bauxite silicon-containing mineral morphology, promote the discharge of higher-valent sulfur in the sodium aluminate solution with red mud, and at the same time, the process eliminates the negative impact of the accumulation of negative divalent sulfur and total sulfur in the Bayer process system on the alumina production process.

[0025] The steps involved in the coordinated coupling regulation of dissolution temperature-lime calcium silicon ratio (C / S)-bauxite silicon-containing minerals are:

[0026] S1: By adjusting the control ratio of different silicon-containing minerals in bauxite to achieve a sodium silicate slag red mud phase structure that is more conducive to chemical coupling with sulfate;

[0027] S2: using an oxidizing substance as an online desulfurizing agent to oxidize low-valent sulfur into higher-valent sulfur, wherein the oxidizing substance is calcium nitrate;

[0028] S3: Through high temperature-low calcium coupling regulation, the higher-valent sulfur in the sodium aluminate solution is promoted to enter the sodium silicate slag and red mud discharge system to achieve the balance of total sulfur in the Bayer process system.

[0029] The dissolution temperature control range is 260-270℃, and the lime-calcium-silicon ratio (C / S) range is 0.6-1.1. Within this temperature control range, high temperature-low calcium control methods are used according to different bauxite grades, which is beneficial to increase the total sulfur content in red mud and ensure the dissolution effect of bauxite.

[0030] According to the different grades of bauxite, the high temperature-low calcium control method is adopted: the bauxite used is mainly domestic monohydric bauxite, and its aluminum-silicon ratio (A / S) control range is 4.0-8.0. For every 1.0 increase in the aluminum-silicon ratio (A / S) of bauxite, the corresponding optimal lime-calcium-silicon ratio (C / S) increases by 0.10-0.15.

[0031] The method comprises the following steps: when producing alumina by the Bayer process, the amount of lime added is controlled in stages by online monitoring, and the specific steps are:

[0032] (1) The bauxite raw materials are blended, homogenized, and ground into bauxite powder;

[0033] (2) Calculate the aluminum-silicon ratio based on the content of aluminum oxide and silicon dioxide in the bauxite powder to determine the grade of the bauxite;

[0034] (3) According to the grade of bauxite, select the best lime-calcium-silicon ratio (C / S), and accurately calculate the amount of lime to be added based on the best lime-calcium-silicon ratio grade data.

[0035] In the dissolution process, high temperature-low calcium regulation is carried out according to the corresponding aluminum-silicon ratio (A / S) classification, and the dissolution temperature control range is 260-270°C; the optimal ash-calcium-silicon ratio (C / S) is selected according to the corresponding aluminum-silicon ratio (A / S) and the dissolution temperature control method.

[0036] Implementation Example 1 (Experimental Research Results)

[0037] As shown in Table 1-1, at the same dissolution temperature, the higher the C / S ratio of the ash, the lower the sulfur content in the red mud. The use of a low calcium ratio formula can effectively promote the increase in the sulfur content in the red mud, which is beneficial to the removal of sulfur in the Bayer process system.

[0038] Table 1-1. Research results on the effect of ash mix C / S on the sulfur content of red mud dissolved from bauxite

[0039] Gray C / S Dissolution temperature / ℃ Dissolution time / min Total sulfur content of red mud / % 0.6 265 60 1.06 0.7 265 60 1.00 0.8 265 60 0.95 0.9 265 60 0.90 1.0 265 60 0.89 1.1 265 60 0.83

[0040] As shown in Table 1-2, when the dissolution temperature is 260℃, the best ash C / S is 0.8, and the relative dissolution rate is 97.27%; when the dissolution temperature is 265℃, the best ash C / S is 0.7, and the relative dissolution rate is 97.36%; when the dissolution temperature is 270℃, the best ash C / S is 0.7, and the relative dissolution rate is 98.04%. Under the condition of the best dissolution effect of bauxite, increasing the dissolution temperature can reduce the control conditions of ash C / S. Therefore, the use of high temperature and low calcium formula is more conducive to increasing the sulfur content in red mud, ensuring that the total sulfur in the sodium aluminate solution of the Bayer system does not accumulate, and achieving the balance of sulfur inflow and outflow.

[0041] Table 1-2. Research results on the effect of dissolution temperature on ash blending C / S and dissolved red mud sulfur content

[0042]

[0043] Implementation Example 2 (Actual Production Operation Results)

[0044] As shown in Table 2-1, when the actual production dissolution temperature is controlled at 267±2℃, the relative dissolution rate is not less than 95%. Under this condition, the C / S of the ash blend is reduced, the total sulfur content in the red mud is increased, the sulfur content index of the bauxite is continuously improved, and the total sulfur concentration in the Bayer process system is steadily decreasing. Therefore, in actual production, while ensuring that the dissolution temperature remains basically unchanged, reducing the C / S of the ash blend is more conducive to increasing the sulfur content in the red mud and continuously improving the sulfur content index of the bauxite, and will not cause the accumulation of total sulfur in the Bayer process system, thereby eliminating the adverse effects of the total sulfur accumulation in the system on production.

[0045] Table 2-1. Actual production operation data of the influence of ash C / S on the sulfur content of red mud dissolved from bauxite

[0046]

[0047] This technical solution adopts high temperature-low calcium control method according to different bauxite grades, which is beneficial to increase the total sulfur content in red mud and ensure the dissolution effect of bauxite.

[0048] Before the implementation of the present invention, the content of bauxite used in production was controlled within the range of 0.3-0.4%, and the annual consumption of high-sulfur ore was about 600,000 tons;

[0049] After the implementation of the present invention, the sulfur content of bauxite is gradually increased to 0.6% and above, and the annual consumption of high-sulfur bauxite exceeds 1 million tons.

[0050] The above description is only a preferred embodiment of the present invention and does not constitute any form of confidentiality restriction on the present invention. Any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the present invention without departing from the technical solution of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A Bayer process alumina online desulfurization control method, characterized in that: This method controls the total sulfur content of high-sulfur ore and low-sulfur ore in the precise blending range of 0.50-0.70%, and grades bauxite according to the aluminum-silicon ratio (A / S). In the dissolution stage, oxidizing substances are used as online desulfurizers to oxidize low-valent sulfur into higher-valent sulfur, and high-temperature-low-calcium regulation is performed according to the corresponding silicon ratio (A / S) classification, thereby achieving synergistic coupling regulation of dissolution temperature-blending calcium-silicon ratio (C / S)-bauxite silicon-containing mineral morphology to promote the discharge of higher-valent sulfur in sodium aluminate solution with red mud.

2. The Bayer process alumina online desulfurization control method according to claim 1, characterized in that: The steps involved in the coordinated coupling regulation of dissolution temperature-lime calcium silicon ratio (C / S)-bauxite silicon-containing minerals are: S1: By adjusting the control ratio of different silicon-containing minerals in bauxite to achieve a sodium silicate slag red mud phase structure that is more conducive to chemical coupling with sulfate; S2: Using oxidizing substances as online desulfurization agents to oxidize low-valent sulfur into higher-valent sulfur; S3: Through high temperature-low calcium coupling regulation, the higher-valent sulfur in the sodium aluminate solution is promoted to enter the sodium silicate slag and red mud discharge system to achieve the balance of total sulfur in the Bayer process system.

3. The Bayer process alumina online desulfurization control method according to claim 2, characterized in that: The dissolution temperature control range is 260-270℃, and the ash-calcium-silicon ratio (C / S) range is 0.6-1.

1. Within this temperature control range, high temperature-low calcium control methods are adopted according to different bauxite grades.

4. The Bayer process alumina online desulfurization control method according to claim 3, characterized in that: The high temperature-low calcium control method is adopted according to different bauxite grades: the bauxite used is mainly domestic monohydric bauxite, and its aluminum-silicon ratio (A / S) control range is 4.0-8.

0. For every 1.0 increase in the aluminum-silicon ratio (A / S) of the bauxite, the corresponding optimal lime-calcium-silicon ratio (C / S) increases by 0.10-0.

15.

5. The Bayer process alumina online desulfurization control method according to claim 1, characterized in that: It includes the following steps: When using the Bayer process to produce alumina, the amount of lime added is controlled in stages using online monitoring. The specific steps are: (1) The bauxite raw materials are blended, homogenized, and ground into bauxite powder; (2) Calculate the aluminum-silicon ratio based on the content of alumina and silicon dioxide in the bauxite powder to determine the grade of the bauxite; (3) According to the grade of bauxite, select the best lime-calcium-silicon ratio (C / S), and accurately calculate the amount of lime to be added based on the best lime-calcium-silicon ratio grade data.

6. The Bayer process alumina online desulfurization control method according to any one of claims 1 to 5, characterized in that: The oxidizing substance is calcium nitrate.

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