Method for continuously decomposing molybdenum calcine at low pressure

Abstract

The invention provides a method for continuously decomposing molybdenum calcine at low pressure, which comprises the following steps: 1) uniformly mixing the molybdenum calcine with water, liquid caustic soda and a strong oxidant, and carrying out size mixing; (2) the slurry obtained in the step (1) is continuously leached, needed heat is introduced in the reaction process, certain pressure is maintained, and molybdenum is continuously leached in the form of sodium molybdate and left in the solution; a multi-stage continuous leaching mode is adopted, and after it is ensured that the feed liquid of the last stage is completely qualified, continuous discharging is conducted; and (3) carrying out continuous filter pressing under the operation pressure of 20-25MPa, and separating the sodium molybdate solution from the slag phase. The method is completed by adopting low-pressure leaching equipment, the automation degree of operation is improved, meanwhile, high-pressure equipment is omitted, the field safety operation risk is reduced, the operation process is simple, the decomposition cost is low, and the efficiency is high.

Description

Technical Field

[0001] The invention relates to the technical field of molybdenum roasted sand decomposition, and relates to a method for continuously decomposing molybdenum roasted sand at low pressure. Background Art

[0002] Industrial molybdenum oxide, also known as roasted molybdenum concentrate and molybdenum roasted sand, is not only the main molybdenum product added to alloys, but also the raw material for making ferromolybdenum and producing ammonium molybdate. At present, the industry generally adopts high-pressure alkaline leaching to treat molybdenum roasted sand, so that industrial molybdenum trioxide enters the solution in the form of sodium molybdate, which is mainly divided into the following types:

[0003] One is to use high temperature and high pressure combined with reaction with alkali solution to make soluble molybdenum oxide enter the solution.

[0004] The second method is to use a strong oxidant to convert the low-valent molybdenum in the molybdenum roasted sand into a high-valent molybdenum, which then reacts with a strong base to form sodium molybdate and enters the solution.

[0005] Third, under high temperature and high pressure, ammonium molybdate solution is produced by utilizing the strong binding ability of ammonia and molybdate ions in concentrated ammonia water.

[0006] However, the prior art has the following shortcomings:

[0007] First, the reactor is a high-pressure equipment, and high temperature and high pressure pose safety risks.

[0008] Second, the metal recovery rate is low.

[0009] Third, the current single batch operation is unstable. Under high temperature and high pressure, a large amount of impurity ions are leached into the solution at the same time, making it difficult to separate the subsequent impurities. When decomposing the roasted sand, the solution must be removed while impurities are removed. The workers' work efficiency is low and there is a problem of long operation cycle.

[0010] Fourth, the decomposition cost is high and the process operation is complicated. Summary of the invention

[0011] In view of the above problems, the purpose of the present invention is to provide a method for low-pressure continuous decomposition of molybdenum roasted sand, eliminate high-pressure equipment, reduce the risk of on-site safety operations, and improve the degree of automation of the operation.

[0012] The technical solution adopted by the present invention to achieve the technical purpose is:

[0013] A method for continuously decomposing molybdenum roasted sand at low pressure, comprising:

[0014] 1) mixing molybdenum roasted sand with water, liquid caustic soda and strong oxidant uniformly to prepare slurry;

[0015] 2) Continuously leaching the slurry obtained in step 1), introducing the required heat during the reaction and maintaining a certain pressure, so that molybdenum is continuously leached in the form of sodium molybdate and remains in the solution; adopting a multi-stage continuous leaching method and ensuring that the last stage of the slurry is fully qualified, and then continuously discharging the material;

[0016] 3) Continuously filter under an operating pressure of 20-25 MPa to separate the sodium molybdate solution from the slag phase.

[0017] Preferably, in step 1), molybdenum roasted sand is added to the aqueous solution in a ratio of 1:5.

[0018] Preferably, in step 1), liquid caustic soda NaOH and a strong oxidant NaNO are added in an amount theoretically required for complete reaction with molybdenum. 3 .

[0019] Preferably, in step 2), at a flow rate of 20 m 3 / h and pumping the slurry obtained in step 1) into a continuous leaching reactor.

[0020] Preferably, in step 2), steam is introduced to make the reaction temperature 110°C.

[0021] Preferably, in step 2), the pressure is maintained at 0.3 Mpa.

[0022] Preferably, in step 2), the stirring speed at each stage is 110 rpm.

[0023] Preferably, in step 2), the continuous discharging process needs to be cooled continuously and the material temperature is kept below 50°C.

[0024] The beneficial effects of the present invention are: low-pressure leaching equipment is used to improve the automation of the operation. At the same time, high-pressure equipment is eliminated, the risk of on-site safety operation is reduced, the operation process is simple, the decomposition cost is low, and the efficiency is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The present invention is a flow chart of the method. DETAILED DESCRIPTION

[0026] In order to explain the present invention more clearly, the present invention is further described in detail below in conjunction with embodiments and with reference to the accompanying drawings. It should be understood by those skilled in the art that the content described below is illustrative rather than restrictive, and should not be used to limit the scope of protection of the present invention.

[0027] Combination Figure 1 The present invention provides a method for continuously decomposing molybdenum roasted sand at low pressure, comprising:

[0028] 1. Pulping

[0029] In a stirring tank, molybdenum roasted sand is added to the aqueous solution at a ratio of 1:5, and a certain amount of liquid alkali and strong oxidant NaNO are added according to the amount required for complete reaction with molybdenum in theory. 3 , so that the slurry is mixed evenly.

[0030] 2. Continuous Leaching

[0031] The prepared slurry is poured at a flow rate of 20m 3 / h pumped into the continuous leaching reactor. During the continuous leaching reaction, steam was introduced to make the reaction temperature 110°C and maintain the pressure at 0.3Mpa. The stirring speed of each level was 110 rpm, so that the molybdenum was continuously leached in the form of sodium molybdate and remained in the solution.

[0032] 3. Continuous discharging

[0033] The design adopts a multi-stage continuous leaching method and ensures that the material is continuously discharged after the last stage of the liquid is fully qualified. In order to facilitate the subsequent solid-liquid separation, the continuous discharge process needs to be continuously cooled and the material temperature is kept below 50℃.

[0034] 4. Continuous Filtration

[0035] A conventional plate and frame filter press is used with an operating pressure of 20-25 MPa to separate the sodium molybdate solution from the slag phase, thereby obtaining a sodium molybdate solution that meets production requirements. Since the molybdenum slag contains multiple metals, other processes are used for recovery and application.

[0036] Example

[0037] In the multi-stage continuous leaching tank, the temperature of the slurry (mainly containing calcium molybdate, iron molybdate, and lead molybdate) before the reaction is guaranteed to be 120°C ± 5, and the alkalinity is 30g / L. Then, the prepared slurry (the slurry residue contains 15% molybdenum, the alkalinity is 60g / L, and the sodium nitrate content is 2g / L) is continuously and uniformly added to the first stage. The feeding speed is 20m 3 / h, the process is always heated by steam and the temperature is kept constant at 110℃, and the stirring speed of each level is 110 rpm. The slurry with good reaction flows into the discharge tank evenly. The discharge tank has a cooling jacket device to cool the material. When the cooling temperature is lower than 50℃, the filter press pump is started to pump the qualified slurry to the filter press for separation to obtain the required sodium molybdate solution and molybdenum slag. The molybdenum slag (molybdenum content <2%) is washed and dried with compressed air, unloaded and loaded into ton bags, and finally the solid-liquid separation is achieved.

[0038] Obviously, the above embodiments of the present invention are merely examples to more clearly illustrate the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made on the basis of the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A method for continuously decomposing molybdenum roasted sand at low pressure, comprising: 1) mixing molybdenum roasted sand with water, liquid caustic soda and strong oxidant uniformly to prepare slurry; 2) Continuously leaching the slurry obtained in step 1), introducing the required heat during the reaction and maintaining a certain pressure, so that molybdenum is continuously leached in the form of sodium molybdate and remains in the solution; adopting a multi-stage continuous leaching method and ensuring that the last stage of the slurry is fully qualified, and then continuously discharging the material; 3) Continuously filter under an operating pressure of 20-25 MPa to separate the sodium molybdate solution from the slag phase.

2. The method according to claim 1, characterized in that In step 1), molybdenum roasted sand is added to the aqueous solution at a ratio of 1:

5.

3. The method according to claim 1 or 2, characterized in that: In step 1), liquid alkali NaOH and strong oxidant NaNO3 are added in amounts theoretically required for complete reaction with molybdenum.

4. The method according to claim 1, characterized in that In step 2), the flow rate is 20m 3 / h and pumping the slurry obtained in step 1) into a continuous leaching reactor.

5. The method according to claim 1, characterized in that In step 2), steam is introduced to make the reaction temperature 110°C.

6. The method according to claim 1 or 5, characterized in that: In step 2), the pressure is maintained at 0.3 MPa.

7. The method according to claim 1, characterized in that In step 2), the stirring speed at each stage is 110 rpm.

8. The method according to claim 1, characterized in that In step 2), the continuous discharging process needs to be cooled continuously and the material temperature should be kept below 50°C.

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