Method for preparing and adding sodium aluminate solution refined filtration aid

Abstract

The invention belongs to the technical field of aluminum oxide production, and particularly relates to a preparation method of a sodium aluminate solution refined filtration aid, which adopts lime or lime milk, a sodium aluminate solution and ethanol or methanol as raw materials, the proportion is as follows: 1 part of lime or lime milk, 2-20 parts of sodium aluminate solution, 0.02-0.2 part of ethanol or 0.01-0.1 part of methanol, and the sodium aluminate solution comprises 100-300g / L of Na2O and 350-220g / L of Al2O3; under the conditions that the reaction temperature is 25-105 DEG C and the reaction time is 5-240 minutes, the sodium aluminate solution refined filtration aid is prepared. The method has the advantages that the use amount of the lime milk for filter aid can be greatly reduced, and aluminum oxide loss, steam consumption, water consumption and power consumption caused by large use amount of the lime milk are reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of alumina production, and relates to a preparation and adding method of a filter aid for fine filtration of a sodium aluminate solution. Background Art

[0002] The fine filtration of sodium aluminate solution is one of the main processes in the alumina industrial production process. Its function is to remove the suspended matter in the overflow of the red mud separation sedimentation tank (i.e., the crude sodium aluminate solution) by further filtration, so that the suspended matter content in the refined solution obtained after filtration is controlled below 15 mg / l (the suspended matter content before filtration: 150-300 mg / l), so as to ensure that the impurity content in the final product alumina is lower than the standard requirement value. In order to improve the filtration efficiency, filter aids need to be added during the filtration of the crude sodium aluminate solution. The filter aids can help quickly form a filter layer on the filter cloth surface, effectively prevent the passage of suspended matter, and slow down the growth rate of the liquid passing resistance. At present, the filter aids used in alumina plants are mainly lime milk, and 20 kg of lime needs to be added for every ton of alumina products.

[0003] Although the existing domestic filter aid addition process can meet the needs of filtration and the filtrate suspended solids can meet the index requirements, there are the following four main problems:

[0004] (1) The consumption of lime milk is large. During the filtration operation, lime milk is added to the crude sodium aluminate liquid as a filter aid. However, the filter aid only plays a major role in the filter cloth hanging cycle period. After entering the normal filtration of refined liquid period, the filter aid and suspended matter attached to the filter cloth in the early stage can meet the needs of blocking suspended matter from passing through the filter medium. Continuing to add lime milk will have limited filtering effect and increase unnecessary lime consumption.

[0005] (2) Cause alumina loss. Lime milk added to the process will react with alumina to cause alumina loss, which includes direct loss and indirect loss. Direct reaction loss refers to the lime that enters the alumina production process, which reacts with alumina to form hydrated garnet and is then discharged from the production system along with red mud. Therefore, the more lime milk is added, the more alumina is lost:

[0006] Al2O3+3Ca(OH)2+3H2O→3CaO·Al2O3·6H2O

[0007] The filter residue produced by the leaf filtration operation will promote the hydrolysis of the solution and cause the loss of alumina when it is returned to the previous red mud washing process to recover the attached losses.

[0008] (3) Increasing the amount of leaf filter residue results in an increase in the loss of alkali and alumina. The amount of lime milk added during leaf filtration increases, which increases the amount of filter residue. When the amount of lime milk added is 5‰ of the amount of crude sodium aluminate liquid and the suspended solids concentration of the crude sodium aluminate liquid is 0.5g / L, the solids formed by lime milk in the filter cake residue account for more than 60% of the total filter residue. The filter cake residue is returned to the previous red mud washing process, which increases the amount of red mud and thus increases the loss of abandoned red mud.

[0009] (4) Increased evaporation water and electricity consumption. Domestic alumina plants mostly use the process of hydrating lime to prepare lime milk. The more lime milk is used, the more water will enter the system with the lime milk, the higher the load of the evaporation process, and the higher the steam and electricity consumption of evaporation. The large amount of lime milk used will increase the water and electricity consumption for the preparation and transportation of lime milk. Summary of the invention

[0010] Purpose of the Invention

[0011] Aiming at the problems of large lime consumption in fine filtration of sodium aluminate solution and high alumina loss in existing alumina production, a method for preparing and adding a filter aid for fine filtration of sodium aluminate solution is provided, which can reduce the lime consumption for fine filtration and reduce the alumina loss in fine filtration.

[0012] To achieve the above object, the present invention provides the following technical solutions:

[0013] A method for preparing a sodium aluminate solution fine filtration filter aid comprises lime or lime milk, sodium aluminate solution and ethanol or methanol as raw materials, wherein the proportions are: 1 part of lime or lime milk, 2-20 parts of sodium aluminate solution, 0.02-0.2 parts of ethanol or 0.01-0.1 parts of methanol, wherein the concentration of the sodium aluminate solution is 100-300 g / L of Na2O and 50-220 g / L of Al2O3; and the sodium aluminate solution fine filtration filter aid is prepared under the conditions of a reaction temperature of 25-105°C and a reaction time of 5-240 minutes.

[0014] As a further description of the above scheme, the concentration of the lime milk is CaO 50-300g / L.

[0015] As a further description of the above scheme, the sodium aluminate solution in the raw material is one of a crude sodium aluminate liquid, a refined liquid and a mother liquor, and the crude sodium aluminate liquid is 2-10 parts, the refined liquid is 2-10 parts or the mother liquor is 4-20 parts.

[0016] As a further description of the above scheme, the concentration of ethanol or methanol is 10-99%.

[0017] A method for adding a filter aid for fine filtration of a sodium aluminate solution comprises the following steps:

[0018] Step 1, mixing the sodium aluminate solution fine filtration filter aid according to claim 1 with the sodium aluminate crude liquid at a mass ratio of 0.001-0.02:1 and entering the leaf filter for fine filtration, and stopping adding the filter aid after 2-30 minutes;

[0019] Step 2: After continuing to add the crude sodium aluminate solution for 10-120 minutes, stop adding the crude sodium aluminate solution;

[0020] Step 3: Unloading the filter cake from the leaf filter;

[0021] Step 4: After unloading the filter cake, repeat step 1 to start a new cycle.

[0022] Advantages and effects of the present invention:

[0023] The present invention aims at solving the problems that the lime consumption in the fine filtration of sodium aluminate solution in the existing alumina production is large, resulting in high alumina loss, etc. The use of this patented technology can greatly reduce the amount of lime milk used as a filtration aid, and reduce the alumina loss, steam consumption, water consumption and electricity consumption caused by the large amount of lime milk. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a scanning electron microscope photo 1 of the filter aid prepared by the present invention;

[0025] Figure 2 Scanning electron microscope photo 2 of the filter aid prepared by the present invention. DETAILED DESCRIPTION

[0026] It can be understood that the specific description of the present invention is only used to illustrate the present invention and is not limited to the technical solutions described in the embodiments of the present invention. It is impossible to list all the implementation methods here. Ordinary technicians in this field should understand that the present invention can still be modified or replaced by equivalents to achieve the same technical effects; as long as the use requirements are met, they are within the protection scope of the present invention.

[0027] A method for preparing a sodium aluminate solution fine filtration filter aid comprises lime or lime milk, sodium aluminate solution and ethanol or methanol as raw materials, wherein the proportions are: 1 part of lime or lime milk, 2-20 parts of sodium aluminate solution, 0.02-0.2 parts of ethanol or 0.01-0.1 parts of methanol, wherein the concentration of the sodium aluminate solution is 100-300 g / L of Na2O and 50-220 g / L of Al2O3; and the sodium aluminate solution fine filtration filter aid is prepared under the conditions of a reaction temperature of 25-105°C and a reaction time of 5-240 minutes. The filter aid prepared by this method has a mesh and bridge structure, which can better filter fine particles; at the same time, in view of the large consumption of lime for fine filtration of sodium aluminate solution in the existing alumina production, resulting in high alumina loss, etc., the implementation of this patented technology can reduce the consumption of lime for fine filtration by 60-90%, reduce the loss of fine filtration alumina by 60-90%, and also reduce steam consumption, water consumption and electricity consumption; at the same time, the design of the concentration of sodium aluminate solution combines the on-site process and production conditions, and is suitable for all alumina plants.

[0028] The concentration of the lime milk of the present invention is CaO 50-300g / L.

[0029] The sodium aluminate solution in the raw material of the present invention is one of a crude sodium aluminate solution, a refined solution, a seed solution or a circulating solution, wherein the crude sodium aluminate solution is 2-10 parts, the refined solution is 2-10 parts or the solution is 4-20 parts. This design can select the best solution according to the on-site process and configuration, and the raw material trial range is wide.

[0030] The concentration of ethanol or methanol in the present invention is 10-99%. The addition of ethanol or methanol in the present invention can provide hydroxyl groups to form a bridge structure.

[0031] The method for preparing and adding a filter aid for fine filtration of a sodium aluminate solution of the present invention comprises the following steps:

[0032] Step 1: Mix the above with the crude sodium aluminate liquid at a ratio of 0.001-0.02:1 and enter the leaf filter for fine filtration. Stop adding the filter aid after 2-30 minutes;

[0033] Step 2: After continuing to add the crude sodium aluminate solution for 10-120 minutes, stop adding the crude sodium aluminate solution;

[0034] Step 3: Unloading the filter cake from the leaf filter;

[0035] Step 4: After the filter cake is unloaded, step 1 is repeated to start a new cycle. The preparation and addition method of the sodium aluminate solution fine filtration filter aid of the present invention can achieve good filtration aid effect and reduce the amount of filter aid used.

[0036] Example 1

[0037] In the present embodiment, the preparation and addition method of the filter aid for fine filtration of sodium aluminate solution adopts lime or lime milk, sodium aluminate solution and methanol as raw materials, and the ratio is 1 part of lime milk, 2 parts of crude sodium aluminate liquid, and 0.01 part of methanol; under the conditions of reaction temperature of 25° C. and reaction time of 240 minutes, the filter aid for fine filtration of sodium aluminate solution is prepared.

[0038] The method for preparing and adding the filter aid for fine filtration of the sodium aluminate solution comprises the following steps:

[0039] Step 1: The filter aid and the crude sodium aluminate solution are mixed in a ratio of 0.001:1 and then filtered through a leaf filter for fine filtration. After 2 minutes, the addition of the filter aid is stopped.

[0040] Step 2: After adding the crude sodium aluminate solution for 10 minutes, stop adding the crude sodium aluminate solution;

[0041] Step 3: Unloading the filter cake from the leaf filter;

[0042] Step 4: After the filter cake is unloaded, repeat step 1 to start a new cycle.

[0043] The concentration of lime milk in this embodiment is CaO 50g / L.

[0044] The methanol concentration in this example is 99%.

[0045] The concentrations of the crude sodium aluminate solution in this embodiment are Na2O 300 g / L and Al2O3 220 g / L.

[0046] The sodium aluminate solution fine filtration filter aid obtained in the example was put into the alumina production of the prior art, and the amount of lime added per ton of alumina product was 7 kg, corresponding to an alumina loss of 4.1 kg.

[0047] Example 2

[0048] In the present embodiment, the preparation and addition method of the filter aid for fine filtration of sodium aluminate solution adopts lime or lime milk, sodium aluminate solution and methanol as raw materials, and the ratio is 1 part of lime milk, 10 parts of crude sodium aluminate liquid and 0.1 part of methanol; under the conditions of reaction temperature of 105° C. and reaction time of 5 minutes, the filter aid for fine filtration of sodium aluminate solution is prepared.

[0049] The method for preparing and adding the filter aid for fine filtration of the sodium aluminate solution comprises the following steps:

[0050] Step 1: The filter aid and the crude sodium aluminate solution are mixed in a ratio of 0.02:1 and then filtered through a leaf filter for fine filtration. After 30 minutes, the addition of the filter aid is stopped.

[0051] Step 2: After the crude sodium aluminate solution is added for 120 minutes, the addition of the crude sodium aluminate solution is stopped;

[0052] Step 3: Unloading the filter cake from the leaf filter;

[0053] Step 4: After the filter cake is unloaded, repeat step 1 to start a new cycle.

[0054] The concentration of lime milk in this embodiment is 300g / L;

[0055] The methanol concentration in this embodiment is 10%;

[0056] The concentrations of the crude sodium aluminate solution in this example are Na2O 100 g / L and Al2O3 50 g / L.

[0057] The sodium aluminate solution fine filtration filter aid obtained in the example was put into the alumina production of the prior art, and the amount of lime added per ton of alumina product was 2 kg, corresponding to an alumina loss of 1.7 kg.

[0058] Comparative Example 1

[0059] In the prior art alumina production, the amount of lime added as a filter aid is 20 kg of lime per ton of alumina product, resulting in a loss of 12.6 kg of alumina.

[0060] Comparing Example 1 and Example 2 with Comparative Example 1 which does not adopt the technology of the present invention, the lime consumption is reduced by 70% and 90% respectively, and the alumina loss is reduced by 70% and 90% respectively.

[0061] Depend on Figure 1 and Figure 2 It can be seen that the filter aid prepared by the present invention has a particle size of 0.5-1 micron, a complete degree of crystallization, and a tetrahedral microscopic morphology. This morphology has a large specific surface area and can form a bridge structure when the particles are aggregated.

[0062] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing a filter aid for fine filtration of sodium aluminate solution, characterized in that: Lime or lime milk, sodium aluminate solution and ethanol or methanol are used as raw materials, and the proportion is: 1 part of lime or lime milk, 2-20 parts of sodium aluminate solution, 0.02-0.2 parts of ethanol or 0.01-0.1 parts of methanol, and the concentration of the sodium aluminate solution is 100-300 g / L of Na2O and 50-220 g / L of Al2O3; under the conditions of reaction temperature of 25-105°C and reaction time of 5-240 minutes, a sodium aluminate solution fine filtration filter aid is prepared.

2. The method for preparing a filter aid for fine filtration of sodium aluminate solution according to claim 1, characterized in that: The concentration of the lime milk is CaO 50-300g / L.

3. The method for preparing a filter aid for fine filtration of sodium aluminate solution according to claim 1, characterized in that: The sodium aluminate solution in the raw material is one of a crude sodium aluminate liquid, a refined liquid and a mother liquor, and the crude sodium aluminate liquid is 2-10 parts, the refined liquid is 2-10 parts or the mother liquor is 4-20 parts.

4. The method for preparing a filter aid for fine filtration of sodium aluminate solution according to claim 1, characterized in that: The concentration of the ethanol or methanol is 10-99%.

5. A method for adding a filter aid for fine filtration of a sodium aluminate solution, characterized in that: The following steps are involved: Step 1, mixing the sodium aluminate solution fine filtration filter aid according to claim 1 with the sodium aluminate crude liquid at a mass ratio of 0.001-0.02:1 and entering the leaf filter for fine filtration, and stopping adding the filter aid after 2-30 minutes; Step 2: After continuing to add the crude sodium aluminate solution for 10-120 minutes, stop adding the crude sodium aluminate solution; Step 3: Unloading the filter cake from the leaf filter; Step 4: After the filter cake is unloaded, repeat step 1 to start a new cycle.

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