Water saving method in preparation process of iron oxide red

Abstract

The invention discloses a water-saving method in the preparation process of iron oxide red, which is characterized in that a filter cake formed after filter pressing is washed in the filter pressing and washing process of iron oxide red slurry, and the washing comprises the following steps: carrying out primary washing on the iron oxide red filter cake by using secondary washing water, and forming primary washing water by using water after washing the filter cake; washing the iron oxide red filter cake for the second time by using the third-time washing water, and forming second-time washing water by using water after washing the filter cake; washing the iron oxide red filter cake for the third time by using clear water, wherein the water after washing the filter cake forms third washing water; the total amount of clean water used for washing each batch of iron oxide red filter cakes is # imgabs0, when the conductivity of washing water at one time exceeds a rated value, the clean water is used for slurrying the calcined iron oxide red, washing water at each stage is fully utilized, and the amount of clean water is saved to the maximum extent.

Description

Technical Field

[0001] The invention relates to a method for preparing red iron oxide, in particular to a method for saving washing water in the process of washing red iron oxide filter cake. Background Art

[0002] Red iron oxide, also known as iron oxide red or iron red, is a dark red or red powder. It is the world's largest inorganic dye pigment with a chemical formula of α-Fe 2 O 3 , melting point is 1565℃, non-toxic, insoluble in water. It is the inorganic pigment with the largest output and usage except titanium dioxide, and it is also the product with the largest usage and output in the iron oxide series pigments (iron red, iron yellow, iron black, etc.). It has good light resistance, weather resistance, hiding power, high wear resistance and corrosion resistance, and is widely used in building materials, coatings, plastics, rubber, ceramics, glass, inks, lithium batteries and other industries. At present, the traditional preparation methods of iron oxide red include dry process and wet process. The dry process includes green vitriol calcination method, iron yellow calcination method, iron black calcination method, ferrous sulfate-soda ash calcination method, and the wet process includes sulfate method, nitrate method, and mixed acid salt method.

[0003] In the process of wet production of red iron oxide, the calcined red iron oxide is sent to a slurry pool to form a primary slurry, and then the primary slurry is ground, dissolved, color-matched, filtered, and cleaned to obtain a red iron oxide filter cake, and then the red iron oxide filter cake is dried and crushed to obtain the red iron oxide finished product.

[0004] After the primary slurry is filtered, the mother liquor after filtration is discharged from the filter press. There are certain water-soluble substances in the mother liquor, and there are also water-soluble substances in the filter cake formed after filtration. These water-soluble substances have a great influence on the quality of the red iron oxide product. Therefore, it is necessary to wash the filter cake to dissolve the water-soluble substances in the filter cake as much as possible, so that the content of water-soluble substances in the filter cake is greatly reduced to meet the standard requirements of the red iron oxide product. According to "GB / T 1863-2008 Iron Oxide Pigments", the purity of the red iron oxide product is expressed by the content of ferric oxide. The specific requirements are: Class A is not less than 95%, Class B is not less than 70%, Class C is not less than 40%, and Class D is not less than 10%. For the content of water-soluble substances, the standard for higher-quality Type I red and brown products stipulates that the mass fraction of water-soluble substances (measured after drying at 105°C) is ≤0.3%, and the total mass fraction of water-soluble oxides and sulfates (measured as Cl - and SO 4 -2 Indicates) ≤0.1%.

[0005] There are many documents on the washing of red iron oxide filter cake. The Chinese patent "A method for washing and separating high-purity red iron oxide": Publication number CN104445434B, discloses a method for washing and separating high-purity red iron oxide. The red iron oxide is first mixed with water and ground, and then an iron-containing electrolyte solution is added to the washed red iron oxide slurry and stirred. After the slurry is allowed to stand, the lower layer of precipitated red iron oxide material and the upper layer of water washing liquid are separated, and the filter cake after the lower layer of precipitated red iron oxide material is filtered and dried. The upper layer of water washing liquid is separated from the filtrate and solid red iron oxide material by filtering equipment and the filtrate is discharged. At the same time, the liquid and solid red iron oxide material separated by the filter press are recovered and repeatedly processed, which can reduce the loss rate of red iron oxide to less than 1% and solve the problem of wastewater discharge in environmental protection.

[0006] "A method for manufacturing a red iron oxide water washing device", publication number CN202322365650.1, the utility model provides a red iron oxide water washing device, red iron oxide solution and chloride ion remover are added into a stirring tank through a dosing pipe for stirring, and then an electric motor and an electromagnetic rod are used to adsorb and remove impurities from the red iron oxide, and then the electromagnetic rod after adsorbing impurities is transferred to a sewage washing tank for cleaning, thereby realizing water washing of the red iron oxide and separation of impurities.

[0007] "A filter cake washing system", application number CN202320128275.8, this utility model relates to a filter cake washing system, including a filtration system, an atomization system, and a positive pressure system. The atomization system can transfer the washing liquid into the filtration system in atomized form, and the positive pressure system can force the atomized washing liquid into the filter cake, thereby achieving uniform washing of the filter cake. The system can be installed in a detachable manner and can provide all-round spraying and washing.

[0008] In Chinese patent CN116216680B "A method for preparing lithium iron phosphate positive electrode material using industrial waste iron mud", in paragraphs

[0049] and

[0050] of its specification, S4, filtering and washing process is disclosed: the above-mentioned iron precipitate slurry is filtered, and the filter cake is washed with pure water. The washing end point is that the conductivity of the rinsing water is ≤300μs / cm (the actual measurement is 285μs / cm). Obviously, in order to ensure the washing effect, pure water is used. However, such a low conductivity of the rinsing water is suspicious, because the conductivity of ordinary tap water is also higher than 1000μs / cm.

[0009] Some comprehensive utilization technologies have also been reported for the wastewater generated during the washing process of the red iron oxide filter cake. For example, the article "Research on the Treatment and Resource Utilization of Wastewater from the Red Iron Oxide Factory" by Ge Qilong focused on the optimal process parameters for the treatment of acidic wastewater from the red iron oxide factory, demonstrated the feasibility of using the wastewater from the red iron oxide factory to produce red iron oxide pigment, and determined the optimal reaction conditions. The experimental results show that after adding NaOH solution and other treatments to the wastewater from the red iron oxide factory, the precipitated iron-containing sludge can be used as red iron oxide crystal seeds for the production of red iron oxide pigment, achieving a certain degree of resource utilization of wastewater.

[0010] "Treatment and Utilization of Wastewater from Iron Oxide Production", author Wang Handong, mentioned in the article that the solid matter, ammonia nitrogen, sulfate ions, etc. in the washing wastewater can be separated and recovered, and the treated clean water can be recycled in the iron oxide production process without affecting the quality of the iron oxide product. The remaining washing wastewater is recovered through fine filtration, drying, and roasting to recover iron oxide. After a series of treatments such as neutralization and precipitation of the filtrate with lime milk, and removal of sulfate ions, ammonia water with a mass fraction of about 15% can be obtained, which can be sold as a product or used in iron oxide production.

[0011] In summary, the prior art discusses washing the red iron oxide filter cake with pure water or clean water, which leads to the problem of large amounts of pure water and clean water used, and the comprehensive utilization of the red iron oxide filter cake washing water is not reused in the washing of the red iron oxide filter cake. Summary of the invention

[0012] Obviously, the amount of clean water used for washing the red iron oxide filter cake is a core issue directly related to the production cost. There has been no corresponding research on how to use as little clean water as possible while ensuring the washing effect of the red iron oxide filter cake. Therefore, the purpose of the present invention is to provide a method that can effectively utilize the washing water of the red iron oxide filter cake to effectively remove water-soluble substances and use as little clean water as possible.

[0013] The technical solution adopted by the present invention to solve its technical problem is:

[0014] The inventor found that the relationship between conductivity and water-soluble content is not a fixed value, and it is affected by various factors such as salt type and temperature. For the washing solution of the iron oxide red filter cake, at the same temperature, there is a corresponding relationship between conductivity and water-soluble content. Conductivity is an indicator to measure the electrolyte content in water. The more impurity ions dissolved in water, the higher the conductivity. In the washing process of iron oxide red, as the number of washings increases, the impurity content in the washing water will gradually decrease, and the conductivity will also decrease accordingly. Therefore, the working condition and washing effect of the washing water can be judged by monitoring the conductivity changes of the first washing water, the second washing water and the third washing water. The present invention designs three washings of the iron oxide red filter cake, and establishes a model of the optimal amount of clean water through the conductivity difference between different washing waters, so as to save the amount of clean water to the maximum extent.

[0015] A water-saving method in the preparation process of red iron oxide is to wash the filter cake formed after the filtration during the filtration and washing of the red iron oxide slurry, wherein the washing comprises:

[0016] The red iron oxide filter cake is washed for the first time with the secondary washing water, and the water after washing the filter cake forms the primary washing water;

[0017] The red iron oxide filter cake is washed a second time with the tertiary washing water, and the water after washing the filter cake forms the secondary washing water;

[0018] The red iron oxide filter cake is washed for the third time with clean water, and the water after washing the filter cake forms the third washing water;

[0019] The total amount of clean water used for washing each batch of iron oxide red filter cake is:

[0020]

[0021] Where, M is the total amount of water-soluble matter in the initial iron oxide red filter cake, M std The total amount of water-soluble matter allowed to remain in the red iron oxide filter cake after washing;

[0022] The conductivity of the secondary wash water is C 2 , the secondary washing water dosage is V 2 ;

[0023] The conductivity of the three wash water is C 3 , the amount of water used for three washes is V 3 ;

[0024] The amount of clean water is V 0 , the conductivity of clean water is C 0 ;

[0025] This formula is derived based on the principle of water-soluble matter migration and conservation of matter. It is used to calculate the amount of different wash water to achieve the purpose of saving water and meeting the water-soluble matter requirements of the product. The derivation process is as follows:

[0026] 1. First wash (using secondary wash water)

[0027] According to the law of conservation of matter, the reduction in water-soluble matter in the filter cake during the first washing is equal to the increase in water-soluble matter in the second washing water. It can be obtained that: MM 1 =k 1 C 2 V 2 , where M 1 It is the water-soluble matter content in the filter cake after the first washing.

[0028] 2. Second wash (using three wash water)

[0029] Similarly, during the second wash, M 1 -M 2 =k 2 C 3 V 3 , where M 2 It is the water-soluble matter content in the filter cake after the second washing.

[0030] 3. Third wash (using clean water)

[0031] During the third wash, M 2 -M std =k 3 C 0 V 0

[0032] From the final washing requirements, we know that when the conductivity of the three wash water reaches the rated conductivity C rated When the washing is completed, that is, C 3 =C rated

[0033] Combining the above three equations, we can get:

[0034]

[0035] k 1 is the migration coefficient of water-soluble matter during the first washing, k 2 is the migration coefficient of water-soluble matter during the second washing, k 3 is the water-soluble matter migration coefficient during the third washing. In simple terms, it indicates the proportion of water-soluble matter that can migrate from the filter cake during the washing process under the conditions of unit conductivity and unit volume of washing water. For example, it indicates the water-soluble matter migration coefficient k during the first washing. 1, which reflects the migration of water-soluble matter in the filter cake under the action of the secondary washing water during the first washing of the filter cake with the secondary washing water. Similarly, the migration coefficient k of water-soluble matter during the second washing 2 , which reflects the migration of water-soluble matter in the filter cake under the action of three wash waters during the second wash of the filter cake with three wash waters; similarly, it represents the migration coefficient k of water-soluble matter during the third wash. 3 It reflects the migration of water-soluble matter in the filter cake under the action of clean water during the third washing of the filter cake with clean water.

[0036] From the derivation process of the formula, the unit of the water-soluble migration coefficient is From the perspective of mass transfer, the washing process is a process of mass transfer between phases, that is, between the filter cake and the wash water (or clean water). When the wash water (or clean water) comes into contact with the filter cake, the water-soluble matter is transferred from the filter cake phase and the mother liquor remaining in the filter cake to the wash water (or clean water) phase. The rate of this process is affected by factors such as the interfacial area, concentration difference, and mass transfer coefficient. The water-soluble matter migration coefficient can be understood as a coefficient that combines these mass transfer factors. It reflects the efficiency of the water-soluble matter transferred from the filter cake to the washing liquid under specific washing conditions, such as the properties of the wash water (or clean water), the state of the filter cake, etc. Through many experiments and explorations, the inventor obtained the water-soluble matter migration coefficient k during the first washing. 1 for Migration coefficient k of water-soluble matter during the second washing 2 for The migration coefficient k of water-soluble matter during the third washing 3 for

[0037] In order to more accurately adjust the dosage of the secondary washing water, the tertiary washing water and the clean water, and to meet the final washing effect, that is, to achieve the minimum water-soluble matter content in the filter cake after washing, it is necessary to consider the difference in conductivity between the primary washing water and the secondary washing water, and the difference in conductivity between the secondary washing water and the tertiary washing water. Only when these two differences meet certain conditions can the tertiary washing water be used to wash the filter cake for the second time, or the secondary washing water can be used to wash the filter cake for the first time. If the two conductivity differences do not meet the corresponding requirements, clean water is added to the tertiary washing water or the secondary washing water to adjust its conductivity, so that the conductivity difference meets the corresponding requirements, and the purpose of fully using the tertiary washing water and the secondary washing water is achieved. In addition, the dosage of the tertiary washing water and the secondary washing water should be fully considered, so that the clean water used to wash the filter cake for the third time and the total amount of clean water added to the secondary washing water and the tertiary washing water are minimized.

[0038] Then, after adding clean water to the secondary wash water and / or tertiary wash water, the total amount of clean water used is:

[0039] Vtotal =V add2 +V add3 +V 0

[0040] It should also meet:

[0041]

[0042] Where V total is the total amount of clean water used, V add2 V is the amount of clean water added to the secondary wash water. add3 To replenish the amount of clean water in three washes, is the minimum permissible conductivity difference between the primary wash water and the secondary wash water, It is the minimum allowable conductivity difference between the secondary wash water and the tertiary wash water.

[0043] The derivation process of this formula is as follows:

[0044] 4. Define conductivity difference

[0045] Assume that the difference in conductivity between the first wash water and the second wash water is: ΔC 1-2 =C 1 -C 2

[0046] Assume that the difference in conductivity between the second wash water and the third wash water is ΔC 2-3 =C 2 -C 3

[0047] 5. Set the difference requirement

[0048] Assume that there is a minimum allowable difference in conductivity between the primary and secondary wash water. And a minimum permissible conductivity difference between the secondary wash water and the tertiary wash water

[0049] when and Only then can the filter cake be washed according to the previous process, that is, the filter cake is washed for the first time with the secondary washing water and the filter cake is washed for the second time with the tertiary washing water.

[0050] 6. Consider adding clean water to adjust the conductivity

[0051] like Assume that the volume of clean water to be added to the secondary wash water is V add2 , then:

[0052]

[0053] The final solution is:

[0054]

[0055] Similarly, if Assume that the volume of clean water to be added to the secondary wash water is V add3 , then:

[0056]

[0057] The final solution is:

[0058]

[0059] The total amount of clean water used, including the water used for the second and third washes and the clean water used for the third wash, is V total =V add2 +V add3 +V 0 , so that V total Minimum, need to consider V add2 、V add3 and V 0 The relationship between them is optimized and adjusted according to the actual conductivity and migration of water-soluble substances.

[0060] Wherein, the conductivity of the clean water is C 0 is 1250μs / cm, and the conductivity C of the three washing water is 3 ≤9800μs / cm, 9800μs / cm is also the rated conductivity of the three-wash water. Less than or equal to this rated conductivity indicates that the iron oxide red filter cake meets the quality requirements after washing; the conductivity of the secondary wash water C 2 ≤16000μs / cm. If the conductivity is less than or equal to this value, the red iron oxide filter cake can be washed for the first time using secondary washing water.

[0061] The minimum permissible conductivity difference between the primary wash water and the secondary wash water is The minimum permissible conductivity difference between the secondary wash water and the tertiary wash water is

[0062] When the conductivity of the primary washing water exceeds 32000 μs / cm, the primary washing water is introduced into a pulping tank to pulp the calcined red iron oxide.

[0063] The primary washing water, secondary washing water and tertiary washing water are stored in the primary washing water tank, the secondary washing water tank and the tertiary washing water tank respectively, and the clean water is stored in the clean water tank; in the initial stage of washing the red iron oxide filter cake, that is, when there is no primary washing water in the primary washing water tank, the red iron oxide filter cake is washed for the first time with clean water to form primary washing water and stored in the primary washing water tank; in the initial stage of washing the red iron oxide filter cake, that is, when there is no secondary washing water in the secondary washing water tank, the red iron oxide filter cake is washed for the second time with clean water to form secondary washing water and stored in the secondary washing water tank; in the initial stage of washing the red iron oxide filter cake, that is, when there is no tertiary washing water in the tertiary washing water tank, the red iron oxide filter cake is washed for the third time with clean water to form tertiary washing water and stored in the tertiary washing water tank.

[0064] When the conductivity of the secondary wash water in the secondary wash water tank exceeds the rated value of 16000 μs / cm, clean water is passed from the clean water tank into the secondary wash water tank until the conductivity is lower than the rated value of 16000 μs / cm.

[0065] When the conductivity of the tertiary wash water in the tertiary wash water tank exceeds the rated value of 9800 μs / cm, clean water is passed from the clean water tank into the tertiary wash water tank until the conductivity is lower than the rated value of 9800 μs / cm.

[0066] The device for implementing the water-saving method in the preparation process of red iron oxide comprises a filter press, a slurry tank, a mother liquor water tank, a clean water tank, a primary wash water tank, a secondary wash water tank and a tertiary wash water tank, wherein the outlet of the slurry tank is connected to the inlet of the filter press through an inlet main pipe provided with a slurry pump and a control valve, the outlet of the filter press is connected to the outlet main pipe, the outlets of the clean water tank, the primary wash water tank and the secondary wash water tank are respectively connected to the wash water inlet main pipe through pipelines provided with control valves and wash water pumps, the outlet of the tertiary wash water tank is connected to the inlet of the slurry tank through a return pipe provided with a return pump, the wash water inlet main pipe is connected to the inlet main pipe of the filter press, the outlet main pipe is connected to the wash water outlet main pipe, and the wash water outlet main pipe is respectively connected to the inlets of the primary wash water tank, the secondary wash water tank, the tertiary wash water tank and the mother liquor water tank through pipelines provided with independent control valves.

[0067] The beneficial effects of the present invention are:

[0068] Firstly, the present invention scientifically arranges three washings of the red iron oxide filter cake and fully utilizes the washing water of each washing of the red iron oxide filter cake, that is, the red iron oxide filter cake is washed for the first time with the secondary washing water, and the water after washing the filter cake forms the primary washing water; the red iron oxide filter cake is washed for the second time with the tertiary washing water, and the water after washing the filter cake forms the secondary washing water; the red iron oxide filter cake is washed for the third time with clean water, and the water after washing the filter cake forms the tertiary washing water; and the primary washing water is reused in the pulping tank to pulp the calcined red iron oxide.

[0069] Secondly, by controlling the total amount of water-soluble matter in the initial red iron oxide filter cake, the residual amount of water-soluble matter in the red iron oxide filter cake after washing, the conductivity of each washing water, the conductivity difference between the first washing water and the second washing water, the conductivity difference between the second washing water and the third washing water, and setting the migration coefficient of water-soluble matter in each washing, a mathematical model for maximally reducing the total amount of clean water is established, so that the present invention can save the total amount of clean water to the maximum extent while effectively removing the water-soluble matter in the red iron oxide filter cake. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 It is a diagram of a filter press device for implementing the method of the present invention.

[0071] 1-slurry tank, 2-filter press, 3-mother liquor water tank, 4-clean water tank, 5-primary wash water tank, 6-secondary wash water tank, 7-tertiary wash water tank, 8-inlet main pipe, 9-outlet main pipe, 10-return pipe, 11-wash water inlet main pipe, 12-slurry pump, 13-wash water outlet main pipe, 14-wash water pump, 15-return pump, 20-feed control valve, 21-first control valve, 22-second control valve, 23-third control valve, 24-fourth control valve, 25-fifth control valve, 26-sixth control valve, 27-seventh control valve. DETAILED DESCRIPTION

[0072] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0073] A filter press device for implementing the water-saving method described in the present invention comprises a slurry tank 1, a filter press 2, a mother liquid water tank 3, a clean water tank 4, a primary wash water tank 5, a secondary wash water tank 6 and a tertiary wash water tank 7, the filter press 2 is provided with an inlet manifold 8, an outlet manifold 9, a wash water inlet manifold 11 and a wash water outlet manifold 13, the outlet of the slurry tank 1 is connected to the inlet of the filter press 2 via the inlet manifold 8 provided with a slurry pump 12 and a feed control valve 20, the outlet of the filter press 2 is connected to the outlet manifold 9, the wash water inlet manifold 11 is connected to the inlet manifold 8 of the filter press 1, the outlet manifold 9 is connected to the wash water outlet manifold 13, the wash water outlet manifold 13 is connected to the inlet of the mother liquid water tank 3 via a pipeline provided with a first control valve 21, and the outlet of the clean water tank 4 is connected to the inlet of the mother liquid water tank 3 via a pipeline provided with a second control valve 21. The pipes through which the control valve 22 and the wash water pump 14 are connected to the wash water inlet main pipe 11, the outlet of the tertiary wash water tank 7 is connected to the wash water inlet main pipe 11 via a pipe provided with a third control valve 23 and another wash water pump 14, the outlet of the secondary wash water tank 6 is connected to the wash water inlet main pipe 11 via a pipe provided with a fourth control valve 24 and another wash water pump 14, the wash water outlet main pipe 13 is connected to the inlet of the primary wash water tank 5 via a pipe provided with a fifth control valve 25, the wash water outlet main pipe 13 is connected to the inlet of the secondary wash water tank 6 via a pipe provided with a sixth control valve 26, the wash water outlet main pipe 13 is connected to the inlet of the tertiary wash water tank 7 via a pipe provided with a seventh control valve 27, and the outlet of the primary wash water tank 5 is connected to the inlet of the slurry tank 2 via a return pipe 10 provided with a return pump 15.

[0074] In the initial stage of washing the red iron oxide filter cake, that is, when there is no primary washing water in the primary washing water tank 5, the red iron oxide filter cake is washed for the first time with clean water to form primary washing water and stored in the primary washing water tank 5; in the initial stage of washing the red iron oxide filter cake, that is, when there is no secondary washing water in the secondary washing water tank 6, the red iron oxide filter cake is washed for the second time with clean water to form secondary washing water and stored in the secondary washing water tank 6; in the initial stage of washing the red iron oxide filter cake, that is, when there is no tertiary washing water in the tertiary washing water tank 7, the red iron oxide filter cake is washed for the third time with clean water to form tertiary washing water and stored in the tertiary washing water tank 7. After the initial stage, when washing the red iron oxide filter cake again, the red iron oxide filter cake is washed for the first time with the secondary washing water, and the water after washing the filter cake forms the primary washing water; the red iron oxide filter cake is washed for the second time with the tertiary washing water, and the water after washing the filter cake forms the secondary washing water; the red iron oxide filter cake is washed for the third time with clean water, and the water after washing the filter cake forms the tertiary washing water;

[0075] The total amount of clean water used for washing each batch of iron oxide red filter cake is:

[0076]

[0077] Where, M is the total amount of water-soluble matter in the initial iron oxide red filter cake, M stdThe total amount of water-soluble matter allowed to remain in the red iron oxide filter cake after washing;

[0078] The conductivity of the secondary wash water is C 2 , the secondary washing water dosage is V 2 ;

[0079] The conductivity of the three wash water is C 3 , the amount of water used for three washes is V 3 ;

[0080] The amount of clean water is V 0 , the conductivity of clean water is C 0 ;

[0081] Based on the above content, three embodiments and one comparative example are designed. It is assumed that the red iron oxide slurry that needs to be filtered and washed in each embodiment and comparative example is 1m 3 After filtering the slurry and discharging the mother liquor, the red iron oxide filter cake contained 269 kg of solution and 500 kg of red iron oxide, of which the total amount of water-soluble matter in the 269 kg of solution was 7.42 kg, the conductivity of the clean water was 1250 μs / cm, and the highest conductivity of the three washing waters after the third washing, that is, the rated conductivity of the three washing waters was 9800 μs / cm.

[0082] Example 1: Conventional three-stage washing

[0083] A water-saving method in the preparation process of red iron oxide is to wash the filter cake formed after the filtration during the filtration and washing of the red iron oxide slurry, wherein the washing comprises:

[0084] The secondary wash water in the secondary wash water tank 6 is passed into the filter press 2 to wash the red iron oxide filter cake for the first time. When the wash water enters the filter cake, it will begin to penetrate into the pores of the filter cake driven by the pressure difference. Since the filter cake has a certain pore structure, the wash water will flow along the pores and diffusion will occur at the same time. At the microscopic level, the wash water will come into contact with the mother liquor in the pores of the filter cake and the impurities on the solid surface. For the soluble matter in the filter cake, due to the existence of the concentration difference, the soluble matter will diffuse from the high concentration area (the mother liquor part in the filter cake) to the low concentration area (wash water). This is a spontaneous process based on physical and chemical principles and conforms to the law of diffusion. In this process, the wash water will gradually replace the mother liquor in the pores of the filter cake, while dissolving and taking away the soluble impurities therein. For the iron oxide red filter cake, impurities may include some water-soluble substances such as salts, acids, and alkalis remaining in the production process. These substances will dissolve in the wash water and gradually be taken out of the filter cake as the wash water flows, and then the water will be discharged through the outlet main pipe 9 to form primary wash water, which will be stored in the primary wash water tank 5;

[0085] Similarly, the iron oxide red filter cake is washed for the second time with the tertiary washing water in the tertiary washing water tank 7, and the water after washing the filter cake forms the secondary washing water, which is stored in the secondary washing water tank 6;

[0086] Similarly, the red iron oxide filter cake is washed for the third time with the clean water in the clean water tank 4 , and the water after washing the filter cake forms the tertiary washing water, which is stored in the tertiary washing water tank 7 .

[0087] In this embodiment, the total amount of water-soluble matter in the initial iron oxide red filter cake is M=7.42 kg, and the total amount of water-soluble matter allowed to remain in the iron oxide red filter cake after washing is M std =0.68kg, the conductivity of clean water is C 0 =1250μs / cm, conductivity of secondary washing water C 2 =15423μs / cm, the conductivity of the three-wash water is C 3 =9753μs / cm, Secondary washing water consumption V 2 =1.5×10 6 cm 3 ,Three wash water consumption V 3 =1.5×10 6 cm 3 , according to the following formula,

[0088]

[0089] Find V 0 ≈1.5×10 6 cm 3 .

[0090] The parameters of the three-time washing of the iron oxide red filter cake are shown in Table 1. The washing effect of the iron oxide red filter cake after three-time washing is shown in Table 2. The total amount of clean water used for washing is 1.5m 3 , where the conductivity of the primary wash water is C 1 =24903μs / cm, the condition for recycling the primary washing water into the slurry tank 1 has not yet been met.

[0091] Example 2: Add clean water to the secondary wash water (the difference in conductivity between the primary wash water and the secondary wash water

[0092] The iron oxide red filter cake was washed according to the method in Example 1, wherein the conductivity of the secondary washing water in the secondary washing water tank 6 was measured to be C 2 =17327μs / cm, the conductivity of the secondary wash water in the secondary wash water tank 6 exceeds the rated value of 16000μs / cm, and the conductivity of the primary wash water in the primary wash water tank 5 is C 1 =24859μs / cm, C 0 =1250μs / cm, so ΔC1-2 =7532μs / cm, and the minimum allowable conductivity difference between the first wash water and the second wash water Obviously, Use the clean water in the clean water tank 4 to add 0.2×10 6 cm 3 After the clean water, the conductivity of the secondary washing water is C 2 =15184μs / cm, so that ΔC 1-2 =9675μs / cm, meeting the conditions for secondary washing water reuse.

[0093] In this embodiment, the total amount of water-soluble matter in the initial iron oxide red filter cake is M=7.42 kg, and the total amount of water-soluble matter allowed to remain in the iron oxide red filter cake after washing is M std =0.66kg, the conductivity of clean water is C 0 =1250μs / cm, conductivity of secondary washing water C 2 =15184μs / cm, the conductivity of the three-wash water is C 3 =9700μs / cm, Secondary washing water consumption V 2 =1.5×10 6 cm 3 , three wash water consumption V 3 =1.5×10 6 cm 3 , V add2 =0.2×10 6 cm 3 According to the following formula,

[0094]

[0095] Find V 0 ≈1.5×10 6 cm 3 , according to V total =V add2 +V add3 +V 0 It can be concluded that V total =1.7×10 6 cm 3 .

[0096] Clean water was added to the secondary washing tank 6. The parameters of the three washings of the iron oxide red filter cake are shown in Table 1. The washing effect after washing is shown in Table 2. The total amount of clean water used for washing is 1.7m 3 Among them, the conductivity of the first wash water is C 1 =24859μs / cm, the condition for recycling the primary washing water into the slurry tank 1 has not yet been met.

[0097] Example 3: Add clean water to the three wash water (the difference in conductivity between the second wash water and the third wash water

[0098] The iron oxide red filter cake was washed according to the method in Example 1, wherein the conductivity of the three wash water in the three wash water tank 6 was measured to be C 3 =12675μs / cm, the conductivity of the tertiary wash water in the tertiary wash water tank 7 exceeds the rated value of 9800μs / cm, and the conductivity of the secondary wash water in the secondary wash water tank 5 is C 2 =15078μs / cm, C 0 =1250μs / cm, so ΔC 2-3 =2403μs / cm, and the minimum allowable conductivity difference between the secondary wash water and the tertiary wash water Obviously, Use the clean water in the clean water tank 4 to add 0.4×10 6 cm 3 After the clean water, the conductivity of the three wash water is C 3 =9629μs / cm, so that ΔC 2-3 =5449μs / cm, which meets the conditions for tertiary washing water reuse.

[0099] In this embodiment, the total amount of water-soluble matter in the initial iron oxide red filter cake is M=7.42 kg, and the total amount of water-soluble matter allowed to remain in the iron oxide red filter cake after washing is M std =0.63kg, the conductivity of clean water is C 0 =1250μs / cm, conductivity of secondary washing water C 2 =15078μs / cm, the conductivity of the three-wash water is C 3 =9629μs / cm, Secondary washing water consumption V 2 =1.5×10 6 cm 3 , three wash water consumption V 3 =1.5×10 6 cm 3 , V add3 =0.4×10 6 cm 3 , according to the following formula

[0100]

[0101] Find V 0 ≈1.5×10 6 cm 3 , according to V total =V add2 +V add3 +V 0It can be concluded that V total =1.9×10 6 cm 3 .

[0102] Clean water was added to the three-wash tank 7. The parameters of the three-washing of the iron oxide red filter cake are shown in Table 1. The washing effect after washing is shown in Table 2. The total amount of clean water used for washing is 1.9m 3 Among them, the conductivity of the first wash water is C 1 =24744μs / cm, the condition for recycling the primary washing water into the slurry tank 1 has not yet been met.

[0103] Comparative example: Three washes were all done with clean water

[0104] The iron oxide red filter cake was washed according to the method in Example 1.

[0105] In this embodiment, the total amount of water-soluble matter in the initial iron oxide red filter cake is M=7.42 kg, and the total amount of water-soluble matter allowed to remain in the iron oxide red filter cake after washing is M std =0.44kg, the conductivity of clean water is C 0 =1250μs / cm, the conductivity of the washing water is C 1 =21182μs / cm, conductivity of secondary washing water C 2 =12765μs / cm, the conductivity of the three-wash water is C 3 =8982μs / cm, 1.5m was used for all three washes 3 The parameters of the three washings of the iron oxide red filter cake are shown in Table 1, and the washing effect after washing is shown in Table 2. The total amount of clean water used for washing is 4.5m 3 .

[0106] Table 1: Parameters of Examples 1-3 and Comparative Examples

[0107]

[0108] As can be seen from Table 1, through the above three embodiments and comparative examples, when treating the same volume of red iron oxide slurry, the total amount of clean water used in Example 1 is equivalent to 33.3% of the comparative example, the total amount of clean water used in Example 2 is equivalent to 37.8% of the comparative example, and the total amount of clean water used in Example 3 is equivalent to 42.2% of the comparative example.

[0109] Table 2: Washing effect table of Examples 1-3 and Comparative Examples

[0110]

[0111] As can be seen from Table 2, according to GB / T 1863-2008 Iron Oxide Pigments, the washing effects of Examples 1, 2, 3 and the comparative example, where the purity of the iron oxide red product is expressed by the ferric oxide content, all reached Class A not less than 95%; the washing effects of Examples 1, 2, 3 and the comparative example, where the mass fraction of water-soluble matter (measured after drying at 105°C) of the higher quality Type I red and brown products is ≤0.3%; the washing effects of Examples 1, 2, 3 and the comparative example, where the total mass fraction of water-soluble oxides and sulfates (measured by Cl- and SO 4 2- Indicates) only the comparative example ≤0.1%, and Examples 1, 2, and 3 are slightly greater than 0.1%; the washing effects of Examples 1, 2, 3 and the comparative example, wherein the mass fraction % of the sieve residue (45 μm) are all >0.1, ≤1, meet the Type 3 standard.

Claims

1. A water-saving method in the preparation process of red iron oxide, wherein the filter cake formed after the filter pressing is washed during the filter pressing and washing process of the red iron oxide slurry, characterized in that The washing comprises: The red iron oxide filter cake is washed for the first time with the secondary washing water, and the water after washing the filter cake forms the primary washing water; The red iron oxide filter cake is washed a second time with the tertiary washing water, and the water after washing the filter cake forms the secondary washing water; The red iron oxide filter cake is washed for the third time with clean water, and the water after washing the filter cake forms the third washing water; The total amount of clean water used for washing each batch of iron oxide red filter cake is: Where, M is the total amount of water-soluble matter in the initial iron oxide red filter cake, M std The total amount of water-soluble matter allowed to remain in the red iron oxide filter cake after washing; The conductivity of the secondary wash water is C2, and the amount of secondary wash water is V2; The conductivity of the tertiary washing water is C3, and the amount of tertiary washing water is V3; The amount of clean water is V0, and the conductivity of clean water is C0; k1 is the migration coefficient of water-soluble matter during the first wash, k2 is the migration coefficient of water-soluble matter during the second wash, and k3 is the migration coefficient of water-soluble matter during the third wash.

2. The water-saving method in the preparation process of red iron oxide according to claim 1, characterized in that The water-soluble matter migration coefficient k1 during the first washing is The migration coefficient k2 of water-soluble matter during the second washing is The migration coefficient k3 of water-soluble matter during the third washing is 885~ 3. The water-saving method in the preparation process of red iron oxide according to claim 1, characterized in that The secondary wash water and the tertiary wash water include the replenished clean water; after replenishing the clean water into the secondary wash water and / or the tertiary wash water, the total amount of clean water is: V total =V add2 +V add3 +V0 It should also meet: Where V total is the total amount of clean water used, V add2 V is the amount of clean water added to the secondary wash water. add3 To replenish the amount of clean water in three washes, is the minimum permissible conductivity difference between the primary wash water and the secondary wash water, It is the minimum allowable conductivity difference between the secondary wash water and the tertiary wash water.

4. A water-saving method in a red iron oxide preparation process according to claim 1 or 3, characterized in that The conductivity of the clean water is C0, which is 1250 μs / cm.

5. A water-saving method in a process for preparing red iron oxide according to claim 1 or 3, characterized in that The conductivity C3 of the tertiary washing water is ≤9800 μs / cm.

6. A water-saving method in a process for preparing red iron oxide according to claim 1 or 3, characterized in that The conductivity C2 of the secondary washing water is ≤16000 μs / cm.

7. The water-saving method in the preparation process of red iron oxide according to claim 3, characterized in that The minimum permissible conductivity difference between the primary wash water and the secondary wash water is 8. The water-saving method in the preparation process of red iron oxide according to claim 3, characterized in that The minimum permissible conductivity difference between the secondary wash water and the tertiary wash water is 9. The water-saving method in the preparation process of red iron oxide according to claim 1, characterized in that When the conductivity of the primary washing water exceeds 32000 μs / cm, the primary washing water is introduced into a pulping tank to pulp the calcined red iron oxide.

10. The water-saving method in the preparation process of red iron oxide according to claim 1, characterized in that The primary washing water, secondary washing water and tertiary washing water are stored in the primary washing water tank, the secondary washing water tank and the tertiary washing water tank respectively, and the clean water is stored in the clean water tank.

11. The water-saving method in the preparation process of red iron oxide according to claim 10, characterized in that When the conductivity of the secondary wash water in the secondary wash water tank exceeds the rated value of 16000 μs / cm, clean water is passed from the clean water tank into the secondary wash water tank until the conductivity is lower than the rated value of 16000 μs / cm.

12. The water-saving method in the preparation process of red iron oxide according to claim 10, characterized in that When the conductivity of the tertiary wash water in the tertiary wash water tank exceeds the rated value of 9800 μs / cm, clean water is passed from the clean water tank into the tertiary wash water tank until the conductivity is lower than the rated value of 9800 μs / cm.

13. The water-saving method in the preparation process of red iron oxide according to claim 10, characterized in that In the initial stage of washing the red iron oxide filter cake, that is, when there is no primary washing water in the primary washing water tank, the red iron oxide filter cake is washed for the first time with clean water to form primary washing water which is stored in the primary washing water tank.

14. The water-saving method in the preparation process of red iron oxide according to claim 10, characterized in that In the initial stage of washing the red iron oxide filter cake, that is, when there is no secondary washing water in the secondary washing water tank, the red iron oxide filter cake is washed for the second time with clean water to form secondary washing water which is stored in the secondary washing water tank.

15. The water-saving method in the preparation process of red iron oxide according to claim 10, characterized in that In the initial stage of washing the red iron oxide filter cake, that is, when there is no third washing water in the third washing water tank, the red iron oxide filter cake is washed for the third time with clean water to form third washing water which is stored in the third washing water tank.

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