Waste recovery treatment method in titanium dioxide production process

Abstract

The invention discloses a method for recycling and treating waste in a titanium dioxide production process, which comprises the following steps: mixing the waste with concentrated sulfuric acid, the waste comprising hydrolyzed metastatic acid, ferric sulfate or ferrous sulfate and titanium dioxide; adding water into the mixture and heating for reaction; carrying out curing reaction; and carrying out leaching treatment on the reactant after the curing reaction, and carrying out solid-liquid separation to obtain liquid and solid. According to the scheme provided by the invention, waste is treated by adopting an acidolysis-like process, so that recycling of the waste is realized, the waste does not need to be subjected to additional process treatment, and the main difference from the acidolysis process is that the waste does not have an acidolysis heat value, so that the whole reaction process needs to be subjected to heat compensation in the whole process. The leaching solution is directly recycled into the titanium solution for production, a small amount of generated solids are treated along with acidolysis residues in the sulfuric acid method titanium dioxide production process, no new waste is generated, and the existing process is not influenced.

Description

Technical Field

[0001] The invention relates to the field of titanium dioxide production, and in particular to a method for recycling waste in a titanium dioxide production process. Background Art

[0002] In the titanium dioxide industry, ferrous sulfate is mostly used to prepare sulfuric acid and iron by-products. A certain amount of solid waste will be generated during the production process. However, in the current production process, this waste will be directly discarded as waste and cannot be recycled, resulting in a waste of resources. Summary of the invention

[0003] In view of this, in order to overcome at least one aspect of the above problems, an embodiment of the present invention proposes a method for recycling waste in a titanium dioxide production process, comprising the following steps: Mixing the waste with concentrated sulfuric acid, wherein the waste includes hydrolyzed skew acid, ferric sulfate or ferrous sulfate, and titanium dioxide; Add water to the mixture and heat to react; Performing a aging reaction; The reactants after the aging reaction are subjected to leaching treatment and solid-liquid separation to obtain liquid and solid.

[0004] In some embodiments, mixing the waste with concentrated sulfuric acid further comprises: The weight ratio of concentrated sulfuric acid to waste is 1.46-1.56.

[0005] In some embodiments, the concentration of concentrated sulfuric acid is 94%-98%.

[0006] In some embodiments, water is added to the mixture and heated to react, further comprising: Add water to the mixture and dilute the acid concentration to 80%-84%; Continue heating until the reaction is complete.

[0007] In some embodiments, heating is continued until the reaction is complete, further comprising: If the volume of the mixture expands and then falls back, the reaction is determined to be complete and heating is stopped.

[0008] In some embodiments, performing the aging reaction further comprises: The aging is carried out at a temperature of 160°C-175°C and the aging time is 60min-90min.

[0009] In some embodiments, the reactants after the aging reaction are subjected to a leaching process, further comprising: The amount of leaching water is determined based on the total titanium concentration in the liquid being 120g / L-140g / L.

[0010] In some embodiments, it also includes: The leaching is carried out at a temperature of 60°C-75°C and a leaching time of 60min-120min.

[0011] In some embodiments, it also includes: The liquid is returned to the titanium liquid process as a titanium clear liquid to continue producing titanium dioxide, and the solid is subjected to residue treatment.

[0012] In some embodiments, the titanium dioxide in the waste is anatase.

[0013] The present invention has one of the following beneficial technical effects: the scheme proposed by the present invention realizes the recycling of waste by using a process similar to acidolysis to treat waste, and does not require additional process treatment of the waste. The main difference from the acidolysis process is that the waste itself does not have the acidolysis calorific value, so the entire reaction process needs to be supplemented with heat throughout the process. The leaching liquid is directly recycled to the titanium liquid for production, and the small amount of solid produced is treated with the acidolysis residue in the sulfuric acid process titanium dioxide production process, without generating new waste and without any impact on the existing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other embodiments can be obtained based on these drawings without paying creative work.

[0015] Figure 1 A schematic flow chart of a waste recycling method in a titanium dioxide production process provided by an embodiment of the present invention; Figure 2 XRD results of titanium in waste provided by the embodiments of the present invention; Figure 3 A schematic diagram of particle size distribution of waste and titanium concentrate provided in an embodiment of the present invention; Figure 4 The present invention provides a waste acid hydrolysis experiment and its results. DETAILED DESCRIPTION

[0016] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0017] It should be noted that all expressions using "first" and "second" in the embodiments of the present invention are for distinguishing two non-identical entities with the same name or non-identical parameters. It can be seen that "first" and "second" are only for the convenience of expression and should not be understood as limitations on the embodiments of the present invention. The subsequent embodiments will not explain this one by one.

[0018] According to one aspect of the present invention, an embodiment of the present invention provides a method for recycling waste in a titanium dioxide production process, such as Figure 1 As shown, it may include the steps of: Mixing the waste with concentrated sulfuric acid, wherein the waste includes hydrolyzed skew acid, ferric sulfate or ferrous sulfate, and titanium dioxide; Add water to the mixture and heat to react; Performing a ripening reaction; The reactants after the aging reaction are subjected to leaching treatment and solid-liquid separation to obtain liquid and solid.

[0019] The solution proposed by the present invention realizes the recycling of waste by using a process similar to acidolysis to treat waste, and does not require additional process treatment of the waste. The main difference from the acidolysis process is that the waste itself does not have the calorific value of acidolysis, so the entire reaction process needs to be supplemented with heat. The leaching liquid is directly recycled to the titanium liquid for production, and the small amount of solid produced is treated with the acidolysis residue in the sulfuric acid process of titanium dioxide production, so no new waste is generated and there is no impact on the existing process.

[0020] In some embodiments, ferrous sulfate is mostly used in the titanium dioxide industry to prepare sulfuric acid and other iron byproducts, and a certain amount of solid waste is generated during the production process, which is directly discarded as waste. The present invention can perform harmless treatment on the waste and recover more than 87% of titanium and iron in the waste.

[0021] The waste contains 23.46% water. After the water is dried, the main components of the waste include SO3, Fe2O3, and TiO2. That is, the waste is mainly hydrolyzed skewed acid and ferrous sulfate or ferrous sulfate that has not been recovered cleanly, and has the possibility of acid hydrolysis and washing iron removal. Although the waste after drying has the possibility of acid hydrolysis, in actual operation, the optimal conditions for acid hydrolysis still need to be considered. For example, factors such as the amount of acid, reaction temperature, and reaction time need to be optimized. Due to the complex composition of the waste, it may be necessary to determine the most suitable acid hydrolysis conditions through experiments to ensure the maximum leaching of titanium and iron while avoiding the occurrence of side reactions. For example, an orthogonal experimental design can be used to study the effects of acid concentration, reaction temperature, and time on the leaching rate of titanium and iron, so as to find the optimal acid hydrolysis process parameters.

[0022] In addition, during the acid hydrolysis process, the corrosion resistance of the reaction equipment needs to be considered. Because it involves acidic substances and possible high-temperature reactions, the equipment needs to be able to withstand these conditions. Appropriate materials can be selected, such as a reactor lined with polytetrafluoroethylene, to ensure the service life of the equipment and the safety of the reaction.

[0023] In some embodiments, mixing the waste with concentrated sulfuric acid further comprises: The weight ratio of concentrated sulfuric acid to waste is 1.46-1.56.

[0024] In some embodiments, the concentration of concentrated sulfuric acid is 94%-98%.

[0025] In some embodiments, water is added to the mixture and heated to react, further comprising: Add water to the mixture and dilute the acid concentration to 80%-84%; Continue heating until the reaction is complete.

[0026] Specifically, the waste contains 20% water, which is significantly different from titanium concentrate. The titanium concentrate used for acid hydrolysis contains almost no water. In addition, the titanium in the waste exists in the anatase form, and the reaction is an endothermic reaction, while the acid hydrolysis of titanium concentrate is an exothermic reaction and does not require heat supplement after initiation, while the waste requires heat supplement throughout the process.

[0027] Acid hydrolysis reactions usually need to be carried out under specific concentration conditions to ensure that the reaction can be carried out efficiently and stably. The waste contains 20% water. Compared with titanium concentrate, which contains almost no water, this large amount of water will dilute the acid used for acid hydrolysis. For example, when sulfuric acid is used for acid hydrolysis, the actual concentration of sulfuric acid will decrease after the originally suitable concentration of sulfuric acid is mixed with the waste due to the presence of water, which may affect the rate and degree of the acid hydrolysis reaction. The acid hydrolysis reaction may not achieve the desired effect, such as the leaching rate of titanium may decrease, resulting in incomplete resource recovery. Therefore, a higher concentration of sulfuric acid is required.

[0028] In some embodiments, heating is continued until the reaction is complete, further comprising: If the volume of the mixture expands and then falls back, the reaction is determined to be complete and heating is stopped.

[0029] Specifically, during a chemical reaction, chemical bonds between reactant molecules break and recombine to form new product molecules. When the reaction proceeds, some physical phenomena may occur, such as changes in volume. For this particular reaction, in the early stages of the reaction, as the reaction progresses, the volume of the mixture may expand due to factors such as the interaction between reactants, the generation of new substances, and the possible generation of gas. When the reaction is complete, the system reaches a relatively stable state, new substances no longer continue to be generated, and gas generation stops (if any gas is generated). At this time, the volume of the mixture will fall back to a relatively stable value, which provides an observable feature for judging whether the reaction is complete. At the beginning of the reaction, as the reactants gradually transform into products, the composition and state of the substances in the reaction system continue to change, and volume expansion is an external manifestation of this change. Once the reaction is complete, it means that all reactants that can react have been converted, and there is no new substance generation and state change in the system, so the volume will fall back and remain stable. Through this dynamic observation of volume changes, the progress of the reaction can be grasped more accurately, so as to determine whether the reaction is truly completed.

[0030] It is very important to stop heating in time when the reaction is complete. On the one hand, this can avoid energy waste caused by overheating. If the heating is continued when the reaction is already completed, the extra heat consumed is not used to promote the reaction, but is wasted, increasing production costs. On the other hand, overheating may have adverse effects on the reaction products. For example, it may cause the product to decompose, deteriorate, or cause some unnecessary side reactions, thereby affecting the quality of the product and its subsequent utilization value.

[0031] In some embodiments, performing the aging reaction further comprises: The aging is carried out at a temperature of 160°C-175°C and the aging time is 60min-90min.

[0032] In some embodiments, the reactants after the aging reaction are subjected to a leaching process, further comprising: The amount of leaching water is determined based on the total titanium concentration in the liquid being 120g / L-140g / L.

[0033] In some embodiments, it also includes: The leaching is carried out at a temperature of 60°C-75°C and a leaching time of 60min-120min.

[0034] Specifically, the premixed waste does not need to be dried, the concentration of concentrated sulfuric acid is 94%-98%, and the premixed acid-ore ratio is 1.46-1.56. The initiating water volume is diluted to a reaction acid concentration of 80%-84%, the aging temperature is 160℃-175℃, and the aging time is 60min-90min. The leaching water volume is to control the total titanium concentration in the liquid phase to 120g / L-140g / L, the leaching temperature is 60℃-75℃, and the leaching time is 60min-120min.

[0035] In some embodiments, it also includes: The liquid is returned to the titanium liquid process as a titanium clear liquid to continue producing titanium dioxide, and the solid is subjected to residue treatment.

[0036] In some embodiments, the titanium dioxide in the waste is anatase.

[0037] Specifically, Figure 2 The XRD results shown in the figure show that the titanium in the waste mainly exists in the form of anatase titanium dioxide, which is significantly different from the existence form of titanium in titanium concentrate.

[0038] Since the waste is a co-precipitate formed by the hydrolysis of titanyl sulfate and the oxidation of ferrous iron, it is considered to use the iron as a titanium dioxide product after washing. However, due to the special properties of the co-precipitate, the iron cannot be effectively removed by simple water washing or acid washing with the addition of a certain amount of sulfuric acid, hydrochloric acid or other acids. In the end, 4% of the iron will be difficult to remove. The titanium dioxide industry requires that the iron content in titanium dioxide be below 30ppm. Therefore, it is not possible to remove the iron by washing to obtain titanium dioxide.

[0039] like Figure 3 The comparison results of the particle size of the waste and the particle size of the titanium concentrate are shown in the figure. It can be seen from the figure that the particle size distribution of the waste and the titanium concentrate is similar and has the possibility of acid hydrolysis treatment. The chemical reaction that occurs is: TiO2+H2SO4=TiOSO4+H2O TiO2+2H2SO4=TiSO4+2H2O After the waste is treated, the main components of the filtrate are about 130g / L titanium and about 7g / L iron, and there is almost no other impurities. The main components of the clear titanium liquid after acid hydrolysis are about 130g / L titanium and about 40g / L iron, as well as some other trace elements such as Si, Mg, and Ca. Mixing the two will not cause any impact and will not affect the normal titanium dioxide production process. The unreacted products after the waste reaction can be directly mixed with the acid hydrolysis residue of titanium concentrate for treatment, and no additional disposal is required. In this way, by using a process similar to acid hydrolysis to treat waste, waste recycling is achieved, and no additional process is required for waste treatment. The main difference from the acid hydrolysis process is that the waste itself does not have the calorific value of acid hydrolysis, so the entire reaction process requires heat supplementation. The leaching liquid is directly recycled to the titanium liquid for production, and the small amount of solid produced is treated with the acid hydrolysis residue in the sulfuric acid method titanium dioxide production process, without generating new waste and without any impact on the existing process.

[0040] Example 1 Mix 50g of waste with 74.49g of concentrated sulfuric acid with a concentration of 98% (acid-ore ratio 1.46), add 16.76g of water to initiate (reaction acid concentration is 80%), and increase the temperature (keep heating, no need to control the temperature). After the reaction is completed (manifested by a slight expansion of the volume and then a fall), put the reactants and the reaction container into an oven and stay at 160°C for 60 minutes (maturation). After the aging is completed, add 200mL of water and heat and stir in a 60°C water bath for 60 minutes. Use a funnel to separate the solid and liquid of the leached mixture. The liquid phase is the clear titanium liquid, which can be mixed into the clear titanium liquid of sulfuric acid titanium dioxide as a raw material for sulfuric acid titanium dioxide; the residue is mixed into the acidolysis residue of sulfuric acid titanium dioxide for treatment.

[0041] Example 2 Mix 50g of waste with 79.79g of concentrated sulfuric acid with a concentration of 94% (acid-ore ratio of 1.5), add 11.68g of water to initiate (reaction acid concentration is 82%), and heat up (keep heating without controlling the temperature). After the reaction is completed (manifested by a slight expansion of the volume and then a fall), put the reactants and the reaction container into an oven and stay at 165°C for 80min (maturation). After the aging is completed, add 200mL of water and heat and stir in a 65°C water bath for 90min. Use a funnel to separate the solid and liquid of the leached mixture. The liquid phase is the clear titanium liquid, which can be mixed into the clear titanium liquid of sulfuric acid titanium dioxide as a raw material for sulfuric acid titanium dioxide; the residue is mixed into the acidolysis residue of sulfuric acid titanium dioxide for treatment.

[0042] Example 3 Mix 50g of waste with 81.25g of 96% concentrated sulfuric acid (acid-ore ratio 1.56), add 11.61g of water to initiate (reaction acid concentration is 84%), and heat up (keep heating, no need to control temperature). After the reaction is completed (manifested by a slight expansion and then a fall in volume), put the reactants and the reaction container into an oven and stay at 175°C for 90min (maturation). After the aging is completed, add 200mL of water and heat and stir in a 75°C water bath for 120min. Use a funnel to separate the solid and liquid of the leached mixture. The liquid phase is the clear titanium liquid, which can be mixed into the sulfuric acid titanium white clear titanium liquid as the sulfuric acid titanium white raw material; the residue is mixed into the sulfuric acid titanium white acid hydrolysis residue for treatment.

[0043] like Figure 4 As shown, the present invention can basically recover more than 87.6% of iron and titanium in the waste.

[0044] The above are exemplary embodiments disclosed in the present invention, but it should be noted that various changes and modifications may be made without departing from the scope disclosed in the embodiments of the present invention as defined in the claims. The functions, steps and / or actions of the method claims according to the disclosed embodiments described herein do not need to be performed in any particular order. In addition, although the elements disclosed in the embodiments of the present invention may be described or required in individual form, they may also be understood as multiple unless explicitly limited to the singular.

[0045] It should be understood that, as used herein, the singular forms "a", "an" are intended to include the plural forms as well, unless the context clearly supports an exception. It should also be understood that, as used herein, "and / or" refers to any and all possible combinations including one or more of the associated listed items.

[0046] The serial numbers of the embodiments disclosed in the above embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

[0047] A person skilled in the art should understand that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the disclosure of the embodiments of the present invention (including the claims) is limited to these examples; under the concept of the embodiments of the present invention, the technical features in the above embodiments or different embodiments can also be combined, and there are many other changes in different aspects of the above embodiments of the present invention, which are not provided in detail for the sake of simplicity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present invention should be included in the protection scope of the embodiments of the present invention.

Claims

1. A method for recycling waste in a titanium dioxide production process, characterized in that: The following steps are involved: Mixing the waste with concentrated sulfuric acid, wherein the waste includes hydrolyzed skew acid, ferric sulfate or ferrous sulfate, and titanium dioxide; Add water to the mixture and heat to react; Performing a aging reaction; The reactants after the aging reaction are subjected to leaching treatment and solid-liquid separation to obtain liquid and solid.

2. The method according to claim 1, characterized in that Mixing the waste with concentrated sulfuric acid further comprises: The weight ratio of concentrated sulfuric acid to waste is 1.46-1.

56.

3. The method according to claim 1, characterized in that The concentration of concentrated sulfuric acid is 94%-98%.

4. The method according to claim 3, characterized in that Adding water to the mixture and heating to react, further comprising: Add water to the mixture and dilute the acid concentration to 80%-84%; Continue heating until the reaction is complete.

5. The method according to claim 4, characterized in that The heating is continued until the reaction is complete, further comprising: If the volume of the mixture expands and then falls back, the reaction is determined to be complete and heating is stopped.

6. The method according to claim 1, characterized in that Carrying out a aging reaction further comprises: The aging is carried out at a temperature of 160°C-175°C and the aging time is 60min-90min.

7. The method according to claim 1, characterized in that The reactants after the aging reaction are subjected to leaching treatment, further comprising: The amount of leaching water is determined based on the total titanium concentration in the liquid being 120g / L-140g / L.

8. The method according to claim 7, characterized in that Also includes: The leaching is carried out at a temperature of 60°C-75°C and a leaching time of 60min-120min.

9. The method according to claim 1, characterized in that Also includes: The liquid is returned to the titanium liquid process as a titanium clear liquid to continue producing titanium dioxide, and the solid is subjected to residue treatment.

10. The method according to claim 1, characterized in that The titanium dioxide in the waste is anatase type.

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