Selective separation of sodium carbonate and salt from a solution containing sodium carbonate and salt, and production of caustic

Abstract

The present invention relates to a process for the recovery of waste materials by producing soda ash, sodium hydroxide and hydrogen via converting the liquid and solid wastes, which are generated as a result of production from the Trona ore using solution mining and underground production methods, into a solution; and a process that will enable production in brine production areas that are currently not suitable for production.

Description

[0001] SELECTIVE SEPARATION OF SODIUM CARBONATE AND SALT FROM A SOLUTION CONTAINING SODIUM CARBONATE AND SALT, AND PRODUCTION OF CAUSTIC

[0002] Field of the Invention

[0003] The present invention relates to a process for the recovery of waste materials by producing soda ash, sodium hydroxide and hydrogen via converting the liquid and solid wastes, which are generated as a result of production from the Trona ore using solution mining and underground production methods, into a solution; and a process that will enable production in brine production areas that are currently not suitable for production.

[0004] Background of the Invention

[0005] In the field of the invention, various methods are used for caustic production purposes. However, these methods have certain disadvantages. The main disadvantages are listed below:

[0006] • Low efficiency of the lime slaking process due to the high salt content,

[0007] • High energy consumption and inability to return the energy to the system,

[0008] • The salt being discharged as a solid from the system after being subjected to evaporation,

[0009] • Increased amount of CO2 gas emission during the lime slaking process.

[0010] The state-of-the-art patent document with application number TR 2017 / 15323 B discloses a process of producing soda ash and sodium bicarbonate from bicarbonate solutions obtained from trona ore by solution mining method, reducing the amount of waste by process optimization and recovering thereof as a product. According to the said document, the deca-purge waste discharged from the decahydrate crystallization system is used in caustic production. The total alkalinity in the deca-purge is used in caustic production to convert the sodium carbonate into caustic. In caustic production, the process steps of lime slaking causticization & clarification - weak caustic tank - caustic evaporation - centrifuge - clarification are used respectively. However, the said method does not have the capacity to fully utilize the entire deca-purge waste that is produced. Furthermore, due to the low efficiency of the system used, the product recovery efficiency is low. The said document additionally includes a caustic evaporation system and 30% caustic solution is produced from deca-purge, which is the process waste. However, due to the inefficient operation of the system, the required amount for the process cannot be met, and thus caustic is purchased from outside. In this process, which constitutes the state of the art, the lime mud discharged from the caustic system in the lime recovery plant must be recovered for internal use and reused in the caustic production phase. This results in both energy costs and raw material costs. The patent application with publication number US5283054 discloses obtaining decahydrate crystals from bicarbonate-containing solutions via solution mining. In the patent document with application number TR 2017 / 15323 B, prior to decahydrate crystallization, all of the bicarbonate in the solution is eliminated by caustic soda treatment. In the current process, the caustic soda used therein is produced from the deca-purge which is the process waste, however not all of the resulting waste can be utilized thereby requiring the waste to be stored in the reservoirs, and additionally, due to the low efficiency during production, the system is required to be supplied with caustic soda from outside.

[0011] As a result, due to the above-mentioned disadvantages and the inadequacy of the existing solutions, it has become necessary to make a development in the related technical field.

[0012] Summary of the Invention

[0013] The present invention relates to a caustic production process that meets the above-mentioned requirements, eliminates all disadvantages, and introduces certain additional advantages.

[0014] The invention is inspired by the existing state of the art and aims to solve the above-mentioned disadvantages.

[0015] The main object of the invention relates to the selective separation of sodium carbonate and salt from solutions as well as solid wastes containing sodium carbonate and salt, and production of caustic.

[0016] In the present invention, contrary to the state of the art, the process wastes that cannot be used during production are utilized and recycled back into the system. This in turn allows almost all of the raw solution to be used in the production of the end product, increasing the production efficiency and at the same time eliminating the need for external procurement of slaked lime. Electricity is generated with the hydrogen gas formed within the system after electrolysis, and almost all of the energy consumed by the system (since it does not work with 100% efficiency) is met therefrom.

[0017] In the present invention, contrary to the state of the art, the direct recovery of the sodium carbonate in the system and the sodium hydroxide to be produced eliminates the need to re-add caustic into the system. At the same time, this makes the process advantageous in terms of cost and waste management.

[0018] In the present invention, contrary to the state of the art, the existing alkalinity in the deca-purge is kept completely constant and the sodium chloride in the product is converted into sodium hydroxide as a result of the chemical reaction, thereby enabling caustic production, while at the same time recovering all the sodium carbonate contained therein.

[0019] Thanks to the present invention, due to the recycling of the wastes, the efficiency of the plant is increased and production costs are reduced, and also elements that will harm human health and the environment are eliminated through green energy production, thereby establishing a sustainable environmental management system.

[0020] Salt, which is a waste as a result of the production disclosed in the patent document with application number TR 2017 / 15323 B, is used as a raw material in the system of the present invention, creating a significant advantage in terms of cost and waste management. At the same time, the Chlorine gas and Hydrogen gas that will be formed in the system can be converted into products. The chlorine gas generated in the system can be produced as Liquid chlorine, Hydrochloric acid and Hypochlorite using three different production methods and resulting in production of different product types. Thus, in addition to the ore extracted from the underground, the salt extracted together with the ore is also included in the production. At the same time, a process in which the most efficient production methods are used with minimum waste and cost is implemented.

[0021] In the present invention, unlike the state of the art, a solution is obtained by using the solution preparation tank - purge injection tank - electrolysis circuit - separator system, respectively. In addition, the hydrogen gas to be obtained as a product with the present invention is used in energy production. The brine solution entering the electrolysis system passes through the solution preparation tank - brine injection tank - electrolysis circuit - separator system, and the discharged chlorine gas is obtained as liquid chlorine, hydrochloric acid and sodium hypochlorite, resulting in production of new products. The brine solution coming out of the electrolysis system proceeds to the brine crystallization - brine centrifugation - drying & packaging system whereby it is turned into refined salt ready for sale. Thus, a plurality of products will be obtained from the ore extracted from the underground, extending operational life and ensuring continuity in the system while increasing the production returns.

[0022] In the present invention, unlike the state of the art, sodium carbonate and sodium hydroxide are obtained simultaneously by providing highly efficient separation in the electrolysis circuit without the need to react with any by-product. Therefore, it can be fed to the process without the need for a second evaporation process. This prevents unnecessary energy consumption and costs.

[0023] In the present invention, unlike the state of the art, all of the solution and solid wastes discharged from the systems are used as raw materials after being converted into solutions of suitable concentration. The structural and characteristic features and all advantages of the invention will be more clearly understood by the accompanying figures and the detailed description written by referring to these figures, and therefore the invention should be evaluated taking into consideration the said figures and the detailed description.

[0024] Figures to Help Understand the Invention

[0025] In order to best understand the configuration and advantages of the present invention, it should be evaluated together with the figures described below.

[0026] Schematic representation of the process is provided in Figure 1.

[0027] Description of the Reference Numbers of the Parts

[0028] 110 Solution preparation tank-1

[0029] 120 Purge injection tank

[0030] 130 Anolyte chamber

[0031] 140 Separator- 1

[0032] 150 Sodium carbonate -sodium hydroxide solution tank

[0033] 160 Hydrogen gas storage system

[0034] 170 Cogeneration plant

[0035] 210 Solution preparation tank-2

[0036] 220 Brine injection tank

[0037] 230 Catholyte chamber

[0038] 240 Separator-2

[0039] 250 Brine solution tank

[0040] 260 Brine crystallization unit

[0041] 270 Brine centrifuge

[0042] 280 Drying and packaging

[0043] 290 Chlorine gas storage tank

[0044] 300 Chlorine cooling unit

[0045] 310 Hydrochloric acid production tank

[0046] 320 Sodium hypochlorite production tank

[0047] 400 Liquid chlorine storage tank Detailed Description of the Invention

[0048] In this detailed description, preferred embodiments of the invention are described only for the purpose of facilitating a better understanding of the subject matter.

[0049] The invention relates to a process for the recovery of waste materials by producing soda ash, sodium hydroxide and hydrogen via converting the liquid and solid wastes, which are generated as a result of production from the Trona ore using solution mining and underground production methods, into a solution; and a process that will enable production in brine production areas that are currently not suitable for production.

[0050] Sodium carbonate and caustic soda are obtained from the bicarbonate solution fed to the integrated process of the present invention. In the method of the present invention, by producing caustic soda from liquid and solid wastes containing high impurities and salt instead of a raw solution, wastes are utilized as well as achieving a more cost-effective method. By means of this process, solutions rich in alkalinity and salt, containing impurities, and solid wastes containing sodium carbonate and salt are utilized. The solution reaching the appropriate concentration and temperature in the solution preparation tank (110) is transferred to the purge injection tank (120). Here, more solution is stored than is required for production. The solution leaving the purge injection tank (120) enters the anolyte chamber (130) within the electrolysis circuit. Upon undergoing electrodialysis therein, the solution and gases leave the system and reach the separator (140). After being separated in the separator (140) the solution and hydrogen gas exit the system. The separated solution reaches the sodium carbonate-sodium hydroxide solution tank (150), and after the necessary analyses are conducted therein, the entire solution is added to the solution containing sodium carbonate, sodium bicarbonate and salt, which is brought into a solution after solution mining or underground production, to neutralize the sodium bicarbonate concentration.

[0051] At the same time, the hydrogen gas leaving the separator (140) is sent to the hydrogen gas storage system (170). The hydrogen gas stored therein is transferred to the cogeneration plant (180) for green energy production.

[0052] During the production of 10% caustic soda, the waste from the caustic system disclosed in the patent document numbered TR 2017 15323 B and the sodium carbonate and salt discharged as solid waste after underground production are utilized upon being converted back into raw materials and used in caustic production. The solid waste salt discharged from the systems is transferred, along with raw water, to the solution preparation tank-2 (210). The solution prepared at the desired temperature and concentration therein is stored in the brine injection tank and also pumped into the system. The solution leaving the brine injection tank undergoes electrodialysis in the catholyte chamber (230) of the electrolysis circuit and is sent from the system to the separator (240) together with the solution and chlorine gas. The solution leaving the separator is transferred to the brine solution tank (250). The solution leaving the said brine solution tank (250) enters the brine crystallization unit (260). The solution which is crystallized therein moves on to the brine centrifuge (270) where it is recovered in solid form and then is transferred to the drying and packaging (280) process. After passing through the fluidized bed dryer, steam is used therein for heating purposes. With the salt crystal drying and packaging (280) process, the salt end product is obtained from the system. At the same time, the chlorine gas leaving the separator is transferred to the chlorine gas storage tank (290) and stored therein. The gas leaving the chlorine gas storage tank reaches the chlorine cooling unit (300) where it is cooled, and it is obtained as an end product in the liquid chlorine storage tank (400). Additionally, the discharged chlorine gas flows into the hydrochloric acid production tank (310) where it reacts with hydrogen to form hydrochloric acid. The chlorine gas also flows into the sodium hypochlorite production tank (320) where it reacts with sodium hydroxide to form sodium hypochlorite. Each of these three alternatives can be given weight according to the needs of the market. Thus, all of the minerals extracted from the ore can be utilized, achieving low production costs and recovery of products.

[0053] The electrodialysis method is the process in which ionic substances are separated (decomposed) into simpler substances when an electric current passes through them. Electricity is the flow of electrons or ions. For electrolysis to work, the compound must contain ions. This process is carried out by transmitting an electric current into a solution and is usually used in the form of a solution or brine solution. In electrodialysis, two electrodes are immersed in an electrolyte containing ions, and when direct current is applied to the electrodes, sodium ions move towards the negative electrode (cathode) and chloride ions move towards the positive electrode (anode). This is due to electrical attraction. Electrodialysis is a process where chemical compounds in the form of a solution are separated using electrodes by applying direct electric current from the outside. This process is carried out in a closed non-conductive container. Inside this non-conductive container, there are two electrodes immersed in a solution that is separated into + and - charged ions, placed such that they do not contact each other (usually 5-10 cm apart). For the electrolysis process to take place, the said two electrodes are connected to a direct current power supply. Then the voltage, in other words the electric field, created between the electrodes moves the ions dissolved in the water towards the oppositely charged electrodes. As a result of this interaction, positively (+) charged ions move towards the cathode, while negatively (-) charged ions move towards the anode. As a result of these processes, electrodialysis takes place.

[0054] Special membranes with selective permeability suitable for the chemical reactions that are required to take place in the electrodialysis cell are used. These membranes have selective permeability and are anionic membranes that allow only Cl ions to pass through. As a result of the chemical reactions provided by this membrane, sodium hydroxide is produced.

[0055] The technical advantages provided by the invention are summarized below: • Salt is recycled back into the system instead of being removed.

[0056] • Purchasing waste storage areas and converting them into reservoirs is no longer needed.

[0057] • The sodium carbonate within the wastes is recovered and caustic is produced from the salt therein and fed back into the system. This reduces the amount of caustic and lime that companies producing trona purchase from external sources, thereby decreasing external dependency and costs.

[0058] • The hydrogen gas generated as a result of the process is reused for energy production within the scope of green energy.

[0059] • HC1 hydrochloric acid and NaClO sodium hypochlorite are produced with the chlorine gas generated as a result of this process. • In the state-of-the-art inventions, carbon dioxide is released during the process carried out to recover the lime mud generated in caustic production. However, in the system of the present invention, no carbon dioxide gas is produced. This reduces carbon dioxide emissions.

[0060] • Energy consumption is lower compared to other applications in the industrial environment.

Claims

CLAIMS1. A method suitable for caustic production and product recovery from wastes containing sodium carbonate and salt, characterized in that it comprises the following process steps;• after trona mining, transferring the wastes along with raw water to the solution preparation tank (110) where they are converted into a solution prepared at the appropriate concentration,• transferring the solution from the solution preparation tank (110) to the purge injection tank (120),• the solution leaving the purge injection tank (120) entering the anolyte chamber (130) in the electrolysis circuit, and the solution and gases undergoing electrodialysis therein leaving the system and reaching the separator (140),• the solution and hydrogen gas separated in the separator (140) leaving the system, and the separated solution reaching the sodium carbonate-sodium hydroxide solution tank (150), and after the necessary analyses are conducted therein, the entire solution being added to the solution containing sodium carbonate, sodium bicarbonate and salt, which are brought into a solution after solution mining or underground production, thereby neutralizing the sodium bicarbonate concentration,• transferring the solid waste salt discharged following trona mining along with raw water to the solution preparation tank-2 (210), and storing the solution prepared therein at the desired temperature and concentration in the brine injection tank and also pumping it into the system,• the solution leaving the brine injection tank undergoing electrodialysis in the catholyte chamber (230) of the electrolysis circuit and reaching the separator (240) together with the solution and chlorine gas and being output from the system as chlorine gas,• transferring the solution leaving the system to the brine solution tank (250) and the solution leaving the tank entering the brine crystallization unit (260) and being crystallized therein.

2. The method according to Claim 1 , characterized in that it comprises the process step wherein, after the crystallized solution moves on to the brine centrifuge (270) where it is recovered in solid form, it is transferred to the drying and packaging (280) process and obtained as salt end product.

3. The method according to Claim 1, wherein the chlorine gas leaving the separator is transferred to the chlorine gas storage tank (290) and stored therein; and the gas exiting the chlorine gas storage tank reaches the chlorine cooling unit (300) where it is cooled and obtained as an end product in the liquid chlorine storage tank (400).

4. The method according to Claim 1 , characterized in that it comprises the process step of reacting the discharged chlorine gas with hydrogen to obtain hydrochloric acid.

5. The method according to Claim 1 , characterized in that it comprises the process step of reacting the chlorine gas with sodium hydroxide to obtain sodium hypochlorite.

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