A method for removing organic amines from a wet refined potash product

Abstract

The application discloses a method for removing organic amine in wet refined potassium, which is simultaneously completed in a drying process of the wet refined potassium, namely, hydrogen peroxide is added in the wet refined potassium material during transportation, hydrogen peroxide and ozone are added in a drying drum I, ozone is added in a drying drum II, and ozone is added in a gas flow entering a cyclone dust collector. The development of the application is suitable for the needs of the development of potassium chloride product technology, and provides technical support for high-value utilization of the potassium chloride product. The technical achievement has wide application prospect, provides good technical support and demonstration for promoting the technical progress of the production of industrial potassium chloride industry in China, and can improve the market competitiveness of the potassium salt product and provide technical support for a salt lake industrial base.

Description

Technical Field

[0001] This invention relates to the chemical industry, specifically to a method for removing organic amines from wet potassium chloride products. Background Technology

[0002] Among all salt lake mineral resources, potash has always been one of the products developed on a large scale and with a focus on key production. The Qarhan Salt Lake in Qinghai Province is one of the earliest developed salt lakes in my country, primarily producing potassium chloride. Currently, the annual potassium chloride production of Qarhan Salt Lake has reached the million-ton level, making it my country's largest potassium chloride production base.

[0003] Potassium chloride production in the Qarhan Salt Lake mainly involves three process routes: hot dissolution-cold crystallization, cold crystallization-positive flotation, and reverse flotation-cold crystallization. However, the hot dissolution-cold crystallization method has high energy consumption, severe equipment corrosion, and high investment costs. Therefore, potassium chloride production in the Qarhan Salt Lake mostly adopts the flotation process, which is also the most widely used production process in the world.

[0004] Direct flotation produces potassium-containing foam, while reverse flotation produces sodium-containing foam. Direct flotation has a low potassium recovery rate and produces finer particle sizes, but the process is simple, adaptable, and requires less investment. Potassium salt direct flotation collectors primarily use single amines with carbon chain lengths greater than 12, with octadecyl primary amines being the most prevalent and widely used. However, long-chain primary amines are difficult to degrade naturally, leading to long-term accumulation in salt lake areas, negatively impacting the fragile ecosystem and the production of high-quality salt lake chemical products. Reverse flotation-cold crystallization is currently a more advanced process for potassium salt production. Compared to cold decomposition-direct flotation, this method produces concentrates with better specifications, larger particle sizes, and stronger market competitiveness. Currently, industrially used reverse flotation collectors are mainly amides and morpholine reagents, with morpholine reagents being the most widely used. Morpholine collectors exhibit strong selectivity and collecting performance for sodium chloride, requiring no additional auxiliary reagents.

[0005] The flotation process consumes large quantities of amine-rich organic compounds annually, such as octadecylamine and dodecylmorpholine. Over years of production, these amines have diffused and accumulated, resulting in high amine content in the brine system and potash fertilizer products. This has directly or indirectly impacted the production process, the quality of potassium chloride, the production of other salt products, and the quality of downstream products. For example, the electrolysis of potassium chloride produces highly toxic, irritating, and explosive nitrogen trichloride. Therefore, organic amine pollution in potash salts has become a major pain point and challenge for the industry, urgently requiring a solution.

[0006] Existing technologies for removing organic amines from wastewater mostly employ oxidation methods, which often occur between gas and liquid or liquid and liquid phases. However, these methods cannot be easily replicated for treating organic amines in solid potassium salts. This is because organic amines in wastewater generally exist as free individual molecules or nanoparticles, resulting in high reactivity and rapid diffusion. Oxidation removal processes are readily implemented and fast. However, in potassium salts, organic amines form ionic bonds with chloride ions, anchoring the molecules firmly to the potassium salt crystal surface. This reduces their reactivity, meaning that oxidation removal requires the oxidant to diffuse to the crystal surface for the reaction to proceed, and the reaction rate is relatively slower. Furthermore, these anchored organic amine chains are more difficult to degrade the closer they are to the surface, meaning that lower concentrations of organic amines during degradation are more difficult to break down. On the other hand, actual measurements show that the concentration of organic amines in potassium salts can reach several hundred ppm, but is generally in the tens of ppm range, often higher than the several ppm concentration in wastewater.

[0007] Because potassium salts contain high levels of organic amines that are anchored on their surface, treating organic amines on solid potassium salts is more difficult and requires more sophisticated processes than treating organic amines in wastewater. Summary of the Invention

[0008] The problem to be solved by this invention is to provide a method for removing organic amines from wet potassium salt. The method uses oxidative coupling drying technology to simultaneously achieve low-cost and high-efficiency potassium salt drying and removal of organic amine impurities during the potassium salt production process, ultimately obtaining high-quality potassium salt products.

[0009] The wet potassium chloride produced in this invention can be from various existing conventional potassium chloride production processes, such as hot dissolution-cold crystallization, cold crystallization-positive flotation, or reverse flotation-cold crystallization. A common feature of these processes is that after obtaining wet potassium chloride through each production step, it must be dried to a moisture content ≤2% before packaging and sale (National Standard 6549-2011). While the national standard does not specify requirements for the organic amine content in potassium salt products, in production practice, organic amine impurities in the product cause significant inconvenience to downstream users. For example, during the electrolysis of potassium chloride, highly toxic, strongly irritating, and easily decomposed nitrogen trichloride is produced. Therefore, according to the requirements of the downstream electrolysis industry, the organic amine content in potassium salt products must not exceed 2 ppm.

[0010] The existing drying process mainly involves conveying the wet potassium chloride to a hopper via a belt conveyor, and then feeding it into the feeding end through a feeding pipe via a feeder in the hopper. Partially recovered exhaust gas and hot air from the heater outlet form a heat carrier, flowing parallel to the wet material into the first drying cylinder. As the cylinder rotates, the material moves to the lower end under gravity. During this forward movement within the cylinder, the wet material is dried. The material then enters the second drying cylinder for further drying and cooling, before being discharged at the outlet via a belt conveyor. Lifting plates are installed on the inner wall of the drying cylinder to increase the contact surface between the material and the airflow, thereby improving the drying rate and promoting material movement. The waste heat airflow within the drying cylinder is collected by a cyclone dust collector, which captures the material carried within the gas as the product.

[0011] The product for removing organic amines described in this invention can be produced using existing drying equipment without the need for new equipment investment, thus possessing industrial feasibility.

[0012] The main technical solutions of this invention are as follows: A method for removing organic amines from wet potassium chloride, wherein the method is performed simultaneously during the drying process of wet potassium chloride, specifically including the following steps: (1) Add hydrogen peroxide during the transfer of wet potassium concentrate; (2) Add hydrogen peroxide and ozone to the drying drum; (3) Add ozone to the second drying drum; (4) Add ozone to the airflow entering the cyclone dust collector.

[0013] In some embodiments, hydrogen peroxide is added in step (1) by atomization, and the residence time after mixing is greater than 2 hours. A better removal effect can be achieved if the residence time is greater than 2 hours. However, in order to improve the effect, the residence time can be preferably 2 to 24 hours.

[0014] In some embodiments, in step (1), the hydrogen peroxide added is 0.1%-1% of the weight of the potassium salt material. Within this range, the effect is similar, and from the perspective of saving costs, the concentration can also be 0.1%-0.5%; the added hydrogen peroxide concentration is 3%-30%, within this range, the effect is similar, and from the perspective of saving costs, the concentration can also be 3%-10%. Step (1) can activate the organic amines on the outside of the potassium salt and partially remove the organic amines.

[0015] In some embodiments, hydrogen peroxide and ozone are atomized and added together in step (2), and the addition position is at a position where the temperature of the first drying drum is below 150°C, preferably 50-150°C; in some instances, the residence time in the first drying drum is 30-60 minutes; preferably 40-50 minutes; if the temperature is too high, it will cause the catalyst to fail and reduce the catalytic effect; if the time is too short, the reaction will be incomplete, and the time process will affect the system's processing capacity.

[0016] In some embodiments, in step (2), the hydrogen peroxide added is 0.01%-0.1% by weight of the potassium salt material, preferably 0.01%-0.05%; the hydrogen peroxide concentration is 3%-30%, preferably 10%-3%; and the ozone concentration is 10-50 ppm, preferably 20-30 ppm. This step enables the generation of a large number of strongly oxidizing OH groups in the drying rotary kiln, removing most of the organic amines.

[0017] In some embodiments, the ozone concentration added in step (3) is 1-7 ppm, the temperature is 40-70°C, preferably 2-3 ppm, and the temperature is 50-60°C. The ozone is added at the inlet of the second drying drum, and the material remains in the drying drum for 20-60 minutes, preferably 30-40 minutes. This step enables further deep oxidation of residual organic matter in the material. Similarly, the treatment temperature and residence time affect the treatment effect and the total amount processed.

[0018] In some embodiments, the ozone concentration added in step (4) is 0.1-0.5 ppm, preferably 0.1-0.3 ppm; the temperature is 40-70°C, preferably 50-60°C. This step can further oxidize the potassium salt dust in the gas phase.

[0019] The beneficial effects of this invention are: (1) This invention employs an oxidation treatment coupled with drying technology, coupled with the existing potassium chloride production process. After simple modifications to the existing drying process, efficient and low-cost removal of organic amines from the product can be achieved. The final product contains less than 2 ppm of organic amines, or even none at all, meeting the requirements of downstream industries. The organic amines are ultimately oxidized into ammonia, carbon dioxide, water, and a small amount of nitrogen oxides, etc.

[0020] (2) The development of this invention meets the needs of potassium chloride product development technology and provides technical support for the high-value utilization of potassium chloride products in the future. This technological achievement has broad application prospects, provides good technical support and demonstration for promoting the technological progress of my country's potassium chloride production industry, can enhance the market competitiveness of potassium salt products, and provide technical guarantee for Qinghai to build a world-class salt lake industry base. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the oxidative coupling drying process.

[0023] Figure 2 The surface properties change before and after potassium salt treatment. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Unless otherwise specified, the wet potassium used in the following examples is wet potassium produced by Qinghai Salt Lake Industry Co., Ltd. using different existing conventional potassium chloride production processes such as hot dissolution-cold crystallization, cold crystallization-positive flotation, or reverse flotation-cold crystallization. The common feature of these processes is that after obtaining wet potassium through each production step, it must be dried so that the moisture content of the potassium chloride product is ≤2% before it can be packaged and sold.

[0026] The method used in this embodiment can utilize existing equipment in the potassium salt drying process, or add an oxidant inlet to existing equipment for adding oxidant.

[0027] Unless otherwise specified, the method for removing organic amines from wet potassium chloride in the following embodiments is performed simultaneously during the drying process of wet potassium chloride, and the specific process is as follows: Figure 1 As shown: hydrogen peroxide is added during the transfer of wet potassium salt materials; hydrogen peroxide and ozone are added in the first drying drum; ozone is added in the second drying drum; and ozone is added to the airflow entering the cyclone dust collector.

[0028] Example 1: Method for removing organic amines from wet potassium chloride Step (1): Hydrogen peroxide is added by atomization during the transfer of potassium chloride wet material. The weight of hydrogen peroxide added is 0.5% of the weight of potassium salt material, the concentration of hydrogen peroxide is 10%, and the residence time after mixing is 3 hours.

[0029] Step (2): In the drying drum 1, at a temperature of 120℃, hydrogen peroxide and ozone are added by atomization. The weight of hydrogen peroxide added is 0.02% of the weight of potassium salt material, the hydrogen peroxide concentration is 3%, the ozone concentration is 20ppm, and the residence time of the material in the drying drum 1 is 40 minutes.

[0030] Step (3): Add ozone to the feed inlet of the drying drum at a concentration of 2 ppm and a temperature of 60°C. The material stays in the drying drum for 30 minutes.

[0031] Step (4): Ozone is added to the airflow entering the cyclone dust collector at a concentration of 0.2 ppm and a temperature of 60°C, ultimately forming potassium chloride product after the removal of organic amines.

[0032] The potassium chloride obtained in this embodiment is more easily soluble in water because the organic amines on the surface of the solid salt are oxidized and removed (e.g., potassium chloride). Figure 2 As shown in the right figure, after removing the organic amine, potassium chloride (potassium chloride) sinks to the bottom of the water; however, if the product is dried directly without the addition of the oxidant as in Example 1, it appears oily and floats on the water surface due to the organic amine covering its surface (e.g., ...). Figure 2 (As shown in the left figure).

[0033] The organic amine content in the potassium salt products before and after oxidation treatment was determined by digestion-neutralization titration: the organic amine content in the obtained potassium salt decreased from 10.3 ppm before treatment to 0.7 ppm, which is qualified.

[0034] The processing time of this process is matched with the drying process, and the throughput remains unchanged. Extending step one allows production to proceed via intermediate stacking without affecting production or throughput. However, extending the processing time of other steps will lead to a decrease in throughput and an increase in cost. Following the basic method and steps of Example 1, the specific variations and effects of other examples and comparative examples are shown in Table 1: Table 1 Examples 2-5 and Comparative Examples 1-6 ;

[0035] illustrate: 1* The amount of hydrogen peroxide added refers to the percentage of the weight of hydrogen peroxide added to the weight of potassium salt.

[0036] 2. The residence time is also an important factor. If the residence time is less than that required by this patent, the treatment effect will be poor, while if the residence time is longer than that required by this patent, it will lead to a decrease in the system's processing capacity. The first stage can be processed by stacking materials, which increases the disposal space but does not affect the system's processing capacity.

Claims

1. A method for removing organic amines from wet potassium chloride, characterized in that, Includes the following steps: (1) Hydrogen peroxide is added during the transfer of wet potassium salt material. The hydrogen peroxide is added by atomization. After mixing, the residence time is greater than 2 hours. The weight of hydrogen peroxide added is 0.1%-1% of the weight of potassium salt material. (2) Add hydrogen peroxide and ozone to the first drying drum. The weight of hydrogen peroxide added is 0.01%-0.1% of the weight of potassium salt material, and the concentration of hydrogen peroxide is 3%-30%. The concentration of ozone is 10-50ppm. The residence time of the material in the first drying drum is 30-60 minutes. (3) Add ozone to the second drying drum. The ozone concentration is 1-7 ppm and the temperature is 40-70℃. The ozone is added at the feed inlet of the second drying drum, and the material stays in the drying drum for 20-60 minutes. (4) Ozone is added to the airflow entering the cyclone dust collector to further oxidize the potassium salt dust in the gas phase, and finally form potassium chloride product after removing organic amines.

2. The method for removing organic amines from wet potassium chloride according to claim 1, characterized in that, The stay can last from 2 to 24 hours.

3. The method for removing organic amines from wet potassium chloride according to claim 1, characterized in that, In step (1), the amount of hydrogen peroxide added is 0.1%-0.5% of the weight of the potassium salt material.

4. The method for removing organic amines from wet potassium chloride according to claim 1, characterized in that, The concentration of hydrogen peroxide added in step (1) is 3%-30%.

5. The method for removing organic amines from wet potassium chloride according to claim 4, characterized in that, The concentration of hydrogen peroxide added in step (1) is 3%-10%.

6. The method for removing organic amines from wet potassium chloride according to claim 1, characterized in that, In step (2), hydrogen peroxide and ozone are added together by atomization, and the addition position is at the position where the temperature of the first drying drum is below 150°C.

7. The method for removing organic amines from wet potassium chloride according to claim 6, characterized in that, In step (2), hydrogen peroxide and ozone are added together by atomization, and the addition position is at the position of the drying drum one where the temperature is 50-150℃.

8. The method for removing organic amines from wet potassium chloride according to claim 1, characterized in that, The ozone concentration added in step (4) is 0.1-0.5 ppm; the temperature is 40-70℃.

9. The method for removing organic amines from wet potassium chloride according to claim 8, characterized in that, The concentration of ozone added in step (4) is 0.1-0.3 ppm.

Images