阅读说明：本技术 一种利用复分解法生产熔盐级硝酸钾的工艺和系统 (Process and system for producing molten salt-grade potassium nitrate by utilizing double decomposition method ) 是由 邱刚 孙立辉 王俊峰 高斌 刘国洪 于 2020-07-31 设计创作，主要内容包括：本发明公开了一种利用复分解法生产熔盐级硝酸钾的工艺和系统,包括以下步骤：向合成釜中投入氧化镁,然后再滴加硝酸进行搅拌；向合成釜中加入氯化钾进行复分解合成,生成硝酸钾溶液并进行压滤；将压滤之后的硝酸钾溶液送至结晶槽降温冷却结晶,之后进行水洗除去氯根；把硝酸钾结晶体送至水洗釜水洗并送至振动流化床烘干,制得硝酸钾产品出售；把含有硝酸钾及氯化镁的母液送到硝酸钾冷冻盐水储槽降温分离；将分离出的硝酸钾进行重溶、结晶、洗涤、离心后,制得硝酸钾产品出售；将分离出的含有六水氯化镁的母液进入氯化镁储槽外卖。本发明具备通过对工艺中产生的母液及水洗液进行重复利用,增加硝酸的利用率,进而降低硝酸钾的生产成本的优点。(The invention discloses a process and a system for producing molten salt-grade potassium nitrate by using a double decomposition method, which comprises the following steps: adding magnesium oxide into the synthesis kettle, and then dropwise adding nitric acid to stir; adding potassium chloride into the synthesis kettle for double decomposition synthesis to generate a potassium nitrate solution and performing filter pressing; sending the potassium nitrate solution after filter pressing to a crystallization tank for cooling, cooling and crystallizing, and then washing with water to remove chlorine radicals; sending the potassium nitrate crystal to a washing kettle for washing and sending to a vibrating fluidized bed for drying to obtain a potassium nitrate product for sale; mother liquor containing potassium nitrate and magnesium chloride is sent to a potassium nitrate frozen brine storage tank for cooling and separation; re-dissolving, crystallizing, washing and centrifuging the separated potassium nitrate to obtain a potassium nitrate product for sale; and (4) putting the separated mother liquor containing the magnesium chloride hexahydrate into a magnesium chloride storage tank for selling. The method has the advantages that the utilization rate of the nitric acid is increased by recycling the mother liquor and the rinsing liquor generated in the process, and the production cost of the potassium nitrate is further reduced.)

1. A process and a system for producing molten salt-grade potassium nitrate by using a double decomposition method are characterized by comprising the following steps:

s1, metering the washing mother liquor generated in the step S4 by a mother liquor metering tank, putting the mother liquor into a potassium nitrate synthesis kettle, pumping nitric acid into the metering tank, adding magnesium oxide into the synthesis kettle, and then dropwise adding the nitric acid and stirring;

s2, slowly adding potassium chloride into the synthesis kettle to perform double decomposition synthesis to generate a potassium nitrate solution;

s3, filtering the potassium nitrate solution through a filter press to remove impurities such as silicon dioxide, metal and the like;

s4, pumping the potassium nitrate solution after filter pressing to a crystallization tank by a pump for cooling, pumping the potassium nitrate solution into an artificial tank after cooling to a certain temperature, returning the mother solution to a natural mother solution tank, adding a certain amount of desalted water or washing mother solution into the artificial tank, then starting a vacuum pump for suction filtration, washing to remove chlorine radicals, and returning the washing mother solution to a washing tank;

s5, conveying the potassium nitrate crystal after the mother liquor is subjected to suction filtration in the S4 to a water washing kettle, washing the potassium nitrate crystal again, then centrifuging the potassium nitrate crystal in a centrifugal machine, conveying the centrifuged potassium nitrate crystal to a vibrating fluidized bed through a spiral conveyor, and drying the potassium nitrate crystal to obtain a potassium nitrate product for sale;

s6, pumping the mother liquor containing potassium nitrate and magnesium chloride in the S4 from the mother liquor tank to a potassium nitrate frozen brine storage tank, cooling to-11 ℃, and separating potassium nitrate and magnesium chloride liquor;

s7, re-dissolving, crystallizing, washing and centrifuging the potassium nitrate separated in the S6 to obtain a potassium nitrate product for sale;

s8, putting the mother liquor containing the magnesium chloride hexahydrate separated in the S6 into a magnesium chloride storage tank for selling.

2. The process and the system for producing the molten salt-grade potassium nitrate by the double decomposition method according to claim 1 are characterized in that: and (5) stirring for 1.5h in S1, and controlling the pH value to 2-3 after acid dripping is finished.

3. The process and the system for producing the molten salt-grade potassium nitrate by the double decomposition method according to claim 1 are characterized in that: in S2, the pH value in the reaction kettle is 4-5, and the reaction temperature is 80-100 ℃.

4. The process and the system for producing the molten salt-grade potassium nitrate by the double decomposition method according to claim 1 are characterized in that: in S5, the inlet air temperature of the drying fluidized bed is 170-200 ℃, the outlet air temperature is 60-120 ℃, the opening of the inlet valve of the cooling fluidized bed is 1/5, the temperature of a product at a material outlet is controlled by an induced draft fan through frequency conversion to be 30-60 ℃, the moisture of a dried finished product is less than or equal to 0.3 percent, and the chloride (calculated by CL < - >) is less than or equal to 0.1 percent.

5. The process and the system for producing the molten salt-grade potassium nitrate by the double decomposition method according to claim 1 are characterized in that: in S3, when the filter press is used for filtering, the pressure at the outlet of the self-priming pump is 0.4-0.6MPa, the temperature of the filtered material is 80-100 ℃, and the pressure of the filter press is 20-25 MPa.

6. The process and the system for producing the molten salt-grade potassium nitrate by the double decomposition method according to claim 1 are characterized in that: the reaction equations in S1 and S2 are 2HNO3+ MgO +5H20 → Mg (NO3) 2.6H 20 respectively; 2KCl + Mg (NO3) 2.6H 20 → 2KNO3+ MgCl 2.6H 20.

Technical Field

The invention relates to the technical field of potassium nitrate preparation, in particular to a process and a system for producing molten salt-grade potassium nitrate by utilizing a double decomposition method.

Background

The potassium nitrate is also called saltpeter, saltpeter and potassium nitrate, has a chemical formula of KNO3, is a chlorine-free high-quality fertilizer and an inorganic chemical product, and has wide application in agriculture and industry. In agriculture, potassium nitrate is used as a high-quality chlorine-free potassium fertilizer, is particularly suitable for tobacco, coffee, tea, flowers and other dry land economic crops which are forbidden to be subjected to chlorine and potassium preference, and is composed of effective substances, so that the soil quality cannot be changed or the crops cannot be affected after the potassium nitrate is applied; in industry, potassium nitrate is mainly used for manufacturing gunpowder, metal welding aids, synthetic ammonia catalysts, glass products, ceramics and the like; the product can be used as color former and antiseptic for meat products; in the aspect of medicine, the compound can also be used as a diuretic, a freshener and the production of penicillin potassium salt, rifampicin and other medicines. In addition, industrial-grade potassium nitrate also shows a good development prospect in the aspect of glass manufacturing in recent years, potassium nitrate is used for manufacturing optical glass in the United states in the past, a plurality of glass manufacturers also start to adopt potassium nitrate to manufacture high-end chemically strengthened glass such as mobile phone screens and flat computers successively, the development space of potassium nitrate is larger and larger along with the continuous and stable development of Chinese economy, and the market demand is continuously increased. At present, the main processes for producing potassium nitrate at home and abroad include a conversion method, an ion exchange method, a solvent extraction method and a double decomposition method, wherein the double decomposition method is the main process for producing potassium nitrate in China. However, the existing process for preparing potassium nitrate by the double decomposition method has the disadvantages of long process flow, complex operation, high energy consumption, weak raw material adaptability and high product production cost.

Disclosure of Invention

The invention aims to provide a process and a system for producing molten salt-grade potassium nitrate by using a double decomposition method, which have the advantages of increasing the utilization rate of nitric acid and further reducing the production cost of potassium nitrate by recycling mother liquor and washing liquor generated in the process, and solve the problems of long process flow, complex operation, high energy consumption, weak raw material adaptability and high product production cost of the existing double decomposition method for preparing potassium nitrate. In order to achieve the purpose, the invention provides the following technical scheme: a process and a system for producing molten salt-grade potassium nitrate by using a double decomposition method comprise the following steps:

s1, metering the washing mother liquor generated in the step S4 by a mother liquor metering tank, putting the mother liquor into a potassium nitrate synthesis kettle, pumping nitric acid into the metering tank, adding magnesium oxide into the synthesis kettle, and then dropwise adding the nitric acid and stirring;

s2, slowly adding potassium chloride into the synthesis kettle to perform double decomposition synthesis to generate a potassium nitrate solution;

s3, filtering the potassium nitrate solution through a filter press to remove impurities such as silicon dioxide, metal and the like;

s4, pumping the potassium nitrate solution after filter pressing to a crystallization tank by a pump for cooling, pumping the potassium nitrate solution into an artificial tank after cooling to a certain temperature, returning the mother solution to a natural mother solution tank, adding a certain amount of desalted water or washing mother solution into the artificial tank, then starting a vacuum pump for suction filtration, washing to remove chlorine radicals, and returning the washing mother solution to a washing tank;

s5, conveying the potassium nitrate crystal after the mother liquor is subjected to suction filtration in the S4 to a water washing kettle, washing the potassium nitrate crystal again, then centrifuging the potassium nitrate crystal in a centrifugal machine, conveying the centrifuged potassium nitrate crystal to a vibrating fluidized bed through a spiral conveyor, and drying the potassium nitrate crystal to obtain a potassium nitrate product for sale;

s6, pumping the mother liquor containing potassium nitrate and magnesium chloride in the S4 from the mother liquor tank to a potassium nitrate frozen brine storage tank, cooling to-11 ℃, and separating potassium nitrate and magnesium chloride liquor;

s7, re-dissolving, crystallizing, washing and centrifuging the potassium nitrate separated in the S6 to obtain a potassium nitrate product for sale;

s8, putting the mother liquor containing the magnesium chloride hexahydrate separated in the S6 into a magnesium chloride storage tank for selling.

Preferably, the stirring time in S1 is 1.5h, and the pH is controlled to be 2-3 after the acid dripping is finished.

Preferably, the pH value in the reaction kettle in S2 is 4-5, and the reaction temperature is 80-100 ℃.

Preferably, the air inlet temperature of the drying fluidized bed in the S5 is 170-200 ℃, the air outlet temperature is 60-120 ℃, the opening of the air inlet valve of the cooling fluidized bed is 1/5, the induced draft fan controls the temperature of a material outlet product by frequency conversion to be 30-60 ℃, the moisture of a dried product is less than or equal to 0.3 percent, and the chloride (calculated by CL < - >) is less than or equal to 0.1 percent.

Preferably, in S3, the pressure at the outlet of a self-priming pump is 0.4-0.6MPa, the temperature of the filtered material is 80-100 ℃, and the pressure of the filter press is 20-25 MPa.

Preferably, the reaction equations in S1 and S2 are 2HNO3+ MgO +5H20 → Mg (NO3) 2.6H 20; 2KCl + Mg (NO3) 2.6H 20 → 2KNO3+ MgCl 2.6H 20.

Compared with the prior art, the invention has the beneficial effects that: mother liquor and rinsing liquor generated in the reaction process are recycled and fully utilized, so that the utilization rate of nitric acid is increased, the preparation rate of potassium nitrate is increased, and the production cost of potassium nitrate is reduced.

Drawings

FIG. 1 is a schematic flow chart of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the present invention, it should be noted that the terms "upper", "lower", "inner", "outer", "front", "rear", "both ends", "one end", "the other end", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "disposed," "connected," and the like are to be construed broadly, such as "connected," which may be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

Referring to fig. 1, three embodiments of the present invention are provided: