CN110713196B - Preparation of low-sodium NaCl K by using melt recrystallization technology+Method for preparing salt - Google Patents

Abstract

The invention discloses a method for preparing low-sodium NaCl: K by using a melt recrystallization technology⁺Method of salt formation by subjecting K⁺The ions enter the NaCl crystal lattice to form usable NaCl K⁺A "new" KCl-doped NaCl crystalline compound is shown, resulting in NaCl K⁺The purity of the crystallized product can reach more than 99 percent, and the yield of the product is more than 80 percent; can reach the application of NaCl to K in the fields of high-tech industry, eating and the like⁺The purity requirement of the product; the method can obviously improve the large-scale industrial preparation of high-purity NaCl K⁺The production efficiency of the product is expected to have considerable economic and social benefits.

Description

Preparation of low-sodium NaCl K by using melt recrystallization technology+Method for preparing salt

Technical Field

The invention belongs to the field of NaCl salt production, and particularly relates to a method for producing high-purity NaCl K by using a melting recrystallization technology⁺A process for preparing low-sodium edible salt.

Background

Sodium chloride is a flavouring agent with important physiological functions for life on earth. The concentration of sodium ions in the blood is directly related to the regulation of safe levels of body fluids. However, a large number of epidemiological data and clinical studies have confirmed that excessive intake of sodium-induced Na⁺An excess of ions can lead to a number of adverse physiological reactions: a long-term high-salt diet can increase the blood pressure of people; additional studies have shown that: high salt diet can cause ventricular hypertrophy, ventricular contractile dysfunction, vascular endothelial dysfunction, and increased stiffness of blood vessel wall and ventricular wall independently of blood pressure level. High salt diets are one of the important risk factors for cardiovascular disease.

Epidemiological data and clinical studies have further demonstrated that dietary potassium supplementation can lower blood pressure in humans. Data of international cooperation research China at the end of 90 s in the 20 th century show that the daily salt intake of men and women in rural areas of China is about 14.3g and 12.3g respectively, and the daily intake of potassium ions is about 1.51g and 1.48g respectively. In the face of bad dietary structure of high sodium and low potassium in China, some experts and scholars propose advices of eating less salt, increasing the intake of fruits and vegetables in diet and eating potassium-containing low-sodium food aiming at limiting salt and supplementing potassium, thereby realizing the scheme of preventing and treating the occurrence and development of hypertension and cardiovascular diseases.

In fact, however, despite the provisions made in GB/T23789-2009 "low sodium food", low sodium food means food whose sodium content is significantly lower than that of the same food by reducing or removing the sodium in the food. The content of sodium specified by the existing low-sodium food standard in China is extremely low, the requirement on the content of sodium of common low-sodium food is not higher than 120mg/100 g, and the requirement on the content of sodium of very low-sodium food is not higher than 40mg/100g, but in daily life, vegetarian foods such as rice, vegetables and fruits eaten by people also contain certain sodium, and the content of sodium in animal foods such as fresh fish and fresh meat is generally 10-40 times of the content of sodium in the vegetarian foods. According to the Chinese food ingredient table, the flour (standard flour) contains 3.1mg/100g of sodium, the polished round-grained rice contains 2.7mg/100g of sodium, the tomato contains 9.7mg/100g of sodium, the Chinese cabbage contains 39.9mg/100g of sodium, and the carrot contains 120.7mg/100g of sodium. Therefore, it is difficult to meet this requirement in the actual production of food.

In addition, a large number of research studies show that the effect of reducing the blood pressure of patients with hypertension and common people can be achieved by mixing a certain proportion of KCl in the salt. At the same time, doping K⁺Use safety studies of ionic salts have also shown that subjects with normal renal function take up a maximum of 15.6 grams of potassium per day (corresponding to the potassium content of 120 grams of the low sodium salt). Thus, as shown in Table 1, although there is international lack of information on the amount of potassium required in humans, the target intake is suggested based on the actual intake of the population and considering the need for cardiovascular disease control without specifying the maximum intake. According to the table 1, when 10 g of low-sodium salt is taken every day, about 1g of potassium is ingested, which is 50% of the national target value and 20% of the American target value; if 20 g of potassium is taken every day, the intake of about 2 g of potassium just reaches the national target value and is 40 percent of the American target value. As can be seen, according to the comparison of the survey values that the daily salt intake of the rural men and women in China is about 14.3g and 12.3g respectively, the people who eat the low-sodium salt eat K⁺The amount of ions is also within a safe range. Therefore, it is recommended to select K⁺Low sodium salts of ions have become a common and imperative concern in preventing certain diseases. Some actively encouraged production and marketing of low sodium salt and lowThe policy of sodium food is also disputed: if the development cost is provided, tax reduction policies are implemented on low-sodium salt manufacturers to encourage enterprises to develop and produce safe, effective and good-taste low-sodium salt or seasoning; allowing the use of a processed food made with low sodium salt to mark a health mark; implementing low-sodium salt purchase price subsidy for hypertension patients; guarantee the low sodium salt to enter all subsidiary food retail stores, and the like.

China formulated the industry standard QB 2019-2005 'Low sodium salt' in 2005. The low sodium salt is classified into 3 types according to its composition in the standard. The I type comprises edible salt (refined salt), edible potassium chloride and edible magnesium sulfate (heptahydrate); the II type comprises edible salt (refined salt), edible potassium chloride and edible magnesium chloride (hexahydrate); group III consists of edible salt (refined salt) and edible potassium chloride. Meanwhile, the enterprise standards of the low sodium salt are many, but the components of the low sodium salt are similar to the industrial standards. In summary, the basis of the low sodium salt is to reduce the sodium chloride content of the common salt and to add a certain amount of potassium chloride, magnesium chloride hexahydrate or magnesium sulfate heptahydrate. At present, low sodium salt produced in China is widely sold in the market. However, the low-sodium salt products currently on the market still have some problems to be solved urgently:

1. homogeneity problem of NaCl and KCl mixture

NaCl and KCl are easy to absorb moisture, so that the powder is sticky and is not easy to disperse. The KCl is difficult to be uniformly distributed in the NaCl by adopting a mechanical mixing technical method.

2. Taste problems with low sodium salt

Because a certain amount of K is mixed in the low sodium salt⁺、Mg²⁺Ions, so that it stimulates the tongue's feeling and contains a bitter taste.

3. Long term storage and convenient use of low sodium salt

Containing K⁺、Mg²⁺The ionic low-sodium salt powder is more moisture-absorbing, so that the storage time of the ionic low-sodium salt powder is shortened, the ionic low-sodium salt powder is more likely to be agglomerated, and the storage and the use are inconvenient.

The melting recrystallization purification technical method does not need to add any solvent, is environment-friendly, has low equipment investment cost and canThe method has the advantages of low consumption, high product manufacturing efficiency and the like, and becomes a preferred process method for separating and purifying a plurality of low-melting-point materials. The development advantage is particularly obvious. Particularly, it is worth mentioning a method of purifying NaCl using a melt recrystallization technique [ a melt purification method of obtaining high purity NaCl crystals (ZL 200710160188. X)]The method has attracted more attention because of being capable of avoiding the defects of other methods. The invention provides a process for producing K by adopting a melting recrystallization technology⁺The doped low-sodium salt method well solves the problems caused by other methods for producing low-sodium salt, and can lay a solid foundation for large-scale popularization of high-quality low-sodium salt products.

Disclosure of Invention

The invention is based on K⁺The ions can effectively replace Na⁺The physical principle that ions enter NaCl crystal lattices provides a method for preparing, purifying and refining K at one time by using a melt crystallization method⁺Ion-doped NaCl K⁺A process for crystallizing the product. NaCl K obtained by the technical method⁺The purity of the crystallized product can reach more than 99 percent, and the yield of the product is more than 80 percent; can reach the application of NaCl to K in the fields of high-tech industry, eating and the like⁺The purity requirement of the product; the method can obviously improve the large-scale industrial preparation of high-purity NaCl K⁺The production efficiency of the product is expected to have considerable economic and social benefits.

The invention relates to a method for preparing low-sodium-salt NaCl-K by using a melt recrystallization technology⁺The method comprises the following steps:

1) firstly, heating mixed crystal salt powder containing food-grade KCl and NaCl from the ambient temperature to 500 ℃, keeping the temperature constant for 1h, then continuously heating to 800 ℃ and keeping the temperature constant for 0.5h to obtain a primary product, wherein the purpose of the process is to remove moisture, adsorbed gas and low-boiling-point organic matters in the raw materials;

2) and after continuously heating the primary product obtained in the step 1) to 950 ℃, immediately stopping heating and naturally cooling the primary product to 800 ℃. Repeating the above process twice to obtain secondary product, which can decompose and remove organic compounds such as protein and amino acids, and remove trace amount of organic compoundsNaF, KF and CaCl of₂And MgCl₂Impurities can completely float on the surface of the coarse crystal salt through a 'sweating' process;

3) continuously heating the secondary product obtained in the step 2) to 1350 ℃, keeping the temperature for 5min, and then stopping heating to naturally cool the secondary product to 800 ℃. Repeating the above process twice to obtain refined product, wherein the process makes NaF, KF and CaCl on the surface of the crude salt₂And MgCl₂The impurities can be completely removed by boiling or sublimation processes.

4) After the steps 1), 2) and 3) are finished, stopping heating, naturally cooling to room temperature, and taking out a product, namely the high-purity refined NaCl K⁺And (5) producing the product.

The invention has the advantages and positive effects that:

1. the technological method of the invention has no wastewater discharge, simple equipment, low production energy consumption and high efficiency, and the obtained NaCl K⁺The product purity can reach more than 99 percent, and the product yield is more than 80 percent. The method can obviously improve the large-scale industrial preparation of high-purity NaCl K⁺The production efficiency of the product is estimated to be considerable in economic benefit and social benefit.

2. The melting recrystallization process adopted by the process of the invention is characterized in that: through the process of heating up and sweating according to the steps, impurities with relatively low melting points in the raw material coarse crystal NaCl are firstly exposed and completely gathered on the surface of the coarse crystal salt, and then the impurities are separated out by means of the processes of boiling and gasification, so that the aim of purifying the coarse crystal is fulfilled.

3. Low sodium edible salt products processed by the process of the invention, in which traces of water and organic matter and Li are present⁺、 Ca^{2 +}、Mg²⁺And the molecules and ions which influence the taste of the food are completely separated, and the fresh and salty taste effects of the natural NaCl are returned. It can be used for cooking dishes and soup, and can make dishes and soup exhibit refreshing, fresh and salty taste even without adding deliciousness seasoning agent.

4. The method is such that K⁺The ions enter the NaCl crystal lattice to form usable NaCl K⁺The expressed 'new' KCl doped NaCl crystalline compound not only causes the change of the local structure of the material to reduce the moisture absorption of the low-sodium salt, but also causes the low-sodium salt not to be easy to agglomerate, thereby bringing convenience for packaging and long-term storage and use; furthermore, also make K⁺The ions can be uniformly distributed in the crystal.

5. Theoretical studies show that a large amount of 'impurity' K⁺Ion substituted Na⁺The ion's protons create a large number of crystal lattice vacancies in the NaCl crystal, which are physically referred to as "color centers" of energy centers. And has K⁺Ions, crystal lattice vacancies and O^2—The anion composition color center can not only endow the NaCl crystal with optical activity (shown in figure 1), but also endow the crystal material with biological functions: in fact, it has long been known that negative oxygen ions have the functions of promoting intestinal motility, relieving constipation and accelerating the metabolism of human body.

Drawings

FIG. 1 shows NaCl 11% K⁺And a photoluminescence spectrogram of the natural NaCl salt crystal and the solution recrystallized NaCl salt crystal.

Detailed Description

The swelling NaCl K of the present invention is explained in detail by the following specific examples⁺The preparation process of the crystalline material comprises the following specific implementation modes:

1) selecting 8kg of high-purity powder salt with the NaCl content of more than 99.5 percent and 2kg of KCl salt powder with the NaCl content of more than 99.5 percent, putting the high-purity powder salt and the KCl salt powder into a stirring mixer, fully mixing, putting the mixture into a 99 porcelain alumina box body with proper size, and moving the box body into a high-temperature furnace;

2) raising the temperature of the furnace to 500 ℃ within 30min, keeping the temperature for 1h, then continuously and rapidly raising the temperature to 800 ℃ and keeping the temperature for 0.5 h;

3) then the temperature is continuously raised to 950 ℃ within 20min, the heating is immediately stopped and the temperature is naturally reduced to 800 ℃. This process was repeated 2 times.

4) Rapidly heating from 800 ℃ to 1350 ℃, keeping the temperature for 5min, then naturally cooling to 800 ℃, then heating to 1350 ℃ and keeping the temperature for 5 min. This process was repeated 2 times;

5) and naturally cooling to room temperature from 800 ℃. The product is taken out and weighed, and the yield is calculated,obtaining high-purity NaCl K⁺The crystallized product is about 8 kg.

6)NaCl:K⁺And (3) testing the purity of the crystallized product: according to the national salt product quality supervision and inspection center [ No.20191567)]Aiming at the detection report of the sample to be detected, K products containing KCl 11% and other impurities with contents far higher than the standard content are refined by using the process technical method. See table 2 below for specific test items.

TABLE 1 daily intake target values for low sodium salt

TABLE 2 NaCl: K⁺Purity test result of crystallized product

FIG. 1 shows NaCl 11% K⁺Natural NaCl salt crystals and solution recrystallized NaCl salt crystals photoluminescence spectra. The excitation wavelength is 630nm and the emission wavelength is in the near infrared spectral interval between 850nm and 1000 nm.

From three spectra can be seen: natural and solution recrystallized salt crystals see only background noise, while only the molten recrystallized salt crystals have a distinct luminescence signature, which can indicate the presence of optically active centers within the crystal.

Claims (1)

1. Preparation of low sodium salt NaCl K by using melting recrystallization technology⁺The method of (2), characterized by: the method comprises the following steps:

1) firstly, heating mixed crystal salt powder containing food-grade KCl and NaCl from the ambient temperature to 500 ℃, keeping the temperature constant for 1h, and then continuously heating to 800 ℃ and keeping the temperature constant for 0.5h to obtain a primary product;

2) continuing to heat the primary product obtained in the step 1) to 950 ℃, immediately stopping heating, naturally cooling to 800 ℃, and repeating the process twice to obtain a secondary product;

3) continuously heating the secondary product obtained in the step 2) to 1350 ℃, keeping the temperature for 5min, then stopping heating, naturally cooling to 800 ℃, and repeating the process twice to obtain a refined product;

4) after the steps 1), 2) and 3) are finished, stopping heating, naturally cooling to room temperature, and taking out a product, namely the high-purity refined NaCl K⁺And (5) producing the product.

Images