CN112456533B - Method for producing high-purity anhydrous calcium chloride with limestone as raw material - Google Patents

Abstract

The invention belongs to the technical field of mineral processing, and in particular relates to a method for producing high-purity anhydrous calcium chloride by using limestone as a raw material. Using limestone ore as raw material, high-purity anhydrous calcium chloride is prepared through slurry preparation, leaching reaction, precipitation reaction and post-treatment. In the method for producing high-purity anhydrous calcium chloride using limestone as a raw material, the limestone ore can be leached out of calcium ions through chemical reaction without grinding and calcining. During the leaching process, since the generated Fe(OH) ₃ itself has a very strong adsorption capacity, it can adsorb and remove the impurity ions in the leaching solution. In order to further reduce the content of magnesium ions in the reaction system, by adding CaO to the reaction system, magnesium ions are converted into magnesium hydroxide colloids, and while removing magnesium elements, the impurity ions in the reaction system are further adsorbed to obtain highly purified calcium chloride solution.

Description

Method for producing high-purity anhydrous calcium chloride with limestone as raw material

technical field

The invention belongs to the technical field of mineral processing, and in particular relates to a method for producing high-purity anhydrous calcium chloride by using limestone as a raw material.

Background technique

Anhydrous calcium chloride has an extremely wide range of uses in industrial and agricultural production and daily life. For example, it is a widely used chemical desiccant because of its effective dehumidification and moisture-proof effect, which can prevent electronic equipment, chemical reagents, medicines and food from being damaged due to moisture during transportation, storage or use. Or metamorphism has important applications; in the chemical industry, it is used to manufacture metal calcium and various calcium salts. It is used as an antifreeze in the construction industry to accelerate concrete hardening and increase the cold resistance of construction mortars. Used as a medium for haploid breeding in the microbial industry. In analytical chemistry, it is used to determine the carbon content of iron and steel, whole blood glucose, serum inorganic phosphorus and serum alkaline phosphatase activity. In addition, it is also used as a fire retardant for fabrics, an anti-fogging agent for seaports, a dust collector for road surfaces and a water treatment agent for boilers, and it can also prevent coal dust and prevent the generation of explosive coal dust in mines. In the food industry, it is used as a chelating agent and a curing agent, such as a coagulant for canned food and soy products.

At present, the process methods for producing calcium chloride mainly include soda ash waste liquid recovery method, potassium chlorate waste liquid recovery method and hydrochloric acid limestone method. Among them, the hydrochloric acid limestone method is widely used, but the acid leaching method is used for preparation, which increases the production cost and requires high reaction equipment.

my country is extremely rich in limestone mineral resources. Seven or eight thousand cement limestone mines have been discovered nationwide, of which 1,286 have proven reserves, with a total of 54.2 billion tons of ore reserves. Limestone minerals are abundant, but the degree of development and utilization of limestone is relatively low. In my country, the main use of limestone is to produce cement and fired lime. Because limestone contains impurity elements, it cannot be separated by a simple process, and the use of a complex process leads to an increase in production costs. How to develop and utilize limestone under the premise of low cost has become a difficult problem.

In the process of limestone development and utilization, how to remove impurities in limestone and obtain calcium efficiently has become the bottleneck restricting the development and utilization of limestone. One of the main uses of limestone is to burn cement. In the process of burning cement, the content of MgO in limestone is required to be less than or equal to 3%, and limestone exceeding 3% cannot be used as cement raw material. Limestone calcination to produce lime not only consumes high energy, but also has the problem of how to recover high-temperature carbon dioxide, resulting in increased production costs. The use of acid leaching to extract calcium in limestone not only increases the cost significantly, but also produces a reaction acid solution that requires further follow-up treatment. At the same time, corrosion-resistant reaction equipment is required, and the input cost in industrial production is too high, which is not conducive to industrial production and application.

It can be seen that looking for a leaching process that does not require calcination and can directly leaching magnesium and calcium elements in limestone ore without acid participating in the reaction has become a key to the future development of the limestone industry.

SUMMARY OF THE INVENTION

The purpose of this invention is to: provide a kind of method that takes limestone as raw material to produce high-purity anhydrous calcium chloride. The method effectively reduces the cost of leaching valuable elements in limestone and simplifies production equipment.

The method for producing high-purity anhydrous calcium chloride with limestone as a raw material according to the present invention comprises the following steps:

(1) Preparation of slurry

The limestone ore is crushed and washed with water, and then water is added to make a slurry;

(2) leaching reaction

Add one of ferric chloride anhydrous or ferric chloride hexahydrate to the prepared slurry, and then transfer it to a stirring tank for leaching reaction;

(3) Precipitation reaction

After the reaction finishes, the obtained reaction mass is subjected to pressure filtration, and the gained filtrate is sent to the reaction tank, and the content of ^Mg in the filtrate is measured, and according to the content of ^Mg , in the filtrate, high-purity CaO is added to carry out precipitation reaction;

(4) Post-processing

After the reaction is completed, the obtained reaction material is subjected to pressure filtration, and the generated filtrate is evaporated to obtain calcium chloride dihydrate, and the calcium chloride dihydrate is dried to obtain high-purity anhydrous calcium chloride.

in:

The chemical composition of the limestone ore described in step (1) is CaO 35-55.7%, SiO ₂ 0.07-6%, MgO 0.5-15%, Al ₂ O ₃ 0.4-5%, loss on ignition 22-40%, The remainder is impurities.

In step (1), the limestone ore is crushed to a particle size of ≤3mm, and then washed with water to remove impurities such as sediment.

The mass of limestone in the slurry described in step (1): the mass of water=1:1～1:50.

The addition of the anhydrous ferric chloride or ferric chloride hexahydrate described in the step (2) is: the mole number of ^Fe in the reaction system: the mole number of Ca ²⁺ +Mg ²⁺ in the limestone=2:3 ~6.

In step (2), the volume of the slurry after adding anhydrous ferric chloride or ferric chloride hexahydrate is 60% to 80% of the volume of the stirring tank.

The reaction temperature described in the step (2) is room temperature, the reaction time is 0.5～3h, and the stirring speed is 120r/min～1000r/min.

In step (3), the filter cake obtained by pressure filtration is washed for many times, and dried at 120°C to 150°C, and the filter cake is subjected to subsequent separation treatment.

In the high-purity calcium oxide described in step (3), CaO is 98.5-99.8%, and SiO ₂ is 0-0.5%; the amount of Mg ²⁺ in the filtrate: the amount of high-purity calcium oxide=1:1 ~1.5.

The reaction temperature described in the step (3) is room temperature, the reaction time is 0.5～3h, and the stirring speed is 150r/min～1000r/min.

The filter cake obtained by the pressure filtration described in the step (4) is washed and dried and stacked with the filter cake obtained in the step (3) for subsequent separation treatment.

In step (4), a three-effect evaporator is used for efficient evaporation, the evaporation capacity is 100L/h～60t/h, and the evaporation temperature is 40～100°C.

As described in step (4), the calcium chloride dihydrate is sent to a high-temperature furnace, and heated for 1 h to 2 h at 300 to 360° C. for drying.

The invention takes limestone ore as the research object, removes magnesium and other impurity elements in limestone by selective leaching method and precipitation method, and obtains anhydrous calcium chloride product. The reaction that happens is:

3MgCO ₃ +2FeCl ₃ +3H ₂ O=2Fe(OH) ₃ ↓+3MgCl ₂ +3CO ₂ ↑

3CaCO ₃ +2FeCl ₃ +3H ₂ O=2Fe(OH) ₃ ↓+3CaCl ₂ +3CO ₂ ↑

CaO+H ₂ O=Ca(OH) ₂

MgCl ₂ +Ca(OH) ₂ =Mg(OH) ₂ ↓+CaCl ₂

CaCl ₂ ·2H ₂ O=CaCl ₂ +2H ₂ O.

As a preferred technical scheme, the method for producing high-purity anhydrous calcium chloride with limestone as a raw material of the present invention is made up of the following steps:

(1) crushing the limestone ore to a particle size less than 3mm, then washing the crushed ore to remove impurities such as sediment therein;

(2) The crushed ore is made into slurry, wherein m (limestone): m (water)=1:1～1:50;

(3) Add anhydrous ferric chloride or ferric chloride hexahydrate to the configured slurry, and the addition amount is: n (the moles of Ca ²⁺ +Mg ²⁺ in the limestone): n (Fe ³ in the reaction system ⁺ moles) = 3:2;

(4) The slurry added with anhydrous ferric chloride or ferric chloride hexahydrate is moved to the stirring tank, and the slurry filling amount is 60% to 80% of the volume of the stirring tank;

(5) The reaction is carried out at room temperature, the reaction time is 0.5～3h, the leaching reaction is carried out under this reaction condition, and the stirring speed is 120r/min～1000r/min.

(6) After the reaction is completed, the reaction material is sent to a filter press for pressure filtration, the filter cake is washed multiple times, and dried at 120°C to 150°C, and the filter cake is subjected to subsequent separation treatment.

(7) the filtrate produced by pressure filtration in step (6) is pumped to the reaction tank, the content of ^Mg in the filtrate is measured, according to the content of ^Mg , in the filtrate, high-purity CaO is added, and the addition is: n (Mg ²⁺ ):n(CaO)=1:1. The reaction is carried out at room temperature, and the reaction time is 0.5 to 3 h. The reaction is carried out under this reaction condition, and the stirring speed is 150 r/min to 1000 r/min.

(8) After the reaction is completed, the reaction material in step (7) is sent to a filter press for pressure filtration. After the filter cake is washed and dried, it is stacked with the filter cake in step (6) for subsequent separation treatment. .

(9) efficiently evaporate the filtrate generated in the step (8) to obtain a calcium chloride dihydrate product, further send the calcium chloride dihydrate to a high-temperature furnace, and continue to heat at 360° C. for 1h to 2h to obtain a high-purity calcium chloride dihydrate product. Water calcium chloride products.

Compared with the prior art, the present invention has the following beneficial effects:

(1) the method for producing high-purity anhydrous calcium chloride with limestone as raw material of the present invention does not need to carry out high-temperature calcination and decomposition to limestone, and the reaction process has no acid to participate in the reaction, effectively reducing the leaching of valuable elements in the limestone cost and simplify the production equipment.

(2) The method for producing high-purity anhydrous calcium chloride with limestone as a raw material according to the present invention can not only reduce the environmental pollution caused by high-temperature calcined limestone, but also increase the economic benefit of enterprises, be beneficial to environmental protection, and have broad development prospects.

(3) The method for producing high-purity anhydrous calcium chloride with limestone as a raw material according to the present invention, the limestone ore can leach calcium ions by chemical reaction under the conditions of no grinding and no calcination. During the leaching process, since the generated Fe(OH) ₃ itself has a very strong adsorption capacity, it can adsorb and remove the impurity ions in the leaching solution. In order to further reduce the content of magnesium ions in the reaction system, by adding CaO to the reaction system, magnesium ions are converted into magnesium hydroxide colloids, and while removing magnesium elements, the impurity ions in the reaction system are further adsorbed to obtain highly purified calcium chloride solution.

(4) The method for producing high-purity anhydrous calcium chloride using limestone as a raw material of the present invention has high product yield, low cost, no environmental pollution, high efficiency, green environmental protection, and is easy to realize industrialized production. Potential advantages of limestone ore utilization technology.

Description of drawings

Fig. 1 is the process flow diagram of producing high-purity anhydrous calcium chloride with limestone as raw material;

Fig. 2 is the SEM image of the calcium chloride anhydrous prepared by embodiment 2;

3 is the XRD pattern of the anhydrous calcium chloride prepared in Example 2.

Detailed ways

The present invention will be further described below in conjunction with the embodiments.

Example 1

The chemical composition of the limestone ore used in Example 1 is CaO 35%, SiO ₂ 5%, MgO 12%, Al ₂ O ₃ 2%, loss on ignition 22%, and the balance is impurities.

The method for producing high-purity anhydrous calcium chloride with limestone as a raw material described in the present embodiment 1 is made up of the following steps:

The limestone ore is crushed to a particle size of ≤3mm, and then the crushed ore is washed with water to remove impurities such as sediment; the crushed ore is made into a slurry, wherein m (limestone): m (water) = 1:1; Add anhydrous ferric chloride to the configured slurry, and the addition amount is: n (the number of moles of Ca ²⁺ +Mg ²⁺ in the limestone): n (the number of moles of Fe ³⁺ in the reaction system)=3:2; The slurry added with anhydrous ferric chloride was moved to the stirring tank, and the filling amount of the slurry was 80% of the volume of the stirring tank; the reaction was carried out at room temperature, and the reaction time was 3h. Under this reaction condition, the leaching reaction was carried out, and the stirring speed was is 1000r/min. After the reaction, the reaction material was sent to a filter press for pressure filtration, the filter cake was washed several times, and dried at 150° C., and the filter cake was subjected to subsequent separation treatment. The filtrate produced by the pressure filtration is pumped to the reaction tank, and the content of ^Mg in the filtrate is measured. According to the content of ^Mg , high-purity CaO is added to the filtrate. In the high-purity calcium oxide, CaO 99.0%, SiO ₂ 0.3%; the addition amount is: n(Mg ²⁺ ):n(CaO)=1:1. The reaction was carried out at room temperature, the reaction time was 3h, and the stirring speed was 150r/min. After the reaction is completed, the reaction material is sent to a filter press for pressure filtration, and the filter cake is washed and dried, and then sent to the filter cake stack for subsequent separation treatment. The generated filtrate is efficiently evaporated by a three-effect evaporator, the evaporation capacity is 100L/h～60t/h, the first-effect evaporation temperature is 81°C, the second-effect evaporation temperature is 66°C, and the third-effect evaporation temperature is 51°C to obtain calcium chloride dihydrate. The product, calcium chloride dihydrate is further sent to a high-temperature furnace, and continues to be heated at 360 ° C for 1 hour to obtain high-purity anhydrous calcium chloride.

Example 2

The chemical composition of the limestone ore used in Example 2 is CaO 41%, SiO ₂ 3%, MgO 9%, Al ₂ O ₃ 1.8%, loss on ignition 32%, and the balance is impurities.

The method for producing high-purity anhydrous calcium chloride with limestone as a raw material described in the present embodiment 2 is made up of the following steps:

The limestone ore is crushed to a particle size of less than 3mm, and then the crushed ore is washed with water to remove impurities such as sediment; the crushed ore is made into a slurry, wherein m (limestone): m (water)=1:20; Add ferric chloride hexahydrate to the configured slurry, and the addition amount is: n (the number of moles of Ca ²⁺ +Mg ²⁺ in the limestone): n (the number of moles of Fe ³⁺ in the reaction system)=4:2; The slurry added with ferric chloride hexahydrate was moved to the stirring tank, and the filling amount of the slurry was 70% of the volume of the stirring tank; the reaction was carried out at room temperature, and the reaction time was 1.5h. Under this reaction condition, the leaching reaction was carried out, and the stirring The rotational speed is 500r/min. After the reaction, the reaction material was sent to a filter press for pressure filtration, the filter cake was washed several times, and dried at 130° C., and the filter cake was subjected to subsequent separation treatment. The filtrate produced by pressure filtration is pumped to the reaction tank, the content of Mg ²⁺ in the filtrate is measured, and high-purity CaO is added to the filtrate according to the content of Mg ²⁺ . ₂ 0.3%; the addition amount is: n(Mg ²⁺ ):n(CaO)=1:1.2. The reaction was carried out at room temperature, the reaction time was 2h, and the stirring speed was 600r/min. After the reaction is completed, the reaction material is sent to a filter press for pressure filtration, and the filter cake is washed and dried, and then sent to the filter cake stack for subsequent separation treatment. The resulting filtrate is efficiently evaporated by a three-effect evaporator, the evaporation capacity is 100L/h～60t/h, the first-effect evaporation temperature is 85°C, the second-effect evaporation temperature is 70°C, and the third-effect evaporation temperature is 57°C to obtain calcium chloride dihydrate. The product, calcium chloride dihydrate is further sent to a high-temperature furnace, and continues to be heated at 330 ° C for 1.5 hours to obtain high-purity anhydrous calcium chloride.

Example 3

The chemical composition of the limestone ore used in Example 3 is CaO 54%, SiO ₂ 0.2%, MgO 0.5%, Al ₂ O ₃ 0.4%, loss on ignition 40%, and the balance is impurities.

The method for producing high-purity anhydrous calcium chloride with limestone as a raw material described in the present embodiment 3 is made up of the following steps:

The limestone ore is crushed to a particle size of less than 3 mm, and then the crushed ore is washed with water to remove impurities such as sediment; the crushed ore is made into a slurry, wherein m (limestone): m (water) = 1:35; Add ferric chloride hexahydrate to the configured slurry, and the addition amount is: n (the number of moles of Ca ²⁺ +Mg ²⁺ in the limestone): n (the number of moles of Fe ³⁺ in the reaction system)=6:2; The slurry added with ferric chloride hexahydrate was moved to a stirring tank, and the filling amount of the slurry was 60% of the volume of the stirring tank; the reaction was carried out at room temperature, the reaction time was 3h, and the stirring speed was 120r/min. After the reaction, the reaction material was sent to a filter press for pressure filtration, the filter cake was washed several times, and dried at 120° C., and the filter cake was subjected to subsequent separation treatment. The filtrate produced by the pressure filtration is pumped to the reaction tank, and the content of ^Mg in the filtrate is measured. According to the content of ^Mg , high-purity CaO is added to the filtrate. In the high-purity calcium oxide, CaO 99.0%, SiO ₂ 0.3%; the addition amount is: n(Mg ²⁺ ):n(CaO)=1:1.5. The reaction was carried out at room temperature, the reaction time was 3h, and the reaction was carried out under the reaction conditions, and the stirring speed was 1000r/min. After the reaction is completed, the reaction material is sent to a filter press for pressure filtration, and the filter cake is washed and dried, and then sent to the filter cake stack for subsequent separation treatment. The resulting filtrate is efficiently evaporated by a three-effect evaporator, the evaporation capacity is 100L/h～60t/h, the first-effect evaporation temperature is 90°C, the second-effect evaporation temperature is 75°C, and the third-effect evaporation temperature is 62°C to obtain calcium chloride dihydrate. The product, calcium chloride dihydrate is further sent to a high-temperature furnace, and heated at 360 ° C for 2 hours to obtain high-purity anhydrous calcium chloride.

According to GB/T 26520-2011 industrial calcium chloride, the anhydrous calcium chloride prepared in Example 1-3 is detected, and each relevant index is shown in attached table 1.

The chemical index of the calcium chloride anhydrous that the embodiment 1-3 of table 1 prepares

As can be seen from Table 1, each detection index of the calcium chloride anhydrous prepared by the present invention all meets the relevant requirements in Type I anhydrous calcium chloride in "GB/T26520-2011 Industrial Calcium Chloride".

Claims (6)

1. a method for producing high-purity anhydrous calcium chloride with limestone as raw material, is characterized in that: be made up of the following steps: (1) Preparation of slurry The limestone is crushed and washed with water, and then water is added to make a slurry; (2) Leaching reaction Add one of ferric chloride anhydrous or ferric chloride hexahydrate to the prepared slurry, and then transfer it to a stirring tank for leaching reaction; (3) Precipitation reaction After the reaction finishes, the obtained reaction mass is subjected to pressure filtration, and the gained filtrate is sent to the reaction tank, and the content of ^Mg in the filtrate is measured, and according to the content of ^Mg , in the filtrate, high-purity calcium oxide is added to carry out precipitation reaction; (4) Post-processing After the reaction is finished, the obtained reaction material is subjected to pressure filtration, and the generated filtrate is evaporated to obtain calcium chloride dihydrate, and the calcium chloride dihydrate is dried to obtain high-purity anhydrous calcium chloride; in: The chemical composition of the limestone ore described in step (1) is CaO 35-55.7%, SiO ₂ 0.07-6%, MgO 0.5-15%, Al ₂ O ₃ 0.4-5%, loss on ignition 22-40%, The remainder is impurities; The mass of limestone in the slurry described in step (1): the mass of water=1:1～1:50; The addition amount of the anhydrous ferric chloride or ferric chloride hexahydrate described in the step (2) is: the number of moles of Fe ³⁺ in the reaction system: the number of moles of Ca ²⁺ +Mg ²⁺ in the limestone=2: 3～ 6; In the high-purity calcium oxide described in step (3), CaO is 98.5-99.8%, and SiO ₂ is 0-0.5%; the amount of Mg ²⁺ in the filtrate: the amount of high-purity calcium oxide=1:1-1.5. 2 . The method for producing high-purity anhydrous calcium chloride using limestone as a raw material according to claim 1 , wherein in step (1), the limestone ore is crushed to a particle size of less than ≤3 mm. 3 . 3. the method for producing high-purity anhydrous calcium chloride with limestone as raw material according to claim 1, is characterized in that: in step (2), add the volume of the slurry of anhydrous ferric chloride or ferric chloride hexahydrate It is 60% to 80% of the volume of the stirring tank. 4. the method for producing high-purity anhydrous calcium chloride with limestone as raw material according to claim 1, is characterized in that: in step (2), the reaction temperature is room temperature, the reaction time is 0.5～3h, and the stirring speed is 120r/ min～1000r/min. 5. the method for producing high-purity anhydrous calcium chloride with limestone as raw material according to claim 1, is characterized in that: in step (3), reaction temperature is room temperature, reaction time is 0.5～3h, and stirring speed is 150r/ min～1000r/min. 6. The method for producing high-purity anhydrous calcium chloride with limestone as a raw material according to claim 1, is characterized in that: the evaporation described in the step (4) adopts a three-effect evaporator to carry out high-efficiency evaporation, and the evaporation capacity is 100L/ h～60t/h, evaporation temperature is 40～100℃; the drying is to send calcium chloride dihydrate to a high temperature furnace, and continue heating at 300～360℃ for 1h～2h to dry.

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