CN114956608A - Low-viscosity and low-cost calcium hydroxide suspension and preparation method thereof - Google Patents
Low-viscosity and low-cost calcium hydroxide suspension and preparation method thereof Download PDFInfo
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- CN114956608A CN114956608A CN202210709115.2A CN202210709115A CN114956608A CN 114956608 A CN114956608 A CN 114956608A CN 202210709115 A CN202210709115 A CN 202210709115A CN 114956608 A CN114956608 A CN 114956608A
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2/00—Lime, magnesia or dolomite
- C04B2/02—Lime
- C04B2/04—Slaking
- C04B2/06—Slaking with addition of substances, e.g. hydrophobic agents ; Slaking in the presence of other compounds
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2/00—Lime, magnesia or dolomite
- C04B2/02—Lime
- C04B2/04—Slaking
- C04B2/045—After-treatment of slaked lime
Abstract
The invention discloses a low-viscosity low-cost calcium hydroxide suspension and a preparation method thereof, which comprises the steps of uniformly mixing high-activity quicklime and common active quicklime, crushing and sieving, adding a first part of water for digestion into a reactor with a stirring device, adding an active promoter and/or a stabilizer dissolved in the water for digestion, adding the quicklime into the reactor for digestion reaction under the state of continuous stirring by the stirring device, adding a second part of water for dilution into the reactor after the digestion reaction is finished, uniformly stirring, performing hydrocyclone separation and/or sieving on the resultant mixed solution in the reactor, and removing impurities to obtain a target calcium hydroxide suspension finished product. The invention adopts the proportioning use of high-activity and common active quicklime and the process of adding water twice, accurately controls the raw materials, the process and the auxiliary agent, can obtain the calcium hydroxide suspension with low cost, low viscosity, high reaction activity and high calcium hydroxide content, and improves the application range of the product.
Description
Technical Field
The invention belongs to the technical field of calcium hydroxide production, and relates to a low-viscosity and low-cost calcium hydroxide suspension and a preparation method thereof.
Background
The calcium hydroxide is widely applied in the water treatment fields of neutralization of acidic wastewater, removal of heavy metal ions, phosphate ions, sulfate ions, fluoride ions and the like. In water treatment practice, calcium hydroxide is generally used as a suspension with water or after a calcium hydroxide suspension is obtained by wet digestion of calcium oxide.
The calcium hydroxide has the advantages of good safety and lower price than inorganic alkaline treatment agents such as sodium hydroxide, sodium carbonate and the like, but the defects mainly comprise two aspects: firstly, calcium hydroxide is slightly soluble in water, and compared with water-soluble alkali such as sodium hydroxide and the like, when chemical reaction occurs, the calcium hydroxide is firstly dissolved in water, and then calcium ions or hydroxide ions react with harmful substances in wastewater, so that the treatment speed of the calcium hydroxide is slower than that of the water-soluble alkali such as sodium hydroxide and the like when the calcium hydroxide is used for treating wastewater, and the water treatment efficiency is influenced; secondly, the solid content of the common calcium hydroxide suspension is 5-10% (while the concentration of the sodium hydroxide solution commonly used for water treatment is more than 30%), and the viscosity of the suspension is too high due to the high concentration, so that the suspension is difficult to convey and measure, and the production load and the production cost in the pulp preparation link are obviously increased. In addition to the two main defects, calcium hydroxide also has the problems of incomplete reaction, excessive addition, high impurity content, increased water treatment sludge amount and the like. Therefore, from the application point of view, calcium hydroxide suspension with high reactivity, high solid content, low viscosity and low impurity content is ideal for the water treatment industry.
It has been found that the dissolution rate of calcium hydroxide in water is related to the particle size, the smaller the particle size, the faster the dissolution rate, and the corresponding faster the chemical reaction rate, the better the reactivity of calcium hydroxide. At the same time, however, the smaller the particle size, the greater the viscosity of the suspension, which limits the increase in the calcium hydroxide content of the suspension. Therefore, it is technically difficult to obtain a calcium hydroxide suspension having high reactivity, high content and low viscosity at the same time.
To solve the above problems, a great deal of research has been conducted, mainly including:
1. the viscosity of the suspension is reduced by using an additive which can form precipitates or slightly soluble substances with calcium ions, for example, when calcium oxide is subjected to a digestion reaction with water, substances such as gypsum and the like are added into the water to reduce the viscosity of lime milk. However, this type of method results in a decrease in the reactivity of calcium hydroxide.
2. The viscosity is reduced by adding an organic polymer dispersant during the preparation of the calcium hydroxide suspension or during the wet digestion of calcium oxide, for example, the viscosity of the calcium hydroxide suspension is reduced by adding a polyacrylate dispersant in patent WO2018/048633A 1. Although the addition of the dispersant can reduce the viscosity of the suspension, the primary particle size of the calcium hydroxide cannot be reduced, i.e., the reactivity of the calcium hydroxide is not improved.
3. The method of wet milling (or milling plus dispersing agent) is used to reduce the particle size of the calcium hydroxide and thereby increase the reactivity of the calcium hydroxide, as disclosed in US 2019002301. The method increases the preparation steps of the suspension, is more complicated, and increases the addition proportion of corresponding additives although the particle size is reduced, thereby bringing obvious influence on the production cost.
4. High activity, low viscosity suspensions were prepared by varying the digestion process. For example, in patents CN106470960 and US2019092684, suspensions of calcium hydroxide are prepared by stepwise addition of water to lime, the water containing a dispersant or an inorganic salt. This approach is highly demanding for digestion equipment because at low water-to-ash ratios the lime slake product is pasty and has a very high viscosity that ordinary equipment cannot meet.
5. High-activity lime is used as a raw material, the characteristic of high reaction speed of the high-activity lime is utilized to reduce the particle size of calcium hydroxide, and the reaction activity of the high-activity lime is improved. However, the high-activity lime has the disadvantages of high price and high cost of the obtained calcium hydroxide suspension, and the disadvantage of relatively high viscosity of the obtained calcium hydroxide suspension.
6. In the industry, ordinary active lime with low price is used as a raw material to prepare a calcium hydroxide suspension, but in order to solve the problems that the ordinary active lime is slow to digest and low in product activity, high-temperature water with the temperature of more than 60 ℃ is generally used for digestion, and after digestion, the ordinary active lime needs to be aged for a long time to complete the digestion reaction. In this process, the source of high temperature water and the long aging time both make the production of calcium hydroxide suspension with common activated lime less efficient and more costly.
In summary, the method for preparing the calcium hydroxide suspension in the prior art has many disadvantages, which causes the problems of high reactivity, high content, high viscosity, high production cost and the like of the calcium hydroxide suspension produced by the method, and limits the application of the calcium hydroxide suspension in the fields of high reactivity requirement, low viscosity requirement, low cost requirement and the like.
Disclosure of Invention
In order to fill the blank of the prior art, the invention provides the calcium hydroxide suspension with high reaction activity, high calcium hydroxide content, low viscosity and low cost and the preparation method thereof, so as to overcome the defects in the prior art.
The technical scheme of the invention is as follows:
a method for preparing a low viscosity, low cost calcium hydroxide suspension comprising the steps of:
s1: respectively crushing and sieving high-activity quicklime and common active quicklime to screen out quicklime with the particle size of less than 8mm, weighing according to the mass ratio of 1: 2-9: 1, uniformly mixing for later use, wherein the activity of the high-activity quicklime is not lower than 360, and the activity degree of the common active quicklime is between 240-320;
s2: adding a dissolving activity promoter and/or a stabilizer into water to prepare a first part of slaking water, wherein the ratio of the total adding mass of the activity promoter and/or the stabilizer to the mass of the standby quicklime is 5: 1000-40: 1000, adding a first part of slaking water into a reactor with a stirring device, the mass ratio of the first part of slaking water to the standby quicklime is 2: 1-3: 1, the water temperature is controlled at 20-45 ℃, the activity promoter is a substance which can make water alkaline after being dissolved in water and can not generate precipitate after being mixed with calcium hydroxide, and the stabilizer is one or a mixture of a small molecular dispersant, sugar alcohol and saccharide;
s3: adding the standby quicklime into a reactor under the state of continuous stirring by a stirring device, wherein the adding process ensures that the quicklime and water are uniformly mixed, and the quicklime is not accumulated in the reactor, on the basis, the time of the adding process is not more than 15min, and in the digestion reaction process, the reaction time of the reactant with the temperature higher than 70 ℃ is not more than 60min and not less than 20 min;
s4: and after the digestion reaction is finished, adding a second part of diluting water into the mixed liquor obtained by the reaction under the state of continuous stirring by a stirring device, wherein the mass ratio of the second part of diluting water to the added standby quicklime is 0.4: 1-1.5: 1, uniformly stirring, and performing hydrocyclone separation and/or screening on the mixed liquor of the products in the reactor to remove large-particle impurities in the mixed liquor to obtain the finished product of the target calcium hydroxide suspension.
Further, the mass ratio of the high-activity quicklime to the common active quicklime is 7: 3-8: 2.
Further, in the step S1, the particle size of the screened ready-to-use quicklime is less than 5 mm.
Further, in the S1, the activity degree of the high-activity quicklime is not lower than 380.
Further, in the step S3, the time length of the feeding process does not exceed 10 min.
Further, in the step S3, the time period of the feeding process does not exceed 5 min.
Further, the activity promoter is one or a mixture of more of sodium hydroxide, potassium hydroxide, sodium acetate, sodium formate, monoethanolamine, diethanolamine and triethanolamine.
Further, the stabilizer is one or a mixture of potassium pyrophosphate, sodium hexametaphosphate, xylitol, sorbitol, erythritol, sucrose, glucose and fructose.
Furthermore, the ratio of the total mass of the added active accelerant and/or stabilizer to the mass of the ready quicklime is 10: 1000-30: 1000.
The calcium hydroxide suspension prepared by any preparation method has the advantages that the mass content of calcium hydroxide in the calcium hydroxide suspension is 25-40%, the particle size distribution is that D50 is more than or equal to 3 mu m and less than or equal to 6 mu m, D97 is more than or equal to 23 mu m, D100 is more than or equal to 45 mu m, the viscosity at 25 ℃ is less than or equal to 200 centipoises, and the reaction activity t90 is less than or equal to 5 seconds.
The quick lime mentioned in step S1 is tested according to the method specified in YB/T105-2005 metallurgical lime physical inspection method, and is composed of high-activity lime with activity degree not less than 360, preferably not less than 380 and ordinary active lime with activity degree 240-320. Ordinary lime activity lower than 240 slows down the reaction rate and lowers the activity of the product calcium hydroxide, while higher than 320 leads to increased costs and is uneconomical. The method has the advantages that the quicklime is crushed and then used, so that the digestion reaction process is more uniform and stable, the phenomena of bumping, local overheating and the like caused by porous massive lime are reduced, and the stability of product quality is facilitated. The size of the ground and sieved lime particles is not more than 8mm, otherwise the phenomena of bumping and the like are easily caused; the size of the crushed and sieved quicklime particles is preferably less than 5mm, and experiments show that the size has more remarkable effect on eliminating phenomena such as bumping and the like. The mass ratio of the high-activity lime to the common active lime is 1: 2-9: 1, preferably 7: 3-8: 2. When the ratio of the high-activity quicklime to the common active quicklime is lower than 1: 2, the activity of the product is poor, and when the ratio of the high-activity quicklime to the common active quicklime is higher than 9: 1, the effect of reducing the cost is not obvious. When the ratio of the high-activity lime to the common active lime is 7: 3-8: 2, the product has the optimal effect on the balance of performance and cost.
In step S2, a temperature of the digestion water lower than 20 ℃ leads to a decrease in reactivity of the resulting calcium hydroxide suspension, while a temperature higher than 45 ℃ leads to a significant increase in viscosity of the calcium hydroxide suspension. The mentioned active promoter is a substance which can make water alkaline after being dissolved in water, but does not include a substance which can react with calcium hydroxide to generate precipitate, and sodium hydroxide, potassium hydroxide, sodium acetate, sodium formate, monoethanolamine, diethanolamine, triethanolamine and the like are preferred; the stabilizer has double functions of improving the reaction activity of calcium hydroxide and reducing the agglomeration of calcium hydroxide particles, can be used alone or together with an activity promoter, and preferred stabilizers include small molecular dispersing agents such as potassium pyrophosphate and sodium hexametaphosphate, sugar alcohols such as xylitol, sorbitol and erythritol, and saccharide substances such as sucrose, glucose, fructose and the like. The total amount of the active promoter and/or stabilizer added is 0.5-4%, preferably 1-3% of the total mass of lime.
In step S3, the quicklime is fed at a slow speed, which affects the production efficiency and causes the reduction of the reactivity and the increase of the viscosity of the product, so that the quicklime is fed for no more than 15 minutes, preferably no more than 10 minutes, and most preferably no more than 5 minutes. When calcium hydroxide is generated through the digestion reaction of quicklime and water, heat is released to cause the temperature of a reaction system to rise, for the preparation of a calcium hydroxide suspension, the temperature rise is favorable for the digestion reaction to be more complete, but the reaction activity of the calcium hydroxide is reduced due to long-time high temperature, so that the time of the digestion reaction temperature of more than 70 ℃ is not more than 60 minutes and is not less than 20 minutes.
In step S4, the suspension obtained after the digestion reaction is removed of large particles by means of a hydrocyclone and/or a vibrating screen, which can remove the unreacted impurities carried in the lime raw material, such as silica, alumina, and unburnt limestone, to increase the content of calcium hydroxide in the suspension and reduce the amount of sludge generated during sewage treatment.
The applicant has found that the effect of adding water in two portions, which gives a suspension with a viscosity much lower than that obtained by adding the same weight of water to the reaction in one portion, is unexpected.
The mass ratio of the total mass of the digestion water to the quick lime is 2.4: 1-4: 1, the mass ratio of the first part of the digestion water to the quick lime is 2: 1-3: 1, the viscosity of the suspension is too high when the mass ratio of the first part of the digestion water to the quick lime is lower than 2: 1, the control of the uniformity of the reaction is not facilitated, and the contribution of the method to the reduction of the viscosity of a final product is not large when the mass ratio of the first part of the digestion water to the quick lime is higher than 3: 1. The method for calculating the adding amount of the second part of dilution water comprises the following steps: the total water addition is calculated according to the calcium hydroxide content of the final suspension, and the total water addition is determined by subtracting the consumption of the first part of the digestion water, and for the invention, the ratio of the second part of the water addition to the quicklime is 0.4: 1-1.5: 1.
In conclusion, the beneficial effects of the invention are as follows:
(1) the cost is greatly reduced: the invention uses the high-activity quicklime to be compounded with the common active lime, reduces the cost of raw materials, and unexpectedly: in the reaction process, the high-activity quicklime preferentially reacts to release heat to improve the water temperature, so that the digestion speed of the common active quicklime and the reaction activity of a digestion product are accelerated, the problems of low digestion speed and low reaction activity of the product of the common active quicklime are solved, the technical bias that the common active quicklime cannot be selected to prepare the high-activity calcium hydroxide suspension in the industry is broken through, the problem of high cost caused by the fact that the high-activity quicklime is used alone is solved, the problems that the digestion water temperature is high and long-time aging is needed when the common active lime is used alone for digestion are solved, and the production cost is reduced on the premise of ensuring the product performance.
(2) The viscosity is greatly reduced: the invention greatly reduces the viscosity of the calcium hydroxide suspension by using a method of adding slaked water in sections, has no adverse effect on the reactivity and the particle size distribution of calcium hydroxide in the suspension by adding water in batches, obtains unexpected beneficial effects, breaks through the thinking that the mass ratio of the added water to the quicklime needs to be adjusted when adjusting the viscosity, and greatly reduces the viscosity of the calcium hydroxide suspension under the condition of not changing the total water-cement ratio.
(3) The suspension has good performance indexes: the process prepares the calcium hydroxide suspension with high reaction activity, high calcium hydroxide content and low viscosity by precisely controlling the selection of raw materials, the improvement of the process, the selection of auxiliary agents and the feeding, and then removes large-particle impurities in the suspension by using a screening method such as hydrocyclone separation and the like, thereby solving the problems of low reaction speed, low production efficiency, high addition amount, more sludge and the like existing in the prior calcium hydroxide in water treatment application.
(4) The process has low manufacturing cost: expensive polymer dispersing agents are not used, all the used additives are common small-molecule chemical agents, and the optimal effect is realized through the combination of different agents; meanwhile, the invention does not need special equipment (such as a high-torque digester and the like), has simple operation and short reaction flow, and is favorable for reducing the manufacturing cost of the suspension.
Detailed Description
The following describes in detail embodiments of the present invention.
Example 1
S1, respectively weighing 2.25kg of high-activity quicklime with the activity degree of 400 and the particle size of less than or equal to 5mm after crushing and sieving and 0.25kg of common quicklime with the activity degree of 240 and the particle size of less than or equal to 5mm after crushing and sieving, and uniformly mixing the two quicklime with the activity degree of 240 for later use (the mass ratio of the two quicklime to the common quicklime is 9: 1, and the total amount of the quicklime to the quicklime is 2.5 kg);
s2, adding 7.48kg of water into the reactor, adding 10g of sodium hydroxide and 10g of potassium pyrophosphate into the water, and uniformly stirring to obtain 7.5kg of first part of digestion water, wherein the water temperature is controlled at 45 ℃;
s3, adding the slaking water into the slaking water S1 to prepare 2.5kg of quicklime powder for standby in 15 minutes under stirring. After the quicklime is added, quickly heating the reaction system, continuously stirring for 60 minutes after the temperature exceeds 70 ℃, and then stopping stirring;
s4, adding 2.5kg of normal temperature water (water for dilution) into the suspension, uniformly stirring the water and the suspension, discharging from the kettle body, and sieving by a 200-mesh sieve to obtain the finished product of the target calcium hydroxide suspension.
The calcium hydroxide suspension obtained was tested using the following test methods and standards: the content of the calcium hydroxide is tested according to the method specified in GB/T27815 & lt 2011 'industrial milky calcium hydroxide'; the viscosity of the suspension is tested by using an NDJ-9S rotational viscometer, the temperature of the suspension is stabilized at 25 ℃, and the suspension is tested by using a No. 2 or No. 3 rotor at the rotating speed of 60 revolutions per minute; the particle size distribution of the solid particles in the suspension was tested using a laser particle sizer; the reactivity of calcium hydroxide in the suspension is determined by conductivity method, i.e. according to the content of calcium hydroxide in the suspension, 0.1g of the suspension containing calcium hydroxide is weighed, the suspension is rapidly poured into 700g of deionized water (water temperature is 25 ℃), the change of the conductivity of the deionized water along with time is recorded, and the time consumed from pouring the calcium hydroxide suspension until the conductivity reaches 90% of the maximum value is calculated and recorded as t90, and the smaller t90, the faster the dissolution speed of calcium hydroxide is, and the higher the reactivity is.
Through determination, the calcium hydroxide suspension prepared in this example has the following indexes: the calcium hydroxide content was 25%, t90 ═ 5 seconds, viscosity 71cp, D50 ═ 5.5 μm, D97 ═ 18 μm, and D100 ═ 40.5 μm.
Example 2
Referring to example 1, 9kg of water having a temperature of 20 c was charged into a stirred reactor, 20g of sodium acetate and 90g of glucose were dissolved in the water, and 1.5kg of quicklime powder having an activity of 360 and 3kg of quicklime powder having an activity of 320 (all particle sizes < 8mm, completed within 5 minutes) were added to the water under stirring. After the quicklime is added, the reaction system is rapidly heated, after the temperature exceeds 70 ℃, the stirring is continuously carried out for 20 minutes, then the stirring is stopped, 1.8kg of normal-temperature water is added into the suspension, the water and the suspension are uniformly stirred, and then the suspension is discharged from the reaction kettle and sieved by a 200-mesh sieve, so that the calcium hydroxide suspension with the calcium hydroxide content of 40 percent, t90 being 4.3 seconds, the viscosity being 200cp, D50 being 5.5 mu m, D97 being 17.5 mu m and D100 being 37.8 mu m is obtained.
Example 3
Referring to example 1, 7.2kg of water having a temperature of 25 c was charged into a stirred reactor, 60g of sorbitol and 30g of sodium hexametaphosphate were dissolved in the water, and 2.55kg of quicklime powder having an activity of 380 and 0.45kg of quicklime powder having an activity of 260 (all particle sizes < 5mm, completion of the charging within 10 minutes) were added to the water under stirring. After the quicklime is added, the reaction system is rapidly heated, after the temperature exceeds 70 ℃, stirring is continuously carried out for 40 minutes, then stirring is stopped, 1.8kg of normal-temperature water is added into the suspension, the water and the suspension are uniformly stirred, and then the suspension is discharged from the reaction kettle and sieved by a 200-mesh sieve, so that the calcium hydroxide suspension of the calcium hydroxide suspension with the calcium hydroxide content of 35%, t90 ═ 4.6 seconds, viscosity of 148cp, D50 ═ 6 μm, D97 ═ 23 μm and D100 ═ 43.5 μm is obtained.
Example 4
Referring to example 1, 6.25kg of water having a temperature of 30 c was charged into a stirred reactor, 25g of triethanolamine, 25g of xylitol and 50g of sucrose were dissolved in the water, and 1.25kg of quicklime powder having an activity of 390 and 1.25kg of quicklime powder having an activity of 280 (all particle sizes < 5mm, completed within 5 minutes) were added to the water under stirring. After the quicklime is added, the reaction system is rapidly heated, the stirring is continuously carried out for 30 minutes after the temperature is over 80 ℃, then the stirring is stopped, 3.75kg of normal-temperature water is added into the suspension, the water and the suspension are uniformly stirred, and then the suspension is discharged from the reaction kettle and sieved by a 200-mesh sieve, so that the calcium hydroxide suspension with the calcium hydroxide content of 25 percent, the t90 of 4.7 seconds, the viscosity of 66cp, the D50 of 5.9 mu m, the D97 of 19.5 mu m and the D100 of 45 mu m is obtained.
Example 5
Referring to example 1, 7.8kg of water having a temperature of 30 c was charged into a stirred reactor, 30g of erythritol and 35g of monoethanolamine were dissolved in the water, and a mixture of 2.1kg of quicklime powder having an activity of 380 and 0.9kg of quicklime powder having an activity of 320 (all particle sizes < 5m, completed in 5 minutes) was added to the water under stirring. After the quicklime is added, the reaction system is rapidly heated, after the temperature exceeds 80 ℃, stirring is continuously carried out for 30 minutes, then stirring is stopped, 1.2kg of normal-temperature water is added into the suspension, the water and the suspension are uniformly stirred, and then the suspension is discharged from the reaction kettle and sieved by a 200-mesh sieve, so that the calcium hydroxide suspension with the calcium hydroxide content of 35%, t90 ═ 3.5 seconds, the viscosity of 101cP, D50 ═ 3 μm, D97 ═ 18.5 μm and D100 ═ 37.5 μm is obtained.
Example 6
Referring to example 1, 7.5kg of water having a temperature of 40 c was charged into a stirred reactor, 40g of diethanolamine and 12.5g of sucrose were dissolved in the water, and a mixture of 2.4kg of quicklime powder having an activity of 390 and 0.6kg of quicklime powder having an activity of 310 (all particle sizes < 5mm, completion of the charging within 5 minutes) was added to the water under stirring. After the quicklime is added, the reaction system is rapidly heated, after the temperature exceeds 80 ℃, the stirring is continuously carried out for 25 minutes, then the stirring is stopped, 1.5kg of normal temperature water is added into the suspension, the water and the suspension are uniformly stirred, then the suspension is discharged from the reaction kettle and sieved by a 200-mesh sieve, and the calcium hydroxide suspension with the calcium hydroxide content of 35 percent, the t90 being 3.3 seconds, the viscosity of 88cP, the D50 being 3.1 μm, the D97 being 19 μm and the D100 being 40 μm is obtained.
In conclusion, the low-viscosity and low-cost calcium hydroxide suspension prepared by the process is a calcium hydroxide suspension with the mass content of calcium hydroxide of 25-40%, the particle size distribution of D50 which is more than or equal to 3 mu m and less than or equal to 6 mu m, D97 which is less than or equal to 23 mu m, D100 which is less than or equal to 45 mu m, the viscosity at 25 ℃ which is less than or equal to 200 centipoises and the reaction activity t90 which is less than or equal to 5 seconds.
Comparative example 1
Referring to the process and detection method of example 1, the adding mode of the digestion water is changed into one-time adding of 10 kg:
10kg of water at 45 ℃ was added to a stirred reactor, 10g of sodium hydroxide and 10g of potassium pyrophosphate were dissolved in the water, and 2.5kg of quicklime powder was added to the water under stirring, wherein the content of highly active quicklime powder having an activity of 400 was 2.25kg and the content of ordinary quicklime powder having an activity of 240 was 0.25kg (particle size < 5mm, addition was completed within 15 minutes). After quicklime is added, the reaction system is rapidly heated, stirring is continuously carried out for 60 minutes after the temperature exceeds 70 ℃, then stirring is stopped, the mixed liquid after the reaction is discharged from the reaction kettle and passes through a 200-mesh sieve, and a calcium hydroxide suspension with the calcium hydroxide content of 25%, t90 of 5 seconds, the viscosity of 152cp, D50 of 6 μm, D97 of 18 μm and D100 of 40.5 μm is obtained through detection.
In comparison, in example 1, under the process condition of adding water in batches, the viscosity 71cp of the suspension is obviously reduced compared with the viscosity 152cp in the comparison, and the process has no adverse effect on main indexes such as the reactivity, the content and the particle size distribution of calcium hydroxide.
Therefore, the invention is suitable for the application fields with extremely high requirements on the viscosity and the fluidity of the calcium hydroxide suspension, relatively high requirements on the reaction activity and high requirements on the cost.
The foregoing shows and describes the general principles, principal features, and advantages of the invention. The present invention is not limited to the above-described embodiments, which are described in the specification and illustrated only for illustrating the principle of the present invention, but various changes and modifications may be made within the scope of the present invention as claimed without departing from the spirit and scope of the present invention. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (10)
1. A preparation method of low-viscosity and low-cost calcium hydroxide suspension is characterized by comprising the following steps: the method comprises the following steps:
s1: respectively crushing and sieving high-activity quicklime and common active quicklime to screen out quicklime with the particle size of less than 8mm, weighing according to the mass ratio of 1: 2-9: 1, uniformly mixing for later use, wherein the activity of the high-activity quicklime is not lower than 360, and the activity degree of the common active quicklime is between 240-320;
s2: adding a dissolving activity promoter and/or a stabilizer into water to prepare a first part of digestion water, wherein the ratio of the total added mass of the activity promoter and/or the stabilizer to the mass of the standby quicklime is 5: 1000-40: 1000, adding a first part of digestion water into a reactor with a stirring device, the mass ratio of the first part of digestion water to the standby quicklime is 2: 1-3: 1, the water temperature is controlled at 20-45 ℃, the activity promoter is a substance which can make water alkaline after being dissolved in water and is mixed with the calcium hydroxide to avoid generating precipitates, and the stabilizer is one or a mixture of a small molecular dispersant, a sugar alcohol and a saccharide substance;
s3: adding the standby quicklime into a reactor under the state of continuous stirring by a stirring device, wherein the adding process ensures that the quicklime and water are uniformly mixed, and the quicklime is not accumulated in the reactor, on the basis, the time of the adding process is not more than 15min, and in the digestion reaction process, the reaction time of the reactant with the temperature higher than 70 ℃ is not more than 60min and not less than 20 min;
s4: and after the digestion reaction is finished, adding a second part of diluting water into the mixed liquor obtained by the reaction under the state of continuous stirring by a stirring device, wherein the mass ratio of the second part of diluting water to the added standby quicklime is 0.4: 1-1.5: 1, uniformly stirring, and performing hydrocyclone separation and/or screening on the mixed liquor of the products in the reactor to remove large-particle impurities in the mixed liquor to obtain the finished product of the target calcium hydroxide suspension.
2. A method of preparing a low viscosity, low cost calcium hydroxide suspension according to claim 1, wherein: the mass ratio of the high-activity quicklime to the common active quicklime is 7: 3-8: 2.
3. A method of preparing a low viscosity, low cost calcium hydroxide suspension according to claim 1, wherein: in the S1, the particle size of the screened standby quicklime particles is less than 5 mm.
4. A method of preparing a low viscosity, low cost calcium hydroxide suspension according to claim 1, wherein: in S1, the activity degree of the high-activity quicklime is not lower than 380.
5. A method of preparing a low viscosity, low cost calcium hydroxide suspension according to claim 1, wherein: in the S3, the time length of the feeding process does not exceed 10 min.
6. A method of preparing a low viscosity, low cost calcium hydroxide suspension according to claim 1 or 5, wherein: in the S3, the time of the feeding process does not exceed 5 min.
7. A method of preparing a low viscosity, low cost calcium hydroxide suspension according to claim 1, wherein: the activity promoter is one or a mixture of more of sodium hydroxide, potassium hydroxide, sodium acetate, sodium formate, monoethanolamine, diethanolamine and triethanolamine.
8. A method of preparing a low viscosity, low cost calcium hydroxide suspension according to claim 1, wherein: the stabilizer is one or more of potassium pyrophosphate, sodium hexametaphosphate, xylitol, sorbitol, erythritol, sucrose, glucose and fructose.
9. A method of preparing a low viscosity, low cost calcium hydroxide suspension according to claim 1, wherein: the ratio of the total mass of the active accelerant and/or the stabilizer to the mass of the standby quicklime is 10: 1000-30: 1000.
10. A low viscosity, low cost suspension of calcium hydroxide, characterized by: the calcium hydroxide suspension prepared by any one of the preparation methods has the calcium hydroxide content of 25-40% by mass, the particle size distribution of D50 which is more than or equal to 3 mu m and less than or equal to 6 mu m, D97 which is more than or equal to 23 mu m, D100 which is more than or equal to 45 mu m, the viscosity at 25 ℃ which is less than or equal to 200 centipoises, and the reaction activity t90 which is less than or equal to 5 seconds.
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| CN114522554A (en) * | 2022-02-20 | 2022-05-24 | 深圳市长隆科技有限公司 | Preparation and application of superfine suspended calcium hydroxide |
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| CN101254935A (en) * | 2008-04-03 | 2008-09-03 | 武汉工程大学 | Method for preparing calcium hydroxide with high purity and high activity |
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