CN111302505A - A kind of method and system of reverse osmosis concentrated water regeneration and recovery of calcium carbonate - Google Patents

Abstract

A method and a system for recycling calcium carbonate by reverse osmosis concentrated water regeneration belong to the technical field of water treatment. Using Ca (OH)₂Calcium and magnesium ions and high-valence metal ions in the concentrated water are precipitated and separated to obtain a calcium carbonate product, and the concentrated water is regenerated and converted into raw water. The method realizes the linkage breakthrough of the field of wastewater regeneration and the inorganic salt industrial technology, the effect of wastewater regeneration and solid waste zero discharge shows obvious technical progress, the capability of utilizing concentrated water as a resource and recycling high-added-value calcium carbonate finished products to change waste into valuable represents the development direction in the future, and the advantages of low investment, convenient matching, simple operation, low operation cost and the like presented by the technical scheme determine the wide popularization prospect.

Description

A kind of method and system of reverse osmosis concentrated water regeneration and recovery of calcium carbonate

technical field

The invention belongs to the technical field of water treatment, and in particular relates to a method and a system for regenerating and recovering calcium carbonate from reverse osmosis concentrated water.

Background technique

The use of reverse osmosis equipment to produce pure water has been widely used by many industrial enterprises and households. However, the disadvantage of this technology is that when pure water is obtained, nearly 50% of the high-salt ion concentrated water has to be eliminated. Although this part of the eliminated concentrated water will not cause harm to the environment, and this water can also be used for greening watering flowers and road dust suppression, but for industrial industries with large water consumption, such as power plants, steel mills, chemical and other enterprises , Due to the large amount of eliminated water, it cannot be digested and utilized at all, and can only be discharged as industrial wastewater, resulting in a huge waste of water resources. Not only that, the high fees to be paid for discharging sewage also push up the cost of enterprises. In the long run, the policy requirements for zero discharge of wastewater are getting higher and higher, and the recovery and management of reverse osmosis concentrated water and the utilization of resources are imminent.

In terms of reverse osmosis concentrated water treatment, the practice adopted by many enterprises is to use high-pressure reverse osmosis to carry out secondary concentration treatment of concentrated water to obtain concentrated high-salt concentrated water for discharge, in order to minimize the amount of concentrated water, but this approach After paying a high price, only 50% of the concentrated water can be recovered, and no substantial effect has been achieved; some companies use the method of concentration and crystallization to crystallize the soluble salt in the concentrated water, so that the concentrated water can be restored to close to Recycling the properties of raw water, this technology can solve the problem of concentrated water recycling, but there is also a small amount of soluble mixed salt solid waste, especially the high treatment cost restricts the development of technology; there is also a technical trend, which is to use chemical The sedimentation method precipitates calcium and magnesium ions from concentrated water, and separates the sediment to convert the concentrated water into raw water. This technical trend is theoretically feasible, but there are also weak theoretical research, lack of certification in practice and the formation of problems. The problem of solid waste treatment. For example, "a kind of high-efficiency and high-recovery reverse osmosis concentrated water recovery and treatment method and system" disclosed in Chinese Patent Application No. 201410641681.X, although it is mentioned that "use slaked lime and soda ash to soften or chemically precipitate the reverse osmosis concentrated water, It is a better idea to remove calcium ions, magnesium ions and silicon that cause scaling. However, the two serious shortcomings brought about by this solution determine that the technology is not perfect and it is difficult to meet environmental protection requirements: first, the Concentrated water treatment uses sodium carbonate and hydrochloric acid, which will increase the soluble salt content of sodium chloride in the concentrated water, which will eventually increase the environmental protection hazard of waste salt discharge; second, the solid waste mixture obtained in this scheme has no other uses and chooses landfill treatment , which is tantamount to causing secondary pollution to the environment. This also objectively reflects the outstanding problems of the existing technology, such as low recovery rate, coexistence of high recovery rate and sharp increase in cost, and coexistence of high recovery rate and hidden dangers of environmental protection.

Therefore, in the field of reverse osmosis concentrated water treatment, there are still common problems that the wastewater cannot be fully utilized, the operating cost is too high, the use of certain chemicals causes environmental protection hazards, and the formation of solid waste results in secondary pollution. In terms of water, for example, there are still theoretical gaps in the field of precipitation treatment technology. The existing technology lacks theoretical basis and practical support, and there are even misunderstandings and fallacies. Interpenetration and innovation of technologies in various industries are needed.

SUMMARY OF THE INVENTION

The purpose of this invention is to provide a kind of method and system for reclaiming calcium carbonate by reverse osmosis concentrated water regeneration, and at the same time of recycling and precipitation of hardness ions such as calcium, magnesium, iron, aluminum, zinc in concentrated water, and regenerating concentrated water into components Clean water close to raw water can achieve zero discharge of wastewater and solid waste while obtaining calcium carbonate, greatly reducing costs and obtaining high economic benefits.

The technical theory on which the present invention is based is: based on the quality of groundwater in the north, most of the raw water quality has calcium bicarbonate type temporary hardness, so the components of the concentrated water discharged by reverse osmosis are mainly Ca(HCO ₃ ) ₂ and a small amount of Mg(HCO ₃ ) ₂ , there are a small amount of high-valent metal ion salts such as Fe ^{2 +} , AL ³⁺ , Zn ²⁺ and low-valent ion salts such as Na ⁺ , K ⁺ , NH ₄ ⁺ , and some SO ₄ ^2- , CI ^- , NO ₃ ^- plasma , wherein: the two salts of Ca(HCO ₃ ) ₂ and Mg(HCO ₃ ) ₂ account for more than 95% of the salt content of the concentrated water, and the total content is 8-15mmol/L. The calcium and magnesium ions and high-valent metal ions in the concentrated water are precipitated and separated by chemical precipitation to obtain calcium carbonate products containing a small amount of magnesium and trace amounts of iron, aluminum and zinc, and the concentrated water is regenerated and converted into raw water. Adding Ca(OH) ₂ slurry to concentrated water can make Ca(HCO ₃ ) ₂ react to form CaCO ₃ precipitation, and make Mg(HCO ₃ ) ₂ react to form MgCO ₃ precipitation; due to the addition of Ca(OH) ₂ slurry, water The PH value of the iron, aluminum and zinc ions in trace amounts will be precipitated from the concentrated water in the form of hydroxides; after the calcium and magnesium ions and iron, aluminum and zinc ions are efficiently separated, the total hardness of the concentrated water will decrease. The clean water whose composition is close to the raw water is regenerated. Here, the clean water is the raw water, which can also be called the regenerated raw water.

In order to achieve the above object, the invention provides a method for reclaiming calcium carbonate from reverse osmosis concentrated water regeneration, comprising the following steps:

a. Preparation of precipitant Ca(OH) ₂ slurry milk: use quicklime CaO block or powder, or slaked lime powder digestion method to prepare, based on quicklime CaO powder, quantitatively add concentrated water and quicklime to the digester in a stirring state, and concentrated water The mass ratio with quicklime CaO is 10:5-3, and the digestion reaction occurs to obtain Ca(OH) ₂ slurry. After the digestion and exothermic reaction is completed, the Ca(OH) ₂ slurry is adjusted to contain a certain solid content of CaO by adding concentrated water. The adjusted Ca(OH) ₂ slurry is pumped into the lime milk metering tank with a lime milk pump for use; namely:

CaO+H ₂ O→Ca(OH) ₂ ;

b. Use precipitant to react with concentrated water to precipitate hardness ions to regenerate raw water: quantitatively add concentrated water and a certain amount of precipitant Ca(OH) ₂ slurry to the precipitation reactor to precipitate it with the hardness ions in the concentrated water Reaction, the main content of calcium ions Ca ²⁺ precipitation reaction to form insoluble CaCO ₃ precipitation, the secondary content of magnesium ions Mg ²⁺ precipitation reaction to form insoluble MgCO ₃ precipitation, the trace presence of iron ions Fe ²⁺ precipitation Reaction to form Fe(OH) ₂ precipitation, aluminum ion AL ³⁺ precipitation reaction to form AL(OH) ₃ precipitation, zinc ion Zn ²⁺ precipitation reaction to form Zn(OH) ₂ precipitation, addition of precipitant Ca(OH) ₂ slurry The amount changes the total hardness, total alkalinity and phenolphthalein alkalinity of the regenerated raw water. When the total hardness of the regenerated raw water in the precipitation reactor is stable between 2-4 mmoL/L, and the total alkalinity is stable between 1-3 mmoL/L , with the phenolphthalein alkalinity not greater than 0.1 mmoL/L as the criterion for judging the end point of the reaction, indicating that the concentrated water will generate raw water or clear water after removing most of the hardness ions, namely:

Ca(HCO ₃ ) ₂ +Ca(OH) ₂ →2CaCO ₃ ↓+2H ₂ O

Mg(HCO ₃ ) ₂ +Ca(OH) ₂ →CaCO ₃ ↓+MgCO ₃ ↓+2H ₂ O

Ca(OH) ₂ →Ca ²⁺ +2OH ^-

Fe ²⁺ +2OH ^- →Fe(OH) ₂ ↓

AL ³⁺ +3OH ^- →AL(OH) ₃ ↓

Zn ²⁺ +2OH ^- →Zn(OH) ₂ ↓;

c. Recovering calcium carbonate: the regenerated raw water containing the precipitate obtained in step b is pumped into a filter for solid-liquid separation with a slurry pump, the filtrate is clean water with a composition close to raw water, and is sent to a clean water storage tank for storage as raw water for use. The water pump sends the regenerated raw water into the raw water system; the filter cake is the raw material of the recovered calcium carbonate in the present invention. Quality calcium carbonate products.

Preferably, in step a, the mass ratio of concentrated water and quicklime is quantitatively added to be 3:1, and after the digestion and exothermic reaction is completed, the concentrated water is added to adjust the Ca(OH) ₂ slurry with a CaO solid content of about 10% w/w.

Preferably, the properties of quicklime added in step a are lime powder, the quality requirements are CaO≥93%, fineness 200 mesh sieve residue≤1%, Fe≤0.1%.

Preferably, in step a, slaked lime powder Ca(OH) ₂ can be directly used to prepare precipitant Ca(OH) ₂ slurry, and step b can be directly added to react with concentrated water to precipitate hardness ions to regenerate raw water.

In order to achieve the above object, the present invention also provides a system for regenerating and reclaiming calcium carbonate from reverse osmosis concentrated water, which is characterized in that it includes a digester, a lime milk pump, a lime milk metering tank, a sedimentation reactor, a material Slurry pump, clean water pump, filter, clean water tank and belt conveyor, dryer and pulverizer connected or matched by material conveying, among which:

The digester includes an agitator, a lime feeding port, and a reverse osmosis concentrated water feeding port connected with the reverse osmosis concentrated water pipe, which is used for the digestion reaction of the concentrated water and quicklime block/or lime powder/and then slaked lime powder to prepare Ca. (OH) ₂ Serum milk;

The milk of lime pump is connected between the digester and the milk of lime metering tank through a pipeline, and is used to pump the _Ca (OH) slurry prepared by the digester into the milk of lime metering tank;

The feeding port of the milk of lime metering tank is connected with the milk of lime pump, and the discharging port of the milk of lime metering tank is connected with the feeding port of the precipitation reactor;

The precipitation reactor includes a stirrer, a feeding port connected with the lime milk metering tank, and a reverse osmosis concentrated water feeding port connected with the reverse osmosis concentrated water pipe, which is used to complete the reaction of precipitating agent and concentrated water to precipitate hardness ions to obtain / or the reaction of regenerating raw water;

The slurry pump is connected between the precipitation reactor and the filter through a pipeline, and is used for pumping the regenerated raw water and the precipitation mixed slurry in the precipitation reactor into the filter for solid-liquid separation;

The clean water tank is connected with the clean water outlet of the filter, and is used to store the regenerated raw water separated from the filtrate of the filter. The clean water pump is connected between the clean water tank and the raw water system to return the regenerated raw water to the raw water system. ;

The belt conveyor is arranged at the filter cake outlet of the filter, and is used for conveying the filter cake to the dryer;

The dryer is arranged between the belt conveyor and the pulverizer, and is used to dry the filter cake conveyed by the belt conveyor. The inlet of the dryer is matched and connected with the outlet of the belt conveyor, and the outlet of the dryer is connected with the inlet of the pulverizer. matching connection;

The pulverizer includes a feeding port connected to the outlet of the dryer and an outlet for powdered calcium carbonate, which is used for pulverizing the dried material into a finished product of calcium carbonate.

Compared with the prior art, the beneficial effects of the present invention are embodied in:

_The invention provides a method and a system for regenerating and recovering calcium carbonate from reverse osmosis concentrated water. Calcium carbonate, magnesium carbonate, iron hydroxide, aluminum hydroxide and zinc hydroxide are precipitated, which effectively and quickly reduces the hardness of concentrated water. In addition to recovering calcium carbonate products, the concentrated water is regenerated and turned into raw water. Compared with the prior art: the present invention improves the theoretical and practical basis of the chemical precipitation method for the regeneration of concentrated water at the level of technological innovation, and achieves the conditions of no waste water and solid waste generation through the connection and breakthrough of the field of waste water regeneration and inorganic salt industrial technology. The purpose of regenerating concentrated water into raw water shows extremely obvious technological progress. Its ability to reuse concentrated water and recover high value-added calcium carbonate products and turn waste into treasure represents the future development direction. The advantages of low investment, convenient matching, simple operation and low operating cost determine its broad promotion prospects.

Description of drawings

The present invention will be further described below with reference to the accompanying drawings and embodiments. Obviously, the accompanying drawings in the following description are only an embodiment of the present invention. For those of ordinary skill in the art, under the premise of no creative work , other drawings can also be obtained from these drawings.

Fig. 1 is a kind of reverse osmosis concentrated water regeneration method and system configuration schematic diagram of calcium carbonate recovery of the present invention; among the figure: 1-digester, 2-lime milk pump, 3-lime milk metering tank, 4-precipitation reactor, 5-Slurry pump, 6-Clean water pump, 7-Filter, 8-Belt conveyor, 9-Clean water storage tank, 10-Dryer, 11-Pulverizer

Detailed ways

Embodiment 1: as can be seen from Figure 1, the present invention provides a kind of method of reverse osmosis concentrated water regeneration reclaiming calcium carbonate, comprises the following steps:

a. Preparation of precipitant Ca(OH) ₂ slurry: prepared by the digestion method of quicklime powder CaO, add 1000Kg of concentrated water to the digester 1 in a stirring state, and then put in 300Kg of quicklime powder to make it undergo a digestion reaction to generate Ca(OH) ₂ Slurry milk, after the digestion and exothermic reaction is completed, add 1500Kg of concentrated water to adjust the Ca(OH) ₂ slurry milk into a slurry milk with a CaO solid content of 10% that is easy to transport, and use a lime milk pump 2 to adjust the Ca(OH) milk. ) _2. The slurry milk is pumped into the lime milk metering tank 3 for standby use;

B, react with precipitant and concentrated water to precipitate hardness ions and regenerate raw water: add 100 tons of concentrated water in precipitation reactor 4, then add precipitant Ca (OH) in 0.6 ton of lime milk metering tank ₃ Slurry milk, Make it react with the hardness ions in concentrated water to precipitate, react the main content of calcium ions Ca ²⁺ to form insoluble CaCO ₃ precipitation, and react the secondary content of magnesium ions Mg ²⁺ to form insoluble MgCO ₃ precipitation, Fe(OH) ₂ precipitation was formed by the precipitation reaction of iron ions Fe ²⁺ in trace amounts, and AL(OH) ₃ precipitation was formed by the precipitation reaction of aluminum ions AL ³⁺ _; Total hardness, total alkalinity and phenolphthalein alkalinity, when the total hardness of the regenerated raw water in the precipitation reactor 4 is stable between 2-4mmoL/L, and the total alkalinity is stable between 1-3mmoL/L, the phenolphthalein alkalinity is used. The index of not more than 0.1mmoL/L is used as the criterion for judging the end point of the reaction, indicating that the concentrated water will generate raw water after removing most of the hardness ions;

c, reclaiming calcium carbonate: the regenerated raw water containing sediment obtained in step b is pressed into filter 7 with slurry pump 5 for filtration and separation, the filtrate is the clear water whose composition is close to raw water, and is sent to clear water storage tank 9 for storage, and clear water pump 6 is used for storage. The regenerated raw water is sent to the raw water system; the filter cake is the raw material of the recovered calcium carbonate in the present invention, and the filter cake is transported to the dryer 10 through the belt conveyor 8 for drying, and the dried product is pulverized through the outlet of the dryer 10 to match the inlet of the pulverizer 11. Powder packaging to obtain magnesium-containing light calcium carbonate products.

Embodiment 2: as can be seen from Figure 1, the present invention provides a kind of method that reverse osmosis concentrated water regeneration reclaims calcium carbonate, comprises the following steps:

a. Preparation of precipitant Ca(OH) ₂ slurry milk: prepared by using quicklime block CaO digestion method, adding 1000Kg of concentrated water to digester 1 in a stirring state, and then adding 320Kg of quicklime block to make it undergo a digestion reaction to obtain Ca(OH) ₂ Slurry milk, after the digestion and exothermic reaction is completed, add 1500Kg of concentrated water to adjust the Ca(OH) ₂ slurry milk into a slurry milk with a CaO solid content of about 10% that is easy to transport, and use a lime milk pump 2 to adjust the Ca ( OH) ₂ slurry milk is pumped into lime milk metering tank 3 for standby use;

B, react with precipitant and concentrated water to precipitate hardness ions and regenerate raw water: add 100 tons of concentrated water in precipitation reactor 4, then add precipitant Ca (OH) in 0.7 ton of lime milk metering tank ₃ Slurry milk, Make it react with the hardness ions in the concentrated water; control the reaction end point by detecting the total hardness, total alkalinity and phenolphthalein alkalinity of the regenerated water, when the total hardness of the regenerated raw water in the precipitation reactor 4 is stable between 2-4mmoL/L, And when the total alkalinity is stable between 1-3mmoL/L, the phenolphthalein alkalinity index is not more than 0.1mmoL/L as the criterion for judging the reaction end point, which means that the concentrated water will generate raw water after removing most of the hardness ions;

c, reclaiming calcium carbonate: the regenerated raw water containing sediment obtained in step b is pressed into filter 7 with slurry pump 5 for filtration and separation, the filtrate is the clear water whose composition is close to raw water, and is sent to clear water storage tank 9 for storage, and clear water pump 6 is used for storage. The regenerated raw water is sent to the raw water system; the filter cake is the raw material of the recovered calcium carbonate in the present invention, and the filter cake is transported to the dryer 10 through the belt conveyor 8 for drying, and the dried product is sent to the pulverizer 11 for pulverization and packaging to obtain magnesium-containing light weight calcium carbonate products.

Embodiment 3: as can be seen from Figure 1, the present invention provides a kind of method of reverse osmosis concentrated water regeneration reclaiming calcium carbonate, comprises the following steps:

a. Preparation of precipitating agent Ca(OH) ₂ slurry milk: use slaked lime Ca(OH) ₂ powder to directly pulp to make Ca(OH) ₂ slurry milk, add 3000Kg of concentrated water to digester 1 in a stirring state, and then add slaked lime Ca(OH) 2 (OH ₎ powder 500Kg, make it slurried to obtain Ca(OH) slurried milk, then with lime milk pump ₂ the adjusted Ca(OH ₎ slurried milk is pumped into lime milk metering tank 3 for standby use;

b, react with precipitant and concentrated water to precipitate hardness ions and regenerate raw water: add 100 tons of concentrated water in precipitation reactor 4, then add 0.6 tons of precipitant Ca(OH) from milk of lime metering tank ₃ Slurry milk , make it react with the hardness ions in the concentrated water; control the reaction end point by detecting the total hardness, total alkalinity and phenolphthalein alkalinity of the regenerated raw water, when the total hardness of the regenerated raw water in the precipitation reactor 4 is stable at 2-4mmoL/L When the total alkalinity is stable between 1-3 mmoL/L, the phenolphthalein alkalinity index is not more than 0.1 mmoL/L as the criterion for judging the reaction end point, which means that the concentrated water will generate raw water after removing most of the hardness ions;

c, reclaiming calcium carbonate: the regenerated raw water containing sediment obtained in step b is pressed into filter 7 with slurry pump 5 for filtration and separation, the filtrate is the clear water whose composition is close to raw water, and is sent to clear water storage tank 9 for storage, and clear water pump 6 is used for storage. The regenerated raw water is sent to the raw water system; the filter cake is the raw material of the recovered calcium carbonate in the present invention, the filter cake is transported to the dryer 10 for drying through the belt conveyor 8, and the dried product is sent to the pulverizer 11 for pulverization and packaging to obtain magnesium-containing light weight. calcium carbonate products.

Embodiment 4: as shown in Figure 1, the present invention also provides a kind of system of reverse osmosis concentrated water regeneration and reclaiming calcium carbonate, it is characterized in that: comprise digester 1, lime milk pump 2, lime milk metering that are connected successively by pipeline Tank 3, precipitation reactor 4, slurry pump 5, clean water pump 6, filter 7, clean water tank 8 and belt conveyor 9, dryer 10, pulverizer 11 connected by material conveying or matching connection, wherein:

The digester 1 includes a stirrer, a lime feeding port, and a reverse osmosis concentrated water feeding port connected with a reverse osmosis concentrated water pipe, and is used for the digestion reaction of concentrated water and quicklime block/or lime powder/and then slaked lime powder to prepare Ca(OH) ₂ syrup;

Described milk of lime pump 2 is connected between digester 1 and milk of lime metering tank 3 by pipeline, for the Ca(OH) prepared by digester ₁ The milk of lime is pumped into milk of lime metering tank 3;

The feeding port of the milk of lime measuring tank 3 is connected with the milk of lime pump 2, and the discharging port of the milk of lime measuring tank 3 is connected with the feeding port of the precipitation reactor 4;

The precipitation reactor 4 includes a stirrer, a feeding port connected with the lime milk metering tank 3, and a reverse osmosis concentrated water feeding port connected with the reverse osmosis concentrated water pipe, for completing the reaction of the precipitant and the concentrated water to precipitate out hardness. Reaction of ions to regenerate raw water;

The slurry pump 5 is connected between the precipitation reactor 4 and the filter 7 through a pipeline, and is used for pumping the regenerated raw water and the precipitation mixed slurry in the precipitation reactor 4 into the filter 7 for solid-liquid separation;

The clean water tank 9 is connected with the clean water outlet of the filter 7, and is used to store the regenerated raw water separated from the filtrate of the filter 7. The clean water pump 6 is connected between the clean water tank 9 and the raw water system, and is used for regenerating good The raw water is returned to the raw water system;

The belt conveyor 8 is arranged at the filter cake outlet of the filter 7 for transporting the filter cake to the dryer 10;

The dryer 10 is arranged between the belt conveyor 8 and the pulverizer 11, and is used to dry the filter cake conveyed by the belt conveyor 8. The inlet of the dryer 10 is matched with the outlet of the belt conveyor 8, and the drying The outlet of the crusher 10 is matched and connected with the inlet of the pulverizer 11;

The pulverizer 11 includes a feed port connected to the outlet of the dryer 10 and an outlet for powdered calcium carbonate, which is used for pulverizing the dried material into a finished product of calcium carbonate.

Claims (4)

1. a method for reclaiming calcium carbonate by reverse osmosis concentrated water regeneration, comprises the following steps: a. Preparation of precipitant Ca(OH) ₂ slurry: using quicklime CaO block or powder, or slaked lime powder digestion method to prepare, in terms of quicklime CaO powder, quantitatively add concentrated water and quicklime to the digester (1) in a stirring state , the mass ratio of concentrated water and quicklime CaO is 10:5-3, the digestion reaction occurs to obtain Ca(OH) ₂ slurry, after the digestion and exothermic reaction is completed, the Ca(OH) ₂ slurry is adjusted to contain a certain amount of concentrated water by adding concentrated water The slurry milk of CaO solid content, with the lime milk pump (2), the adjusted Ca(OH) ₂ slurry milk is pumped into the lime milk metering tank (3) for use; b. Use the precipitant to react with concentrated water to precipitate hardness ions and regenerate raw water: quantitatively add concentrated water and a certain amount of precipitant Ca(OH) ₂ slurry to the precipitation reactor (4) to make it match the hardness of the concentrated water. The ions undergo precipitation reaction, the main content of calcium ions Ca ²⁺ will be precipitated to form insoluble CaCO ₃ precipitation, the secondary content of magnesium ions Mg ²⁺ will be precipitated to form insoluble MgCO ₃ precipitation, and the trace amount of iron ions Fe will be precipitated. ²⁺ precipitation reaction to form Fe(OH) ₂ precipitation, aluminum ion AL ³⁺ precipitation reaction to form AL(OH) ₃ precipitation, zinc ion Zn ²⁺ precipitation reaction to form Zn(OH) ₂ precipitation; precipitant Ca(OH) ₂ slurry The amount of milk added changes the total hardness, total alkalinity and phenolphthalein alkalinity of the regenerated raw water. When (4) the total hardness of the regenerated raw water in the precipitation reactor is stable between 2-4 mmoL/L, and the total alkalinity is stable at 1- When it is between 3 mmoL/L, the phenolphthalein alkalinity index is not more than 0.1 mmoL/L as the criterion for judging the reaction end point, which means that the concentrated water will generate raw water after removing most of the hardness ions; c, reclaiming calcium carbonate: the regenerated raw water containing the sediment obtained in step b is pumped into the filter (7) with a slurry pump (5) to carry out solid-liquid separation, and the filtrate is clean water with a composition close to raw water, and is sent to a clean water storage tank ( 9) store as raw water for use, and send the regenerated raw water into the raw water system with a clean water pump (6); the filter cake is the raw material of the recovered calcium carbonate of the present invention, and the filter cake is transported to the dryer (10) by the belt conveyor (8) After drying, the dried product is sent to a pulverizer (11) for pulverization, and the powder is packaged to obtain a magnesium-containing light calcium carbonate product. 2. the method for reclaiming calcium carbonate by a kind of reverse osmosis concentrated water regeneration according to claim 1, is characterized in that: in step a, quantitatively adding concentrated water and quicklime mass ratio is 3: 1, after the elimination exothermic reaction is completed, adding The concentrated water is adjusted to a Ca(OH) ₂ slurry with a CaO solid content of about 10% w/w. 3. the method that a kind of reverse osmosis concentrated water regeneration reclaims calcium carbonate according to claim 1, comprises the following steps: a. Preparation of precipitating agent Ca(OH) ₂ slurry milk: prepared by the digestion method of quicklime powder CaO, add 1000Kg of concentrated water to the digester (1) in a stirring state, and then put in 300Kg of quicklime powder to make it undergo a digestion reaction to generate Ca( OH) ₂ slurry, after the digestion and exothermic reaction is completed, add 1500Kg of concentrated water to adjust the Ca(OH) ₂ slurry into a slurry with a CaO solid content of 10% that is easy to transport, and is adjusted with a lime milk pump (2). The Ca(OH) ₂ slurry is pumped into the lime milk metering tank (3) for use; b. Use precipitant and concentrated water to react to precipitate hardness ions and regenerate raw water: add 100 tons of concentrated water in the precipitation reactor (4), and then add the precipitant Ca(OH) in the 0.6-ton lime milk metering tank (3). ₂ Slurry milk, so that it reacts with hardness ions in concentrated water; precipitant Ca(OH) ₂ The amount of slurry milk added changes the total hardness, total alkalinity and phenolphthalein alkalinity of regenerated water, when the precipitation reactor (4) When the total hardness of the recycled raw water is stable between 2-4mmoL/L and the total alkalinity is stable between 1-3mmoL/L, the phenolphthalein alkalinity index is not more than 0.1mmoL/L as the criterion for judging the reaction end point, indicating that concentrated water After removing most of the hardness ions, raw water is generated; c, reclaiming calcium carbonate: the regenerated raw water containing the sediment obtained in step b is pressed into a filter (7) with a slurry pump (5) for filtration and separation, and the filtrate is clean water with a composition close to raw water, and is sent to a clean water storage tank (9) Storage, use the clean water pump (6) to send the regenerated raw water into the raw water system; the filter cake is the raw material of the calcium carbonate recovered by the present invention, and the filter cake is transported to the dryer (10) by the belt conveyor (8) for drying, and the dried product passes through The outlet of the dryer (10) matches the inlet of the pulverizer (11) for pulverization and powder packaging to obtain a magnesium-containing light calcium carbonate product. 4. a system for reclaiming calcium carbonate by reverse osmosis concentrated water regeneration, is characterized in that: comprise digester (1), lime milk pump (2), lime milk metering tank (3), precipitation reactor ( 4), slurry pump (5), clean water pump (6), filter (7), clean water tank (9) and belt conveyor (8), dryer (10), pulverizer connected by material conveying or matching connection (11), where: The digester (1) comprises an agitator, a lime feeding port, and a reverse osmosis concentrated water feeding port connected with the reverse osmosis concentrated water pipe, and is used for the digestion reaction of the concentrated water and quicklime block/or lime powder/and then or slaked lime powder , to prepare Ca(OH) ₂ slurry; The milk of lime pump (2) is connected between the digester (1) and the milk of lime metering tank (3) through a pipeline, and is used for pumping the Ca(OH) slurry prepared by the digester ( ₁ ) to the lime in the milk measuring tank (3); The feeding port of the milk of lime measuring tank (3) is connected with the milk of lime pump (2), and the discharge port of the milk of lime measuring tank (3) is connected with the feeding port of the precipitation reactor (4); The precipitation reactor (4) comprises a stirrer, a feeding port connected with the lime milk metering tank (3), and a reverse osmosis concentrated water feeding port connected with a reverse osmosis concentrated water pipe, for completing the use of precipitating agent and concentrated water The reaction precipitates hardness ions and regenerates raw water; The slurry pump (5) is connected between the precipitation reactor (4) and the filter (7) through a pipeline, and is used for pumping the raw water and precipitation mixed slurry regenerated in the precipitation reactor (4) into the filter (7) carry out solid-liquid separation; The clean water tank (9) is connected with the clean water outlet of the filter (7) for storing the regenerated raw water separated from the filtrate of the filter (7), and the clean water pump (6) is connected to the clean water tank (9) and the raw water. Between systems, it is used to return the regenerated raw water to the raw water system; The belt conveyor (8) is arranged at the filter cake outlet of the filter (7) for transporting the filter cake to the dryer (10); The dryer (10) is arranged between the belt conveyor (8) and the pulverizer (11), and is used for drying the filter cake conveyed by the belt conveyor (8). The inlet of the dryer (10) is connected to the belt conveyor. (8) The outlet is matched and connected, and the outlet of the dryer (10) is matched and connected with the inlet of the pulverizer (11); The pulverizer (11) includes a feed port connected to the outlet of the dryer (10) and an outlet for powdered calcium carbonate, which is used for pulverizing the dried material into a finished product of calcium carbonate.

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