CN205340185U - Continuous crystallization equipment of multistage high vacuum insulation flash distillation - Google Patents

Abstract

The utility model relates to a multi-stage vacuum adiabatic flash evaporation continuous crystallization equipment. A plurality of crystallizers are connected in series; the mold is divided into an upper straight cylinder section and a lower straight cylinder section; the lower straight cylinder section has a smaller diameter, the upper straight cylinder section has a larger diameter, and the two straight cylinder sections are connected by a variable diameter; the upper straight cylinder section is short, and the lower straight cylinder section is long; The bottom of the crystallizer is a W-shaped bottom; there is a guide tube in the straight section of the lower part of the crystallizer; the motor for stirring is located on the top of the crystallizer, and the stirring paddle is stirred by double-layer paddles. The paddle is higher than the draft tube, and the bottom stirring paddle is located at the lower part of the draft tube. The top of the crystallizer is connected with a condenser and a water ring vacuum pump; the lower part of the crystallizer is equipped with a turbidimeter. The material inlet of each stage of crystallizer is located at the bottom of the guide tube, which is higher than the stirring paddle of the lower layer; the discharge port is located at the bottom of the crystallizer; the discharge pipe of the last stage of crystallizer is connected to the centrifuge. The upper part of each crystallizer is provided with a spray pipe. The production crystal particle size is uniform, the appearance is good, the crystal particle size is large and stable.

Description

A multi-stage vacuum adiabatic flash evaporation continuous crystallization equipment

technical field

The utility model relates to a continuous crystallization device, in particular to a multi-stage vacuum adiabatic flash evaporation continuous crystallization equipment; in particular to a multi-stage vacuum adiabatic flash evaporation continuous crystallization equipment.

Background technique

In chemical production, the crystallization process is roughly divided into two forms: continuous crystallization and batch crystallization. The batch crystallization process is a crystallization process in which raw materials are added at one time, then crystals are obtained through different crystallization methods, and the crystals are separated from the mother liquor for the last time. Due to the defects of its operation mode, the quality of the product depends very much on the experience of the operator, which often leads to problems such as uneven crystal thickness and difficulty in filtration. And because the batch crystallization operation is discontinuous, its production efficiency is often not high enough, and the equipment occupies a large area.

Continuous crystallization is a crystallization process in which materials are continuously fed into the crystallizer and products are continuously obtained. For large-scale industrial crystallization processes, the advantage of continuous crystallization is that continuous crystallization can control the supersaturation of the mother liquor within the metastable region by controlling the operating conditions of different stages of crystallizers, thereby effectively controlling nucleation, making The particle size distribution of the product is narrow, which improves the quality of the product. Due to continuous feeding and continuous discharging, the number of equipment in the crystallization process is greatly reduced, so that the crystallization process that originally required multiple batch crystallizers becomes only a set of continuous crystallization system. And because of continuous production, it can reduce the impact of human operation on the crystal, reduce the difference between different batches of products, and achieve the purpose of stably controlling product quality.

Continuous crystallization can be divided into continuous cooling, continuous evaporation, adiabatic flash evaporation and other crystallization operations. For the continuous crystallization of some species, because the concentration of the mother liquor is often relatively high, if the operation mode of continuous cooling crystallization is adopted, the problem of wall formation is often not easy to solve. However, due to the continuous operation process, there is always a degree of supersaturation in the mother liquor. Once the wall is formed, the wall will continue to grow. The continuous growth of the wall will have an adverse effect on the stirring and heat transfer in the crystallizer, and eventually lead to the operation. It cannot run continuously, so how to avoid wall formation is the key issue for continuous crystallization. Adiabatic flash evaporation is a process in which the solvent evaporates under vacuum to take away the heat of the mother liquor and make the mother liquor cool and crystallize. The heat exchange surface is at the gas-liquid interface, and there is no cooling surface for solid-liquid contact. , will not cause fouling on the wall due to heat exchange with the environment, so the problem of wall formation can be better avoided, thereby ensuring continuous operation of production.

In the Chinese patent CN200710130643.8 multifunctional and multi-effect automatic continuous evaporation crystallization process and crystallization equipment, a continuous evaporation process is introduced, which is characterized in that the steam evaporated by the crystallizer is used as the preheating steam of the raw material liquid, so as to save energy consumption the goal of. However, the magma external circulation crystallizer used in this patent needs to be heated and evaporated by external steam, which will make the external evaporator easy to wall and cause continuous operation to be unstable.

Chinese patent CN203816265U inorganic salt continuous crystallization device introduces a crystallizer for continuous crystallization of inorganic salt, which is characterized in that it uses external circulation cooling and vacuum evaporation equipment. However, due to the external circulation cooling in the equipment, the cooling pipes are relatively easy to foul, which affects the continuous operation of the device. And because there is no agitation inside the crystallizer, the mixing condition of the slurry may be deteriorated, thereby deteriorating the crystal grain size.

Contents of the invention

The purpose of the utility model is to provide a multi-stage continuous vacuum adiabatic flash evaporation continuous crystallization equipment which can increase the granularity of crystallized products and stably control the quality of the crystals, aiming at the defects of the existing continuous crystallization equipment.

The technical scheme provided by the utility model is:

A multi-stage vacuum adiabatic flash evaporation continuous equipment of the utility model; multiple crystallizers are connected in series; the crystallizer is divided into an upper straight cylinder section and a lower straight cylinder section; the lower straight cylinder section has a small diameter, the upper straight cylinder section has a larger diameter, Connected by a variable diameter; the upper straight section is short and the lower straight section is long; the bottom of the crystallizer is a W-shaped bottom; the lower straight section of the crystallizer has a guide tube; the stirring motor is located on the top of the crystallizer, and the stirring paddle uses double-layer stirring Paddle stirring, the diameter of the stirring paddle is smaller than that of the guide tube, the top layer of stirring paddle is higher than the guide tube, and the bottom layer of stirring paddle is located at the lower part of the guide tube.

The diameter ratio of the upper straight section and the lower straight section is 1.2-2; the height ratio of the upper straight section and the lower straight section is 0.5-1;

The ratio of the height of the guide tube to the height of the lower straight tube section is 0.5-1, the ratio of the diameter of the guide tube to the diameter of the lower straight tube section is 0.5-0.9; the ratio of the diameter of the stirring blade to the diameter of the guide tube is 0.6-0.95.

The top of the crystallizer is connected with a condenser and a water ring vacuum pump; the lower part of the crystallizer is equipped with a turbidimeter. The material inlet of each level of crystallizer is located at the bottom of the guide tube, which is higher than the stirring paddle of the lower layer; the material outlet is located at the bottom of the crystallizer; the discharge pipe of the last stage of crystallizer is connected to the centrifuge. The upper part of each crystallizer is provided with a spray pipe; the outer wall of the crystallizer is wrapped with a thermal insulation layer.

In the crystallizer of the utility model, the larger diameter of the upper part is mainly to prevent fluctuations in vacuum degree and liquid entrainment caused by evaporation. The bottom of the crystallizer is a W-shaped bottom, which is a design obtained through fluid mechanics simulation to reduce the flow dead zone. The motor for stirring is located on the top of the crystallizer, and the stirring paddle uses double-layer stirring paddles for stirring, so that a lower stirring speed can be used and a better mixing effect can be achieved. The purpose of using top stirring is to have a better mixing effect when the solid content in the mother liquor is high. A condenser and a water ring vacuum pump are connected to the top of the crystallizer to provide vacuum. The lower part of the crystallizer is equipped with a turbidimeter, which is used to measure the slurry density inside the crystallizer and provide parameters for controlling the operation of the crystallizers at all levels.

The material inlets of crystallizers at all levels are located at the bottom of the draft tube, which is higher than the stirring paddle in the lower layer. The outlet is located at the bottom of the crystallizer. The raw material liquid of the first stage crystallizer is injected from the mother liquor tank. The output of the upper stage crystallizer is directly injected into the next stage crystallizer through the pump, and the pipes are connected by flanges. The discharge pipe of the final crystallizer is connected to the centrifuge, and the crystals obtained by centrifugation are dried and packed into the warehouse. If the last-stage crystallizer needs mother liquor circulation, the mother liquor obtained after centrifugation will be re-injected into the last-stage crystallizer by the pump.

The upper part of each crystallizer is equipped with a spray pipe, and the water evaporated in the crystallizer is used to spray the junction wall at the evaporation surface of the inner wall of the crystallizer to ensure continuous operation. The outer wall of the crystallizer is wrapped with a thermal insulation layer, which is used to prevent the inner wall of the crystallizer from forming due to the low temperature of the environment.

Using this equipment for continuous crystallization will have the following beneficial effects:

1. The produced crystals have uniform particle size, good appearance, large crystal particle size and stable particle size.

2. Compared with intermittent production, continuous production reduces the intermediate operation steps and labor intensity, and can reduce the difference between batches of products caused by staff operation problems through automatic control operation.

3. Improve the production efficiency of the crystallization process and greatly reduce the number of equipment.

4. The method and equipment of the utility model can also be extended to the production of various inorganic salts and organic products.

Description of drawings

Fig. 1 is a typical crystallizer of the present utility model;

Fig. 2 is a two-stage continuous crystallization device diagram;

Fig. 3 is a four-stage continuous crystallization device diagram;

Fig. 4 is a three-stage continuous crystallization device diagram;

Fig. 5 is the product particle size that sodium hydrogen phosphate uses this technology continuous crystallization to obtain;

Fig. 6 is the sodium hydrogen phosphate crystal photograph that uses this technique to obtain;

1. Spray water pipe, 2. Insulation layer, 3. Feed inlet, 4. Turbidimeter, 5. Motor, 6. Guide tube, 7. Stirring paddle, 8. Outlet, 9. Condenser, 10 1. Raw material storage tank, 11. Centrifugal pump, 12. Crystallizer, 13. Screw pump, 14. Condensed water storage tank, 15. Water ring vacuum pump, 16. Centrifuge.

detailed description

Below in conjunction with accompanying drawing and embodiment, the specific embodiment of the utility model is further described. The following examples are only used to illustrate the technical solutions of the present utility model more clearly, but cannot limit the protection scope of this patent with this.

Example 1

As shown in Figure 1, a continuous vacuum adiabatic flash evaporation continuous crystallizer. There is a thermal insulation layer 2 outside the crystallizer. The diameters of the upper and lower straight cylinders of the crystallizer are different. The diameter of the upper part is larger than that of the lower part. The diameter of the upper straight cylinder is 3.5 meters. The height of the segment is 2 meters. The hot material enters the inside of the guide tube 6 from the feed port 3, and is stirred by a double-layer large-diameter stirring paddle 7. The height of the guide tube is 1.7 meters, the diameter of the guide tube is 1.83 meters, and the diameter of the stirring paddle is It is 1.8 meters. The mixing in the crystallizer is uniform, and there is a spray pipe 1 on the upper part of the crystallizer for spraying the inner wall of the crystallizer to remove the knot wall at the evaporation surface. The evaporated water in the crystallizer is condensed by the condenser 9 and enters the condensed water storage tank. A turbidity meter 4 is installed at the lower part of the crystallizer to monitor the slurry density in the crystallizer.

Example 2

As shown in Figure 2, a vacuum adiabatic flash evaporation continuous crystallization device consists of two crystallizers connected in series. The top of the crystallizer is connected with a condenser and a water ring vacuum pump; the lower part of the crystallizer is equipped with a turbidimeter. The material inlet of each level of crystallizer is located at the bottom of the guide tube, which is higher than the stirring paddle of the lower layer; the material outlet is located at the bottom of the crystallizer; the discharge pipe of the last stage of crystallizer is connected to the centrifuge. The upper part of each crystallizer is provided with a spray pipe; the outer wall of the crystallizer is wrapped with a thermal insulation layer. The concentration in the storage tank 10 is 17%, and the sodium hydrogen phosphate mother liquor with a temperature of 80 degrees is entered into the first-stage crystallizer 12 by the centrifugal pump 11 according to the flow rate of 7m3/h, and the first-stage crystallizer 12 is controlled by controlling the power of the water ring vacuum pump 15. The degree of vacuum in the first-stage crystallizer 12 makes the solid content in the first-stage crystallizer 12 6%. And control the average residence time of the slurry in the first stage crystallizer to be 2h. The water flashed out of the crystallizer is condensed by the condenser 9 and stored in the condensed water storage tank 14. When there are many walls on the evaporation surface, the water in the condensed water storage tank is pumped into the first-stage crystallization through the centrifugal pump 11 In the container, wash away the knot wall. The slurry in the first-stage crystallizer is injected into the second-stage crystallizer 12 by the screw pump pump 13, and the vacuum degree in the second-stage crystallizer 12 is controlled at 97kpa by controlling the power of the water ring vacuum pump 15, and the residence time is 2h . The water flashed out in the second-stage crystallizer 12 is condensed through the condenser 9 and stored in the condensed water storage tank 14. When there are many walls on the evaporation surface, the water in the condensed water storage tank is pumped into the condensed water storage tank through the centrifugal pump 11. In the second-stage crystallizer, the wall is washed away. The slurry in the second-stage crystallizer is injected into the centrifuge by the pump 13, and the centrifuged crystals are blown and dried at room temperature before being packaged and stored.

Example 3

As shown in Figure 3, a vacuum adiabatic flash evaporation continuous crystallization device consists of four crystallizers connected in series; the top of the crystallizer is connected with a condenser and a water ring vacuum pump; the lower part of the crystallizer is equipped with a turbidimeter. The material inlet of each level of crystallizer is located at the bottom of the guide tube, which is higher than the stirring paddle of the lower layer; the material outlet is located at the bottom of the crystallizer; the discharge pipe of the last stage of crystallizer is connected to the centrifuge. The upper part of each crystallizer is provided with a spray pipe; the outer wall of the crystallizer is wrapped with a thermal insulation layer. The concentration in the storage tank 10 is 23%, and the sodium hydrogen phosphate mother liquor with a temperature of 90 degrees is entered into the first-stage crystallizer 12 by the centrifugal pump 11 according to the flow rate of 7m3/h, and is controlled by controlling the power of the water ring vacuum pump 15 The degree of vacuum in the first-stage crystallizer makes the solid content in the first-stage crystallizer 10%. Control the average residence time of the slurry in the first stage crystallizer to be 3h. The slurry in the first-stage crystallizer 12 is injected into the second-stage crystallizer 12 by the screw pump 13, and the solid content in the second-stage crystallizer 12 is controlled at 20% by controlling the power of the water ring vacuum pump 15. And control the average residence time of the slurry in the second stage crystallizer to be 3h. The magma in the second-stage crystallizer 12 is injected into the third-stage crystallizer 12 by the screw pump 13, and the solid content of the third-stage crystallizer is controlled at 30% by controlling the power of the water ring vacuum pump 15. And control the average residence time of crystal slurry in the third stage crystallizer to be 3h, inject the slurry of the third stage crystallizer 12 into the fourth stage crystallizer by the screw pump 13, control the fourth stage by controlling the power of the water ring vacuum pump 15 The vacuum degree of the first-stage crystallizer is at 97kpa, and the average residence time of the slurry in the fourth-stage crystallizer is 3h. The slurry in the fourth-stage crystallizer is injected in the centrifuge 16 by the screw pump 13, and the crystal after the centrifugation passes through normal temperature. After being dried by the blowing air under it, it is packaged and put into storage. The centrifuged mother liquor is pumped back into the fourth-stage crystallizer by the pump 11 to ensure that the solid content in the fourth-stage crystallizer is lower than 50%. The particle size distribution of the obtained product crystals is shown in accompanying drawing 5, and the main particle size of the crystals is 950 microns. See Figure 6 for the crystal appearance. The operation of spraying water in all stages of crystallizers of this process is consistent with embodiment 2.

Example 4

As shown in Figure 4, a vacuum adiabatic flash evaporation continuous crystallization device consists of three crystallizers connected in series; a condenser and a water ring vacuum pump are connected to the top of the crystallizer; a turbidimeter is installed at the bottom of the crystallizer. The material inlet of each level of crystallizer is located at the bottom of the guide tube, which is higher than the stirring paddle of the lower layer; the material outlet is located at the bottom of the crystallizer; the discharge pipe of the last stage of crystallizer is connected to the centrifuge. The upper part of each crystallizer is provided with a spray pipe; the outer wall of the crystallizer is wrapped with a thermal insulation layer. The concentration in the storage tank 10 is 21.5%, and the sodium hydrogen phosphate mother liquor with a temperature of 90 degrees is entered into the first-stage crystallizer 12 by the centrifugal pump 11 according to the flow rate of 7m3/h, and the first-stage crystallizer 12 is controlled by controlling the power of the water ring vacuum pump 15. The solid content in the primary crystallizer 12 is 8%. And control the average residence time of the slurry in the first-stage crystallizer to be 2.5h, the first-stage crystallizer, the slurry in the first-stage crystallizer is injected into the second-stage crystallizer 12 by the screw pump 13, by controlling the water ring The power of type vacuum pump 15 is used to control the solid content in the second-stage crystallizer at 20%, and the average residence time of the slurry in the second-stage crystallizer is 2.5h. The slurry in the second-stage crystallizer is injected into the third-stage crystallizer 12 by the screw pump 13, and the third-stage vacuum degree is controlled at 96kpa by controlling the power of the water ring vacuum pump 15, and the residence time is 2.5h. The slurry in the third stage is poured into the centrifuge 16 for centrifugation, and the centrifuged crystals are air-dried at room temperature before being packaged and put into storage. The centrifuged mother liquor part is pumped back into the third-stage crystallizer through the centrifugal pump 11 to ensure that the solid content in the third-stage crystallizer is lower than 50%. The operation of spraying water in all stages of crystallizers of this process is consistent with embodiment 2.

Claims (6)

1. a multi-stage vacuum adiabatic flash continuous device；Connected by multiple crystallizers；It is characterized in that crystallizer is divided into direct tube section and lower direct tube section；Lower direct tube section diameter is little, and upper direct tube section diameter is big, and two sections of straight tubes are connected by reducing；Upper direct tube section is short, lower straight tube segment length；Crystalliser feet is at the bottom of W type；With guide shell in the direct tube section of crystallizer bottom；Stirring electricity consumption machine is positioned at the top of crystallizer, and stirring paddle uses Double-layer stirring paddle stirring, and the diameter of stirring paddle is less than draft tube diameter, and top layer stirring paddle is higher than guide shell, and bottom stirring paddle is positioned at guide shell bottom.

2. equipment as claimed in claim 1, is characterized in that the diameter ratio of upper direct tube section and lower direct tube section is 1.2～2；The aspect ratio of upper direct tube section and lower direct tube section is 0.5～1.

3. equipment as claimed in claim 1, is characterized in that the guide shell height aspect ratio with lower direct tube section is 0.5～1, and draft tube diameter and lower direct tube section diameter ratio are 0.5～0.9；The ratio of diameter of stirring paddle and draft tube diameter is 0.6～0.95.

4. equipment as claimed in claim 1, is characterized in that crystallizer top is connected to condenser and water-ring vacuum pump；Crystallizer bottom is equipped with transmissometer.

5. equipment as claimed in claim 1, is characterized in that the material inlet of crystallizer at different levels is positioned at bottom guide shell, higher than lower floor's stirring paddle；Discharging opening is positioned at crystalliser feet；The discharge nozzle of afterbody crystallizer is connected with centrifuge.

6. equipment as claimed in claim 1, is characterized in that each crystallizer top is provided with shower；The outer wall of crystallizer is enclosed with heat insulation layer.