Device for recovering magnesium salt tablets from industrial magnesium salt-containing wastewater

Abstract

The utility model relates to a device for recovering magnesium salt tablets from industrial magnesium salt-containing wastewater, which is characterized in that magnesium salt in industrial waste acid is recovered by adopting an evaporation mode, after the magnesium salt-containing wastewater is filtered and precipitated, a supernatant solution enters an evaporation system to be evaporated and concentrated, a concentrated solution is recovered, cooling and flaking are carried out, and flaked magnesium salt is collected. The evaporation system comprises an evaporator and a condenser. The evaporation system increases the evaporation speed by enhancing evaporation; through the characteristic of normal-pressure evaporation, the problems that the boiling point is increased due to the fact that the solubility of the solution is increased, and energy consumption is increased due to the fact that the requirement for the quality of a heat source is improved in a traditional boiling evaporation process link and the evaporation system works unstably are solved. Compared with the prior art, the energy utilization efficiency is improved, the energy consumption is reduced, the operation stability of the system is improved, and the risk that the evaporator is scaled and blocked is avoided.

Description

TECHNICAL FIELD

[0001] The utility model relates to the recovery technology of magnesium salt especially relates to a device for recycling magnesium salt tablets from industrial wastewater containing magnesium salt. BACKGROUND

[0002] The industrial wastewater containing magnesium salt is mixed wastewater containing a small amount of organic matter and single magnesium salt in the chemical production process, and the conventional recovery process generally has the sedimentation separation method, the magnesium oxide precipitation method and the freeze crystallization method.

[0003] (1) The sedimentation separation method generally needs to add NH4F, and HF is generated in the production process, which has the defects of large investment, large loss and 8 kinds of dangerous products such as HF generated in the process.

[0004] (2) The magnesium oxide precipitation method uses magnesium oxide water reagent for neutralization and precipitation, controls the pH value of the mother liquor to be neutral, and after the sedimentation, the precipitate is magnesium salt. The investment is still high, and sodium salt impurities may be generated in the pH adjustment process, which is not suitable.

[0005] (3) The freeze crystallization method has requirements for the concentration of magnesium salt, and magnesium salt with insufficient solubility cannot form good crystals at low temperature, and the recovered material has low value. INVENTION CONTENTS

[0006] The utility model discloses a device for recycling magnesium salt tablets from industrial wastewater containing magnesium salt, which overcomes the defects of the prior art.

[0007] The utility model discloses a device for recycling magnesium salt tablets from industrial wastewater containing magnesium salt, which overcomes the defects of the prior art.

[0008] The utility model discloses a device for recycling magnesium salt tablets from industrial wastewater containing magnesium salt, which overcomes the defects of the prior art.

[0009] The heat exchanger has a first heat exchange channel and a second heat exchange channel, the evaporator has an inlet, an evaporated gas outlet and an evaporated concentrated liquid outlet, and the filter tank, the condenser, the heat preservation buffer tank and the tabletting machine all include an outlet and an inlet.

[0010] The outlet of the filter tank is connected to the inlet of the evaporator through the first heat exchange channel of the heat exchanger, the evaporated gas outlet of the evaporator is connected to the inlet of the condenser, the evaporated concentrated liquid outlet of the evaporator is connected to the heat preservation buffer tank, the outlet of the condenser is connected to the second heat exchange channel of the heat exchanger or directly drains water, the outlet of the heat preservation buffer tank is connected to the tabletting machine, and the structures are connected through pipelines.

[0011] Further, the filter tank is connected with a water inlet, and the magnesium salt-containing wastewater is first filtered and separated to remove some large-particle impurities after entering the filter tank.

[0012] Further, the heat exchanger is a steam heating heat exchanger, and is selected from any one of a plate heat exchanger, a shell-and-tube heat exchanger, an immersion heat exchanger, and a double-shell heat exchanger.

[0013] Still further, the steam heating heat exchanger is made of polyphenylene sulfide (PPS).

[0014] Further, the evaporator is a columnar tower-shaped spray evaporator.

[0015] Still further, the evaporator is provided with a blowing device for spraying the entering liquid onto the inner wall of the evaporator to accelerate the evaporation speed.

[0016] Still further, the evaporator has a diameter of 0.8-4 m and a height of 8-12 m, and the filler is spherical round filler or corrugated filler.

[0017] Still further, the evaporator is made of modified polypropylene (ppH), and the filler is made of polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF).

[0018] Further, the condenser is a columnar tower-shaped condenser, and is selected from any one of a water-cooled condenser, an air-cooled condenser, an evaporative condenser, and a spray condenser.

[0019] Still further, the condenser has a diameter of 0.8-4 m and a height of 8-12 m, and the filler is spherical round filler or corrugated filler.

[0020] Still further preferably, the condenser is made of glass fiber reinforced polypropylene (FRPP), and the filler is made of polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF).

[0021] Further, the second heat exchange channel inlet of the heat exchanger is connected with the steam supplementing tank in addition to being connected with the outlet of the condenser. In application, the water produced in the condenser is often insufficient in heat to support the heating of the entering water, and thus the heat needs to be supplemented by steam to make the raw water (the upper solution after the treatment of the filter tank) reach the required temperature.

[0022] Further, a centrifugal pump is arranged on the connecting pipeline between the structures to transport the liquid.

[0023] Further, the application provides a use process of the device for recycling magnesium salt tablets from industrial magnesium salt-containing wastewater.

[0024] S1. Pumping the industrial magnesium salt-containing wastewater to be treated into a filter tank to filter and precipitate the magnesium salt-containing wastewater, and taking the upper solution;

[0025] S2. Preheating the upper solution obtained in step S1 in a heat exchanger, and then feeding it into an evaporator to heat and evaporate, to obtain an evaporated concentrated solution and evaporated gas;

[0026] S3. Collecting the evaporated gas obtained in step S2 in a condenser, and collecting the evaporated concentrated solution obtained in step S2 in a heat-insulated buffer tank;

[0027] S4. Heat-insulating storage of the collected evaporated concentrated solution in step S3, and then heat-insulating segmented delivery to a tabletting machine to cool and tablet into magnesium salt tablets.

[0028] Further, in step S1, the flow rate of the industrial magnesium salt-containing wastewater to be treated is 50-4500 L / h, and the magnesium salt contained is magnesium chloride, and the concentration of the magnesium chloride is 8-12%.

[0029] Further, in step S2, the preheating is performed in a steam heating heat exchanger, and the heat source for the preheating is selected from live steam, secondary steam, or water at a temperature of 95°C. The live steam is generated by a steam reheat tank, the secondary steam is obtained from the production line of a factory, and has a temperature insufficient for production line use, and can be used as a heat source for the evaporator when the temperature is above 120 degrees, and the water at a temperature of 95°C is obtained from the production water of a condenser.

[0030] Further, in step S2, the temperature of the preheated upper solution is 85-95°C.

[0031] Further, in step S2, the heating and evaporating process is air blast evaporation for separating the salt and water; the temperature of the air blast evaporation is 90°C, and the air blast amount is 1.5-2.8 times the flow rate of the magnesium salt-containing wastewater, in units of m 3 / h.

[0032] The concentration and crystallization are in a positive pressure air blast evaporation state, which avoids the problems of the traditional boiling evaporation process, such as the increase of the solubility of magnesium chloride with the increase of the temperature, the increase of the boiling point of the magnesium chloride solution, the requirement for a higher temperature heat source to meet the boiling state, the improvement of the quality requirement for the heat source, the improvement of the heat consumption, and the instability of the system operation.

[0033] Further, in step S3, the temperature of the final condensation is 35-45 DEG C. After the temperature is lowered by the condensation tower and the waste heat recovery, the temperature reaches the acceptable inlet water temperature of the sewage biochemical treatment process of a general production enterprise. The condenser is used as a heat source recovery structure, and the water produced after condensation can be reused to heat the inlet water in step S2, thereby reducing the energy consumption. In the whole process, the water in the condenser has a high temperature at the beginning and has a waste heat recovery value. During the recovery process, the temperature of the water gradually decreases, and when the temperature is too low to have a recovery value, the water is no longer reused for heat exchange and is discharged as waste water.

[0034] Further, in step S3, the magnesium salt-containing wastewater to be treated is concentrated by 1.5-5.8 times after being heated and evaporated, that is, the volume of the concentrated wastewater is reduced by 1.5-5.8 times compared with the original water. The evaporation concentrated liquid obtained in step S3 is kept warm by step S4 and then is transported to a tabletting machine to be frozen and cut into pieces, so that magnesium salt tablets are finally obtained; the magnesium salt tablets are magnesium chloride hexahydrate crystals.

[0035] Compared with the prior art, the magnesium salt recovery process has the following beneficial effects:

[0036] (1) The magnesium salt recovery process adopts the normal pressure evaporation mode, does not need to reach the boiling point of the solution in the conventional boiling evaporation, and avoids the difficulty that the solubility increases and the boiling point rises as the temperature increases.

[0037] (2) The equipment used in the magnesium salt recovery process is made of high-temperature-resistant and corrosion-resistant plastic material, thereby effectively solving the problems of fast corrosion and short service life of the metal material.

[0038] (3) In the heating and evaporation process of the magnesium salt recovery process, a circulating pump is used to continuously spray the filtrate, and ventilation is performed, so that the contact area of the two is increased, heat exchange is sufficient, and the heat loss is small.

[0039] (4) The magnesium salt recovery process recovers the heat of the once-condensed water, effectively reduces the heat consumption by 20%-50%, and saves the cost of magnesium salt recovery.

[0040] (5) The tablets obtained in the magnesium salt recovery process are magnesium chloride hexahydrate tablets, and no other by-products are generated. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 The figure is a process flow diagram for recovering magnesium salt from industrial magnesium salt-containing wastewater;

[0042] The marks in the figure represent:

[0043] 1 is a filter tank, 2 is a heat exchanger, 3 is an evaporator, 4 is a condenser, 5 is a heat preservation buffer tank, and 6 is a tabletting machine. DETAILED DESCRIPTION

[0044] In order for those skilled in the art to better understand the technical solutions of the present application, the present application will be described in detail below in conjunction with specific embodiments. It should be pointed out that the following embodiments will help those skilled in the art to further understand the present application, but do not limit the present application in any form. It should be pointed out that, for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made. These all belong to the protection scope of the present application.

[0045] In the description of the present application, it should be pointed out that the terms "upper", "lower", "inner", "outer", "front end", "rear end", "two ends", "one end", "the other end" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance. In the description of the present application, it should be pointed out that, unless otherwise explicitly specified and limited, the terms "mounting", "provided with", "connection" and the like should be understood broadly, for example, "connection" can be fixed connection, can also be detachable connection, or integral connection; can be mechanical connection, can also be electrical connection; can be directly connected, can also be indirectly connected through an intermediate medium, can be the communication between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0046] Example 1

[0047] The equipment processing capacity is 50L / h, the temperature is 30℃, the wastewater containing 12% magnesium chloride and a small amount of low-boiling-point organic matter.

[0048] The process for treating wastewater comprises the following steps:

[0049] S1. Filtering and precipitating the above-mentioned industrial magnesium salt-containing wastewater to obtain an upper solution;

[0050] S2. Controlling the evaporation air volume to be 75-100m 3 / h, heating the temperature of the filtrate through the evaporation heating heat exchanger to be 95℃, the heat source being steam, hot water with a temperature of 95℃ and the heat source reused by the condenser; the heated filtrate enters the evaporator, the temperature in the evaporator is controlled to be 90℃, and the filtrate is concentrated in the evaporator by about 2.9 times ((47%-12%) / 12%) volume to reach a solid-containing solution with a content of about 47%, i.e. the evaporation concentrated liquid.

[0051] S3. The evaporated gas is condensed, and the final temperature of the circulating system is about 35°C (the initial condensed temperature in the condenser is 60-70°C, and after heat recovery, the temperature in the circulating system reaches about 35°C). About 3%-5% of the tail gas overflows, the collected condensed water is directly discharged after treatment in a biochemical tank, and the concentrated solution is stirred in a heat preservation buffer tank and then continuously transported to a freezing tablet machine through a heat preservation pipeline to obtain magnesium chloride tablets.

[0052] The total steam consumption in the process is 0.4-0.45 tons of steam per ton of wastewater, and 255 kg of magnesium salt is recovered per ton of wastewater.

[0053] Example 2

[0054] The equipment processing capacity is 1400 L / h, the temperature is 30°C, and the solution contains 8% magnesium chloride and a small amount of organic matter.

[0055] The process for treating wastewater includes the following steps:

[0056] (1) The above-mentioned industrial wastewater containing magnesium salt is sequentially filtered to obtain a filtrate;

[0057] (2) The evaporation air volume is controlled to be 2600-3900 m 3 / h, the temperature of the filtrate heated by the evaporation heating heat exchanger is 95°C, the heat source is steam at 135°C and the heat source recycled from the condenser; the heated filtrate enters the evaporator, and the temperature in the evaporator is controlled to be 90°C. The filtrate is concentrated by about 5.87 times in the evaporator, evaporated to crystallize, and the solution density is about 1.85 g / cm 3 .

[0058] (3) The evaporated gas is condensed, and the final temperature of the circulating system is about 35°C (the initial condensed temperature in the condenser is 60-70°C, and after heat recovery, the temperature in the circulating system reaches about 35°C). The condensed water enters a Fenton processor for treatment; the concentrated solution is stored in a heat preservation buffer tank and then continuously transported to a freezing tablet machine through a heat tracing pipeline to obtain magnesium chloride hexahydrate tablets.

[0059] The total steam consumption in the process is 0.35-0.45 tons of steam per ton of wastewater, and 5.87 times of concentration can be finally achieved, and 170 kg of magnesium salt is recovered per ton of wastewater.

[0060] Example 3

[0061] The equipment processing capacity is 4500 L / h, the temperature is 30°C, and the solution contains 8% magnesium chloride and a small amount of organic matter.

[0062] The process for treating wastewater includes the following steps:

[0063] (1) The industrial magnesium salt containing wastewater is subjected to air floatation and precipitation to obtain a relatively clear upper liquid;

[0064] (2) The evaporation blast volume is controlled to be 9000-12000 m 3 / h, the temperature of the filtrate heated by the evaporation heating heat exchanger is 95℃, the heat source is 180℃ steam and the heat source recycled by the condenser; the heated filtrate enters the evaporator, the temperature in the evaporator is controlled to be 95℃, and the filtrate can be concentrated by about 4.5 times in the evaporator to reach a 45% magnesium chloride containing solid solution, i.e. the evaporation concentrated liquid.

[0065] (3) The evaporation gas is condensed, the final temperature of the recycled system after condensation is about 35℃ (the initial condensation temperature in the condenser is 60-70 degrees, and after heat recovery, the temperature in the recycled system reaches about 35 degrees), the condensed water is collected and used as an acid pickling cleaning agent for equipment surfaces in the factory; the concentrated liquid enters the heat preservation buffer tank for storage, is continuously conveyed to the frozen tablet machine through a pipeline, and magnesium chloride hexahydrate tablets are obtained, and the final magnesium salt recovery efficiency is about 220 kg / ton of wastewater.

[0066] The total steam consumption of the process is 0.5-0.6 tons of steam / ton of water, the final concentration can reach 4.5 times, and the final magnesium salt recovery efficiency is about 220 kg / ton of wastewater.

[0067] In summary, the process for recycling magnesium salt tablets from industrial magnesium salt containing wastewater provided by the utility model has the working principle that after the magnesium salt containing wastewater to be treated is filtered, the filtrate is pumped into an evaporation system. The evaporation system comprises an evaporator and a condenser. The evaporator sprays the filtrate while utilizing the convection of the blast to increase the specific surface area and accelerate the evaporation speed. The heat of the condenser water is recycled by a recycling heat exchanger and used for heating the filtrate, so that the energy consumption is effectively reduced by 20%-50%. The magnesium salt and the solvent are separated and recycled respectively by using the anti-corrosion evaporator. The whole evaporation process is atmospheric evaporation, which solves the problems of the traditional boiling evaporation process, such as the increase of the solubility of magnesium salt with the increase of the temperature, the increase of the boiling point, the increase of the requirement for the heat source, the increase of the energy consumption, and the instability of the whole evaporation system.

[0068] The above description of the embodiments is for the convenience of the ordinary skilled person in the art to understand and use the utility model. Those skilled in the art can obviously make various modifications to the embodiments and apply the general principles described herein to other embodiments without having to go through creative labor. Therefore, the utility model is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the utility model should be within the protection scope of the utility model.

Claims

1. An apparatus for recovering magnesium salt tablets from industrial magnesium salt-containing wastewater, characterized in that, The device comprises the following structures: a filter tank (1), a heat exchanger (2), an evaporator (3), a condenser (4), a heat preservation buffer tank (5), and a flake forming machine (6). The heat exchanger (2) has a first heat exchange channel and a second heat exchange channel, the evaporator (3) has one inlet, one evaporated gas outlet, and one evaporated concentrated liquid outlet, and the filter tank (1), the condenser (4), the heat preservation buffer tank (5), and the flake forming machine (6) all comprise an outlet and an inlet. The filter tank (1) is connected to a water inlet; the outlet of the filter tank (1) is connected to the inlet of the evaporator (3) through the first heat exchange channel of the heat exchanger (2); the evaporated gas outlet of the evaporator (3) is connected to the inlet of the condenser (4), and the evaporated concentrated liquid outlet of the evaporator (3) is connected to the heat preservation buffer tank (5); the outlet of the condenser (4) is connected to the second heat exchange channel of the heat exchanger (2), or directly drains water; the outlet of the heat preservation buffer tank (5) is connected to the flake forming machine (6); the structures are connected through pipelines; and the inlet of the second heat exchange channel of the heat exchanger is connected to a steam heat supplement tank in addition to the outlet of the condenser (4).

2. An apparatus for recovering magnesium salt tablets from industrial wastewater containing magnesium salt according to claim 1, characterized by The heat exchanger (2) is a steam heating heat exchanger, which is selected from any one of a plate heat exchanger, a shell-and-tube heat exchanger, an immersion heat exchanger, and a double-shell heat exchanger.

3. An apparatus for recovering magnesium salt tablets from industrial wastewater containing magnesium salt according to claim 2, characterized by The steam heating heat exchanger is made of polyphenylene sulfide.

4. The apparatus for recovering magnesium salt tablets from wastewater of industrial magnesium salt according to claim 1, characterized by, The evaporator (3) is a columnar tower-shaped spray evaporator.

5. The apparatus for recovering magnesium salt tablets from wastewater of industrial magnesium salt according to claim 1, characterized by, The evaporator (3) is provided with a blowing device for spraying the entering liquid onto the inner wall of the evaporator.

6. The apparatus for recovering magnesium salt tablets from wastewater of industrial magnesium salt according to claim 1, characterized by, The diameter of the evaporator (3) is 0.8-4 m, the height is 8-12 m, and the filler is spherical round filler or corrugated filler.

7. The apparatus for recovering magnesium salt tablets from wastewater of industrial magnesium salt according to claim 1, characterized by, The evaporator (3) is made of modified polypropylene, and the filler in the evaporator (3) is made of polytetrafluoroethylene or polyvinylidene fluoride.

8. The apparatus for recovering magnesium salt tablets from wastewater of industrial magnesium salt according to claim 1, characterized by, The condenser (4) is a columnar tower-shaped condenser, which is selected from any one of a water-cooled condenser, an air-cooled condenser, an evaporative condenser, and a spray condenser.

9. The apparatus for recovering magnesium salt tablets from wastewater of industrial magnesium salt according to claim 1, characterized by, The diameter of the condenser (4) is 0.8-4 m, the height is 8-12 m, and the filler is spherical round filler or corrugated filler.

10. The apparatus for recovering magnesium salt tablets from wastewater of industrial magnesium salt according to claim 1, characterized by, The condenser (4) is made of glass fiber reinforced polypropylene, and the filler in the condenser (4) is made of polytetrafluoroethylene or polyvinylidene fluoride.

Images