An apparatus and process for preparing calcium sulfate whiskers and treating wastewater

Abstract

The present invention relates to a device and process for preparing calcium sulfate whiskers and treating wastewater, including a hydrothermal reaction kettle, a centrifuge, a liquid storage tank, and a wastewater treatment system. The material discharged from the hydrothermal reaction kettle enters the centrifuge. The solid material discharged from the centrifuge is collected as a product, and the liquid material discharged from the centrifuge enters the liquid storage tank, is cooled, and then sent to the wastewater treatment system. The wastewater treatment system includes a precipitation area, a filtration area, and an ion resin exchange area. The wastewater from the centrifuge is sent to the precipitation area for precipitation. The supernatant in the precipitation area enters the filtration area, and the water discharged from the filtration area is sent to the ion resin exchange area. The water discharged from the ion resin exchange area is the treated fresh water. The beneficial effects of the present invention are as follows: The present invention proposes a device and method for preparing calcium sulfate whiskers by hydrothermal reaction, and at the same time provides a corresponding water treatment process for treating the waste liquid caused by hydrothermal reaction. The wastewater treated by the present invention can be reused as fresh water. The present invention has low investment and low operating cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of calcium sulfate whisker production and wastewater re - treatment and recycling, and particularly relates to a device and process for preparing calcium sulfate whiskers and treating wastewater. Background Technique

[0002] Calcium sulfate whiskers have high added value. It is a kind of short fiber grown in the form of single crystals, with a uniform cross - section, a complete appearance and a highly perfect internal structure. Compared with glass fibers, its advantages are that it has extremely high strength, fine dimensions, is more easily combined with organic high - molecular compounds such as resins, rubbers, plastics, etc., and the appearance quality of the product is excellent; it can be widely used in many fields such as automobiles, aerospace, chemical industry, metallurgy, national defense, machinery, electricity, ships, petroleum and building materials.

[0003] Some production units such as enterprises and colleges and universities use gypsum, phosphogypsum, flue gas desulfurization gypsum, etc. as raw materials to prepare calcium sulfate whiskers. The present invention first proposes to prepare calcium sulfate whiskers by hydrothermal reaction. After preparing calcium sulfate whiskers from the hydrothermal reactor, it is necessary to use centrifugal dehydration to separate the solid calcium sulfate whiskers in the hydrothermal reactor from the aqueous solution. In this way, the waste liquid after dehydration of calcium sulfate whiskers will be discharged in the production of calcium sulfate whiskers by the hydrothermal reaction method. The present invention particularly provides a process method for wastewater treatment, regeneration and recycling of the waste liquid for preparing calcium sulfate whiskers. Summary of the Invention

[0004] The purpose of the present invention is to provide a device and process for preparing calcium sulfate whiskers and treating wastewater. The present invention provides a device and method for preparing calcium sulfate whiskers by hydrothermal reaction, and at the same time provides a corresponding wastewater treatment, regeneration and recycling process for the wastewater generated by the hydrothermal reaction.

[0005] To achieve the above - mentioned purpose, the present invention is realized by adopting the following technical solutions:

[0006] A device for preparing calcium sulfate whiskers and treating wastewater includes a hydrothermal reaction kettle, a centrifuge, a liquid storage tank, and a wastewater treatment system. The material discharged from the hydrothermal reaction kettle enters the centrifuge. The solid material discharged from the centrifuge is collected as a product, and the liquid material discharged from the centrifuge enters the liquid storage tank, is cooled and then sent to the wastewater treatment system; the wastewater treatment system includes a precipitation area, a filtration area, and an ion resin exchange area. The wastewater from the centrifuge is sent to the precipitation area for precipitation. The supernatant in the precipitation area enters the filtration area, and the water discharged from the filtration area is sent to the ion resin exchange area. The water discharged from the ion resin exchange area is the treated new water.

[0007] The wastewater treatment system further includes a CO2 aeration tank, which is arranged in the middle section of the filtration area, and the gas introduced into the CO2 aeration tank is a mixed gas of CO2 and air.

[0008] The sedimentation zone includes a stirring tank and a sedimentation tank. There are two sedimentation tanks. The water from the centrifuge is first adjusted for pH value in the stirring tank and then enters the first sedimentation tank for sedimentation. The supernatant of the first sedimentation tank enters the stirring tank again for pH value adjustment and then enters the second sedimentation tank. The supernatant of the second sedimentation tank enters the filtration zone.

[0009] A stirring paddle is provided in the hydrothermal reactor, and the stirring paddle is provided with a double-layer stirring blade, the upper stirring blade is a "cross" shape, and the lower stirring blade is a "U" shape or a "凵" shape. The bottom center position of the lower stirring blade is fixedly connected to the stirring paddle shaft, and a tie rod is provided between the two side wings of the lower stirring blade and the stirring paddle shaft; the outer wall of the hydrothermal reactor is provided with a heating device.

[0010] The heating device is electric heating, thermal oil heating or steam heating.

[0011] A production process for preparing calcium sulfate whiskers and a device for treating wastewater, comprising:

[0012] 1) firstly heating the hydrothermal reaction temperature in the reactor to an initial temperature, and then adding the calcium sulfate whisker preparation raw material to carry out a hydrothermal reaction;

[0013] 2) The slurry after the hydrothermal reaction is discharged into a centrifuge to achieve solid-liquid separation. The solid matter after centrifugal separation is collected as a product, and the slurry enters the stirring tank in the sedimentation area as wastewater;

[0014] 3) Add calcium-based inorganic alkali into the stirring tank and add Ca 2+ Excess SO4 in wastewater 2- Reaction to form CaSO4 precipitate;

[0015] 4) taking the supernatant after the first precipitation, adding inorganic alkali again for stirring, and controlling the pH value of the wastewater to reach 12, and then sending the wastewater into a precipitation tank for secondary precipitation;

[0016] 5) filtering the supernatant after the second precipitation to remove suspended matter in the wastewater;

[0017] 6) The filtered wastewater enters the aeration tank where CO2 gas is introduced. CO2 is introduced into the wastewater, and Ca in the wastewater is 2+ and Mg 2+ With CO3 2- The reaction generates CaCO3 and MgCO3 white precipitates, which remove the Ca 2+ and Mg 2+ The concentration is controlled below 60 mg / L; the wastewater is then filtered to remove the white precipitates of CaCO3 and MgCO3;

[0018] 7) The ion resin exchange process is adopted to remove harmful ions in the wastewater; the wastewater treated by the ion resin exchange is the regenerated fresh water.

[0019] Compared with the existing technologies, the beneficial effects of the present invention are as follows:

[0020] The present invention provides a device and a method for preparing calcium sulfate whiskers by hydrothermal reaction, and at the same time provides a corresponding water treatment process for treating the waste liquid caused by the hydrothermal reaction. The wastewater treated by the present invention can be reused as fresh water. The present invention has low investment and low operation cost. Description of the Drawings

[0021] Figure 1 is the process flow chart of the present invention;

[0022] Figure 2 is the structural schematic diagram of the reaction kettle in the present invention.

[0023] In the figure: 1-hydrothermal reaction kettle, 2-centrifuge, 3-liquid storage tank, 4-stirring tank, 5-first sedimentation tank, 6-second sedimentation tank, 7-filtration area, 8-CO2 aeration tank, 9-ion resin exchange area, 10-fresh water tank, 11-upper stirring paddle, 12-heating device, 13-lower stirring paddle. Detailed Embodiments

[0024] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0025] As Figure 1 、 Figure 2 shown, a device for preparing calcium sulfate whiskers and treating wastewater includes a hydrothermal reaction kettle 1, a centrifuge 2, a liquid storage tank 3, and a wastewater treatment system. The discharge of the hydrothermal reaction kettle 1 enters the centrifuge 2. The solid discharge of the centrifuge 2 is collected as a product, and the liquid discharge of the centrifuge 2 enters the liquid storage tank 3 and is sent to the wastewater treatment system after cooling;

[0026] The wastewater treatment system includes a sedimentation area, a filtration area 7, and an ion resin exchange area 9. The wastewater from the centrifuge 2 is sent to the sedimentation area for sedimentation. The supernatant of the sedimentation area enters the filtration area 7, and the water discharged from the filtration area 7 is sent to the ion resin exchange area 9. The water discharged from the ion resin exchange area 9 is the treated fresh water.

[0027] The wastewater treatment system further includes a CO2 aeration tank 8. The CO2 aeration tank 8 is arranged in the middle section of the filtration area 7, and the gas introduced into the CO2 aeration tank 8 is a mixed gas of CO2 and air.

[0028] The sedimentation zone includes a stirring tank 4 and a sedimentation tank. There are two sedimentation tanks. The water from the centrifuge is first adjusted for pH value in the stirring tank 4 and then enters the first sedimentation tank 5 for sedimentation. The supernatant of the first sedimentation tank 5 enters the stirring tank 4 again for pH value adjustment and then enters the second sedimentation tank 6. The supernatant of the second sedimentation tank 6 enters the filtration zone 7.

[0029] The hydrothermal reactor 1 is provided with a stirring paddle, which is provided with a double-layer stirring paddle, the upper stirring paddle 11 is a "cross" shape, the lower stirring paddle 13 is a "U" shape or a "凵" shape, the bottom center of the lower stirring paddle 13 is fixedly connected to the stirring paddle shaft, and a tie rod is provided between the two side wings of the lower stirring paddle 13 and the stirring paddle shaft; the outer wall of the hydrothermal reactor 1 is provided with a heating device 12. The bottom of the hydrothermal reactor 1 is an arc, and the lower stirring paddle 13 is a "U" shape; the bottom of the hydrothermal reactor 1 is a flat bottom, and the lower stirring paddle 13 is a "凵" shape.

[0030] The cross-shaped upper stirring blade of the present invention can ensure that the 2H2O·CaSO4 molecular clusters are not destroyed, and the sinking speed of the 2H2O·CaSO4 molecular clusters can be controlled by stirring.

[0031] The lower "U"-shaped or "凵"-shaped stirring blades can control and weaken the Brownian motion of molecules such as 1 / 2H2O·CaSO4 and 2H2O·CaSO4; and ensure that all chemical molecules in the solution are in an orderly motion state, with no dead angles in the stirring; and the movement direction is consistent, ensuring the growth of calcium sulfate whisker fibers.

[0032] The heating device 12 is electric heating, thermal oil heating or steam heating.

[0033] The raw materials for preparing calcium sulfate whiskers in the embodiment of the present invention are sintering flue gas semi-dry desulfurization ash and sulfuric acid. After sampling, testing and analysis, the characteristics of the wastewater are as follows:

[0034] Ca 2+ The concentration is 1600-2000mg / L;

[0035] Mg 2+ The concentration is 1200-1800 mg / L;

[0036] K + The concentration is 5500-6000mg / L;

[0037] SO4 2- Concentration is 3500-10000mg / L;

[0038] Cl - The concentration is 7000-8500mg / L;

[0039] Na +The concentration is between 600 - 750 mg / L;

[0040] The total Fe concentration in the wastewater is between 160 - 200 mg / L.

[0041] A production process for a device for preparing calcium sulfate whiskers and wastewater treatment, comprising:

[0042] 1) First, heat the hydrothermal reaction temperature in the reaction kettle to an initial temperature of 45 °C, and then add the raw materials for preparing calcium sulfate whiskers for hydrothermal reaction;

[0043] 2) The slurry after the hydrothermal reaction is discharged into a centrifuge for solid-liquid separation. The solid matter after centrifugal separation is collected as a product, and the slurry enters the stirring tank in the precipitation area as wastewater;

[0044] 3) Add a calcium-based inorganic base to the stirring tank, preferably using CaO or Ca(OH)2, the purpose of which is to add Ca 2+ to react with the excess SO4 2- in the wastewater to generate CaSO4 precipitate;

[0045] 4) Take the supernatant after the first precipitation, add inorganic base again for stirring, and control the pH value of the wastewater to reach 12, then send the wastewater into a precipitation tank for secondary precipitation;

[0046] 5) Filter the supernatant after the second precipitation to remove the suspended matter in the wastewater; Wastewater filtration mainly includes quartz sand filters, activated carbon filters, multi-media filters, iron and manganese removal filters, and precision filters, etc. due to different filtration media. Any of the above filters can be adopted in the present invention, but considering the removal of iron and manganese in the wastewater, it is recommended to use an iron and manganese removal filter.

[0047] 6) The filtered wastewater enters an aeration tank into which CO2 gas is introduced. CO2 is introduced into the wastewater, and Ca 2+ and Mg 2+ in the wastewater react with CO3 2- to generate a small amount or trace amount of white precipitates of CaCO3 and MgCO3 to ensure that the concentrations of Ca 2+ and Mg 2+ in the wastewater are controlled below 60 mg / L; The wastewater after introducing CO2 is filtered again through a precision filter or a pipeline filter to remove a small amount or trace amount of white precipitates of CaCO3 and MgCO3;

[0048] 7) Adopt an ion resin exchange process to remove the relatively high-concentration Cl - ions; After the above wastewater treatment process, the Cl - concentration in the wastewater is between 7000 - 8500 mg / L, belonging to wastewater containing Cl -Wastewater with a relatively high concentration; it also contains a relatively low concentration of Na⁺ / K⁺ / Ca 2+ / Mg 2+ / SO₄ 2- / OH - etc. Therefore, the present invention adopts an ion resin exchange combining primary cation and secondary anion according to the characteristics of the raw water. The wastewater treated by the ion resin exchange is the regenerated fresh water. The concentrations of Na⁺ / K⁺ / Ca 2+ / Mg 2+ / SO₄ 2- / Fe 2+ (Fe 3+ ) / Cl - and other ions in the regenerated fresh water, as detected by a third - party professional testing institution, the results are shown in Table 1:

[0049] Table 1 Summary of detection data (unit: mg / L)

[0050] <![CDATA[Ca 2+ > <![CDATA[Mg 2+ > <![CDATA[K + > <![CDATA[Sodium + > <![CDATA[Cl - > <![CDATA[SO4 2- > TFe Raw water 1600-2000 1200-1800 5500-6000 600-750 7000-8500 3500-10000 160-200 Regenerated fresh water ≤18.6 0.02L ≤158 ≤245 ≤233 ≤65.6 0.03L

[0051] In Table 1: (1) 0.02L means below the method detection limit.

[0052] (2) 0.03L means below the method detection limit.

[0053] The wastewater treated by the above - mentioned wastewater treatment process can be reused to prepare the raw gypsum solution in the process of preparing calcium sulfate whiskers.

[0054] Example 1:

[0055] This example is a set of wastewater treatment facilities specifically for receiving and treating the waste liquid after preparing calcium sulfate whiskers with an actual investment and construction treatment capacity of 2m 3 / h. Its treatment process flow is "alkali addition precipitation + filtration + CO₂ aeration + ion resin exchange system", and the floor area is about 240 square meters. The specific operations are as follows:

[0056] Operation 1: Start the pipeline pump to send the centrifuge effluent into the alkali - adding stirring tank. The volume of the alkali - adding stirring tank is about 3m 3 , the diameter is about 150 cm, and the height is about 180 cm. When the wastewater level reaches about 120 cm, stop the water inlet and, under the stirring state, open the valve of the CaO tank to add it. Continuously observe the change of the pH meter during the addition of CaO powder. When the displayed pH value is greater than 6, stop the addition and close the valve of the CaO tank. Continue stirring for 30 min and then send the wastewater to the first sedimentation tank.

[0057] Operation 2: Primary sedimentation of wastewater: The wastewater after adding alkali enters the first sedimentation tank. The volume of the primary sedimentation tank is about 10m 3 , and the designed wastewater residence time is 240 min.

[0058] Operation 3: The overflow water after precipitation in the first sedimentation tank enters the secondary alkali addition stirring tank. The specifications of the secondary alkali addition stirring tank are the same as those of the primary alkali addition stirring. The operation process is the same as that of Operation 1. In this operation, the secondary alkali addition is NaOH, and the pH value is controlled to reach 12.

[0059] Operation 4: The overflow water after secondary precipitation enters the filter. The filter is a filtration system composed of a three-stage manganese sand filter and a one-stage activated carbon filter. The filtered wastewater enters the CO2 aeration tank.

[0060] Operation 5: The volume of the CO2 aeration tank is 2 m 3 . It is designed to place a CO2 gas pipeline at the bottom of the water tank to form CO2 bubbles in the water. After the wastewater stays in the CO2 aeration tank for 30 minutes, it enters the ion resin exchange system through a primary precision filter.

[0061] Operation 6: The wastewater continuously enters the regenerated fresh water collection tank after passing through the ion resin exchange. Samples are taken and entrusted to a third-party testing agency for analysis of the wastewater and the regenerated fresh water. The analysis results are shown in Table 2.

[0062] Table 2 Summary of Test Data (Unit: mg / L)

[0063] <![CDATA[Ca 2+ > <![CDATA[Mg 2+ > <![CDATA[K + > <![CDATA[Sodium + > <![CDATA[Cl - > <![CDATA[SO4 2- > TFe Before wastewater treatment 1380 692 5230 629 7110 9670 1650 Regenerated fresh water 5.1 0.02L 13.3 63.4 214 0.806 0.03L

[0064] In Table 2: (1) 0.02 L indicates below the method detection limit.

[0065] (2) 0.03 L indicates below the method detection limit.

Claims

1. An apparatus for preparing calcium sulfate whiskers and treating wastewater, characterized in that, It includes a hydrothermal reactor, a centrifuge, a liquid storage tank, and a wastewater treatment system. The discharge of the hydrothermal reactor enters the centrifuge, the solid discharge of the centrifuge is collected as a product, and the liquid discharge of the centrifuge enters the liquid storage tank for cooling and then is sent to the wastewater treatment system; the wastewater treatment system includes a precipitation area, a filtration area, and an ion resin exchange area. The wastewater from the centrifuge is sent to the precipitation area for precipitation, the supernatant of the precipitation area enters the filtration area, the effluent of the filtration area is sent to the ion resin exchange area, and the effluent of the ion resin exchange area is the treated new water; The wastewater treatment system further comprises a CO2 aeration tank, which is arranged in the middle section of the filtration zone, and the gas introduced into the CO2 aeration tank is a mixture of CO2 and air; The sedimentation zone includes a stirring tank and a sedimentation tank. There are two sedimentation tanks. The water from the centrifuge is first adjusted for pH value in the stirring tank and then enters the first sedimentation tank for sedimentation. The supernatant of the first sedimentation tank enters the stirring tank again for pH value adjustment and then enters the second sedimentation tank. The supernatant of the second sedimentation tank enters the filtration zone.

2. The device for preparing calcium sulfate whiskers and treating wastewater according to claim 1, wherein The hydrothermal reactor is provided with a stirring paddle, which is provided with a double-layer stirring paddle blade, the upper stirring paddle blade is a "cross" shape, the lower stirring paddle blade is a "U" shape or a "凵" shape, the bottom center position of the lower stirring paddle blade is fixedly connected to the stirring paddle shaft, and a tie rod is provided between the two side wings of the lower stirring paddle blade and the stirring paddle shaft; the outer wall of the hydrothermal reactor is provided with a heating device.

3. The device for preparing calcium sulfate whiskers and treating wastewater according to claim 2, characterized in that, The heating device is electric heating, thermal oil heating or steam heating.

4. A production process using the device for preparing calcium sulfate whiskers and wastewater treatment as described in any one of claims 1-3, characterized in that, include: 1) First, the hydrothermal reaction temperature in the reactor is heated to the initial temperature, and then the calcium sulfate whisker preparation raw material is added to carry out the hydrothermal reaction; 2) The slurry after the hydrothermal reaction is discharged into the centrifuge to achieve solid-liquid separation. The solid matter after centrifugal separation is collected as the product, and the slurry enters the stirring tank in the sedimentation area as wastewater; 3) Add calcium-based inorganic base into the stirring tank and put in Ca 2+ to react with the excessive SO4 2- in the wastewater to generate CaSO4 precipitate; 4) Take the supernatant after the first precipitation, add inorganic alkali again for stirring, and control the pH value of the wastewater to 12, and then send the wastewater into the precipitation tank for secondary precipitation; 5) Filter the supernatant after the second precipitation to remove suspended matter in the wastewater; 6) The filtered wastewater enters the aeration tank into which CO2 gas is introduced. CO2 is introduced into the wastewater, and Ca 2+ and Mg 2+ in the wastewater react with CO3 2- to form white precipitates of CaCO3 and MgCO3, controlling the concentrations of Ca 2+ and Mg 2+ in the wastewater below 60 mg / L; the wastewater is filtered again to remove the white precipitates of CaCO3 and MgCO3; 7) Use ion resin exchange process to remove harmful ions in wastewater; the wastewater treated by ion resin exchange is regenerated new water.

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