Absorption tower defoaming system with foam discharge function

Abstract

The application discloses an absorption tower defoaming system with a foam discharge function, which is used for solving the problems of unstable operation, equipment corrosion and secondary pollution caused by foam accumulation in a wet desulfurization process. The system comprises an absorption tower, a foam collecting tank and a foam breaking device, a plurality of groups of rotating defoaming grid mechanisms are uniformly and interval arranged on the side wall of the absorption tower along the circumference, and the defoaming grids are synchronously and homodirectionally rotated by driving a variable frequency electrode outside. The defoaming grids cut and break the foam by means of physics, and at the same time, the rotation of the defoaming grids drives the surface layer of slurry to form a directional circular flow, so that the foam continuously gathers to the defoaming area and is efficiently removed. The application adopts a pure mechanical defoaming mode, does not need to rely on chemical agents, and has the advantages of high efficiency, low energy consumption, energy saving and environmental protection and the like. In the preferred scheme, a PLC control system is additionally arranged, the rotating speed of the defoaming grids is dynamically adjusted by monitoring the foam thickness in real time, and the system is further adapted to complex working conditions. The equipment can be widely applied to the foam treatment of desulfurization absorption towers in fields such as coal-fired power plants and chemical plants.

Description

Technical Field

[0001] This application relates to the field of flue gas desulfurization technology in coal-fired power plants, specifically to an absorber tower defoaming system with foam discharge function, which is suitable for the removal and recovery of foam in absorber towers in wet desulfurization processes. Background Technology

[0002] In wet flue gas desulfurization (FGD) processes, a large amount of foam is often generated during the contact between the slurry and flue gas in the absorber tower. This problem has become a key factor restricting the stable operation of the desulfurization system. The foam generation mainly stems from the following aspects: First, solid impurities such as fly ash and unburned carbon particles in the flue gas significantly reduce the surface tension of the slurry after entering it; second, substances such as sulfites generated during the desulfurization reaction have surface-active properties; and third, organic pollutants in the process water and organic acid additives added to improve desulfurization efficiency all exacerbate foam formation.

[0003] The foam generated in the absorption tower has a serious impact on the quality of desulfurized gypsum: the foam carries unreacted limestone, fly ash and other impurities into the gypsum slurry system, resulting in a decrease in the CaSO4·2H2O content and an increase in the impurity content in the final gypsum product; the presence of foam interferes with the normal growth process of gypsum crystals, leading to the formation of irregular small-particle crystals. This crystal structure not only affects the dewatering performance of gypsum, but also reduces its physical properties such as compressive strength; the foam has the characteristic of enriching Cl-, which will significantly increase the soluble chloride content in gypsum, seriously affecting the applicability of gypsum as a building material; after the foam enters the gypsum hydrocyclone and vacuum belt conveyor, it will reduce the dewatering efficiency and increase the moisture content of the filter cake.

[0004] Currently, the most commonly used foam control method in industry is chemical defoaming. Although this method is effective, long-term use will lead to the accumulation of defoamer in the slurry. Organosilicon defoamers will remain in the gypsum, affecting the performance of gypsum products. Excessive use may lead to an increase in the COD of the slurry, which may in turn promote the generation of more foam, forming a vicious cycle.

[0005] The above methods have failed to fundamentally solve the foam problem. Therefore, it is urgent to develop a new defoaming technology that can effectively control foam without negatively affecting the quality of desulfurized gypsum. This is of great significance for improving the comprehensive utilization value of desulfurization by-products. Summary of the Invention

[0006] In view of the above-mentioned technical problems existing in the prior art, the purpose of this application is to provide an absorption tower defoaming system with foam discharge function. This application fundamentally solves the problem of foam affecting system operation and gypsum quality in wet desulfurization process by combining innovative mechanical defoaming with foam discharge.

[0007] The technical solution adopted in this application is as follows:

[0008] A defoaming system for an absorption tower with foam discharge function includes an absorption tower, a foam collection tank, and a foam breaking device. Multiple sets of rotating foam breaking grid mechanisms are evenly spaced along the circumference of the side wall of the absorption tower, and the rotating foam breaking grid mechanisms are located above the slurry inside the absorption tower. A foam diversion system is provided on the side of the absorption tower and is connected to the foam collection tank through the foam diversion system.

[0009] The rotary bubble-breaking grid mechanism includes a bubble-breaking grid and a rotary drive system. The bubble-breaking grid is fixedly installed on the inner side wall of the absorption tower through the rotary drive system. Under the driving action of the rotary drive system, the bubble-breaking grid rotates to cut and break the foam in the absorption tower.

[0010] The foam diversion system is used to divert unbroken foam in the absorption tower into the foam collection tank;

[0011] The foam breaking device is used to further break up the discharged foam collected in the foam collection tank.

[0012] Furthermore, the rotary drive system includes a central rotating shaft and a variable frequency motor. One end of the central rotating shaft is fixedly connected to the bubble-breaking grid, and the other end of the central rotating shaft extends to the outside of the absorption tower and is fixedly connected to the variable frequency motor. The bubble-breaking grid is rotated by the driving action of the variable frequency motor.

[0013] The bubble-breaking grid includes a corrosion-resistant metal frame with two layers of grid strips arranged on the metal frame. The two layers of grid strips are arranged in an alternating pattern to form a grid structure. In the structure of the grid strips in the same layer, the spacing between the grid strips is 30-80mm.

[0014] Furthermore, at least three sets of rotating bubble-breaking grid mechanisms are provided at intervals on the side wall of the absorption tower.

[0015] Furthermore, the foam diversion system includes an inclined overflow hole opened on the side wall of the absorption tower. The overflow hole is connected to the upper end of the diversion pipe, and the lower end of the diversion pipe is connected to the foam collection tank. The diversion pipe is an inclined pipe. The diameter of the overflow hole is 150-400mm.

[0016] Furthermore, the overflow hole is equipped with an adjustable baffle valve with an adjustable opening to control the amount of foam flowing out; the overflow hole is equipped with a flushing water system to prevent foam from clogging the guide pipe.

[0017] Furthermore, the foam collection tank contains a liquid-sealed slurry layer to prevent flue gas from leaving the absorption tower through the diversion system.

[0018] Furthermore, the foam defoaming device employs one or both of the following: an ultrasonic defoamer and a heating device, for eliminating discharged foam; a mechanical stirrer is installed inside the foam collection tank to assist in defoaming, while the stirring of the mechanical stirrer prevents slurry sedimentation.

[0019] It also includes a reuse pump, which is used to pump the defoamed slurry in the foam collection tank back to the absorption tower or the reuse water tank, or to discharge it to the wastewater treatment system.

[0020] Furthermore, it also includes a PLC control system and a foam thickness measuring instrument installed in the absorption tower. The foam thickness measuring instrument is connected to the rotary drive system and the adjustable baffle valve via the PLC control system. When the monitored foam thickness is lower than the set value range, the PLC control system provides feedback and adjusts the rotary drive system to increase the speed of the foam breaking grid and increase the opening of the adjustable baffle valve. When the monitored foam thickness is higher than the set value range, the PLC control system provides feedback and adjusts the rotary drive system to decrease the speed of the foam breaking grid and decrease the opening of the adjustable baffle valve.

[0021] The process of the absorber tower defoaming system with foam discharge function includes the following steps:

[0022] S1 Primary Defoaming Stage: Multiple sets of rotating defoaming grid mechanisms rotate synchronously in the same direction. Rotation in the same direction means rotating counterclockwise or clockwise. The rotating defoaming grid directly cuts and breaks most of the foam on the surface of the slurry in the absorption tower. The centrifugal force generated by the rotation accelerates gas-liquid separation, and the gas is discharged from the top of the absorption tower.

[0023] S2 Foam Guiding Stage: Under the action of the unidirectional rotation of the multiple sets of rotating foam breaking grids, the slurry surface layer is driven to form a directional circulation. Unbroken foam moves with the circulation to the overflow hole area. The micro-positive pressure condition in the absorption tower promotes the foam to enter the overflow hole.

[0024] S3 Foam Discharge Treatment Stage: The foam flowing out through the overflow hole enters the foam collection tank. The foam collection tank contains a liquid seal slurry layer to prevent flue gas leakage. The foam structure is completely destroyed by ultrasonic and / or heating and / or mechanical stirring. The resulting slurry liquid can be reused in the absorption tower.

[0025] Furthermore, the rotational speed of the bubble-breaking grid is 5-20 rpm, and the pressure of the micro-positive pressure inside the absorption tower is 50-200 Pa.

[0026] Compared with the prior art, the beneficial effects achieved by this application are:

[0027] 1. By employing a three-stage defoaming mode of "mechanical defoaming + directional flow guidance + external discharge treatment," the foam removal rate is comprehensively improved. This combines methods such as using a foam-breaking grid to remove most of the foam, an overflow system to remove residual foam, and external treatment to ensure thorough defoaming. This achieves complete foam removal, avoids chemical defoamer contamination of the gypsum system, and reduces the impact of foam on the operation of the desulfurization system.

[0028] 2. An innovative foam guiding mechanism ensures that residual foam inside the absorption tower is discharged in a timely manner. The rotation of the grid drives the foam layer to circulate, and the inclined overflow holes are designed in conjunction with the rotation direction to create a slight positive pressure inside the absorption tower, promoting foam discharge. This results in low energy consumption and high efficiency.

[0029] 3. A complete foam recycling system, which ensures no leakage of flue gas through liquid seal design, guarantees treatment effect through multi-mode defoaming, and achieves zero emissions by reusing the liquid phase after foam treatment, making full use of desulfurization absorbent and gypsum seed crystals, while saving water resources. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of an absorption tower defoaming system with foam discharge function.

[0031] In the diagram: 1. Foam grid; 2. Foam diversion system; 3. Foam collection tank; 4. Foam disposal device; 5. Reuse pump. Detailed Implementation

[0032] The present application will be further described below with reference to specific embodiments, but the scope of protection of the present application is not limited thereto.

[0033] Example: Control Figure 1

[0034] A defoaming system for an absorption tower with foam discharge function includes an absorption tower, a foam collection tank 3, and a foam breaking device 4. At least three sets of rotating foam breaking grid mechanisms are evenly spaced along the circumference of the side wall of the absorption tower, and the rotating foam breaking grid mechanisms are located above the slurry inside the absorption tower. A foam diversion system is provided on the side of the absorption tower and is connected to the foam collection tank through the foam diversion system.

[0035] A rotary bubble-breaking grid mechanism includes a bubble-breaking grid 1 and a rotary drive system. The bubble-breaking grid 1 is fixedly installed on the inner side wall of the absorption tower via the rotary drive system. Under the driving action of the rotary drive system, the bubble-breaking grid 1 rotates, cutting and breaking the foam inside the absorption tower. The rotary drive system includes a central rotating shaft and a variable frequency motor. One end of the central rotating shaft is fixedly connected to the bubble-breaking grid 1, and the other end of the central rotating shaft extends to the outside of the absorption tower and is fixedly connected to the variable frequency motor. The variable frequency motor drives the bubble-breaking grid 1 to rotate.

[0036] In this application, the bubble-breaking grid 1 includes a corrosion-resistant metal frame, on which two layers of grid strips are arranged. The two layers of grid strips are arranged in an interlaced manner to form a grid structure. In the structure of the grid strips in the same layer, the spacing between the grid strips is 30-80mm.

[0037] A foam diversion system is used to divert unbroken foam from the absorption tower into a foam collection tank 3. In this application, the foam diversion system includes an inclined overflow hole formed on the side wall of the absorption tower. The overflow hole is connected to the upper end of a guide pipe, and the lower end of the guide pipe is connected to the foam collection tank 3. The guide pipe is an inclined pipe. The diameter of the overflow hole is 150-400 mm.

[0038] Furthermore, the overflow hole is equipped with an adjustable baffle valve with an adjustable opening to control the amount of foam flowing out; the overflow hole is equipped with a flushing water system to prevent foam from clogging the guide pipe.

[0039] Foam breaking device 4 is used to further break up the discharged foam collected in foam collection tank 3. Foam breaking device 4 uses one or both of the following: ultrasonic defoamer and heating device, to eliminate discharged foam; a mechanical agitator is installed in the foam collection tank to assist in defoaming, and at the same time, the agitation of the mechanical agitator prevents slurry sedimentation.

[0040] The foam collection tank 3 contains a liquid seal slurry layer to prevent flue gas from leaving the absorption tower through the diversion system. The height of the liquid seal slurry layer can be 5-15cm.

[0041] The system of this application also includes a reuse pump 5, which is used to pump the defoamed slurry in the foam collection tank 3 back to the absorption tower or the reuse water tank, or discharge it to the wastewater treatment system.

[0042] The system of this application can also be equipped with a PLC control system, and a foam thickness measuring instrument is installed in the absorption tower. The foam thickness measuring instrument is connected to the variable frequency motor and adjustable baffle valve of the rotary drive system through the PLC control system. When the monitored foam thickness is lower than the set value range, the PLC control system feeds back and increases the output power of the variable frequency motor to increase the speed of the foam breaking grid and increases the opening of the adjustable baffle valve. When the monitored foam thickness is higher than the set value range, the PLC control system feeds back and decreases the output power of the variable frequency motor to decrease the speed of the foam breaking grid and decreases the opening of the adjustable baffle valve.

[0043] The process of the absorber tower defoaming system with foam discharge function includes the following steps:

[0044] S1 Primary Defoaming Stage: The defoaming grids 1 of multiple sets of rotating defoaming grid mechanisms rotate synchronously in the same direction. Rotation in the same direction means rotating counterclockwise or clockwise. The rotating defoaming grids 1 directly cut and break most of the foam on the surface of the slurry in the absorption tower. The centrifugal force generated by the rotation accelerates the gas-liquid separation, and the gas is discharged from the top of the absorption tower.

[0045] S2 Foam Guiding Stage: Under the action of the unidirectional rotation of the defoaming grid 1 of the multiple sets of rotating defoaming grid mechanisms, the surface of the slurry is driven to form a directional circulation. The unbroken foam moves with the circulation to the overflow hole area. The micro-positive pressure condition in the absorption tower promotes the foam to enter the overflow hole.

[0046] S3 Foam Discharge Treatment Stage: The foam flowing out through the overflow hole enters the foam collection tank 3. The foam collection tank 3 contains a liquid seal slurry layer to prevent flue gas leakage. The foam structure is completely destroyed by ultrasonic and / or heating and / or mechanical stirring. The resulting slurry liquid can be reused in the absorption tower.

[0047] The rotation speed of the bubble-breaking grid 1 is 5-20 rpm, and the pressure of the micro-positive pressure inside the absorption tower is 50-200 Pa.

[0048] Example 1

[0049] This embodiment provides an absorption tower defoaming system with foam discharge function: the defoaming grid is made of 316L stainless steel, with a grid spacing of 50mm and a rotation speed of 10-15rpm. The overflow hole diameter is 200mm, the inclination angle is 45°, and four overflow holes are evenly spaced along the circumference of the absorption tower sidewall. Each overflow hole is connected to a foam collection tank through a guide pipe; the foam collection tank has a volume of 5m³. 3 Equipped with an ultrasonic defoamer (2kW power), liquid seal height of 8cm, and a reuse pump flow rate of 10m³ / h. 3 / h. Testing showed that the defoaming efficiency of the system in this application reached 95.2%.

[0050] The contents described in this specification are merely an enumeration of the implementation forms of the application concept, and the scope of protection of this application should not be regarded as limited to the specific forms described in the embodiments.

Claims

1. A defoaming system for an absorption tower with foam discharge function, characterized in that, It includes an absorption tower, a foam collection tank (3) and a foam breaking device (4). Multiple sets of rotating foam breaking grid mechanisms are evenly spaced along the circumference of the side wall of the absorption tower. The rotating foam breaking grid mechanisms are located above the slurry inside the absorption tower. A foam diversion system is provided on the side of the absorption tower and is connected to the foam collection tank through the foam diversion system. The rotary bubble-breaking grid mechanism includes a bubble-breaking grid (1) and a rotary drive system. The bubble-breaking grid (1) is fixedly installed on the inner side wall of the absorption tower through the rotary drive system. Under the driving action of the rotary drive system, the bubble-breaking grid (1) rotates to cut and break the foam in the absorption tower. The foam diversion system is used to divert unbroken foam in the absorption tower into the foam collection tank (3); The foam breaking device (4) is used to further break up the outflowing foam collected in the foam collection tank (3).

2. The defoaming system of the absorption tower with foam discharge function as described in claim 1, characterized in that, The rotary drive system includes a central rotating shaft and a variable frequency motor. One end of the central rotating shaft is fixedly connected to the bubble-breaking grid (1), and the other end of the central rotating shaft extends to the outside of the absorption tower and is fixedly connected to the variable frequency motor. The bubble-breaking grid (1) is rotated by the driving action of the variable frequency motor. The bubble-breaking grid (1) includes a corrosion-resistant metal frame, on which two layers of grid strips are arranged. The two layers of grid strips are arranged in an interlaced manner to form a grid structure. In the structure of the grid strips in the same layer, the spacing between the grid strips is 30-80mm.

3. The defoaming system of the absorption tower with foam discharge function as described in claim 1, characterized in that, The absorption tower sidewall is provided with at least three sets of rotating bubble-breaking grid mechanisms at intervals.

4. The defoaming system of an absorption tower with foam discharge function as described in claim 1, characterized in that, The foam diversion system includes an inclined overflow hole opened on the side wall of the absorption tower. The overflow hole is connected to the upper end of the diversion pipe, and the lower end of the diversion pipe is connected to the foam collection tank (3). The diversion pipe is an inclined pipe. The diameter of the overflow hole is 150-400mm.

5. The defoaming system of an absorption tower with foam discharge function as described in claim 4, characterized in that, The overflow hole is equipped with an adjustable baffle valve with an adjustable opening to control the amount of foam flowing out; the overflow hole is equipped with a flushing water system to prevent foam from clogging the guide pipe.

6. The defoaming system of the absorption tower with foam discharge function as described in claim 1, characterized in that, The foam collection tank (3) contains a liquid seal slurry layer to prevent flue gas from leaving the absorption tower through the diversion system.

7. The defoaming system of the absorption tower with foam discharge function as described in claim 1, characterized in that, The foam defoaming device (4) uses one or both of the following: an ultrasonic defoamer and a heating device, to eliminate the discharged foam; a mechanical stirrer is installed in the foam collection tank to assist in defoaming, and at the same time, the stirring of the mechanical stirrer prevents the slurry from settling. It also includes a reuse pump (5), which is used to pump the defoamed slurry in the foam collection tank (3) back to the absorption tower or the reuse water tank, or discharge it to the wastewater treatment system.

8. The defoaming system of the absorption tower with foam discharge function as described in claim 4, characterized in that, It also includes a PLC control system and a foam thickness measuring instrument installed in the absorption tower. The foam thickness measuring instrument is connected to the rotary drive system and the adjustable baffle valve via the PLC control system. When the monitored foam thickness is lower than the set value range, the PLC control system provides feedback and adjusts the rotary drive system to increase the speed of the foam breaking grid and increase the opening of the adjustable baffle valve. When the monitored foam thickness is higher than the set value range, the PLC control system provides feedback and adjusts the rotary drive system to decrease the speed of the foam breaking grid and decrease the opening of the adjustable baffle valve.

Images