Vertical flow air flotation integrated machine

1、 Introduction to Vertical Flow Air Floatation Integrated Machine
At present, the country is paying more and more attention to environmental protection work and paying more and more attention to environmental pollution issues. Wastewater treatment, as a long-standing and difficult problem, has been troubling various enterprises, especially some small and medium-sized enterprises such as papermaking, printing and dyeing, petroleum, chemical, pharmaceutical and other enterprises. Due to financial and technological constraints, they cannot afford to import equipment and immediately invest huge amounts of money to install treatment equipment. Often, they also have to start and stop due to huge operating costs to cope with inspections by environmental protection departments. In response to the current situation, our company has referred to advanced foreign technologies and developed the DAF series dissolved air flotation technology and complete equipment, which has higher efficiency, lower cost, and simpler maintenance and operation. Its processing efficiency and effectiveness are far higher than traditional conventional air flotation, and it is a replacement product for various types of air flotation.
2、 Structural characteristics and working principle of vertical flow air flotation integrated machine
1. Structural composition: ① Tank body ② Microbubble generator ③ Container device ④ Drug dispensing device ⑤ Mud discharge tank ⑥ Water outlet pipe 2. Structural features: Due to the manufacturing characteristics of the tank body, it adopts a high-efficiency gas dissolution mechanism. Through the separated microbubble generator, the raw water, dissolved water, and drugs (with a tangential vortex entering) can be quickly combined, released, flocculated, floated, and the microbubbles are uniform and dense. When reaching the middle and upper parts of the tank body, the buoyancy speed tends to be stable and zero speed, forming a three-dimensional microcirculation state, ensuring that microbubbles fully contact and combine with the flocs in the wastewater. Whether in the process of binding or already bound flocs, their binding will not be disrupted by external forces, and the floc floating layer is stable.
3、 Principle of Vertical Flow Air Floatation Integrated Machine
Drug dispensing device: The drug is pumped through a flow meter, dissolution, filtration, and rubber plate (according to a certain process ratio) to the microbubble generator in the air flotation tank. At the same time, the raw water and dissolved air water (to reduce treatment load, dissolved air water can be used as raw water) enter the microbubble generator separately. Under the relatively stable pressure effect of the water dissolution device, high-density dissolved air water can quickly release pressure and rise with the medicine and raw water, ensuring that microbubbles fully contact and combine with the flocs in the wastewater. When microbubbles drive the suspended solids to float up to the middle and upper parts, a stable floating layer is formed, and the three-dimensional microcirculation also tends to be stable. The suspended solids are not easily damaged by external forces during the bonding process. Under the three-dimensional microcirculation effect, the clear water clarifies in the lower part of the tank body. Store around the area and discharge through a clear water outlet. When the flocculants form a stable floating layer on the surface of the tank and gradually rise to a certain level, they are naturally discharged from the inclined sludge discharge tank without the need for additional power equipment. When regular discharge is required, close all outlet (clear water valve) valves, and the liquid level can rise, completely removing the floating layer. In addition, there is no drain valve at the bottom, and the sediment at the bottom can be regularly drained.
4、 Key technology and characteristics of vertical flow air flotation integrated machine
1. High processing efficiency
The density is higher than 1012/cm3, and the bubble size is uniform, which ensures high processing efficiency and very good processing effect. More than 85% of the bubbles in mm are invalid flotation bubbles. Moreover, due to the large diameter of the bubbles, the rising speed of the bubbles is too fast, causing the flocs to be impacted and ruptured, resulting in lower flotation efficiency. The diameter of the microbubbles generated in this case is below 1mm, and the density of the bubble group (the number of bubbles contained in the dissolved water per unit volume after energy dissipation) is generally below 108/cm. The uniformity of the bubble group (the proportion of the main bubble group to the total number of bubbles) is poor. For bubbles with a diameter greater than 100mm, the number can reach 106. Therefore, under the premise of a certain amount of dissolved air, reducing the diameter of a single bubble can increase the density of the bubble group, and the uniformity of the bubble group can also be improved. One of the most important reasons for the low efficiency of traditional air flotation is that the diameter of the generated bubbles is too large. The diameter of the main bubble group bubbles is generally around 50mm. If the bubbles become equal volumes of 1m, the efficiency of air flotation treatment depends on the maximum absolute weight of suspended particles that can be lifted per unit volume of dissolved water. We define it as the unit float, which is an objective indicator of the quality of dissolved water. Air is a substance that is difficult to dissolve in water. Under normal pressure, the solubility of air in water is about 1.8%. At a pressure of 0.3 Mpa, the solubility can reach 5.4%. How to fully utilize this limited dissolved air is the key technology of air flotation. Reducing the diameter of bubbles, increasing the density of bubble clusters, and improving bubble uniformity are the key to improving air flotation efficiency. The three are interrelated and mutually restrictive.
2. High utilization rate of dissolved gas
The utilization rate of dissolved air in this case is close to 100%, while the traditional vortex concave air flotation is only about 10%, and the early air flotation is only about 6%. The efficiency of air flotation is not closely related to the efficiency of dissolved gas, but ultimately depends on the utilization rate of dissolved gas. Taking the dissolved gas pressure as an example, increasing it from 0.3Mpa to 0.5Mpa can double the dissolved gas efficiency, but the structure of the corresponding dissolved gas equipment is much more complex, and maintenance is also correspondingly complicated. Research has shown that only bubbles with a diameter smaller than the suspended particles (individual suspended particles before flocculation) can effectively adsorb onto the suspended particles. In natural water bodies, suspended particles that are difficult to settle in a short period of time mostly have a diameter of 10-30mm. Solid suspended particles larger than 50mm can naturally sink or float to the surface after several hours of standing. The main particle size of the floating liquid is between 0.25-2.5mm, with a small amount of large particles around 10mm domestically. So, microbubbles of about 1mm have a good adsorption effect on the vast majority of suspended particles, which is also the direct reason for the high utilization rate of dissolved gas in this case.
3. High processing load
This scheme can treat wastewater with suspended solids (SS) content up to 5000-20000mg/L, which cannot be achieved by any traditional air flotation method. The maximum SS content that can be separated by traditional conventional air flotation is generally around 1000mg/L, and it only has certain practical value in wastewater with SS content of several hundred mg/L.
Simple and practical pressure dissolved gas
The design of the dissolved gas tank in this scheme adopts a different design basis from traditional theory, rejecting the design method mainly based on hydraulic retention time, and achieving a large processing capacity with small dissolved gas. To increase the contact area between air and water, a four stage premixing mechanism is adopted, and the gas and water can reach equilibrium in several periods of time.
4. Efficient bubble generator
Traditional air flotation, due to the defects and limitations of its release device, has also had a fatal impact on flotation efficiency. For example, vortex concave air flotation uses a high-speed rotating impeller to break up the inhaled air and generate bubbles. Regardless of whether the high-speed rotating impeller simultaneously stirs the flocs and destroys the aggregation of suspended matter, this method of generating bubbles alone determines that this structure cannot produce microbubbles below 10mm. Because to generate microbubbles through mechanical shearing, the first thing to overcome is the surface tension of the bubbles. The smaller the bubble, the greater its surface tension and the higher the energy required. The current method for obtaining the smallest bubble diameter is electrolysis, followed by pressure gas dissolution.
The bubble generator used in this case, with its reasonable design, achieves the perfect conversion of air from dissolved water to microbubbles, and has the following advantages:
(1) It can eliminate the energy of dissolved gas water to the maximum extent, that is to say, it can reduce the high energy value of dissolved gas water from the equilibrium state to a low energy value almost close to atmospheric pressure. The energy dissipation of dissolved water is the transfer of energy, not the loss of energy. The maximum consumption refers to the highest value of energy conversion under the premise of obtaining microbubbles with excellent physical properties. The energy dissipation ratio of the bubble generator used in this scheme can reach 99.9%, while ordinary bubble generators can only achieve a maximum of 95%.
(2) On the premise of obtaining the maximum energy dissipation ratio, it has the fastest energy reduction speed. That is to say, it has the shortest energy reduction time, which means it can achieve the maximum energy reduction ratio in the shortest energy reduction time. The energy dissipation time of the bubble generator used in this case is only 0.01-0.03 seconds, while the fastest for a regular bubble generator is 0.32 seconds.
(3) There is no flow state such as vortex or recoil generated during the process of dissolved gas water decreasing from high energy value to low energy value. As is well known, after the formation of microbubbles, a series of bubble merging processes occur. The merging effect is determined by the spontaneous reduction of surface energy. After two bubbles of the same volume merge, their surface energy decreases by 20.63%. If there is a structure in the release device that is conducive to bubble merging, it is impossible to obtain ideal microbubbles through this device. Only by eliminating the vortex and recoil of dissolved water can the merging of microbubbles be fundamentally avoided.
5、 Operation and precautions of vertical air flotation integrated machine
Before starting up, the dispensing device and gas dissolving device should be started first. When they enter normal operation, the raw water pump can be directly started (to reduce treatment load, raw water can be used as gas dissolving water), and at the same time, it can enter the tank. But it is necessary to maintain a constant dissolved gas pressure of 0.3-05 Mpa to ensure the maximum absolute amount of suspended particles that can float per unit volume of dissolved gas water.
Regular discharge: Sediments should be discharged every 2-3 hours and should not accumulate too much.
Before shutting down, thoroughly drain the mud once to avoid the floating layer affecting the quality of the next start-up treatment.
About 15 minutes after each startup, a small amount of suspended solids will appear in the clean water, which will then return to normal.