How to realize automation and environmental protec

2022-07-29
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How to realize automation, environmental protection and energy saving of pneumatic diaphragm valve ultrafiltration device

the hollow fiber ultrafiltration membrane used in a 1000m3/d direct drinking water project of a five-star hotel has an outer diameter of about 1mm and an inner hole of about 0.7? Mm. During filtration, raw water flows through the inner hole of the fiber. Under the action of pressure, the purified water passes through the micropores of the membrane and gathers together to form a ultrafiltration solution, which flows out from the side port of the filter. The hollow fiber membrane does not need any support structure. The filtering equipment composed of the hollow fiber membrane has simple structure and low equipment cost. According to the ratio of device volume and membrane area, the water treatment capacity of the hollow fiber ultrafiltration membrane equipment is 20 times higher than that of the flat membrane

the treatment process adopted in the project is:

tap water → raw water tank → sand filtration → activated carbon → softening → fine filtration → clean water tank → guest room. Sand filtration can remove most suspended and solid substances in the water (SS of effluent can reach 2 mg/l; 5 μ M precision winding filter element can make the effluent SS reach 0 and automatically print out the experimental data 1mg/l, the pollution index fi value can reach 3 ~ 5); Activated carbon and sodium ion softening resin can reduce the content of residual chlorine, organic matter, divalent calcium and magnesium plasma in water, so as to improve the taste of water

the system shares two ultrafiltration equipment, each of which uses 36 ultrafilters. These 36 ultrafilters are divided into groups A and B, with 18 ultrafilters in each group. During the operation of the equipment, the time of each process shall be adjusted and set according to the water volume change of the two output control modes of pulse generation and voltage, and the isobaric cleaning and reverse backwashing with the membrane shall be carried out in due time. Reverse backwashing is very effective, but the quality of backwashing water must be ultrafiltration water. Therefore, when designing the backwashing process, either use the output water of group a ultrafilter to wash group B ultrafilter, or use the output water of group B ultrafilter to wash group a ultrafilter; The overall dimension of ultrafilter used in ultrafiltration equipment is 90mm × 1000mm, containing about 2000 hollow fiber ultrafiltration membranes, with a membrane area of about 4m2. The membrane material is polyvinylidene fluoride, which has stable chemical properties. In particular, its pollution resistance is better than the commonly used PS, pan and other membrane materials. It is a new filter medium material for purified water

hollow fiber ultrafiltration membrane has many advantages, but there are still many problems to be solved in practical application, otherwise its use effect, especially the service life of the membrane, will be greatly affected. The key problem is the cleaning and recovery of the membrane, which involves cleaning time, cleaning method, cleaning agent and so on. The tap water is further purified into direct drinking water, and the water volume is required to be stable within 24h to ensure uninterrupted supply, which puts forward high requirements for the key equipment - ultrafiltration. In order to solve this problem, the "microcomputer pneumatic diaphragm valve automatic ultrafiltration equipment" designed and manufactured by ourselves is used in the ultrafiltration equipment, which realizes automation in the aspects of cleaning time, cleaning method and cleaning water

1. The automatic ultrafiltration equipment

microcomputer is combined with the pneumatic diaphragm valve. The control chip with the large-scale integrated circuit microcontroller 89C51 as the core is used. The pneumatic valve body is used as a control mechanism, and the layman can not see whether it is good or bad. The hollow fiber ultrafiltration membrane module is used as the control object to realize the automatic process of work, isobaric cleaning, backwashing and chemical cleaning. Automatic ultrafiltration can not only reduce the labor load, improve the operation reliability, prevent membrane damage caused by operation errors, but also timely clean the membrane in different ways, avoid irreversible pollution and blockage caused by long-time operation, and greatly prolong the service life of the membrane, The operator can and the wiring is correct. Before loading the system, the operator needs to open the electromechanical device and directly set the program time of "water making → equal pressure washing → backwashing → chemical cleaning" through the keyboard. The control system is composed of single-chip microcomputer motherboard, keyboard display board, power board, strong current board and electromagnetic pneumatic valve. First, the microcomputer realizes the logic control of the electromagnetic pneumatic valve through i/o interface and solid-state relay (SSR), The pneumatic diaphragm valve of the actuator is controlled by the electromagnetic pneumatic valve

2. Pneumatic diaphragm valve

pneumatic diaphragm valve is the key actuator in the automatic ultrafiltration device, which is required to be reliable and flexible. The pneumatic diaphragm valve is different from the general manual valve. It is driven by the gas pressure. Its structure is divided into upper and lower parts. The upper part is a compressed air chamber, and the lower part is the same as the general liquid diaphragm valve. After the air chamber is inflated, the rubber bowl is deformed, and the gas pressure pushes the connecting rod and positioning bracket to press down the rubber pad of the diaphragm valve. At this time, the valve is closed. When the compressed air pressure drops sharply, the rubber pad of the diaphragm valve returns to its original state under the joint action of the water flow pressure and the plastic bowl shape change restoring force, and the valve is opened at this time. The diaphragm only has two actions: full open and full close. The switch is flexible and convenient. According to the setting process, the opening and closing action is completed after receiving computer instructions. All valve bodies are made of ABS engineering plastics for injection molding, which has good mechanical properties, chemical properties and heat resistance, and has no pollution to water quality. The rubber pads and bowls in the valve are made of high-quality rubber, which is reinforced with cord inside, so the fatigue resistance is high

3. Environmental protection, energy conservation, and improvement of water utilization rate

one of the characteristics of membrane filtration is that the filter fluid flows laterally at a high speed on the membrane surface, and the impurities in the water are not easy to stay on the membrane surface (along with the original water flow), so the ultrafiltration membrane is not easy to be polluted. However, this will cause a large amount of water loss. Generally, in the ultrafiltration process of tap water, the utilization rate of water can reach 90% at most, and 10% of the water needs to be discharged. About 10% of the water has been treated by sand filtration, activated carbon, softening, fine filtration and other processes. Therefore, a recycling system is added in the design to increase the water recovery rate to 98.7%, and only 1.3% of the washing water is discharged when the equipment is automatically cleaned. During normal operation, the return water (or concentrated water shrinkage) returns to the intermediate water tank set at the bypass side between the fine filtration and ultrafiltration, allowing it to be continuously added to the ultrafiltration equipment with the fine filtration water

4. Promotion and application

in the water treatment project with ultrafiltration as the core technology, sand filtration, activated carbon, softening, fine filtration and other water treatment processes are combined with ultrafiltration to make the water quality performance indicators of produced water meet the design requirements, with total bacterial count <50/ml and total coliform count <3/l (sensory properties, general chemical indicators and toxicological indicators are omitted). The whole system has been running for one year. The assessment and test show that the equipment operates normally and the automatic control system meets the process requirements

the ultrafilter designed and manufactured by ourselves in the equipment, the microcomputer control system first developed in China and the pneumatic diaphragm valve have stable performance and can be further popularized and applied in large projects

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