Reverse osmosis equipment maintenance cleaning
Eastony Industries (NingBo) Co., LTD. , https://www.eastony.com
The key component of reverse osmosis equipment is a semi-permeable membrane, and its maintenance and maintenance is the key to the entire system.
(1) Maintenance of reverse osmosis membrane components:
The maintenance of membrane elements is summarized into two major aspects: first, reverse osmosis pretreatment, and second, rinsing, cleaning and maintenance of reverse osmosis equipment. In either case, there is only one final destination: extending the life of the membrane element and maintaining the performance of the membrane element.
1. Pretreatment of reverse osmosis equipment
To be a pretreatment of the reverse osmosis system, it is first necessary to configure the pretreatment equipment according to the raw water quality, which is critical to the safety of the entire system. The raw water quality of our company is underground deep well water. The raw water hardness is higher, the free chlorine is less, and there is a certain colloid content, COD: 30mg/l,
Equipment process: raw water → clean water tank → pre-filter → horizontal filter → microporous filter → RO → decarbonization tower → intermediate water tank → mixed bed → demineralized water tank.
The reverse osmosis system is a whole, and each treatment process is interconnected. One ring and one ring, the effect of the previous treatment process may affect the next process, and even affect the final water quality and performance of the entire process. Therefore, the water quality target requirements for each unit treatment must be clarified.
1) Maintenance of multi-media filters.
Our company is two horizontal filters, one is divided into six grids, each grid output is 66.7 tons / hr, multi-media filter maintenance scrubbing, backwashing is the key, after scrubbing should make its water output SDI less than 4, scrub Steps: water release → scrubbing → backwashing → positive west. The water level should be suitable when scrubbing, the amount of scrubbing air must be sufficient, and the backwashing flow should be well mastered.
There are two principles to be mastered in dealing with filters: one is to scrub enough; the other is to thoroughly wash back. Filters that have been shut down for a long time should be shut down for maintenance. The method used by our company is to add a certain dose of fungicide to fully agitate and seal. Rinse out when using. The purpose is to prevent the growth of microbial bacteria. In addition, our company uses the transfer device to transfer and clean the filter material in the filter every two years to ensure the quality of the filter material.
2) Microporous filter (also known as security filter).
It is the last protective screen to filter raw water. We believe that the most important two factors for the microporous filter to play its due role are as follows: First, supervise the pressure difference between the inlet and outlet. Once the pressure difference exceeds 1 kg, it must be replaced. Another factor that cannot be ignored is the quality of the filter element. Some thermal power plants are caused by the purchase of cheap and inferior filter elements. Although the pressure difference is acceptable all the year round, but the filter function is not affected, the membrane components are severely blocked, so that some membrane elements are scrapped and cause great losses.
2. In summary, the purpose of preprocessing is to:
(1) Prevent contamination on the surface of the membrane: suspended matter, colloids, microorganisms;
(2) Preventing fouling on the surface of the membrane: by adding a scale inhibitor;
(3) Ensure that the membrane is protected from mechanical and chemical damage.
To do a good job of preprocessing:
(1) Carefully determine the water output index of the pretreatment equipment;
(2) Do a good job of backwashing and scrubbing regularly;
(3) The equipment configuration is reasonable;
(4) Do the raw water dosing work: especially the amount and quality of the scale inhibitor.
RO start and stop flushing
1) Each set of RO needs to be flushed with demineralized water during start and stop. Generally, the flushing water volume is controlled at about 60T/hour.
2) Flushing during commissioning can also be used to remove demineralized water. The purpose is two: it is to wash off the salt on the surface of the membrane and also protect the membrane.
(2) Chemical cleaning of reverse osmosis membrane
1, the purpose of cleaning:
Restore the good water permeability and desalination ability of the semipermeable membrane, protect the performance of the membrane and prolong the service life of the membrane.
2, cleaning conditions: (under the same original underwater)
(1) The standard water permeability is reduced by 10% to 15%;
(2) The standard system pressure difference is increased by 10% to 15%;
(3) Desalination rate decreased by 1% to 2%
3. Cleaning method:
A, online cleaning; B, offline cleaning.
The so-called in-line cleaning, that is, the cleaning of the membrane elements in the entire RO system by the cleaning device.
The so-called off-line cleaning means that each film is taken out and cleaned separately.
The advantage of online cleaning is that it is easy to operate and short in use, and the disadvantage is that the cleaning is not complete.
The advantage of off-line cleaning is that it is thoroughly cleaned. The disadvantage is that it takes a long time and the operation is complicated.
The specific cleaning method used by the manufacturer can be determined according to the actual situation.
Two sets of RO semi-permeable membranes of Taishan Chengjian Thermal Power Co., Ltd. have been subjected to offline cleaning and multiple online cleaning.
Here is a brief introduction to online heating cleaning. According to our experience and technical data statistics, online heating cleaning can achieve the effect of offline cleaning, and avoid the cumbersome off-line cleaning, which has certain practical significance and operability.
The specific method is briefly introduced as follows:
After the water in the RO is cleaned, the boiler feed water (higher temperature) is referenced to the cleaning solution, so that the solution water temperature is controlled at about 30°, and the cleaning liquid can be heated by the heater. First pickling, the temperature of the cleaning circulating water does not exceed 30 °, generally around 28 °, cycle for 20 minutes, rinse and then adjust the temperature of the alkaline washing solution to 26 ± 1 °, cycle, time 40 minutes. According to the water quality of the cleaned back water, it is decided whether to re-clean, and finally a pickling is performed, and the whole cleaning process is finished.
(3) Stopping and maintenance of reverse osmosis equipment
The reverse osmosis in production must be flushed every time it is started and stopped. The purpose is to wash away the salt on the surface of the membrane, especially when it is out of service. The long-term or short-term shutdown of reverse osmosis must take the necessary maintenance. Methods as below:
1. Stop the operation for 1 to 3 days and regularly perform low-pressure (0.2KG ~ 0.4KG) high-flow flushing on the RO system for 15 minutes and 15 minutes. It is better to use demineralized water for rinsing.
2, out of service for more than 7 days, first use the demineralized water washing method, then use 0.5% sodium bisulfite solution to soak, seal.
3. If the system is out of service for more than 10 days, it should be sealed with 0.5% formalin solution and replaced every 30 days.
(4) Repair of semipermeable membrane
If the damaged semi-permeable membrane has good performance, but the external or the end is damaged, open the loop, do not easily discard it, and repair it with epoxy resin with corresponding solvent and glass cloth. Our company has more than ten 8-inch Dow films with rupture of the end membrane ring. It has not been replaced since the above method has been repaired for 4 years, and it also shows that the damaged membrane element can be reused, saving material costs.
In summary, to maintain a good set of RO equipment, to protect the semi-permeable membrane, so that it has a longer life, you need to do the following:
1. Do a good job of reverse osmosis pretreatment to make SDI&S249;4;
2, do a good job of reverse osmosis dosing, choose the appropriate scale inhibitor;
3. Do a good job in chemical cleaning in a timely manner;
4. Do a good job of running data analysis;
5, do a good job of membrane outage protection during the outage;
6. Do a good job in the diagnosis of abnormal conditions in the reverse osmosis system.
(5) Composition of reverse osmosis water treatment system:
The reverse osmosis device is a set of water treatment system organized around the reverse osmosis membrane. A complete reverse osmosis system consists of a pretreatment part, a reverse osmosis main unit (membrane filtration part), a post-treatment part and a system cleaning part.
First, the pretreatment is often composed of a quartz sand filter device, an activated carbon filter device, and a precision filter device. The main purpose is to remove sediment, rust, colloidal substances, suspended solids, pigments, odors, biochemical organic matter, and water in the raw water. Residual ammonia and harmful substances such as pesticide pollution. If the content of calcium and magnesium ions in the raw water is high, the soft water device needs to be added. The main purpose is to protect the reverse osmosis membrane of the latter stage from the destruction of large particulate matter, thereby prolonging the service life of the reverse osmosis membrane.
Second, the reverse osmosis host is mainly composed of a booster pump, a membrane shell, a reverse osmosis membrane, a control circuit, etc., and is the core part of the entire water treatment system. The quality of the water quality depends mainly on this part. As long as the model of the membrane and the model of the booster pump are selected, the reverse osmosis host can achieve a filtration capacity of more than 99% of the salt in the water, and the conductivity of the effluent can be guaranteed within 10 us/cm (25 degrees).
Third, the post-processing part is mainly to further treat the pure water taken by the main mechanism of reverse osmosis. If the subsequent process is connected with ion exchange or electrodeionization (EDI) equipment, industrial ultrapure water can be obtained, if it is used in For the direct drinking water technology, the rear-end sterilizing device is often connected. For example, the external germicidal lamp or the ozone generator can be connected, so that the water can be directly consumed.
4. In order to ensure the normal operation of the reverse osmosis system and prolong the service life of the reverse osmosis membrane element, when the reverse osmosis system is operated for a period of time, it is necessary to remove calcium carbonate scale, metal oxide scale in water, and biological growth (bacteria, fungi, mold, etc.) The substance needs to be cleaned. When do you need to clean? For related technical knowledge on how to clean and what kind of chemicals to use for cleaning, please go to the "Download" section of the Customer Service Center. Under the condition that no phase change occurs at normal temperature, the solute and water can be separated, which is suitable for the separation and concentration of heat sensitive substances, and the energy consumption is lower than that of the phase change separation method.
· Reverse osmosis membrane separation technology has a wide range of impurity removal.
·High salt rejection and water reuse rate, which can cut off solute with a particle size of several nanometers or more.
·Using low pressure as the membrane separation power, the separation device is simple, the operation, maintenance and self-control are simple, and the site is safe and sanitary.
Therefore, reverse osmosis water treatment technology in power plant boiler feed water treatment, ultra-pure water treatment in electronics and semiconductor industries, pure water treatment in chemical and pharmaceutical industries, food, beverage, drinking water treatment, seawater, brackish water desalination, metallurgy, light industry It has been widely used in industries such as wastewater treatment in electroplating and leather industries.