Operation and maintenance of ultrafiltration-reverse osmosis system in power plant water treatment application

With the development of society and economy, the water treatment technology of power plant has made some progress, and the development of ultrafiltration-reverse osmosis system has been introduced. The system first originated in 2000 and was obtained by modifying the first-level desalination + mixed bed ion exchange system. The transformed system has great applicability and brings great convenience to the operation of power plants, but there are more or less problems in its operation, maintenance and management. Under this background, in-depth analysis of the operation, maintenance and management of the ultrafiltration-reverse osmosis system in power plant water treatment applications is of vital importance.

Ⅰ. Overview

The process flow of ultrafiltration-reverse osmosis system mainly includes industrial water pump outlet-valveless filter-raw water pump-laminated filter-clean water tank-clean water pump-filter 20μ-4 group ultrafiltration-clean water tank-clean water pump -Filter 5-μ-High-pressure pump-2 sets of reverse osmosis-fresh water tank-fresh water pump-primary desalination + mixed bed ion exchange system. This system provides boiler make-up water for each unit of the power plant, and also shoulders the task of supplying water to the power plant’s heating equipment, which has a very important role and significance.

As the operating time of the permeable membrane in the ultrafiltration-reverse osmosis system has greatly increased, the water production of this system decreases by about 15% every year. Obviously, the power plant has achieved certain economic benefits under the full utilization of the system, and has greatly reduced the total work of the power plant staff and reduced their burden.

Ⅱ. Stable operation measures of ultrafiltration-reverse osmosis system

1. During the operation of the system, reverse backwashing is used regularly to clean up the substances adsorbed or trapped on the surface of the ultrafiltration membrane, and the cleaning time and system running time are adjusted reasonably according to the water quality of the influent.

2. Increase its investment, install water quality online monitoring instruments at the water inlet, and monitor the water quality in real time, so as to grasp the water quality timely and accurately. At this stage, in the detection of whether surface water is mixed into the influent work, the more commonly used raw water online DD table. The detection instrument controls the water pollution index to less than 2. When the influent exceeds this range, an alarm will be issued in time to facilitate the duty personnel to analyze in time and take corresponding measures. To a certain extent, the phenomenon of reduced water production due to increased turbidity is eliminated.

3. For 20μm filter, the supervision should be increased. As a security measure, the device shoulders the role of filtering suspended solids, but does not filter the load. Therefore, each manufacturer should set the pressure drop limit value, so as to realize the timely replacement of the filter.

4. Control incoming water quality through shutdown protection. Mainly refers to the formation of metastable salt crystals under the premise of scale inhibitors, so as to avoid the reproduction of organisms. Based on the ultrafiltration membrane materials and the operating conditions of various devices, selective shutdown operations are carried out to achieve effective control of influent water quality.

5. As a deep filter element in ultrafiltration, reverse osmosis membranes will inevitably produce a large amount of microorganisms, particles and colloids on the surface. This puts high demands on the cleaning work. We should pay attention to the timeliness of the cleaning work. On the basis of ensuring the annual cleaning work, according to the cleaning standard of the reverse osmosis membrane, compare the indicators and the current operating indicators just after commissioning. When the salt flux is as high as 15% after normalization, cleaning work should be performed immediately.

Ⅲ. Operation, maintenance and management focus in the application of ultrafiltration-reverse osmosis system

(1) The stability of the water output during ultrafiltration operation should be taken as the management focus, and various operation maintenance and management measures should be adopted reasonably according to the actual operation of the power plant. On this basis, the safe and stable operation of the pretreatment equipment is guaranteed to fully meet the water inlet requirements during the operation of the ultrafiltration-reverse osmosis system.

(2) The extension and management of the service life of the ultrafiltration-reverse osmosis membrane should be taken as the primary task, and the corresponding operation and maintenance measures should be actively adopted to prevent the reverse osmosis membrane from being blocked or contaminated, thereby avoiding the damage and deterioration of the ultrafiltration membrane.