The wire-wound filter element is a filter element which is made by precisely winding a textile fiber with good filtering characteristics on a porous skeleton. It has the characteristics of large interception amount, small resistance, high strength and backwashing, and is widely used. In the pre-tube filter in the condensate polishing system of the power plant (hereinafter referred to as the tubular filter), the filter element in the tube filter cannot be removed from the filter element due to the large amount of contaminants retained after a period of use. Elution on the wire causes the filter element to be fouled, the initial differential pressure of the filter to be high, the operating pressure difference to rise too fast, and the operating cycle to be significantly shortened. Not only increases the operating cost of the finishing process, but also reduces the commissioning rate of the filter, which jeopardizes the safe and stable operation of the unit. The 1 MW unit has higher requirements on the quality of the soda water. Therefore, if the filter element of the tube filter of the finishing system is contaminated, chemical cleaning must be carried out in time.
Off-line chemical cleaning uses a combination of cleaning agent and special cleaning equipment to combine chemical cleaning and physical cleaning to chemically clean the filter element outside the filter. This technology has a clean and thorough cleaning, short construction period, no damage to the equipment, etc. Features, especially for wire-wound filter cleaning of 1000MW unit power plant precision treated tube filter 4-5. 1 Contaminant composition analysis To ensure the role of off-line chemical cleaning, the first step in the study is to analyze the fouling caused by the filter element. The main component of the pollutant. The composition of the pollutants on the surface of the contaminated filter element is tested and analyzed. And Table 1 is the scanning electron micrograph and energy spectrum analysis results of the surface pollutants of the tubular filter of the 2x1000MW supercritical wet cooling unit of Suizhong Power Plant.
It can be seen from the scanning electron micrograph that the surface of the contaminated filter element is contaminated with the surface of the filter element. Scanning electron microscopy image. Table 1 The surface energy of the filter element is analyzed by the spectrum analysis. The chemical cleaning effect of the filter element is mostly reddish brown particles. Scanning electron microscopy and energy spectrum analysis show that the main products are iron oxidation products. In addition, a small amount of silicon compounds and oil contaminants are found in the surface pollutants of the filter elements.
2 filter offline chemical cleaning process 2.1 compound cleaning agent filter offline chemical cleaning to remove iron, while taking into account silicon and oil removal. In addition, due to the limitation of the strength of the filter element winding, it is necessary to strictly control the conditions such as the filter cleaning agent concentration and the cleaning temperature, otherwise it is easy to cause the filter element to become brittle and the service life is shortened. Therefore, it is necessary to develop a new type of compound cleaning agent, which not only can effectively remove iron, silicon, oil and other contaminants, but also has good solubility, easy rinsing, and low cleaning temperature.
2.2 Cleaning process The off-line chemical cleaning simulation test bench is used to determine the optimal process conditions for cleaning, including the cleaning temperature, cleaning agent concentration, cleaning flow rate and other influencing conditions. The appearance of the simulation test bench for the offline chemical cleaning of the filter element.
The offline chemical cleaning simulation test bench of the filter element is a cleaning effect diagram of the chemical filter only. The experiment found that although the chemical action of the drug can dissolve most of the pollutants, the detergent consumption is large, the soaking time is long, and some pollutants have precipitated inside the filter element, which is difficult to pass the general backwashing operation. Elution. Therefore, it is necessary to consider the combination of chemical action and physical action, and use the chemical action of an appropriate amount of cleaning agent to loosen and dissolve the contaminants on the surface and inside of the filter element, and then use special cleaning equipment to peel off the contaminants from the surface and inside of the filter element. This not only saves the consumption of cleaning agent, but also improves the cleaning efficiency and shortens the construction period.
3 Filter element offline chemical cleaning features Clean the filter element in the filter body, the cleaning process is safe and reliable, and will not have any adverse impact on the power plant equipment.
Special equipment and compound cleaning agent are used to ensure uniform cleaning effect, which can effectively remove various pollutants. After cleaning, the flux of the filter element can be effectively restored, and the color changes from black to light white.
The cleaning temperature is low, which will not affect the fiber strength and ensure the service life of the filter. The service life of the imported filter element is generally up to 2 years under normal conditions. After the contaminated filter element is cleaned offline, the service life of the filter element can be extended to 3 to 5 years.
Since no new impurities are introduced during the cleaning process, and the used agent has good solubility and easy washing, the flushing time is short when the system is put into operation, the water consumption is low, and the water quality is not affected, and the system can be put into operation very quickly.
The cleaning time is short, and with the removal and installation of the filter element, one filter can be cleaned within 3 days. Therefore, it does not affect the operation of the power plant, even if it is not overhauled.
4 Application examples and effects The condensate water treatment system of Jizhong Power Plant adopts a pre-filter-high-speed spherical mixed bed system, in which the wire-wound filter element in the tube filter is subjected to severe iron pollution and oil pollution during operation. The filter operating cycle is significantly shortened, and the cycle water production is greatly reduced. Using the off-line chemical cleaning technology of the filter element, more than 2,000 filter elements of the two units were cleaned. After cleaning, the color of the filter element changed from the original dark brown to light white, and the surface was clean and free of residual impurities. The operating cycle is extended from a minimum of about 4 hours before cleaning to more than 41 hours, and the cycle water production is increased from a minimum of about 7000 m3 before cleaning to 61,000 m3, which is nearly nine times higher. In addition, due to the reduction in the number of backwashing, the filter is reduced from 0.3% to 0.03% before cleaning, and the annual water consumption is saved: the operating cycle is cleaned before and after the filter. Compared with the comparison chart of the tubular filter filter before and after washing, the cleaning effect and economic benefits are very significant.
And for the plant No. 3 machine No. 1 filter running differential pressure curve, the curve interruption represents the end of a running cycle. For the comparison of the appearance of the filter before and after cleaning.
The off-line chemical cleaning technology of the filter element is an effective method to solve the problem that the initial pressure difference of the power plant filter is large, the running pressure difference rises too fast, and the operation cycle is short. It has the advantages of good effect, low cost, safety and reliability. Relying on special cleaning agents and cleaning equipment, it can effectively solve the problems of iron pollution, silicon pollution and oil pollution of various types of filter elements (wire winding, large flow, etc.).
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