Selection, replacement and cleaning of cooling tower packing

1. What is the cooling tower fill?
The cooling tower packing is the core component of the cooling tower. The packing increases the heat dissipation in the cooling tower, prolongs the residence time of the cooling water, and increases the heat exchange area, which plays an important role in the cooling effect of the circulating water.

2. Filler selection

Some studies have shown that the heat dissipation capacity of water-spraying fillers can reach more than 70% of that of conventional cooling towers, so the choice of fillers is very important. There are many factors affecting the selection of fillers. It is necessary to comprehensively consider many factors such as cooling tower form, thermal characteristics, cooling tasks, circulating cooling water quality, ventilation conditions, thermal resistance characteristics of fillers, support methods of fillers, and cost of fillers.

1) Select according to the cooling water quality
When there is a possibility of leakage of raw material oil in the water or fibers in the water or the concentration of suspended solids in the cooling water is greater than 100mg/L, the drip packing should be selected; when there is no leakage and the water quality is well controlled or the concentration of suspended solids in the cooling water is less than 50mg/L, it should be selected. Film type packing; when the site is limited and the water may leak raw material oil pollutants or the concentration of suspended solids in the cooling water is between 50mg/L and 100mg/L, the drip film mixed packing type should be used.

2)According to the cooling tower type selection
The packing of the counter-flow cooling tower is usually arranged above the air inlet of the tower. The use of film type or drip film type can reduce the total height of the tower and reduce the cost. Generally, it is preferred for engineering design; while the height of the packing of the cross-flow cooling tower is the same as the height of the tower air inlet. In the same way, it is advantageous to use drip-type fillers with large heights. Of course, drip-type film type or film type fillers are not restrictive conditions for height and can also be applied. However, the packing depth (diameter depth) has a direct impact on the overall size of the tower, so the packing should be compared with the height of the tower body.

3)Select according to the water temperature entering the tower
Fillers of different materials have different applicable temperatures. In fact, even if the material is the same and the variety is different, the temperature resistance and physical properties may be very different. For example, the plastic materials widely used in cooling towers are: modified polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC), polypropylene (PP). The best use effect is when the tower water temperature is not higher than 45 °C, while the hydrophilicity of chlorinated polyvinyl chloride (CPVC) is worse than that of modified polyvinyl chloride (PVC), and the heat dissipation performance is not as good as the former. Polypropylene (PP) is in low temperature environment. When the temperature of the water entering the tower exceeds 45 °C, the temperature resistance of chlorinated polyvinyl chloride (CPVC) and polypropylene (PP) packing is obviously better than that of modified polyvinyl chloride (PVC). It is preferred; and when the water temperature entering the tower exceeds 60 °C, polypropylene (PP) has a higher temperature resistance, and the selection effect is better; when the water temperature entering the tower exceeds 70 °C or higher, the above three plastics are no longer available. Applicable, other high temperature resistant materials such as aluminum alloy should be considered.

4) Select according to the characteristics of the fan
The thermal characteristics and resistance characteristics of the filler should be comprehensively evaluated in combination with the characteristics of the fan, and the one with the largest cooling capacity under the same design conditions should be selected. Because the thermal performance of the packing is good, the resistance is often high. In a natural tower, the packing resistance is balanced by the suction force of the tower, and the suction force is proportional to the density difference between the inlet and outlet air of the packing. Generally speaking, fillers with high thermal performance use a relatively low air-water ratio, while the air density difference is relatively large, which has the effect of improving the pumping force. In a draft-type mechanical ventilation cooling tower, the drafting force is provided by the wind pressure of the fan, and the actual working wind pressure of the fan is proportional to the air density. When using a filler with a relatively low air-water ratio, the air density at the tower outlet is relatively low. There is the effect of reducing wind pressure, which is just the opposite of the former. It can be seen from the calculation and comparison of some examples that in the natural tower, when some fillers with better thermal performance are used in mechanical ventilation cooling towers, the order will be reversed, so the selection of fillers should be combined with fan characteristics. judge.

5) Select according to packing arrangement
As far as large cooling towers are concerned, when the filler is installed by hoisting, the shaking of the filler should be fully considered. The assembled form of the packing should be stable, convenient for construction and routine maintenance. In addition, when the filler block is simply supported directly on the support beam, the support beam should adopt a structure with small width and low ventilation resistance, and the beam center distance should be matched with the optimal size of the filler block simply supported. When supporting grating is used, the simply supported design span of the grating should be consistent with the span of the supporting beam, the corrosion resistance of the grating should be compatible with the filler, and the influence of the grating on the ventilation resistance should be considered.

In short, for water-spraying fillers, after fully considering various conditions, it is advisable to choose fillers with good thermal and resistance properties, good stiffness, corrosion resistance, aging resistance, and flame retardant properties.
3. Replacement and installation
Like other cooling tower components, the use of packing also requires routine maintenance and replacement. Generally speaking, the cooling tower needs to be replaced once after 5-8 years of normal use. In the absence of normal maintenance, the packing should be replaced every 2-3 years. If there is scaling, subsidence, aging, etc., it should be replaced in time to ensure that the efficiency of the cooling tower reaches the target.

The replacement of the cooling tower packing requires cleaning the tower on the basis of removing the waste cooling tower, and scientifically laying new packing in sequence. The replacement construction of old and new fillers generally follows the following steps:

1) Before construction, protect other equipment on site, and carry out necessary isolation and listing. Lay construction material cloth on the floor waterproof layer.

2) Remove the old packing. Turn off the power of the motor, remove the tie bars in the packing part of the cooling tower, then remove the old packing, and clean up the garbage in the tower.

3) Fill with new filler. Bond the cooling tower filler, and ensure the space for the filler to be placed during the curing time of the binder, to ensure that the contact point of the filler is on the same level during bonding, and to ensure that the contact point of the filler is uniform and tight during the crimping process.

4) Cleaning in the tower. Clean the dust and rubbish inside the cooling tower, stack the packing in the cooling tower in sequence, and strictly prohibit trampling and squeezing, to ensure that the packing blocks of each stack and each layer are neat, and to ensure that the packing and the corners and the circumference of the column are tight and seamless, and the distance between difficulties does not exceed 2mm. . Restoring the tie bars in the packing part of the cooling tower.

5) The assembly block should be assembled in the up and down direction, the top surface of each layer should be laid flat, and the layers should be cleaned to remove sundries.

6) When installation, maintenance and other work need to work on the packing, it must be operated on the flat plate, and it is strictly forbidden to step on the packing.

7) During the whole construction process, it is strictly forbidden to weld above the filler, and fire prevention measures should be taken if necessary.

8) After the replacement, tower body maintenance and other procedures are all completed, the construction tools and auxiliary installation facilities are brought out, and the project is successfully completed.

4. Cooling tower cleaning
(1) Disassemble and clean the packing of the cooling tower, pay attention to the stacking order when disassembling, cleaning and restoring the packing module, and adjust the stacking position and order during restoration and installation if necessary;

(2) Cleaning the cooling tower water distributor and chassis;

(3) Cleaning the cooling tower and its Y-type water filter;

(4) Use a long-haired hard brush and a high-pressure water gun to wash and scour the disassembled cooling tower packing block by block, and visually check whether the scale adhering to the packing surface wall falls off. It is best to restore the cooling tower packing surface wall to its original color;

(5) Check the integrity of the packing, sort out the damaged packing, and recommend to replace the severely damaged packing if necessary to ensure the operating efficiency of the cooling tower;

(6) Reinstall the packing, and it is recommended to stack and number the packing in advance, so as to facilitate the playback after the packing is cleaned, but it is recommended that each piece of packing be regularly adjusted and stacked, so that the aging rate of the packing can be synchronized;

(7) Sewage discharge from the chassis, in order to avoid waste of water resources, it is necessary to prevent sewage discharge while cleaning.