Powder Supply Center

Working Principle of Large Cyclone Secondary Recycling Spray Booth

The powder sprayed from the spray gun, the part which is not adhension on the workpiece is brought to the inside of the large cyclone by the airflow that generated by the exhaust fan,  the larger powder is be separated in the separator and drop on the vibrating screen, shake the sieve through the vibration motor, then the powder which has been removed impurities is dropped into the powder recovery group. Return to the powder box through the powder recovery pump and the powder supplying  tube, then be reused . Effectively reduces the waste of powder.

The powder that has not been separated from the large cyclone is sucked into the secondary recovery,  the filter element in the secondary recovery separates the remaining powder from the air,then the purified air is discharged to the inside of the workshop.

The filter element will be cleaned with compressed air for a period of time via the rotate wing and the powder will be blown into the powder collecting bucket.

Care and Maintenance of The Large Cyclone Secondary Recycling Spray Booth

Spray booth

Every day, clean up the accumulated powder in the spray booth (even if the color is not changed), to prevent the powder from accumulating for a long time and solidify on the spray chamber.

Every week, check whether the air hole of the “airflow pulse floor cleaning device” at the bottom of the spray booth is blocked. Clean it up in time after plugging and the cleaning air pressure is controlled between 2-4 bar.

Large cyclone separator

Every day, clean up the accumulated powder in the cyclone (even if the color is not changed), otherwise the powder will solidify on the inner wall of the cyclone due to high-speed rotation, resulting in a decrease in cyclone separation efficiency; Check the mesh screen and clean up the accumulated powder on the screen.  If the mesh surface is damaged, replace it in time; clean up the powder recovery barrel to prevent the powder from agglomerating and affect the powder recycling; check whether the mesh screen can be lifted smoothly, whether the seal is intact to prevent low recovery efficiency due to air leakage.

Every week, clean up the powder in the powder recovery pump, to prevent accumulation of agglomerates and affect recycling.

Every six months, check the wear condition of the powder pump and the powder tube, replace it if necessary.

The powder recovery pressure is set at 2-4 bar. If the powder recovery efficiency is too low, adjust the atmospheric pressure appropriately, and vice versa.

Secondary recovery

Every day, clean up the waste powder in the collection powder box. In general, the weight of the waste powder is 3%--5% of the normal used powder; Check the differential pressure range of the differential pressure gauge, the normal range is between 1.0KPa and 2KPa. If beyond the differential pressure range, it indicates that the filter element is severely clogged or the filter cleaning device is malfunction; the filter cleaning pressure is set between 4-4.5 bar.

Every week, check the powder accumulation of the filter surface area. If the powder accumulation is serious, the filter element has been blocked or the filter cleaning device has a malfunction.

Every three months, check whether the rotary wing is working properly, whether the lifting plate on the rotary wing is cracked and damaged,  replace it if necessary.

Every year, check and clean the bonding powder on the fan blades, check the vibration of the fan, remove them to check the dynamic balance if necessary.

Reciprocator

Every week, open the side panel of the reciprocator to check the tightness of the timing belt, tighten it in time and clean up the powder adhering to the rail.

Every month, open the top hat and side panels of the reciprocators to check the wear condition of the pulleys and bearings, replace them if necessary.

Powder box

Every week, clean up the powder in the powder box.

Every three months, check the fluidization situation of the fluidized plate and the sealing of the fluidized plate, replace it if necessary.

Detailed description of electrostatic spray powder recovery device:

First, the principle of spray recycling device

The electrostatic powder coating recovery device is derived from the dust removal device in the environmental protection equipment. The basic function is to realize the two-phase separation of the gas and solid mixed fluid. The difference is that the solid phase after dust removal is waste, but the solid phase after recovery is It is a utilization material, and various filter bags and filter separators are used as the main filtering equipment. The working principle is to cut off the powder through the filter material acting as a sieve.

Second, the classification of recycling devices

The coating industry divides it into primary recovery, secondary recovery, and even tertiary recovery from the perspective of equipment combination configuration of the recovery unit.

1. Primary recovery only uses a filter separator to complete the recovery of the powder, usually designed with a single integrated powder room.

2. Secondary recovery refers to the recovery system formed by the cyclone separator and the filter separator in series, which is the most common in the existing electrostatic powder coating production line.

3. The third-stage recycling is based on the secondary recovery, and then connected to the primary filtration separator in series, only for occasions with special environmental protection requirements.

1.1 Filter element primary recovery device for integrated powder room

A plurality of filter elements are directly disposed in the operating position of the powder spraying chamber, and the integrated recycling device of the integrated powder room filter element formed on the opposite side is a relatively common configuration.

During the powder coating operation, the floating powder not adsorbed on the workpiece to be coated is sucked by the exhaust fan together with the indoor air, and flows to the filter element opposite to the operation port, and is filtered by a filter element made of a filter material such as parchment, and the powder is trapped. Indoors, the air is vented through the filter to the outside. In this way, when the filter element is back-blown with compressed air, the powder on the surface of the filter element falls into the collecting box at the bottom of the chamber, and can be recycled. The continuous exhaust air not only maintains the negative pressure inside the room, the powder can not overflow, and ensures that the indoor dust concentration does not exceed the explosion boundary.

The advantage of this recycling configuration is that it is compact in structure and small in floor space. Because there is no need to connect pipes, maintenance and cleaning are very convenient, and equipment investment is relatively small. The disadvantage is that the recovery burden of the filter element is heavy, and it is easy to be blocked and damaged. In addition, the operation port cannot be provided on the side of the filter element, so it is suitable for occasions where the amount of powder sprayed is small and the recovery burden is light.

2.1 Two-stage recovery device consisting of single cyclone and filter recovery unit

Mono cyclone separators are commonly known as "big cyclone" When the air inlet pipe is connected with the air outlet of the spraying chamber (standing at the bottom of the powder spraying chamber), and the air outlet is connected with the air inlet of the filter separator, a single cyclone and filter recovery unit is formed the secondary recovery unit.

When the secondary recovery device is in operation, the gas and powder mixed air extracted from the spraying booth first enters the mono cyclone. Under the centrifugal action of high-speed cyclone, more than 80% of the larger particle size powder falls into the bottom of the tube along the wall of the cyclone tube, and the air containing a small amount of fine powder is transferred to the bag filter separator for filtration separation. Due to the cooperation of the two-stage device, it can withstand a large recovery load and the recovery rate is over 95%.

The secondary recovery configuration is designed in the structure of the powder spraying chamber, so that it can not occupy the operating positions on both sides, thus facilitating the spraying operation of the larger workpiece.

The disadvantage is that the work space is large, especially in the interior of the large cyclone and the recovery pipeline is inconvenient to clean, so it is not suitable for electrostatic powder coating with frequent color change.

2.2 Two-stage recovery device consisting of multi-tube cyclone and filter element filtration

The connection relationship and effect of this recycling configuration are similar to those of the large cyclone and filter recovery unit. The difference is that multi-tube cyclone (also known as small cyclone) uses a multi-tube structure to replace the single-tube of the large cyclone, so it is relatively short and relatively easy to clean.

In addition, the cleaning or replacement of the filter element is easier. It is suitable for occasions where the amount of spraying is large and there is a color change requirement. The disadvantage is that equipment investment costs are higher and there are fewer options to choose from.

When secondary recovery is used, the large particle size powder usually separated by the cyclone can be directly reused. There are two methods for recycling: one is to manually remove the powder collecting bucket at the bottom of the cyclone tube, and the recycled powder is sieved and then returned to the powder feeding device; the second is to use the so-called closed-circuit recycling system for automatic reuse, that is, by installing in the set. The venturi powder pump on the powder bucket slowly returns the recovered powder to the powder supply device under the action of compressed air. Obviously, the amount of spraying work is large, especially for the continuous production of electrostatic powder coating production line, the second recycling method should be adopted.