How to deal with frost blockage in the condensation recovery unit? Direct answer: Frost is blocking the low-temperature heat exchange surface. The treatment should follow the four steps of "temperature control zone, tube humidity, defrosting cycle, and blockage location" - control the degree of subcooling in the low-temperature stage, block the inlet moisture pipe, set the defrosting cycle according to the moisture content and set temperature, and perform differentiated cleaning on easily blocked points such as separators and discharge ports. The judgment criteria are based on the trend of heat exchange temperature difference and pressure drop, where the frost layer falls first after a long recovery and the power consumption increases later. This article explains the defrosting and anti blocking aperture of graded condensation. Many sites only focus on the temperature of the host, and frosting on the low-temperature heat exchange surface occurs slowly. They only deal with it when the recovery rate significantly decreases, and the power consumption has already been wasted.
In graded condensation, the temperature of the low-temperature heat exchange surface is often lower than the dew point or even freezing point of the gas. The water vapor containing wet exhaust gas condenses into frost on the cold surface, gradually covering the heat exchange surface and occupying the airflow channel. The longer the frost layer, the more the gas escapes without sufficient heat exchange, and the low boiling point components cannot be collected, resulting in a decrease in recovery rate; At the same time, the pressure drop increases, the cooling load is abnormal, the defrosting frequency increases, and the power consumption increases accordingly. The frosting rate is related to the moisture content of the intake, the set temperature of the low-temperature stage, and the residence time. The lower the temperature and the higher the humidity, the faster the frosting will occur. To understand the cause of this blockage, we can start with "temperature control zone and pipe humidity".
The temperature control zone is the key front gate for preventing blockages: do not blindly set the temperature at low temperatures. The greater the degree of undercooling, the stronger the tendency for frosting. Leave a reasonable margin according to the solidification point of the components. Humidity management relies on pre-processing: in situations where the intake moisture content is high, the front-end dehumidification or temperature and humidity reduction is used to reduce the amount of water vapor, resulting in a lighter burden and slower frosting at low temperatures. Doing both tasks together is more convenient than defrosting after frost has formed. Calculate the moisture content in the temperature zone during the design phase, and don't wait until it's put into operation to find frost forming every day at low temperatures.
The defrost cycle is not a fixed value and is determined by the operating conditions: high humidity in the intake, low set temperature, fast frost accumulation, and short intervals; Low moisture content, moderate temperature, and can be placed at long intervals. When determining, refer to the heat exchange temperature difference and pressure drop trend in the operation record. A decrease in temperature difference and a rise in pressure drop are the signals for defrosting. Don't wait until it's blocked. The defrosting method follows the logic of the device, and defrosting should be thorough. It is more troublesome to repeatedly stack layers of incomplete defrosting. Defrosting too frequently interrupts continuous operation, and it is too sparse and blocked. The balance point depends on the data.
Blockage is not only on the heat exchange surface: liquid accumulation in gas-liquid separators, freezing of collection and discharge ports, and dust accumulation at gas channel corners can also cause blockage. The main method for frosting on the heat exchange surface is defrosting; The accumulated liquid or impurities in the separator should be cleaned and checked for smooth drainage; Improve the freezing of the discharge port with heat tracing or insulation; Regularly blow and clean the corner dust accumulation. Differentiated treatment for different parts is necessary to turn occasional disposal into regular management, rather than checking everywhere every time there is a blockage.
| Part | Cause of blockage | disposal method | Attention point |
|---|---|---|---|
| Low temperature heat exchange surface | Supercooled frosting | Defrost logically | Reduce the degree of supercooling in the temperature control zone |
| Inlet moisture content | High humidity and fast frosting | Front end dehumidification and temperature rise | Without humidity control, defrosting alone cannot withstand it |
| gas-liquid separator | Accumulation of fluid and impurities | Clean up nuclear discharge fluid | Poor drainage and repeated blockage |
| Liquid collection and discharge port | freeze | Heat tracing insulation | Frost removal and drainage should be smooth |
| Channel corner | Dirt | Regular blowing and sweeping | Easy to accumulate dust at corners |
Not: too frequent interruption of continuous operation, increased power consumption, too sparse and blocked; According to the intake moisture content and low-temperature temperature, observe the trend of heat transfer temperature difference and pressure drop, and clear the frost signal as soon as it appears. Do not mechanically follow a fixed interval.
The repeated stacking of frost layers results in thicker and more blocked channels, lower recovery rates, and higher power consumption. In severe cases, there may be abnormal low-temperature loads; Defrosting should be thoroughly cleaned according to the equipment logic, and defrosting drainage should be unobstructed.
Front end dehumidification or temperature and humidity reduction reduces the amount of water vapor before entering the low-temperature stage; Without humidity control, frost will continue to form at low temperatures, and defrosting alone cannot withstand it. Pre treatment and temperature control zones need to be done together to ensure stability.
This article by LuoyangWohong PetrochemicalEquipment Co., Ltd. arranges that the company provides design, manufacturing and operation and maintenance services for condensation recovery, membrane separation recovery and complete solvent recovery devices for chemical and pharmaceutical enterprises. If you need process evaluation or scheme configuration, please contact and exchange.
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