Plate heat exchanger in the operation of the use of the period may appear scaling problems, then, do you understand the reasons behind this phenomenon? The following is a brief explanation of the hazards of scaling by me, the formation of the six types of scaling process and preventive measures to deal with scaling.
Six hazards of plate heat exchanger scaling
Plate heat exchanger is widely used in industrial and civil fields, and its working principle is to exchange heat through the temperature difference between the plates. However, in the process of use, due to water quality problems or solid particles in the fluid medium, deposits will be formed between the plates, i.e. scaling. If not cleaned in time, scaling can cause the following hazards:
1. Reduced heat transfer efficiency:
Scaling will form a layer of insulation, hindering heat transfer, resulting in a reduction in heat transfer efficiency, affecting the normal operation of the equipment.
2. Increased pressure drop:
Scaling makes the fluid channel narrow, flow resistance increases, resulting in increased energy consumption of the pump, the system pressure drop increases.
3. shorten equipment life:
Long-term scaling will accelerate the aging of the equipment, corrosion plate, reducing the service life of the equipment.
4. Increased operating costs:
Heat transfer efficiency decreases and energy consumption increases, companies need to invest more energy and money to maintain the original heat transfer effect.
5. Reduced system safety:
Fouling may lead to localized overheating of the equipment, causing safety accidents.
6. Increased maintenance costs:
Severe scaling may require more frequent downtime for cleaning, increasing maintenance costs and downtime.
Six main types of plate heat exchanger fouling processes
Plate heat exchangers may form several types of scaling during operation, which are mainly formed by different components and mechanisms. The following are the six main types of scaling processes:
1. Crystallization fouling:
Mainly by the sulfate, carbonate and silicate and other dissolved salts in the flow process due to the lower temperature of the hot surface leads to solution oversaturation, so as to precipitate in the heat exchanger tube wall to form a tight solid fouling. The formation of this fouling usually involves two major steps: the transport of ions from the bulk fluid to nearby surfaces, and the attachment of the fouling to the equipment surface. The main factor affecting precipitation fouling is the degree of supersaturation of the solution
2. Biofouling:
Microorganisms such as bacteria, fungi, and algae in untreated seawater, river water, or lake water will form fouling after attaching to and depositing on the pipe wall surface under the right conditions. This film-like layer of soft sludge impedes heat transfer and creates conditions for the deposition of fine particulate matter and inorganic salts. Microorganisms of many kinds, tenacious, fast breeding speed and wide distribution, to the characteristics of biological scaling in the heat exchanger and descaling technology has brought greater difficulties.
3. Corrosion scaling:
In the process of use, the heat exchanger surface chemical corrosion, which produces deposits to form fouling. Corrosion fouling is very easy to be flushed by the flow of liquid, resulting in wall thickness thinning leakage, great harm. Corrosion mainly includes chemical corrosion and electrochemical corrosion
4. Particle fouling:
By insoluble impurity particles, heterogeneous nucleation particles, homogeneous nucleation particles and heat exchanger wall stripping particles, gravity and collision under the action of attachment to the heat exchanger surface to form a layer of solid deposits. Particle fouling adhesion is small, concentrated in the laminar flow region of the wall, and easy to accumulate in the surface roughness. Particle fouling deposits will increase the number of nucleation points of crystallization scaling, promote the heat exchanger surface precipitation crystallization fouling, but also make the biological aggregation, growth and reproduction, the formation of biological fouling, particle fouling to promote a variety of fouling coexist, tight and difficult to remove.
5. Chemical reaction fouling:
The chemical composition of the fluid in the heat exchanger internal reaction, the formation of deposits.
6. Solidification fouling:
Inside the heat exchanger, certain fluid components solidify due to temperature changes, forming fouling.
Plate heat exchanger prevention and treatment of scaling of the six measures
Based on the six main types of fouling processes in plate heat exchanger operation, the following measures can be taken for prevention and maintenance:
1. Periodic Cleaning:
Establish a program of regular cleaning and use chemical or mechanical cleaning methods to remove dirt and deposits on the plates.
2. Water Quality Management:
Appropriate treatment of circulating water, such as softening, desalting, and sterilizing, to reduce dissolved solids and microbial content in the water.
3. Use of scale inhibitors:
Adding an appropriate amount of scale inhibitor to the circulating water prevents the formation of precipitated crystalline fouling and reduces the likelihood of scaling.
4. Control of flow rate and temperature:
Reasonable control of the flow rate and temperature of the fluid, to avoid particulate matter in the fluid deposited on the surface of the heat exchanger, while reducing the chemical reaction caused by temperature changes in fouling and solidification of fouling.
5. Periodic inspection and maintenance:
Regularly check the operating status of the heat exchanger, including pressure, temperature, flow rate and other parameters, as well as changes in heat transfer efficiency, timely detection and treatment of problems.
6. Filtering and pre-treatment:
Filter and pre-treat the fluid before it enters the heat exchanger to remove the particles and impurities in it and reduce the formation of particle fouling.
7. Optimized Design:
Optimize the design of the heat exchanger, such as increasing the cleanliness of the flow path, reducing dead space, using easy-to-clean plate structures, and selecting corrosion-resistant materials to reduce the risk of scaling.
Through these measures, the scaling problem of plate heat exchanger in operation can be effectively prevented and reduced to ensure the efficiency and operational safety of the heat exchanger.
