2024-03-11
Application of drum adsorption dryer in process industry
The drum adsorption dryer is widely used in the process industry-electric power, chemical, pharmaceutical, water treatment and other fields, and is an important part of on-site air post-treatment. Individualized field environments are also increasingly demanding for the selection of suitable dryers. This paper introduces the application of the drum adsorption dryer provided by Liankesi in the electric power, chemical, pharmaceutical and water treatment industries.
electric power industry
Detection of moisture content in SF6 gas in high voltage switch
In voltage delivery (100kV to 400kV) power distribution networks, power switching or load current interruptions are often caused by arcs between two contact points. SF6 insulation, with pressure SF6 can effectively control the formation of arc. However, over time, the ingress of moisture causes SF6 to decompose into other products, such as fluorohydrides. This will not only affect the operating performance of a single device, but also when the moisture content is high, the by-product will include strong corrosive hydrogen fluoride, which will accelerate the corrosion of the switch contact, cause physical damage, and will spread to other areas within the circuit breaker enclosure, aggravate the damage degree, and bring safety hazards to people and equipment.
The moisture content of new bottled SF6 supplied by the industrial gas supplier should be checked before use, and the circuit breaker supplied by the circuit breaker manufacturer should be checked before use. During the storage of SF6 bottled gas, moisture can easily enter from the entrance. If well preserved, the moisture content of SF6 should be <10ppmv, equivalent to atmospheric dew point <-60 ℃. At the manufacturer of the circuit breaker, the enclosure of the circuit breaker shall be purged with dry gas during the final stage or during internal maintenance work before pressurization and sealing with SF6. The most common practice is to use bottled high-purity nitrogen or other inert gas to purge the water into the atmosphere by repeated pressurization until the moisture content in the enclosure drops to 10ppmV, which is equivalent to a normal pressure dew point of <-60°C. During on-site inspection/continuous monitoring, the moisture content in SF6 must be controlled at <100ppmv, which is equivalent to a normal dew point of <-42°C.
Detection of Moisture Content in Hydrogen for Generator Set Cooling
The thermal conductivity of hydrogen is much higher than that of other gases, so in the power generation industry, the common practice is to use hydrogen to directly cool the stator coils of the generator set. Since the shell of the generator set cannot be sealed, moisture in the surrounding air is likely to invade into the unit, and the heat exchange opportunity generates gaps due to aging, and moisture will also penetrate into the hydrogen. Therefore, the hydrogen circulation loop must be equipped with a dehumidification dryer to continuously remove the absorbed moisture. Otherwise, the moisture in the hydrogen gas will cause the exposed metal parts to condense and cause flashover phenomenon and even cause heavy losses. If the hydrogen dew point exceeds the upper limit, emergency measures should be taken immediately, or stop using and repair the generator, or immediately re-pressure the pump to pump dry hydrogen into the system.
water treatment system
The water treatment industry is now increasingly using ozone (O3) instead of chlorine to treat pure water. There are four main applications: drinking water, food production water and pharmaceutical production water, swimming pool water, sewage treatment and disinfection before circulation. In view of the high cost of chlorination processes and the health and safety risks associated with water transport and chlorination system applications, the water treatment industry has consistently used ozone disinfection in recent years. Ozone and chlorination have the same water treatment effect. They are both powerful oxidizing media that can attack impurities in the water (especially for microbial media) and split them into harmless residues after filtering the water system. The advantage of ozone is that when it acts on microorganisms, it fission into completely harmless oxygen atoms. [page]
The working principle of the ozone generator is very simple. Pure air or oxygen through the reaction unit (ceramic or stainless steel) between the two electrodes of the high voltage discharge (generally 12000V), high voltage causes the reaction between oxygen atoms, the formation of stable ozone molecules. A typical ozone generator must use compressed air from a standard regenerative dryer, fed to the ozone generator from a set of reaction vessels like a heat exchanger. The following three necessary reasons determine the moisture in the air or oxygen of the process must be measured: to prevent the generator electrode from arcing, to prevent the system parts from corroding due to acid formation, and to increase the ozonation efficiency. If there is a lot of moisture in the gas entering the generator, it will cause the electrodes to arc. In extreme cases, the electrode will contact and break the chamber wall. Arcing will damage the electrodes and the housing of the system, eventually leading to system breakdown and expensive repairs. The side effects of arcing in the presence of ozone can cause nitrogen and water to form acids and other nitrogen compounds, causing corrosion of electrodes and system components, which can also cause the ozone generator to fail. The efficiency of an ozone generator is inversely proportional to the moisture content of the input gas. If the moisture content is reduced from 50ppm to 5ppm(-50 to -70°C dew point), the efficiency of the generator can be increased by 20%. The general technical index stipulates that the minimum dew point of the input air or oxygen is -50 ℃, but if the drying can be accurately controlled, it can be reduced to -70 ℃ dew point, then the working efficiency and life of the generator can be significantly improved and improved.
Pharmaceutical Industry
The industry has very low requirements for the dew point temperature of dry air. When the fluid air bed system is used to dry the compound, the dew point is generally -40 ℃. In addition, the cooling stage before the material packaging should be strictly prevented from generating moisture again. All of these occasions require precisely controlled, repeatable environmental conditions and traceability. In most cases, the user will choose a relative humidity sensor, but if you want to accurately control within the range of 2% or 1.5, you are at the critical point of the measurement accuracy of this type of instrument or exceed the measurement capability of the instrument. Therefore, the best solution is to use Optidew with an accuracy of ± 0.1~0.2 ℃ dew point (see Figure 3) or S4000Integrale integrated (depending on the required accuracy),± 1 ℃ dew point CermetII or Transmet,± 2 ℃ dew point EasidewOnline (see Figure 4) or Easidew transmitters. These meters can provide accurate humidity measurement and achieve the purpose of precise control of the dehumidifier.
petrochemical industry
catalytic reforming of petroleum products
During the catalytic reforming of refined petroleum products, it is essential to control the moisture in the recycled hydrogen in order to ensure the operational efficiency of the plant. Excessive moisture content, such as greater than 50ppmv, can lead to catalyst poisoning, which means increased costs. In addition, if the moisture in the recycle gas is not maintained within the optimal range of 20 to 30ppmv, the chemical reaction efficiency will be reduced, which will also affect the product yield. During this stage, hydrogen chloride must be injected into the gas stream during the refining process to supplement the hydrogen content for periodic regeneration and conditioning of the catalyst. The humidity transmitter should be isolated from the process sample gas to avoid the attack of hydrogen chloride and the concomitant increase in moisture content. At this point the moisture content can be as high as 2000ppmv or even higher.
PET industry
Before injecting PET into the mold press, it must go through the process of drying and extrusion to improve the appearance and quality of the finished product by reducing the free moisture content. Precise control of the drying process is the primary process to ensure product quality (strength and aesthetics) can not be ignored. In the solid state, PET absorbs moisture from the air until it is in equilibrium with atmospheric moisture, and this hygroscopic behavior means that 0.6 percent of its weight is moisture. In order to ensure the performance of the polyester product, the moisture content must be reduced to 0.003%(30ppm) before heating. This is because during the heating stage, the contained moisture will rapidly hydrolyze the raw material, thereby reducing the molecular weight and impairing the physical properties of the polyester product. The process is carried out in the hopper loading base, which is treated by the hot dry air stream emitted by the dehumidifying dryer. The general process is to expose these materials to air having a dew point temperature below -40°C for a period of time. It is then carried to another hopper for transfer to the mold press. The general production plant will have 10 to 50 such dryers and mold presses.
Reel, moisture, content, dew point, ozone, conduct, hydrogen, sf6, air, system
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