125- The essential difference between the special feather leaf separator for the flue gas desulfurization scrubber of the heavy oil catalytic device and the flue gas desulfurization curved cone dust collector

Regarding the actual case of the feather leaf separator being used in the heavy oil catalytic cracking unit flue gas desulfurization scrubber chimney "rain elimination" and "dust reduction" technical upgrading and transformation, it has been posted in the Haichuan Forum technology special post https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=1944683 For in-depth analysis and discussion, please refer to this post. This post only provides a necessary brief introduction.

This post was last posted by luoli519 on 2023-9-27 10:07 Editor: Cyclone dust collectors are also called "curved cone" dust collectors in China based on the shape of their tapered tubes. They were first used abroad in the 1940s for the primary separation of gas-solid and gas-liquid-solid, such as coal mill tail gas primary cyclone dust collector + subsequent bag dust collector, and power plant boiler flue gas lime wet desulfurization tower primary cyclone tube lime slurry foam + subsequent secondary and tertiary baffle washing demisters, etc. Due to the limitations of the separation principle and internal structure of the cyclone tube itself, it has only been used in foreign countries for primary dust removal and separation of air flow. Subsequently, it must be equipped with a secondary and third-stage separator to further separate the air flow. Cyclone dust collectors often only have a single-stage and at most 2-stage separation unit structure. The separation efficiency of each stage set through the accurate dynamic separation system platform design is between 85-95%. The heavy phase mass residue of the flue gas at the outlet of the 2-stage cyclone dust collector estimated at 10% average residue (i.e. 0.1) is about (0.1)^2=1%. The emphasis is on "dust removal"” ； Often because the density of large particles is much higher than the density of light phases such as airflow and liquid droplets, dust removal and separation are relatively simple. For small, medium and micro-sized dust particles, dry cyclone cannot achieve effective "dust removal".” ； Cyclone dust collectors often must use reverse high-intensity spraying to wash small, medium and micro-sized dust particles carried by the airflow in order to achieve "dust removal" "indirectly". In short, "low-level cyclone tubes must + high-intensity spraying to remove dust from the flue gas." However, it often causes more liquid droplets to be carried in the flue gas, causing serious problems such as "rain" in the chimney and "frozen ground in winter". Therefore, in order to remove dust particles mainly distributed in small, medium and micro sizes from flue gas, the cyclone dust collector must turn on the reverse high-intensity spray scrubbing airflow. Otherwise, the cyclone dust collector cannot truly achieve the "dust removal" effect. The negative effect is that more liquid droplets are carried in the flue gas, causing serious problems such as "rain" in the chimney and "freezing on the ground in winter". Feather leaf separators generally have a separation unit structure of more than 4 stages. For demanding separation situations, a separation unit structure of more than 6 stages is required. The separation efficiency of each stage set through the design of the accurate dynamic separation system platform is between 85-95%. The heavy phase residue of the flue gas at the outlet of the 4-stage feather leaf separator estimated at 10% average residue (i.e. 0.1) is about (0.1)^4=0.01%. The emphasis is on "demist removal"” ； In addition to separating large-sized heavy phase substances, it can also achieve efficient separation of tiny-sized, dust-containing and salt-containing droplets produced by flue gas scrubbing through synergistic methods such as momentum separation, coalescence separation, vector field separation, and liquid foam surface free energy capture and separation. The feather leaf separator can achieve the separation of micro-sized particles by further efficiently removing salt and dust that are dissolved and condensed in the micro-droplets in the flue gas. Although the feather leaf separator itself has an airflow self-cleaning function, some owners require the installation of an intermittent online flushing device to prevent the precipitation and crystallization of dust and salt particles. Generally speaking, the flushing frequency of installing an intermittent online flushing device on the feather leaf separator is generally 15-60 seconds per shift (8 hours). The operation of the feather leaf separator will not cause "rain" in the chimney or "frozen ground in winter".

This post was last edited by luoli519 on 2023-9-27 09:58. The cyclone dust collector was introduced into the country from abroad by visiting scholars sent from China around the 1990s. It was used by foreign companies in the primary separation of power plant boiler flue gas lime wet desulfurization towers + subsequent secondary and third-stage baffles to control washing and defoaming. However, domestic devices can only imitate the shape and structure of the cyclone tube, and do not have an accurate design platform model for the gas-liquid dynamic separation technology of the cyclone tube. The stability and reliability of the actual application effect are difficult to effectively solve, which in turn affects the subsequent operating conditions of the secondary and third-stage separators. Colleagues may be aware of the indicators of flue gas emissions from chimneys after desulfurization in thermal power plant boilers in the past. What's more, in recent years, without mastering the precise dynamic separation calculation design model and without conducting in-depth research on the application scenarios of similar foreign equipment, some profit-driven engineering company personnel have actually entered the cyclone equipment design into the precision separation process node of their projects. The owner later had to invest in technical upgrades and replacements, and suffered a lot. The same type of stainless steel cyclone separator provided by NOVEL for the design of foreign process packages through a dedicated precise dynamic separation calculation and design platform can only be used for primary separation of 10^2 microns to 10^3 microns in the air flow. It cannot be used alone to meet the technical requirements of "elimination of rain and dust" for flue gases. Secondary feather separation technology must be further used to complete subsequent deep separation. What's more, some swirling cones are created based on experience and rough estimation?

This post was last edited by luoli519 on 2019-12-18 12:46 Let’s first take a look at the picture of a single cyclone tube: 1. The shape of a single swirl tube is a tapered tube with a large diameter at one end and a small diameter at the other end. 2. A set of rotary vanes or two sets of rotary vanes are arranged in the middle of the cone tube. One set of rotary vanes is called a curved cone (usually the length of the spinal canal is 1200mm-1300mm), and two sets of rotary vanes are called a hyperbolic cone (usually the length of the spinal canal is 1500mm-1700mm). The more rotary vane groups there are, the operating pressure drop will be doubled and the water consumption will be doubled, but the separation efficiency will not increase much. The number of rotary vane groups should usually not exceed two groups, otherwise, the pressure drop will be too large and cause pressure suppression. 3. The washing water pipe is connected to the rotary vane head through the cyclone tube for water distribution. The water distribution density of each group of rotary vane cross-sections is not less than 30L/m^2/minute (domestic minimum standard) - 40L/m^2/minute (international minimum standard). Generally speaking, the water consumption of cyclone tubes is often higher than that of other equivalent separators. 4. The swirl pipe, water inlet pipe and sealing ring are usually made of plastic, ceramic or metal casting or welding. Swirl tubes made of injection molded plastic (often polyvinyl chloride (PVC)) are the most common and are often used in power plant boiler flue gas desulfurization towers. They are low-cost, easy to deform and collapse, and have poor aging resistance. They require frequent maintenance and replacement of parts, and high operation and maintenance costs. They cannot be used to withstand hot and cold alternating temperature conditions, especially abnormal accident conditions. The cyclone tubes used in flue gas desulfurization towers in some thermal power plants even need to be completely replaced in about three years. Therefore, the material of the separator for flue gas desulfurization must be stainless steel.

This post was last edited by luoli519 on 2019-7-2 14:26. ​​So, what does the internal rotary vane covered by the cyclone tube jacket look like? Please see the picture below: Some people may say, isn’t this a ceiling fan or an umbrella? Yes, there are also ones called "paradynamic separators" or "fan-shaped separators" from the appearance. It is mainly necessary to grasp the following points about the internal rotary vane:: 1. The airflow passes through the rotary vane from the cone end and mixes with the washing water flowing out of the rotary vane head to wash away some large particles. ； At the same time, more droplets and droplets generated by the rotary vane head are carried by the airflow and enter the airflow. Compared with other equivalent separators, the pressure drop of the rotary vane doubles, the water consumption doubles, and the amount of liquid carried by the outlet airflow doubles. 2. Since the flue gas scrubber usually operates under normal pressure, the pressure drop generated by the cyclone tube cannot exceed 2kPa. ； Otherwise, the smoke will be trapped in the chimney, causing "obstruction" and poor exhaust. Due to the pressure drop limitation, the flow rate of the airflow through the swirling blade cannot be large. The centrifugal acceleration generated by the rotation of the airflow is "weak centrifugal", and the acceleration is much lower than the acceleration of gravity G. Its separation effect is not ideal and can only be used for primary separation. 3. Different from the internal parts of the feather blade separation, which have a "structure where the gas and liquid flow directions are orthogonal to each other and the flow channels are independent of each other", the swirl blade does not have the "structure of a structure where the gas and liquid flow directions are orthogonal to each other and the flow channels are independent of each other". Its internal structure determines that obvious gas and liquid entrainment will occur during the operation of the swirl blade, resulting in unsatisfactory separation efficiency and operating pressure drop. 4. Since the connection line between the rotary vane and the external tapered tube is the thin peripheral edge of the rotary vane, which has low strength and is volatile, it is necessary to thicken and reinforce the peripheral thin edge when forming the rotary vane. Even if the outer periphery of the rotary vane is thickened and reinforced, when it cooperates with the inner wall of the tapered tube, it often produces excessive deformation or even damage, which is difficult to detect, resulting in high breaking noise and low separation efficiency during actual operation.

This post was last edited by luoli519 on 2019-7-2 14:26. ​​As the primary separation component, the curved cone cyclone dust collector is arranged in the washing tower as shown below.: 1. The diameter of the swirl cone that has been accurately calculated, designed and verified abroad by the dynamic separation model is fixed at 4 inches. The diameter of the swirl cone cannot be changed at will, otherwise its separation efficiency will drop significantly. The separation efficiency is inversely proportional to the diameter of the swirl cone. The larger the diameter, the lower the separation efficiency. For a scrubber with a given flue gas operating condition volume flow rate, there is a corresponding minimum lower limit number of swirl cones when meeting the separation efficiency and operating pressure drop technical requirements. ； If the swirl cone is used as the primary separation internal component to modify the original scrubber, it is likely that the cross-section of the original scrubber will be difficult to accommodate and arrange the swirl cone with a minimum number determined based on the principle of dynamic separation. Therefore, based on the conflict between the minimum number of swirl cones determined based on the dynamic separation principle and the cross-sectional area of ​​the original scrubber, even if the owner agrees to use swirl cones as primary separation internals to transform the original scrubber, not all scrubbers can use swirl cones as primary separation internals to transform the original scrubber. In order to reduce the lower limit of the number of swirl cones required in the renovation of a certain tower, some domestic companies completely ignored the technical requirements of dynamic separation and took it for granted to increase the diameter of the swirl cone to 12 inches, which is three times the international standard curved cone size of 4 inches. ； Although the flow cross-sectional area of ​​a single swirl cone has increased to 9 times, the lower limit of the number of swirl cones required in the renovation of a certain tower has dropped to nearly 1/10 of the minimum required number of curved cones of international general size, and the cost of renovation is * * Reduced, but the separation efficiency is certainly far from the technical requirements. 2. Hundreds or thousands of cyclone cones require limited space in the washing tower at the project site. For example, the Terracotta Warriors array is arranged in multiple groups on the positioning holes on the cross-section support plate in the tower, and is fixed by sealing and fastening rings. It is difficult to install and maintain, and it is difficult to find which swirl cones have problems. Even if a quality problem is found, it is very difficult to repair it alone, and it is often left alone. For rubber seals and plastic water supply pipes, tapered pipes, etc., if they appear to be deformed, aged or cracked, they can only be dismantled and reinstalled as a whole during the next overhaul of the device. This kind of hundreds or thousands of swirl cones are assembled on-site in the scrubber. It is impossible to conduct an overall pre-operation test on the entire swirl cone internal assembly formed after installation at the assembly site. It is difficult to determine whether the entire swirl cone meets the design requirements. The feather leaf separator needs to be tested as a whole after the final assembly of the internal parts before leaving the factory, shipped as a whole, and implanted into the scrubber at one time in the overall factory attitude after the final assembly test, so as to ensure that the internal parts of the feather leaf separator implanted in the scrubber have the same overall test results as its factory final assembly. 3. The main washing water pipe is introduced from the outer wall of the upper tower of the curved cone assembly to the inner wall of the tower, enters the washing water branch pipes in series, and supplies water to the lower swirl cone group through the program controller in groups. The wash water is mixed with the bottom-up air flow in the cyclone cone to elute large-sized particles in the air flow and flows into the bottom liquid phase collection area, and then is discharged to the lower part of the tower through the pipeline.

This post was last edited by luoli519 on 2018-10-20 18:57 Some colleagues are very familiar with Berg process equipment. After seeing the layout diagram of the curved cone in the tower above, they will definitely ask, isn't this similar to the filtration module? Isn't this similar to kinetic waves? Colleagues, be wise! The principle and internal arrangement of curved cone dust removal are similar to those of the filtration module and power wave. That is, the upward swirling airflow is reversely washed by downward reverse spraying to remove part of the dust particles carried by the airflow. The washing liquid droplets and foam will be carried by the airflow and dispersed into the airflow. The secondary airflow carries a large amount of liquid. The curved cone, filter module and power wave have a certain effect on airflow washing to remove some dust particles, but they have no obvious effect on the droplets and foam carried in the original airflow. On the contrary, the airflow carries more droplets and foam due to the reverse spray cleaning airflow. And the dust removal efficiency of the curved cone is far different from that of the filter module and power wave! Can't be compared. This is why we have replaced the cyclone dust collector with feather leaf separators in recent years.

This post was last edited by luoli519 on 2019-12-18 12:49. Below is a physical picture of the installation of the primary cyclone dust collector in the flue gas desulfurization scrubber of a fluidized bed coal-fired boiler provided by a company in North China for everyone to identify. I believe that after seeing this picture, you will be surprised to find how many cyclone dust collectors are around you and me. We need to pay attention to them and remind users to pay attention to them. This kind of cyclone tube made of PP material is installed in the flue gas desulfurization tower. Even if the front end is equipped with an expensive temperature control system, the slurry circulation pump outage and FCCU "running agent" conditions that are not uncommon in the scrubber tower will cause the cyclone tube to deform and collapse, and then have to find another technical transformation.

This post was last edited by luoli519 on 2018-7-10 15:48 The curved cone cyclone dust collector is also a dynamic separation technology equipment. Its separation efficiency and operating pressure drop are a contradiction. The higher the operating pressure drop, the higher the separation efficiency. On the contrary, if the operating pressure decreases, the separation efficiency will be low. According to the international standard size cyclone cone tube determined through precise dynamic separation calculation and configuration design system platform, the operating pressure drop of a single-stage cyclone cone corresponding to a separation accuracy of 10^1 microns is generally around 2kPa. When the operating pressure drop of the single-stage cyclone cone required for smooth emission of chimney flue gas is less than 1kPa, because the flue gas flow rate is too low, the centrifugal acceleration generated by the airflow rotation is much less than 1 gravity acceleration G, and the corresponding separation accuracy is on the order of 10^2 microns to 10^3 microns. It is difficult to achieve the purpose of "eliminating rain" from the chimney flue gas. If a two-stage swirl cone is used and its cumulative operating pressure drop is required to be less than 1kPa, this means that the operating pressure drop of a single-stage swirl cone is only half of the total pressure drop, and the separation efficiency is even lower. The washing water sprayed from the swirl cone has a certain elution effect on larger-sized particles in the flue gas, but the small and medium-sized washing water droplets will be newly carried into the flue gas, which will instead add new loads to the "rain elimination" of the flue gas. The greater the number of swirl cone stages, the greater the cumulative load newly carried by wash water droplets and foam into the flue gas.

This post was last edited by luoli519 on 2019-7-2 14:27. However, some non-professional kinetic separation technology companies actually stated it in black and white in the heavy catalyst flue gas desulfurization scrubber chimney rain and dust reduction plan provided to the owners of refining companies in the system.: When the operating pressure drop is less than 0.6kPa, its curved cone separation efficiency exceeds 99.5% for droplets of 5 micron size. ； The separation efficiency for droplets of 10 nanometers (0.01 microns) exceeds 90% ； And it is clearly marked as "Nano Curved Cone Mist Eliminator". See screenshot below. These sensational titles and plans obviously come from some non-professional dynamic separation technology companies, bullying owners and design institutes who do not understand separation technology! But when it was actually tested for operation, it fell far short of the targets in its plan, causing harm to others and itself! Colleagues know that the dispersed phase in the airflow with a size below 3 microns already has aerosol characteristics. The smaller the size of the dispersed phase in the airflow, the more obvious the aerosol characteristics. Internationally, the lower limit size that can effectively separate and remove the dispersed phase in the air flow is 0.1-0.3 microns. The removal of dispersed phases with a size below 0.1 micron (i.e. 100 nanometers) in the air flow is a technical problem that the international community has gathered global technical resources to tackle for decades but has not made significant progress in recent years! The curved cone dust collector belongs to the same technology as the filtration module and the power wave dust collector, and its separation efficiency is lower than the filtration module and the power wave dust collector. Its actual separation efficiency is foreseeable. Structure determines performance! The curved cone that lacks "the light and heavy phase flow directions are orthogonal to each other and the light and heavy phase flow channels are independent of each other" has been abandoned or even eliminated by many international professional dynamic separation technology companies. However, the "nano curved cone" suddenly appeared on the rain and dust reduction solution provided to the fume removal scrubber of the heavy catalyst unit of the refining and chemical company in the system, and it was marked that "when the operating pressure drop is less than 0.6kPa, the separation efficiency of its curved cone for droplets of 5 micron size exceeds 99.5%." ； The separation efficiency of 10 nanometer (0.01 micron) droplets exceeds 90%." It is worthy of reflection by peers!