108- The Nuowei Energy feather separator operated efficiently and stably in the technical upgrade project to improve the emission standards of the sulfur processing unit at Dushanzi Petrochemical

Sulfur recovery exhaust gas treatment units and flue gas denitration and desulfurization units in the combined plants of domestic and foreign refining and chemical enterprises generally use foreign process packages, or process packages that have been developed by adapting foreign technology. After the implementation of the latest and strictest environmental standards for flue gas emissions in our country, the flue gas emitted by process units that originally used foreign process packages or developed such packages through the adaptation of foreign technologies often fails to meet the requirements of these new emission standards. It can be said that in order to fulfill its emission reduction commitments on the international stage and strive to become a pioneer and leader in global environmental protection, China’s newly introduced air emission standards should be among the strictest in the world.

In order to implement the latest environmental emission standards, provinces, municipalities, and regions have, almost unanimously, urged state-owned refining companies such as CNPC and Sinopec, as well as local refineries, to carry out upgrades to improve the standards for the emissions of their flue gases. State-owned refining and chemical enterprises such as CNPC and Sinopec, as well as local refineries, face considerable pressure from local environmental protection agencies; as a result, they submit requests to their corporate headquarters regarding these environmental pressures and seeking funding for upgrades and technological improvements.

This post was last edited by luoli519 on 2017-6-30 23:33. For the foreign process packages originally used in refineries, or the secondary process packages developed through adaptation and modification of such packages, the final step in treating the flue gas before it is released into the environment is the desulfurization alkali scrubber. Most of these towers use conventional packed-type demisters with relatively low requirements in terms of performance indicators such as separation efficiency, operational flexibility, and operational stability (such as the typical conventional packed EF-25 series), simple baffle demisters (such as the first-generation Chevron simple baffle plates), or simple rotary vane demisters (such as the Cyclolab water droplet separator). As a result, even slight fluctuations in operating conditions can lead to a rapid decline in the demisting efficiency, causing the flue gas emitted from the top of the scrubber tower to exhibit phenomena such as \"rainfall\" or even \"water splashing\". When the \"agent leakage\" condition occurs, the existing demister suffers even more severe blockage, leading to a sharp rise in pressure drop; as a result, flue gas cannot be transported smoothly, forcing the installation to shut down. The losses resulting from shutting down operations for cleaning, maintenance, and removing obstacles cannot be underestimated.

The flue gas emitted from the desulfurization and alkali washing towers in the refinery experienced issues such as \"water splashing,\" \"rainfall-like phenomena,\" and even excessive sulfate levels, due mainly to the following reasons:

This post was last edited by luoli519 on 2017-6-30 10:10. First, there are obvious design and selection mistakes, or even errors, in the gas-liquid separation components inside the scrubber tower. Domestic owners, design institutes, demister manufacturers, and process package suppliers, as well as many engineers from certain well-known foreign companies, often tend to rely on a simplistic approach based on experience, rough estimates, or even hasty decisions when dealing with gas-liquid separation technology, which is a technique based purely on dynamics. In this mode of operation, the gas-liquid separation internals produced may have issues; either the kinetic energy threshold for fluid flow through these internals is problematic, resulting in a separation regime that is not within the effective operating range, or there are problems with the configuration of the internals, leading to fluid contraction and causing certain areas of the intended flow surface to be in an abnormal separation state. Additionally, incorrect selection of internals may occur, with separation-type internals being chosen when mixing-type internals would be more appropriate. In fact, the importance of accurately designing the momentum and kinetic energy thresholds for gas-liquid separation in fluid dynamics, as well as the design of the internal component configuration system, is greater than that of selecting and designing the internal components themselves. If there are problems with the calculation of dynamic separation design and configuration design, or if accurate design is not even carried out using a precise dynamic separation technology platform, then even the use of the best separation-type internals will be of no use. This is why the process package supplier, design institute, and client require that the separator internals supplier, in addition to providing technical solutions and cost estimates for those internals, must also submit key technical documents such as hydraulic calculation reports for dynamic separation design, separation efficiency curves, and operating pressure drop curves. These documents are used to assess the scientific validity, accuracy, and reliability of their design solutions, as well as to serve as a basis for evaluating their performance in operation.

Secondly, the operating conditions within the scrubber tower fluctuate to a degree that far exceeds the maximum operating load and flexibility range of the gas-liquid separation internals in a given configuration. The vane-type high-efficiency gas-liquid separators obtained through kinetic separation calculation design and configuration design system platforms typically have an operating flexibility range of 15%-135% or even wider, which makes them the gas-liquid separation element assemblies with the greatest operating flexibility range available both domestically and internationally at present. However, if there are significant fluctuations in the conditions upstream of it, and the system components designed to handle such situations have obvious shortcomings or even defects, it often places a severe strain on the operational flexibility of the gas-liquid separation internals. As industry professionals are aware, when there is a leakage issue in the upstream system, the flue gas carries an excessive amount of heavy-phase entrainment substances beyond the design standards into the scrubber tower. The inlet pipe for the mixed-phase fluid in the scrubber tower usually adopts an opposed straight-cut design, which serves to pre-separate the flue gas entering the pipe and remove the heavy-phase contaminants, thereby enabling the flue gas to meet the required standards before it enters the subsequent secondary gas-liquid separator. However, it is imperative that the process package supplier, the design institute, and the owner’s engineers keep in mind that for the inlet separation assembly of the counterflow direct-cut type in wash towers, the kinetic separation technique for pre-separating the flue gas at the inlet and removing heavy-phase contaminants relies on the condition that the diameter of this inlet separation assembly does not exceed ~1/6 of the diameter of the wash tower. Otherwise, the separation capacity of the opposed straight-cut type inlet separation assembly for heavy-phase entrained substances in the flue gas will decrease significantly, causing the flue gas containing an excessive amount of such substances to enter the secondary gas-liquid separator directly. This poses a serious challenge and strain on the separation internals, which have limited operational flexibility, and may even force them to stop operating. Therefore, in the case where the diameter of the opposing straight-cut type inlet separation assembly exceeds ~1/6 of the diameter of the scrubber tower, please remember to consult NOVEL Corporation for a flow rectifier specifically designed for such assemblies. Otherwise, the secondary gas-liquid separator is likely to face many problems.

This post was last edited by luoli519 on 2017-8-2 at 17:41. Thirdly, after the reduction in diameter of the scrubber tower, the diameter of the chimney section becomes too small while its height becomes too large, resulting in a large temperature difference between the flue gas inside and outside the chimney. As industry insiders are aware, many such devices use a Venturi alkaline solution mixing reactor scrubber in the upstream process to remove sulfur from flue gas through direct contact, which results in a significant drop in flue gas temperature. Flue gas that has cooled down is not conducive to being drawn up through the chimney, and it often needs to be preheated again. Preheated flue gas indeed helps it rise in the chimney, enabling smoother exhaust ； However, due to the large temperature difference between the flue gas inside and outside the chimney, with the ambient temperature being much lower, the hot flue gas condenses into water mist or even turns into rain when it comes into contact with the cold environment, especially during autumn and winter. Therefore, some companies install a combined unit of \"flue gas heat exchange + high-efficiency gas-liquid separation\" on top of their chimneys. This unit not only recovers heat to reduce the temperature difference between the flue gas and the environment, thereby preventing the formation of distinct \"plumes\" of smoke, but also efficiently separates and captures the condensation droplets formed as a result of pre-cooling the flue gas, so as to avoid any precipitation. It should also be emphasized that the installation of a combined unit for \"flue gas heat exchange + efficient gas-liquid separation\" at the top of the chimney must also be designed using a precisely engineered dynamic separation platform, in order to avoid issues such as low separation efficiency, excessive operating pressure drops, and insufficient load handling for flue gas treatment. If the chimney has an excessively small diameter and a large height, the flue gas purified by the two-stage gas-liquid separator rises upward within the chimney. As a result of frequent and prolonged frictional collisions between the fluids as well as between the fluids and the inner walls of the chimney, many very small liquid droplets aggregate together and grow, resulting in a certain amount of liquid droplets suspended in the exhaust gas. Therefore, installing a combined device of \"flue gas heat exchange + high-efficiency gas-liquid separation\" at the top of the chimney also contributes to the removal of secondary liquid droplets and foam in such cases.

The “Sulfur Off-gas Upgrade Project for the Combined Unit of the Dushanzi Petrochemical Company’s Refinery” serves as the first successfully operational model unit in China’s petrochemical industry. It plays a positive role as a model and guide for helping petrochemical enterprises as well as other industries to upgrade their existing similar units so that they meet the latest environmental standards regarding flue gas emissions. These projects for upgrading identical or similar facilities include: 1. The upgrade project for Claus sulfur recovery exhaust gases, which applies to the petroleum refining industry, the new coal chemical industry, the natural gas processing and transportation industry, the fertilizer industry, as well as offshore oil and gas platforms and onshore terminals. 2. Project for upgrading the exhaust gas treatment system of the catalytic cracking flue gas denitration and desulfurization unit ； 3. Project for upgrading the exhaust gas treatment facilities for denitration and desulfurization in circulating fluidized bed coal-fired boilers in the thermoelectric industry ； 4. Project for upgrading the exhaust gas standards of denitrification and desulfurization equipment for flue gas from circulating fluidized bed coal-fired boilers in the HVAC and heating industry.

The last edit to this post was made by luoli519 on 2023-9-27 at 12:59. The vane separators provided by NOVEL Company for the project aimed at upgrading the sulfur off-gas treatment system in another combined unit at the Dushanzi Petrochemical Plant have arrived at the client’s site, ready to be installed and put into operation at an appropriate time.

The last edit to this post was made by luoli519 on 2023-9-27 at 12:59. The technical solution for the vane separator required for the upgrade of the flue gas denitration and desulfurization equipment at CNPC Wushihua Petrochemical has also been finalized.