106- Discussion on the design of a vaned demister for the vapor drum of the ethylene oxidation reactor in EO/EG plants
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This post was last edited by luoli519 on 2023-9-27 at 13:05. The domestic and international value chains for the deep processing of ethylene typically involve the production of ethylene oxide from ethylene, which is then used to manufacture ethylene glycol and its polyether derivatives. Among them, the oxidation of ethylene to produce ethylene oxide is the primary key step. The efficient demister used in the high-pressure drum of the oxidation reactor requires vane-type separation internals in all three process packages. Please take into account the operating conditions of your own facilities, and discuss the necessity of using vaned separation internals in the high-pressure drum demisters of the oxidation reactors involved in the three major EO/EG process packages worldwide.
As is well known, the process packages used in the EO/EG units of petrochemical companies both domestically and internationally are often those provided by SD, DOW, and ABB. For the projects carried out in the past two years, the process packages from the American company SD have been used more frequently. In China, the engineering companies with experience in designing EO/EG plants are essentially SEI, HQC, and SSEC.
This post was last edited by luoli519 on 2017-6-13 at 22:05. We have worked with each of the three aforementioned engineering companies, providing professional design, manufacturing, and supply services for dynamic separators used in various components related to three overseas EO/EG process packages – including high-pressure drum demisters, vapor-liquid separators in high-pressure drum steam generation pipelines, pre-condensers and KO tanks in the decarburization unit regeneration towers, demisters in CO2 concentration towers, and demisters in exhaust gas absorption towers. Our work was highly praised by the process package providers, engineering companies, and project owners, and we continue to maintain good technical consultation relationships with them to this day.
The oxidation reaction generates a large amount of heat, which is removed by the generation of large quantities of steam from the saturated water in the steam drum. For the reactor drum, a high-efficiency vaned demister with a large steam handling capacity, high operational flexibility, stability, and efficiency is selected. This type of demister prevents liquid droplets and mist carried by the steam from accumulating in downstream pipelines, thereby avoiding \"liquid resistance\" that could lead to poor steam flow and fluctuations in system pressure. It also enables the efficient capture and recovery of the large amount of saturated water droplets and mist carried by the steam, **thereby reducing the costs associated with the addition of external deionized water.
Furthermore, if the drum demister fails to meet the requirements for efficient and stable demisting and separation under conditions of high steam flow rates, high liquid load levels, high operational flexibility, and wide variations in operating conditions, it will inevitably lead to the accumulation of liquid droplets and mist carried by the steam in the downstream pipelines, creating a \"liquid resistance\" that hinders steam flow and causes fluctuations in system pressure. These pressure fluctuations in turn result in temperature fluctuations in the reactor, thereby triggering a vicious cycle of oxidation reactions. This not only affects reaction efficiency, selectivity, and product quality but can also pose safety risks.
This post was last edited by luoli519 on 2022-11-30 at 18:05. The figure below shows the data sheet for the oxidation reactor drum and the vaned separation internals required for a certain EO/EG project process package:
As can be seen from the requirements for the location of demisters specified in the process package technical specifications in the figure above, each high-pressure drum of the reactor requires two sets of efficient demisters to be installed at the beginning of the steam outlet pipe on the inside of the drum.
This post was last edited by luoli519 on 2022-11-30 at 18:06. The operating pressure of the high-pressure drum in this reactor varies between 2.963 MPa and 5.848 MPa, while the steam flow rate ranges from 12,910 kg/h at 2.963 MPa to 137,670 kg/h at 5.848 MPa. It is required that 99.5% separation of liquid droplets and mist with a size of 70 microns or larger be achieved under the condition of Fs=1.22 (m/s)(kg/m^3)^0.5. It is evident that traditional screen-type demisters, swirl-type demisters, and conventional Chevron baffle plates are unable to achieve stable and efficient demisting performance under such wide fluctuations in operating conditions; only the vane-type demister can meet these technical requirements.
The process package suppliers, engineering companies, and the owner all require that the designer and manufacturer of the demister provide the corresponding hydraulic calculations for dynamic gas-liquid separation, separation efficiency curves, and operating pressure drop curves, in order to demonstrate the accuracy and reliability of such designers and manufacturers in creating efficient gas-liquid demisters.
Indeed, the vapor-liquid separator belongs to the category of dynamic separators; an accurate configuration of the demister system must be obtained through dynamic separation calculations, and the exact installation positions of the internal components must also be determined using specialized dynamic separation calculation systems. The same set of internal components cannot be installed at any arbitrary position at the beginning of the steam outlet pipe on the inside of the drum ； If the internals are not installed at the exact positions determined by the system designed for separation calculations based on proprietary dynamics, the effect of airflow contraction will cause some of the internals to operate abnormally or even not to function at all, thereby preventing them from meeting the demisting requirements specified in the process package.
This post was last edited by luoli519 on 2024-4-3 11:06. The components of the vane-separated demister provided by our company for this project are shown in the figure below: