161-Leaf-separated demister for the upgrade plan of flue gas scrubbers in the process main towers of refining enterprises and thermal power station boilers

Over the past two years, the refining and chemical industry has carried out upgrades to its existing flue gas treatment systems in order to improve the standards for flue gas emissions and address potential safety issues, especially among those companies located in the north where low winter temperatures result in poor flue gas dispersion conditions. Recently, there has been an increase in requests from some refining and chemical enterprises in East and South China to upgrade their existing flue gas scrubbers by installing vane-type demisters. Therefore, we will simply begin by discussing and analyzing its general technical key points here.

Here, an example of the technical upgrade of the original main tower and boiler flue gas tower of a certain enterprise in East China, using vane-type separation mist eliminators, is discussed in detail to help people understand the existing problems with such devices as well as the key aspects of the technical solutions that involve using vane-type separation mist eliminators.

This post was last edited by luoli519 on 2020-9-11 at 16:50. The attached image is a summary diagram showing that a petrochemical company in East China commissioned Nuowei Energy Technology Company, through Lanhun Environmental Protection Company, to carry out an upgrade using the patented technology of feather-leaf type mist eliminators:

As can be seen from the document, the unit originally adopted a “packing + mist eliminator” scheme. This is similar to the scenario we discussed in a previous thread regarding how PetroChina’s refining enterprises implemented the originally introduced WGS process package方案 from Exxon. That is, the flue gas entering the tower is first pre-washed by circulating slurry spray; after passing through the packing layer from bottom to top, it is washed again by a secondary spray before entering the demister, which is arranged horizontally along the radial cross-section at the upper part of the scrubber, to remove any solid and liquid particles carried in the gas.

Based on the original schematic diagram of the demister and its layout provided in the documents, the original demister was installed in a horizontal, horizontal orientation. The original plan called for the use of simple Chevron baffles similar to those used in thermal power plant flue gases, or EF-25 type packing blades. There is no dedicated independent liquid dropping system or gas seal system.

Based on the basic process data provided by the client, the original plan considered only the packing layout area and packing layer thickness from the perspective of flue gas mass flow rate, emphasizing the qualitative goal of keeping the operating pressure drop of the internal components as low as possible, while lacking quantitative metrics. The impact of dynamic separation characteristic parameters such as flue gas composition, operating temperature, operating pressure, gas phase density, gas phase viscosity, liquid phase density of the washing solution, liquid phase viscosity, and liquid phase surface tension on the operation of gas-liquid-solid separation was not considered. It should be noted that the technology for separating the liquid-solid mixture from the gas stream belongs to the category of kinetic separation techniques, and focusing solely on the mass flow rate of the flue gas is far from sufficient.

The packing blades used in the aforementioned flue gas treatment not only have low separation efficiency and unstable operation, but they also tend to accumulate dust particles, which can block the internal flow channels and lead to a sharp increase in operating pressure drop. From the on-site photos of the filler blades and internal components separating after the devices were operated, shown in previous discussions on related technical topics, one can truly appreciate the tricky problems faced during actual operation.

The original condition of the main tower provided by the East China owner in the documents is as follows: 1. Tower diameter: 4500 mm； 2. Tower height: 9400 mm ； 3. Chimney diameter: 1800 mm ； 4. Flue gas treatment capacity: 145.8 t/h. Among them, the original filler height is 650 mm. The height of the original packing demister is unknown. As shown in the attached figure

Following detailed discussions with the owner to gain a better understanding of the conditions of the original installation, and based on the actual operating conditions while making full use of the existing wash tower shell and packing and leaving the existing pipelines and instrumentation unchanged, the main specifications of the vane-type separation demister were determined through NOVEL’s precise dynamic separation calculations and configuration design system platform. These specifications are as follows: 1. Model of the vane-type separation demister: NOVEL P4-177-73; all components are made of SS316L material； II. Model of the vane-separated demisting internal component set: NOVEL P4-D BANK-144/4-60-EDP, equipped with a new type of liquid dropping system designed to prevent \"siphon short circuits\", and features a detachable modular configuration ； III. Model of internal components for the online cleaning system: NOV-135-16W-120*4; swirl jet type ； IV. Design processing capacity: The design processing capacity is based on a gas phase flow rate of 145.8 t/h under operating conditions ； V. Separation efficiency guarantee: Under normal operating conditions, the separation efficiency for liquid droplets with a diameter of 12.05 microns or larger is 99.99%, and the amount carried in the gas exiting the separator is less than 0.1 Gal/MMSCF ； VI. Operating pressure drop of the feather-leaf separation mist eliminator: Under normal design conditions, the operating pressure drop shall not exceed 0.064 psi ； VII. Operating flexibility range: 10%~130%. The vane-separated demister designed to prevent clogging in the flue gas scrubber towers provided by Novay Energy Technology Company is supplied as a complete skid-mounted unit. It undergoes comprehensive testing before leaving the factory, and at the installation site, the entire skid-mounted vane-separated demister is installed in the scrubber tower. This ensures that the configuration and performance of the demister once it is installed in the tower are exactly the same as those tested prior to departure from the factory, thereby effectively avoiding various structural and performance defects as well as potential risks that may arise from attempting to assemble the components on-site when overall testing conditions are not available.

This post was last edited by luoli519 on 2024-4-7 at 10:58. The figure below shows the \"Data and Diagram Summary\" for the specialized vane-type demister designed for the owner’s main tower, developed by Nuowei Energy Technology Company using its precision dynamics separation calculation and configuration design system platform: