60- Discussion on the technical design to prevent clogging in the wet flue gas desulfurization and dust removal tower of fluidized-bed coal-fired boilers, using efficient feather-leaf separation demister dust collectors
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This post was last edited by luoli519 on 2022-11-30 at 18:33. In recent years, environmental protection authorities have imposed stricter requirements regarding the emissions from coal-fired boilers. Monitoring of flue gas emissions from coal-fired boilers is frequent. For owners who choose the wet flue gas desulfurization and dust removal process to treat the flue gas from fluidized-bed coal-fired boilers, there is a lack of experience in the design and selection of the demisting and dust separation components used in the wet desulfurization tower as the final stage of flue gas treatment, which has led to many detours. Some case information is provided here; friends are invited to discuss it together to improve design skills.
Some time ago, a company in Binzhou, Shandong Province, provided a set of wet desulfurization and dust removal equipment for a flue gas treatment project involving coal-fired boilers at a factory in Jiangsu. The final device for removing foam and dust before flue gas is emitted is a limestone packed tower. At the beginning of operation, the marble filler proved effective in capturing flue gas droplets and dust, despite being a very simple and traditional technical approach.
However, within less than two months of operation of the marble packed tower, a sharp increase in pressure drop was observed, as dust had clogged the marble packing. I had to stop the vehicle to carry out backflushing; as a result, the smoke had to be discharged through a bypass route. I was very worried, fearing that the environmental protection agency would catch me in the act.
At the strong insistence of the owner, this supplier was forced to add another set of marble packed towers as a backup, with one in use and one as a spare, to facilitate backwashing and regeneration in case the tower gets clogged. This eliminates the need to exhaust flue gas through a bypass during marble regeneration. The cost of adding an additional set of marble packed towers as a spare can obviously only be borne by the supplier itself. This was due to initial problems in the design choice of the equipment used as the final safeguard against flue gas emissions by this company in Binzhou, Shandong.
Soon, the owner planned to expand the project. Due to issues related to the site layout and space constraints, as well as investment considerations, they aimed to carry out partial upgrades based on the existing boiler flue gas desulfurization and dust removal processes and equipment. This supplier in Shandong naturally has the advantage of being first-mover. However, the flue gas volume has increased by nearly 3 times, and the original marble packed tower clearly does not have such a large operational flexibility or margin; therefore, it is necessary to consider modifying this marble packed tower.
The new dusty and humid operating conditions are: temperature of 60°C, pressure of 95 kPaA (absolute pressure), gas flow rate of 67,100 Nm^3/h, dust content of 200–500 mg/Nm^3, and liquid content of up to 5%.
While this company in Binzhou, Shandong was struggling with investment issues, an environmental protection equipment firm from Hebei approached it, stating that its swirl tube/swirl plate demisting and dust removal separators could help solve the company’s urgent problems. It assured the Shandong-based company that its swirl tube/swirl plate demisting and dust removal separator had the following features: 1. It could be installed in a stainless-steel tower with an original diameter of 2000 mm, with the installation height limited to 3000 mm. 2. The total amount of residual foam and dust in the airflow after defoaming and dust removal is less than 15 mg/Nm^3, and it can be discharged directly through the chimney. 3. Ensure that the demisting device operates continuously around the clock, with low operating and maintenance costs.
This company based in Hebei guarantees that the use of its swirl tubes/swirl plates can fully meet the requirements, and it cites a state-owned power environmental protection company that has also adopted its swirl tube/swirl plate demisters in the flue gas desulfurization and dust removal systems of various power plants. Since the owner and the company in Binzhou, Shandong, were unaware of the application of swirl tube/swirl plate demisters both domestically and internationally, and considering the tight deadline set by the local environmental protection agency for addressing emissions from the factory’s boilers, they paid a company in Hebei to carry out the design and supply work based on the operational conditions and the requirements for installing and operating such demisters.
This post was last edited by luoli519 on 2016-12-5 at 13:27. This cyclone/turbine plate demister manufacturer in Hebei provided a set of 19 cyclone/turbine plate demisters with a diameter of 300 mm and a length of 2500 mm, which were installed in a stainless steel tower with a diameter of 2000 mm. The image below shows the Hebei-based company at the site, installing the swirl tube/swirl plate demister components inside the tower at that time:
However, the actual performance of the swirl tube/swirl plate demisters used by this company in Hebei is very poor; it even falls short of the demisting and dust removal efficiency of the limestone-filled towers. The results of the trial operation of the cyclone/turbine plate demister at this company in Hebei, as measured by the Environmental Protection Bureau, showed that the total amount of residual liquid droplets and dust in the gas exiting the demister exceeded 150 mg/Nm^3.
The Environmental Protection Bureau, the property owner, and the buyer, a company based in Binzhou, Shandong, required the company in Hebei that supplies cyclone/turbine plate demisters to make the necessary corrections within one week. The company in Hebei sent its technical manager, who is in charge of the technical and commercial aspects of this project, to the site to deal with this issue. As a result, after a week of trying, the problem still persisted. The on-site technical manager sent by this company in Hebei has disappeared, and the company also says it has not seen him. The owner from Jiangsu and the supplier from Binzhou, Shandong, called the boss of this company in Hebei, but his phone was constantly off.