Clogging of the control slats of the inlet pipe into the electrostatic precipitator.
1. Brief description of the technology.
Flue gases contaminated with ash from the boiler flow through the inlet pipe to the active part of the electrostatic precipitator (ESP). The temperature of the flue gas entering the electro separator is 150 [°C], the vacuum is 108.6 [Pa] on average. For the correct operation of the electrostatic precipitator, it is important to guarantee an optimal flow of polluted flue gases in the inner part.
The distribution of the flue gas flow affects the overall performance of the electrostatic precipitator. It is therefore necessary that there is a uniform speed of flue gases in the entire cross-section, as this ensures maximum capture efficiency in the electrostatic precipitators. The manufacturer of the device always suggests such measures to ensure an even flow and thus avoid the diversion of flue gases from the electric field.
That is why there is a so-called diffuser on the entrance part of the ESP, where dividing walls made of perforated sheet metal are usually placed. Their function consists in the uniform distribution of gas in the active cross-section of the device. Directing blinds (directional plates) are mounted in front of the diffuser on the inlet part of the pipe.
What problem are we solving here?
On the technology in question, there was an uneven flow of flue gases, because our built-in internal shutters on the inlet pipe were getting clogged. The ash settled mainly in the area of the lower right part. The space between the individual slats should be covered up to the height of 2/3 of the flow profile, see the attached picture. In this case, we can no longer talk about the optimal flow of flue gases in the entire cross-section of the internal space of the electrostatic precipitator.
2. With the given problem, we turned to the manufacturer of the filter equipment (ESP) and introduced him to our proposed solution for our customer. Here, we wanted to use acoustic energy for cleaning blinds.
We received a reply from the equipment manufacturer that this method of cleaning the slats is not suitable. Since a large amount of dust could be released when using the acoustic horn. This could clog the first rows of electrostatic precipitator.
Since the device was already out of warranty, the decision to carry out any tests was only for the consideration of the operator and our company.
He agreed to allow us to test the acoustic horn for the given technology, so we proceeded to install the technology and then started the test operation.
3. We mounted the acoustic horn on the inlet pipe leading to the EPS at the height of the blinds. The goal of the acoustic horn was to continuously eliminate the drafts arising on the control shutters and thereby ensure a better distribution of the flue gas flow in the EPS and achieve a reduction in the emission values of solid pollutants. Of course, we took seriously the idea of the equipment manufacturer that we must not clog the first rows of waste of the EPS.
4. The acoustic horn is active for 10 seconds and the delay time is set to 10 minutes. During regular operation of the acoustic horn, no major deposits formed on the internal blinds. During a visual inspection during boiler shutdown, there was a continuous layer of ash with a thickness of max. 10 mm.
5. The proposed system was commissioned in 2009 year on one technology. Subsequently, we mounted this tested system on two other technologies.