Problem

A Power Boiler ESP with capacity of 54 MW in a petrochemical plant in Thailand had been undergone periodical maintenance, however, its performance had been inevitably deteriorated since it had been operating for 27 years. The ESP operation was unable to run at its full rating of T/R set. The emission during operation was 288 mg/Nm³ based on its emission designation of 300 mg/Nm³. The end users expected to bring back ESP performance and improve collecting efficiency even beyond its capacity.

Table 1: Emission rate among ESP design, operation and target

Solution

Tai & Chyun has been awarded for this ESP retrofit project. We provided all-in-one service from design, manufacture, installation as well as commissioning. The project included dismantlement of the entire internal parts inside the ESP and reinstallation of new parts with a 45-day on-site installation and supervision service. Major ESP parts such as Collecting Electrode (CE), Discharge Electrode (DE), and Transformer Rectifier (T/R) Set, including Access Door were retrofitted into new designs as shown in Table 2.

Table 2: Comparison between old and new design

The width of CE has been reduced with increased number of CEs per row against its original design. This change has no effect on the Specific Collecting Area (SCA), but it benefits the ease of maintenance due to less reduction area when bent or deteriorated CE is required to be cut off. Old DE has been replaced with new Rigid Discharge Electrode (RDE) that resulted in reduced number of DEs after retrofit to 80% while corona generation is even more efficient than the original design, which increases ESP performance and also benefits future maintenance respectively.

Along with major parts, other related mechanical parts such as rapping system, Gas Distribution (GD) screen, inlet/outlet expansion joint, etc. have also been renewed. Single Access Door has been upgraded to Double Access Door in order to eliminate the possibility of air leakage through the door and avoid moisture from building up inside the ESP.

Dismantling the entire internal parts

Installing new CE

Installed DE/CE rapping system

Newly installed RDE

Installing Double Access Door

Installing inlet/outlet expansion joint

In electrical aspect, 2 sets of High Frequency Transformer Rectifier (HFTR) have been replaced in the 1^st and 2^nd field while another new conventional T/R set has been installed in the 3^rd field. HFTR produces higher average voltage than conventional T/R, generating higher migration velocity that leads to higher ESP collecting efficiency.

Furthermore, a new control panel with Graphic Display Unit (GDU) keypad has been installed. An interlock key system provides Lock Out Tag Out (LOTO) procedure for safety concern during operation and maintenance.

High Frequency Transfomer Rectifier Upgrade

Control Panel Installation

Newly installed GDU keypad