Electrostatic Precipitators for CHP Plants and Boiler Houses: Removing Ash from Flue Gas
Coal-fired CHP plants and boiler houses are among the most demanding applications for an ESP: large gas volumes, high ash content, and strict emission limits.
Why CHP plants and boiler houses cannot do without an ESP
Burning coal in a boiler furnace produces ash — 5-40% of fuel mass depending on coal grade and ash content. Without cleaning, this ash is released to atmosphere with the flue gas through the stack, which fails current environmental limits and exposes the plant to fines and a shutdown order from regulators.
An ESP remains the standard way to clean flue gas at CHP plants and large boiler houses precisely because at high gas volumes (hundreds of thousands of m³/h) it offers low pressure drop and up to 99.9% collection efficiency — bag filters are less cost-effective at these gas volumes given filter media life at high temperature.
What makes coal ash a demanding material to collect
The key parameter for ESP sizing is ash resistivity. Ash from Ekibastuz and other Kazakhstan coals often has elevated resistivity due to low sulfur content — this reduces collection efficiency and calls for more fields, gas conditioning, or higher-capacity power supplies compared to ash from more "cooperative" coals.
Ash abrasiveness also matters: it accelerates wear on gas distribution screens, the casing at flow-turn sections, and ash removal screws, so the high-wear zones are built with extra plate thickness or wear liners.
How an ESP is sized for a specific boiler
Sizing starts from the specific boiler's flue gas parameters: volumetric flow (m³/h), inlet temperature, moisture content, and the grade and ash content of the fuel being burned — these drive both ash resistivity and the required gas velocity in the active zone. Next, the required collection efficiency is set based on emission limits for the specific region and site.
From this data, the number of series fields, collecting electrode area, and power supply capacity are selected — a generic "for an N MW boiler" solution without this input data is only a rough estimate; an accurate design requires the actual parameters of the specific boiler.
Retrofitting an ESP into an operating CHP plant
On an operating site, an ESP is almost always tied into the existing gas duct between the boiler and the stack or induced-draft fan — this imposes footprint, height, and duct-connection constraints that do not exist when designing from scratch. The tie-in is scheduled to minimize boiler downtime, usually within a planned maintenance outage.
Economics: fines versus investment in gas cleaning
Excess-emission fees and environmental fines for operating without effective cleaning, or with a worn-out ESP, accumulate year after year, whereas an ESP is a one-time capital investment followed by operating costs for power and maintenance. For sites with continuous boiler operation, payback is usually driven by reduced environmental fees and eliminating the risk of a regulator-ordered shutdown.
Need an ESP sized for your boiler?
UK-ZTO-AN has designed and manufactured electrostatic precipitators for CHP plants and boiler houses since 2005 — send us your boiler parameters and fuel grade, and we will size a configuration for the required collection efficiency.