Wet Flue Gas Desulfurization (FGD) Systems

Overview

What a wet FGD system does

Burning coal, oil or other sulfur-bearing fuel releases sulfur dioxide into the flue gas. A wet scrubber brings the gas into contact with a liquid that absorbs the SO2 and converts it to a stable by-product. Our systems use either the wet limestone-gypsum process or a seawater process, depending on what the site offers.

Limestone-gypsum route

Ground limestone is mixed with water into slurry and sprayed through the gas in an absorber tower. Sulfur dioxide reacts to form calcium sulfite, which is oxidized with blown air into gypsum. The gypsum is dewatered and can be sold or landfilled, subject to local rules. This route suits sites with limestone supply and space for slurry handling.

Seawater route

Coastal plants can use seawater, whose natural alkalinity absorbs sulfur dioxide. The used water is treated and returned to the sea in line with local discharge requirements. It avoids limestone handling, but needs suitable marine conditions and permits.

Designed from your gas, not from a catalog

Gas flow, temperature, sulfur content, dust loading, layout space and the emission limit you must meet decide the absorber size, materials and the number of spray levels. Removal efficiency and pressure drop are set by the design and written into the contract for your gas conditions, not taken from a general figure.

Subsystems and scope

The scope can include absorber, circulation pumps, oxidation air, gypsum dewatering, gas heat exchange, wastewater treatment, electrical and controls. The boundary of supply is defined at the start so nothing is left unassigned.

Delivery

Large vessels may be fabricated locally to our drawings; pumps, instruments and internals are shipped from our factory. Commissioning support is part of the project plan.

Quotation

Use the quote checklist below and our engineers will reply with a written scope, drawings or a specification, and a clear list of what is and is not included. Questions on shipping, spare parts and installation are answered in the same reply.

Typical installation and site requirements

A wet FGD plant is built around the boiler or furnace it serves, so the site survey comes before the drawings. The absorber is a tall vessel, often 15 to 35 m including the outlet, and needs a foundation sized for the full slurry load. Plan floor space beside it for the limestone silo or day tank, slurry pumps, oxidation blowers and the dewatering skid, plus a drain pit that can take washdown water.

Utilities decide running cost: process water for makeup and mist-eliminator washing, compressed air for instruments, and a power supply for pumps and fans. Gas ducting should be short, with room for expansion joints and a drain at the lowest point. Material choices follow chloride level and temperature, so send a flue-gas analysis early. Also decide where gypsum goes: sale, landfill or a stockpile, because that sets the dewatering and conveying design. We review all of this against your drawings before quoting a layout.