Give an Existing FGD Tower a Second Life: Upgrade Without Demolition

An existing limestone-based flue gas desulfurization (FGD) tower does not necessarily need to be demolished when a plant switches to ammonia desulfurization.

For industrial operators, the decision is becoming increasingly important. Demolition and reconstruction can mean significant capital expenditure, while continuing to operate an aging limestone-gypsum FGD system may bring growing pressure from by-product disposal, wastewater treatment, carbon management, and emissions compliance.

Calcium-to-ammonia conversion offers another option: retain usable infrastructure and upgrade the key process sections.

Depending on the original tower design and operating conditions, the existing foundation, tower shell, piping, and plant buildings may be suitable for reuse. Typical modifications may include raising the tower or adding a series-connected tower, installing concentration and oxidation sections, upgrading spray layers, and adding ammonia supply and ammonium sulfate recovery facilities.

Where the plant already has an ammonia supply system for selective catalytic reduction (SCR) denitrification, the new design may also allow the supply infrastructure to be integrated, subject to engineering and safety assessments.

The economic case extends beyond the initial investment. Ammonia desulfurization converts sulfur dioxide into ammonium sulfate, a potentially marketable by-product. It can also reduce the need for limestone consumption and gypsum disposal. Actual savings depend on project configuration, local disposal charges, by-product quality, ammonia prices, and operating requirements.

MingSheng Environmental Protection provides calcium-to-ammonia conversion solutions designed to make use of suitable existing assets while upgrading the treatment process. The company states that typical retrofit projects can be completed within 90–120 days, although the schedule depends on site conditions and the scope of work.

For plants evaluating an FGD system upgrade, the first step is not necessarily to plan demolition. A technical assessment of the existing tower can help determine which structures and equipment can be retained, what needs to be modified, and whether conversion is economically viable.

A successful retrofit is not about preserving an old tower at any cost. It is about giving usable infrastructure a new role in a more integrated flue gas treatment system.