Borosilicate Glass Block Linings at Work in Wet FGD Chimneys

Borosilicate Glass Block Linings at Work in Wet FGD Chimneys
Expanding demand for flue gas desulfurization (FGD) systems in both new and retrofit applications for coal-fired power plants has required the use of suitable and cost-effective materials for flue gas ductwork and chimneys.

 In the past, metallic and glass reinforced plastic solutions have often been the first consideration. More recently, a composite system based on a flexible, acid resistant adhesive and borosilicate glass block technology has enjoyed attention, based on its combination of technical properties. In addition to favorable economics and fire resistance, this system’s installation method may make it especially suitable for both new construction on steel as well as refurbishment applications, including application onto existing brick flues, steel flues or directly to a concrete windshield.                                                                             

 Engineers have developed a new chimney to maximize the benefit of this composite technology. The design incorporates the borosilicate glass block lining system directly bonded to the concrete windshield, eliminating the need for a traditional internal independent flue. The design offers the chimney builder and utility owner a potentially cost-effective solution, as well as favorable scheduling advantages.

 Borosilicate glass block linings were originally used in the early 1980s when FGD technology was first being added to coal-fired power plants. At that time, most chimney liners were constructed of chemical resistant brick. The primary corrosion protection concerns were horizontal duct sections from the scrubber, as well as bypass ductwork.

 Chimney designers evaluated a number of lining types with varying degrees of success. One system used in these early tests was a borosilicate glass block lining, employing a combination of a flexible adhesive/membrane layer and a thick (typically 1.5 inch to 2 inch) lightweight closed cell acid proof borosilicate block, to provide full chemical and thermal protection.

 Full height chimney linings using this system were first performed in the mid 1980s—typically to address corrosion problems with existing structures. Over time, the performance of the borosilicate glass block lining system showed it to be a long-term solution. From these early applications, this technology evolved to large scale use today.

 Borosilicate glass block lining systems can be used in three applications: construction of new concrete chimneys with steel flues, retrofit modification of chimneys with brick flues and construction of new concrete chimneys without internal flues (new chimney design).

 The borosilicate block system is economically favorable as an internal lining for steel chimney flues. The system provides outstanding corrosion protection and it eliminates the need for external insulation. It is suitable for a wide range of operating conditions—wet gas service, reheat and FGD bypass. It also offers several specific technical advantages including minimizing condensate formation, fire resistance and earthquake zone suitability.


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