FLUE GAS VELOCITY AND RISK OF SPITTING
Avoiding flue gas reheat and running an FGD Wet Stack offers great savings in both the construction cost and the operating cost of a coal fired power station. One serious complication of FGD Wet Stack operation is the risk of "spitting", the spreading of acidic droplets in the environment surrounding the power station.
In order to minimize the risk of spitting, the flue gas velocity in an FGD Wet Stack must be limited and it is different for every material of construction.
Hadek's lining system has been thoroughly tested for its Wet Stack properties and, in its normal configuration with the borosilicate glass blocks placed upright, it will not allow liquid to break free from its surface at gas velocities up to 19.8 m/s. Using a 1.5 m/s safety margin, it is normally recommended that borosilicate glass block lined chimneys should be restricted to a flue gas velocity of 18.3 m/s.
SOLUTION FOR FLUE GAS VELOCITIES ABOVE 18.3 M/S: HADEK™ LINING INSTALLED IN 45 DEGREE HIGH VELOCITY PATTERN
Unfortunately, 18.3 m/s is sometimes not enough. Some owners want to re-use an existing chimney, where flue gas velocity will be greater than 18.3 m/s. Other owners want to build a new chimney that respects the 18.3 m/s limit during normal operation, but they cannot rule out higher velocities in some operating cases. Finally, some FGD outlet ducts have "strange" geometries that result in a very uneven gas distribution in the chimney entry zone.
To address this problem, Hadek has once again worked with Alden Research Laboratory and developed the "45 Degree High Velocity Pattern". Put simply, this is a lining where the Hadek Blocks are placed under a 45 degree angle, avoiding the use of any horizontal joints.
The effect of using the 45 Degree High Velocity Pattern is significant. When placed in this configuration, the lining will hold on to liquids on its surface at gas velocities up to 22.9 m/s.
The 45 Degree High Velocity Pattern (patent pending) does not create additional cost in the chimney construction process, other than a slight increase in installation man-hours.
ADVANTAGES OF THE 45 DEGREE HIGH VELOCITY PATTERN
Applying the HadekTM Block Lining System in the 45 Degree High Velocity Pattern will minimize the risk of harmful stack liquid discharge ("spitting").
For additional cost saving and emissions reduction, power plant owners should consider our other innovative ideas: