Flue Gas Desulfurization System Expansion Design Optimized with AFT Arrow
AFT Arrow™ Case Study
Energoprojekt Katowice | Flue Gas System| Power Generation
“Using AFT Arrow I could check all parameters and find
the optimal dimensions of conduits in order to deliver
the required flow through the FGD plants.”
-Adam Klepacki, Energopojekt Engineer
PROBLEM
- Environmental regulations required power plant to expand their flue gas desulfurization system
- Needed to ensure controlled pressure at furnace exit
ANALYSIS
- AFT Arrow with the Goal Seek & Control module was used to find the optimum fan conditions
- Engineers were able to creatively model unique aspects of their design
SOLUTION
- Found the fans should provide ~3000 Pa (0.45 psi) to ensure the proper furnace exit pressure, while maintaining expansion demand to meet regulations
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Problem Explained
Energoprojekt Katowice was charged with designing the expansion of the flue gas desulfurization system at a coal fired power plant in Poland.
Originally having a capacity equivalent to four of the eight power units at the plant, increasing environmental regulations required a capacity expansion to now handle all eight power units. The system presented several unique challenges to accurately model its characteristics, all ingeniously addressed by Energopojekt’s engineer, Adam Klepacki:
- The natural draft effect in the discharge stacks provides a noticeable and useful benefit in assisting system flow that varies as a function of the gas flow rate and temperature. Using fans modeled with curves, the draft effect as a function of flow was accurately simulated. By modeling the fans using Multiple Configurations, curves for the flue gas temperature extremes were represented in a single ‘fan’ making it easy to change operating scenarios by simply selecting the curve corresponding to the ‘hot’ or ‘cold’ flue gas.
- The FGD plants have the combined effect of increasing the gas stream temperature and adding mass and volume to the flow by virtue of the internal water spray. Using a heat exchanger with a controlled downstream temperature in conjunction with spray discharge junction this combined effect on the flue gas flow stream was simulated.
Challenges addressed Cont.
- Induced draft (ID) fan speed control to maintain a controlled furnace exit pressure was simulated using the Arrow GSC Module. With the multitude of ID fans and furnaces, this represented an 8 variable/8 goal automated goal seeking operation saving significant time compared to manual iteration.
- Flue gas conduits in power plants typically have very large cross sections so that the velocity profile is highly irregular, with significant turbulence induced by direction changes resulting in hydraulic resistance larger than the resistance calculated based on the mean velocity. To account for this, ducting resistance was increased using a combination of additional fittings losses and increased wall roughness.
- The unique properties of the flue gas were dynamically modeled by characterizing its properties within an AFT Arrow fluid database.
Solutions & Benefits
“It would be very difficult and time consuming to calculate such a big system using only pencil and a piece of paper or even a calculator,” said Klepacki. “To solve this task I needed specialized software which can estimate all necessary flows and pressures in every branch of the system (moreover, using GSC module I could set the demand pressure in the furnace chamber).”
Klepacki said by using AFT Arrow he could check all parameters and find the optimal dimensions of conduits in order to deliver the required flow through the FGD plants. Speaking on how easy it is to introduce changes into the model he said, “There is no problem when you have such a model because every change in design data can be easily implemented and new results are available in a few minutes. The same is true when multiple scenario analysis is needed (in our case I [needed to] calculate about 40 scenarios so it has brought me a really great benefit).”
Compressor/fan summary from one of the many operating scenarios simulated.
Detail view of the FGD plant and discharge stack
area of the system