Plant draft system and flow improvement across pollution control equipment are areas where performance expectations are much higher than they were 10 years ago, in part due to stricter industry standards and stronger competitive forces that is prompting companies to examine how they can enhance cost effectiveness while operating at peak efficiencies. However companies are unable to do much and constrained for the following reasons:
• Balance draft problems
• Non-uniform flow distribution in wind boxes
• Improper loading of fans resulting in flow induced vibrations, turbulence and under performance of fans (for e.g. FD/ID/PA Fans in Power industry; Primary/ Final Cooling Fan, Windbox Recup Fan, and Updraft/Downdraft Fan in Ferrous industry; Mine Ventilation Fan in Mining industry)
• Non-uniform flow distribution across — Air Heaters, External Economizer, Annulus Cooler, and Updraft & Downdraft Drying Zones
• Poor performance of Environmental equipment like ESP, Bag House, SCR, and FGD due to improper flow distribution through conventional perforated distribution plate/flow straighteners
• Cold air corrosion in Air Pre-Heater due to temperature stratification
The Cause for the above problems:
• Improper air & flue gas entry conditions at fan
• Poor or no conversion of unproductive velocity pressure (Kinetic Energy) to useful static pressure through gradual diffusion of air/flue gas without flow separation.
• Poor duct design and flow stratification
• High velocity hot spots across ESP causing the aerodynamic forces on particles to be much higher than electrostatic forces generated by collecting surfaces/ electrodes resulting in higher particulate emission
• Improper mixing of hot and tempering air before pulverizers
This has opened new opportunities for M&I. M&I is reinforcing technical potential and know how through extensive R&D and over two decades of experience in integrating fluid mechanics with aerodynamics.
Conventional Design Approach
• Flow characteristics not analyzed or given adequate importance
• Negative effect of turbulence, flow separation, etc not considered
• ‘Conduit’ mentality for duct design instead of fed equipment performance needs
• Initial and final ducting design based on ‘rule of thumb’
• Use of obtuse angles and sharp bends
• Incorrect use and location of silencers
• ‘Brute force’ stiffening used to reduce flow induced vibration
• Use of ‘bluff bodies’ to even out flow (e.g. for perforated plates, screen, baffles, etc.)
M&I’s approach is to study the flow characteristics of air/flue-gas by using Computational Fluid Dynamics (CFD) and mathematical modeling techniques and accordingly design the plant draft system or equipment inlet/discharge system. All equipment relies on proper flow conditions to perform efficiently and M&I’s design ensures that the fed equipment and the engineering / operational needs are met. At the same time, noise, vibration and pressure drop or draft losses are considerably reduced within the same existing constrained space limitations.
M&I employs the knowledge it has about flow behavior / characteristics, boundary layer separation and accordingly design aerodynamic diffusion system J. in the draft system ducting and inlet/discharge ducts of Fans and Environmental Equipment. Despite the prevalence of turning vanes, aerodynamic diffusion is a viable solution due to its 3-dimensional construction, because it can provide performance advantage that can help plants to meet tougher standards and efficiency demands.
M&I’s aero-acoustic diffusion systems ensure that flow problems like turbulence, flow separation, etc are minimized. This ensures streamlining of flow entering downstream equipment.
The diffusion system not only streamlines the flow but also absorbs noise. Hence eliminates conventional splitter silencer designed to consume extra pressure drop. M&I has over 30 patents, which covers various draft plant equipment and other energy saving solutions.
• 10-25% reduction in power consumed by fans
• Improved plant performance through flow control and draft plant system optimization.
• Lower emission from same environmental equipment using conventional flow distribution techniques at much lower pressure drop.
• Improved performance of various equipment due to uniform flow
• Lower foot print enabling easy retrofitting of M&I modification in existing plant
Application of M&I’s technology
M&I’s technology for streamlining flow and reducing pressure drop finds application in the following equipment/system:
1. ID, FD and PA Fans
2. Collector Fan, Windbox Recup Fan and Mine Ventilation Fan
3. ESP, FGD, SCR and Bag House
4. Plant Draft System
Manufacturing units consuming large amounts of energy need to be efficient, economical and silent. The critical element to our vision is the ability to work closely with our customers, understand their needs and respond appropriately. M&I’s technology provides superior engineering value i.e. by providing our customers with long-term advantage. We understand complexity of fan capacity constraints and are fully aware that decision you make today will affect your operations for years to come. That is why with M&I’s Aero-acoustic technology we can address most of the plant draft system problems, including fan capacity constraints accomplished through converting unproductive velocity pressure of the fan into static pressure regain. Similarly, by ensuring that flow into environmental equipment, like ESP, has to be less than 10-12% RMS deviation over mean velocity (as against 25-30% in conventional design), the performance of equipment is significantly enhanced and environmental pollution is reduced.