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Hybridization of Urea-SNCR with SCR - A Fit for the Future

AIR POLLUTION CONTROL Flow Modeling


FLOW MODELING - EXPERIMENTAL

We specialize in experimental (physical) modeling of air pollution control equipment. Scale models of 1:4 to 1:18 have been built for testing at our North Carolina flow lab for installations in Europe, North America and Asia. Our focus continues to be the delivery of the most accurate and innovative solutions for our customers.

Innovative techniques are used in scale flow modeling to improve performance in flow critical equipment. Our flow models are constructed quickly and accurately using CNC cut steel as a skeleton, while clear plastic is tested using the latest in flow analysis equipment.

Our experimental model studies combined with Computational Fluid Dynamics (CFD) modeling allow for insightful understanding of existing flow situations and effective design of corrective devices such as turning vanes, ash screens, injection systems and static mixers for each unique project. Typical optimization projects reduce system pressure losses, improve temperature, velocity, gas species and ash distributions and prevent in-duct ash and dust fallout, all of which translate to customer savings.

The combination of unique construction techniques, state-of-the-art technology and years of experience enables model studies to be performed in half the time required by our competitors, thereby providing our customers with the confidence and guarantees needed to proceed with construction or retrofitting.

Electrostatic Precipitators

Electrostatic precipitators (ESP) rely on electrostatic attraction to collect particles from a flow stream. As such, they are quite versatile and can be operated with up to 99% efficiency in a wide variety of operating conditions. However, to achieve such high efficiency several ESP variables must be considered. Specifically, temperature, flow and dust distributions must be uniform to each of the compartments formed by the precipitator plates and dust fallout in the ductwork and re-entrainment from the hoppers must also be taken into consideration.

By combining computational and experimental modeling to predict fluid behavior in new and existing ESP installations, such flow problems can be found, analyzed and prevented. Corrective flow devices can then be designed, tested and optimized to ensure that flow characteristics meet industry standards such as those set by the Institute of Clean Air Companies (ICAC) Technical standard EP-7.

Selective Catalytic Reactors

Selective catalytic reactors use ceramic catalyst to react NO2 and NO3 with ammonia to produce harmless N2 and H2O. NOx emissions have been identified as the main source of smog, ground level ozone and acid rain. The reduction of NOx emissions is beneficial to the environment as well as to general public health.

Selective catalytic reactors are modeled to ensure that the catalyst is effective and catalyst life is extended for as long as possible. Proper mixing of flue gas and good flow and velocity profile are required to prevent ammonia slip (unreacted ammonia in flue gas) and ensure that NOx emissions are minimized. Fuel Tech engineers are highly experienced in the operation of SCRs and the design of ammonia injection systems and work closely with leading catalyst manufacturers to achieve the best possible flow solution.

Fabric Filter

Fabric filter baghouses remove particulate from an air stream through physical exclusion. Even distribution of flow to baghouse compartments and good flow profiles at the bottom of the bags are important to ensure even efficient removal of dust and the prevention pf premature wear of the filter fabric.

The design of flow optimization devices requires consideration of dust fallout, dust distribution to baghouse compartments, hopper re-entrainment and protection of the fabric filters. Modeling of baghouses can be used to predict and solve problem areas of wear and particulate fallout in baghouse systems while reducing overall pressure losses. Fuel Tech designs corrective flow devices to conform to industry baghouse performance standards such as those set by the Institute of Clean Air Companies (ICAC) Technical Standard F-7 to ensure optimum baghouse performance.

Flue Gas Desulphurization

Flue gas desulphurization (FGD) wet scrubber systems and dry absorber systems remove SO2 from flue gas by reaction of the acidic SO2 gas with an alkaline reactant to produce an easily collectable by-product. Essential to the efficient operation of an FGD is good mixing of the flue gas stream with the scrubber reactant as well as residence time within the reactor.

Nozzle placement, flow optimization devices and mixers are some of the tools used to correct inefficient flow situations in an FGD system. Using CFD and experimental modeling, poor FGD performance can be prevented, and even improved, while solving other problems associated with wet scrubber systems such as:

  • Inlet duct liquid pullback
  • Mist eliminator performance
  • Excessive pressure losses
  • Fan inlet flow distribution
  • Spray coverage
  • Liquid collection

Air Pollution Control Overview