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Combustion Products Incorporated (CPI) supplies adjustable coal distribution devices for the precise control of mass and velocity. The primary use is in balancing fuel delivery to individual burners of coal-fired power plants.
 Controling flow from coal pulverizers to the burners is critical to obtaining optimized combustion. In todays’ Power Market where both efficiency and reduced emissions are vitally important, the ability to control the coal delivery for combustion is essential to achieving both.
CPI’s engineered approach to coal control has led to a variety of solutions for coal balancing. The NT Series (Patent Pending) coal valve was developed as a result of the need to balance coal pipes while also maintaining/creating a more homogenous coal distribution in the coal/air stream of the coal pipe. This again, is essential for optimizing combustion. The use of the NT valve will allow for reduced NOx, unburned carbon, CO as well as improved boiler performance. It can also lead to decreased slagging and boiler tube wastage.
Because the coal in a coal pipe is prone to roping (flowing in very small, contrated areas within the coal conduit), any means of adjusting or restriction in the pipe needs to take this into consideration and act to break up a rope or otherwise more evenly distribute the coal across the pipe cross-section.
While most restricting type variable orifice coal control devices move coal into more concentrated coal regions (coal ropes), The NT Series Coal Valve uses a (patent pending) perforated blade design. The more the pipe is restricted with the NT Coal Valve, the more redistribution of the coal is performed for better combustion.
The NT Series Coal Valve is easy to install in any pipe size without removing a section of pipe - though a flanged "spoolpiece" is available as an option. Proven to regulate coal when installed properly (at the mill outlet), the NT Series Coal Valve does not cause roping nor the excessive pipe wear associated with other coal adjusting devices.
Extended service was in mind when the NT Series Coal Valve was designed - with a hardened steel (AR500 equivalent) blade.
The NT Series Coal Valves can be used not just to control the coal mass to the burners but also to control the coal velocity to the burners. Improper coal velocity can lead to coal layout, pipe fires or burner tip fouling (too low of a velocity) as well as to high LOI, CO and tube temperatures (associated with high coal velocity). When the NT Series Coal Valve is used to control velocity it has the same positive effects on combustion because it more evenly distributes the coal within the coal conduit.
This data shows the NT Series coal valves’ changes to the coal distribution at a Power Plant. The improvements to the coal distribution on this and the other mills led to the reduction in LOI by 4% combined with a dramatic reduction in CO.
The diffusing capabilities of the NT Series Valve have also been applied to exhauster mill applications with Riffle Boxes. A multi-blade solution to Riffle Box applications offers control of coal beween the pipes.
The diffusing capabilities of the NT Series Valve have the same positive results on exhauster mill applications with Riffle Boxes as they do on pressurized mill applications. This multi-blade solution to riffles offers adjustability of the coal, which is essential for good combustion. Coal Entering the riffle box can be adjusted with either of the two lower diffusing blades and/or the upper blade. The fixed riffle element is no longer needed. The end result is the overall pressure drop can be reduced. As shown here the diffusing blades are restricting coal from the left pipe to and adding coal to the right pipe.
If desired, the riffle elements can remain in place and the NT valves can be located just upstream or downstream of the riffle to allow for precise balancing.
The use of NT Series Coal Valves on exhauster mill applications (often T-Fired boilers) can lead to improvements to corner-to-corner coal flows (as shown here) and thus to improvements in steam temperature distribution, NOx, CO, LOI and more.
AR 500 Hardened Steel Diffusing Blades are used in this assembly to ensure long life and uniform distribution of coal in the pipe(s). The cover plate is removed from the riffle housing and the old riffle element is replaced with this assembly consisting of a new riffle cover plate with integral diffusing blades.
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