| US 7,484,955 B2 | ||
| Method for controlling air distribution in a cyclone furnace | ||
| Thomas J. Flynn, North Canton, Ohio (US); Ralph T. Bailey, Uniontown, Ohio (US); Timothy A. Fuller, North Canton, Ohio (US); Charles E. A. Finney, Knoxville, Tenn. (US); and C. Stuart Daw, Knoxville, Tenn. (US) | ||
| Assigned to Electric Power Research Institute, Inc., Charlotte, N.C. (US) | ||
| Filed on Oct. 04, 2006, as Appl. No. 11/538,578. | ||
| Claims priority of provisional application 60/823568, filed on Aug. 25, 2006. | ||
| Prior Publication US 2008/0050684 A1, Feb. 28, 2008 | ||
| Int. Cl. F23M 3/00 (2006.01) | ||
| U.S. Cl. 431—9 [431/8; 431/10; 431/75; 431/116; 431/281; 110/348; 110/213; 110/203; 700/274; 700/299; 700/300; 126/19.5; 137/15 E; 137/15 R] | 13 Claims |
| 1. A method of adjusting air flow distribution in a cyclone furnace of the type having a plurality of cyclones, each cyclone
having a barrel, an attached burner, primary, secondary and tertiary air flow dampers for controlling air flow to the barrel
and burner, over-fire air flow dampers, a lighter scanner and a main flame scanner in order to minimize NOx while maintaining
acceptable carbon monoxide emissions, unburned carbon loss, and reliable cyclone operation, the method comprising the steps
of:
(a) setting secondary air flow on each cyclone to a typical secondary air flow damper setting to provide equal secondary air
flow to each cyclone;
(b) setting all over-fire air flow dampers to a same air flow value;
(c) closing the tertiary air flow damper;
(d) adjusting the primary air flow dampers to 90-95% of a target sum of primary air flow and tertiary air flow as indicated
by one or more flow measurement devices or the position of the primary air flow damper;
(e) adjusting the tertiary air flow damper until a minimum tertiary air flow at which a balance of primary and tertiary air
flow as indicated by flow measurement devices or the position of the primary and tertiary air flow dampers is achieved;
(f) assessing cyclone performance by analyzing the flame scanner signals from the main flame scanner and lighter scanner and
generating statistics indicative of whether operational characteristics of one or more cyclones is inside or outside of predetermined
variance limits;
(g) increasing primary air flow or secondary air flow as appropriate to eliminate instability indicated by some or all of
statistics being outside of ± variance limits;
(h) in the case of all cyclones indicating stable operation by reference to both main flame and scanner lighter signals, decreasing
primary air flow on each cyclone until a minimum primary air flow is reached at which the main flame scanner signal begins
to exhibit flame instability as indicated by statistics drifting toward variance limits, while maintaining tertiary air flow
at minimum flow;
(i) upon adjustment of the primary air flow to a minimum value needed to achieve stable operation, decreasing secondary air
flow by closing the secondary air damper on each cyclone stepwise and simultaneously until a minimum secondary air flow is
reached at which the lighter scanners begin to detect instability;
(j) simultaneously increasing air flow to all overfire air ports equally to maintain excess air flow while decreasing secondary
air flow to the cyclones to a value corresponding to a minimum secondary air flow and maximum degree of staging for each cyclone;
and
(k) adjusting the overfire air port dampers as needed to compensate for any O2 or CO imbalances resulting from the adjustments made to the cyclones.
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