Control method for the operation of a combustion boiler
AssigneeImprobed AB
InventorsBengt-Ake Andersson, Fredrik Lind, Henrik Thunman
Life of this patent
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Abstract
The invention is in the field of boiler control and relates to a control method for the operation of a combustion boiler, comprising providing a predetermined upper limit (VF,max) for the flue gas velocity in at least one location of the boiler; monitoring the flue gas velocity (VF) during the combustion of fuel in said at least one location of the boiler; comparing the flue gas velocity (VF) with the predetermined upper limit (VF,max); decreasing the thermal load of the boiler if the flue gas velocity exceeds the predetermined upper limit (VF,max). The invention also relates to a control system configured to execute the control method.
Claims12
A control method for the operation of a combustion boiler, comprising:
- a) providing a predetermined upper limit (VF,max) for the flue gas velocity in at least one location of the boiler;
- b) monitoring the flue gas velocity (VF) during the combustion of fuel in said at least one location of the boiler, wherein monitoring the flue gas velocity (VF) comprises monitoring a flue gas temperature in the at least one location of the boiler;
- c) comparing the flue gas velocity (VF) with the predetermined upper limit (VF,max);
- d) decreasing the thermal load of the boiler if the flue gas velocity exceeds the predetermined upper limit (VF,max),
- wherein the boiler is a fluidized bed boiler having bed material that comprises ilmenite particles;
- and wherein at least a portion of the bed material is carried away with a primary gas stream and subsequently separated from the primary gas stream by a cyclone;
- wherein flue gas velocity (VF) is determined according to the following formula:
- VF=C/A;
- where:
- C=the volume flow of flue gas;
- A=the cross-sectional area of the flue gas duct;
- and
- wherein the boiler is a circulating fluidized bed (CFB) boiler and the flue gas velocity is determined for the region adjacent and downstream the cyclone and the volume flow of flue gas is determined according to the following formula:
- V
- *
- C
- =
- (
- V
- *
- Total
- ,
- stack
- +
- V
- *
- FGR
- -
- V
- *
- Air
- ,
- FGT
- -
- V
- *
- Water
-
-
- vapour
- ,
- FGT
- )
- ·
- T
- c
- 273
- ·
- 1
- P
- c
-
- (
- m
- 3
- s
- )
-
- where
-
- :
-
- V
- *
- Total
- ,
- stack
- =
- total
-
-
- gas
-
-
- flow
-
-
- in
-
-
- the
-
-
- stack
- (
- m
- n
- 3
- s
- )
-
- V
- *
- FGR
- =
- flow
-
-
- of
-
-
- recirculated
-
-
- flue
-
-
- gas
- (
- m
- n
- 3
- s
- )
-
- V
- *
- Air
- ,
- FGT
- =
- air
-
-
- flow
-
-
- added
-
-
- to
-
-
- the
-
-
- flue
-
-
- gas
-
-
- treatment
-
-
- plant
- (
- m
- n
- 3
- s
- )
- V
- *
- Water
-
-
- vapour
- ,
- FGT
- =
- flow
-
-
- of
-
-
- water
-
-
- vapour
-
-
- from
-
-
- the
-
-
- water
-
-
- added
-
-
- to
-
-
- the
-
-
- flue
-
-
- gas
-
-
- treatment
-
-
- plant
- (
- m
- n
- 3
- s
- )
- Tc=temperature just downstream the cyclone (° C.)
- Pc=pressure just downstream the cyclone (Pa)
- wherein the flow of water vapour in the flue gas treatment plant is determined as the mass flow of water added divided by the density of the water vapour.
Dependencies are inferred from the claim text.