US4556019A — Convection section ash monitoring

Claim 1

Independent Claim 168 words

A method of controlling the build up of ash on the heat exchange surfaces of a convection section of a steam generator wherein a flowing hot gas stream contacts the heat exchange surfaces to heat steam flowing within the surfaces and said heat exchange surfaces in said convection section comprises a series of banks of heat exchange tubes, which comprises: directly measuring the temperature of the gas stream at two locations in the flowing gas stream spaced-apart in the direction of flow using radiation pyrometers positioned one on each longitudinal side of each tube bank as determined by the direction of flow to determine the temperature difference between each side of each bank as a measure of the build-up of ash on each of said tube banks, calculating the difference in temperature between said two locations as a measure of the build-up of ash on each said tube band, and activating selective cleaning of said tube banks in response to a predetermined level of build-up of ash thereon.

Claim 2

Independent Claim 168 words

A method of controlling the build up of ash on the heat exchange surfaces of a convection section of a steam generator wherein a flowing hot gas stream contacts the heat exchange surfaces to heat steam flowing within the surfaces and said heat exchange surfaces in said convection section comprises a series of banks of heat exchange tubes, which comprises: directly measuring the temperature of the gas stream at two locations in the flowing gas stream spaced-apart in the direction of flow using radiation pyrometers positioned one on each longitudinal side of each tube bank as determined by the direction of flow to determine the temperature difference between each side of each bank as a measure of the build-up of ash on each of said tube banks, calculating the difference in temperature between said two locations as a measure of the build-up of ash on each said tube band, and activating selective cleaning of said tube banks in response to a predetermined level of build-up of ash thereon.

Claim 3

Dependent Claim 25 words

The method of claim 1 wherein said build up of ash is calculated as a fouling factor (R F ) from said calculated temperature difference.

Claim 4

Dependent Claim 37 words

The method of claim 2 wherein said fouling factor is displayed on a monitor screen for use by a steam generator operator in controlling the steam generating process and/or to effect cleaning of fouled heat exchange surfaces.

Claim 5

Dependent Claim 19 words

The method of claim 3 wherein said display is a representation of the convection section illustrating regions of fouling.

Claim 6

Dependent Claim 21 words

The method of claim 2 wherein said fouling factor is used to activate said cleaning of fouled heat exchange surfaces automatically.

Claim 7

Dependent Claim 34 words

The method of claim 5 wherein said automatic actuation is overridden by signals indicative of a fouling condition which does not necessitate cleaning of the whole of said selected number of heat exchange surfaces.

Claim 8

Dependent Claim 62 words

The method of claim 6 further including measuring the heat flux received from the flowing hot gas stream at selected locations transverse to the flow path to monitor differences in the degree of fouling of the heat exchange surfaces, and selectively activating cleaning of selected portions of the heat exchange tubes in a bank in response to the measured heat flux values.

Claim 9

Dependent Claim 35 words

The method of claim 7 wherein at least four heat flux meters are provided in a plane extending transverse to the gas flow path at the periphery of a pipe confining the gas flow path.

Claim 10

Dependent Claim 74 words

The method of claim 1 further including measuring the heat flux received from the flowing hot gas stream at selected locations transverse to the flow path to monitor differences in the degree of fouling of the heat exchange surfaces, and using the measured heat flux values to override signals indicative of a fouling condition in a particular bank of heat exchange tubes determined by said difference in temperature measurements determined by said radiation pyrometers.

Claim 11

Independent Claim 161 words

A method of controlling the build up of ash on heat exchange surfaces of a convection section of a stream generator wherein a flowing hot gas stream contacts the heat exchange surfaces to heat steam flowing within said surfaces, which comprises: continuously directly measuring the temperature of the gas stream at two locations in the flowing gas stream spaced-apart in the direction of flow and between which is located a selected number of said heat exchange surfaces, adjusting said measured temperature to compensate for the emissivity of the flowing gas stream, continuously measuring the steam flow rate through said selected number of heat exchange surfaces and the temperature change in said steam across said heat exchange surfaces, determining a fouling factor (R F ) from said measurements as a measure of the build up of ash on said selected number of heat exchange surfaces, and automatically actuating cleaning of fouled heat exchange surfaces when said fouling factor attains a predetermined value.

Claim 12

Independent Claim 161 words

A method of controlling the build up of ash on heat exchange surfaces of a convection section of a stream generator wherein a flowing hot gas stream contacts the heat exchange surfaces to heat steam flowing within said surfaces, which comprises: continuously directly measuring the temperature of the gas stream at two locations in the flowing gas stream spaced-apart in the direction of flow and between which is located a selected number of said heat exchange surfaces, adjusting said measured temperature to compensate for the emissivity of the flowing gas stream, continuously measuring the steam flow rate through said selected number of heat exchange surfaces and the temperature change in said steam across said heat exchange surfaces, determining a fouling factor (R F ) from said measurements as a measure of the build up of ash on said selected number of heat exchange surfaces, and automatically actuating cleaning of fouled heat exchange surfaces when said fouling factor attains a predetermined value.

Claim 13

Dependent Claim 15 words

The method of claim 10 wherein said direct temperature measurements are effected using radiation pyrometers.

Claim 14

Dependent Claim 47 words

The method of claim 11 wherein the radiation pyrometers are each sensitive in the wavelength range in which carbon dioxide and water absorb and emit radiation and the direct determinations effected by the radiation pyrometers are corrected for the emissive and absorptive properties of the gas stream.

Claim 15

Dependent Claim 49 words

The method of claim 11 wherein the radiation pyrometers are each sensitive in the wavelength range in which carbon dioxide and water do not absorb and/or emit radiation and the direct determinations effected by the radiation pyrometers are corrected for the emissive and absorptive properties of the gas stream.

Claim 16

Dependent Claim 17 words

The method of claim 10 wherein said direct temperature measurements are effected using clean heat flux meters.

Claim 17

Dependent Claim 14 words

The method of claim 10 wherein said direct temperature measurements are effected using thermocouples.

Claim 18

Dependent Claim 158 words

The method of claim 10 wherein said fouling factor (R F ) is determined automatically from said measured values by substitution in the equation: ##EQU2## wherein (h c ) f is the convective heat transfer coefficient on the gas stream side of said heat exchange surfaces, (h c ) s is the convective heat transfer coefficient on the steam side of said heat exchange surfaces, L and k respectively are the thickness and thermal conductivity of said heat exchange surfaces, and U is a heat transfer coefficient which is determined from the equation: ##EQU3## wherein Q is the heat absorbed by the steam and determined from the measurements of temperature and flow rate on the steam side of the heat exchange surfaces, ΔT lm is the log mean temperature drop across said selected number of heat-exchange surfaces as determined from said gas stream temperature measurements and steam temperature measurements, and A is the area of the heat-exchange surfaces.

Claim 19

Dependent Claim 71 words

The method of claim 16 including determining the heat flux reaching a plurality of peripheral locations of said heat-exchange surfaces, comparing the individual heat flux determinations to the average of the heat flux determinations, overriding the automatic cleaning actuation in response to a predetermined difference in the compared heat flux determinations, and actuating selective cleaning of portions only of the heat-exchange surfaces in response to detected channelling of said gas stream.

Claim 20

Dependent Claim 17 words

The method of claim 17 wherein said heat flux determinations are effected using a heat flux meter.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1988-12-02	1989-06-03	1989-12-03	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1992-12-02	1993-06-03	1993-12-03	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1996-12-02	1997-06-03	1997-12-03	$7700.00	Window Closed / Lapsed

Convection section ash monitoring

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