DD289114A5 - METHOD AND DEVICE FOR DETERMINING THE SLACKING TEMPERATURE AND THE SLACKING THICKNESS THICKNESS - Google Patents

Abstract

The invention relates to a method and a device for determining the slag preparation temperature and the thickness of the pipe system of a combustion chamber or heat plant, being measured as the combustion chamber temperature of an uncooled head of a provided with a cooled pipe part probe tube. In this case, the temperature T ind wi on the inner wall and the temperature T ind wa on the outer wall of the cooled pipe part when setting a sufficiently large temperature difference T ind wa - T ind wi measured, the heat flux density q (r ind A) after the known per se Relationship q (r ind A) = f (T ind wi; (formula)) and the slag batch temperature T ind A according to the known relationship T ind A = f (formula) and / or the slag batch thickness according to the known per se relationship ( Formula), where the symbols A - area q - heat flux density s - thickness T - temperature delta _ tube wall thickness epsilon - degree of blackness sigma o - radiation constant of the absolutely black body X - thermal conductivity indices A - approach a - outside i - inside BK - combustion chamber n - medium Fl - flame W - wall Fig. 1 {combustion chamber; piping system; slagging; determination; batch temperature and thickness; measurement; temperature: internal and external wall; mathematical relationships}

Description

Field of application of the invention

The invention relates to a method and a device for determining the slag preparation temperature and the slag approach thickness on the pipe system in a combustion chamber or a thermal plant.

Characteristic of the known state of the art

To determine the layer thickness of flue gas approaches on solid surfaces solutions are known by

- special measuring arrangements record the local conditions,

- Evaluation of process parameters give information about mean thickness of the application.

In a locally detecting measuring device two temperature sensors are arranged, one on the surface of a heat exchanger, the other at an adjustable distance thereof, which emit a pulse when the temperature difference exceeds a certain level (DE-AS 1526136)

 The disadvantage is that

- only a certain boundary layer thickness at the temperature sensor, no intermediate layer and no increase is displayed and

- The temperature sensor is very susceptible to interference due to the use in the highest temperature range.

Another measuring device has an electrode pair, which detects the increasing corona current at Bdlastungswiderstand an electrical circuit with increasing layer thickness (DD-PS 265962). Here complex electrical systems with high voltages are to be installed. Again, only one limit is displayed, the electrode is exposed to high temperatures.

These solutions also capture only previously set thresholds.

Also known is a device which mechanically outputs a signal when reaching a certain layer thickness with levers, joints and tie rods (DD-PS 232 749).

Here is a pipe system (only uncooled) usable because it is weighed as a segment. However, this uncooled system shows different slagging behavior than a cooled tube wall. A weighing cooled subsystem can not be produced. As an additional disadvantage here is the vibration and susceptibility to see.

In another local measuring method (DD-PS 215174), a transient temperature field is generated in the measurement object and in the measuring arrangement. From the rate of temperature change can then close to the thermal conductivity of the coating, which in turn depends on the layer thickness of the coating. The method is applicable if a polluting surface is accessible as a test object. The arrangement in flue gas systems is not possible because it would have to be installed in the pipe of the water-steam system, a heat source. This is spatially and thermodynamically (would be cooled by water-steam medium) not feasible.

Another solution for determining the local slag attachment behavior is given by a probe. This probe has an uncooled head with a temperature measuring point and a cooled foot. At the uncooled head, slag form in the steam boiler interior. The slag is sampled, examined and evaluated in conjunction with the measured temperature. Thus, no measured values are present during the slagging process, which provide information about the state of slagging during operation.

To evaluate process parameters

- Flue gas temperatures (DE-OS 3505343),

Steam temperatures (US Pat. No. 2,811,954),

- Medium Drikes (DD-PS 217303)

used, from which references are derived for approach approach.

All these methods have the disadvantage that d? no information is given on the actual local conditions, but only average values or overall balance values of a heat transfer heating surface.

It is a method for determining the required experimental time for detecting the contamination behavior of heat exchangers known (DD-PS 262345). In this way, contamination maps of heat exchanger surfaces are determined in a minimum experimental time, which are the basis for an optimization with regard to the apparatus design, determination of favorable process conditions and appropriate cleaning cycles.

The results obtained are strictly valid only for the experimental conditions, such. B. fuel assembly and process parameters. Thus, during operation, the need for locally effective cleaning measures can not be displayed.

It is known to determine on the basis of external pipe temperature measurements internal pipe contaminants locally (DE-PS 868157). However, quantification of their strength is not possible.

Object of the invention

The aim of the invention is to continuously determine the state of slagging and thus derive information for the management.

Explanation of the essence of the invention

The object of the invention is to obtain temperature measurements by means of a probe for determining the state of slagging.

This is achieved in that, according to the invention, the temperature Twi on the inner wall and the temperature Tw. Jn of the outer wall of the cooled pipe part are set when a sufficiently large temperature difference T _w »-T _{w is} established

A _m R

Heat flux density q (r> 0 according to the known relationship q (rA> = f (Tw «- Tw, δ; Ar -t ² -) determined and the

"A

Slag batch temperature Ta according to the known relationship T _A = f (Tbk; <Ϊ (γα); o "o! Ε _Α ; Cn) and / or the slag _{batch thickness} according to the known relationship S = f (X _A ; T _Wj - T _wi ; q (r _A ); - ^ -) is calculated, where:

- Symbol A - Area

q - heat flux density

S - neck thickness

T - temperature

δ - pipe wall thickness

ε - blackness level

00 - Radiation constant of the absolutely black body X - Thermal conductivity

- indices

A - Approach q - outside

1 - inside

BK - combustion chamber

m - medium

Fl - flame

W - wall.

To realize temperature _{measuring points} T _Wj are on the outer and inner wall of the cooled pipe _part ; Twi arranged, wherein the cooled pipe part with a temperature difference T _w , - Tw; effecting wall thickness and / or choice of material is designed.

embodiment

In one embodiment, the invention is explained in detail. The drawing shows

1 shows the structure of the probe in principle,

Fig. 2: the schematic representation of the temperature conditions at the "probe.

The cooled probe tube 1 (Figure 1) has the closure bottom 2 with the opening 3 for the coolant inlet pipe 4 and the opening 5 for the passage of the thermocouples 14; 15; 16 on. The outer tube 1 has the opening 6 for the coolant outlet. Spacers 7 support the coolant inlet pipe 4 centrally in the outer tube 1. The intermediate bottom 8 separates the uncooled probe head 9 from the coolant. The probe head 9 is provided with holes 10. The measuring point 11 of the thermocouple 14 is located in the probe head 9 above the holes 10. The measuring points 12; 13 are arranged on the outer and inner walls of the cooled probe tube 1. The mode of action is the following:

The probe is retracted into the combustion chamber. The probe tube 1 is penetrated by the coolant flow. The amount of cooling water or its temperature is controlled so that the surface temperature of the outer wall of the pipe wall temperature of the installed heating surfaces corresponds and thus the same thermal approach conditions are present. Due to the cooling of the probe tube 1, a heat flow from the combustion chamber to the coolant via the probe tube 1 is established. The wall thickness δ and / or the material of the probe tube 1 is designed with its thermal conductivity λ so that a sufficiently large temperature difference is measured during the heat transfer from the tube outer wall to the cooled inner wall.

At the uncooled head 9 is due to the introduced holes, which reduce the heat conduction to the probe tube 1, a minimal heat flow, so that the measured temperature at the measuring point 11 corresponds approximately to the combustion chamber temperature. The reason for this is the all-round flushing of the probe head 9 with hot combustion chamber gases. At the probe head 9 slag will start, which warms up uniformly with the combustion chamber temperature on all sides, because it is not cooled. On the other hand, the slag lugs on the cooled probe tube 1 cool analogously to the combustion chamber tubes, because their heat is dissipated inwards towards the cooling medium (FIG. 2). With the formation of slag approaches, however, the heat flow on the cooled probe tube 1 is reduced, from which, taking into account the combustion chamber temperature Tbk under different firing conditions, the reaction temperature Ta and the attachment thickness S can be determined at any time

C A (Τ »- Tyyj) A _mA

q (γα) A _a

to calculate.

Where: A [m ² ] area

ql,] - heat flux density

r Im] radius

S [m] - gauge thickness

T (K) - temperature

6 [mj - pipe wall thickness

e [-_) - Blackness level

σ ₀ [W / m ² . k ⁴ ] - Radiation constant of the absolutely black body

XIII thermal conductivity

with the indices:

A - approach a - outside

m - medium Fl - flame

W - wall In general, the average area for a cylinder wall is calculated

A _n , = ^^ (4)

and thus the expressions for

A _mR δ

In Aa (r _w.) * (R _w. + S) fwi

(5)

Thereafter, the approach temperature Ta or the approach thickness S can be determined iteratively. The error calculation shows that sufficiently accurate results are achieved with estimated fluctuation margins of the influencing variables.

If the batch temperature Ta or the batch thickness S reaches a certain threshold value, cleaning devices are put into operation via a control unit, under the influence of which the probe is also cleaned.

From the determination of the temporal slagging behavior of the probe, the slagging tendency is evaluated and z. B. assessed the effectiveness of firing measures to reduce slagging.

The invention achieves the following:

1. Slag layer thicknesses and / or surface temperatures can be determined for each operating state of the furnace.

2. Slag layer growth and surface temperature can be assigned to specific operating conditions and flame positions.

3. From the slag growth, the optimal low-sludge operating conditions can be determined, selected and optimized.

4. The application of the invention enables a low-slag operation and steam boiler with increasing efficiency.

5. It can be heavily used for slagging fuel.

6. The slagging properties of different coal mines, blends and compositions can be tested and determined on the large scale plant.

7. The use of cleaning equipment can be determined or controlled.

8. The decommissioning of the steam boiler for cleaning can be predicted and planned prophylactically.

9. The coalification regime (mixed coal operation) is controllable.

Claims (8)

1. A method for determining the slag preparation temperature and the slag neck thickness on the pipe system in a combustion chamber or a heat plant, wherein the temperature is measured as the combustion chamber temperature T ₈ K temperature of an uncooled head of a provided with a cooled tube part probe tube, characterized in that the temperature T _W i on the inner wall and the temperature T _Wa on the outer wall of the cooled pipe part when setting a sufficiently large temperature difference T _Wa - Tw, measured, the heat flux density q (r _A ) according to the known relationship q (r _A ) = f (T _Wa -T _Wi ; δ; λ _Η -) and the slag approach temperature TA according to the known relationship Ta = f (Tbk; ή (ΐΆ); ^σ οΊ & a ', & fi) and / or the slag approach thickness according to the known per se Relationship S = f (λ_Α; T_Wa - Tw ,; Φ (γα); ) is calculated, where: - Formula sign
A - area q - heat flux density S - neck thickness T - temperature δ - pipe wall thickness ε - blackness level 0 ₀ - Radiation constant of the absolutely black body X - Thermal conductivity - Indices A - approach
q - outside 1 - inside BK - combustion chamber
m - medium
Fl - flame
W - wall 2. The method according to claim 1, characterized in that the slag approach temperature Ta and / or the slag approach thickness S is used as a display and / or control signal for the commissioning of cleaning devices. 3. The method according to claim 1, characterized in that the slag approach temperature Ta and / or the slag approach thickness S is used as a display and / or control signal for the operation of the combustion chamber or heat plant. 4. The method according to claim 1, characterized in that the slag approach temperature T _A and / or the slag approach thickness S is used as a control signal for decommissioning of the combustion chamber. 5. A device for temperature measurement for the determination of the slag approach temperature and the slag approach thickness on the pipe system in a combustion chamber or a heat plant, wherein a probe tube is provided with a cooled pipe part and a temperature measuring non-cooled head, characterized in that on the outer and inner walls of the cooled measuring elements (T _Wa ; Tw.) Are arranged, wherein the cooled pipe part is designed with a temperature difference (Tw _a - Twi) causing wall thickness and / or choice of material. 6. Apparatus according to claim 5, characterized in that arranged on the cooled pipe part uncooled head is provided with through holes. 7. Apparatus according to claim 5 and 6, characterized in that the uncooled head is arranged via a heat insulator on the cooled pipe part. 8. Apparatus according to claim 5 to 7, characterized in that the cooling of the cooled pipe part is adjustable. For this 2 pages drawings