EP2846087A2 - Method for operating a steam boiler and device for carrying out the method - Google Patents

Abstract

The invention relates to a method for operating a steam boiler and to an apparatus for carrying out the method. The steam boiler has an interior, a supply line for supplying liquid, a steam outlet, a discharge line for discharging liquid from the steam boiler and a boiler control, wherein according to the method by means of an analysis device several parameters are determined. In particular, a loss of energy during a discharge of liquid through the discharge line is determined as a parameter.

Description

The invention relates to a method for operating a steam boiler according to claim 1 and an apparatus for carrying out the method according to claim 9.

Steam boilers are used to generate steam, for example for industrial applications. For this purpose, a steam boiler, which encloses an interior pressure-tight except for inlets and outlets, fed a liquid and heated within the boiler to the boiling point. The resulting steam then flows out of the steam boiler and is used for technical applications. Most of the steam condenses in the technical application or a downstream condenser and is passed as liquid through appropriate facilities back into the boiler.

The liquid used is water. The evaporation of water leads within the boiler to a concentration of dissolved components, which do not evaporate. The disadvantage of this is that it can lead to a foaming of the water in the boiler and increases the moisture of the steam as a result. This can adversely affect the downstream technical application, especially in terms of efficiency and damage. In addition, the concentration also leads to settling of components, which can lead to sediment in the boiler. This sediment then inhibits the transfer of heat from a heat source to the liquid in the boiler, reducing the efficiency of the boiler. The efficiency is the ratio between the applied thermal power (of a burner) and dissipated net power (of the steam).

Detectable is the concentration of components in the liquid, among other things, based on the conductivity of the liquid within the boiler, which correlates with the concentration.

The concentration is encountered in the prior art by a regular discharge of liquid from the boiler, while supplementing with fresh liquid. For the dissolved components, the removal takes place via a so-called sagging device.

Such has a discharge line just below the level line. Undissolved components are preferably effected with a discharge line at the geodesic lower end of the boiler, so that sedimented components, the so-called sludge, is removed from the boiler (sludge).

A disadvantage of a discharge of liquid from the steam boiler is the associated loss of energy, because it is already discharged heated liquid. Accordingly, both the concentration and the discharge have a negative effect on the efficiency of the steam boiler. In particular, a lump-sum and oversized discharge is problematic.

The invention has for its object to overcome the disadvantages of the prior art and to provide a method which is suitable to optimize or increase the efficiency of a steam boiler. It should be economically and ecologically sensible and feasible in a simple manner.

This is achieved with the features of claims 1 and 9 according to the invention. Advantageous developments can be found in the dependent claims.

The invention relates to a method for operating a steam boiler, which has an interior, a supply line for supplying liquid, a steam outlet, a discharge line for discharging liquid from the steam boiler and a boiler control, wherein at least one parameter is determined by means of an analysis device, namely a determination of an energy loss in a discharge of liquid through the discharge line.

An advantage of this is that, with knowledge of the actual energy loss in a discharge of liquid optimizations can be made with regard to the future operation of the boiler. In particular, this can increase the boiler efficiency of the steam boiler. Namely, the determination of the actual energy loss of a discharge may be included in addition to taking into account a decreasing efficiency of the boiler (based on concentration). The efficiency of the boiler decreases as the amount of rejects increases, and the energy losses for discharge increase simultaneously with the operating time. The latter in particular because with increasing operating time more liquid must be discharged to reduce the concentration of components in the liquid in the boiler again. The efficiency of the boiler is now through targeted Termination of discharges can be optimized. Interruptions of the heating are preferably used for discharging, because here is a layering of the liquid and components according to their densities. Floating components settle on the boiler bottom. High efficiency leads to low operating costs and emissions. The process is also automated and therefore easy and convenient to carry out.

In determining the actual energy loss, the energy costs, e.g. Electricity for a pump and / or a valve to be taken into account. Likewise, the supplied energy of the supplementary supplied liquid can flow. However, these energies are relatively small in relation to the energy content of the effluent and can therefore be disregarded in simple process designs.

The method is particularly suitable when water is used as the liquid. This regularly contains components which do not evaporate, in particular salts. In addition, the water composition may vary by conditioning agent, so that the concentration varies rapidly.

For sludge removal, the discharge line at the geodesic lower end, ie at the boiler bottom, should flow out of the boiler, so that settled components, the so-called sludge or the sludge, can be removed from the boiler. In low-cost steam boiler variants also the desalination by means of this discharge line takes place.

For bleeding, however, preferably a discharge line (just below) provided below the level line. This is because more dissolved components build up and can be removed from the boiler with less fluid exchange. The concentration of components in the liquid can be determined by determining the conductivity of the liquid.

In a preferred embodiment, the steam boiler on two separate discharge lines, one for desalination and one for sludge. There are also no problems in adjusting the flow rate in the discharge lines. The desalination is namely usually continuous and slow, whereas the sludge briefly, abruptly and with high flow rate he follows. Cables and valves can be adapted to these requirements with two separate discharge lines.

A further embodiment of the method provides that the analysis device for determining the (actual) energy loss in a discharge of liquid through the discharge line determines a flow rate of the discharged liquid. With the help of the discharged flow rate can be deduced on the energy loss.

To determine the flow rate, a special variant of the invention proposes that this takes place with data of a quantity sensor in the discharge line or by a calculation based on a valve position of a discharge valve in the discharge line, a valve characteristic and a boiler internal pressure. A quantity sensor is particularly accurate, whereas the second variant without quantity sensor is less expensive.

According to a special process supplement, the analyzer for determining the (actual) energy loss in a discharge of liquid through the discharge line performs a determination of a temperature of the discharged liquid, preferably over time. Subsequently, an enthalpy flow is calculated based on the flow rate and the temperature of the discharged liquid. The enthalpy current over the period of the discharge corresponds to the energy loss. Preferably, the determination of the temperature takes place immediately behind a valve in the discharge line.

An alternative or additional embodiment of the method provides for determining the (actual) energy loss in a discharge of liquid through the discharge line, a determination of the internal pressure of the boiler in the interior. Subsequently, an enthalpy flow is calculated based on the flow rate of the discharged liquid and the internal pressure of the tank. Boiler pressure can be used to determine the corresponding boiling point of the liquid. This can be used to convert the flow rate into an enthalpy flow. For this purpose, a pressure sensor, which is usually present anyway, can be coupled to the analysis device.

For analysis purposes, according to one embodiment of the method, a record of the flow rate over the entire operating period and a resettable Period. A recoverable period is understood to mean a past time that can be set to zero by resetting, similar to a day counter of a motor vehicle. However, it is also a sliding time window available, which considers a defined period of time before the current time.

For analysis, a special process design provides that a comparison is made between the flow rate over the entire operating period and the flow rate over the resettable period, and a signal is issued when the ratio between the two flow rates changes over time by a defined amount.

This comparison reveals changes in boiler efficiency. In particular, it is also possible to infer changes in the liquid supplied. Thus, for example, a deterioration of the feedwater quality can be detected. Appropriate measures to optimize boiler efficiency can then be taken. The signal output may comprise a visual output of an indication on a display device, e.g. a warning light, a traffic light or a screen, in particular with a graph showing the flow rate and / or the boiler efficiency.

In addition, an absolute comparison between the flow rate over the entire operating period can be made with a predefined value and a signal can be output if this flow exceeds the predefined value. Accordingly, the method may be supplemented by the output of a signal when it is determined by comparison that the flow rate over the resettable period exceeds a predefined value.

A further analysis is carried out in a method variant by calculating a ratio between the flow rate and an amount of liquid supplied from the parameters, amount of steam or thermal power. If the calculated ratio changes over time by a defined amount, a signal is output.

Using the parameters thus determined, conclusions can be drawn about the amount of components removed. The discharge can thus be designed so that as little liquid is discharged from the boiler. Accordingly, little energy is lost. To design the discharge The opening positions and opening times of the valve in the discharge line can be varied.

To determine the amount of steam, a quantitative measurement of the steam is preferably carried out. The thermal power is preferably determined by measuring the quantity of fuel used, e.g. Gas or oil. If there is no quantity measuring device for this fuel quantity, the supplied power can alternatively be determined by the so-called burner load request, which specifies the default value of the requested service. This in particular by scaling the burner load requirement to the actual burner performance and integration over the defined period. Alternatively, to determine the useful power is a quantity measurement of the steam boiler supplied liquid, in particular the feedwater quantity.

• die zugeführte Flüssigkeitsmenge wird über eine Drehzahlvorgabe der zuführenden Pumpe, den Innendruck im Dampfkessel und die Pumpenkennlinie ermittelt; oder
• die zugeführte Flüssigkeitsmenge wird über eine Ventilstellung eines in der Zuführleitung positionierten Ventils, z.B. durch Position des Schrittmotors des Ventils, sowie dem Innendruck im Dampfkessel und die Ventilkennlinie ermittelt; oder
• die zugeführte Flüssigkeitsmenge wird durch einfache Zweipunktregelung bestimmt, indem der Flüssigkeitsmassenstrom bei offenem Ventil gleich der Pumpennennleistung gesetzt wird.

If there is no quantity measuring device for the steam and / or the liquid inflow, the following alternatives exist to determine the net output:

• the amount of liquid supplied is determined by a speed specification of the feeding pump, the internal pressure in the steam boiler and the pump characteristic; or
• the amount of liquid supplied is determined via a valve position of a valve positioned in the supply line, for example by the position of the stepping motor of the valve, as well as the internal pressure in the steam boiler and the valve characteristic; or
• the amount of liquid supplied is determined by simple two-point control by setting the liquid mass flow at open valve equal to the rated pump power.

Furthermore, the invention relates to an apparatus for carrying out the method described above, with a steam boiler, from which opens a discharge line, and with an analysis device for determining an (actual) energy loss in a discharge of liquid through the discharge line.

With such a device, it is possible to determine the actual energy loss of a liquid discharge and to take into account in future discharge operations, in particular with regard to maximizing boiler efficiency, taking into account energy losses during discharge. The procedural advantages can be realized accordingly with such a device. It can the Be complemented device according to the procedural respectively necessary device features.

Thus, the steam boiler can be supplemented, inter alia, by a return line, so that the discharged steam after an industrial application back into the boiler is conductive, preferably condensed as a liquid. This gives little energy to the environment. This also increases the efficiency of the steam boiler.

In a further embodiment, the device has a quantity determination device for determining a flow rate in the discharge line. The quantity determination device can be a quantity sensor or a quantity determination via the valve position, valve characteristic and internal pressure of the internal combustion chamber. The specific flow rate can be used to deduce the energy loss during a discharge.

Fig. 1

eine schematische Anordnung eines Dampfkessels mit Analyseeinrichtung und Sensoren.

The drawing illustrates an embodiment of the invention and is shown in FIG

Fig. 1

a schematic arrangement of a steam boiler with analysis device and sensors.

In Fig. 1 If one recognizes a steam boiler 1. This surrounds a hollow interior 2 with boiler bottom 15. The interior 2 is partially, namely up to a level line, filled with liquid 100. At the geodesic upper end of the boiler 1, a steam outlet 4 opens. This is connected via a steam line 16 with a consumer 9. From the consumer 9 performs a return line 10 back into the boiler 1. It opens in particular below the liquid line in the boiler 1 a.

Furthermore, one recognizes a feed line 3, via which fresh liquid 100 is introduced into the steam boiler 1. In the supply line 3, an inflow valve 17 is arranged via which the supply of liquid 100 is releasable and lockable.

Both the return line 10 and the feed line 3 initially open into a common feed vessel 30. In the feed vessel 30, the recirculating liquid 100 is collected and mixed with fresh liquid 100, which replaces any lost liquid 100. Behind the storage vessel 30 share the Return line 10 and the supply line 3 a common line section. In this is the inflow valve 17th

At the geodetic lower end of the steam boiler 1, in particular on the boiler bottom 15, opens a discharge line 5 for discharging liquid 100 from the boiler 1 from. With this discharge line 5 a sludge is feasible. In the discharge line 5, a discharge valve 11 is arranged. On the side of the discharge valve 11 facing away from the steam boiler 1, a first temperature sensor 12 and a quantity sensor 18 for determining a flow rate are positioned and connected to an analysis device 6.

In addition, a second discharge line 40 discharges from the steam boiler 1. This serves for desalination. For this purpose, the orifice is just below the level line of the liquid 100. In the second discharge line 40, a second discharge valve 42, a second temperature sensor 44 and a second quantity sensor 46 are arranged. The second temperature sensor 44 and the second quantity sensor 46 are each communicatively connected to the analysis device 6. In addition, an outside temperature sensor 8 is provided, which is also connected to the analysis device 6.

Furthermore, one recognizes a burner 20 which supplies heat to the liquid 100 in the steam boiler 1. To transfer the heat to the liquid 100, the burner 20 has a heat exchanger 22. This is performed, inter alia, as a horizontal flame tube 22, which passes through the interior 2 of the boiler 1. It is below the level line.

To control the steam boiler 1, a boiler control 7 is provided which is connected to the burner 20, the first discharge valve 11, the second discharge valve 42 and the inflow valve 17. The three valves 11, 17, 42 are electrically adjustable by the boiler control 7. The boiler control 7 is communicatively connected to the analysis device 6.

In addition, the boiler controller 7 is communicatively connected to a pressure sensor 19 for determining a boiler internal pressure and an exhaust gas temperature sensor 21 in the region of the flame tube 22.

With such a device, the inventive method is feasible.

Deviating from the presentation of Fig.1 For example, the analysis device 6 may optionally be designed as part of the boiler control 7. In addition, it is also possible to let the feed line 3 and the return line 10 separate into the boiler 1. Preferably, a feed vessel 30 is then arranged in the return line 10.

Claims (10)

A method of operating a steam boiler (1) having an internal space (2), a supply line (3) for supplying liquid (100), a steam outlet (4), a discharge line (5) for discharging liquid (100) from the steam boiler (1) and a boiler control (7), characterized by determining at least the following parameter with the aid of an analysis device (6): a) determining an energy loss in a discharge of liquid (100) through the discharge line (5). Method according to claim 1, comprising the step of the analysis device (6) for determining the loss of energy during a discharge of liquid (100) through the discharge line (5): b) determining a flow rate of discharged liquid (100) through the discharge line (5). Method according to claim 2, comprising the step: c) determining the flow rate with data of a quantity sensor in the discharge line (5) or by a calculation based on a valve position of a discharge valve (11) in the discharge line (5), a valve characteristic and a boiler internal pressure. Method according to one of claims 2 or 3, comprising the step of the analysis device (6) for determining the energy loss in a discharge of liquid (100) through the discharge line (5): d) determining a temperature of the discharged liquid (100); and e) calculating an enthalpy flow based on the flow rate and the temperature of the discharged fluid (100). Method according to one of claims 2 to 4, comprising the step of the analysis device (6) for determining the energy loss in a discharge of liquid (100) through the discharge line (5): f) determining a boiler internal pressure in the interior (2); and g) calculating an enthalpy flow based on the flow rate of the drained liquid (100) and the internal pressure of the tank. Method according to one of claims 2 to 5, comprising the step: h) Recording the flow rate over the entire operating period and over a resettable period. Method according to claim 6, comprising the step: i) comparison of the flow rate over the entire operating period and the flow rate over the resettable period; j) output a signal if the ratio between the two flow rates changes over time by a defined amount. Method according to one of claims 2 to 7, comprising the step: k) calculating a ratio between the flow rate and an amount of liquid supplied from the parameters, amount of steam or thermal power; I) Output of a signal when the ratio changes over time by a defined amount. Apparatus for carrying out the method according to one of claims 1 to 8, comprising a steam boiler (1) from which opens a discharge line (5), and with an analysis device (6) for determining an energy loss during a discharge of liquid (100) through the Outfeed line (5). Apparatus according to claim 9, characterized by a quantity determining device (18) for determining a flow rate in the discharge line (5).

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