WO2018211192A1 - Method and device for determining a moisture content of an organic material used as a fuel - Google Patents

Abstract

The present invention relates to a method for determining a moisture content of an organic material used as a fuel in an organic material boiler, to the device implementing the method of the invention, as well as to a method for determining the performance of said boiler.

Description

 METHOD AND DEVICE FOR DETERMINING A MOISTURE RATE OF AN ORGANIC MATERIAL USED AS A FUEL

DESCRIPTION

Technical area

 The present invention relates to a method for determining a moisture content of an organic material used as a fuel in a boiler for organic matter, the device implementing said method of the invention, and a method for determining the performance of said boiler.

 The present invention finds, for example, applications in the field of industrial biomass boilers producing hot water or steam, which are supplied with fuel continuously by an automatic device and which have a regulating device, which enables also automatically adapt their instantaneous power to the need for heat or steam.

 In the description below, references in brackets ([]) refer to the list of references at the end of the text.

State of the art

 Currently, it is not easy to know instantaneously the performance of a boiler burning organic matter such as wood in fragmented form.

 Indeed, biomass fuels have very variable qualities in terms of nature, origin, particle size, density, moisture content and / or composition, and ultimately calorific value.

 Currently, it is not possible to measure continuously, at a cost and at a cost that is compatible with their market value, the composition of these fuels (in particular their moisture content) and their flow rate at the boiler inlet. Now these two information make it possible to calculate the instantaneous power provided by the fuel.

Continuous knowledge of the fuel moisture would automatically adjust the settings of the boiler (recipes) so gain in precision and energy efficiency. It would also make it possible to continuously calculate the fuel cost of the fuel and to make reliable the delivery payment transactions that are currently based on the delivered tonnage weighted by the humidity measured on a sample on each load. Lastly, it would make it possible to greatly improve operating performance calculations (particularly on cogeneration plants that must contractually obtain minimum returns).

 The knowledge of the instantaneous yield must for its part allow the operator to better pilot a boiler to favor over the season the generators that have the best performance, and to alert of an abnormal degradation of their performances.

 Over time, it has become apparent that the simple value of smoke moisture, which is an intermediate value generated by the calculation process, is a parameter that is increasingly used. For example, the administration begins to impose its measurement on sites equipped with continuous measurements of particles. These measurements are carried out on the chimney on damp fumes, but the regulation expresses the VLE (Values Limits of Emission) on dry fumes. To make the correction, it is therefore necessary to have a measurement of the moisture content of the fumes. For example, hot water boilers suffer from corrosion problems induced by the desire to optimize their energy performance (as much as possible reducing the flue gas temperature to limit losses, but at the risk of causing their condensation in the heat exchangers ). The measurement of the humidity of the fumes and their temperature makes it possible to calculate their temperature of condensation, thus to envisage a risk of condensation (if the temperature of the fumes is too close to the temperature of dew).

 To date, in commercialization, there is no complete solution meeting the market need described above. On the other hand, some companies propose elements of response, but which are either partial or at prices that are incompatible with the financial means of the companies, or which are not adapted to certain contexts (eg fuel too variable for direct measurements, smokes too aggressive , etc.).

The humidity of the biomass is the most impacting parameter on its PCI. The ash rate is also important but its value generally fluctuates in a small range (0.5 to 3%) so that one can get rid of its measurement. On the boiler rooms the measure of the PCI is thus done by the measurement of the humidity. To do this, a device was developed and marketed by the company Bestwood (Sweden) which consists of a laser spectrometer connected to an optical fiber which can be mounted on a prick probe at the end of an automatic arm; which then makes it possible to measure the moisture content of the delivery trucks before unloading, or mounted above a conveyor belt to thus assess the moisture of the biomass during conveying, for example at the boiler inlet. Although this is the only non-destructive method of accurately measuring biomass moisture, its purchase and maintenance price over several years is far too high. Several companies market optical devices using the near infrared for measuring biomass moisture at the boiler inlet, such as the NTIR device marketed by Berthold or Edit. An infrared source emits on 1 to 2 wavelengths, the beam reflection on the surface of the wood samples makes it possible to measure their humidity. Although this method is non-destructive and can be installed on a conveyor belt for an acceptable cost, it can only be used if a fuel of constant quality is available and for which the device has been specifically calibrated as it there is no universal calibration; This is prohibitive for supplies of varying quality. A more recent ECRIN method patented by the company Cylergie (Patent FR 3020139) [1] is based on a cabinet that calculates the humidity of the fumes from oxygen measurements on the wet and dry fumes and on a calculation tool which from this information and others recovered from the boiler provides the moisture of the wood and the efficiency of the boiler. However, this method is very dependent on the quality of the oxygen sensors in wet and dry smoke, but these probes drift slightly and are difficult to calibrate. The method is therefore difficult to implement.

Many other materials are marketed for the continuous measurement of smoke moisture but none is adapted to our technical and economic context: that is to say that the sites on which this measure is necessary, are not ready to devote budgets above € 10k for such a solution (otherwise its profitability is too uncertain) and that the materials must be robust and not require frequent intervention for the cleaning, etc. .... One can note for example the capacitive sensors (for example of the Vaisala brand). These are micro-electronic probes of small size (approximately 0.1 cm ² ), developed to perform measurements in ambient air and which can also be used on fumes. The measurements are in situ (in the flue pipes). But the quality of biomass fumes means that these probes, although inexpensive, are not very accurate, drift quickly and are quickly deteriorated so that they must be changed very often (sometimes every month). There may also be noted the dew point hygrometer (for example of the Gruter & Marchand brand). It is an extractive device that passes fumes on a cooled mirror that detects the onset of condensation. The equipment therefore actually measures a dew point. By calculation, we then go back to the humidity of the fumes. Although the price / quality ratio is quite good, the use of this equipment on the fumes is not satisfactory. Indeed it has not been developed for fumes that potentially contain particles that will disrupt the device and condensable gases that will disrupt the measurement with the mirror. We can still note the OFCEAS technology. This is another extractive method marketed by the company AP2E since 2012 (equipment of the PROCEAS range) which provides reliable and accurate values but for a much higher budget than the previous one. Although this method is accurate and well adapted to biomass fumes, the equipment is too expensive to be integrated in a chain of measurement of biomass moisture and boiler performance. Lastly, we can note LASER technology in situ (for example from ABB). This in situ laser technology (chimney) measures moisture through a laser beam that passes through the flue gas stream. Although the measurement is very precise and representative and very well adapted to biomass fumes, this material is also much too expensive to be integrated into a chain of measurement of biomass moisture and boiler performance.

Finally methods use the measurement of instantaneous efficiency by combustion fumes. These solutions conventionally used to calculate the instantaneous yields of gas or fuel combustions. They give results all the more precise as the characteristics of the fuel are well defined (Siegert method). For these fossil fuels, if we know the temperature of the combustion air, and that of the fumes as well as the excess air of the the boiler efficiency can be estimated with good accuracy. Since it is easy in this case to measure the fuel flow (gas or oil meter), the instantaneous power of the boiler can be calculated. The case of biomass is more complicated. In addition to the temperatures and the oxygen content of the fumes, their moisture must be measured in order to calculate a yield and to estimate the fuel flow rate their flow must be measured. Although it is a very reactive method and that allows almost instantaneous to have the characteristics of the combustion and thus lends itself well to a use in regulation of conduct, the computational method based on the equations of the combustion is very long. It also requires very high accuracy instrumentation because a very small error on the input data (smoke humidity in particular) generates a very large error on the estimation of the fuel moisture; This method is not implemented by hardware manufacturers.

 It follows from the following that none of the potentially usable solutions for continuously measuring the characteristics of biomass is currently applicable in a generic manner. Existing solutions only give accurate results over a narrow range of fuels. Moreover, they are not robust to changes in fuel quality or environmental conditions. For example, humidity measurements by NTIR are affected by the surface condition, particle size, color, etc. of the samples. Only Bestwood's solution currently meets some of the specifications but its cost makes it totally unusable on all sites. As for the method of measurement by fumes, no boiler manufacturer is able to implement the necessary measurement chain at an acceptable cost. More affordable methods would be potentially usable, eg dew point hygrometer, or even capacitive probe, but the latter two technologies have not proven themselves on biomass combustion fumes.

When using a conventional method to calculate boiler performance (and not a SIEGERT type method), you also need access to a fuel flow value. This measurement can be made in the conveying devices but it will then be very sensitive to the characteristics of the fuel: density, grain size, humidity, etc. supply of fuel to sites of very variable and unpredictable quality in advance, it is necessary to have solutions whose response quality is completely independent of the measured product. Other methods evaluate the mass flow rate by the number of strokes, or similar devices. Thus the volume of fuel introduced by each movement of the supply system in the boiler is estimated by a prior calibration, then the number of cycles is counted. Although this method only requires the equipment of the boiler with a simple counting device, the calculation of the mass flow from the indexed survey is highly estimated and unreliable because the fuel has a variable density and the device diet is never filled in the same way. A last way to calculate the fuel flow is to go through the measurement of the flue gas flow (knowing their excess air and fuel moisture can then be calculated by going back to the fuel flow). But the precise measurements of the flue gas flow are also difficult to achieve. The classic pitot tube method, if it is robust, only gives good results over a fairly restricted flow range. On the other hand, it must be carefully maintained to prevent the clogging of the tube by dust or condensation of fumes. Ultrasonic methods, which operate over a much wider measuring range and are less susceptible to maintenance failure, have not yet been proven.

 There is therefore still a need for a generic method for reliably and accurately calculating the moisture content of an organic material used as fuel in a boiler and the efficiency of said boiler, which does not have the disadvantages and disadvantages. art.

Description of the invention

It is possible, in a biomass boiler, from smoke measurements, if accurate, to calculate the fuel moisture. These parameters combined with an equally accurate measurement of flue gas flow and conventional temperature measurements on the boiler make it possible to calculate the efficiency of an installation. However, this method is not currently implemented because it faces a major problem: the boilers are not, for economic reasons, equipped with the necessary instrumentation.

 The solution provided by the inventors of the present invention has made it possible to develop a specific material for measuring the humidity of the fumes from the measurement of the flow of condensed water in the device drying fumes by cooling and condensation of their moisture .

 To do this, the inventors have developed a device for measuring the humidity of the fumes by the appreciation of the condensate flow generated during the drying by cooling of the fumes. It is based on the principle of Figure 1 described below:

 1) the fumes arrive directly in a cold unit or condenser without going through a wet oxygen measuring probe Û2h;

 2) the condensate flow rate is measured using a micro-flow meter (a few ml / h);

3) the flow rate of fumes passing through the condenser is measured;

 4) the gross moisture of the fumes is calculated (micro-flow meter flow / flue gas flow);

 5) knowing the temperature of the condenser, the residual moisture is added to the raw moisture to obtain the actual humidity of the fumes.

 The subject of the present invention is therefore a process for determining a moisture content of an organic material used as a fuel in a boiler comprising a flue gas duct for evacuating combustion fumes from the organic material in the boiler, characterized in that if a flue gas sampling is carried out in the flue gas duct, the moisture content in the flue gases taken by measuring the flow rate of the condensates generated during the drying by cooling said flue gases in a condenser is determined, and the firing rate is determined. humidity of the organic material as a function of the moisture content of the fumes and the oxygen content in the fumes taken at the same place and after drying of said fumes in a condenser.

According to a particular embodiment of the present invention, said method for determining humidity content comprises: a) measuring the flow rate of the condensates generated in the condenser of the collected fumes arriving directly in the condenser, by cooling and condensation of their moisture;

 b) the measurement of the flow of dry smoke downstream of the condenser;

 c) measuring the gross moisture content of the fumes from the measurements of steps a) and b);

 d) measuring the actual humidity of the fumes from the measurement of step c), to which is added the value of residual moisture remaining in the flue gas leaving the condenser and evaluated from the temperature and the pressure in the condenser.

 As shown in Figure 2, the fumes are taken by a heated sampling line (1) in the chimney. This line maintains them at 160 ° C to avoid any risk of condensation upstream of the condenser. The connection with the condenser must be perfectly thermally insulated.

 The fumes then pass into the condenser or cold unit (2), which includes a refrigerating machine that will lower the flue gas temperature to about 5 ° C.

 The condensates are extracted from the condenser by a peristaltic pump (3) before arriving in the device for measuring their flow (4).

 According to a particular embodiment of the present invention, the flow rate of the condensates of step a) of said moisture content determination method is measured after extraction of the condensates from the condenser, for example by a peristaltic pump, by a microswitch. flow meter, or by a dynamic mass measurement of a container that collects these condensates and self-draining when full.

 This measuring device can be of different natures. It must measure a flow rate of 0.3 to 60 ml of water / h, so very low. The measurement must be done automatically. The imagined measurement solutions are detailed below, they represent an essential innovation.

 At the outlet of the condenser the fumes pass on a probe for measuring the oxygen on dry smoke (5).

A pressure sensor is connected to the flue gas circuit at the outlet of the condenser (6). It allows to appreciate continuously the pressure of the condenser for perform the correction of the residual moisture content of the flue gases at the condenser outlet.

 According to a particular embodiment of the present invention, the pressure of the condenser of said moisture content determination method is continuously measured by a pressure probe located at the outlet of the condenser.

 The fumes then pass into a suction pump (7).

 According to a particular embodiment of the present invention, the dry fumes of said humidity determination method are sucked by a pump placed downstream of the pressure probe.

 Downstream of the pump, the dry fumes pass into a flow control device (8) which can be of different types (for example venturi) and its function is to maintain a constant flow rate in the device. They then arrive in a device for measuring their flow rate (9) which must be able to measure flow rates of between 30 and 120 l / h. This body must make an automatic measurement. It may consist of any sufficiently precise device (for example: mass flow meter, rotameter with automatic reading, etc.).

 According to a particular embodiment of the present invention, a constant flow rate of the fumes of said moisture content determination method is maintained by a flow control member (8) located downstream of the suction pump.

 According to a particular embodiment of the present invention, the flue gas flow rate of said moisture content determination method is measured by a measuring member located downstream of the flow control member and the suction pump.

A calculator (1 1) provides the water content of the flue gases from the condensate flow rate, the dry flue gas flow rate. It corrects this value of the residual water content of the flue gases at the condenser outlet, itself calculated with the pressure of the condenser and its average "resultant" temperature, evaluated during the calibration phase of the device (description of the method below). below 5.2.3). The computer also provides, using in addition data on the temperature and humidity of the combustion air (10), the oxygen content of the dried fumes (5), the fuel moisture. According to a particular embodiment of the present invention, the water content of the fumes of said humidity determination method is measured by a computer, from the condensate flow rate and the dry flue gas flow rate.

 Condensate flow measurement is the most delicate point of the device. This flow rate is very low and it must be measured on a fluid that is not in charge (drip at the output of peristaltic pump). Two solutions are retained at this stage, which are shown in Figure 3:

 1 - a measurement with a tilting bucket device (rain gauge type), in this case an index is incremented at each changeover,

2- a device with a container on a mini scale and therefore dynamic measurement of the weight of condensates. Such a device can also be tilting, or equipped with an electromechanical device that empties it once full. The mass measuring device must recognize the moment when the mass decreases (emptying) to reset the measurement.

 In the mechanical device the container (1) is mounted on a tilting axis and is equipped with a counterweight (5) and a siphon (4). The assembly is mounted on a scale (2) connected to a computer (3).

 In the electromechanical device the container (6) is equipped with a high level contact (9) and a drain solenoid valve (10). The computer (7) triggers the opening of the solenoid valve when the high level is reached.

 Any other solution for measuring very low liquid flow rates under these conditions can also be used in the process of the invention.

The residual humidity of the flue gases at the cabinet outlet is measured, which makes it possible to go back to the "resulting" condensing temperature of the cold unit or condenser; i.e. the average effective temperature at which the fumes are subjected in the cold or condenser unit. This temperature is the temperature that must be entered into the calculator. An example of the solution for determining the resulting temperature of the condenser is shown in the table below:



Le volume de fumées en sortie du piège à froid condenseur peut aussi être mesuré à l'aide d'un compteur volumétrique de gaz, plutôt qu'avec un rotamètre et un chronomètre.

The volume of flue gas at the outlet of the condenser cold trap can also be measured using a volumetric gas meter rather than with a rotameter and stopwatch.

 From the measurements made, the formula for calculating the humidity of the fumes (in%) is determined:

(^ condensate A _I_ LJ n

-j _^ g ^■ n JT residual smoke fumes ^{■ u}

With Dondensat: Condensate flow measured at the outlet of the refrigeration unit (g / h) Dumes: Flue gas flow at the outlet of the refrigeration unit (in Nl / h)

 Hidesidueiie fumes: Residual humidity of the fumes at the outlet of the cold group (in%)

Residual ^Hmas

 18

drinks. n _rs i (i _ue ii _e fumes _î ooo HMAS

 _l_ residual * 22 4

1.29 18

 With: Residual HMA: Residual smoke humidity measured during the calibration phase of the cold unit (in g of water / kg of dry smoke)

_ Psat _H2 o

Let: ^ residual fumes _p

 ^ box

 With: PsatH2o: saturation vapor pressure at the resulting condenser temperature

Psat _H20 = 0.0366. T _cond ² + 0.1106. T _cond + 6.7975

 With: T∞nd: resultant condensing temperature measured during the condenser calibration phase

 Pcoffret: pressure in the box Measuring box measured downstream of the condenser

 According to a particular embodiment of the present invention, the method for determining humidity content further comprises the following correction measures:

 - the absolute humidity of the combustion air, calculated from the temperature and the relative humidity of the combustion air;

 the amount of water supplied by the reagent and the reaction products in the case of treatment to reduce the nitrogen oxides of the fumes with solutions using urea or ammonia.

The ambient air comprises between 0.8 and 2% of moisture, which must be deduced from the humidity of the fumes to obtain the water coming from the organic matter, by example of wood. It is therefore necessary to measure this humidity. The usual equipment used (climatic engineering) perform measurements of the relative humidity in% (humidity / humidity at saturation in water at the given temperature), which must be associated with a measurement of dry temperature (air temperature). ) to obtain the absolute humidity in% (volume of water / total volume of air).

 To reduce the nitrogen oxides of the fumes, DeNOx treatment can be carried out by introducing into the furnace of the boiler a reagent consisting of urea or ammonia and water. But after reaction, urea or ammonia also produce water. It is therefore necessary to deduce these quantities of water from those initially contained in the fumes because they do not come from the water of the organic matter. For this, it is necessary to measure the flow rates of urea or ammonia and water introduced into the boiler and translate them into water concentration in the fumes.

 The present invention also relates to a device for determining a moisture content of an organic material used as a fuel in a boiler comprising a flue gas duct to evacuate the flue gases from the organic material in the boiler, said device characterized in that it comprises smoke sampling means in the flue gas duct, and measuring means able to determine a moisture content of the organic material as a function of the smoke moisture content measured in the flue gases. sampled and the oxygen content of the fumes measured in the fumes taken at the same place and after drying said fumes in a condenser, said measuring means implementing a method according to one of the preceding claims.

 According to a particular embodiment of the present invention, the measuring means of said humidity determination device comprise:

 an oxygen measurement probe;

 - a smoke condenser;

 a condensate extraction system of the condenser, for example a peristaltic pump;

 - a micro-flowmeter, or a dynamic weighing system to measure the flow of condensates;

 a pressure probe;

- a suction pump; a regulator of the flue gas flow rate;

 - a device for measuring the flow of fumes;

 a probe for measuring the relative humidity and the temperature of the combustion air;

 a device for measuring injected reagent flow rates in the case of NOx treatment of the fumes; and

 a calculator of the water content of the fumes and of the moisture of the organic material used as fuel.

 The present invention also relates to a process for determining the performance of a boiler for an organic material comprising a flue gas duct for evacuating combustion flue gases from the organic material in the boiler, said method comprising:

 a) the determination of the moisture content in the flue gases taken from the flue gas and the oxygen content of the fumes taken at the same location and after drying of said fumes in a condenser, implementing a method of determining a moisture content of an organic material according to the invention;

 b) determining the moisture content of the organic material used as fuel from the measurements of step a);

 c) determining the lower heating value (LHV) of the organic material used as fuel from the measurement of step b);

 d) the determination of the volumetric flow rate of the flue gases taken from the flue gas duct; and

 e) determining the mass flow rate of organic material used as fuel from the measurement of step d);

 f) determining the power provided by the organic material used as fuel from the measurements of steps c) and e);

 (g) the determination of the power delivered by the boiler;

 h) determining the instantaneous efficiency of the boiler from the measurements of steps f) and g).

According to steps a) and b), the sampling of fumes, the determination of the moisture content in the fumes by a condensate flow measurement extracted from smoke in a condenser, and the determination of the moisture content of the organic material can be carried out continuously.

 According to step c), by making a hypothesis on the nature of the organic matter (eg considering that it is wood), it is possible to give an estimate by considering a calorific value of dry matter, and by decreasing this calorific value by the latent heat of vaporization of the water which corresponds to the estimate of the moisture of said organic matter.

 According to steps d) to f), a mass or volume flow of the fumes and an oxygen content in the fumes are measured and, in combination with the estimated heating value, a mass flow of organic matter and a power output are deduced therefrom. by the organic matter. The flue gas flow is related to the combustion air flow rate and the fumigant volume of the organic matter. The oxygen content makes it possible to evaluate an excess of air admitted as an oxidizer. We deduce the volume of fumes generated and therefore the flow of material that is burned.

 According to step g), a power of loss by the fumes is deduced from the measurement of flow and a measurement of the temperature of the fumes. The thermal losses of the boiler are also estimated and a power delivered by the boiler is deduced by deducting the powers of loss from the power supplied by the organic material.

 According to step h), from one of these evaluations of the power of the boiler and the power provided by the organic material, an instantaneous efficiency of the boiler is deduced. This information is particularly interesting for checking that the boiler is working properly.

 According to the invention, the fuel flow can be adjusted in real time according to at least one of the following parameters: instantaneous efficiency of the boiler, power of the boiler, power provided by the organic material. Depending on the purpose of the energy supply, the boiler operation can be optimally and automatically adjusted, particularly with regard to the quality of the fumes. In particular, it is possible to vary, for the same power to be supplied, the settings of the distribution of the primary air under the fuel and the proportion of secondary air in the combustion chamber as a function of the fuel moisture.

According to the invention, the organic material may be wood. According to the invention, it has also been useful to make corrections on several of the measurements carried out within the framework of the method, as explained hereinafter.

 According to a particular embodiment of the present invention, said method for determining the performance of a boiler for organic matter also comprises the following correction measures:

 - the absolute humidity of the combustion air, calculated from the temperature and the relative humidity of the combustion air;

 the amount of water supplied by the reagent and the reaction products in the case of treatment to reduce the nitrogen oxides of the fumes with solutions using urea or ammonia.

 The ambient air comprises between 0.8 and 2% of moisture, which must be deduced from the humidity of the fumes to obtain the water coming from the organic material, for example wood. It is therefore necessary to measure this humidity. The usual equipment used (climatic engineering) perform measurements of the relative humidity in% (humidity / humidity at saturation in water at the given temperature), which must be associated with a measurement of dry temperature (air temperature). ) to obtain the absolute humidity in% (volume of water / total volume of air).

 To reduce the nitrogen oxides of the fumes, DeNOx treatment can be carried out by introducing into the furnace of the boiler a reagent consisting of urea or ammonia and water. Or after reaction, urea or ammonia also produce water. It is therefore necessary to deduce these quantities of water from those initially contained in the fumes because they do not come from the water of the organic matter. For this, it is necessary to measure the flows of urea or ammonia and water introduced into the boiler and translate them into water concentration in the fumes.

Brief Description of Figures

 - Figure 1 shows the principle of measuring the humidity of the fumes via the condensate flow.

 FIG. 2 represents the general fluid diagram of the device for measuring the humidity of the fumes via the condensate flow.

- Figure 3 shows the two solutions for measuring the flow of condensate. FIG. 4 represents the diagram of a boiler comprising a device according to the invention.

 FIG. 5 represents the diagram of the method according to the invention. Detailed description of the invention

 A boiler for organic matter, also known as biomass, conventionally comprises a combustion chamber (1), conveying means (2) for feeding the organic material into the combustion chamber (1), blowing means (3). ) to inject combustion air into the combustion chamber (1) and a flue (4) to evacuate the combustion fumes (Figure 4).

 The organic material is brought gradually or in batches by the conveying means (2) into the combustion chamber (1). The combustion of this material is carried out using combustion air supplied by the blowing means (3). The fumes generated are extracted via the flue (4) via a possible treatment system (not shown), in order to reduce the pollutant level.

A system for determining the humidity in the organic material according to the invention comprises means for sampling (5) fumes in the flue (4), and calculating means (6) able to determine a rate of Moisture of the organic matter as a function of the smoke moisture content deduced from measurements in the collected fumes. The smoke sampling means (5) are arranged at a point in the duct, preferably close to the boiler. As shown in Figure 1, the fumes taken directly arrive in a cold group or condenser without going through a wet oxygen sensor Û2h; the condensate flow rate is measured using a micro-flow meter (a few ml / h); the flow rate of fumes passing through the condenser is measured; the gross humidity of the fumes is calculated (micro flow rate / flue gas flow rate); and knowing the temperature of the condenser, the residual moisture is added to the raw moisture to obtain the actual humidity of the fumes. The condenser brings the fumes to a temperature between 0 ° C and 5 ° C, to condense them. The device of the invention also comprises means for measuring (not shown) the humidity of the combustion air, for example disposed near the blowing means (3).

 The calculation means (6) perform the calculations below to go back to the instantaneous efficiency of a boiler, considering for example that the organic material is wood. The calculations are made by following the steps of Figure 5 presented below chronologically:

^> © General equation of wood combustion

Volumes (powers) dry comburivore and dry fumigene

^■ =! © Oxygen ratio on dry fumes + Dry comburivore volume VAS + Dry smoke volume VFS

Excess air

^■ =! © Excess air + Humidity of fumes + Oxygen ratio on dry fumes + Composition of wood

Moisture of the wood> j> PCI ashless wet wood

^■ =! © Volume flow rate of fumes

 XL

 Mass flow of ashless wet wood

^■ =! © Mass flow of ash-free wet wood dbm + PCI ashless wet wood Power supplied by the fuel

^■ =! © boiler water flow + boiler inlet temperature + boiler outlet temperature Power delivered by the boiler

^■ =! © Power supplied by the fuel + Power delivered by the boiler Instantaneous efficiency of the boiler From a theoretical molecular composition of wood, we determine the mass of dry wood Mb _S in kg / mol, and the volumes comburivore dry VAS and dry fumigene VFS ©, that is to say the volume of air necessary stoichiometric combustion and the volume of fumes generated by such combustion, in the absence of water. These values are expressed for example in Nm ³ / mol of dry wood.

 The following calculations are performed per cycle.

 It can be considered that the oxygen content of the dry fumes (A) is directly the oxygen value measured by the dry oxygen probe, or that this rate is calculated by correcting the oxygen value measured by the dry probe. depending on the cooling temperature of the dryer, considering a gas saturated with moisture at this temperature and the pressure of the dryer, the pressure being measured or taken at a flat rate.

 From the oxygen content on dry fumes, the dry comburivore volume VAS and the dry smoke volume VFS, an excess of air (e),, expressed as a percentage by the formula:

A. VFS

 The value 4.77 corresponds to the number of moles of air per one mole of oxygen, that is to say by adding 3.77 moles of dinitrogen.

 Moreover, as indicated in step 13 of FIG. 5, the humidity of the flue gases Hf is determined from the measurement of the flow of water condensed in the flue gas drying device by cooling and condensation of their moisture, as described above in the description part of the invention and the correction of this value of the residual humidity of the fumes at the outlet of the drying device.

 From the excess air (e), the humidity of the fumes and the molar mass of dry wood, the humidity of the wood Hb is determined during the step 14 of FIG. 5. In fact, it is believed that the amount of water in the flue gas comes in part from the moisture originally contained in the moist wood. The moisture of the wood is defined by the formula:

_TT ^m H20

¾ VT ^~

m _H 2o + M _bs With ΠΠΗ20 the amount of water in kg / mol of wood.

 If the humidity of the fumes Hf is known, the humidity of the wood Hb can be calculated by the formulas:

 v

[in Nm ³ / mol of wood]

and

 with MH2O the molar mass of water in g / mol;

 PHI the water content of the combustion air, in moles of water per mole of dry air; y the hydrogen content of the wood, in mass fraction;

V _{m is} the molar volume under normal conditions of temperature and pressure, and is 0.0224 Nm ³ / mol.

 It is therefore considered that the moisture content of the fumes coming from the combustion of the hydrogen constituting the organic matter must be taken into account in the calculation of the humidity of the latter. The calculations also take into account the humidity of the combustion air, either by direct measurements of humidity and temperature at the inlet of the blowing means (3), or by meteorological data.

 From the moisture content of the wood, it is deduced in step 15 of Figure 5, the lower calorific value of wet wood (PCI) ®. This data is essential to appreciate the quality of a supply.

Using the measurement of the volume flow rate of fumes, as shown in step 16 of FIG. 5, relative to the wet smoke power and to the excess air (e), we deduce a mass flow rate of wet wood to Step 17 of Figure 5 ©. By multiplying it by the PCI determined in step 15, the heating power contributed by the fuel in step 18 of FIG. 5 ⁽ D.

The power supplied by the boiler can be evaluated for example by measuring a heat transfer fluid flow, a temperature of the fluid at the boiler inlet and a temperature at the outlet ©. By dividing this power by the As a result of the power supplied by the fuel, an instantaneous efficiency of the boiler in step 19 of FIG. 4 ® is deduced.

 It is important to note that all these calculations are done on ashless wood. To return to the corresponding values on raw wood (wet wood with ash), and to be able to compare the results with measurements made on fuel samples (example: humidity of the raw wood measured in the oven), it will be necessary to estimate the rate of ashes. The ash content can be measured by a destructive method: combustion at 550 ° C and measurement of the remaining mineral residue.

 It is possible to integrate in these calculations the measurement corrections that were previously detailed in the description part of the invention.

 In a variant of the method of the invention, which considers that the most reliable data is the power of the boiler on which the calculation of the incoming power is based, from the step of measuring the flue gas flow ©, the power provided by the organic matter is evaluated by adding the measured power of the boiler, that lost by the flue gases, that by thermal losses of the boiler and deducing that provided by the combustion air:

Combustible ^- Pumice Pfumées + Losses radiation - combustion air-

Thus the power lost in the smoke is evaluated from the measured flow rate of the fumes, their temperature and a heat capacity of the fumes estimated from the theoretical capacities of each of the components of the fumes and the composition of the fumes. The composition of the fumes is calculated from their excess air and the composition of the wood. It could also be measured by a gas analyzer for carbon dioxide, in addition to the moisture measurement, and possibly for nitrogen. The contributions by the combustion air are also evaluated from the heat capacity of the air and the temperature thereof and its flow rate calculated from the flue gas flow rate. The radiation losses of the boiler are not measured but taken at a fixed value.

 In another variant, when the power of the boiler is not available, it is estimated from step,, by the addition of the power provided by the organic material and that provided by the combustion air, and removing that lost by the fumes and that by heat losses of the boiler:

Pchaudière ^- Pcombustible Pair oxidant ^- Pfumées ^- Losses radiation The power supplied by the combustion air, that lost by the fumes and the thermal losses are evaluated in the same way as previously. The power provided by the organic matter is estimated from the measurement of the flue gas flow rate and the evaluation of the heating value from the moisture, as explained above.

The present invention provides a system for determining a moisture content of an organic material used as fuel in a boiler that is reliable, accurate and responsive. Said system being characterized by a principle of measuring the humidity of the fumes (in%) by a measurement of condensate flow extracted from the fumes in a condenser; which is based essentially on a specific assembly of the elements of the device of the invention for the continuous measurement of a very small condensate flow and in a pipe which is not in charge (0.5 to 30 ml / h), as well as the use of correction formulas to correct this measure (eg bucket flowmeter used on rain gauges). The present invention also makes it possible to implement a method of regulating the operation of a boiler for organic matter by determining its performance, which essentially relies on the above determination system, to arrive at the boiler performance, and the implementation of necessary corrections to obtain reliable and accurate measurements.

List of references

1. Patent FR 3020139

 5

Claims

1) Method for determining a moisture content of an organic material used as a fuel in a boiler having a duct 5 fumes to evacuate the combustion fumes of the organic material in the boiler, characterized in that carries a sample of fumes in the flue gas duct, the humidity is determined in the fumes taken by measuring the flow rate of the flue gases. condensate generated during drying by cooling said fumes in a condenser, and the moisture content of the organic material is determined as a function of the moisture content of the fumes and the oxygen content in the fumes taken at the same place and after drying said fumes in a condenser. 2) The method of claim 1, said method comprising: A) measuring the flow rate of the condensates generated in the condenser of the collected fumes arriving directly in the condenser, by cooling and condensation of their moisture;  b) the measurement of the flow of dry smoke downstream of the condenser;  c) measuring the gross moisture content of the fumes from measurements 0 of steps a) and b);  d) measuring the actual humidity of the fumes from the measurement of step c), to which is added the value of residual moisture remaining in the flue gas leaving the condenser and evaluated from the temperature and the pressure in the condenser. 5 3) Process according to claim 2, wherein the condensate flow rate of step a) after condenser condensate extraction, for example by a peristaltic pump, by a micro-flow meter, or by a dynamic mass measurement of the mass, is measured. a container that collects these condensates and 0 self-empty when full. 4) Method according to one of claims 1 to 3, wherein continuously measuring the pressure of the condenser by a pressure sensor at the outlet of the condenser. 5) Process according to claim 4, wherein the dry fumes are sucked by a pump placed downstream of the pressure probe. 6) Process according to claim 5, wherein a constant flow of flue gas is maintained by a flow control member located downstream of the suction pump. 7) Method according to claim 6, wherein the flue gas flow rate is measured by a measuring member located downstream of the flow control member. 8) Process according to claim 7, wherein the water content of the fumes is measured by a computer, from the flow of condensates and the flow rate of dry fumes. 9) Method according to any one of claims 1 to 8, further comprising the following corrections of measurements:  - the absolute humidity of the combustion air, calculated from the temperature and the relative humidity of the combustion air;  the amount of water supplied by the reagent and the reaction products in the case of treatment to reduce the nitrogen oxides of the fumes with solutions using urea or ammonia. 10) Device for determining a moisture content of an organic material used as a fuel in a boiler comprising a flue gas duct for evacuating the flue gases from the organic material in the boiler, said device being characterized in that it comprises means for taking smoke from the flue, and measuring means able to determine a moisture content of the organic material as a function of the smoke moisture content measured in the flue gases sampled and the rate of oxygen of the fumes measured in the fumes taken from the same place and after drying said fumes in a condenser, said measuring means implementing a method according to one of the preceding claims. 1 1) Device according to claim 10, wherein the measuring means comprise:  an oxygen sensor;  - a smoke condenser;  a condensate extraction system of the condenser, for example a peristaltic pump;  - a micro-flow meter, or a dynamic weighing system;  a pressure probe;  - a suction pump;  a regulator of the flue gas flow rate;  - a device for measuring the flow of fumes;  a probe for measuring the relative humidity and the temperature of the combustion air;  a device for measuring injected reagent flow rates in the case of NOx treatment of the fumes; and  - a calculator of the water content of the fumes. 12) A method for determining the performance of a boiler for an organic material comprising a flue gas duct for evacuating combustion flue gases from the organic material in the boiler, said method comprising: a) the determination of the moisture content in the flue gases; combustion taken from the flue gas duct and the oxygen content of the flue gas sampled at the same location and after drying of said flue gas in a condenser, implementing a method according to one of claims 1 to 9;  b) determining the moisture content of the organic material used as fuel from the measurements of step a); c) determining the lower heating value (LHV) of the organic material used as fuel from the measurement of step b); d) the determination of the volumetric flow rate of the flue gases taken from the flue gas duct; and  e) determining the mass flow rate of organic material used as fuel from the measurement of step d);  f) determining the power provided by the organic material used as fuel from the measurements of steps c) and e);  (g) the determination of the power delivered by the boiler;  h) determining the instantaneous efficiency of the boiler from the measurements of steps f) and g). The method of claim 12, said method further comprising the following measurement corrections:  - the absolute humidity of the combustion air, calculated from the temperature and the relative humidity of the combustion air;  the amount of water supplied by the reagent and the reaction products in the case of treatment to reduce the nitrogen oxides of the fumes with solutions using urea or ammonia.