An open type solid fuel calorific value measuring device and method

Abstract

The application discloses an open type solid fuel calorific value measuring device, which comprises a laser ignition unit for igniting solid fuel in a calorific value measuring cavity, the calorific value measuring cavity comprising an inner cylinder and an outer cylinder from inside to outside in sequence to provide a combustion chamber, a sample loading structure for feeding solid fuel into the combustion chamber of the calorific value measuring cavity, and a data processing unit for collecting temperature and oxygen flow data of solid fuel combustion and calculating the calorific value of the solid fuel. The application also discloses a measuring method, which comprises the following steps: feeding a solid fuel sample into the calorific value measuring cavity through a crucible; introducing oxygen to the upper surface of the crucible; irradiating a laser beam to the surface of the solid fuel for ignition; collecting the inlet air temperature, outlet air temperature, inner cylinder temperature, outer cylinder temperature, crucible tray temperature and oxygen flow data, and calculating the calorific value of the solid fuel. The device and method avoid the limitation of high pressure environment of an oxygen bomb and reduce the requirement for external environment, and the accuracy of calorific value measurement is relatively high.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of heat release measurement, and particularly relates to an open type solid fuel heat release measurement device and method. BACKGROUND

[0002] The heat release of solid fuel such as straw, peanut shell, rice husk, charcoal, coal, feed and building material is the most important indicator for its use as energy.

[0003] When measuring the heat release of solid fuel in the prior art, an oxygen bomb calorimeter is usually used. The sample is weighed, a ignition wire is bound, and then put into an oxygen bomb. Excessive high pressure oxygen is introduced into the oxygen bomb. Then the sample is ignited by the ignition wire and cotton thread. The sample releases heat during combustion. The heat release of the sample is calculated by measuring the temperature rise of water around the oxygen bomb. The measurement principle of the oxygen bomb calorimeter is simple, but the oxygen bomb is in a high pressure environment, which requires a high operating environment, and is generally performed in a laboratory.

[0004] At present, many oxygen bomb calorimeters for measuring heat release have been improved. For example, the patent with publication number CN109270119A discloses a coal powder heat release measurement system. The measurement realizes online measurement, but when the gas flows into the combustion chamber from the top, it affects the dispersion of the coal powder. In addition, when calculating the energy dissipation of the environment outside the cylinder, it is difficult to determine the convective heat transfer coefficient and the radiation heat transfer parameter between the outer cylinder and the environment. Moreover, when the environment changes, the heat release error increases, so the calculation requires a high external environment.

[0005] At the same time, the traditional oxygen bomb calorimeter uses an ignition wire for ignition, which needs to be replaced each time, and the operation is cumbersome. Laser has the advantages of directionality, non-contact, high power density and easy control. Laser ignition avoids direct contact with the surface of solid fuel and can ignite the sample in a very short time. For example, the Chinese patent with publication number CN113189140A discloses a heat release detection method and automatic detection system based on wall temperature monitoring oxygen bomb device. The method comprises the following steps: step 1. Put the sample into the tank body; step 2. Open the inlet valve and outlet valve, introduce oxygen, and purge for a period of time; step 3. Close the outlet valve to charge oxygen at a certain speed until the pressure in the tank body reaches a predetermined value, and close the inlet valve; step 4. Use multiple room temperature sensors to obtain the temperature of the measuring point and take the arithmetic average output as the room temperature T r ; use multiple tank temperature sensors to obtain the temperature of the measuring point and take the arithmetic average output as the tank temperature T p ; use multiple combustion temperature sensors to obtain the temperature of the measuring point and take the arithmetic average output as the real-time combustion temperature T c ; step 5. Turn on the laser light source to emit laser light to ignite the sample; step 6. Wait for the combustion temperature T cWhen the temperature drops and is lower than the highest combustion temperature by a certain value, a combustion temperature change curve is generated, and the heat generation is calculated; step 7, opening the gas outlet valve, and exhausting to normal pressure; step 8, opening the gas inlet valve, and purging until the tank temperature recovers to close to T p .

[0006] Therefore, how to reduce the environmental requirements and ensure the accuracy of the heat generation measurement method is the research focus in the field. SUMMARY

[0007] The purpose of the present application is to provide an open type solid heat generation measurement device and method, which avoids the restriction of high pressure environment of oxygen bomb and reduces the requirement for external environment, and the heat generation measurement has high accuracy.

[0008] The present application provides the following technical solutions:

[0009] An open type solid fuel heat generation measurement device, the measurement device comprises:

[0010] A laser ignition unit for directional and rapid ignition of solid fuel in a heat generation measurement cavity;

[0011] A heat generation measurement cavity comprising an inner cylinder and an outer cylinder from inside to outside, which constitutes a combustion chamber for solid fuel combustion;

[0012] A sample loading structure for feeding solid fuel into the combustion chamber of the heat generation measurement cavity;

[0013] A data processing unit for collecting temperature and oxygen flow data of solid fuel combustion and calculating the heat generation of solid fuel.

[0014] The laser ignition unit comprises a laser and a beam expander, and the laser beam emitted by the laser is enlarged in diameter by the beam expander and then irradiates the surface of the solid fuel.

[0015] Further, a high-power laser is used to enlarge the diameter of the laser beam through the beam expander, so that the laser can completely cover the surface of the solid fuel, and after the surface temperature of the solid fuel reaches 800-1200 degrees within 10 seconds, the laser stops irradiating after the solid fuel is ignited.

[0016] The heat generation measurement cavity comprises an upper wall, an upper connecting plate for connecting the inner cylinder and the outer cylinder, a combustion chamber composed of the inner cylinder and the outer cylinder, a lower connecting plate for connecting the inner cylinder and the outer cylinder, and a lower wall from top to bottom; the upper wall is provided with a first air inlet hole, the upper connecting plate is provided with a second air inlet hole, and the inner cylinder is provided with a third air inlet hole, and oxygen enters the combustion chamber through the first air inlet hole, the second air inlet hole and the third air inlet hole in sequence; the lower connecting plate is provided with a first air outlet hole, and the lower wall is provided with a second air outlet hole, and the gas after combustion of the solid fuel is discharged from the combustion chamber through the first air outlet hole and the second air outlet hole.

[0017] Further, the upper connecting plate is uniformly provided with a plurality of air holes as second air inlet holes, and the number of air holes is greater than or equal to 2; the lower connecting plate is uniformly provided with a plurality of air holes as first air outlet holes around the circumference, and the number of air holes is greater than or equal to 2; the air holes of the upper connecting plate and the lower connecting plate correspond to the inner-outer cylinder interlayer and the combustion chamber in the inner cylinder respectively; a plurality of air holes are uniformly arranged in the middle position of the inner cylinder as third air inlet holes, and the number of air holes is greater than or equal to 2.

[0018] A plurality of air holes are arranged in the upper connecting plate, the lower connecting plate and the inner cylinder, and the number of air holes is greater than or equal to 2, so that oxygen can uniformly enter and exit the combustion chamber

[0019] The sample loading structure sequentially comprises a crucible, a crucible tray, a connecting column and a telescopic push rod from top to bottom, and the solid fuel is placed on the crucible.

[0020] Specifically, the crucible loaded with the solid combustion sample is sent into the heat release measurement cavity, and is separated from the heat release measurement cavity after the measurement is completed, and the ash is cleaned for the next measurement.

[0021] Further, the placement position of the crucible in the inner cylinder is that the upper surface of the crucible is below or tangent to the third air inlet hole of the inner cylinder.

[0022] Further, temperature sensors are arranged at the inlet and outlet of the heat release measurement cavity, the wall surface of the inner cylinder, the wall surface of the outer cylinder and the crucible tray, and an oxygen flow sensor is arranged at the oxygen inlet.

[0023] Further, the thickness of the interlayer between the inner cylinder and the outer cylinder is greater than or equal to 2 mm and less than or equal to 20 mm, and the thickness of the inner cylinder and the outer cylinder is less than or equal to 10 mm.

[0024] Further, the inner cylinder, the outer cylinder, the crucible and the crucible tray are made of a material with a thermal conductivity greater than 40 W / (m·K), including but not limited to aluminum, iron, copper and alloys thereof; the upper wall surface, the upper connecting plate, the lower connecting plate, the lower wall surface and the connecting column are made of a material with a thermal conductivity less than 2 W / (m·K), including but not limited to polytetrafluoroethylene and polyimide.

[0025] The selection of the materials of the inner cylinder and the outer cylinder is to insulate the connection between the inner cylinder and the outer cylinder and to build a more accurate heat release calculation model; the selection of the material of the connecting column is to dissipate the heat of the wall surface to the outside through the bottom connecting column.

[0026] The application also provides a measurement method using the above-mentioned open-type solid fuel heat release measurement device, and the measurement method comprises the following steps:

[0027] S1, a certain mass of solid fuel sample is weighed, the crucible loaded with the sample is placed on the crucible tray, and the telescopic push rod is used to send the crucible into the heat quantity measurement cavity;

[0028] S2, oxygen is introduced, and the laser beam emitted by the laser passes through the first gas inlet hole of the upper connecting plate and the second gas inlet hole of the inner cylinder to reach the upper surface of the crucible; the laser beam emitted by the laser passes through the beam expander to enlarge the diameter and irradiates the surface of the solid fuel; after the sample is ignited, the irradiation is stopped;

[0029] S3, the inlet temperature, outlet temperature, inner cylinder temperature, outer cylinder temperature, crucible tray temperature, and oxygen flow rate data at the inlet are collected, and the heat quantity of the solid fuel is calculated.

[0030] Further, in step S1, the telescopic push rod sends the crucible loaded with the sample into the heat quantity measurement cavity, and the position is that the upper surface of the crucible is below or tangent to the inner cylinder air hole, and the oxygen can directly reach the upper surface of the crucible through the inner cylinder air hole, which promotes the combustion of the solid fuel and reduces the amount of oxygen used.

[0031] Further, in step S3, the time resolution of the temperature data and the oxygen flow rate data should be less than 10s, that is, each measured temperature data and oxygen flow rate data needs to be measured at most every 10s.

[0032] The calculation method of the solid fuel is as follows:

[0033] Q=A+B+C+D+E

[0034] Wherein, Q is the heat quantity of the solid fuel, A is the energy carried away by the gas, B is the energy transferred from the inner cylinder to the outer cylinder, C is the increased internal energy of the crucible tray, D is the increased internal energy of the inner cylinder, and E is the increased internal energy of the outer cylinder; which are calculated by the following formulas

[0035]

[0036]

[0037]

[0038]

[0039]

[0040] In the above, except for the temperature T, the time t and the oxygen flow rate q oxy The rest are constants, wherein t0 is the time when the laser is ignited, and t is the time when the measurement is completed. Wherein, ρ oxy is the density of oxygen, C P is the specific heat capacity of oxygen at constant pressure, λ is the thermal conductivity of the interlayer, l is the length of the interlayer, ρ fin , C finV fin It refers to the density, specific heat capacity, and volume of the crucible tray; ρ inshell C inshell V inshell It refers to the density, specific heat capacity, and volume of the inner cylinder; ρ outshell C outshell V outshell It refers to the density, specific heat capacity, and volume of the outer cylinder.

[0041] The energy of each part is:

[0042]

[0043]

[0044]

[0045]

[0046]

[0047] Among them, the coefficients K of each part A K B K C K D K E The fixed parameters of the calorific value measurement chamber should be obtained through prior calibration.

[0048] In the formula, t0 is the moment when the laser ignites the sample, at which point the laser stops irradiating; t is the moment when the measurement of the sample's heat output ends, which is the moment after the sample has completely burned, and the measurement can continue for a period of time.

[0049] The preliminary calibration used combustion heat standard materials, including but not limited to benzoic acid, and K was obtained by fitting data from multiple previous experiments using the least squares method. A K B K C K D K E After fitting the coefficient K A K B K C K D K E Afterwards, further verification is still needed. Once the verification confirms that the error in calorific value is within a reasonable range, it indicates that the coefficient value K of the calorific value calculation fitting model is correct. A K B K C K D K E feasible.

[0050] Furthermore, the calculation method for the solid fuel is as follows:

[0051]

[0052] wherein, T out , T in , T inshell , T inshell are the real-time outlet temperature, inlet temperature, outer cylinder wall surface temperature, inner cylinder wall surface temperature, is the temperature of the crucible tray at time t and time t0, is the temperature of the inner cylinder wall surface at time t and time t0, is the temperature of the inner cylinder wall surface at time t and time t0, t0 is the time of laser ignition, t is the end of measurement time, K A , K B , K C , K D , K E is a fixed parameter belonging to the heat quantity measurement cavity, q oxy is the oxygen flow.

[0053] Therefore, during the measurement, by measuring the temperature data and oxygen flow data of each measuring point, the heat quantity of the pulverized coal can be obtained.

[0054] The measurement of the heat quantity of the sample is realized by an open type solid fuel heat quantity measurement device, the high pressure environment of the oxygen bomb is avoided, the automation level is improved by using laser ignition, and the calculation accuracy is improved based on the open type solid calculation model.

[0055] Compared with the prior art, the open type normal pressure measurement method provided by the present application avoids the high pressure environment during the measurement of the traditional calorimeter, and the heat quantity calculation model of the method is constructed, thereby improving the heat quantity measurement precision. BRIEF DESCRIPTION OF DRAWINGS

[0056] Figure 1 is a sectional view of the open type solid fuel heat quantity measurement device in the embodiment.

[0057] wherein, 1, laser; 2, beam expander; 3, laser beam; 4, heat quantity measurement laser penetration lens; 5, first air inlet hole; 6, second air inlet hole; 7, third air inlet hole; 8, inner cylinder; 9, outer cylinder; 10, outlet space; 11, first outlet hole; 12, first outlet hole; 13, rubber ring; 14, crucible; 15, crucible tray; 16, connecting carrier; 17, telescopic push rod; 18, upper wall surface; 19, upper connecting plate; 20, air inlet space; 21, combustion chamber; 22, interlayer; 23, lower connecting plate; 24, lower wall surface. DETAILED DESCRIPTION

[0058] The measuring device and method of the present application will be described in detail below with reference to the accompanying drawings.

[0059] As shown in FIG. 1, the open-type solid fuel calorific value measuring device provided by the present embodiment comprises:

[0060] The laser ignition unit comprises a laser 1 and a beam expander 2. The laser beam 3 emitted by the laser 1 is enlarged in diameter by the beam expander 2 and then irradiated onto the surface of the solid fuel through the calorific value measuring laser penetration lens 4.

[0061] The heat measurement cavity comprises an inner cylinder 8 and an outer cylinder 9 from inside to outside, which serve as a combustion chamber for the combustion of the solid fuel. Specifically, the heat measurement cavity comprises an upper wall 18, an upper connecting plate 19 for connecting the inner cylinder 8 and the outer cylinder 9, a combustion chamber 21 formed by the inner cylinder and the outer cylinder, a lower connecting plate 23 for connecting the inner cylinder 8 and the outer cylinder 9, and a lower wall 24 from top to bottom. The upper wall 18 is provided with a first air inlet hole 5, the upper connecting plate 19 is provided with a second air inlet hole 6, and the inner cylinder 8 is provided with a third air inlet hole 7. Oxygen enters the combustion chamber 21 through the first air inlet hole 5, the second air inlet hole 6 and the third air inlet hole 7 in sequence. The lower connecting plate 23 is provided with a first air outlet hole 12, and the lower wall 24 is provided with a second air outlet hole 11. The gas after the combustion of the solid fuel is discharged from the combustion chamber 21 through the first air outlet hole 12 and the second air outlet hole 13.

[0062] Among them, temperature sensors are arranged on the first air inlet hole 5, the second air outlet hole 11, the wall surface of the inner cylinder 8 and the wall surface of the outer cylinder 9, respectively, and an oxygen flow sensor is arranged in front of the first air inlet hole 5.

[0063] Among them, the lower connecting plate 23 and the lower wall 24 form an air outlet space 10 for discharging the gas after combustion from the combustion chamber, the upper wall 18 and the upper connecting plate 19 form an air inlet space for the oxygen to enter through the air inlet hole, and the inner cylinder 8 and the outer cylinder 9 form a sandwich layer 22.

[0064] Among them, the second air inlet hole 6 is uniformly arranged along the circumferential direction of the upper connecting plate 19, which facilitates the uniform flow of oxygen into the sandwich layer 22, and the number of the second air inlet hole 6 is at least 2.

[0065] Among them, the third air inlet hole 7 is uniformly arranged along the middle position of the inner cylinder 8, and the number of the third air inlet hole 7 is at least 2.

[0066] Among them, the first air outlet hole 12 is uniformly arranged along the circumferential direction of the lower connecting plate 23, which facilitates the uniform flow of flue gas, and the number of the first air outlet hole 12 is at least 2.

[0067] The sample loading structure sends the solid fuel into the combustion chamber 21 of the heat release measurement cavity. From top to bottom, it is the crucible 14 for loading solid fuel, the crucible tray 15, the connecting column 16 connecting the crucible tray 15 and the telescopic push rod 17, and the telescopic push rod 17. When oxygen flows in from the third air inlet hole 7, it directly reaches the upper surface of the crucible 14.

[0068] The temperature sensor is arranged at the crucible tray 15.

[0069] The rubber ring 10 is arranged between the connecting column 16 and the gas outlet space 10 to enhance the sealing.

[0070] The data processing unit collects the temperature and oxygen flow data of the solid fuel combustion and calculates the heat release of the solid fuel.

[0071] The heat release measurement method using the above open-type solid fuel heat release measurement device includes the following steps:

[0072] First, the heat release measurement cavity is calibrated (pre-calibration) using a combustion heat standard substance (such as heat release): multiple different experiments are performed on the heat release measurement cavity, and multiple sets of temperature data corresponding to the heat release are measured. The least squares method is used for fitting to obtain the inherent parameters K A , K B , K C , K D , K E After the error is verified within a certain range, the subsequent heat release measurement can calculate the heat release of the sample according to the temperature data and oxygen flow based on the correlation formula.

[0073] The specific measurement process is as follows:

[0074] Step one, weigh the solid fuel sample, place the crucible 14 loaded with the sample on the crucible tray 15, and send it into the combustion chamber 21 in the heat release measurement cavity through the telescopic push rod 17.

[0075] Step two, introduce oxygen, and collect the temperature sensor data and oxygen flow data of each measurement point in real time; after the gas in the cavity is exhausted, turn on the laser and ignite the sample. The laser stops irradiation after the sample is ignited; oxygen is introduced and temperature and oxygen flow data are collected throughout the process until the measurement is completed.

[0076] The flow of gas is as follows: Figure 1As shown, oxygen reaches the air inlet space 20 through the first air inlet hole 5, enters the interlayer 22 uniformly through the second air inlet hole 6, and then enters the combustion chamber 21 through the third air inlet hole 7, which can directly reach the upper surface of the crucible 14. After the sample is burned, the oxygen and the flue gas generated by combustion are mixed, enter the air outlet space 10 through the first air outlet hole 12, and then are discharged from the heat generation measurement cavity through the second air outlet hole 11. The gas flows through the interlayer 22 of the inner cylinder 8 and the outer cylinder 9, which helps to take away the heat of the heat generation measurement cavity and is conducive to the stable and sustainable operation of the heat generation measurement cavity. Oxygen can directly reach the upper surface of the sample crucible 14 through the third air inlet hole 7, which helps to reduce the oxygen consumption.

[0077] Step three, according to the temperature data and oxygen flow data collected at each measuring point, the heat generation of the sample is calculated according to the heat generation correlation formula, and finally divided by the sample quality, that is, the heat generation of the sample is obtained.

[0078] Among them, the calculation method of heat generation is:

[0079]

[0080] Among them, T out , T in , T outshell , T inshell are the real-time outlet temperature, inlet temperature, outer cylinder wall temperature, inner cylinder wall temperature, is the temperature of the crucible tray at time t and time t0, is the temperature of the inner cylinder wall at time t and time t0, is the temperature of the inner cylinder wall at time t and time t0, t0 is the time of laser ignition, t is the end of measurement, K A , K B , K C , K D , K E are fixed parameters of the heat generation measurement cavity, q oxy is the oxygen flow.

Claims

1. An open-type solid fuel calorific value measuring device, characterized in that, The measuring device comprises: a laser ignition unit for directing rapid ignition of the solid fuel in the heat release measuring cavity; a heat release measuring cavity comprising, from inside to outside, an inner cylinder and an outer cylinder, and constituting a combustion chamber for combustion of the solid fuel; the heat release measuring cavity comprises, from top to bottom, an upper wall, an upper connecting plate for connecting the inner cylinder and the outer cylinder, a combustion chamber constituted by the inner cylinder and the outer cylinder, a lower connecting plate for connecting the inner cylinder and the outer cylinder, and a lower wall; the upper wall is provided with a first air inlet hole, the upper connecting plate is provided with a second air inlet hole, and the inner cylinder is provided with a third air inlet hole, and oxygen enters the combustion chamber through the first air inlet hole, the second air inlet hole and the third air inlet hole in sequence; the lower connecting plate is provided with a first air outlet hole, and the lower wall is provided with a second air outlet hole, and the gas after combustion of the solid fuel is discharged from the combustion chamber through the first air outlet hole and the second air outlet hole; wherein the lower connecting plate and the lower wall constitute an air outlet space for discharging the gas after combustion from the combustion chamber, the upper wall and the upper connecting plate constitute an air inlet space for the oxygen to enter through the first air inlet hole, and the inner cylinder and the outer cylinder form a sandwich layer, the second air inlet holes are uniformly arranged along the circumferential direction of the upper connecting plate, facilitating uniform flow of oxygen into the sandwich layer, and the third air inlet holes are uniformly arranged along the middle position of the inner cylinder; a sample loading structure for feeding the solid fuel into the combustion chamber of the heat release measuring cavity; the sample loading structure comprises, from top to bottom, a crucible, a crucible tray, a connecting column and a telescopic push rod, and the solid fuel is placed on the crucible; the connecting column is made of a material with a thermal conductivity less than 2 W / (m·K); and the placement position of the crucible in the inner cylinder is that the upper surface of the crucible is below the third air inlet hole of the inner cylinder or is tangent to the third air inlet hole of the inner cylinder; a data processing unit for collecting temperature and oxygen flow data of combustion of the solid fuel and calculating the heat release of the solid fuel; the calculation method of the heat release of the solid fuel is: Q=A+B+C+D+E wherein Q is the heat release of the solid fuel, A is the energy carried away by the gas, B is the energy transferred from the inner cylinder to the outer cylinder, C is the internal energy increased by the crucible tray, D is the internal energy increased by the inner cylinder, and E is the internal energy increased by the outer cylinder; and specifically: wherein, , , , are the real-time outlet temperature, inlet temperature, outer cylinder wall surface temperature, inner cylinder wall surface temperature, respectively, , are the temperatures of the crucible tray at time t and time , , are the temperatures of the inner cylinder wall surface at time t and time , , are the temperatures of the outer cylinder wall surface at time t and time , is the time of laser ignition, t is the time of measurement end, , , , , are fixed parameters belonging to the heat generation measurement cavity, is the oxygen flow rate.

2. The open-type solid fuel heat quantity measuring device according to claim 1, wherein the laser ignition unit comprises a laser and a beam expander, and the laser beam emitted by the laser is enlarged in diameter by the beam expander and then irradiates the surface of the solid fuel.

3. The open-type solid fuel heat quantity measuring device according to claim 1, wherein temperature sensors are arranged at the inlet and outlet of the heat release measuring cavity, the wall of the inner cylinder, the wall of the outer cylinder and the crucible tray, and an oxygen flow sensor is arranged at the oxygen inlet.

4. The open-type solid fuel heat quantity measuring device according to claim 1, wherein the thickness of the sandwich layer between the inner cylinder and the outer cylinder is greater than or equal to 2 mm and less than or equal to 20 mm, and the thickness of the inner cylinder and the outer cylinder is less than or equal to 10 mm.

5. A measuring method using the open-type solid fuel calorimeter according to any one of claims 1 to 4, characterized by, the measuring method comprises the following steps: S1, weighing a certain mass of solid fuel sample, placing the crucible loaded with the sample on the crucible tray, and feeding the sample into the heat release measuring cavity through the telescopic push rod; S2, oxygen is introduced and enters the upper surface of the crucible through the first air inlet hole of the upper wall, the second air inlet hole of the upper connecting plate and the third air inlet hole of the inner cylinder in sequence; the laser beam emitted by the laser is enlarged in diameter by the beam expander and then irradiates the surface of the solid fuel, and the irradiation is stopped after the sample is ignited; S3, collect the inlet temperature, outlet temperature, inner cylinder temperature, outer cylinder temperature, crucible tray temperature, and oxygen flow data at the inlet, and calculate the heat value of the solid fuel.

Images