Scales for weighing a sample while interacting with at least one process gas

Abstract

The invention relates to scales (2) for weighing a sample (4) while interacting with at least one process gas (6), the scales (2) having at least one sample holder (8), which is designed to record a force exerted by the weight of a sample container (10) with the sample (4), having at least one process gas line (12), which is designed to supply the process gas (6) to the sample holder (8), and having at least one measuring unit (14) for measuring the weight or a change in weight acting on the sample holder (8), wherein the sample holder (8) has at least one outlet opening (16) for the process gas (6), the opening being arranged so as to conduct the process gas (6) to a sample container base (18).

Description

[0001] Balance for weighing a sample in interaction with at least one process gas

[0002] The invention relates to a balance for weighing a sample under interaction with at least one process gas, wherein the balance has (a) at least one sample holder configured to absorb a weight of a sample container containing the sample, (b) at least one process gas line configured to supply the process gas to the sample holder, and (c) at least one measuring unit for measuring the weight or a change in weight acting on the sample holder, wherein the sample holder can have at least one outlet opening for the process gas, which is arranged to conduct the process gas to a sample container base. Furthermore, the invention relates to a weighing system comprising such a balance and a sample container.

[0003] Precise balances for weighing a sample in interaction with at least one process gas are required in research, development, and industry, for example, for the investigation of chemical reactions. For example, a sample is repeatedly weighed during a chemical reaction with the process gas to record a time course of the weight change. This allows the reaction rate to be determined.

[0004] In many cases, the respective chemical reaction depends on the temperature or a specified temperature range must be maintained, for example to activate the chemical reaction. It is therefore desirable that the sample and / or the process gas can be temperature-controlled. It is also desirable that the temperature of the sample and / or the amount of heat released or absorbed by the sample can be recorded, for example in order to determine a temperature-dependent change in weight of the sample and / or to perform calorimetry. Balances exist for weighing a sample in interaction with at least one process gas, in which the process gas is fed from the side of the sample, for example from an inflow side in an approximately horizontal direction. In these balances, the process gas flows above the sample and is discharged on a side of the sample horizontally opposite the inflow side.It has been shown that the reaction rates determined with such scales do not agree well with the reaction rates in larger systems.

[0005] To solve this problem and accurately measure weight changes during interaction with the process gas, a complete reaction chamber with a sample placed inside is weighed during the reaction. However, this has the disadvantage that a high total weight must be weighed, resulting in a relatively high absolute measurement uncertainty.

[0006] From CN 211 626 636 U and CN 112 729 512 A a scale for molten steel is known, on which a steel ladle with the liquefied steel can be placed and weighed, whereby the scale has a seal against argon gas, which is fed into the liquid steel from below as a process gas.

[0007] It is therefore the object of the present invention to provide a scale that reduces the disadvantages of the prior art.

[0008] The object is achieved according to the invention by a scale having the features of claim 1.

[0009] This advantageously allows a more realistic measurement of the reaction rate of chemical reactions, since the reaction rate measurable with the balance better matches the reaction rate in a real reactor.

[0010] In addition, the balance advantageously usually has a lower measurement uncertainty, since the weight force acting on the measuring unit can be selected to be lower. In the context of this description, the sample is understood in particular to be an object to be examined that comprises at least one solid and / or a liquid and that exerts a weight force. The sample is, for example, suitable for entering into a chemical reaction with the process gas. The sample is, for example, a pure substance or a mixture of at least two components and is, for example, suitable for the at least two components to enter into a chemical reaction with each other, in particular by interacting with the process gas.

[0011] The sample is preferably arranged in a sample container, which in turn is preferably placed on the sample holder. Thus, the weight of the sample acts on the sample holder via the sample container.

[0012] The balance has at least one sample holder. The sample holder is designed to absorb the weight of the sample. For example, the sample exerts the weight on the sample holder indirectly via the sample container in which the sample is placed. In the context of this description, the sample holder is, in particular, a sample container holder. The latter means that, during operation, the weight of the sample container with the sample acts on the sample holder. The sample container is not part of the balance. The combination of balance and sample container is referred to as a weighing system.

[0013] One advantage is that the sample container and / or sample holder are removable. This allows the balance to be flexibly adapted to different samples and is easy to clean and maintain.

[0014] For example, the sample container stands on the sample holder. The sample holder is, for example, a sample plate or a tube attachment that can be placed on the process gas line. The sample container is, for example, a crucible. The sample container has a sample container base. The sample container base faces the sample holder and usually touches the sample holder when the sample container stands on the sample holder. The sample holder has, for example, a round, particularly circular, cross-sectional base on which the sample holder stands. Alternatively, other base shapes are possible, for example, square.

[0015] The process gas is understood in particular to be a gas that initiates or promotes at least one specific desired chemical reaction in the sample or inhibits or prevents a specific undesired chemical reaction in the sample.

[0016] Examples of process gases include air, hydrogen, ethylene, ethyne, carbon monoxide, oxygen, ozone, nitrogen, helium, argon, xenon, neon, krypton, carbon dioxide, or mixtures thereof, as well as other gases. The process gas serves, for example, to promote or inhibit an oxidation, particularly combustion, reduction, or other chemical reaction, so that the weight change during the chemical reaction can be measured.

[0017] A scale is a device for measuring a weight, change in weight, mass, or change in mass. For the purposes of this description, measuring a weight also includes measuring a change in weight, and vice versa.

[0018] The scale has at least one measuring unit, which is particularly designed to detect the weight force or change in weight force of the sample, preferably indirectly by measuring the weight force or change in weight force of the sample holder. The measuring unit has, for example, at least one electrical, electromagnetic, and / or optical sensor.

[0019] For example, the measuring unit is designed to hold the sample holder in a position by energizing an electromagnet that interacts with a second magnet, and to determine the weight force from the necessary electrical compensation current.

[0020] The balance has at least one process gas line designed to supply the process gas to the sample receptacle. In other words, the process gas line guides the process gas to the sample receptacle, preferably to a base of the sample receptacle. The sample receptacle has at least one outlet opening for the process gas, so that the process gas is directed to a sample container base when the sample container is positioned on the sample receptacle. In other words, the process gas is directed from the process gas line through the outlet opening in the sample receptacle to the sample container base.

[0021] The number of outlet openings on an upper side of the sample holder facing the sample container or the sample is preferably at least two, preferably at least four, preferably at least seven, preferably at least ten.

[0022] Preferably, the outlet openings are evenly distributed over the surface of the sample holder, at least over a portion of the surface, in particular a circular surface, which is designed to receive the sample container. "Evenly" refers in particular to the fact that, for the majority of the openings, the center point is such that the distance to the directly adjacent openings differs by no more than 30% from the average distance between adjacent openings.

[0023] The outlet openings have a respective opening surface per individual outlet opening of preferably at least 0.001 mm 2 , preferably at least 0.01 mm 2 , preferably a maximum of 5 mm 2 , preferably maximum 2.5 mm 2 , preferably maximum 1.5 mm 2 .

[0024] The process gas line is preferably connected to the sample holder, preferably to the bottom of the sample holder, preferably in such a way that all of the process gas flowing out of the process gas line flows into the outlet openings. In particular, preferably no process gas flows past the sample holder. The process gas line is, for example, at least in sections, a hose or pipe, for example with an internal diameter of a maximum of 2 cm, preferably a maximum of 1 cm, for example a minimum of 0.5 mm, preferably a minimum of 1 mm. The process gas can preferably flow through the sample. This means that the process gas flows through the sample, in particular that at least 60%, in particular at least 70%, preferably at least 80% of the sample surface comes into contact with the process gas along a cross-section of the sample orthogonal to the gas flow direction.

[0025] Preferably, the outlet openings are designed so that the process gas does not flow over the sample. In other words, the process gas flow is not horizontal, whereby an angular deviation of ±20°, in particular ±15°, in particular ±10° is tolerable. This allows a chemical reaction between the sample and the process gas to be investigated more reliably and precisely, and the measurement errors of the balance are lower than with conventional balances with process gas flow over the sample.

[0026] Preferably, the scale has a weighing beam mounted on a weighing beam pivot point. Preferably, the sample holder is connected to the measuring unit via the weighing beam, so that a change in the sample's weight can be measured by the measuring unit.

[0027] This advantageously gives the scale a low relative measurement uncertainty, since the relative measurement uncertainty of load beams can be reduced, for example, by increasing the beam length. Furthermore, load beams are comparatively lightweight and can be tared with high precision.

[0028] Preferably, the balance has a balancing unit for balancing a weight force acting on the sample holder.

[0029] Balancing is understood in particular to mean that the weight force acting on the measuring unit is smaller after baling than before. Preferably, a residual weight force of at most 15% of the uncompensated weight force, preferably a maximum of 10%, preferably a maximum of 5%, or an absolute residual weight of the weight force of a maximum of 15 g, preferably a maximum of 5 g, in particular a maximum of 1 g, acts on the measuring unit. In the context of the present description, a weighing beam is understood in particular to mean a horizontal beam. The weighing beam is in particular movably mounted on the pivot point, so that there is a beam section on each side of the pivot point. The weighing beam is in particular designed such that the weight force of the sample acts on a first beam section, so that the first beam section is displaced downwards and such that the measuring unit is arranged on the second beam section.

[0030] The second beam section has its own weight and preferably has an additional counterweight. The balancing unit is preferably arranged on the second beam section and / or connected to it, at least indirectly. The balancing unit is particularly designed to balance or compensate for the weight force acting on the weighing beam, in particular on the first beam section. This results in the advantage that a change in the weight force of the sample and / or the sample holder is easier, precise, fast, and / or independent of the temperature over a wide temperature range.

[0031] The balancing unit preferably comprises at least one magnet, in particular a permanent magnet, and at least one electromagnetic coil. The balancing unit is preferably configured to feed an electrical compensation current into the electromagnetic coil as a function of the weight force acting on the weighing beam, in particular on the first beam section, and the resulting deflection of the weighing beam, so that the magnet, in particular the permanent magnet, is moved by the magnetic interaction with the coil in such a way that the deflection is reduced.

[0032] The balancing unit preferably has a sensor, in particular an optical one, which is configured to detect an angular position and / or angular position change of the weighing beam, so that a deflection due to a change in the weight of the sample can be detected. The detected deflection is forwarded by the sensor to a controller, which is configured to determine an electrical current intensity from the detected deflection, which is to be fed into the coil to balance or compensate for the deflection. The controller calculates the change in weight of the sample from the change in the electrical current intensity. The balancing unit preferably has a power source configured to feed the electrical compensation current with the determined current intensity into the electromagnetic coil, so that the deflection is compensated. For example, the power source is a battery and / or an accumulator and / or a power supply unit.

[0033] Preferably, the absolute measurement uncertainty of the weight force and / or weight force change of the sample is at most 10 mg, in particular at most 1 mg, in particular at most 200 pg, preferably at most 100 pg, preferably at most 10 pg.

[0034] However, it is not necessary for the scale to have a load beam. Alternatively, the scale can have a weighing platform, for example.

[0035] Preferably, the process gas line has a first line section that runs from the pivot point of the weighing beam to the sample receptacle, and in which the process gas line runs at least partially along the weighing beam. Coupling the gas into the pivot point has a lesser influence on the weighing signal than if the hose were connected directly to the sample receptacle.

[0036] In the context of the present description, “along” means in particular a course in the same direction at a small distance, in particular a parallel course with a maximum angular deviation of preferably at most 5° and / or a distance of at most 3 cm, in particular at most 1 cm.

[0037] For example, the first line section from the load beam pivot point to the sample intake is at least partially connected to the load beam or runs in or along the load beam. This further reduces the influence of a change in the process gas flow in the process gas line on the deflection of the load beam.

[0038] The process gas line preferably has a second line section that runs away from the load beam pivot point and in which the process gas line is not connected to the load beam. In other words, the second line section is spaced from the load beam and is connected to the load beam at the point where the second line section merges into the first line section, preferably in the region of the load beam pivot point. The region is understood to mean, in particular, a radius of at most 4 cm, in particular at most 2 cm, around the pivot point. This advantageously reduces the influence of the process gas line and / or a process gas flow on the weight force and / or weight force change detected by the scale's measuring unit.

[0039] Preferably, the second line section is detachably connected to the weighing beam at the weighing beam pivot point, for example, by means of at least one tab, a knob, a screw, a pin, a groove, a Velcro connection, or other detachable mechanical connections. This advantageously enables easy replacement of the process gas line and / or the weighing beam or parts thereof.

[0040] Preferably, the connection point between the first and second line sections is arranged in the region of the pivot point of the weighing beam such that a change in the process gas flow through the first and / or second line sections leaves the weight force acting on the measuring unit at least substantially unchanged. This is understood, in particular, to mean that an increase in flow through the process gas line from 0 to 0.1 liters per minute results in a change in weight force of a maximum of 5 milligrams, in particular a maximum of 2 milligrams.

[0041] For example, the second line section is at least partially connected (directly or indirectly) to a suspension of the weighing beam or is formed in or on it. This advantageously reduces the additional weight of the scale required for supporting or securing the process gas line. This increases the absolute measuring accuracy of the scale.

[0042] The term "suspension" refers, in particular, to a bearing of the weighing beam at the pivot point, which holds the weighing beam pivot point in a fixed position. The suspension is preferably designed to prevent the weighing beam pivot point from shifting and / or falling. The suspension comprises, for example, at least one tensioning strap that connects the weighing beam pivot point to a reference point, which is located, for example, on a foundation of the scale and / or on a housing base of the scale.

[0043] Preferably, the second line section is connected to the first line section such that the process gas line is connected to the weighing beam in a stress-free manner, for example, with a loop in the second line section in the area before the second line section merges into the first line section. The term "before" refers to the gas flow direction in the process gas line, so that before means opposite to the gas flow direction. As a result, the weight force acting on the weighing beam is advantageously independent of a process gas flow in the process gas line. In other words, a changing process gas flow in the process gas line preferably does not lead to a change in the weight force acting on the weighing beam.

[0044] Preferably, the process gas line in the first line section is at least partially connected to the weighing beam or formed in or on it. This advantageously reduces the influence of the process gas line and / or a process gas flow on the weight force and / or weight force change detected by the scale's measuring unit. Furthermore, the process gas line is advantageously vibrated less, resulting in lower measurement uncertainty.

[0045] Preferably, the process gas line runs at least partially in the axial direction away from the load beam in the region of the load beam pivot point. The axial direction refers in particular to the direction along the axis of rotation about which the load beam can rotate at the load beam pivot point. For example, the load beam is mounted horizontally in the force-compensated state, and the axis about which the load beam can rotate at the load beam pivot point runs orthogonal to the load beam and to the acceleration due to gravity.

[0046] This results in the advantage that the weight force acting on the weighing beam is independent of the process gas flow in the process gas line. In other words, a variable process gas flow in the process gas line preferably does not lead to a change in the weight force acting on the weighing beam. According to one embodiment, the sample holder is suspended from the process gas line. In other words, the process gas line absorbs the weight force of the sample holder. The advantage of this is that any thermal expansion of the sample container and / or the sample holder hardly leads to additional measurement uncertainty.

[0047] In this case, the process gas line is preferably made of glass, ceramic or metal.

[0048] The balance preferably has a pressure vessel that surrounds at least the sample receptacle, so that the sample container can be brought to a process pressure that differs from the ambient pressure. This advantageously makes it possible to investigate a weight force and / or a change in weight force as a function of the process pressure and / or chemical reactions that only occur at a given process pressure. It is possible for the pressure vessel to surround all components of the balance mentioned in claim 1.

[0049] The pressure vessel is preferably configured to set an overpressure and / or negative pressure in the region of the sample and / or the sample container. The pressure vessel is preferably configured to set a process pressure within a pressure range whose upper limit is preferably at least 10 bar, preferably at least 50 bar. The pressure vessel is preferably configured to set a process pressure within a pressure range whose lower limit is preferably a maximum of 10' 1 bar, preferably maximum 10' 3 bar, preferably maximum 10' 4 bar, preferably a maximum of 10' 5 bear.

[0050] The balance preferably has at least one heating element for heating the sample. This advantageously allows for the investigation of the weight force and / or weight force change as a function of the sample temperature and / or chemical reactions that only occur at a given temperature and / or temperature range. Many chemical reactions require activation energy, for example, in the form of heat, to initiate the reaction.

[0051] The scale preferably has at least one gas temperature control device for controlling the process gas at the outlet openings to a predetermined temperature. The heating element and / or the gas temperature control device are preferably suitable for setting a temperature within a range whose lower limit is preferably a maximum of 50°C and / or whose upper limit is preferably at least 250°C, preferably at least 700°C, preferably at least 1000°C.

[0052] This advantageously makes it possible to bring the process gas temperature at the outlet to a desired temperature, which is, for example, at least as high as the sample temperature. Furthermore, it is advantageously possible to supply the activation energy required for many chemical reactions in the form of heat via the process gas temperature, which is, for example, higher than the sample temperature. This advantageously makes it possible to achieve and preferably determine a melting point and / or boiling point of the sample and / or a component of the sample.This advantageously enables control of a chemical reaction of the sample, in particular the reproducibility of the chemical reaction is improved, since the course of chemical reactions usually depends on the temperature of the sample and / or the process gas and thus precise control over the temperature of the sample and / or the process gas is desirable.

[0053] The balance preferably has at least one temperature sensor for detecting a temperature of the sample and / or the process gas. This advantageously makes it possible to detect the weight force and / or weight force change as a function of a sample temperature, in particular the sample temperature and the time during a chemical reaction. This makes it possible, for example, to perform a thermogravimetric analysis and / or a thermal analysis of the sample. The temperature sensor is designed, for example, to detect temperatures in a temperature range with an upper limit of at least 1500°C, preferably at least 2500°C, preferably at least 2850°C.

[0054] The balance preferably has a calorimeter for detecting the amount of heat released during the interaction of the sample with the process gas. This advantageously makes it possible to perform calorimetry, for example, dynamic differential scanning calorimetry. Calorimetry detects the heat energy absorbed and / or released by the sample. Dynamic differential scanning calorimetry detects the amount of heat absorbed or released by the sample during a temperature change. This advantageously makes it possible, for example, to determine at least one phase transition, such as a melting point, of the sample and / or a component of the sample.

[0055] If the balance is equipped with both a temperature sensor and a calorimeter, it is advantageously possible to perform simultaneous thermal analysis, which involves performing thermogravimetric analysis and calorimetry, particularly differential scanning calorimetry, simultaneously. Both sample containers and both sample receptacles are connected to a process gas line and are supplied with process gas in the same way.

[0056] The balance preferably has a process gas flow controller for controlling a process gas flow. In other words, the process gas flow controller is designed to control the process gas flow through the process gas line. The process gas flow controller has, for example, a controller and at least one valve, for example in the process gas line and / or the sample holder, wherein the controller is preferably designed to control the valve. The process gas flow in the process gas line and / or through the outlet openings of the sample holder can preferably be controlled by opening or closing the valve, preferably with at least three intermediate stages between open and closed, preferably at least eight, preferably continuous adjustment of the intermediate range between open and closed.This advantageously allows for monitoring the process gas concentration at the sample and / or the rate at which the process gas flows through the sample. This, in turn, enables monitoring of a chemical reaction in the sample, provided the process gas is a reaction-promoting, reactant, or reaction-inhibiting gas.

[0057] Preferably, the balance comprises a controller configured to automatically perform a method comprising the steps of (i) detecting a weight of the sample at at least one point in time, (ii) supplying process gas according to a stored process gas flow pattern, and (iii) correcting the measured weight using a stored function that assigns a weight correction value to at least one process gas flow. This advantageously ensures that a process gas flow, for example, in the process gas line, causes no or at least only a slight recoil and / or other force on the balance, which would otherwise lead to additional measurement uncertainty.

[0058] Preferably, the controller is configured to transmit the weight correction value to the balancing unit. Preferably, the balancing unit is configured to compensate for the weight force acting on the measuring unit in accordance with the received weight correction value.

[0059] Preferably, the controller is configured to determine the weight correction value based on the respective detected process gas flow using a formula and / or from a predefined value table. The predefined value table can be determined, for example, from previous calibration tests.

[0060] The process gas flow scheme contains, in particular, at least one predefined value for the process gas flow, which prevails, for example, in the process gas line and / or in the outlet openings of the sample holder. The process gas flow scheme contains, for example, several predefined values ​​for the process gas flow, with each value being assigned, for example, to a specific time or time range and / or temperature or temperature range and / or weight or weight range of the sample.

[0061] Preferably, the controller is configured to perform the step of detecting the weight of the sample at at least two points in time, preferably at least five, preferably at least ten points in time. This allows a time dependence of the weight or the weight change of the sample to be determined.

[0062] The balance preferably has a purge gas device configured to purge the area around the measuring unit. The purge gas flows, for example, past the sample holder. The purge gas is, for example, an inert gas, in particular a noble gas or nitrogen. The purge gas device has, for example, a purge gas line configured to direct the purge gas to the sample holder.

[0063] Connected with means that at least one, preferably at least two, points of the process gas line are at least indirectly mechanically connected to the weighing beam, so that the distance between the process gas line and the weighing beam at this point can preferably vary by a maximum of 4 mm, preferably by a maximum of 2 mm.

[0064] Preferably, the connection between the process gas line and the sample holder is gas-tight. Gas-tight is understood in particular to mean that a leakage flow that flows through the process gas line to the sample holder and does not flow into the outlet opening of the sample holder is a maximum of 5%, preferably a maximum of 2%, preferably a maximum of 1%, when a gas from a pressurized container with an overpressure of at least 10 mbar above ambient pressure, and preferably an overpressure of at most 5 bar, preferably at most 1 bar, preferably at most 100 mbar above ambient pressure, is passed through the outlet opening of the sample holder. This pressure may differ from the ambient pressure outside the balance if a pressurized or vacuum container is used.

[0065] The invention further relates to a weighing system comprising a balance as described above and a sample container, in particular a crucible, having a sample container base with at least one gas inlet opening. The sample container is preferably designed to form a gas-tight connection with a sample receptacle, wherein the sample receptacle is preferably flat, at least in sections.

[0066] The sample container preferably has at least two, preferably at least five, preferably at least ten gas inlet openings. The gas inlet openings are preferably evenly distributed over a surface, preferably a circular area. "Evenly" means, in particular, that for the majority of the center points of the openings, the distance to the directly adjacent openings differs by at most 30% from the average distance between adjacent openings. This advantageously achieves an approximately uniform process gas concentration, which varies along the cross-section of the sample, which is orthogonal to the acceleration due to gravity and, for example, at half the height of the sample, by preferably a maximum of 20%, preferably a maximum of 10%.This advantageously makes it possible to measure a more realistic reaction rate that is more closely aligned with real reaction rates in large reactors than, for example, with balances where the sample is only partially flowed through and overflowed by the process gas.

[0067] The at least one gas inlet opening of the sample container bottom has an opening surface of preferably at least 0.0005 mm 2 , preferably at least 0.01 mm 2 , preferably a maximum of 5 mm 2 , preferably maximum 2.5 mm 2 , preferably maximum 1.5 mm 2 .

[0068] At least partially flat is understood in particular to mean that within a section which is preferably sufficiently large for a connection to the sample container, a mean square deviation from a compensation plane through the section is a maximum of 5 pm, preferably a maximum of 0.5 pm.

[0069] In particular, the sample holder has at least one outlet opening which is designed to allow gas to flow through the outlet opening and the sample container placed on the sample holder to the sample arranged in the sample container.

[0070] Preferably, the at least one gas inlet opening of the sample container is designed such that it can be positioned at least partially congruent with at least one outlet opening of the sample holder.

[0071] Preferably, the sample container is designed such that it can be arranged on the sample holder or connected to it in such a way that each gas inlet opening of the sample container is at least partially congruent with one of the outlet openings of the sample holder.

[0072] The sample container is preferably designed to be connected to a sample receptacle of a balance according to the invention in a gas-tight manner. In this context, gas-tight is understood in particular to mean that a leakage flow that flows into the outlet opening of the sample receptacle and does not flow into the sample container is a maximum of 20%, preferably a maximum of 5%, preferably a maximum of 1%, when the sample container is placed on the sample receptacle and / or is connected to the sample receptacle, and a gas from a pressurized container with an overpressure of 10 mbar above ambient pressure is passed through the outlet opening of the sample receptacle.

[0073] The sample container base is preferably made of metal, ceramic, or glass, especially quartz glass. This makes the sample container base advantageously heat-resistant and / or pressure-resistant and suitable for weighing at high temperatures and / or pressures.

[0074] Preferably, the sample container base of the sample container has a base with which the sample container stands on a flat surface, wherein the base has a flatness deviation of a maximum of 50 pm, preferably a maximum of 10 pm.

[0075] Preferably, the sample container has a lid with at least two reaction gas outlet openings for allowing gas to flow out of the sample container interior in a radially outward direction. This provides the advantage that a process gas flowing out of the reaction gas outlet openings has little or no momentum due to gravitational acceleration, thus causing less change in the weight force on the sample holder and thus on the measuring unit.

[0076] Preferably, the reaction gas outlet openings are arranged such that a process gas flowing out of the reaction gas outlet openings has almost no total momentum and thus causes almost no change in the weight force on the sample holder and thus on the measuring unit.

[0077] It's also possible to have an opening at the top of the lid so that the gas can escape axially. Alternatively, the lid can be omitted entirely.

[0078] Preferably, the sample container base has a siphon structure that is connected to the gas inlet opening and leads into the sample container interior. This advantageously prevents the sample or parts of the sample from falling out through the gas inlet opening of the sample container base.

[0079] A siphon structure is understood, in particular, to mean a tube that has at least one bend with an angle of at least 80° between an inlet section before the bend and an outlet section after the bend. For example, the siphon structure has an S-shape, for example, with a circular arc-shaped section.

[0080] The invention further relates to a weighing system comprising a balance according to the invention and a sample container having a sample container base with at least one gas inlet opening. Preferably, the sample holder and the sample container are configured such that the sample container can be positioned in a contact position on the sample holder, in which process gas escaping from the outlet openings flows into the sample container through the gas inlet opening, so that a sample contained in the sample container is permeated by the process gas.

[0081] By flowing through is meant that an entire process gas volume of the process gas flowing out of the at least one outlet opening comes into contact with the sample and that preferably a cross-sectional area of ​​the sample orthogonal to the gas flow direction and / or to the acceleration due to gravity comes into contact with the process gas to at least 60%, preferably at least 80%, preferably at least 90%.

[0082] This has the advantage that the process gas concentration within the sample is approximately constant. This allows a chemical reaction between the sample and the process gas to be investigated more reliably and precisely, and the balance's measurement errors are lower than with conventional balances with process gas flowing over the sample. Preferably, the outlet openings are designed so that the process gas concentration within the sample varies by a maximum of 20%, in particular by a maximum of 12%, and in particular by a maximum of 8%.

[0083] The invention is explained in more detail below with reference to the accompanying figures.

[0084] Figure 1 shows a scale according to the invention with sample holder and process gas line,

[0085] Figure 2 shows a section of the balance according to Figure 1, on whose sample holder a sample container according to the invention is located,

[0086] Figure 3 shows a weighing system according to the invention with a balance according to the invention and a sample container, wherein the balance has a control system and the sample container has radial reaction gas outlet openings,

[0087] Figure 4 shows a weighing system according to the invention with a balance according to the invention and sample container, wherein the balance can have a purge gas line,

[0088] Figure 5 shows part of a scale according to the invention with a weighing beam and with a representation of the process gas line, which is connected to the weighing beam in a first line section, and

[0089] Figure 6 shows a sample container of a weighing system according to the invention with gas inlet openings with a siphon structure.

[0090] Figure 7a shows a scale according to the invention without a weighing beam according to a second embodiment of the invention and

[0091] Figure 7b shows a section of a scale according to the invention according to a third embodiment of the invention and

[0092] Figure 8 shows a section of a scale according to the invention according to a fourth embodiment of the invention and

[0093] Figure 9 shows a section of a scale according to the invention in accordance with a fifth embodiment of the invention. Figure 1 shows a scale 2 according to the invention. The scale 2 has a sample holder 8, which is configured to absorb a weight force G of the sample container 10 containing a sample 4. The scale 2 further has a process gas line 12, which is configured to supply a process gas 6 to the sample holder 8. The arrow P indicates the process gas flow direction. The arrow P' symbolizes the process gas 6 that has flowed through the sample 4 and escapes into the environment.

[0094] The scale 2 also has a measuring unit 14 for measuring the weight force G acting on the sample holder 8, or a weight force change dG / dt. In particular, the measuring unit 14 detects when the weight G of the sample 4 in the sample container 10 changes. The sample holder 8 has an outlet opening 16 for the process gas 6, so that the process gas 6 is directed to a sample container bottom 18 (see Figure 2).

[0095] The scale has a weighing beam 20, which is mounted on a weighing beam pivot point 22. The sample holder 8 is connected to the measuring unit 14 via the weighing beam 20, so that a weight force and / or change in weight force of the sample 4 can be measured by the measuring unit 14. A weight force acting on the sample holder 8 can be balanced using a balancing unit 24. The balancing unit 24 is used for rough adjustment to bring the weighing beam 20 at least approximately into balance before the actual measurement.

[0096] The measuring unit 14 has, for example, a permanent magnet 25 (see Figure 5) and an electromagnetic coil 27 through which a compensation current Ik with a predetermined electrical current intensity can be fed. The magnetic field thus generated generates a force on the permanent magnet 25 and thus a torque on the load beam 20.

[0097] If the weighing beam 20 is deflected before the start of a measurement due to a change in weight, for example, by placing the sample container 10 on the sample holder 8, the deflection is detected by at least one position sensor 29.1, for example, optical sensors, and a controller 40 feeds an electrical compensation current lk required for compensation into the coil. The compensation current could also be called a balancing current. For example, a second position sensor 29.2 may be present.

[0098] The compensation current lk is changed during the measurement so that the angular position of the load beam 20 remains constant. This significantly reduces the measuring range of the measuring unit 14, which reduces the measurement uncertainty.

[0099] Figure 2 shows a section of the balance 2 and a sample container 10. The sample container 10 has a sample container base 18 with several gas inlet openings 19i. The sample container 10, together with the balance 2, forms a weighing system 50.

[0100] The sample container 10 is designed to form a gas-tight connection with the sample holder 8. For this purpose, the sample holder 8 is flat on the side facing the sample container 10, and the sample container 10 has a sample container base 18 with a base surface 46 that has a flatness deviation of a maximum of 50 pm, for example, a maximum of 10 pm. Thus, the sample holder 8 has a correspondingly small flatness deviation.

[0101] The sample holder 8 and the sample container 10 are designed such that the sample container 10 can be positioned in a contact position on the sample holder 10, in which process gas 6 exiting from the outlet opening 16 flows through the gas inlet openings 19.i into the sample container 10, so that the sample 4 contained in the sample container 10 is flowed through by the process gas 6. The sample container base 18 is made of ceramic or glass, for example, quartz glass.

[0102] Figure 3 shows that the sample container 10 can have a lid 48 that has two reaction gas outlet openings 49.1, 49.2 for allowing gas to flow out of a sample container interior 47 in a radially outward direction R. This reduces a change in weight caused by the escaping gas 47. For example, the two reaction gas outlet openings 49.1, 49.2 are located opposite each other. However, this lid is not necessary.

[0103] It is possible for the lid 48 of the sample container 10 to have more than two reaction gas outlet openings 49.1, 2. The reaction gas outlet openings 19.i are arranged such that the pulses due to the outflowing gas add up to at least substantially zero.

[0104] In this example, the sample holder 8 of the balance 2 has five outlet openings 16.1, ..., 16.5 along the section shown. In total, the sample holder 8 in this example has, for example, 18 to 20 outlet openings 16.i, which are distributed approximately evenly over a circular area.

[0105] Figure 4 shows a balance 2 in whose sample holder 8 there is a plurality of outlet openings 16.i (i = 1, 2, ..., N), for example N = 55 to 63 outlet openings 16.i, which are distributed approximately evenly on a circular area, for example.

[0106] The balance 2 has a pressure vessel 26 which surrounds the sample holder 8 and the other components of the balance 2, so that the sample container 10 can be brought under a process pressure pp which deviates from the ambient pressure pu.

[0107] In addition, the balance 2 has a heating element 28 for heating the sample 4, a gas tempering device 30 for tempering the process gas 6 at the outlet openings 16 to a predetermined temperature and a temperature sensor 32 which has a connecting cable 33 for detecting a temperature of the sample 4 and the process gas 6.

[0108] Using a calorimeter, the amount of heat released and / or absorbed during the interaction of sample 4 with process gas 6 can be measured. For example, the calorimeter includes a second sample container in which no reaction takes place. Temperature sensors are installed in both sample containers. The temperature difference between the two sample containers can be used to determine the heat released by the reaction.

[0109] In addition, the scale 2 has a process gas flow controller 36 for controlling the process gas flow. For example, the process gas flow controller 36 is configured to control the process gas flow according to a predefined process gas flow pattern with predefined process gas flow values. The desired process gas flow is, for example, constant over a predefined time period or amounts to various predefined values ​​for predefined time intervals depending on the time.

[0110] Figure 5 shows part of a balance 2 according to the invention with a weighing beam 20 and with the process gas line 12, which is composed of a first line section 12.1 and a second line section 12.2. The first line section 12.1 is connected to the weighing beam 20, which is mounted on a weighing beam pivot point 22. The sample holder 8 is connected to the measuring unit 14 via the weighing beam 20.

[0111] In the first line section 12.1, which runs from the load beam pivot point 22 of the load beam 20 to the sample holder 8 (see Figure 1), the process gas line 12 runs along the load beam 20. The second line section 12.2 runs away from the load beam pivot point 22 and is not connected to the load beam 20.

[0112] The second line section 12.2 transitions into the first line section 12.1 at the load beam pivot point 22. In this example, the transition is realized via a loop, so that the process gas line 12 is routed to the load beam 20 without stress. This advantageously prevents any change in the weight force acting on the measuring unit 14 when a process gas flow in the process gas line 12 changes.

[0113] Alternatively, as shown in Figure 8, it is possible that the process gas line 12 from the sample holder does not run along the weighing beam 20.

[0114] The process gas line is routed through a first process gas line connection 70 toward the sample receptacle 8, which is located here in the pressure vessel 26. A second process gas line connection 72 is arranged in the housing 68 and is configured to guide the process gas line 12 from outside the housing 68, for example, from a pressure gas vessel, into the balance 2.

[0115] Figure 6 shows a sample container 10 according to the invention with gas inlet openings 19.1, ..., 19.3 in the sample container base 18 with a siphon structure. Three exemplary siphon structures are shown for the three gas inlet openings 19.1, 19.3 shown. The siphon structure prevents the sample 4, which is located in the sample container interior 47, from falling out through the gas inlet openings 19.1, ..., 19.3. Other siphon structures are also possible.

[0116] As Figure 5 shows, the balance has a controller 40 which is designed to automatically carry out a method comprising the steps of (i) detecting a weight of the sample 4 at at least one time t, (ii) supplying process gas 6 according to a stored process gas flow pattern, and (iii) correcting the measured weight G using a stored function which assigns a weight correction value to at least one process gas flow.

[0117] Figure 7a shows a scale 2 without a weighing beam, in which the measuring unit 14 has a strain gauge 74 which is connected to the electrical control 40.

[0118] Figure 7b shows a section of another scale 2, in which the load beam 20 runs horizontally. Only the first section of the line is shown. The remaining components are those shown in Figure 1. Sample 4 is at the same height as the load beam 20.

[0119] Figure 9 schematically shows another scale 2, in which the sample holder 8 is suspended from the process gas line 12. The process gas line 12 absorbs the weight of the sample holder 8 and the sample 4.

[0120] List of reference symbols

[0121] 2 scales 36 process glass flow control

[0122] 4 Sample

[0123] 6 Process gas 40 Control

[0124] 8 Sample holder 46 Base of the sample container

[0125] 47 Sample container interior

[0126] 10 Sample container 48 Sample container lid

[0127] 12 Process gas line 49. i Reaction gas outlet openings

[0128] 12.1 first line section

[0129] 12.2 second line section 50 weighing system

[0130] 14 Measuring unit 56 Bracket (clamping strap)

[0131] 16. i Exit openings

[0132] 18 Sample container bottom 60 Purge gas

[0133] 19 Gas inlet opening 61 Purge gas device

[0134] 68 housings

[0135] 20 load beams

[0136] 22 Weighing beam pivot point 70 first process gas line

[0137] 24 Balancing unit connection

[0138] 25 permanent magnets 72 second process gas line

[0139] 26 Pressure vessel connection

[0140] 27 Coil 74 Strain gauge

[0141] 28 Heating element

[0142] 29 Position sensor A axial direction lk compensation current

[0143] 30 Gas tempering device N Number of outlet openings

[0144] 32 Temperature sensor R radial direction

[0145] G Direction of gravity

Claims

Patent claims 1 . Balance (2) for weighing a sample (4) under interaction with at least one process gas (6), wherein the balance (2) (a) at least one sample holder (8) which is designed to absorb a weight force of a sample container (10) with the sample (4), (b) at least one process gas line (12) which is designed to supply the process gas (6) to the sample holder (8), and (c) at least one measuring unit (14) for measuring the weight force or a change in weight force acting on the sample holder (8), characterized in that (d) the sample holder (8) has at least one outlet opening (16) for the process gas (6), which is arranged to guide the process gas (6) to a sample container bottom (18) and (e) the absolute measurement uncertainty of the weight force and / or change in weight force of the sample is not more than 10 mg.

2. Scale (2) according to claim 1, characterized in that the scale (2) has a weighing beam (20) which is mounted in a weighing beam pivot point (22), (a) the sample holder (8) by means of the weighing beam (20) with the measuring unit (14) is connected so that a weight force and / or weight force change of the sample (4) can be measured by means of the measuring unit (14), (b) the balance (2) has a balancing unit (24) for balancing a weight force acting on the sample holder (8) and (c) the process gas line (12) (i) has a first line section (12.1) which runs from the load beam pivot point (22) of the load beam (20) to the sample holder (8) and in which the process gas line (12) runs at least partially along the load beam (20), and (ii) has a second line section (12.2) which runs away from the load beam pivot point (22) and in which the process gas line (12) is not connected to the load beam (20).

3. Balance (2) according to claim 2, characterized in that the process gas line (12) in the first line section (12.1) is at least partially connected to the weighing beam (20) or is formed in or on it.

4. Balance (2) according to one of claims 2 or 3, characterized in that the process gas line (12) in the region of the weighing beam pivot point (22) runs at least partially in the axial direction (A) away from the weighing beam (20).

5. Balance (2) according to one of claims 2 to 4, characterized in that the sample holder (8) hangs on the process gas line (12).

6. Scale (2) according to one of the preceding claims 2 to 5, characterized by (a) a pressure vessel (26) surrounding the sample holder (8) so that the sample container (10) can be brought under a process pressure different from the ambient pressure, and / or (b) at least one heating element (28) for heating the sample (4) and / or (c) at least one gas tempering device (30) for tempering the process gas (6) at the at least one outlet opening (16) to a predetermined temperature, and / or (d) at least one temperature sensor (32) for detecting a temperature of the sample (4) and / or the process gas (6), and / or (e) a calorimeter (34) for detecting a quantity of heat released and / or absorbed during the interaction of the sample (4) with the process gas (6) and / or (f) a process gas flow controller (36) for controlling a process gas flow.

7. Scale (2) according to one of the preceding claims 2 to 6, characterized by a control (40) which is designed to automatically carry out a method with the steps (i) detecting a weight of the sample (4) at at least one time, (ii) supplying process gas (6) according to a stored process gas flow scheme, and (iii) correcting the measured weight using a stored function that assigns a weight correction value to at least one process gas flow.

8. Weighing system (50) with (a) a scale (2) according to any one of claims 1 to 7 and (a) a sample container (10) which (i) has a sample container bottom (18) with at least one gas inlet opening (19) and (ii) is designed to form a gas-tight connection with a, in particular flat, sample holder (8), (b) wherein the sample holder (8) and the sample container (10) are designed such that the sample container (10) can be positioned in a contact position on the sample holder (8), in which process gas (6) emerging from the at least one outlet opening (16) flows through the gas inlet openings (19.i) into the sample container (10), so that a sample (4) contained in the sample container (10) is flowed through by the process gas (6).

9. Weighing system (50) according to claim 8, characterized in that the sample container base (18) consists of metal, ceramic or glass, in particular quartz glass:

10. Weighing system (50) according to claim 8 or 9, characterized in that the sample container base (18) has a standing surface (46) with which the sample container (10) stands on a flat surface, wherein the standing surface (46) has a flatness deviation of a maximum of 50 pm, in particular a maximum of 10 pm.

11. Weighing system (50) according to one of claims 8 to 10, characterized in that the sample container (10) has a lid (48) which has at least two reaction gas outlet openings (49.i) for allowing gas to flow out of a sample container interior (47) in a radially outward direction (R).

12. Weighing system (50) according to one of claims 8 to 11, characterized in that the gas inlet opening (19) in the sample container base (18) has a siphon structure which is connected to the gas inlet opening (19) and leads into a sample container interior (47).

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