Rotary Dosing Device

Abstract

A rotary dispensing device for use in an analytical instrument rapidly transfers a series of precise molar amounts of gas from a primary stream to a secondary stream. The device has a rotating chamber with a dispensing port that cycles through three states: filling, equilibrating, and transferring. The device cycles in an overlapping manner, such that one dose volume is filled with gas from the primary stream, another dose volume equilibrates at a known pressure and temperature, and another dose volume transfers its contents to the secondary stream. The device begins operation such that the first transfer in the series is a properly filled and equilibrated dose from the primary stream. Rather than cycling a single dose volume multiple times through the three states, the overlapping action of the rotary dispenser allows multiple precise molar amounts of gas to be transferred in one-third of the time.

Description

[Technical Field]

[0001] The present invention relates to a dosing device for delivering precise molar amounts of gas, and in particular to a dosing device for use in an elemental analyzer. [Background technology]

[0002] The determination of elements such as carbon, hydrogen, and nitrogen in organic materials is desirable for many reasons. In recent years, the food market has become interested in determining the amount of protein in a sample, which can be determined by the nitrogen content. Therefore, determining nitrogen is important in providing useful information to the nutrition market. Carbon-to-hydrogen ratios are desirable in characterizing coal and coke samples, as are carbon, hydrogen, and nitrogen ratios in various other organic materials. Therefore, elemental analyzers have been used for these and other applications for some time.

[0003] In the present element analyzer, a combustion or reduction furnace may be provided to combust or reduce sample materials so that the combustion gases produced thereby may be analyzed. One such analyzer system is described in commonly assigned U.S. Patent No. 7,070,738. U.S. Patent Nos. 7,497,991, 4,622,009, 6,291,802, and 6,270,727 also disclose combustion system components.

[0004] Dosage devices are used in one or more applications. In one application, a gas dosator is used to accurately transfer a precise amount of a known calibrant from a primary stream to a secondary stream as part of calibrating a detection system in the secondary stream. Some designs have a single dose size for single-point calibration, while others have two or more dose sizes for multi-point calibration.

[0005] In another application, the primary gas consists of at least a portion of the combustion gases evolving from the combustion of the sample, gases collected and equilibrated using a molar transfer device. A dosing device transfers small, representative aliquots from the primary gas stream to a secondary stream for further processing and analysis. Because reagents in the secondary stream are consumed by processing the aliquots, the dose size is made as small as possible to minimize the cost of analysis. However, the dose must be large enough to enable the instrument to achieve the specified detection limit in the most demanding applications. There can be more than one dose size, allowing the operator to select the size that best suits their analytical needs. In one instrument with two dose sizes, the ratio of the two dose volumes is approximately 3:1, with the two doses transferring approximately 1 / 500 and 1 / 1500 of the volume of gas collected in the primary stream.

[0006] Dosing devices that transfer repeatable amounts of gas from a primary stream into a secondary stream are common. The device is placed in a constant temperature environment or a means is provided to accurately measure the device's temperature. Valving means typically cycle the dose through three states: filling, equilibration, and transfer. The equilibration state is important to allow the primary gas contained in a fixed volume to stabilize at the desired temperature and pressure. By knowing the volume, temperature, and pressure of the dosing device, the exact molar amount of gas is known. If more than one dose is used, additional valving means are required to select the dose size.

[0007] For high-precision dosing, the valve pathway must have low dead volume, and the device must operate multiple valves simultaneously. If two-way valves are used to achieve gas transfer, a bank of eight such valves is required, increasing the likelihood of substantial dead volume. Alternatively, four three-way valves can provide the same operation with lower dead volume, but an additional two-way valve is required to disable the primary flow for equilibration. When multiple dose sizes are present, only one dose is used at any time.

[0008] One such design uses a stem valve, essentially consisting of multiple three-way valves located on the same stem. The stem is moved between two positions, simultaneously actuating all valves between two states (fill and transfer). Another similar stem valve is used to select one or the other for two dosage sizes. The valve body has eight external ports that extend into the internal stem chamber. Because multiple O-rings are installed on the stem and must pass through the ports when the stem is actuated, the ports must have smooth edges to prevent slicing through the O-rings. To minimize dead volume, the stem diameter is kept as small as possible, which makes manufacturing difficult. The external and internal connections create multiple potential leak points, making the valve difficult to troubleshoot. Summary of the Invention

[0009] The disclosed invention solves the problem of rapidly transferring a series of precise molar amounts of gas from a primary stream to a secondary stream using a simple device that is easy to manufacture and operate, has essentially zero dead volume, and fewer leak points. The rotary dispensing device includes a rotating chamber, a valve body, two end caps, two end seals, and a motor. The rotating chamber has at least two internal dispensing ports, which function as doses. As the cylinder rotates, the doses cycle through two or three states: filling, equilibration (optional), and transfer. The device cycles in an overlapping manner, such that one dose volume is filled with gas from the primary stream, another dose volume equilibrates at a known pressure and temperature, and another dose volume transfers its contents to the secondary stream.

[0010] The rotating chamber can be operated multiple times during a single analysis to dose variable but precise amounts of primary gas into the secondary stream. For example, the dosing chamber can be operated once for one analysis and three times for the next to generate data for two points on a calibration curve. Multiple doses can also provide flexibility in combustion applications, allowing the operator to more closely match aliquot volumes to analytical requirements.

[0011] An aspect of the present invention is to provide a rotary dispensing device comprising a valve body and a rotating cylindrical chamber contained within the valve body, the rotating cylindrical chamber having an axial length and including a first dispensing port extending therethrough and a second dispensing port extending therethrough. The rotary dispensing device further comprises a primary upstream port for receiving the primary gas stream and introducing the primary gas stream into one of the first and second administration ports of the rotating cylindrical chamber, a secondary upstream port for receiving the secondary gas stream and introducing the secondary gas stream into one of the first and second administration ports of the rotating cylindrical chamber, a primary downstream port for receiving the remainder of the primary gas stream from one of the first and second administration ports of the rotating cylindrical chamber, a secondary downstream port for receiving the secondary gas stream from one of the first and second administration ports of the rotating cylindrical chamber, and a motor for rotating the rotating cylindrical chamber such that each of the first and second administration ports is sequentially aligned with the primary upstream and downstream ports for filling with the primary gas stream and the secondary upstream and downstream ports for transferring gas to the secondary gas stream.

[0012] Another aspect is to provide a method for transferring a precise amount of a known calibrant from a primary stream to a secondary stream to calibrate a detection system in the secondary stream, the method comprising using a rotary dispensing device as described herein, where the known calibrant is introduced into a primary upstream port and a dose of the calibrant is transferred to the secondary stream via a secondary downstream port.

[0013] Another aspect is to provide a method for transferring a small, representative aliquot of a precise volume from a primary gas stream containing a secondary stream for further processing and analysis, the primary gas stream comprising at least a portion of combustion gases evolved from combustion of a sample to be analyzed, the method comprising using a rotary dispensing device as described herein, wherein the primary gas stream is introduced into a primary upstream port and a precise volume aliquot is transferred to the secondary stream via a secondary downstream port.

[0014] Another aspect of the present invention is to provide a rotary dispensing device comprising a valve body and a rotary cylindrical chamber contained within the valve body, the rotary cylindrical chamber having an axial length and including opposite upstream and downstream end faces, a first dispensing port extending from the upstream end face to the downstream end face, a second dispensing port extending from the upstream end face to the downstream end face, and a third dispensing port extending from the upstream end face to the downstream end face. The rotary dispensing device further comprises a primary upstream port for receiving the primary gas stream and introducing the primary gas stream into one of the first, second, and third administration ports of the rotating cylindrical chamber, a secondary upstream port for receiving the secondary gas stream and introducing the secondary gas stream into one of the first, second, and third administration ports of the rotating cylindrical chamber, a primary downstream port for receiving a remainder of the primary gas stream from one of the first, second, and third administration ports of the rotating cylindrical chamber, a secondary downstream port for receiving the secondary gas stream from one of the first, second, and third administration ports of the rotating cylindrical chamber, a balancing port, and a motor for rotating the rotating cylindrical chamber such that each of the first, second, and third administration ports is sequentially aligned with the primary upstream and downstream ports for charging the primary gas stream, the balancing port for balancing the gas, and the secondary upstream and downstream ports for transferring the gas to the secondary gas stream.

[0015] These and other features, objects, and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0016] In the drawings, [Figure 1] FIG. 1 is an isometric view of a rotary dispensing device. [Figure 2] FIG. 2 is an enlarged isometric view of an upstream portion of the rotary dispensing device shown in FIG. 1. [Figure 3] FIG. 2 is an enlarged isometric view of the downstream portion of the rotary dispensing device shown in FIG. 1. [Figure 4] FIG. 2 is an isometric view of a rotating chamber used in the rotary dispensing device shown in FIG. 1. [Figure 5] FIG. 2 is a top view of an upstream end seal used in the rotary dispensing device shown in FIG. 1. [Figure 6] FIG. 2 is a top view of a downstream end seal used in the rotary dispensing device shown in FIG. 1. [Figure 7A] 2 is a schematic diagram of the rotary dispensing device shown in FIG. 1 with the dispensing ports of the rotating chamber in a first normal set of positions. [Figure 7B] 2 is a schematic diagram of the rotary dispensing device shown in FIG. 1 with the dispensing port of the rotating chamber in an intermediate set of positions. [Figure 7C] 2 is a schematic diagram of the rotary dispensing device shown in FIG. 1 with the dispensing ports of the rotating chamber in a second normal set of positions. [Figure 7D] 2 is a schematic diagram of the rotary dispensing device shown in FIG. 1 with the dispensing ports of the rotating chamber in a third normal set of positions. DETAILED DESCRIPTION OF THE INVENTION

[0017] 1, there is shown a rotary dispensing device 10 having a rotating cylindrical chamber 20, a valve body 30, an upstream end cap 40, a downstream end cap 50, an upstream end seal 60, a downstream end seal 70, and a motor 80. As best shown in FIG. 7A, five gas paths connect to the device 10: a primary upstream path A, a primary downstream path B, a secondary upstream path C, a secondary downstream path D, and a downstream balance path E.

[0018] As best shown in FIG. 4 , the rotating cylindrical chamber 20 has flat end faces 21 and 22 perpendicular to the axis of rotation of the cylinder, including an upstream end face 21 and a downstream end face 22. In the illustrated example, three equal-volume administration ports 24, 26, and 28 extend the length of the chamber 20 to both end faces 21 and 22 and serve as the internal dose volume of the device 10. However, it should be noted that the administration ports 24, 26, and 28 may have different volumes to allow for different sized doses from each port. As shown in FIG. 5 , the administration ports 24, 26, and 28 are located at a fixed radius R1 from the center of the end faces 21 and 22 and are spaced 120° apart from one another. While three administration ports 24, 26, and 28 are shown in the disclosed embodiment, only two administration ports are required, and additional administration ports may be provided. Such additional administration ports may be provided for a variety of reasons. For example, if additional equilibration time is desired, additional administration ports and additional equilibration positions may be provided between the fill position and the transfer position. There may also be additional ports and locations that simply await filling. Although administration ports 24, 26, and 28 are shown as extending parallel to the axis of rotating cylindrical chamber 20, the administration ports may extend at an angle to this axis or may enter or exit chamber 20 on the curved sidewalls of chamber 20.

[0019] 1, the valve body 30 has a large cylindrical bore for receiving the rotating cylindrical chamber 20 and bearings (not shown) for radially compressing the chamber 20 while allowing it to rotate freely. An upstream cap 40 and a downstream cap 50 are fastened to the valve body 30 to axially retain the rotating cylindrical chamber 20.

[0020] The upstream end seal 60 is located between the upstream end cap 40 and the upstream end face 21. The downstream end seal 70 is located between the downstream end cap 50 and the downstream end face 22. As best shown in FIG. 2 , the seals 60 and 70 are preferably constructed of an elastomeric material 62, 72 in contact with the caps 40 and 50 and a low-friction material 63, 73, such as PTFE, or other material in contact with the rotating end faces 21, 22 of the chamber 20. The elastomeric material 62, 72 provides a spring force to keep the low-friction sealing surfaces pressed against the end faces 21 and 22. The seals 60 and 70 are retained within the caps 40 and 50 to prevent them from rotating when the chamber 20 rotates.

[0021] When viewed from the upstream cap 40 looking at the upstream seal 60 and upstream end face 21 (FIG. 5), six positions are defined with reference to the axis of rotation of the chamber. These positions are spaced at 60° intervals at radius R1. The selection of the 0° position is arbitrary. The six positions are labeled 1 through 6 clockwise. FIG. 6 shows the positions on the downstream seal 70 as viewed from the upstream end.

[0022] As shown in FIGS. 1, 2, and 7A-7D, the primary upstream port 42 on the exterior of the upstream cap 40 connects to upstream primary pathway A, and the secondary upstream port 44 connects to upstream secondary pathway C. These two ports 42 and 44 extend internally to interface with the administration ports 24, 26, and 28. The primary upstream port 42 occupies position 1, and the secondary upstream port 44 occupies position 5. Upstream grooved pathways 46 and 48 on the interior surface of the upstream cap 40 allow the valve to operate in two positions: activated and normal, as described further below. On the upstream cap 40, the first upstream grooved pathway 46 extends between positions 1 and 2, and the second upstream grooved pathway 48 extends between positions 4 and 5.

[0023] As shown in FIGS. 1, 3, and 7A-7D, the downstream cap 50 has three downstream ports 51, 52, and 53. The primary downstream port 51 connects externally to the primary downstream pathway B, the secondary downstream port 52 connects to the secondary downstream pathway D, and the balancing downstream port 53 connects to the balancing downstream pathway E. These three downstream ports 51, 52, and 53 extend internally and interface with one of the administration ports 24, 26, and 28. The primary downstream port 51 occupies position 1, the secondary downstream port 52 occupies position 5, and the balancing port 53 occupies position 3. Two downstream grooved pathways 54 and 55 are present on the inner surface of the downstream cap 50. The first downstream grooved pathway 54 extends between positions 1 and 2, and the second downstream grooved pathway 55 extends between positions 4 and 5. If balancing using back pressure is not desired, the balancing port 53 may be eliminated.

[0024] In the end seals 60 and 70 there are passages that align with the ports and grooved passages in the caps 40 and 50 .

[0025] The end faces 21 and 22 are finished to provide minimal wear to the sealing surfaces as they rotate.

[0026] There is a feature 82 in the center of downstream end face 22 that has a non-circular shape so that it can be engaged by a similarly shaped mating coupling on the shaft of motor 80 to rotate chamber 20. Motor 80 may be a stepper motor that fastens to downstream cap 50, with the feature on the motor shaft passing through opening 83 in downstream cap 50 and downstream seal 70 engaging the mating feature 82 on chamber face 22 to rotate chamber 20.

[0027] Under normal conditions, internal dosing ports 24, 26, and 28 align with positions 1, 3, and 5 on caps 40 and 50 and end seals 60 and 70, as shown in FIG. 7A : position 1 is during filling, position 3 is during equilibration, and position 5 is during transfer. In the example shown in FIG. 7A , first dosing port 24 is aligned at position 1 in communication with ports 42 and 51 to fill first dosing port 24 with gas from upstream primary gas stream A while excess gas flows into downstream primary gas stream B, which may be atmospheric exhaust 106. Second dosing port 26 is aligned at position 3 to communicate with equilibration port 53 to equilibrate at a specific pressure, which may be established by backpressure exhaust gas stream E. Third dosing port 28 is aligned at position 5 in communication with ports 44 and 52 to allow upstream secondary gas stream C to flow through third dosing port 28 into downstream secondary gas stream D. The chamber 20 is then rotated clockwise 120° for each cycle, as further described below.

[0028] However, for the first transfer, it is undesirable to begin by advancing chamber 20 clockwise 120° because the gas at the dose port (second transfer port 26) in equilibrium position 3 is unknown, and therefore transfer to secondary gas stream D is undesirable. Thus, at start-up, chamber 20 is rotated counterclockwise 60° to an intermediate position so that its dose ports 24, 26, and 28 are aligned with positions 2, 4, and 6. Grooved channels 46, 48, 54, and 55 in end caps 40 and 50 and end seals 60 and 70 extend primary upstream and downstream paths A and B, and secondary upstream and downstream paths C and D, to reach intermediate positions 2 and 4. As shown in FIG. 7B, the second administration port 26, which was at position 3, is now moved to be filled at position 2, the third administration port 28, which was at transfer position 5, now provides a flow path for the secondary gas flow at position 4, and the first administration port 24, which was filled at position 1, is now returned to its standby position at position 6 with its input and output blocked.

[0029] After filling the second administration port 26, the chamber 20 advances 60° clockwise to the original starting position ( FIG. 7A ) to equilibrate the first dose contained in the second administration port 26 at position 3. The chamber 20 then advances 120° clockwise per cycle as normal. For example, moving from the position shown in FIG. 7A to the position shown in FIG. 7C , the second administration port 26 is advanced from equilibrium position 3 to transfer position 5 to transfer the first dose to downstream secondary stream D using carrier gas from upstream secondary stream C, the first administration port 24 is moved from fill position 1 to equilibrium position 3, and the third administration port 28 is moved from transfer position 5 to fill position 1. Next, chamber 20 is again advanced 120° clockwise such that chamber 20 rotates from the position of FIG. 7C to the position of FIG. 7D , and first administration port 24 is advanced from equilibrium position 3 to transfer position 5, and third administration port 28 is moved from fill position 1 to equilibrium position 3, and second administration port 26 is moved from transfer position 5 to fill position 1, to transfer a second dose to downstream secondary gas flow D using carrier gas from carrier source 102 via upstream secondary gas flow C. Next, chamber 20 is again advanced 120° clockwise such that chamber 20 rotates from the position of FIG. 7D to the initial position of FIG. 7A , and the third dose at third administration port 28 can be transferred to secondary gas flow D.

[0030] The chamber 20 may continue to rotate, delivering doses to the secondary gas stream D. The number of rotations depends on the molar dose desired for a particular analysis. This rotary dosing device 10 therefore allows for the selection of any particular dose in single dose increments from one of the dosing ports 24, 26, and 28. The rotating chamber 20 can be actuated multiple times during a single analysis to dose variable but precise amounts of primary gas into the secondary gas stream. For example, the rotary dosing device 10 can be actuated once for one analysis and three times for the next analysis to generate data for two points on a calibration curve. Multiple doses can also provide flexibility in combustion applications, allowing the operator to more closely match aliquot volumes to analytical requirements.

[0031] The rotary dosing device 10 is capable of rapidly transferring a range of precise molar amounts of gas from a primary gas stream to a secondary gas stream. The rotary dosing device 10 is a simple device that is easy to manufacture and operate, has essentially zero dead volume, and has fewer leak points.

[0032] The rotary dispensing device 10 can be used in a method for transferring a precise amount of known calibrant from a primary gas stream to a secondary gas stream to calibrate a detection system in the secondary stream. The method involves using the rotary dispensing device 10 described herein, where the known calibrant is introduced into the primary upstream port 42 and a dose of the calibrant is transferred to the secondary stream via the secondary downstream port 52. The size of the dose of calibrant can be varied to achieve multi-point calibration.

[0033] The rotary dosing device 10 can also be used in a method for transferring small, representative aliquots of precise volume from a primary gas stream containing a secondary stream for further processing and analysis, where the primary gas stream contains at least a portion of combustion gases evolved from combustion of a sample to be analyzed. The method involves using the rotary dosing device 10 described herein, where the primary gas stream is introduced into the primary upstream port 42 and a precise volume aliquot is transferred to the secondary stream via the secondary downstream port 52. The size of the aliquot dose is variable.

[0034] Thus, the rotary dispensing device 10 is suitable for use in an elemental analyzer including a sample source 100 for providing a gas sample in a primary gas stream A received at the primary upstream port 42 of the rotary dispensing device 10. The sample source 100 may be a combustion furnace. Examples of suitable combustion furnace components are disclosed in U.S. Patent Nos. 7,497,991, 4,622,009, 6,291,802, and 6,270,727. The elemental analyzer may also include a carrier source 102 for providing a carrier gas in a secondary gas stream C received at the secondary upstream port 44 of the rotary dispensing device 10. The elemental analyzer may further include at least one analysis cell 104 for receiving a secondary gas stream D from the secondary downstream port 52 and analyzing the received secondary gas stream D into which the gas sample is introduced by the rotary dispensing device 10. Additionally, the element analyzer may include an atmospheric exhaust 106 for exhausting the primary gas stream B received from the primary downstream port 51 to the atmosphere, and a back pressure exhaust 108 coupled to equilibrate the port 53, which is connected to the equilibration port 53 at a desired pressure, bringing the dose at the dose port to the desired pressure.

[0035] It will be apparent to those skilled in the art, in view of the teachings herein, that multiple bidirectional or unidirectional ballasts can be used to improve analyzer performance, and it will also be apparent to those skilled in the art that these and other modifications can be made without departing from the spirit or scope of the present invention, as defined by the appended claims.

Claims

1. 1. A rotary dispensing device comprising: A valve body; a rotating cylindrical chamber contained in the valve body, the chamber having an axial length; a first administration port extending through the rotating cylindrical chamber; a second administration port extending through the rotating cylindrical chamber; a rotating cylindrical chamber including a third administration port extending through said rotating cylindrical chamber; a primary upstream port for receiving a primary gas flow and for introducing the primary gas flow into one of the first through third ports of the rotating cylindrical chamber; a secondary upstream port for receiving a secondary gas stream and for introducing the secondary gas stream into one of the first through third administration ports of the rotating cylindrical chamber; a primary downstream port for receiving the primary gas flow from one of the first through third administration ports of the rotating cylindrical chamber; a secondary downstream port for receiving the secondary gas flow from one of the first through third administration ports of the rotating cylindrical chamber; a balancing port; a motor for rotating the rotating cylindrical chamber, wherein each of the first, second, and third administration ports is the primary upstream port and the primary downstream port for loading a first dose, a second dose, or a third dose of a primary gas from the primary gas stream; the balancing port for balancing the first, second or third respective doses of primary gas; the secondary upstream port and the secondary downstream port for delivering the first, second, or third dose of primary gas to the first, second, or third dose port, respectively; and a motor for sequentially aligning the rotary dispensing device.

2. 2. The rotary dispensing device of claim 1, wherein when the second administration port is aligned with the primary upstream port and the primary downstream port to fill the second dose of primary gas, the first administration port simultaneously aligns with the balancing port for balancing the first dose.

3. 3. A rotary dispensing device according to claim 1 or 2, wherein when the third administration port is aligned with the primary upstream port and the primary downstream port to load the third dose of primary gas from the primary gas stream, the second administration port is simultaneously aligned with the equilibration port for equilibrating the second dose of primary gas, and the first administration port is simultaneously aligned with the secondary upstream port and the secondary downstream port for transferring the first dose of primary gas to the secondary gas stream.

4. an upstream end cap secured to the upstream end of the valve body; a downstream end cap fixed to the downstream end of the valve body, A rotary dispensing device according to any one of claims 1 to 3, wherein the primary upstream port and the secondary upstream port are provided in the upstream end cap, and the primary downstream port, the secondary downstream port and the balancing port are provided in the downstream end cap.

5. an upstream end seal positioned between the upstream end cap and the upstream end face of the rotating cylindrical chamber; 5. The rotary dispensing device of claim 4, further comprising a downstream end seal positioned between the downstream end cap and a downstream end face of the rotating cylindrical chamber.

6. the upstream end seal has two openings communicating with the primary upstream port and two openings communicating with the secondary upstream port; 6. The rotary dispensing device of claim 5, wherein the downstream end seal has two openings communicating with the primary downstream port, two openings communicating with the secondary downstream port, and one opening communicating with the balancing port.

7. 7. The rotary dispensing device of claim 6, wherein the motor is configured to rotate the rotating cylindrical chamber in an intermediate position, one of the first, second, and third dispensing ports being aligned with the balancing port, another being aligned with the secondary upstream port and the secondary downstream port, and another being aligned with none of the primary upstream port and the primary downstream port, the secondary upstream port and the secondary downstream port, and the balancing port.

8. A rotary dispensing device according to any one of claims 1 to 7, wherein the rotating cylindrical chamber includes an upstream end face and a downstream end face on opposite sides of the rotating cylindrical chamber, and the first and second dispensing ports both extend from the upstream end face to the downstream end face.

9. 1. A method for transferring a precise amount of a known calibrant from a primary stream to a secondary stream to calibrate a detection system in said secondary stream, comprising:

9. A method comprising using a rotary dispensing device according to any one of claims 1 to 8, wherein the known calibrant is introduced into the primary upstream port and a dose of the calibrant is transferred to the secondary flow via the secondary downstream port.

10. 10. The method of claim 9, wherein the size of the calibrant of a dose can be varied to achieve multi-point calibration.

11. 1. A method for transferring a small, representative aliquot of a precise volume from a primary gas stream to a secondary gas stream for further processing and analysis, comprising: wherein the primary gas stream comprises at least a portion of combustion gases resulting from combustion of a sample to be analyzed, and the method further comprises:

11. A method comprising using a rotary dispensing device according to any one of claims 1 to 10, wherein the primary gas stream is introduced into the primary upstream port and a precise amount of the aliquot is transferred to the secondary gas stream via the secondary downstream port.

12. 12. The method of claim 11, wherein the aliquot size is variable.

13. 1. An elemental analyzer for analyzing elements in a gas sample, comprising: A rotary dosing device according to any one of claims 1 to 8; a sample source for providing a gas sample into the primary gas stream received at the primary upstream port of the rotary dispensing device; a carrier source for providing a carrier gas in the secondary gas stream received at the secondary upstream port of the rotary dispensing device; an analytical cell for receiving the secondary gas stream from the secondary downstream port and for analyzing the received secondary gas stream into which the gas sample is introduced by the rotary dispensing device.

14. 1. A rotary dispensing device comprising: A valve body; a rotating cylindrical chamber contained in the valve body, the chamber having an axial length; Opposite upstream and downstream end faces of the rotating cylindrical chamber; a first administration port extending from the upstream end surface to the downstream end surface; a second administration port extending from the upstream end surface to the downstream end surface; a third administration port extending from the upstream end surface to the downstream end surface; a primary upstream port for receiving a primary gas flow and for introducing the primary gas flow into one of the first, second, and third administration ports of the rotating cylindrical chamber; a secondary upstream port for receiving a secondary gas stream and for introducing the primary gas stream into one of the first, second, and third administration ports of the rotating cylindrical chamber; a primary downstream port for receiving the primary gas flow from one of the first, second, and third administration ports of the rotating cylindrical chamber; a secondary downstream port for receiving the secondary gas flow from one of the first, second, and third administration ports of the rotating cylindrical chamber; a balancing port; a motor for rotating the rotating cylindrical chamber, wherein each of the first administration port, the second administration port, and the third administration port sequentially: the primary upstream port and the primary downstream port for filling a dose of primary gas from the primary gas stream; the balancing port for balancing the dose of the primary gas; and the secondary upstream port and the secondary downstream port for transferring a dose of the primary gas to a secondary gas stream; a rotary dispensing device comprising a motor configured to align with the

15. when the second dose port is aligned with the primary upstream port and the primary downstream port for loading a second dose of primary gas from the primary gas stream; the first dose port simultaneously aligns with the equilibration port for equilibrating a first dose of primary gas; 15. A rotary dispensing device according to claim 14.

16. when the third dose port is aligned with the primary upstream port and the primary downstream port for loading a third dose of primary gas from the primary gas stream; the second dose port is simultaneously aligned with the equilibration port for equilibrating a second dose of primary gas; and wherein the first dose port simultaneously aligns with the secondary upstream port and the secondary downstream port for transferring a first dose of primary gas to the secondary gas stream.

15. A rotary dispensing device according to claim 14.

17. an upstream end cap secured to the upstream end of the valve body; a downstream end cap fixed to the downstream end of the valve body, A rotary dispensing device according to any one of claims 14 to 16, wherein the primary upstream port and the secondary upstream port are provided in the upstream end cap, and the primary downstream port, the secondary downstream port and the balancing port are provided in the downstream end cap.

18. an upstream end seal positioned between the upstream end cap and the upstream end face of the rotating cylindrical chamber; 18. The rotary dispensing device of claim 17, further comprising a downstream end seal positioned between the downstream end cap and the downstream end face of the rotating cylindrical chamber.

19. the upstream end seal has two openings communicating with the primary upstream port and two openings communicating with the secondary upstream port; 20. The rotary dispensing device of claim 18, wherein the downstream end seal has two openings communicating with the primary downstream port, two openings communicating with the secondary downstream port, and one opening communicating with the balancing port.

20. 20. The rotary dispensing device of claim 19, wherein the motor is configured to rotate the rotating cylindrical chamber in an intermediate position, one of the first, second, and third dispensing ports being aligned with the balancing port, another being aligned with the secondary upstream port and the secondary downstream port, and another being aligned with none of the primary upstream port and the primary downstream port, the secondary upstream port and the secondary downstream port, and the balancing port.

21. 1. An elemental analyzer for analyzing elements in a gas sample, comprising: A rotary dosing device according to any one of claims 14 to 20; a sample source for providing a gas sample into the primary gas stream received at the primary upstream port of the rotary dispensing device; a carrier source for providing a carrier gas in the secondary gas stream received at the secondary upstream port of the rotary dispensing device; an analytical cell for receiving the secondary gas stream from the secondary downstream port and for analyzing the received secondary gas stream into which the gas sample is introduced by the rotary dispensing device.

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