GB2451279A

GB2451279A - Apparatus for gas sampling comprising an inert gas atmosphere in the region of the port

Info

Publication number: GB2451279A
Application number: GB0714564A
Authority: GB
Inventors: Ian Mcdonald
Original assignee: Siemens VAI Metals Technologies Ltd
Current assignee: Primetals Asset Management UK Ltd
Priority date: 2007-07-26
Filing date: 2007-07-26
Publication date: 2009-01-28
Anticipated expiration: 2027-07-26
Also published as: GB0714564D0; GB2451279B

Abstract

Apparatus suitable for gas sampling comprises a housing 2a, a probe 1 arranged to pass through a port 3 in the housing and means for providing an inert gas atmosphere adjacent to the port 10 at greater pressure than the exterior of the housing. The apparatus may comprise chamber 10 which is supplied inert gas via a conduit 8. The apparatus may comprise a piston 4 arranged to push the probe 1 through the port 3 to an operating position. The piston may be a pneumatic piston operated by inert gas. The piston and the chamber may be pressurised and depressurised independently of one another. The surface of the port (12) may be tapered and may comprise a disposable insert in the housing. The probe may measure gas temperature and pressure and may be used to collect furnace gas for subsequent analysis. The apparatus may be suitably used with nitrogen gas and may be useful in the sampling of gases in dirty environments (e.g. a blast furnace). The apparatus may solve the problem of dirt and grit contaminating the probe.

Description

1 2451279 Remote Gas Sampling Cartridge The invention is concerned with sampling of gases, particularly in dirty environments such as blast furnaces.

The use of gas sampling devices in blast furnaces is known.

Monitoring of gas composition, temperature and pressure are increasingly necessary to the efficient operation of blast furnaces and gas sampling devices are commonplace in

the field.

Typically, a sampling probe is mounted in the end of a lance, the latter being suitable for insertion through the wall of the furnace. Once the lance is inserted, the sampling probe is caused to emerge from the lance (typically by a pneumatic cylinder) and effect the necessary measurements.

In addition to the measurement of parameters such as gas temperature and pressure, the probe may also be used to collect furnace gas for subsequent analysis.

A common problem encountered in the prior art arises from the high levels of dirt and grit typically encountered in the environments in which these instruments are required to operate. Contamination of moving parts such as the sampling probe gives rise to increased wear through abrasion and can lead to seizing of components. The present invention addresses these problems.

According to the invention, gas sampling apparatus comprises the features set out in claim I attached hereto.

The invention will now be described, by non-limiting example, with reference to the appended figures in which: figure 1 shows a schematic representation of a sampling probe arrangement of the prior art; figure 2 illustrates in more detail, some of the components of figure 1; figure 3 illustrates a sampling probe arrangement according to the invention and figure 4 shows in detail, some preferred features of the invention.

In the figures, like components appearing in more than one figure are labelled with the same numeral.

Referring to figure 1, a gas sampling probe 1, of the type typically used to monitor gases in a blast furnace, is mounted in a housing 2a incorporated in the end of a lance 2 (partially shown) and is arranged to pass through a port 3 from the interior to the exterior of the housing 2a. A pneumatically driven piston 4 located in cylinder 5 causes the probe to emerge from the housing 2a to an operating position when the cylinder 5 is pressurised by nitrogen introduced via conduit 6. A return spring 7 causes the probe to withdraw back into the housing when the pressure in cylinder 5 is released.

The probe 1 typically includes measuring devices such as a thermocouple junction and a pressure transducer (not shown) and a second conduit 8 from the tip of the probe 1 directs gas to collection means (e. g sample bottles, not shown) for subsequent analysis.

When the housing is located in the blast furnace, or other dirty environment, dirt and grit etc are able to ingress through the port 3 due to small gaps 9 around the probe 1.

(Figure 2 shows the detailed components around the port where the gaps 9 are exaggerated for clarity). In particular, dirt etc may deposit on the surfaces of the probe and then penetrate gap 9 as the probe is withdrawn into housing 2a. Such dirt can cause damage by abrasion and sticking of moving parts.

While the lance is inserted in the blast furnace, the pressure in the interior of the housing will tend towards that of the blast furnace (typically about 3 bar) at least in part because the gap 9 provides fluid communication therewith. A pressure of about 7 bar is applied to the cylinder 4 to cause the probe to emerge.

Referring to figure 3, in a probe housing 2a according to the invention at least part of the interior of the housing, particularly the region adjacent the port, is maintained in an atmosphere of nitrogen or other inert gas at a greater pressure than that of the blast furnace. In the embodiment shown, this is achieved by defining a chamber 10 adjacent the port and pressurising the chamber with nitrogen. The nitrogen supply used to drive piston 4 may conveniently be used to provide a chamber pressure of about 7 bar, but in such an arrangement, it is preferable that the pressure in the chamber 10 can be maintained independently of the pressure in the cylinder 5. The design of a system having such a feature is within the capabilities of a person skilled in the art.

It should be noted, however, that the invention is not limited to apparatus that uses a pneumatic cylinder to move the probe. In apparatus using other means (for example electromechanical devices) the invention may nevertheless be worked by providing the source of inert gas at a suitable pressure.

Moreover, it is not essential to include a separate chamber to be pressurised: the whole of the interior of the housing 2a could be pressurised but, by including the chamber, it is possible to pressurise only the region of the housing interior that is essential to the invention (i.e. that which is adjacent the port) thereby reducing the amount of nitrogen used.

The effect of this pressurised atmosphere is to provide a purge of nitrogen (or other inert gas) from the interior of the housing, through gaps 9 and thereby to prevent or reduce the ingress of dirt etc. By allowing the chamber 10 to be pressurised independently of the cylinder, it is possible to maintain the nitrogen purge during and after withdrawal of the probe back into the housing. In the non-operative (withdrawn) position, the probe end would typically be flush with the end of the housing.

A secondary benefit of the pressurised atmosphere in chamber 10 is that return spring 7 is assisted during withdrawal of the probe.

Figure 3 also illustrates how thermocouples 11 may be included at various depths in the body of the housing in addition to, or as an alternative to, the thermocouple located on the probe end.

Referring to figure 4, in a preferred embodiment of the invention, the surface 12 of port 3 is tapered so that gap 9 is greater on the interior side of the port (relative to the housing 2a) than on the exterior side. This enhances the purging effect of the pressure differential across the port on dirt that entered gap 9.

By another preferred feature, the port 3 is realised in a replaceable insert 13 which can be retained in the housing 2a by, for example, screw threading. By this feature, wear or damage to the port can be rectified by simple replacement of a consumable item rather than a larger item.

Claims

Claims 1. Apparatus for gas sampling comprising: a housing; a probe arranged to pass through a port in the housing and means for providing an atmosphere of inert gas in the region of the interior of the housing adjacent the port, at greater pressure than the exterior of the housing.
2. Apparatus according to claim I including a chamber inside the housing, wherein the port extends from the exterior of the housing to the chamber, and further including means for supplying inert gas to the chamber to a pressure greater than the exterior of the housing.
3. Apparatus according to claim 2, further including: a pneumatic piston arranged to push the probe through the port to an operating position; a source of pressurised inert gas and means for supplying inert gas from the source to the piston and to the region of the interior of the housing adjacent the port.
4. Apparatus according to claim 4, where the piston and the chamber may be pressurised and depressurised independently of each other.
5. Apparatus according to any preceding claim, where the surface of the port is tapered from the exterior to the interior of the housing.
6. Apparatus according to any preceding claim, where the port is realised in a disposable insert arranged to be inserted and retained in the housing.
7. A method of sampling gas comprising the steps of: extending a sampling probe through a port from the interior of a housing to the environment of the gas, characterized by the step of providing an atmosphere of inert gas in the region of the interior of the housing adjacent the port, at a pressure greater than the environment of the gas.