LANCE FOR A GAS ANALYSIS SYSTEM

Abstract

A gas sampling lance with a gas sample pipe for sampling gases wherein the gas sample pipe is divided in a lance pipe and a connecting pipe which connects the lance pipe to a gas scrubber, a first scraper to clean the inside of the lance pipe and a second scraper to clean the inside of the connecting pipe.

Claims

1. A gas sampling lance comprising a gas sample pipe for sampling gases, wherein the gas sample pipe is divided in a lance pipe and a connecting pipe which connects the lance pipe to a gas scrubber, a first scraper to clean the inside of the lance pipe and a second scraper to clean the inside of the connecting pipe.

2. The lance according to claim 1, wherein the first and/or second scraper comprises a cylinder with a piston, a piston rod and a scraper element attached to the piston rod and wherein the respective scrapers are mounted in line with respectively the lance pipe and the connecting pipe.

3. The lance according to claim 1, wherein the first and/or second scraper comprises an electric motor driving a spindle guided in a housing and/or a linear motor driving a rod guided in a housing with a scraper element attached to the spindle or the rod and wherein the respective scrapers are mounted in line with respectively the lance pipe and the connecting pipe.

4. The lance according to claim 1, wherein the lance pipe and the connecting pipe are positioned such that the heart lines of the lance pipe and the connecting pipe intersect.

5. The lance according to claim 1, wherein the length of stroke of the first or second scraper extends from a start point at one side of where the lance pipe and the connecting pipe connect to respectively an end point at or near the end of the lance pipe or the connecting pipe at the opposite side of where the lance pipe and the connecting pipe connect.

6. The lance according to claim 1, wherein the scraper elements are ceramic or bronze scraper elements.

7. The lance according to claim 1, wherein at least one inlet for a cooling medium is provided with which the piston rod and/or scraper element of at least one scraper is cooled.

8. The lance according to claim 2, wherein the lance pipe, the connecting pipe, the cylinder or housing of the first scraper and the cylinder or housing of the second scraper are connected by a connecting member.

9. The lance according to claim 8, wherein the at least one inlet for the cooling medium is provided in the connecting member.

10. The lance according to claim 9, wherein the at least one inlet for the cooling medium connects to a recess provided in the connecting member and wherein the recess encloses at least part of one piston rod between the location where the lance pipe and the connecting pipe connect and the cylinder associated with the piston rod.

11. The lance according to claim 9, wherein the recess is provided with a drain and wherein the drain connects to the connecting pipe downstream of the location where the lance pipe and the connecting pipe connect.

12. The lance according to claim 1, wherein the cooling medium to cool the piston rod and/or scraper element of at least one scraper is supplied as a mist.

13. The lance according to claim 1, wherein the cylinder of the first and/or second scraper is a gas driven cylinder.

14. The lance according to claim 12, wherein the cylinder of the first and/or second scraper is a Nitrogen-gas or an inert gas driven cylinder.

15. The lance according to claim 1, wherein the lance pipe is provided at the outside with a cooling jacket with an inlet and outlet for a cooling medium for the lance pipe.

16. The gas scrubber with a lance according to claim 1 with a mist chamber and a gas cleaning chamber, wherein the connecting pipe of the lance connects to the mist chamber and the gas cooling chamber to the gas cleaning chamber.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The invention will be further explained by means of the example shown in the drawing, in which:

[0036] FIG. 1 shows a gas sampling lance and a mist chamber attached thereto in cross-section and an enlarged view of a connecting member;

[0037] FIG. 2 shows a gas cleaning chamber, and

[0038] FIG. 3 shows a drain system that connects to the cleaning chamber.

DETAILED DESCRIPTION OF THE DRAWINGS

[0039] In FIG. 1 a gas sampling lance 1 is shown provided with a lance pipe 2, a connecting pipe 3, a connecting block 4, a first and second cylinder 5,6 with respectively a first and second scraper 7,8 and a mist chamber 9.

[0040] The lance pipe 2 is provided at the outside with a cooling jacket 10 with an inlet 11 and outlet (not shown in the drawing) for a cooling medium for the lance pipe 2. The cooling jacket 10 is necessary to provide sufficient cooling of the lance pipe 2 for the part of the lance pipe that enters the vessel or duct but typically also for the downstream part outside the vessel or duct since the temperature of the sampled gas will not drop considerably inside the lance pipe 2.

[0041] The lance pipe 2 connects to the connecting member 4 in a manner that it can be easily be replaced for instance by bolting the lance pipe 2 to the connecting block 4.

[0042] The lance pipe 2 and the connecting pipe 3 connect by means of channels provided in the connecting block 4 that are in line with lance pipe and connecting pipe. These channels with the lance pipe 2 and connecting pipe 3 form together the gas sample pipe.

[0043] The channels in the connecting block extend beyond the spot where the lance pipe 2 and connecting pipe 3 connect through the connecting block 4 to the outside faces of the connecting block 4. These extended channels form the respective points of entry for first and second scraper 7,8. The first and second cylinder 5,6 of first and second scraper 7,8 are mounted on the connecting block by means of bolts or the like such that these cylinders and/or parts of the cylinders can be replaced easily when necessary.

[0044] The first and second scraper 7,8 comprise a piston 12,13, a piston rod 14,15 connected to the respective pistons 12,13 and a scraper tip 16,17 at the end of each of the piston rods 14,15. The extended channels in connecting block 4 widen at their respective outer ends to form recesses 18,19. In the most retracted position of the scrapers 7,8 the scraper tips 16,17 are at least partially in the respective recesses 18,19.

[0045] The recesses 18,19 are each provided with an inlet 20,21 which connect to a supply of cooling medium such as atomized water. The use of a liquid medium that is sprayed as a mist provides sufficient cooling whereas the total volume of the cooling medium can be kept at a minimum. This is important because the used cooling medium is drained through the scrubber connected to the gas sampling lance 1 which is only capable of handling a certain maximum volume of liquid medium.

[0046] Recess 18 is provided with a drain channel 22 which connects the recess with the connecting pipe 3. A similar drain could be provided for the other recess 19 which, however in the shown embodiment is not necessary because of the vertical or about vertical position of scraper 8 and connecting pipe 3 and the smaller length of connecting pipe 3 compared to that of lance pipe 2. The cooling medium used in recess 19 flows in downward direction either directly along the scraper tip 17 into connecting pipe 2 or indirectly by first flowing into the lance pipe 3 and then into connecting pipe 2. The diameter of the scraper tips 16,17 are taken smaller than the diameters of the respective pipes to prevent that the scrapers 16,17 could get stuck in the pipes because of thermal expansion of the scrapers and or pipes. This gives sufficient play to drain the cooling medium from recess 19 through the connecting pipe 2.

[0047] In the mist chamber 9 the sampled gas is cooled by means of a cooling medium supplied to the cooling chamber 9. Also in the cooling chamber typically an atomized liquid is used to cool the sampled gas. The mist chamber is provided with inlets 23 to supply a mist of cooling medium into the sampled gas in the chamber. At the lower end of the mist chamber 9 a grid 24 is provided to prevent that accretions fall into outlet 25 of the mist chamber and cause blockage of the scrubber system.

[0048] The mist chamber 9 connects through outlet 25 with inlet 26 of gas cleaning chamber 27. In FIG. 2 the gas cleaning chamber is at least partially filled with glass beads and is provided with an inlet 28 for a cleaning liquid for which water can be used and an outlet 29 for cooled and cleaned sampled gas. In the outlet 29 a float 30 is provided which closes gas outlet 29 in case too much cooling and/or cleaning liquid has come into the gas cleaning chamber 27. In that way it is prevented that any liquid could come in the downstream system with the gas analysis equipment.

[0049] The water is sprayed over the glass beads and the sampled gas in between the glass beads and leaves with the collected dust the gas cleaning chamber 27 through outlet 27, drain pipe 32 and is collected in container 33. Since the gas sampling is driven by applying a pressure lower than atmospheric pressure the drain pipe 32 is taken long enough to prevent that liquid could be forced back into the gas cleaning chamber 27 by the higher atmospheric pressure.

[0050] In operation gas is drawn in the gas sample pipe because of the pressure in the system which is by means of a suction pump kept below atmospheric pressure and below the pressure in the vessel or duct from which the gas is to be sampled. With the sampled gas dust is carried along into the gas sample pipe which will adhere to the walls of the gas sample pipe. To prevent clogging the dust adhered to the walls is periodically removed by operating the scrapers. Most of the dust will adhere to the wall of the lance pipe 2. To remove the dust the scraper 7 is moved from the start position over the length of the lance pipe 2 to the end of the lance pipe therewith pushing most of the dust back into the vessel or duct. Part of the dust might remain on the wall and part of the dust might be pushed in the other direction when retracting the scraper back to its start position. That part of the dust might come in the connecting pipe and/or in the recess 18. The dust ending up in the connecting pipe 2 is in its turn removed by the second scraper 8 which moves from its start position to the end of the connecting pipe 2 and back again. Part of the dust that comes into the recesses is removed by means of the liquid mist used for the cooling of the scraper tips and piston rods and will be taken into the gas cooling chamber 9.

[0051] The scrapers are typically used in succession with firstly the first scraper 7 and secondly the second scraper 8. The scrapers can be moved to and fro relatively rapidly with the gas driven cylinders such that the flow of sampled gas will hardly be disturbed. By moving the piston at a certain speed and at a certain time interval the temperature increase of the scraper tip and piston rod because of the hot environment and hot gas can be kept at a minimum.

[0052] During the scraping operation the otherwise open connection with the duct or vessel is temporarily blocked, but the volume of gas present in the mist chamber and the cleaning chamber provides a sufficient large gas buffer to continuously suck gas to the gas analysers.