WO1995011440A1

WO1995011440A1 - Residual carbon analyzer

Info

Publication number: WO1995011440A1
Application number: PCT/DK1994/000389
Authority: WO
Inventors: Anders Sten Wedell
Original assignee: Anders Sten Wedell
Priority date: 1993-10-21
Filing date: 1994-10-21
Publication date: 1995-04-27
Also published as: AU7936994A; DK118493A; DK118493D0

Abstract

A residual carbon analyser for a heating or power plant has an analyser tube (16), preferably of glass, in which an ash sample from the flue duct of the plant, e.g. via a cyclone, can be led through its one end, be deposited in the analyser tube (16) and after a measurement can be blown away or back to where it came from, and whereby an air blast cone (1) has been arranged in the other end of the analyser tube with its top directed upwardly towards the inner of the analyser tube (16), said top forming a bottom for the ash sample in the analyser tube (16) and being shaped as a top cone (3) with a relatively acute top angle, e.g. 40°, and having a wall part of an annular passage or clearance (6) arranged at the lower end of the top cone (3), the largest diameter of said clearance wall part (6) being a minor percentage, e.g. 5,8 %, less than the inner diameter of the analyser tube (16), and which thus together with the analyser tube (16) forms an annular or ring shaped clearance or clearance, whereby the air blast cone (1) immediately below the wall part of the annular clearance (6) being shaped so that its wall parts together with the inner side of the analyser tube (16) form a downwardly closed annular chamber, to which pressurized air can be led in via one or more bores (4, 5 and 11) in the air blast cone (1), wherein said wall part (6) of the outer side of the air blast cone (1) forming the inner wall (6) of the annular clearance, is provided with a number of helical or inclined grooves or channels (2).

Description

RESIDUAL CARBON ANALYZER.

The invention relates to a residual carbon analyser for a heating or power plant and having an analyser tube, preferably of glass, in which an ash sample from the flue duct of the plant, e.g. via a cyclone, can be taken through its one end, be deposited in the analyser tube and after measurement can be blown away or back to where it came from, and whereby an air blast cone has been arranged in the other end of the analyser tube with its top directed upwardly towards the inner of the analyser tube, said top forming a bottom for the ash sample in the analyser tube and being shaped as a top cone with a relatively acute angle, e.g. 40°, and having a wall part of an annular passage or clearance arranged at the lower end of the top cone, the largest diameter of said clearance wall part being a minor percent¬ age, e.g. 5,8% less than the inner diameter of the analyser tube, and which consequently together with the analyser tube forms the annular or ring shaped clearance, whereby the air blast cone immediately below the wall part of the annular clearance being shaped so that its wall parts together with the inner side of the analyser tube form a ring shaped cham¬ ber being closed in its bottom, to which pressurized air can be let in through one or more bores in the air blast cone. A residual carbon analyser may be used for exam- ining whether uncombusted carbon is present in the flue gas from a heating plant and, if so, to which extent.

During removal of an ash sample flue gas with combustion ash is led from the flue duct of a heating or power plant to a cyclone top wherein ash and gas are sepa- rated. The gas is via a return pipe led back into the flue duct while the ash via a cyclone bottom part falls into the ash sample receiver in the form of the analyser tube and settles or is deposited on the top cone of the air blast cone. The filling up of the analyser tube should last pre- ferably at least three minutes; otherwise there might be a risk that the percentage of fly ash will be to large. When the analyser tube is filled, the analyzing measurement is made, e.g. by means of electromagnetic waves, which e.g. provides a colour measurement, the result of which is shown digitized on a measuring apparatus. After the analysis has been completed, pressurized air is led from below through the bores of the air blast cone and up through the ring shaped clearance between the air blast cone and the inner wall of the analyser tube. Thereby the ash is blown out from the analyser tube and via the cyclone parts and the return pipe blown back into the flue duct.

By the prior residual carbon analysers of this kind the air is blown up through the clearance in an axial direc¬ tion, and in some zones of the analyser tube chamber, espe- cially in the bottom thereof, the ash only with difficulty can be blown fully out. During the air blasts static electri¬ city may emerge, which delays a purification of the analyser tube, and furthermore the air blast cleaning operations may cause a certain wear on the analyser tube immediately above the air blast cone.

It is the purpose of the present invention to pro¬ vide a residual carbon analyser, whereby the pressurized air in shorter time can blow the analyser tube empty and blow it completely clean, so that more measurements or analyses can be made compared to the known residual carbon analysers, before the analyser tube shall be stripped down or removed and be replaced or cleaned internally.

This purpose is achieved with a residual carbon analyser according to the invention for a heating or power plant, said analyser being characterized in that the wall part of the outer side of the air blast cone forming the inner wall in the annular or ring shaped clearance, is provided with a number of helix shaped or inclining grooves or channels. Thus, dead zones from which ash is difficult to remove, are avoided, and less air blast errors occur, since the air being blown up through the clearance, will rotate around the top cone of the air blast cone and thus provide a faster and more efficient cleaning of the area between the top cone and the analyser tube compared to a known air blast cone in which the air leaves the clearance only in the axial direction.

Furthermore, it became evident that the development of static electricity and the difficulties in cleaning the analyser tube accrueing therefrom becomes less, and that the wear of the inner side of the analyser tube takes place over a longer time. Also by a blast air at a lower pressurized air pressure a satisfactory cleaning is obtained.

The remaining claims deal with suitable embodiments of a residual carbon analyser according to the invention.

By a residual carbon analyser according to claim 7 a particularly efficient cleaning effect is obtained, which is due to the fact that the pressurized air of the blast air is led obliquely from above and down to the annular passage chamber, and thus, together with the shape of the annular passage chamber, provides a strong turbulence in the air on its further way through the clearance.

The residual carbon analyser of the present inven¬ tion will now be described in more detail with reference to the drawing in which Fig. 1 shows a part of a power or heating plant in which the residual carbon analyser has been built in, Fig. 2 a side view of an air blast cone,

Fig. 3 a section through the longitudinal axis of the air blast cone, Fig. 4 a section in the air blast cone along I-I in Fig. 2, Fig. 5 a section along II-II in Fig. 2,

Fig. 6 a section along III-III in Fig. 2, and Fig. 7 a section along IV-IV in Fig. 2.

Fig. 1 shows a cyclone bottom part 14 which is secured to a cyclone top part. From the flue duct of a heat- ing or power plant flue gas containing the combustion ash is via a sampling nozzle arranged in the flue duct of the plant, led further on through a sampling pipe to the cyclone top part. Here the ash particles are separated from the gas and drop through the cyclone bottom part 14 and settle in a measuring or analyser tube 16, preferably a glass tube 16 arranged below the cyclone bottom part 14. In the lower end of the glass tube 16 is fastened an air blast cone 1, the top cone 3 of which forms the bottom for the ash sample in the glass tube 16. Between the air blast cone 1 and the glass tube 16 is arranged a narrow annular or ring shaped clear¬ ance, the outer wall of which is formed by the glass tube 16, and the inner wall of which is formed by a wall part 6 in the annular clearance of the air blast cone 1. Pressurized air can be led through the clearance and to the glass tube 16 interior. In an assay or test housing 15 is provided at least one opening 17, revealing a part of the glass tube 16, and through which opening ash particles in the glass tube 16 can be subject to measurements and analyses. Below the assay housing 15 and immediately below the glass tube 16 is fastened a bottom part 18 with an air inlet, such as a bore 19 which can be connected to a pressurized air source. In the bore 19 is arranged a transverse wall part with holes 20 for a flow of pressurized air from below. The wall part is provided with a centrally arranged helical hole serving for the fastening and possibly height adjustment of a helical rod 21 being screwed on to the bottom of the air blast cone 1. The assay housing 15 is surrounded by a transparent protec¬ tion cap 22. During sampling of an ash sample, the ash par¬ ticles having been separated in the cyclone top fall via the cyclone bottom 14 into the glass tube 16 and settle during the filling of the tube 16, essentially upon the top cone 3 of the air blast cone 1. After the measurement or analysis has been completed, all sampled ash particles are blown out from the glass tube 16 by means of pressurized air supplied from below, and e.g. further through the cyclone bottom 14, an outlet of the cyclone top, through a return pipe and an ejector nozzle back to the flue duct of the power or heating plant. The measurement and analysis is made by directing e.g. UV light on the ash particles in the glass tube 16. A digit- ized colour analysis or measurement may then show the extent to which uncombusted carbon particles might be present in the ash.

Fig. 2 shows the air blast cone 1 with the helical or inclined grooves 2 or channels 2 in that wall part of the air blast cone 1 forming the inner wall 6 in the ring shaped clearance between the air blast cone 1 and the glass tube 16. The grooves 2 or the channels 2 decrease in cross section from below and upwardly and becomes zero before they reach the lower edge of the top cone 3 of the air blast cone 1. Below the preferably cylindrical inner wall 6 the air blast cone has been shaped so as to form a downwardly closed space together with the glass tube 16, to which annular space pres¬ surized air can be led via borings 4, 5 and 11, cf. Fig. 3, in the air blast cone 1. Below the annular space or chamber the air blast cone 1 has a cylindrical part 9 which by means of a 0-ring arranged in an annular groove 10 is tightening the air blast cone against the glass tube 16. Between said cylindrical part 9 and the part 6 of the air blast cone forming the inner surface 6 of the annular passage, the air blast cone 1 is shaped as an upwardly tapering cone 8, the lower diameter of which corresponds to the diameter of the underlying cylindrical part 9. The top of the cone 8 is con¬ nected to a wall 7 being perpendicular to the longitudinal axis of the air blast cone 1 at the lower part of the inner surface 6 of the annular passage. Below the cylindrical part 9 carrying the O-ring, the air blast cone 1 is provided with a cylindrical part 12 which together with the glass tube 16 forms a annular channel 23, cf. Figs. 1 and 7, to which pres- surized air can be led from below and further through bores 4, 5 and 11, cf. Fig. 3, to the annular chamber and via the annular clearance is blown up into the glass tube 16.

Fig. 3 shows radial bores 11 leading from the annu¬ lar channel 23, to which pressurized air can be led from below, to an axial bore 4, which may bring the pressurized air further upwardly inside the air blast cone 1. The axial bore 4 is at its top connected to a number of bores, each of which having one generatrix in common with the cone 8, and which debouches in the wall 7 of the annular chamber, the wall 7 being perpendicular to the longitudinal axis of the air blast cone 1. Below the radial bores 11 the axial bore 4 has a part which is provided with a thread 13 for receiving the helical rod 21.

Fig. 4 shows a section along the line I-I in Fig. 2, and thus, it shows from below the wall 7 in the annular chamber being perpendicular to the axis of the air blast cone 1. Here six grooves 2 or channels 2 are shown, which grooves are present in that part of the air blast cone 1 forming the inner wall 6 in the annular clearance, and which starts at the wall 7 of the annular chamber. Furthermore, Fig. 4 shows the axial bore 4 and six bores 5 connecting the upper end of the axial bore 4 with the annular chamber.

Fig. 5 shows the same, however, in section along the line II-II in Fig. 2. However, the depth of the grooves 2 or the sockes 2 is less.

Fig. 6 shows with a section along the line III-III in Fig. 2 the axial bore 4 and six bores 5 which below debouch in the annular chamber, and which at the top are connected to the axial bore 4.

Fig. 7 shows with a section along the line IV-IV in Fig. 2 four radial bores 11, connecting the annular channel 23 to the axial bore 4.

Claims

C l a i m s .

1. Residual carbon analyser for a heating or power plant and having an analyser tube (16), preferably of glass, in which an ash sample from the flue duct of the plant, e.g. via a cyclone, can be led through its one end, be deposited in the analyser tube (16) and after having been measured can be blown away or back to where it came from, and whereby an air blast cone (1) has been arranged in the other end of the ana¬ lyser tube with its top directed upwardly towards the inner of the analyser tube (16), said top forming a bottom for the ash sample in the analyser tube (16) and being shaped as a top cone (3) with a relatively acute top angle, e.g. 40°, and having a wall part of an annular passage or clearance (6) provided at the lower end of the top cone (3), the largest diameter of said clearance wall part (6) being a minor per¬ centage, e.g. 5,8%, less than the inner diameter of the ana¬ lyser tube (16), and which thereby together with the analyser tube (16) forms an annular or ring shaped clearance, whereby the air blast cone (1) immediately below the wall part of the annular clearance (6) is shaped so that its wall parts toget¬ her with the inner side of the analyser tube (16) form a downwardly closed annular chamber, to which pressurized air can be led in through one or more bores (4, 5 and 11) in the air blast cone (1), characterized in that said wall part (6) of the outer side of the air blast cone (1) forming the inner wall (6) in the annular clearance, is provided with a number of helical or inclined grooves (2) or channels (2).

2. Analyser according to claim 1, characterized in that the grooves or the channels (2) have a depth decreasing from below and upwards.

3. Analyser according to claim 2, characterized in that the depth of the channels becomes zero before reaching the lower edge of the top cone (3) of the air blast cone (1).

4. Analyser according to claim 3, characterized in that the grooves (2) or the channels (2) have an inclination of about 20°, a width of about 0,8% and a initial depth at the lower edge of the clearance of about 1% of the largest diameter of the air blast cone (1) .

5. Analyser according to any of the preceding claims, characterized in that the air blast cone (1 ) below the annular chamber is shaped as a cylinder (9), which at its outer side has an annular groove (10) for an 0-ring tigh- tening against the inner side of the analyser tube (16).

6. Analyser according to any of the preceding claims, characterized in that the air blast cone (1) below the cylindrical part (9) carrying the 0-ring, has a cylindrical part (12), which together with the analyser tube (16) form a channel for the supply of pressurized air, that the air blast cone (1) has a number of preferably radial bores (11) leading from the channel to an axial bore (4), which in its other end is connected to a number of bores (5) leading to the annular chamber below the clearance, and the total area of the bores (9) being larger than the area of the axial bore (4).

7. Analyser according to claim 6, characterized in that the side surface of the air blast cone (1) limiting the annular chamber below the clearance, is shaped as a cone (8), and that the bores (5) leading from the axial bore (4) in the air blast cone (1) and to the annular chamber below the clear¬ ance, are so drilled that a drill will be tangent to and extend parallell to a generatrix of the cone (8), and that the air blast cone (1) outside the upper edge of the cone (8) is provided with a wall (7), which essentially is perpendi- cular to the longitudinal axis of the air blast cone ( 1 ), and in which the bores (5) debouch.

8. Analyser according to claims 6 and 7, characterized in that the axial bore (4) of the air blast cone (1) is extend- ing below the preferably radial bores (11) and provided with a thread (13) for a helical rod (21) for fastening and pos¬ sibly height adjusting the air blast cone (1) on a bottom part (18) arranged below the analyser tube (16), which bottom part (18) is also adapted as a supply part for a pressurized air source.