GB2127174A

GB2127174A - Periscope for high-temperature reactor

Info

Publication number: GB2127174A
Application number: GB08322291A
Authority: GB
Inventors: Hans-Lutz Beuermann; Roland Bianchin; Werner Franke; Christian Riedel; Manfred Schingnitz; Peter Gohler; Eberhard Claussnitzer; Rolf Grosse
Original assignee: Brennstoffinstitut Freiberg
Current assignee: Brennstoffinstitut Freiberg
Priority date: 1982-09-14
Filing date: 1983-08-18
Publication date: 1984-04-04
Also published as: JPS5981613A; HU191880B; GB2127174B; GB8322291D0; FR2533036A1; DE3316167A1; CS256907B1; DD219059A3; YU184583A; SU1636643A1; CS352983A1; AT394277B; ATA172183A; DE3316167C2

Abstract

The wall (3) and lining (4) of the combustion chamber (5) of a high-temperature, high pressure reactor is penetrated by a water- cooled housing (1) in which there is coaxially disposed an optical system (2) so that scavenging gas can be passed through a gap (8) between the optical system (2) and the housing (1) into the chamber (5) over a diffuser surface (19) to keep clear the front lens (11) of the optical system. In accordance with the invention a hollow frusto-conical element (12) has the lens (11) fitted in its larger- diameter end, its narrower-diameter end providing a light-admission aperture (13), nearer the chamber (5). The rear part of the wall of the element (12) has openings (17) through which scavenging gas can enter the element (12) to exit from the aperture (13) surrounded by scavenging gas passing through the frusto-conical gap (16) between the element (12) and housing (1). <IMAGE>

Description

SPECIFICATION Periscope for high-temperature reactor This invention relates to a periscope for the transmission of optical signals from the reaction chamber of a high-temperature reactor or for the visual observation of processes in such a reactor.

The invention is particularly intended for reactors in which flame reactions take place at high pressures. Preferred fields of application are reactors for high-pressure gasification of pulverised fuels, reactors for the production of synthesis gas by partial oxidation of liquid or gaseous hydrocarbons under pressure, and pressure combustion chambers of gas turbines or combined power stations.

In some processes for the production of synthesis gas from solid fuels, coal dust and industrial oxygen are converted in a flame reaction into a gas rich in CO and H2. The gas temperatures occurring after completion of the conversion are above the melting point of the mineral components of the fuel so that liquid clinker is formed. For example, a typical final reaction temperature is 1 500 C, temperature peaks of 2000"C and over being liable to occur in the flame. Gasification in many cases takes place at pressures of 0.5 to 5 MPa. The same basic principle applies to the production of synthesis gas by the partial oxidation of liquid and gaseous hydrocarbons, where pressures of maximum 10 MPa are usual.The monitoring of the process in such reactors necessitates the transmission of optical signals from the interior of the reaction chamber, in order to determine the temperatures prevailing in the chamber and to monitor the existence of a flame. Furthermore, it is of advantage when processes taking place in the reaction chamber, such as the development of the flame or the clinker flow at the wall of the reaction chamber or in the discharge outlet for the clinker, can be visually monitored, i.e.

either by direct observation or through television. DE OS 22 62 351 and DE OS 29 15 926 describe means of observing pressure gasification reactors, when one opening in the reactor wall is provided with a pressure-proof inspection glass and can be scavenged with a suitable scavenging gas (inert gas or recycled synthesis gas produced by the reactor itself).

Owing to the unavoidably great distance between the inspection glass and the reaction chamber, as a result of the refractory lining of the reactor or the installation of internal cooling walls for the reaction chamber, the angle of visibility in the reaction chamber is very limited. It is limited still further by the extremely intensive radiation from the reaction chamber, which necessitates relatively small opening diameters, in order to prevent any overheating of the inspection socket.

The most serious drawback of this and similar known arrangements, however, is that the inspection opening, despite scavenging, is often partially or completely covered by deposits of clinker. To remove such deposits from reactors operating at high pressures, the reactor has to be shut off and relieved.

Among further known means of observation are those of the periscope type, e.g. for steam generators, glass-melting furnaces and metallurgical furnaces, where a lens system, mounted in a water cooled housing, is additionally protected by a scavenging gas against the ingress of hot gases and contamination. The advantage of such periscopes is their relatively large visibility angle, e.g. 50 .

The known technical solutions, however, are only suitable for plant operating at standard pressures. This type of observation means also corresponds to that described in DD WP 76 055, where a lens system is positioned axially in a double-pipe water jacket, a flow of scavenging gas and cooling gas being maintained between the lens system and the water jacket. In front of the first lens of the objective, as viewed from the combustion chamber, is a conical confusor through which the scavenging gas flows into the combustion chamber. The aperture of the confusor acts simultaneously as a diaphragm for the optical system, while the ratio of the distance between the said aperture and the first lens of the objective to the diameter of said lens determines the visibility angle.Furthermore, similar arrangements are known where the confusor aperture is followed by a diffuser the angular aperture of which is so dimensioned that the visibility angle is not restricted.

Practice has shown that if the operating principle of known periscopes, which are used for the observation of furnace chambers operating at standard pressures, is simply transferred to the optical monitoring of the reaction chamber of, for instance, entrainment gasification reactors operated at high pressures, the desired results cannot be obtained by simply arranging the pressure-proof inspection glasses and lenses in a suitable manner. After a relatively short period of time deposits of clinker tend to occur on the end face of the periscope, and gradually increase in such a way that the optical path is restricted and finally interrupted.Moreover, it has been found that, although a relatively large quantity of scavenging gas was used, highly volatile mineral components, even elementary sulphur, sublimate at the diffuser of the scavenging gas outlet and at the objective and thus impair the serviceability of the periscope likewise.

A principal object of the invention is to provide a periscope for the transmission of optical signals from the reaction chamber of a high-temperature reactor which will be suitable for use in reactors operating at high pressures and particularly for use in reactors for the pressure gasification of pulverised fuels, without any deposits of clinker and impurities occurring.

According to the invention there is provided a periscope for the transmission of optical signals from the reaction chamber of a high temperature reactor, comprising an optical system arranged co-axially in a tubular housing penetrating a wall of the chamber so that a light-entry end of the optical system is nearer to the chamber, there being an annular clearance between the housing and the optical system which opens into the chamber and through which scavenging gas under pressure may be passed into the chamber, wherein there is positioned co-axially within the housing in front of the optical system a hollow, frusto-conical element the narrower-diameter end of which is nearer to the chamber and provides the light-admission aperture of the optical system, the portion of the housing which surrounds said element being internally frusto-conical with a taper angle equal to or greater than that of said element so that the annular gap between said portion of the housing and said element is of constant width or of a width which decreases toward the chamber, said element being provided in a region nearer to the optical system with openings to admit scavenging gas from said annular gap into said element, the aggregate area of said openings being a multiple of the area of said aperture.

This arrangement ensures that some of the scavenging gas passing through said annular gap flows through said openings into the internal space of the hollow element and thence through the said aperture into the reaction chamber, and that the remainder of the scavenging gas flows through the annular gap and surrounds the scavenging gas jet coming from said aperture.

Unlike known systems the otherwise inevitable return-flows in the vicinity of or in the centre of a gas jet emerging from an opening are, by the present invention, prevented in that the gas jet coming from the aperture is enveloped by the jet emerging from the annular gap. This prevents viscous, adhesive particles of clinker or mineral vapours being carried by return-flows toward the aperture and forming deposits thereon.

Said openings may penetrate the element obliquely with respect to radial planes so that scavenging gas entering said element is caused to swirl before emerging from said aperture, or said openings, similar and symmetrically disposed around said element, may each have the form of an incomplete ellipse such that the opening has a longer arm and a shorter arm originating from a vertex at the nearest point of said opening to the widerdiameter end of said element.

A narrower-diameter end region of said element may be externally cylindrical, the cylindrical surface merging continuously and without a step with the frusto-conical surface.

The said annular gap may open toward the chamber via a circular array of equiangularly spaced apertures, and these may be provided between flanges on the narrower-diameter end of said element which serve to locate the latter within the housing.

The ratio between the cross-sectional area of the free space of said aperture and of said annular gap where the latter opens toward the chamber is preferably in the range 1:0.7 to 1:2, and is preferably 1:1.

The optical system may comprise a front lens nearest to the combustion chamber of diameter equal to the inner diameter of the larger-diameter end of said element and fitted therewithin, the ratio of the diameter of said aperture to that of said front lens being in the range 1:5 to 1:8.

The housing may have an end portion extending from said element toward the chamber, the bore of which widens over a curve to form a diffuser, the radius of said curve being so chosen that the housing does not obstruct light passing from the chamber through said aperture to the optical system.

Said housing is preferably water-cooled.

Preferred embodiments of the present invention will now be described with reference to the accompanying diagrammatic drawings, in which: Figure 1 illustrates in longitudinal section a periscope for a high-temperature reactor, Figure 2 is a partial cross-sectional view on an enlarged scale taken on the line A-A of Fig. 1, Figure 3 is a front view of the periscope, Figures 4A and 4B illustrate a frusto-conical element with part-elliptical openings, and Figure 5 is a simplified view on an enlarged scale similar to the left-hand portion of Fig. 1 and on a larger scale.

The periscope shown in Fig. 1 is intended for the transmission of optical signals from the reaction chamber of a reactor for the gasification of coal dust at a pressure of 3 MPa. The temperature in the reaction chamber is in excess of 1 500 C, the atmosphere in the reaction chamber being contaminated by incompletely gasified particles of coal dust and drops of clinker.

The periscope comprises a tubular housing 1 in which there is coaxially disposed an optical system 2 which consists of a series of lenses. The periscope passes through an opening in the reactor wall 3 and through a refractory lining 4 to the reaction chamber 5 and is connected in a pressure-proof manner by a flange 6 to the reactor wall. The periscope is provided at one end with a pressureproof window 7, for example a pressure-proof and especially thick lens of the optical system.

Between the optical system 2 of the periscope and the housing 1 there is a clearance 8 with a scavenging gas socket 9 connected to a scavenging gas source (not shown) of which the supply pressure is about 3.5 MPa, i.e.

higher than the pressure in the combustion chamber. Compensation openings 10 provide for pressure compensation between the clearance 8 and the internal space of the optical system 2 of the periscope.

A hollow element 1 2 having the shape of a thin-walled hollow truncated cone has the front lens 11 of the optical system fitted with its wider-diameter end. The taper angle of the element 12, i.e. the angle between any point on its periphery and its axis, is equal to 25 .

This ensures a visibility angle of 50 into the reaction chamber. With an optically efficient diameter for the front lens of 20mm the internal diameter of the narrower-diameter end of the element 1 2 providing an aperture 1 3 for the optical system is 3mm.

That part 1 4 of the interior of the housing 1 which surrounds the element 1 2 is also frustoconical, the angle being likewise 25 . The clearance 8 in this region therefore constitutes a conical gap 1 5 which forms an annular nozzle 1 6 at the end facing towards the reaction chamber 5. In the region of this annular nozzle the outside of the element 1 2 changes smoothly and without a step into a cylindrical portion, as shown in Fig. 4. Integral flanges 1 8 serve for centering the element 1 2 within the housing 1 and also subdivide the annular nozzle 1 6 into a multitude of individual openings 16' in a circular array.

Through the annular nozzle 1 6 one part of the scavenging gas, which is fed via the scavenging gas socket 9, enters the reaction chamber. The other part of the scavenging gas flows into the internal space of the element 1 2 via openings 17, in the form of four ports penetrating the wider half of the element 1 2 nearer the front lens 11. The arrangement of the ports is shown in Fig. 2.

The arrangement of the ports 1 7 obliquely with respect to radial lines ensures a swirling flow of the scavenging gas through the aperture 1 3 into the reaction chamber 5. The aggregate area of free space at the annular nozzle 1 6 is 8 mm2. The aggregate area of free space in the ports 1 7 totals about 30mm2.

Where it extends beyond the nozzle 1 6 toward the reaction chamber 5 the interior of the housing 1 widens over a curve so that downstream of the nozzle 1 6 the curved surface forms a diffuser 1 9 and finally the end face 20 of the periscope. The radius R of the curve is selected to ensure that the visibility angle into the reactor is not restricted. As shown in Fig. 5, this means that the surface of the diffuser 19 is kept outside the cone 21 bounding light passing to the front lens 11 through the aperture 1 3.

The housing 1 of the periscope is watercooled and provided with sockets 22 for the supply and discharge of cooling water. A deflector plate 23 arranged in the water-containing space of housing 1 ensures that cooling water is supplied to the end face 20 and the diffuser 19, which are subjected to a particularly high thermal stress, and that sufficient cooling-water flow rates are obtained.

The trumpet shape of the diffuser 1 9 and the rounded end face 20 are most suitable for intensive cooling.

Being provided with a quantity of scavenging gas of about 30 m3/h under standard conditions or about 1 m3/h under operating conditions, the periscope, when operated continuously, will be kept free from deposits of clinker and dust which would restrict the visibility angle or reduce the transparency of the optical system. With an apparatus according to the prior art, which has a tapered housing (without a hollow element 12) and a flat end face and which has the same aperture diameter of 3mm and approximately the same throughput of scavenging gas, the operating period is only 6 to 1 2 hours before the optical path is almost completely interrupted by clinker deposits and impurities.

In the modification of the invention shown in Figs. 4A and 4B, the openings 1 7 in the element 1 2 each lie on part of an ellipse.

Each opening 1 7 has limbs 25' and 25" of different length which meet at a vertex 24 which is the nearest point on the opening to the wider-diameter end of the element 1 2.

There are two such openings 1 7 arranged in a rotationally symmetrical manner about the element 1 2 as is apparent from Fig. 4B.

The different lengths of the two limbs 25' and 25" of each opening ensure a swirling of movement of scavenging gas in the internal space of the element 1 2 similar to that obtained by the obliquely arranged openings described in connection with Fig. 2. The same favourable operating conditions for the periscope are thus achieved.

The advantage of this embodiment is the simpler manufacture of the openings 17, which may be cut by means of a thin cylindrical cutter. In this case the cutting plane of the cutter is inclined in respect of the axis of the element 1 2 by an angle of 45 , while the axis of the cutter is situated in a plane parallel with the axis of the element 12, the distance between said axis and the cutter axis being 12 mm.

As shown, the optical system 2 of the periscope consists of a lens system and optical signals will be transmitted outwards through the pressure-proof window 7. The invention will nevertheless be similarly applicable if, instead of a lens system, a light guide or image conduit is used entirely or partially as an optical system for the periscope. In this case, the term "front lens" used in the above description corresponds to the light entry area of the light guide or image conduit.

It is also possible to install within the periscope a suitable sensor (e.g. phototransistor) or a video camera, which converts the optical signals received from the optical system of the periscope into electrical signals which are transmitted onwards by means of a suitable cable duct.

Claims

1. A periscope for the transmission of optical signals from the reaction chamber of a high-temperature reactor, comprising an optical system arranged coaxially in a tubular housing penetrating a wall of the chamber so that a light-entry end of the optical system is nearer to the chamber, there being an annular clearance between the housing and the optical system which opens into the chamber and through which scavenging gas under pressure may be passed into the chamber, wherein there is positioned coaxially within the housing in front of the optical system a hollow, frusto-conical element the narrower-diameter end of which is nearer to the chamber and provides the light-admission aperture of the optical system, the portion of the housing which surrounds said element being internally frusto-conical with a taper angle equal to or greater than that of said element so that the annular gap between said portion of the housing and said element is of constant width or of a width which decreases toward the chamber, said element being provided in a region nearer to the optical system with openings to admit scavenging gas from said annular gap into said element, the aggregate area of said openings being a multiple of the area of said aperture.

2. A periscope as claimed in claim 1, wherein said openings penetrate the element obliquely with respect to radial planes so that scavenging gas entering said element is caused to swirl before emerging from said aperture.

3. A periscope as claimed in claim 1, wherein said openings are similar and symmetrically disposed around said element, each having the form of an incomplete ellipse such that the opening has a longer arm and a shorter arm originating from a vertex at the nearest point of said opening to the widerdiameter end of said element.

4. A periscope as claimed in any one of the preceding claims, wherein a narrowerdiameter end region of said element is exter nally cylindrical, the cylindrical surface merging continuously and without a step with the frusto-conical surface.

5. A periscope as claimed in any one of the preceding claims, wherein the said annular gap opens toward the chamber via a circular array of equiangularly spaced apertures.

6. A periscope as claimed in claim 5, wherein said apertures are provided between flanges on the narrower-diameter end of said element which serve to locate the latter within the housing.

7. A periscope as claimed in any one of the preceding claims, wherein the ratio be tween the cross-sectional area of the free space of said aperture and of said annular gap where the latter opens toward the chamber is in the range 1:0.7 to 1:2.

8. A periscope as claimed in claim 7, wherein said ratio is 1:1.

9. A periscope as claimed in any one of the preceding claims, wherein the optical sys tem comprises a front lens nearest to the combustion chamber of diameter equal to the inner diameter of the larger-diameter end of said element and fitted therewithin, the ratio of the diameter of said aperture to that of said front lens being in the range 1:5 to 1:8.

1 0. A periscope as claimed in any one of the preceding claims, wherein the housing has an end portion extending from said element toward the chamber the bore of which widens over a curve to form a diffuser, the radius of said curve being so chosen that the housing does not obstruct light passing from the chamber through said aperture to the optical system.

11. A periscope as claimed in any one of the preceding claims, wherein said housing is water-cooled.

1 2. A periscope for the transmission of optical signals from the reaction chamber of a high-temperature reactor substantially as de scribed in the Description, with reference to and as shown in Figs. 1, 2, 3 and 5 or Fig. 4 of the accompanying diagrammatic drawings.