AU723335B2

AU723335B2 - Method of monitoring the operation of a device for feeding an abrasive medium by means of a fluid

Info

Publication number: AU723335B2
Application number: AU44506/97A
Authority: AU
Inventors: Hado Heckmann; Josef Stockinger
Original assignee: Voest Alpine Industrienlagenbau GmbH
Current assignee: Primetals Technologies Austria GmbH
Priority date: 1996-09-19
Filing date: 1997-09-02
Publication date: 2000-08-24
Anticipated expiration: 2017-09-02
Also published as: PL332239A1; SK35799A3; TR199900608T2; ATA909097A; TW350877B; WO1998012357A1; CA2266328A1; JP2001501729A; ZA977132B; DE19638346C1; AU4450697A; EP0951570A1; BR9711402A; KR20000036213A; CN1230999A; ID18315A

Description

i 1 METHOD OF MONITORING THE OPERATION OF A DEVICE FOR FEEDING AN ABRASIVE MEDIUM BY MEANS OF A FLUID The invention relates to a method of monitoring the operation of a device for feeding an abrasive medium, especially of a dust-recycling system, into a melting gasifier, the dust extracted from a melting gasifier or reduction shaft furnace being introduced by means of a fluid via a dust conveyor tube through at least one dust burner into the melting gasifier as an additional carbon carrier. The method can also, however, be used for the feeding of abrasive media by means of fluid injection into other melting or incineration plants, such as fluid bed o. .reactors.

DE 40 41 936 Cl discloses a way of feeding the 'gases, of deposited hot dusts, streaming out of melting gasifiers or reduction shaft furnaces, back into the process of a melting gasifier. In this process, an injector is used in order to pass the dust which is to be recycled via a dust conveyor tube and via at least one dust ^burner back into the melting gasifier.

eo.

During operation, under the known severe S- 25 conditions for melting gasifiers, hot gases or unburned oxygen can flow back into the dust recycling system. In such a case, there exists the very great danger that plant components can be damaged or destroyed as a result of an explosion.

It is therefore the purpose of the invention to detect such a state as soon as possible and reliably to prevent any threat being caused by gases flowing back into the dust recycling system.

According to the present invention there is provided a method of monitoring a supply stream that \\melb-files\homeS\suzanet\Keep\Speci\44506-97.1 SPECI.doc 9/06/00 2 supplies an abrasive medium to a melter gasifier via a burner, the method including: measuring gas pressure in the supply stream on the side of the burner opposite to the melter gasifier, and (ii) measuring gas pressure in the melter gasifier, whereby, in the event of measuring a rise in gas pressure in the supply stream without a proportional rise in gas pressure being measured in the melter gasifier, supply of gas including oxygen to the melter gasifier is controlled to prevent reverse flow of gases including oxygen in the supply stream from the melter gasifier.

15 According to the present invention there is also provided a method of monitoring a supply stream that supplies an abrasive medium to a melter gasifier via a burner, the method including measuring the gas pressure in two measuring streams which are branched off the supply stream downstream of the burner at different angles relative to the axial direction of the supply stream, wherein gas pressure differences between the two measuring streams provides an indication of a direction of gas flow in the supply stream, and upon detection of reverse flow of 25 gases in the supply stream, supply of gas including oxygen to the melter gasifier is controlled to prevent reverse flow of gases including oxygen in the supply stream from the melter gasifier.

According to the present invention there is also provided a method of monitoring a supply stream that supplies an abrasive medium to a melter gasifier via a burner, the method including measuring the presence of oxygen in the supply stream using a monitoring device, the monitoring device having a combustion zone, and a combustion monitoring means for optically or acoustically monitoring combustion in the combustion zone, wherein the \\melb.files\home$\suzannet\Keep\Speci\44 5 0 6 9 7 .1 SPECI.doc 9/06/00 2amonitoring device allows the passage of oxygen from the supply stream into the combustion zone and combustion of oxygen in the combustion zone is monitored by the combustion monitoring means to indicate the presence of oxygen in the supply stream such that when the combustion monitoring means indicates that the supply stream includes oxygen, the supply of gas including oxygen to the melter gasifier is controlled to prevent reverse flow of gases including oxygen in the supply stream from the melter gasifier.

Through detecting the flow direction in the conveyor tube of a dust recycling system, the returned dust being the abrasive medium and being used as an additional 15 carbon carrier in the melting gasifier, it is possible in a simple and reliable way to determine whether any undesired backflow of gases is occurring and a corresponding scenario can be initiated which reliably prevents a threat such as already mentioned (explosion) from occurring.

A favourable possibility for this consists in S! monitoring simultaneously the pressure in the melting gasifier and in the dust conveyor tube. If a rise in pressure in the dust conveyor tube is detected, in the case 25 where there is no corresponding rise in pressure \\melbfiles\home$\suzannet\Keep\Speci\44506-97.1 SPECI.doc 9/06/00 3 in the melting gasifier, it can be clearly inferred than an undesired operating situation has been reached which can pose a threat to the system. With such a measuring result, in this case it can be inferred that hot gas or oxygen has penetrated into the dust conveying system of the dust-recycling system and this must be reacted to appropriately in order to overcome a state of danger.

A particularly advantageous way of determining the flow direction in the dust conveyor tube consists in the fact that at least two measuring channels are led through the wall of the dust conveyor tube, the angles of inclination of these measuring channels being different in relation to the longitudinal axis of the dust conveyor tube in the measuring plane. A measuring channel can here be inclined orthogonally to the longitudinal axis of the dust conveyor tube and the second measuring channel can be inclined at an acute 0 angle to this axis.

As is also the case with other measuring methods which are based on the principle of fluid dynamics, it has an advantageous effect, in order to prevent blocking of the measuring channel apertures, if a fluid is led through said apertures into the conveying flow.

Nitrogen suggests itself in particular as such a measurement fluid since nitrogen, as a known inert gas, cannot lead to any threat in the dust-recycling system.

As a result of the differing inclination of the measuring channels in relation to the longitudinal axis of the dust conveyor tube, the pressures in both measuring channels with the exception of the operating point which is defined by the zero crossing or null balance always differ, the pressure difference being under otherwise identical conditions a measurement for the flow velocity in the conveyor tube. If expediently a null balance is carried out for the current-free state, a reversal of the flow direction can be directly inferred from a change of sign of the pressure difference, which reversal is a pre-requisite for the feared case of a backflow of hot flame gases or oxygen into a dust conveyor tube. The proposed arrangement of the measuring channels can, however, be adapted to different conditions by other variants, especially different selected angles of inclination, of the measuring channels whose pressure values are to be compared with one another.

A further possible way of monitoring the backflow of oxygen into the dust-recycling system consists in the fact that a flame guard is led through the wall of the dust conveyor tube. In this process, problems must be taken into account which can occur through possible blockages caused by dust. Negative effects which occur from harmful components

H

2 S) in the conveyor flow must likewise be taken into account. The flame guard has a fuel-gas supply and an ignition device which can for example be configured as a heat plug or a spark generator. If oxygen penetrates via the aperture of the dust burner into the dust conveyor tube and reaches the flame guard, the ignition of the combustible gas mixture occurs and this can be detected via optical or acoustic sensors or via a measurement of temperature.

The invention is to be described in more detail below with the aid of embodiments, given by way of example.

Here the figures show: Fig. 1 a block diagram of the application of a fluid dynamic measurement principle with two measuring channels; Fig. 2 variants for possible measuring channel arrangements and Fig. 3 the monitoring of a dust conveyor tube by means of a flame guard.

In the principle of a pressure difference measurement shown in Fig. 1, this measurement is carried out in two measuring channels 1 and 2. The measuring channels 1 and 2 are here configured as bores which are led through the wall of the dust conveyor tube 3. The measuring channel 1 is here inclined orthogonally to the longitudinal axis of the dust conveyor tube 3 and the measuring channel 2 is inclined at an acute angle to same. The arrow Vc drawn in Fig. 1 indicates the direction in which a danger situation can occur, i.e.

hot gases or oxygen flow back into the system. In principle, a reverse arrangement of the probes in 10 relation to the flow direction can also be used.

Nitrogen is fed into the measuring channels 1 and 2 via a supply line 4. The volume flow of the nitrogen which is led into the measuring channels 1 and 2 is kept constant by means of a control system. For this purpose, volume flow sensors 5 and 6 with control valves 7 and 8 are present. For the supply of the measurement fluid (nitrogen), a further valve 9 is present in conjunction with a pressure sensor 0 As well as the measurement of the pressure difference in the measuring channels 1 and 2, the absolute pressure in the dust conveyor tube 3 is monitored by means of a further pressure sensor 11.

The pressure difference in the measuring channels 1 and 2 is measured by means of pressure sensor 12. The pressure difference detected is a measurement for the flow velocity in the conveyor tube. If a null balance is carried out for the current-free state, it is possible with the aid of a change of sign of the pressure difference to detect that backflow into the dust conveyor tube 3 has taken place and a corresponding signal can be generated in order to shut off the supply of oxygen. The suitable shut-off mechanism for this purpose is not shown in this illustration.

Through the fact that the absolute setting values for the two measurement fluid flows through the measuring channels 1 and 2 can be favourably chosen with regard to the required measuring sensitivity and the measuring range for the measurement of the pressure difference, an optimum region suitable for monitoring can be set without problem. Via the setting of the ratio of the measurement fluid flows, a null balance of the pressure difference can be carried out moreover.

Through the parallel injection of the measurement fluid via the two measuring channels 1 and 2 and the measurement of the difference in pressure between these two measuring channels, the measured value is practically independent of the static pressure and is only affected directly by the static pressure (namely via the density) of the gas used. Through the slight inclination of the measuring channels transversely to the flow direction (bore in the wall of the dust conveyor tube the ideal Bernouilli measurement 8 principle Payn Ptotal Pstat cannot be realised and a corresponding measurement arrangement must be calibrated.

From Fig. 2 can be taken altogether six different possible arrangements of respectively two measuring channels. Here the arrangements shown in the upper row are so chosen that the corresponding apertures of the respective measuring channels are disposed at one point in the dust conveyor tube 3.

However, there also exists the possibility of arranging the measuring apertures of the measuring channels in different places, as can be seen from the lower row of Fig. 2. If the latter arrangement is chosen, what must be considered is that an increased time constant, which is determined by the spacing of the measurement apertures, must be taken into account when the difference in pressure between the measuring channels 1 and 2 is measured directly.

Moreover, when the version which has the measuring channels in one point is used, under certain circumstances a significantly higher measuring sensitivity can be achieved than with the version with separate measuring points.

From Fig. 3 can be taken a further example of an embodiment of a monitoring system configured according to the invention in which a flame guard 13 is used.

The flame guard 13 is here led at least partially through the wall of the dust conveyor tube 3, and in the case of backflow out of the melting gasifier via the dust burner, which likewise cannot be recognised in this representation, oxygen can reach the region of the flame guard 13. Through a supply line 14, combustible gas passes via an aperture through the flame guard 13 and can be led into the dust conveyor tube 3, the flow direction of the fuel-gas being discernible from the arrows.

In addition, an ignition device 15 is present which can be configured for example as a heat plug or a spark generator. If oxygen now reaches the region of the flame guard 13, the fuel-gas is ignited with the aid of the ignition device 15 and, in this example by means of an optical monitoring system 16, it is determined whether oxygen is located in the dust conveyor tube 3 or not. To protect the optical monitoring system 16, a protective glass 17 in front of a lens system 18, which focuses the light which may be detected during ignition onto a photocell 19, can be arranged in front of the latter.

As well as the optical monitoring of the flame guard 13, there is also the possibility of using a corresponding acoustic sensor or a temperature sensor.

Claims

1. A method of monitoring a supply stream that supplies an abrasive medium to a melter gasifier via a burner, the method including: measuring gas pressure in the supply stream on the side of the burner opposite to the melter gasifier, and (ii) measuring gas pressure in the melter gasifier, whereby, in the event of measuring a rise in gas pressure in the supply stream without a proportional rise in gas pressure being measured in the melter gasifier, supply of gas including oxygen to the melter gasifier is controlled 15 to prevent reverse flow of gases including oxygen in the :...supply stream from the melter gasifier. is

2. The method according to claim 1, whereby in the event of measuring a rise in gas pressure in the supply stream without a proportional rise in gas pressure being measured in the melter gasifier, supply of gas including oxygen is shut off to the melter gasifier.

3. A method of monitoring a supply stream that supplies an abrasive medium to a melter gasifier via a burner, the method including measuring the gas pressure in two measuring streams which are branched off the supply stream downstream of the burner at different angles relative to the axial direction of the supply stream, wherein gas pressure differences between the two measuring streams provides an indication of a direction of gas flow in the supply stream, and upon detection of reverse flow of gases in the supply stream, supply of gas including oxygen to the melter gasifier is controlled to prevent reverse flow of gases including oxygen in the supply stream from the melter gasifier. \\melbfies\home\suzannet\Kee\peci\44506-97.1 SPECI.doc 9/06/00 12

4. The method according to claim 3, wherein upon detection of reverse flow of gases in the supply stream, supply of gas including oxygen to the melter gasifier is shut off.

The method according to claim 3 or 4, wherein a measurement fluid, in a small amount in relation to the supply stream, is injected into the latter through the measuring streams.

6. The method according to claim 5, wherein the volume flow of the measurement fluid is kept constant in both measuring streams. 15

7. The method according to claim 5 or 6, wherein an inert gas is used as the measurement fluid. D

8. The method according to claim 7, wherein nitrogen is used.

9. A method of monitoring a supply stream that supplies an abrasive medium to a melter gasifier via a burner, the method including measuring the presence of oxygen in the supply stream using a monitoring device, the monitoring device having a combustion zone, and a combustion monitoring means for optically or acoustically monitoring combustion in the combustion zone, wherein the monitoring device allows the passage of oxygen from the supply stream into the combustion zone and combustion of oxygen in the combustion zone is monitored by the combustion monitoring means to indicate the presence of oxygen in the supply stream such that when the combustion monitoring means indicates that the supply stream includes oxygen, the supply of gas including oxygen to the melter gasifier is controlled to prevent reverse flow of gases including oxygen in the supply stream from the melter gasifier.

H:\suzannet\Keep\Speci\44 5 06- 9 7 .1 SPECI.doc 9/06/00 13 The method according to claim 9, whereby in the event of the combustion means indicating that the supply stream includes oxygen, the supply of oxygen to the melter gasifier is shut off.

11. The method according to any one of the preceding claims, wherein the supply stream is in the form of a conveyor tube.

12. A method of monitoring a supply stream that supplies an abrasive medium to a melter gasifier substantially as hereinbefore described with reference to the accompanying figures. q Dated this 9th day of June 2000 S- VOEST-ALPINE INDUSTRIEANLAGENBAU GMBH By their Patent Attorneys GRIFFITH HACK Fellows Institute of Patent and Trade Mark Attorneys of Australia a \\melb_files\homeS\suzannet\Keep\Speci\44506-9 7 .1 SPECI.doc 9/06/00