COMPACT RADAR-BASED PROFILEMETER FOR BLAST FURNACES

TECHNO COMMERCIAL PROPOSAL

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1. Designation

The radar-based profilemeter is designed for automatic contact-less measuring of the stock line level and profile in blast furnaces.

The stock line profile controlling system (PCS), which is suggested for supply, makes it possible for the profilemeter to operate both in automatic mode and also as integrated into the automatic blast furnace process control systems.

The profilemeter makes it possible to optimize the distribution of stock throughout the span of the furnace top and thanks to that to increase the utilization rate of gas reducing ability, reduce the specific rate of coke and enhance the furnace productivity.

The compact radar-based profilemeter can be effectively used in blast furnaces that are equipped with charging apparatuses of any design: two-bell, chute-type or rotary.

The profilemeter is capable of measuring stock line level and profile both in the furnace top under regular operating conditions, and at a lower horizons inside the furnace at the time of blow-in and blow-out.

The profilemeter can be used not only in blast furnaces but in any other shaft furnaces as well.

2. General characteristics and principal of operation

The set suggested for supply includes mechanical equipment and hardware of the stock line profile control.

The mechanical equipment part consists of the following key units and parts (Figure 1):

Radar sensor body (1). The body is made in the form of a water-cooled pipe with a flange to accommodate the radar sensor on it. Thanks to the water-cooling of the body, the temperature of medium at the spot where radar sensor is installed, will not exceed the permissible limit.

Nitrogen supply unit (2). This unit is designed as a branch pipe with two flanges, one is connected with the flange in the radar sensor casing (1), the other with that in the slewing reflector casing (3). There is an annular manifold with bores to feed nitrogen into the inner space of the profilemeter. Nitrogen is fed under pressure, which exceeds the top gas pressure in the underdome zone of the blast furnace. For that there is a provision of additional cooling of inner parts of the profilemeter and their protection from dust.

Slewing reflector body (3). The body has flanges to connect and install the adjacent units and parts of the equipment. Inside the body there is a slewing pipe (4) with a reflecting member (5). The gap between the body and slewing pipe is sealed (6). The body has a shut-off valve (7), which can shut bore (8) in the slewing pipe. The bottom of the body with flange is water-cooled, which prevents the heating of the body when heat loads in the underdome zone of the furnace go up.

Slewing reflector actuator (9). The actuator consists of a gearbox (10) and stepping electric motor (11). The gearbox (10) is connected with the sewing pipe through a coupler.

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Funnel (12) The funnel has a flange to fasten the body (3) and a bracket to accommodate the actuator (9) of the slewing reflector. The funnel is welded to the furnace dome shell (13), its flow section is square in shape and flares towards the furnace.

Fig. 2 shows a suggested installation of the compact radar-based profilemeter in the blast furnace, which has a bell-less rotary charging unit.

The spacious layout of key parts and units of the mechanical equipment is explicitly shown in Fig.3.

The structural diagram of PCS is given in Fig.4. PCS main hardware makeup is as follows:

radar level sensor (1); stepping motor (2) to operate the positioning of the slewing radio-waves reflector

(supplied as complete with mechanical equipment see above);

PLC cabinet (3); personal computer, industrial design (4).

Radar level sensor - Of Russian design, ( type). The peculiar feature of the sensor is the provision of 100% redundancy of the radio-signal converter electronic block, using an autonomous power source, as well as a high frequency of EHF radiation by the receiving/transmitting module 37.5 GHz.

PLC cabinet - It is based on SIMATIC S7-200 and consists of: - central processor module, which has a converter of interface RS-485, 6 discrete inputs

and 4 relay outputs;

- communication processor Industrial Ethernet; - positioning module for actuators with stepping motors (EM 253); - power pack FM STEPDRIVE- the device for direct control of stepping motors; - twp power sources (operating and stand-by) for the electronic blocks of the radar sensor.

Industrial PC - processor - at least Pentium IV; - HDD - minimum 10 Gb; - RAM - minimum 512 Mb; - Software - Windows XP/2000

Stock line level and profile are measured with the help of radar profilemeters by sounding the burden surface with the help of an impulse EHF radio-signal and simultaneously receiving, treating and analyzing the reflected signal. It is the linear-frequency modulation of EHF band radio-waves which is used as a principle to measure distances.

The distribution of EHF band radio-waves is not affected by dust content and temperature of medium This essential circumstance makes the application of the radar-based profilemeters very promising in measuring distances to the stock line in the underdome zone of blast furnaces, where, as is well known, the physical medium is characterized by a high temperature and dust content in the top gas.

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The salient feature of the compact radar-based profilemeter is the fact that EHF radiation from the radar receiving/transmitting antenna goes to the burden surface through a slewing reflecting member, the surface of which is positioned at a fixed angle of 45 against the antenna central line and at the same time it can turn round this line at any preset angle.

The angular position of the slewing reflector with resolution of at least 0.5 is adjusted by a stepping motor according to the PCS positioning program. It makes it possible to scan burden surface exactly along the top radius, along the vertical plane, which goes through the blast furnace central line.

The slewing reflecting member makes it possible to take the radar device completely out of the furnace underdome zone, thus protecting it against the influence of high temperatures, aggressive gas and dust, thus enhancing considerably the dependability of the radar electronic part. Such a design made it possible to improve the resistance of the radar electronic components to coercive influences from environment, as well as made it as compact as possible and easily accessible for maintenance and repair. All these have increased the dependability of the radar-based profilemeter on the whole and basically upgraded its performance.

3. Specification 1. Designation - Measuring of stock line level and

profile in blast furnace

2, Measuring technique - Radar- based

3, EHF radiation frequency - 37.5 GHz

4. Measurement environment - Top gas: - temperature reg. - 200300 C max. - 500 C - moisture content - up to 100 g/Nm3- dust content up to 50 g/Nm3

5. Measuring duty - continuous

6. Measuring range - 1 - 30 m

7. Measuring error - within 1 - 10 m - within 10 - 30 m

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30 mm 50 mm

8. Angular position range of the slewing reflector - 0 - 70

9. Slewing reflector positioning accuracy, at least - 0.5

10. Interfaces: - radar sensor to controller - additional analogue output - communication of controller with PC

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RS 485 4 20 mA Ethernet

11. PCS power supply - 240 V 10%, 50 Hz

12. Radio-wave radiation strength, maximum - 50 mW

13. Radar sensor consumed power, maximum - 30 W

14. Radar sensor voltage - + 24 V

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15. Cooling water parameters - flow rate, max. - inlet temperature, max.

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10 m3/hour 35 C

16. Nitrogen rate (max.) - 200 Nm3/hour

17. Mechanicals overall dimensions at the furnace top - see Fig.1

18 Mechanical equipment weight 330 kg

4. Outline of performance It is a short-distance radar which is used in PCS. Therefore it is possible to measure short

distances (up to 30 m) with a high degree of accuracy ( 3 cm), to decrease its responsively to clutters, caused by the reflection of the beam from steel structures and process equipment.

It is 37.5 GHz frequency radiation which is assumed as a probing signal in PCS, which corresponds to a 8 mm long radio-wave. This length of the radio-wave is accounted for by the maximum values of absorption of electromagnetic radiation frequencies by water evaporation and ambient gas, which makes it preferable for use in the top gas medium. Besides, it would be possible to provide a sufficiently narrow beam, capable of a large span resolution with minimized at that overall dimensions of hardware. The assumed length of the radio-wave (8 mm) is substantially bigger than dust particles in the top gas, which ensures lower scattering and absorption of EHF radiation.

The stock line profile in the furnace top is to be measured after the discharge of regular batch of stock into the furnace.

The main member of PCS is a level gauge based on a radar sensor -2, made in Russia. It is a frequency method which is used for this sensor to determine the distance to the surface of the object.

The travel time of the radio-signal is determined by measuring the difference between the frequencies of oscillations emitted by the radar antenna and those of the reflected signal. The radar EHF generator operating frequency is 37.5 GHz. The frequency can be varied within the range of 500 MHz with the help of varactor. The voltage of the latter is adjusted by a processor of the radar electronic block.

EHF oscillations come to the radar antenna and further through the slewing reflector are radiated to the burden surface. The reflected signal is received by the same antenna and then sent to the mixer, where the frequency differential is composed thanks to the lag of the reflected signal. It is this differential that determines the distance to the burden surface (or its level) at the point of reflection.

The transformed signal differential may content strays. Having been filtrated and digitized the signal goes to the input of the processor of the radar electronic block, wherein it undergoes fast transformation (FFT). In the course of this processing the system would put interferences though the gate circuit, filtrate the current band, determine the threshold for band components that have maximum amplitude at the background of the averaged noise level and make a decision how to find out the level. The shortest time for this procedure will be 100 ms. To provide for a better validity, in some cases it would be desirable to scan the same spot on the surface several times.

Further, the signal thus received will go through interface RS 485 to the PLC central processor module. The generated data are transmitted through Ethernet bus and communication module CP 243-1 to the system computer, wherein a data base will be created for plotting the stock line profile. As the current measuring cycle is over, PLC would compose a controlling signal to the

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stepping motor to turn at the desired angle. This signal goes through the power section FM STEPDRIVE to the stepping motor, which puts the slewing reflector into a new position as per the preset program for scanning the burden surface. Further, the next spot on the burden surface is scanned and so on and so forth.

As the scanning is over and the level of preset spots on the burden surface has been determined, BPCS computer displays the stock line profile and PLC composes commands to pout the slewing reflector into the initial position.

The burden surface scanning principle and display of its profile on the monitor is shown in Fig.5.

In case of the scheduled maintenance work needed for the profilemeter, or replacement of the radar sensor or reflecting member, the slewing pipe is turned with the help of the drive so that the bore in it would face the shut-off valve poppet. After that the valve is to be closed and as a result of it the radar sensor and reflecting member would be isolated from the furnace working space and could be easily and safely replaced.

5. The TOTEM scope of supply and service TOTEM supplies the compact radar-based profilemeter on "turn-key" terms, which

includes:

profilemeter mechanical equipment; hard and software for BPSC; required technical documentation; contractual supervision for mechanical equipment and BPSC hardware mount work,

start-up and adjustment work and commissioning;

demonstration of performance guarantees; training of the Client's personnel.

All construction and erection work related to the installation of the profilemeter, shall be the scope of the Client.

6. Delivery dates The profilemeter can be supplied within 6 months from the date of the advance paid by the

Client.

7. Commercial terms The overall cost of TOTEM supply and services, as specified under Clause 5, is 250,000

(Two hundred fifty thousand) Euro.

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