Claims:WE CLAIM:

1. A level measurement system for measurement of surface level of material stored inside storage bunker or silo comprising

a level transmitter with a cooperative antenna for emitting high-frequency radar pulses onto the surface of the material in the storage bunker or silo;and

a receiver involving said antenna for receiving the radar pulses that are reflected from the surface of the material in the storage bunker or silo due to change in dielectric constant values between air and the material in the bunker or silo and measuring distance between the antenna and the surface of the material from said reflected radar pulses.

2. The level measurement system as claimed in claim 1, wherein the level transmitter and the receiver constitutes a single unit and adapted to be mount inside a mounting hole on storage bunker top below feeding conveyor of the storage bunker or silo.

3. The level measurement system as claimed in claim 1 or 2, wherein the mounting hole is a circular opening of approximately 430 mm diameter and is available over each silo under the feeding conveyor, whereby allowable vertical distance between the mounting hole and the feeding conveyor above is approximately 400 mm.

4. The level measurement system as claimed in anyone of claims 1 to 3, wherein the level transmitter preferably includes 80 GHz W-Band radar which involves frequency modulated continuous wave method for enabling the antenna to emits electromagnetic wave with continuously varying frequency as the radar pulse with a narrower beam angle which can be focussed on the material surface to eliminates false readings and additional noise that bounce off as reflections from bunker or silo walls.
5. The level measurement system as claimed in anyone of claims 1 to 4, wherein the level transmitter is housed in an enclosure to facilitates sensor angle adjustment and provides protection to the transmitters against ingress of dust and mechanical damage.

6. The level measurement system as claimed in anyone of claims 1 to 5, wherein the receiver is configured analyze the reflected pulses involving measuring time elapsed between pulse emitting and receiving for a direct measurement for distance between the antenna and the surface of the material.

7. The level measurement system as claimed in anyone of claims 1 to 6, wherein the transmitters generates 4-20 mA HART output corresponding to level of coal inside the coal storage bunkers or silos for determining the level of coal stored in the storage bunkers or silos.

8. The level measurement system as claimed in anyone of claims 1 to 7, comprising multiple transmitters implemented on multiple coal silos and multiple corresponding receivers for detecting coal levels in each said coal silos, wherein the each of receivers is connected to a dedicated digital indicator to provide real time display of corresponding silo level;

said digital indicators are configured to re-transmit the level measurement signal and High / Low level indication to a remote PLC interface unit and said Remote PLC unit is connected with the main PLC for real-time control and monitoring.

Dated this the 29th day of March, 2022
Anjan Sen
Of Anjan Sen & Associates
(Applicant’s Agent)
IN/PA-199
, Description:FIELD OF THE INVENTION:

The present invention relates to measurement of coal level inside storage bunkers or silos. More specifically, the present invention is directed to develop an integrated automated system for measurement of coal level inside coal storage bunkers or silos.

BACKGROUND OF THE INVENTION:
The coal bunkers/silos are integral part of a steel processing plant. These coal bunkers are usually a tall structure and coal is fed into them from top through an inclined feeding conveyor and tripper car assembly. The Tripper car collects coal from feeder conveyor and dump it into the storage coal bunkers/silos. There are two chutes through which coal can be transferred from conveyor to each bunker. Provisioning is done on top of the coal bunkers/silos for mounting level measurement sensor.

Accurate information about the amount of coal stocked within the bunkers is crucial for smooth operation of an integrated steel plant. Volumetric measurement of bulk material like coal is prone to error owing to various issues. This is because solids stored in a vessel do not have a flat, horizontal surface unlike liquids. Determination of exact level of such uneven surface renders a complex issue especially when combined with the effect of ever changing surface profile owing silo filling and discharging. Stickers and dust can also pose as a source of errors as they disrupt normal operation of level measurement sensors.

Level measurement with electromechanical system suffers from localized readings that might not reflect true level of the material. Ultrasonic sensor-based system that work of Time-of-flight technique is susceptible to dust, pressure fluctuations, changing angle of repose, large particle sizes, internal vessel obstructions, and coating or formation of mounds on the internal vessel surfaces. Guide wave Radar system works satisfactorily in dusty applications like coal silos. It is unaffected by the density of bulk solid, temperature, dust, and humidity and almost unaffected by baffles. However, the performance of the system is more effective with materials of dielectric constant greater than 1.3. Wave guides can be damaged in long run due to impact as well. Laser-based level transmitter provide fast and precise response, however, the performance degrades in high dust environment.

The known art for measurement of coal level inside storage bunkers or silos are thus suffers from following major drawbacks:
i) Overflow of material from silos owing to unreliable working of the level measurement system
ii) Suboptimal productivity owing to under-filled silos.
iii) Inaccurate readings of coal level within silo due to inherent issues in technology used.
iv) Lacks interlocks or similar safety-mechanisms

It is thus there has been a need for developing an improved system for measurement of coal level inside storage bunkers or silos which can address the above drawbacks.

OBJECTIVE OF THE INVENTION:
It is thus the basic object of the present invention is to develop an improved system for measurement of coal level inside storage bunkers or silos

Another object of the present invention is to develop an improved non-contact type level measurement system for continuous measurement of coal level inside storage bunkers or silos

A still further object of the present invention develop an improved non-contact type level measurement system for continuous measurement of coal level inside storage bunkers or silos which would be protected from ingress of coal dust and mechanical damage.

Yet another object of the present invention develop an improved non-contact type level measurement system for continuous measurement of coal level inside storage bunkers or silos and determine exact level of uneven coal top surface in the bunkers/silos combined with the effect of ever changing surface profile owing silo filling and discharging.
SUMMARY OF THE INVENTION:

Thus according to the basic aspect of the present invention there is provided a level measurement system for measurement of surface level of material stored inside storage bunker or silo comprising

a level transmitter with a cooperative antenna for emitting high-frequency radar pulses onto the surface of the material in the storage bunker or silo; and

a receiver involving said antenna for receiving the radar pulses that are reflected from the surface of the material in the storage bunker or silo due to change in dielectric constant values between air and the material in the bunker or silo and measuring distance between the antenna and the surface of the material from said reflected radar pulses.

In a preferred embodiment of the present level measurement system, the level transmitter and the receiver constitutes a single unit and adapted to be mount inside a mounting hole on storage bunker top below feeding conveyor of the storage bunker or silo.

In a preferred embodiment of the present level measurement system, the mounting hole is a circular opening of approximately 430 mm diameter and is available over each silo under the feeding conveyor, whereby allowable vertical distance between the mounting hole and the feeding conveyor above is approximately 400 mm.

In a preferred embodiment of the present level measurement system, the level transmitter preferably includes 80 GHz W-Band radar which involves frequency modulated continuous wave method for enabling the antenna to emits electromagnetic wave with continuously varying frequency as the radar pulse with a narrower beam angle which can be focussed on the material surface to eliminates false readings and additional noise that bounce off as reflections from bunker or silo walls.

In a preferred embodiment of the present level measurement system, the level transmitter is housed in an enclosure to facilitates sensor angle adjustment and provides protection to the transmitters against ingress of dust and mechanical damage.

In a preferred embodiment of the present level measurement system, the receiver is configured analyze the reflected pulses involving measuring time elapsed between pulse emitting and receiving for a direct measurement for distance between the antenna and the surface of the material.

In a preferred embodiment of the present level measurement system, the transmitters generates 4-20 mA HART output corresponding to level of coal inside the coal storage bunkers or silos for determining the level of coal stored in the storage bunkers or silos.

In a preferred embodiment, the present level measurement system comprising multiple transmitters implemented on multiple coal silos and multiple corresponding receivers for detecting coal levels in each said coal silos, wherein the each of receivers is connected to a dedicated digital indicator to provide real time display of corresponding silo level;

said digital indicators are configured to re-transmit the level measurement signal and High / Low level indication to a remote PLC interface unit and said Remote PLC unit is connected with the main PLC for real-time control and monitoring.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Fig 1 shows top view of the silo top indicating coal feeding hole and sensor mounting location.

Fig 2 shows the present non-contact type level measurement system configuration.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS:

As stated hereinbefore, the present invention provides a non-contact type level measurement system for continuous measurement of level of coal inside storage bunkers. The system employs ‘Through–Air-Radar’ (TAR) mechanism for measurement of level of coal inside storage bunkers. The system includes a transmitter and a receiver which are combined to act as a single unit. The transmitter includes an antenna which emits high-frequency radar pulses. The transmitted radar pulses are reflected from the surface of material in the storage bunkers as there is a change in dielectric constant values between the air and the material. Upon receiving the reflected pulse, the time elapsed between pulse launching and receiving is measured by the receiver. It constitutes a direct measurement for the distance between the antenna and the surface of the material.

A top view of the silo top indicating coal feeding hole and level measurement sensor system mounting location is shown in the accompanying Fig 1.

As shown in the Fig 1, the mounting location of the transmitter is with respect to the floor of the storage bunker top. The mounting hole is a circular opening of approximately 430 mm diameter and is available over each silo under the feeding conveyor. The transmitter is mounted inside the aforesaid opening of the silo. The allowable vertical distance between the instrument mounting hole and the feeding conveyor above is approximately 400 mm.

Reference is now invited from the accompanying fig 2 which shows the present non-contact type level measurement system configuration. As shown in the fig, multiple transmitters may be implemented on multiple silos. These transmitters are preferably based on 80 GHz W-Band radar which uses frequency modulated continuous wave method (FMCW) for level sensing. The antenna emits electromagnetic wave at a continuously varying frequency as the radar pulses. A special enclosure has been designed to house the level transmitters. The enclosure facilitates sensor angle adjustment and provides protection to the transmitters against ingress of coal dust and mechanical damage.

The level transmitters generate 4-20 mA HART output corresponding to the level of coal inside the silos and the corresponding receivers is configured to detect the reflected pulses for direct measurement of the coal level. The receiver electronics calculates the silo level based on frequency phase shift and travel time of electronics wave Upon receiving the reflected pulse, the time elapsed between pulse launching and receiving is measured by the instrument. It constitutes the direct measurement for the distance between the antenna and the surface of the material. Each of the receivers is connected to dedicated digital indicators to provide real time display of silo level. The display is provided at the operator’s room at silo top. Each digital indicator also re-transmits the level measurement signal and High / Low level indication to a remote PLC interface unit. Remote PLC unit is connected with the main PLC at a control room at a distance of around 1 Km through network interface modules and FO cable.

The radar produces a high power energy wave that is able to pass through harsh environment including dust, to the solids surface. The only possible issue would be if vapours or moisture combine to provide an atmosphere that has a dielectric constant higher than that of the solids material itself, which is generally not found in coal level measurement. The 80GHz W-Band radar provides a narrower beam angle which can be focussed on the coal surface as compared to Ultrasound sensors or radars that operate in lower frequency bands. This eliminates false readings and additional noise that bounce off as reflections from silo walls.

The present level measurement system thus enables operators at control room with additional real time display, historical trend, graphics and MIS reports of silo level for the silos. HMI is also provided at a terminal through same PLC network in a shift room located around 1 Km. The HMI displays and reports enables operators in taking timely decision of silo filling and discharging.

The weigh feeders are operated by an existing centralized PLC based system from a control room. The level transmitters signals and auxiliary signals like proximity switches are connected with this centralized PLC through a remote PLC interface unit installed at silo top. The remote PLC interface unit at silo top is connected with centralized PLC unit through Fiber Optic cable.