FIELD OF INVENTION
The present invention relates generally to detection devices. In particular, the
present invention relates to a piezoelectric sensor(s) based fly ash level detection
device.
5 BACKGROUND OF THE INVENTION
Ash level measurement is an important requirement in thermal power plants.
Ultrasonic sensors and radar level transmitters are known in the art for ash level
measurement inside hoppers. However, they are prone to incorrect/ false
measurements when ash gets deposited on the sensor surfaces. As fly ash has
10 poor reflectivity, it also creates problems for the radar level transmitter. The
aforementioned technologies are also costly. Capacitance based technology is
also used for ash level measurement system. However, in ash hoppers, different
types of ashes gather, each possessing different dielectric constant and as a
result, capacitance of the capacitor changes even for the same level of ash.
15
In the light of above, there is a need to develop more robust sensing devices
which can accurately detect the levels of fly ash in a storage unit/silo, is easy to
install and operate, and is economical.
SUMMARY OF THE PRESENT INVENTION
20 In an aspect of the present invention, there is provided a fly ash level detection
module comprising a sensing unit, wherein said sensing unit comprises a first
piezoelectric sensor; a second piezoelectric sensor, wherein said first and second
piezoelectric sensors are paired; and a metal scaffold, wherein said first and
second piezoelectric sensors are detachably attached to the scaffold at a pre25 determined distance from each other, and the scaffold is able to freely vibrate.
In another aspect of the present invention, there is provided a fly ash level
detection device, comprising (a) a fly ash level detection module comprising a
sensing unit, wherein said sensing unit comprises a first piezoelectric sensor; a
second piezoelectric sensor, wherein said first and second piezoelectric sensors
3
are paired; and a metal scaffold, wherein said first and second piezoelectric
sensors are detachably attached to the scaffold at a pre-determined distance
from each other, and the scaffold is able to freely vibrate; (b) a signal
conditioning circuit capable of converting an output AC voltage from the second
5 piezoelectric sensor of the sensing unit to a generated DC voltage; (c) at least an
indicating system comprising at least an audio/visual output device; (d) at least a
signal transmission system capable of transferring data between the fly ash level
detection device and a remote device; and (e) at least a hardware module
electrically connected to at least the signal conditioning circuit and the signal
10 transmission system.
In yet another aspect of the present invention, there is provided an enclosed
compartment for storing fly ash, wherein said compartment comprises at least a
fly ash level detection device, said device comprising: (a) a fly ash level detection
module comprising a sensing unit, wherein said sensing unit comprises a first
15 piezoelectric sensor; a second piezoelectric sensor, wherein said first and second
piezoelectric sensors are paired; and a metal scaffold, wherein said first and
second piezoelectric sensors are detachably attached to the scaffold at a predetermined distance from each other, and the scaffold is able to freely vibrate;
(b) a signal conditioning circuit capable of converting an output AC voltage from
20 the second piezoelectric sensor of the sensing unit to a generated DC voltage; (c)
at least an indicating system comprising at least an audio/visual output device;
(d) at least a signal transmission system capable of transferring data between the
fly ash level detection device and a remote device; and (e) at least a hardware
module electrically connected to at least the signal conditioning circuit and the
25 signal transmission system.
In still another aspect of the present invention, there is provided a method for
detecting fly ash levels in an enclosed compartment, the method comprising the
steps of (i) supplying an input AC voltage to at least a fly ash level detection
module of a device, said device comprising (a) a fly ash level detection module
4
comprising a sensing unit, wherein said sensing unit comprises a first
piezoelectric sensor; a second piezoelectric sensor, wherein said first and second
piezoelectric sensors are paired; and a metal scaffold, wherein said first and
second piezoelectric sensors are detachably attached to the scaffold at a pre5 determined distance from each other, and the scaffold is able to freely vibrate;
(b) a signal conditioning circuit capable of converting an output AC voltage from
the second piezoelectric sensor of the sensing unit to a generated DC voltage; (c)
at least an indicating system comprising at least an audio/visual output device;
(d) at least a signal transmission system capable of transferring data between the
10 fly ash level detection device and a remote device; and (e) at least a hardware
module electrically connected to at least the signal conditioning circuit and the
signal transmission system; (ii) detecting an output AC voltage generated by a
second piezoelectric sensor and converting the detected output AC voltage to a
generated DC voltage by the signal conditioning circuit of the device; (iii)
15 generating at least a signal by the hardware module by comparing the generated
DC voltage with at least a reference value, wherein at least a reference value is
correlated with at least a fly ash level; and (iv) displaying the generated signal by
the indicating system, and/or transmitting the generated signal by the signal
transmission system.
20 This summary is not intended to identify essential features of the claimed
invention nor is it intended for use in determining or limiting the scope of the
claimed subject matter.
DETAILED DESCRIPTION OF THE INVENTION
Those skilled in the art will be aware that the present disclosure is subject to
25 variations and modifications other than those specifically described. It is to be
understood that the present disclosure includes all such variations and
modifications. The disclosure also includes all such steps, features of the process
and the product referred to or indicated in this specification, individually or
collectively, and any and all combinations of any or more of such steps or
5
features.
For convenience, before further description of the present invention, certain
terms employed in the specification, examples are collected here. These
definitions should be read in light of the remainder of the disclosure and
5 understood as by a person of skill in the art. Unless defined otherwise, all
technical and scientific terms used herein have the same meaning as commonly
understood by a person of ordinary skill in the art. The terms used throughout
this specification are defined as follows, unless otherwise limited in specific
instances.
10 As used in the specification and the claims, the singular forms "a", "an", and
"the" include plural referents unless the context clearly dictates otherwise
The following terms shall be used throughout the specification to describe the
present invention.
The present invention provides a fly ash level detection module comprising a
15 sensing unit, wherein said sensing unit comprises a first piezoelectric sensor; a
second piezoelectric sensor, wherein said first and second piezoelectric sensors
are paired; and a metal scaffold, wherein said first and second piezoelectric
sensors are detachably attached to the scaffold at a pre-determined distance
from each other, and the scaffold is able to freely vibrate.
20 In a preferred embodiment, an air-gap is provided between the metal scaffold
and the attached first and independently the second piezoelectric sensor.
In a preferred embodiment, the piezoelectric sensor is ceramic based. In an
embodiment, the ceramic is PZT ceramic. In another embodiment, the ceramic is
lead zirconate titanate. In an embodiment, the piezoelectric sensor is polymer
25 based. In an embodiment, the polymer is polyvinylidene fluoride. In another
embodiment, the polymer is PVDF. In another embodiment, the piezoelectric
sensor is composites based. In yet another embodiment, the piezoelectric sensor
is crystal based. In an embodiment, the crystal is quartz. In still another
embodiment, the piezoelectric sensor is glass ceramics based. In an
6
embodiment, the glass ceramic is Li2Si2O5. In another embodiment, the glass
ceramic is Ba2TiSiO6. In an embodiment, the sensor can be PZT fibers mixed with
resin to form PZT composites.
In a preferred embodiment, the first and the second piezoelectric sensor are
5 made of the same material. In another preferred embodiment, the first and the
second piezoelectric sensor have the same dimensions. In yet another preferred
embodiment, the first and the second piezoelectric sensor have identical
characteristics, such as, but not limited to length, width, thickness, density,
Young’s modulus, and piezoelectric constant.
10 In an embodiment, the dimensions of the piezoelectric sensor is in the range of
70x22x0.1mm – 77x26x0.5mm. The piezoelectric sensors are adhesively attached
to the metal scaffold. In an embodiment, the piezoelectric sensors can withstand
a temperature up to 200°C. In an embodiment, the piezoelectric sensors can be
covered by a compressed non-asbestos fiber sheet to extend the temperature up
15 to 250°C.
The first piezoelectric sensor obeys reverse piezoelectric effect and the second
piezoelectric sensor obeys piezoelectric effect. The first and the second
piezoelectric sensor are operationally coupled to each other, in that they
function in conjunction as a single sensing/operating unit.
20 The present invention also provides a fly ash detection device, the device
comprising: (a) at least a fly ash level detection module; (b) a signal conditioning
circuit capable of converting an output AC voltage from the second piezoelectric
sensor of the sensing unit to a generated DC voltage; (c) at least an indicating
system comprising at least an audio/visual output device; (d) at least a signal
25 transmission system capable of transferring data between the fly ash level
detection device and a remote device; and at least a hardware module
electrically connected to at least the signal conditioning circuit and the signal
transmission system.
The fly ash level detection module of the device is as substantially described in
7
the present specification. In an embodiment, the device comprises 1 module. In
an embodiment, the device comprises 2 modules. In another embodiment, the
device comprises 3 modules. In a preferred embodiment, the device comprises 4
modules. In an embodiment, the device may comprise more than 4 modules.
5 Each module in the device operates independent of each other.
The signal conditioning circuit of the device essentially converts the AC voltage
generated by the second piezoelectric sensor to an output DC voltage in the
range of 1-5V. The signal conditioning circuit essentially comprises a rectifier and
a filter circuit to convert an output AC voltage into a generated DC voltage. The
10 indication system of the device comprising at least an audio/visual output device
can be one or more of speaker, LED screen, and the like. In an embodiment, the
signal transmission system comprises a wireless module. In another
embodiment, the signal transmission system comprises a wired module. In yet
another embodiment, the signal transmission system comprises both wireless
15 and wired module. In an embodiment, the wireless module is wi-fi. In another
embodiment, the wireless module is Bluetooth. In yet another embodiment, the
wireless module is IR. The signal transmission system of the device can transfer
information from the device to any connected to remote device. In an
embodiment, the connected or remote device can be a server. In another
20 embodiment, the connected to remote device can be a handheld reader. The
hardware module of the device is connected to the signal conditioning circuit
and the signal transmission module. The hardware module is capable of receiving
at least a signal in the form of DC voltage and compare the DV voltage to a predetermined/ reference value to generate at least an output signal indicative of
25 ash levels. In an embodiment, the output signal is received by the indicating
system. In another embodiment, the output signal is received by the signal
transmission system.
In an embodiment, where the device has 2 or more fly ash level detection
modules, each module has dedicated signal conditioning circuit, indicating
8
system, signal transmission system, and hardware module. In another
embodiment, where the device has 2 or more fly ash level detection modules,
the plurality of modules have a common hardware module. In another
embodiment, where the device has 2 or more fly ash level detection modules,
5 the plurality of modules have a common indication system.
The present invention also provides an enclosed compartment for storing fly ash,
the said compartment comprising at least a fly ash detection device as
substantially described in the present specification.
The present invention provides a method for detecting fly ash levels in an
10 enclosed compartment, the method comprising the steps of: (a) supplying an
input AC voltage to at least a fly ash level detection module of a device; (b)
detecting an output AC voltage generated by a second piezoelectric sensor and
converting the detected output AC voltage to a generated DC voltage by the
signal conditioning circuit of the device; (c) generating at least a signal by the
15 hardware module by comparing the generated DC voltage with at least a
reference value, wherein at least a reference value is correlated with at least a
fly ash level; and (d) displaying the generated signal by the indicating system,
and/or transmitting the generated signal by the signal transmission system.
An input AC voltage having particular frequency and amplitude is supplied to the
20 first piezoelectric sensor, wherein the input AC voltage acts as an excitation
voltage for the first piezoelectric sensor. The first piezoelectric sensor upon
receiving AC voltage starts to vibrate and acts as an exciter to the second
piezoelectric sensor. As a result, the second piezoelectric sensor also starts to
vibrate to generate an AC voltage.
25 In an embodiment, the frequency of vibration of the second piezoelectric sensor
is same as that of the first piezoelectric sensor. In another embodiment, the
frequency of vibration of the second piezoelectric sensor is less than that of the
first piezoelectric sensor. A reduction in frequency of the second piezoelectric
sensor than that of the first piezoelectric sensor is indicative of fly ash
9
accumulation. In an embodiment, at least a frequency of second piezoelectric
sensor is correlated to at least a level of fly ash. The dampening of frequency of
the second piezoelectric sensor is due to accumulation of fly ash.
The fly ash level detection device of the present invention can be used in
5 continuous mode for real-time detection of fly ash levels.
The fly ash level detection modules are welded at one to four sides/walls on a
lower surface of walls of an enclosed compartment for storing fly ash. To get
more accurate results, four fly ash level detection modules are welded on the
four walls of the galvanized sheets of the enclosed compartment along the
10 periphery and just above its bottom surface, in such a way that the opening of
the enclosed compartment is not get hampered, wherein, the width of the
welded portion is negligible in comparison to the opening diameter of the
hopper.
EXAMPLES
15 Example 1: Preparation of A Sensing unit
Two piezoelectric sensors of the same specifications i.e., length, width, thickness,
density, Young’s Modulus, piezoelectric constant etc. were paired together on an
aluminum scaffold, to make a sensing unit. The length of the aluminum scaffold
taken was larger than that of the piezoelectric sensors. Two piezoelectric sensors
20 or piezoceramic sensors or piezoceramic patches viz. a first piezoceramic sensor
and a second piezoceramic sensor of specification (76.2×25.4×0.5) mm, were
attached to the opposite surfaces of an aluminum scaffold of specification
(200×26×2) mm using Araldite adhesive.
The first piezoelectric sensor obeys the reverse piezoelectric effect and another
25 one follows the piezoelectric effect. The first piezoelectric sensor is supplied with
input AC voltage according to which the first sensor starts to vibrate and acted as
an exciter to the second one as both of them are attached together. Under ideal
conditions, the second piezoelectric sensor is expected to vibrate with the same
frequency as that of the first piezoelectric sensor and generate an output AC
10
voltage. When the enclosed compartment of the fly ash is empty, the second
piezoelectric sensor gives the highest output AC voltage. However, when the
enclosed compartment of the fly ash is filled with levels of fly ash, the
piezoelectric sensors feel pressure on them and accordingly the vibration of
5 second piezoelectric is damped and the output AC voltage of the second
piezoelectric sensor accordingly decreases, which is correlated with fly ash levels.
Example 2: Hopper and sensing section arrangement (Installation of the
sensing unit inside a Hopper)
After installation, the total ash level measurement system/device is calibrated
10 with the sensing units. Once the calibration is complete, the signal conditioning
circuit is calibrated to the output. For the transmission of the measured signal,
different transmitting technologies may be implemented as per requirement.
For hardware implementation, a test model was designed and built. A model
hopper was designed by scaling down the actual size of a hopper. The upper and
15 lower surfaces of the model hopper were of square shape. The actual size of the
lower surface and the upper surface was taken 250 mm*250 mm and 600 mm *
600 cm. The height of the hopper was 4 feet. Walls of the model were prepared
by using the galvanized sheet. For easy outflow of the inside material, the model
enclosed compartment for storing fly ash was equipped with a provision to open
20 up in the lower surface of the model. As per the design of the sensor, it was best
to install them at the lower surface of the hoppers. Accordingly, at the four sides
of the lower surface, four galvanized sheets width of 30 mm were welded along
the periphery and just above its bottom surface in such a way that the opening
of the hopper was not get hampered. As the width of the welded portion was
25 negligible compared to the opening diameter of the hopper, it did not obstruct
the ash at the time of drain out. Four sensing units were installed along the
periphery of the welded metal to get more accurate results.
The both ends of the piezo-laminated aluminum scaffold were fixed using screw
arrangement maintaining a slight gap between the lower metal surface and the
11
piezoceramic patch, so that the beam along with the two piezo-patches was able
to vibrate freely. All the required electrical connections were inserted inside the
model hopper and covered with an electrical insulating pipe. The sensing units
were covered with heat insulation cotton pad and insulating Kapton adhesive
5 tape to protect it from the direct contact of the ash. So, the ash could not come
with direct contact of the sensing unit. The sensing unit of the model hopper was
connected with a signal conditioning circuit, an indicating system; and a signal
transmission system to obtain a fly ash level measuring device.
Between the two piezoelectric sensors (the first and second piezoelectric
10 sensor), laminated on aluminum scaffold, one followed a reverse piezoelectric
effect and another one followed the piezoelectric effect. An input AC voltage of
230 Volt, 50 Hz was supplied as an excitation voltage to the first piezoelectric
sensor of the sensing unit, which was present on the aluminum beam, and which
was installed on the lower side of the test enclosed compartment. The supplied
15 input AC voltage acted as an excitation voltage for a first piezoelectric sensor of
the sensing unit, and according to the reverse piezoelectric effect, the first
piezoelectric sensor produced an equivalent vibration within it.
As the piezoelectric sensors were firmly attached to the aluminum scaffold,
therefore piezo-ceramic patch on the other side of the beam (the second
20 piezoelectric patch of the sensing unit) felt the vibration too and acted as per the
piezoelectric effect.
When the model enclosed compartment was empty (no ash inside the hopper),
the second piezo-ceramic patch did not feel any external pressure on it, and
produced an output AC voltage with the same amplitude and frequency, given as
25 the input AC voltage to the first piezoelectric sensor.
However, as the sensing units were fixed at both ends and the piezoelectric
sensors are attached with Araldite, some of the vibration got damped due to
these two factors viz. external pressure and attachment with the scaffold. So,
when there was no ash inside the test enclosed compartment, the sensing unit
12
or the actuator piezoelectric sensor produced the highest output voltage with
the same as of the input frequency. As the level of fly ash increased, it felt
pressure on it, its vibration got damped and the output AC voltage reduced too.
Here the sensing unit acts both as the exciter section and the sensing and
5 actuator section.
For the experiment, dry sand was used to fill and check inside the hopper. As
sand has the greater density than fly ash, so it was observed that the sensing unit
was much capable to withstand load and gave the actual load. The model hopper
was set on a stand, so that the lower surface could be opened easily and the
10 inside material could come outside smoothly. To check the level of sand inside
the test hopper, one measuring tape was attached at the inside wall of the
model. During the experiment, an input AC voltage was supplied to all the four
sensing units and the output AC voltages was sent to the signal conditioning
circuit. The experiment was performed for 10 times: 5 times of loading and 5
15 times of unloading in the duration of 5 days. After 2 set of experiment (one
loading and one unloading), the test hopper was cleaned up to remove any
residual sand from any corner. The experiment was performed with 1 meter of
level of sand inside the hopper.
Example 3: Signal Conditioning Section
20 The signal conditioning circuit, the output AC voltage was converted into an
equivalent output DC voltage or a generated DC voltage. The signal conditioning
section comprises a rectifier and a filter circuit to convert an output AC voltage
from the sensing unit into a DC voltage.
In this specific design, as the enclosed compartment was filled with the ash, the
25 amplitude of the output voltage started to be damped. It was observed that the
amplitude of the output AC voltage decreased gradually as the ash level inside
the hopper increased. More specifically, the ash level was a function of the
amplitude of the output AC voltage of sensing and actuating circuit, so the
output AC voltage was required to be converted into DC voltage. The measured
13
voltages were passed through buffer, rectifier and filter circuits to get equivalent
DC voltage. In the proposed design 4 sensing units were used, therefore 4
separate rectifiers and filters were used for each of the sensing unit to get
equivalent DC voltage.
5 Example 4: Display section (or indicating system)
For a local indication or displaying purpose, microcontroller based transmitting
approach was used. For using microcontroller, first it was necessary to convert
the output AC voltage of the signal conditioning circuit in the range of the
operating input voltage of the microcontroller. But after passing through the
10 signal conditioning circuit, the output AC voltage was in the range of 1-5 Volt,
therefore no extra circuit was required for this purpose. The DC voltage from the
signal conditioning circuit was sent to the Arduino UNO which calculated the
actual ash level and displays it on a LCD. The calculated ash level was then
displayed on a 16×2 LCD.
15 Example 5: IOT section (Signal transmission system)
To access the data remotely, an IoT based signal transmission system was
implemented. The signal transmission system was designed using ESP 8266 and
Arduino.
20 ADVANTAGES
• Due to employment of the piezoelectric sensor-based ash level
measurement system, better consistency in the results is achieved. The
piezoelectric sensor-based ash level measurement system of the present
25 invention is free from any inconsistency due to deposition of the fly ash
on the sensors;
• The piezo-based system/device of present invention is very much reliable
and hustle-free;
• Cost effective;
14
• No need to recalibrate very frequently and provides accurate and precise
results;
• Long life-span;
• The sensor efficiently works inside the ash hopper and measures the
5 height of the ash level accurately;
• The sensors of the device can withstand a temperature ranging from 200o
C-250 oC; and
• The results can be access remotely due to implementation of an IoT
based signal transmission system.

I/We claim:
1. A fly ash level detection module comprising a sensing unit, wherein said
sensing unit comprises a first piezoelectric sensor; a second piezoelectric
5 sensor, wherein said first and second piezoelectric sensors are paired; and a
metal scaffold, wherein said first and second piezoelectric sensors are
detachably attached to the scaffold at a pre-determined distance from each
other, and the scaffold is able to freely vibrate.
10 2. The fly ash level detection module as claimed in claim 1, wherein there is an
air-gap between the metal scaffold and the attached first or second
piezoelectric sensors.
3. A fly ash level detection device comprising:
15
- at least a fly ash level detection module as claimed in claim
1;
- a signal conditioning circuit capable of converting an output
20 AC voltage from the second piezoelectric sensor of the
sensing unit to a generated DC voltage;
- at least an indicating system comprising at least an
audio/visual output device;
25
- at least a signal transmission system capable of transferring
data between the fly ash level detection device and a
remote device; and
16
- at least a hardware module electrically connected to at least
the signal conditioning circuit and the signal transmission
system.
5 4. The fly ash level detection device as claimed in claim 3, wherein the
audio/visual device can be a speaker, LED, and combinations thereof.
5. The fly ash level detection device as claimed in claim 3, wherein the signal
transmission system comprises at least a wireless and/or wired module for
10 transferring data between the fly ash level detection device and a remote
device.
6. The fly ash level detection device as claimed in claim 3, wherein the
hardware module is capable of receiving the generated DC voltage and
15 generates at least a signal, wherein said at least a generated signal is based
upon correlated values of generated DC voltage and at least a reference
value.
7. The fly ash level detection device as claimed in claim 3, wherein said device
20 comprises 4 fly ash level detection modules.
8. An enclosed compartment for storing fly ash, wherein said compartment
comprises at least a fly ash level detection device as claimed in claim 3.
25 9. A method for detecting fly ash levels in an enclosed compartment as claimed
in claim 8, the method comprising the steps of:
a. supplying an input AC voltage to at least a fly ash level
detection module of a device as claimed in claim 3;
17
b. detecting an output AC voltage generated by a second
piezoelectric sensor and converting the detected output AC
voltage to a generated DC voltage by the signal conditioning
5 circuit of the device;
c. generating at least a signal by the hardware module by
comparing the generated DC voltage with at least a reference
value, wherein at least a reference value is correlated with at
10 least a fly ash level; and
d. displaying the generated signal by the indicating system,
and/or transmitting the generated signal by the signal
transmission system.