FIELD OF THE INVENTION
The disclosure relates to a methodology for in-situ non-destructive measurement of bulk
density of compacted granular solids using ultrasonic method. Particularly the disclosure
relates to in-situ bulk density measurement of stamp charge coal cakes in coke oven
batteries of an integrated steel plant.
BACKGROUND OF THE INVENTION
Coke oven batteries utilize stamp charged coal cakes for production of high quality blast
furnace coke. Crushed coal blends are physically stamped and compacted to a certain bulk
density in a Stamping Charging Cum Pushing (SCP) machine. Achieving a particular bulk
density (≈1150 kgm-3) is extremely critical to both the quality of coke produced and the
efficiency of coking operation. At the same time, it is imperative to achieve uniform bulk
density of the stamped coal cake across the coal cake. The coal cake should be dense
enough to achieve sufficient strength and at the same time have sufficient porosity for
minimizing energy consumption in the oven during coking operation. A very high bulk
density will result in excessive swelling of that region of the cake during coking operation
within the oven. This will exert pressure on the side walls of the coke oven and damage
the inner linings resulting in huge capital loss.
On the contrary, a low bulk density will reduce the operational efficiency of coking oven
and may even result in loss of stability of the coal cake causing it to collapse under its self-
weight. Thus it is of paramount importance to maintain adequate and uniform bulk density
during stamping operation in SCP machine. In-situ measurement of bulk density profile
across the cake will aid in optimizing the coking operation in the coke oven for energy
consumption and quality of coke produced.

PRIOR ART:
CN102759385 describes a method for measurement of bulk density of coal cakes by cutting
a plurality of coal cakes having a regular shape at different locations of the coal cake to
obtain the plurality of briquettes and then calculating the bulk density of each piece of coal
cake using the relationship:
Bulk Density = (Mass of coal briquette) / (Volume of coal briquette)
and then calculating the average bulk density of coal cake by calculating the average bulk
densities of each briquette. The method described is a destructive method and thus cannot
be employed on a continuous basis. The extraction of briquettes will also consume
significant operation time of the coke oven.
KR2010078317A describes a method for measuring the bulk density of coal by extracting a
sample of coal from a conveyor feeding coal to the coke oven. The extracted coal is
diverted into a reservoir where the mass and volume of the coal is measured and used to
calculate the bulk density. The method described is for free coal samples before the
stamping operation. The bulk density of the coal will change significantly after stamping
which cannot be determined with the mentioned prior art.
OBJECTS OF THE INVENTION
In view of the foregoing limitations inherent in the prior-art, it is an object of the disclosure
to propose a system for measuring the bulk density of coal cake inside the stamp box of
stamping charging cum pushing (SCP) machine.
Another object of the disclosure is to propose a system for regulating the number of
stamps to be applied to the coal cake inside the stamp box of stamping charging cum pushing
(SCP) machine to achieve maximum efficiency.

Still another object of the disclosure is to propose a system for in-situ measurement of bulk
density of stamp charge coal cakes at the stamping charging cum pushing (SCP) machine
of coke oven batteries.
Still another object of the disclosure is to propose a system for achieving uniform bulk
density of stamp charge coal cakes at the stamping charging cup pushing (SCP) machine of
coke oven batteries.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The characteristics mentioned in the disclosure are the appended description. The
disclosure discloses the preferred mode of use along with objectives and advantages. The
disclosure will best be understood by reference to the following detailed description of
embodiment when read in conjunction with the accompanying figures. The embodiments
are described, by way of example only, with reference to the accompanying figures.
FIG. 1a illustrates a conventional stamp box.
FIG. 1b illustrates an isometric view of the conventional stamp box.
FIG. 1c and 1d illustrates a stamp box system in accordance with various embodiments of
the disclosure.
FIG. 2 illustrates the regression analysis for a coal in accordance with one of the
embodiment of the disclosure.
The figures depict embodiments of the disclosure for purposes of illustration only. The
skilled person in art will identify from the following description that alternative
embodiments of the structures and methods illustrated may be worked upon without
departing from the concept of the disclosure.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE DISCLOSURE
The foregoing outlines the features and technical advantages of the present disclosure
have in broader sense. Additional features and advantages of the disclosure will be
described hereinafter which form the subject of the claims of the disclosure. It should be
appreciated by the person skilled in art that the concept and specific embodiment disclosed

may be utilized as a basis for modifying or designing other structures for carrying out the
same purposes of the disclosure.
It should also be understood by the person skilled in the art that such equivalent
constructions do not depart from the scope of the disclosure as set forth in the appended
claims. The characteristic features of the disclosure together with further objects and
advantages will be better understood from the description when considered in connection
with the accompanying figures. The figures provided does not intended as a definition of
the limits of the present disclosure.
Variations such as “comprises”, “comprising”, does not intend to include only those
components mentioned for the system or steps but may include other components or steps
not expressly listed or inherent to such setup.
Various embodiments of the disclosure provide a stamp box system for stamping charging
cum pushing (SCP) machine, comprising: a plurality of ultrasonic sensors deployed over a
retractable walls of SCP machine, one of the walls being deployed with transmitters and
the opposite being deployed with receivers of the sensors, the transmitter and the receiver
being configured to assess the time of flight of ultrasonic pulse through a coal cake; each
sensor being guided by a corresponding ultrasonic transducer arrangement, each ultrasonic
transducer arrangement being configured to establish perfect acoustical contact between
the coal cake, the transmitter and the receiver, the ultrasonic transducer arrangement
comprising a cylindrical sleeve, inner of the cylindrical sleeve comprising a cylindrical
coupling, a vertical gap being provided between the cylindrical coupling and the cylindrical
sleeve at curve to deploy a load cell; each sensor being positioned inside the cylindrical
sleeve at a distance from the cylindrical coupling and a spring fixed over the cylindrical
coupling to rigidly hold the sensor, the sensor being in lubrication with the cylindrical
sleeve, the ultrasonic transducer arrangement further comprising a track over which the
cylindrical sleeve can extend and retract along with the cylindrical coupling under the push
a stepper motor and a lead screw causing no relative motion between the cylindrical

sleeve, the cylindrical coupling and the sensor; the stepper motor and the lead screw being
positioned at the cylindrical sleeve to drive the transmitter and receiver of the sensor to
extend towards coal cake inside the stamp box system until the event of causing perfect
acoustical contact between coal, transmitter and receiver, as indicated by the load cell and
causing the stepper motor to stop and obtain ultrasonic time of flight measurement; and
the sensor being coupled to a Multi-Channel Ultrasonic Pulser Receiver Probe Positioning
Controller which is further coupled to Data Acquisition & Bulk Density Analysis System,
DABDAS and the DABDAS is further coupled to a stamp controller, the controller is
configured to receive signal from the sensor and conveyed to the DABDAS to assess the
bulk density of coal cake by manipulating time of flight at the measured point and sending
the signal to a stamp controller, the stamp controller being configured to regulate the
number of stamps, if required, to achieve requisite bulk density.
Shown in FIG. 1a is a conventional stamp box (100) and a coke oven battery (104) utilizing
stamp charged coal cakes for production of high quality blast furnace coke. Crushed coal
blends are physically stamped and compacted to a certain bulk density in a stamp box
(100) of Stamping Charging Cum Pushing (SCP) machine.
Shown in FIG. 1b is an isometric view of the conventional stamp box (100) along the axis
of the motion of its various walls. The stamp box (100) comprises a retractable side walls
(108a, 108b), a front charging door (112) and a back plate cum pushing mechanism (116).
Once a coal cake (120) achieves the requisite bulk density, the retractable side walls (108a,
108b) retracts in Z-Z direction, the front charging door (112) lift itself up (in X-Y direction)
and the back plate cum pushing mechanism (116) slides towards the coke oven battery
(104) (in X-X direction). This sliding will make the coal cake (120) to move along and dump
it into the coke oven battery (104).

Crushed coal is poured in the stamp box (100) from a coal tower situated above the SCP
machine. Series of a mechanical stampers (124) are used to stamp the crushed coal
charged into the stamp box (100) (shown in FIG. 1A). At the end of compacting process
the coal cake (120) is formed with requisite bulk density.
The dependence between ultrasonic wave velocity, density and elastic properties of
isotropic media is well known. Similar relationships have also been studied for rigid porous
media like wood, ceramics, cancellous bone etc. The nature of ultrasonic wave propagation
in granular media like hydrating cement, sand, etc. have also been explored in prior art.
Stamp charged coal cakes however are not highly rigid and can be considered as
compacted-hydrated-granular media.
Shown in FIG. 1C is a stamp box system (102) of SCP machine in accordance with various
embodiments of the disclosure. A plurality of ultrasonic sensors (132) deployed over its
retractable side walls (108a, 108b).
Out of the two, one of the retractable wall are deployed with transmitters (T) and the
opposite being deployed with receivers (R) of the ultrasonic sensors (132). The transmitter
and the receiver are configured to assess the time of flight of ultrasonic pulse through the
coal cake in the stamping box system (102). This time of flight can be later on utilized to
calculate the bulk density of the coal cake.
It is found that the axial load either applied externally or exerted by the compacted coal
cake on the sensor have an effect on the ultrasonic velocity measurements. It is thus
important to position the transmitter and the receiver at constant axial load condition for
accurate bulk density measurement. For that reason each sensors (132) need to establish
perfect acoustical contact at constant axial load condition between the coal cake (120), the
transmitter (T) and the receiver (R). Each sensor (132) is guided by a corresponding
ultrasonic transducer arrangement (144) to establish perfect acoustical contact between
coal cake at constant axial load condition, the transmitter and receiver. The ultrasonic

waves generated from the transducer traverses through the coal cake (120) and are
detected by the receivers (R).
The transducer arrangements (144) are placed along the edge of the coke oven in a way
that there is sufficient clearance between the front face of the transducer and the coal cake
when the coal cake is in motion while being pushed into the coke oven.
In accordance with an embodiment of the disclosure, ultrasonic sensors having frequency
of 20-50 KHz can be used.
Assuming the time of flight of the ultrasonic wave through the coal cake as “T” and the
thickness of the coal cake “B”, the velocity of propagation of ultrasound in the coal cake
“V” can be calculated by Equation 1.

This velocity depends upon various properties of the coal cake like bulk density, moisture
content, packing fraction etc.
The relationship between ultrasonic velocity and bulk density needs to be identified by
means of regression analysis of large number of measurements.
In accordance with one of the embodiment of the disclosure, FIG. 2 shows the data from
the regression analysis for the coal used having properties of ash content 14% by wt.,
volatile matter content 22% by wt., crucible swelling no. 5, particle size distribution 90%
below 3.15 mm, moisture content: 10-12% by wt.
The relationship for the said coal has been identified as
Bulk Density (Y) = (V+238.57)/0.388
For separate coal properties separate relationship need to be established.

Shown again in FIG. 1c is the ultrasonic transducer arrangement (144) corresponding to
each sensor (132). The ultrasonic transducer arrangement (144) comprises a cylindrical
sleeve (148). The cylindrical sleeve (148) comprises a cylindrical coupling (152) at inner
side. The cylindrical coupling (152) carries the sensor (132) inside at a distance and a
spring (156) is fixed over the cylindrical coupling to rigidly hold the sensor (132).
The sensor (132) positioned within the cylindrical sleeve (148) is well lubricated with. This
enables frictionless lateral motion (extension and retraction) of the sensor (132) within the
sleeve (148). The ultrasonic transducer arrangement (144) further comprises a track (164)
over which the cylindrical sleeve (148) can extend and retract along with the cylindrical
coupling (152). A stepper motor (168) and a lead screw (172) is coupled at the end of the
cylindrical sleeve (148) to push the sleeve, thereby pushing transmitter and receiver of the
sensor (132) inside of the stamping box system (102).
A vertical gap is provided between the cylindrical coupling (152) and the cylindrical sleeve
(148) at a curve to deploy a load cell (160).
The stepper motor (168) and the lead screw (172) are positioned at the cylindrical sleeve
(148). The push by the motor (168) and the lead screw (172) does not cause any relative
motion between the cylindrical sleeve (148), the cylindrical coupling (152) and the sensor
(132). The push by the motor continues until the perfect acoustical contact between coal
cake (120), the transmitter (T) and the receiver (R), is achieved. This perfect acoustical
contact is indicated by the load cell (160) which causes the stepper motor (168) to stop
and obtain ultrasonic time of flight measurement.
At the time when measurement is to be taken the stepper motor (168) is actuated which
pushes sensor (132), cylindrical sleeve (148), spring (156), cylindrical coupling (152) and
the load cell (160) along the track (164). This forward motion continues till the front face
of the sensor (132) touches the coal cake. Once the sensor is in contact with the coal cake;
additional forward motion causes the spring (156) to compress thereby transferring the
axial load experienced by the transducer to the load cell (160) through the cylindrical

coupling (152). The readout from the load cell (160) can be utilized to stop the motor
(168) and restrict the forward motion such that the ultrasonic sensor (132) experiences a
predetermined axial load. The same cut-off for axial load is to be used for all the ultrasonic
transducer arrangements (144) so that consistent bulk density measurements are ensured.
Shown in FIG. 1d is the deployment of a stamp controller (176), Data Acquisition & Bulk
Density Analysis System, DABDAS (180), and a Multi-Channel Ultrasonic Pulser Receiver
Probe Positioning Controller (184). The sensor (132) is coupled to a Multi-Channel
Ultrasonic Pulser Receiver Probe Positioning Controller (184), the controller (184) is
coupled to a Data Acquisition & Bulk Density Analysis System, DABDAS (180). The DABDAS
(180) is coupled to the stamp controller (176).
The DABDAS (180), a Multi-Channel Ultrasonic Pulser Receiver Probe Positioning Controller
(184) and the stamp controller (176) can be integrated in one single hardware.
The Multi-Channel Ultrasonic Pulser Receiver Probe Positioning Controller (184) is
configured to receive the signal from the sensor and send the signal to the DABDAS (180).
The Controller (184) is further configured to control the motion of the sensors (132). Once
the data is received by the DABDAS (180), it manipulates the same in the form of bulk
density of the coal cake and compares the same with threshold bulk density and assesses
the number of stamping, if required. The required number of stamping is conveyed to the
stamping controller (176) in the form of a signal. The stamping controller (176) is further
coupled to the mechanical stampers (124) and stamps it over the coal cake to achieve
requisite bulk density.
The number of stamps (n) is calculated based upon the following equations :


where; £ is the specific stamping energy to achieve a final bulk density Pc, £0 is the specific
stamping energy for an intermittent stamping step with bulk density Pl}, maximum drop
height of stamper Smai, intermittent height of stamped coal cake 5 and stampability of coal
blend K.
The stampings by the mechanical stampers are controlled by means of a stamping
controller (176) coupled in between the mechanical stampers and Data Acquisition & Bulk
Density Analysis System.
In accordance with an embodiment of the present disclosure the stamp box system (102)
can be enabled in-situ measurement of bulk density of the coal cake while being pushed
into the coke oven (104).
The descriptions of specific embodiments of the disclosure have been presented for
purposes of illustration. They do not intended to be exhaustive or to limit the present
disclosure to the specific and stricter forms disclosed and various modifications and
variations are possible in the light of the disclosure. The embodiments mentioned are the
best one to describe the concept of the disclosure. This enables the person skilled in the
art to best utilize the present disclosure and its various embodiments with various
modifications as are suited to the particular use. It is possible that various diverse
equivalents are contemplated as per the circumstances, but such are intended to cover the
application or implementation without departing from the true spirit or scope of the present
disclosure.

WE CLAIM:
1. A stamp box system (102) for stamping charging cum pushing (SCP) machine,
comprising:
a plurality of ultrasonic sensors (132) deployed over a retractable walls (108a, 108b)
of SCP machine, one of the walls being deployed with transmitters and the opposite
being deployed with receivers of the sensors (132), the transmitter and the receiver
being configured to assess the time of flight of ultrasonic pulse through a coal cake
(120);
each sensor (132) being guided by a corresponding ultrasonic transducer
arrangement (144), each ultrasonic transducer arrangement (144) being configured
to establish perfect acoustical contact between the coal cake (120), the transmitter
and the receiver, the ultrasonic transducer arrangement (144) comprising a
cylindrical sleeve (148), inner of the cylindrical sleeve (148) comprising a cylindrical
coupling (152), a vertical gap being provided between the cylindrical coupling (152)
and the cylindrical sleeve (148) at curve to deploy a load cell (160);
each sensor (132) being positioned inside the cylindrical sleeve (148) at a distance
from the cylindrical coupling (152) and a spring (156) fixed over the cylindrical
coupling to rigidly hold the sensor (132), the sensor (132) being in lubrication with
the cylindrical sleeve (148), the ultrasonic transducer arrangement (144) further
comprising a track (164) over which the cylindrical sleeve (148) can extend and
retract along with the cylindrical coupling (152) under the push a stepper motor
(168) and a lead screw (172) causing no relative motion between the cylindrical
sleeve (148), the cylindrical coupling (152) and the sensor (132);
the stepper motor (168) and the lead screw (172) being positioned at the cylindrical
sleeve (148) to drive the transmitter and receiver of the sensor (132) to extend

towards coal cake inside box until the event of causing perfect acoustical contact
between coal, transmitter and receiver, as indicated by the load cell (160) and
causing the stepper motor (168) to stop and obtain ultrasonic time of flight
measurement; and
the sensor (132) being coupled to a Multi-Channel Ultrasonic Pulser Receiver Probe
Positioning Controller (184) which is further coupled to Data Acquisition & Bulk
Density Analysis System, DABDAS (180) and the DABDAS (180) is further coupled to
a stamp controller (184), the controller (184) is configured to receive signal from the
sensor (132) and conveyed to the DABDAS (180) to assess the bulk density of coal
cake by manipulating time of flight at the measured point and sending the signal to
a stamp controller (176), the stamp controller (176) being configured to regulate the
number of stamps, if required, to achieve requisite bulk density.
2. The stamp box system (102) as claimed in claim 1 wherein the frequency of the
sensor is 20-50 kHz.