FIELD OF THE INVENTION
The present invention relates in general to density measuring apparatus, and in
particular to measurement of the bulk density of the stamped coal cake before
pushing the stamped coal coke inside the coke ovens i.e. measurement of the
bulk density of the coal cake at the stamped condition before pushing into the
coke ovens to produce coke.
BACKGROUND OF THE INVENTION
Coke causes up to 50% of the costs during the pig iron production. The cost
effective production of high quality coke is thus of prime importance for the
competitive ability of the iron producing industry. The stamp charging technology
such as combined machines (SCP-stamping charging pushing) offers a
considerable potential for reducing costs during the coke production: It enables
the economical production of high- and constant quality coke, also from high
volatile and low-quality coal. Even petrol coke and coke dust can be utilized.
During the stamp charging process the coal is stamped outside the coke oven,
into a single briquette “(coal cake), having almost the same dimensions as the
oven chamber. This coal cake reaches a density of up to 1.15 t/m³ (on wet coal
basis with 10% water) – about 30% more than with the loose coal-charge during
conventional top charging systems. The stamp charged coke making process has
several benefits like remarkable improvement in Coke Quality (CSR, CRI), Stamp
Charged Coke is about 35 % cheaper than Top Charged Coke, improvement of
yield of Blast Furnace Sized Coke, improvement of blast furnace productivity.
The bulk density of the stamped coal cake is an important indicator of the
assessment (coal cake achieves some Bulk density during stamping operation in
SCP machine), the bulk density of below standard, easily leads to the collapse of
coal, disrupting the rhythm of coke production. Further, the coking oven furnace
condition and its’ efficiency is also dependent on the bulk density of coal and its
moisture content. Thus, in order to ensure that the Coke ovens utilizing stamped
charged coal cakes for production of high quality blast furnace coke and facilitate
robust and energy efficient coking operation it is crucial to have a good control
over this stamping operation so as to achieve a uniform bulk density of coal cake
post stamping. In normal operation, the Bulk Density of Charged Coal Cake

~1150 kg/m3 while the bulk density varies during rainy season (1000 – 1150
kg/m3). Due to the variation in the bulk density, the operator faces an
undesirable high pushing force problem in response to which the operator
reduces the stamping time immediately, thereby reducing the bulk density. The
high pushing problem is encountered if at a certain moisture more bulk density
is there, more mass would be accumulated in a certain space which requires
more force to push the cake mass inside the oven. Since the aforementioned
mechanism is manual, hence the bulk density of the stamped coal cake cannot
be controlled with desired accuracy.
Further, the chamber (coke oven) is closed with a very hostile condition prevailing
around it which together make measurement of the Bulk density of the coal cake
inside the chamber impossible since there is no conventional sensor which could
be inserted to get the bulk density because the whole cake mass moves one stage
to another stage in a stipulated time. Moreover, no sensor can sustain such a
stamping jerk inside the coal coke during stamping operation.
In addition to the manual control, conventionally is disclosed an ultrasonic
technique enabling online measurement of bulk density during the stamping
operation. In one such technique disclosed in the conventional art, ultrasonic
response was found to have a straight line correlation with bulk density (wet
basis) and moisture content of stamped coal with an R2 value of 0.98. The effect
of moisture content in the coal on the ultrasonic measurements is also
discussed. A lab scale prototype was developed with integrated sensors to
emulate online measurement. The prototype was found to have a measurement
error of less than ± 1.6%. This method can also be suitably adapted for online
bulk density measurement of granular solids other than crushed coal. However,
the ultrasonic equipment is not at all cost effective since the cost of sensors and
allied accessories is high in ultrasound based technique.
Other conventional techniques for measurement of bulk density of coal on
conveyor belt use a radioactive nucleonic method. For example, in US3678268A
to Reim, the output of a radioactive source is directed through a moving stream

of granular material, e.g., coal on a conveyor, and the radiation passing through
is sensed by a detector. The detector generates a pulse signal of which the pulse
repetition rate varies with the radiation sensed. The pulses generated are counted
in a binary counter, and a timer periodically initiates a read-out of and resets the
counter to effect successive counting cycles, whereupon the digital count in each
cycle is converted to an analog voltage, the magnitude of which is recorded in
terms of bulk density of the coal. The recorder controls the addition of water or
oil to the coal to, respectively, lower or increases the bulk density of the coal.
Controls are included which guard the system from misperforming when a
supply of coal has failed, when the depth of coal on the conveyor belt has been
lost, and when the coal is so dense that an application of water is required.
However, the radioactive nucleonic method does not produced results of the
desired accuracy. Additionally, the radioactive nucleonic method is not used
widely due to the reasons such as radioactive hazards, space constraints and
high costs.
The other challenge related to the measurement of the bulk density of the
stamped coal pertains to the moisture variation in the range of 8.5% to 11%
moving material at temperature of 20-30 Degree C. Further, the intrusive sensor
cannot be used since the coal cake is moved into the oven furnace. Therefore,
there is a need to develop a unique bulk density measurement apparatus which
is simple, cost-effective, accurate, efficient and overcomes all the shortcomings
associated with the existing bulk density measurement systems.
OBJECTS OF THE INVENTION
It is therefore an object of the invention is to overcome the aforementioned and
other drawbacks existing in prior art systems for measurement of stamped coal
cake bulk density.
It is a primary object of the present invention to provide an apparatus for
measuring bulk density of stamped coal cake.
Still another object of the present invention is to provide an online real-time
measurement of coal bulk density in the SCP machine.

Yet another object of the present invention is to provide a non-intrusive
apparatus for measuring bulk density of stamped coal cake.
Further object of the present invention is to provide an apparatus facilitating
assessment of pushing force required to push the cake in oven chamber
through measurement of the Bulk density of the coal cake.
These and other objects and advantages of the present invention will be
apparent to those skilled in the art after a consideration of the following
detailed description taken in conjunction with the accompanying drawings in
which a preferred form of the present invention is illustrated.
SUMMARY OF THE INVENTION
In an aspect, the present application discloses an apparatus for apparatus for
online real-time measurement of bulk density of stamped coal. In an
embodiment, the apparatus includes a box of a fixed volume with pre-defined
dimension receiving stamped coal of different masses in fixed volume of the
box. Further, in an embodiment the apparatus includes two conductive plates
placed at two ends of the box containing the stamped coal mass where the two
conductive plates are connected to a DC voltage supply source and an
ammeter. Further, the conductive plates are positioned such that the density of
the stamped coal received into the box is according to current reflected by the
ammeter. Furthermore, the apparatus further includes an online real-time
control for controlling the mass of the stamped coal received by a coke oven
based on analysis of the current reflected by the ammeter each time coal of
equal or different mass is introduced in the box.
The above and additional advantages of the present invention will become
apparent to those skilled in the art from a reading of the following detailed
description when taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The above brief description, as well as further objects, features and
advantages, of the present invention can be fully appreciated by reference to

the following detailed description. These features of the present invention will
become more apparent upon reference to the drawings, wherein:
Figure 1: shows schematic of an apparatus for measuring bulk density of
stamped coal cake according to an embodiment of the present invention.
Figure 2: shows hardware components of the apparatus implemented for
measuring bulk density of stamped coal cake.
Figure 3: shows a relation between bulk density and current when the
moisture content in coal sample is 9%.
Figure 4: shows a relation between bulk density and current when the
moisture content in coal sample is 9.5%.
Figure 5: shows a relation between bulk density and current when the
moisture content in coal sample is 10%.
Figure 6: shows a relation between bulk density and current when the
moisture content in coal sample is 10.5%.
Figure 7: shows a relation between bulk density and current when the
moisture content in coal sample is 11%.
Figure 8: shows a relation between bulk density and current when the
moisture content in coal sample is 10%, 10.5%, and 11% said data being
obtained by combining data from Fig. 5-7.
DETAILED DESCRIPTION OF THE INVENTION
Although the disclosure hereof is detailed and exact to enable those skilled in
the art to practice the invention, the physical embodiments herein disclosed
merely exemplify the invention which may be embodied in other specific
structure. While the preferred embodiment has been described, the details may

be changed without departing from the invention, which is defined by the
claims.
It will be apparent, however, to one of ordinary skill in the art that the present
invention may be practiced without specific details of the well known
components and processes. Further specific numeric references should not be
interpreted as a literal sequential order. Thus, the specific details set forth are
merely exemplary. The specific details may be varied from and still be
contemplated to be within the scope of the present invention. The features
discussed in an embodiment may be implemented in another embodiment.
Moreover, occasional references to the conventional systems are made in order
to better distinguish the present inventive disclosure discussed later in greater
detail. Few of the details pertaining to said
apparatus/system/process/construction are well-known in the art and
therefore, are described herein only in the detail required to fully disclose the
present invention while unnecessarily obscuring the present invention. The
present invention will be described in detail below with reference to
embodiments as shown in the drawings.
In the present invention, for obtaining the bulk density B of coal at stamped
condition the changes of the ohmic resistance has been observed as per the
variation in Bulk density B at different moisture condition of coal cake. In an
embodiment, the apparatus consists of a two metallic plates with proper
insulation. The two metallic plates act as probe for the constant voltage
application across the coal mass and as per the variation in bulk density B the
variation in current flowing through the coal cake is measured. In another
embodiment, the probe is the surface finished probe to which is applied a
certain voltage and corresponding current through the coal mass with fixed
area of cross section is measured. The results are verified based on the
principle that the bulk density B is equal to the total mass divided by volume.
The factors based on which the bulk density B is assessed is enumerated
below:

1. More the bulk density B more the moisture content which increases the
Electrical Conductance of coal dust.
2. When a fixed DC voltage is applied across the solid mass with the increase
in conductance the value of current increases.
Further, the technical relations governing the assessment/measurement of the
bulk density B of the coal is discussed below:
K= m.D (1)
Where, K-Conductivity, D-Density of coal cake, m- Proportionality constant
C=K.A/L (2)
Where, C-Conductance, A-Area of sensing plate, L- distance between two
sensing plate.
I= C.V (3)
Where, I- The measured current, V- The Constant voltage applied
Now by combining the above three equation we can get
I= (m. A.V/L).D (4)
So, for certain length (L) and fixed area (A) of coke mass with fixed voltage (V)
we get that current (I) flowing through the coke mass is directly proportional to
the Bulk density B (D) of the certain percentage moist coal.
As shown in FIG. 1, Two conductive plates (x,y) which may be made of
aluminium has an area of cross section 50 mm X 50 mm is placed across the
stamped mass of the coal cake of length 483 mm as like the actual cake
thickness in coke oven battery. A fixed D.C voltage is applied across the two
aluminum plates and current being measured at different mass stamped at
same volume of the test box 1. Finally, the mass of stamped coal which is

pushed into the furnace based on multiple iterations is decided through
standard calibrated weighing machine.
Further, in Fig. 2 disclosed is an apparatus for online real-time measurement
of bulk density “B” of stamped coal 5. In an embodiment, the apparatus
comprises a box 1 of a fixed volume defined with pre-defined inner dimensions
receiving stamped coal 5 of different masses in fixed volume of the box 1.
Further, the apparatus comprises two conductive plates (x, y) placed at two
ends of the box 1 containing the stamped coal 5 mass, wherein the two
conductive plates (x, y) are connected to a DC voltage supply 3 source and an
ammeter 2, and wherein the conductive plates (x, y) are positioned such that
the density of the stamped coal 5 received into the box 1 is in proportion to
current reflected by reading on the ammeter 2. Furthermore, in an
embodiment, on the walls of the conductive plates a parallel plate capacitor is
arranged on each plate which is in parallel with proper insulations with the
metallic wall and current drawn is mapped with stamped charged bulk density
of coal. Further, in an embodiment, the apparatus further comprises an online
real-time control for controlling the mass of the stamped coal 5, received by a
coke oven. In an embodiment, the control is based on analysis of the current
reflected by the ammeter 2 each time coal of equal or different mass is
introduced in the box 1. Herein, the current reflected by the ammeter 2 is
indicative of the moisture content of the stamped coal 5 and in turn bulk
density “B” of the stamped coal 5.
Numbers of different experiments had been carried out by measuring the
current and mass in fixed volume as per the test set up shown in FIG. 2. The
total assembly has been made in steel box 1 having pre-defined inner
dimension of 483 mm x 52mm x 52 mm to withstand the stamped strength
and total box 1 is being insulated with perplex sheet of 4 mm thickness. Two
aluminum plates (x,y) are placed as shown in Fig. 2 & 3. In an embodiment, 24
Volt DC voltage is applied and ammeter 2 is being connected to measure the
current variation as per the coal mass is stamped in fixed volume of the box 1.

The schematic of the hardware setup with detail configurations are shown in
(FIG.2). The data captured can be plotted with different moisture condition
which shows the changes in electrical current as per the measured bulk
density B by weight method effect (FIG. 3-Fig.8).
Importantly, Fig. 8 shows a relation between bulk densities and current when
the moisture content in coal sample is 10%, 10.5%, and 11% said data being
obtained by combining data from Fig. 5-7. As percentage of moisture in coal
for coke plant varies in the range from 10 to 11, collating the data for moisture
range of 10, 10.5 and 11%, it has been observed that linearity exits between
bulk density and DC current with R2 error (coefficient of determination) of
88.30%.
The foregoing is considered as illustrative only of the principles of the
invention. Furthermore, since numerous modifications and changes will readily
occur to those skilled in the art, it is not desired to limit the invention to the
exact construction and operation shown and described. While the preferred
embodiment has been described, the details may be changed without departing
from the invention, which is defined by the claims.

We claim:
1. An apparatus for online real-time measurement of bulk density (B) of
stamped coal (5), the apparatus comprising:
a box (1) of a fixed volume defined with pre-defined inner
dimensions receiving stamped coal (5) of different masses in fixed
volume of the box (1);
two conductive plates (x, y) placed at two ends of the box (1)
containing the stamped coal (5) mass, wherein the two conductive
plates (x, y) are connected to a DC voltage supply (3) source and an
ammeter (2), and wherein the conductive plates (x, y) are
positioned such that the density of the stamped coal (5) received
into the box (1) is in proportion to current reflected by reading on
the ammeter (2);
an online real-time control for controlling the mass of the
stamped coal (5), received by a coke oven, wherein said control is
based on analysis of the current reflected by the ammeter (2) each
time coal of equal or different mass is introduced in the box (1).
2. The apparatus as claimed in claim 1, wherein the box (1) is made of
steel.
3. The apparatus as claimed in claim 1, wherein the pre-defined inner
dimension of the box (1) is 483 mm x 52mm x 52 mm.
4. The apparatus as claimed in claim 1, wherein the current reflected by
the ammeter (2) is indicative of the moisture content of the stamped coal
(5) and in turn bulk density (B) of the stamped coal (5).
5. The apparatus as claimed in claim 1, wherein the two conductive plates
(x, y) are made of aluminium having dimension of 50 mm x 50 mm.

6. The apparatus as claimed in claim 1, wherein the box (1) is insulated
with perplex sheet of 4mm thickness.