FIELD OF THE INVENTION:
The present invention relates to a testing process to evaluate
adhesion strength between old and new clay adaptable to taphole of
Blast Furnace and testing apparatus to carry out the method.
More specifically the present invention relates to evolution of
adhesion strength between old and new clay mud at taphole of Blast
Furnace simulated to blast furnace conditions.

BACKGROUND OF THE INVENTION
WITH DIFFICULTIES OF PRIOR ART
Taphole clay is used for purpose of plugging of taphole and discharge of iron and
slag produced inside blast furnace. The mud gun inject or extrude the taphole
clay into taphole of blast furnace where it hardens and block the hot metal and
slag to come out from inside of blast furnace whereas drilling machine drill
taphole clay in order to make hole or path for discharging iron and slag produced
inside blast furnace. The performance of taphole clay is of fundamental
importance to the successful running of a blast furnace. The taphole length,
tapping duration and tapping rate are directly related to uniform furnace
performance. The life of a blast furnace depends largely on the erosion of
refractory lining of the hearth wall. One of the major operating factors that
affect the erosion is metal flow in the hearth, especially, the extent of
circumferential flow near the hearth wall region. The intensity of the
circumferential flow is affected by the taphole length. A longer taphole reduces

the intensity of metal flow in the circumferential region, and reduces the wall
lining erosion. A shorter taphole enhances the circumferential flow and increases
the wall lining erosion. In consequence, the control of the taphole length is
regarded as one of the indispensable measures to achieve longer blast furnace
life. Basically taphole clay is expected to protect hearth side wall by creating
protection layer of clay called mushroom around inside opening of taphole.
Longer taphole length can be achieved only if the injected mud stays at around
the in-furnace taphole opening and sinters there. To achieve the above condition
it is necessary that the clay mud injected by mudgun should adhere well with the
already existing clay mud. A test method has been innovated in order to
measure the adhesion characteristics (strength) between old and new clay mud
developed at high temperature. The present invention has proposed to enchance
Blast Furnace life in a new approach of quantifying adhesion strength between
old and new clay mud at taphole.

Earlier method (published paper in "AISTECH 2004 Proceedings-Vol-1" titled
"Taphole clay for Blast furnace" discloses a method for measuring adhesiveness
between old and new clay mud under the subheading of "Excellent
adhesiveness") for checking adhesion quality of taphole clay involve silicon
carbide crucible, after filling the crucible with taphole clay firing is to be done
under reducing environment at 1450°C for 3 hrs after cooling, the crucible is cut
into two halves in order to see qualitatively whether taphole clay had stick with
crucible wall or not. Above method of checking adhesion characteristics of
taphole clay is inefficient in terms of differentiating different qualities of taphole
clay adhesion characteristics which seems to be adhered (stick) with crucible side
wall. With this method it is difficult to find out the value of adhesion strength
between old and new taphole clay. Moreover this test method cannot be used to
determine the adhesion characteristics between old and new clay mud. In order
to differentiate adhesion characteristics of different type of taphole clay
quantitative measurement of adhesion strength is necessary.

BRIEF DESCRIPTION OF THE INVENTION
According to one object of the invention a test method of quantification of
adhesion strength between old and new clay at taphole is proposed.
Another objective of the invention is to predict the performance of taphole clay in
terms of achieving long taphole length in actual blast furnace condition
ascertaining adherence of new taphole clay mud pushed by mud gun into
taphole with the already existing old taphole clay in front of inside opening of
taphole.
The major problem involved in earlier art is its inability to quantify the adhesion
strength, also in earlier art result consist only qualitative observation of adhesion
or sticking behaviors of taphole clay with silicon carbide crucible wall, but in the
proposed invention the objective is to measure the adhesion characteristics
(strength) between old and new clay mud developed at high temperature.

The testing procedure developed according to the invention is best understood
from the following flow chart.


The invention will be better understood from the following description with
reference to accompanying drawings in which
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Figure 1 shows a compact old clay sample by Marshal Load Test equipment.
Figure 2 shows the drilled clay sample after firing at required temperature.
Figure 3 shows schematically ejection of new clay from the old clay in CCS
Machine to determine adhesion strength.
Figure 4 shows Marshal Load Test Equipment.
In the test method according to the invention a cylindrical shaped compact clay
sample (1) is first prepared from Marshal Load test equipment (basically it is a
simulation test of mud-gun taphole clay pushing process) and is first fired at

around 1300 ~ 1500°C and soaked for some specified time (say 2-5 hr) under
reducing environment. After firing, a hole (25 ~ 50 mm dia.) (2) is drilled
through the center of clay sample. After filling drilled hole with new taphole clay
mud (4) the sample is again fired at around 1300 ~ 1500°C and soaked for some
specified time (say 2-5 hr). In order to quantify the adhesion strength between
newly filled taphole clay and cylindrical shaped already fired old taphole clay, a
load is applied with the help of cold crushing strength (CCS) equipment only on
new clay mud which had been filled in drilled hole. Adhesion strength (value) is
the maximum load at which new clay mud starts to extrude out from old clay
mud. Figure 3 shows the way load is applied only on new taphole clay mud with
the help of CCS machine. In Figure 3, plunger (8) exerts pressure on the new
clay (4) filled in the hole of compact old clay sample (1), number (6) showing the
base of the CCS machine. Thus the new method not only solves the purpose of
quantification of adhesion strength as well as involves clay-to-clay direct
adhesion.

DETAILED DESCRIPTION OF THE
INVENTION WITH ILLUSTRATION
The main objective of new testing method is to simulate the actual blast furnace
condition as much as possible. In actual blast furnace condition first, taphole
clay mass is fed into the barrel of mudgun, where generally temperature lies
around 60 -70° C and consequently it is pushed by piston of mudgun in dense
compact form into blast furnace taphole.
In order to simulate above condition in lab, 1 kg of taphole clay sample is kept in
the oven where temperature lies around 60° C for one hour. After taking out
from oven the sample (1) is kept in the pre-lubricated mould of marshal load test
equipment (Figure 4 shows Marshall load test equipment) then the plunger (3) of
Marshal Load test Equipment is placed vertically above the clay sample (1) and
pressure applied slowly with the help of hydraulically operated piston. At a
certain pressure (depends on plasticity of taphole clay) clay sample starts to

extrude out from mould nozzle and forms compact cylindrical shaped sample.
Dial gauge (7) of Marshal Load test equipment shows the pressure at which clay
sample starts to extrude out from mould nozzle. Figure 1 shows the cylindrical
shape clay sample (1) obtained from Marshal Load test equipment. This
cylindrical shaped clay sample is then kept in atmospheric controlled furnace
under reducing environment and fired at around 1300~ 1500° C and soaked for
some specified time (say 2-5 hr.). After cooling this fired sample, a hole (2)
(25~50 mm dia.) is drilled through the center of sample.
Figure 2 shows drilled taphole clay sample. This drilled hole (2) is filled with the
new taphole clay of same quality, preheated at 60° C to 70° C for one hour in the
oven. The whole arrangement is kept inside atmospheric controlled furnace
under reducing environment and fired at around 1300~1500° C and soaked for
some specified time (say 2-5 hr).

After taking out the above sample from furnace the hole filled up sample is kept
on cold crushing strength machine as shown in Figure 3. Then the load is
applied with the help of CCS machine through plunger (8) only on clay sample
filled in drilled hole. Maximum load at which new clay mud starts to extrude out
from cylindrically shaped old clay mud gives adhesion strength of particular
quality of taphole clay.
The invention as narrated herein should not be read and construed in a
restrictive manner as various modifications, alterations of dimensions of sample
and test conditions and adaptations are possible within the scope and ambit of
the invention as defined in the encompassed appended claims.

WE CLAIM:
1. A testing process to evaluate adhesion strength between old and new clay
adaptable to taphole of Blast Furnace comprising the steps of:
- keeping predetermined quantity of taphole clay sample in an oven at 60 -
70°C for an hour with actual blast furnace condition at taphole;
- taking out the clay sample and keeping it in a pre-lubricated mould of
marshal load test equipment in which equipment the plunger (3) is placed
vertically above the clay sample and pressure applied slowly with the help of
a hydraulically operated piston wherein at a certain pressure clay sample
starts to extrude out from mould nozzle and forms compact cylindrical
sample (1);
- keeping the compacted sample in atmospheric controlled furnace under
reducing environment and fired at 1300-1500° with a soaking period of 2-5
hour;
- drilling a hole (25-50 mm diameter) through the centre of the compact
sample;
- filling drilled hole with new taphole clay mud in the compact sample;

- keeping filled up holed sample inside the atmospheric controlled furnace
under reducing environment and fired at 1300 - 1500°C on soaking for 2-5
hour, the sample with old and filled up holed new clay is then put up in cold
crushing strength machine wherein load is applied through plunger (8) only
on the clay sample (4) filled in the drilled hole (2);
- recording maximum load at which new clay starts to extrude out from
cylindrically shaped old clay to evaluate adhesion strength of particular
quality of taphole clay;
characterized in that evaluation of adhesion strength of the clay sample filled in
the drilled hole by the help of CCS machine wherein the plunger apply load on
the said sample and evaluating the adhesion strength at maximum load at
which new clay starts extruding out from the cylindrically shaped old clay
sample.
2. The testing devices to carry out the testing process as claimed in claim 1
comprises:-
- one oven for heating taphole clay at 60°C from one hour;
- one pre-lubricated mould for making a cylindrical sample;

- one marshal load testing equipment for making a compact cylindrical
sample;
- one atmospheric controlled furnace under reducing environment and fired
the sample at 1300° - 1500°C for 2 - 5 hours;
- one drilling machine for making a central drill hole of the sample;
- one cold crushing strength machine wherein the load is applied through a
plunger on clay sample filled in drilled hole to evaluate the maximum load at
which new clay mud starts to extrude out from cylindrically shaped old clay
mud which shows the adhesion strength of particular quality of tap hole
clay.

ABSTRACT

A TESTING PROCESS TO EVALUATE ADHESION STRENGTH
BETWEEN OLD AND NEW CLAY ADAPTABLE TO TAPHOLE OF
BLAST FURNACE
A testing process to evaluate adhesion strength between old and new clay
adaptable to taphole of Blast Furnace comprising the steps of keeping
predetermined quantity of taphole clay sample in an oven at 60 - 70°C for an
hour with actual blast furnace condition at taphole; taking out the clay sample
and keeping it in a pre-lubricated mould of marshal load test equipment in which
equipment the plunger (3) is placed vertically above the clay sample and
pressure applied slowly with the help of a hydraulically operated piston wherein
at a certain pressure clay sample starts to extrude out from mould nozzle and
forms compact cylindrical sample (1); keeping the compacted sample in
atmospheric controlled furnace under reducing environment and fired at 1300-
1500° with a soaking period of 2-5 hour; drilling a hole (25-50 mm diameter)
through the centre of the compact sample; filling drilled hole with new taphole
clay mud in the compact sample; keeping filled up holed sample inside the
atmospheric controlled furnace under reducing environment and fired at 1300 -
1500°C on soaking for 2-5 hour, the sample with old and filled up holed new clay
is then put up in cold crushing strength machine wherein load is applied through
plunger (8) only on the clay sample (4) filled in the drilled hole (2); recording
maximum load at which new clay starts to extrude out from cylindrically shaped
old clay to evaluate adhesion strength of particular quality of taphole clay.