AN IMPROVED METHOD FOR CONTROLLING BULK DENSITY OF
COAL BLEND
FIELD OF INVENTION
The present invention relates to improving the bulk density of coal blend.
More particularly, this invention concerns decreasing the moisture content of
the coal blend without compromising with the dust emission and with the
increased bulk density of the said coal blend.
BACKGROUND ART
Coking coal is converted to coke by driving off volatile matters to leave coke.
The physical properties of coking coal cause the coal to soften, swallowed
and then resolidify into hard but porous lumps when heated in the absence of
air. The coking process consists of heating coking coal to around 1000-
1100°C in the absence of oxygen to drive off the volatile compounds
(pyrplysis). This process results in a hard porous material - coke. Coke is
produced in a coke battery which is composed of many coke ovens stacked in
rows into which coal is loaded.
One of the most important factors affecting the uniformity of coke oven
operations and the quality of the coke produced is the bulk density of the coal
that is charged into the oven. Changes in that bulk density not only cause
irregular heating, which is reflected in the impaired quality of the coke; but
also cause variations in oven throughput, which affect the coke yield. The
principal cause of bulk density changes in coking coal is the variation in its
surface moisture. As the surface moisture increases up to a limit of around
8% or 9%, the coal increases in volume and its bulk density decreases.
Conversely, as this wet coal dries out, it shrinks in volume and its bulk density
increases. Between dry coal and wet coal, the bulk density may vary as much
as 15% or more. Despite of these facts, moisture in coal blend is added to
reduce the dust emission during transfer/charging and roof carbon deposition.
Reduction in moisture results in higher bulk density but at the same time dust

emission increases. Higher moisture of coal blend increases specific heat
consumption and charging hopper jamming in addition to higher thermal
shock to oven refractory
In order to increase the bulk density of coking coal up to a desired value, a
widely used procedure is to apply fuel oil/ oil emulsion to the coal. These
solutions increase the coal's bulk density. Also, to improve the bulk density of
wet coal, some coke oven installations use a preheating process. The wet
coal is heated until the moisture is driven off and this dried coal is then placed
in the oven where it forms a highly dense mass.
A more common method for increasing the bulk density of wet coal is to add a
bulk density control medium to the coal. Commonly used media include
recycled oil, fuel oil and a surfactant together, or a surfactant alone. Theses
processes are expensive in capital and operating costs.
In the prior art:-
1. U.S. Patent No. 2,378,420 discloses Regulating the Bulk
Density of Coke Oven Charges", teaches that moist coal
containing more than 1% weight moisture can be coated with
small quantities of an oil to increase the wet bulk density of the
coal. Lohr et al also teach that the wet bulk density of coal can
be adjusted by spraying the surfaces of the coal with a free
flowing liquid containing a wetting agent.
2. U.S. Patent No. 3,563,714, teaches a composition of matter
used for controlling the bulk density of coal with comprises a
combination of petroleum oil, water and a surfactant or mixture
of surfactants.
3. U.S. Patent No. 4,214,875, teaches treatment of exposed coal
piles with polymers including polyethylene in combination with
wax tars or pitch and solid fillers. The coating protects coal piles
from the physical loss of coal.

4. U.S. Patent No. 4,304,636, teaches a method for controlling the
bulk density and throughput characteristics of coking coal by
treating the coal with a surfactant and a combination of fuel oil
and alcohol or a solid lubricant and water.
5. U.S. Patent No. 4,331,445, , teaches prevention of spontaneous
combustion of coal by treatment with an aqueous solution of
polyethylene oxide of at least 2% by weight followed by drying of
the coal.
6. U.S. Patent No.4,450,046, , teaches spraying the surface of the
coal with an aqueous dispersion of a surfactant to increase the
wet bulk density.
7. P.C.T application No. WO2009039070A2 discloses methods
and compositions for controlling bulk density of coking coal.
Compositions for adjusting coal bulk density and methods of
using the compositions are provided. In an embodiment, the
present invention provides methods of utilizing the compositions
to adjust coal bulk density. The compositions can comprise one
or more components selected from a group consisting of
vegetable oils, animal fats, triglycerides, fatty acids, fatty acid
methyl esters, fatty acid ethyl esters, and glycerin. These
compositions can be derived from a biodiesel manufacturing
process or transesterification reactions involving triglycerides.
8. P.C.T application No. WO 1993014032 A1 discloses process
for increasing the bulk density of wet coal with polyacrylamide,
polyethylene oxide or mixture thereof. Methods and
compositions are provided for increasing packed bulk density of
coal, whose surface moisture varies from 5 to 15 weight percent,
to desired levels in the range of 45 to 50 1bs./cu.ft., and for
controlling and maintaining the improved bulk density. The
method involves treating the coal with dilute water solutions
(0.01 to 1.0 weight percent of solids) of water soluble, nontoxic

polymers, belonging to the classes of polyethylene oxides and
polyacrylamides, in amounts between .5 gram and 120 grams of
polymer solids per metric ton of coal.
There has been a long-felt and unfilled need for low cost processes for
increasing and controlling the bulk density of wet coal. The present invention
met this need.
SUMMARY OF THE INVENTION
It is an object of this invention to provide method which control and increase
the bulk density of coal used in making coke.
It is another object of this invention to provide processes which increase the
weight of coal and increase the thermal conductivity of the coke oven charge
by increasing the coal bulk density.
It is another object of this invention to provide processes which increase the
throughput and efficiency of a coke oven.
It is another object of this invention to provide processes which increase coke
stability by increasing the bulk density of the coal used in making coke.
It is therefore desirable to develop some methods for improving the bulk
density of coal that emit less pollution, are less hazardous to human health
and the environment, and are also, cost effective.
In an embodiment, this invention is a method of improving the bulk density of
coking coal by treating the comprising water / moisture only.
Therefore such as herein described is a method for effective and inexpensive
bulk density improvement of coal blend carried out by mixing the coal with
bulk density control media comprised of polarized / magnetized water.

It is a final object of this invention to provide processes which raise and
control the bulk density of coal in a manner which is inexpensive, effective,
and environmentally benign.
These and other objects of this invention will become readily apparent from
the following specification.
DETAILED DESCRIPTION
Moisture in coal blend is added to reduce the dust emission during
transfer/charging and roof carbon deposition. Reduction in moisture results in
higher bulk density but at the same time dust emission increases. Higher
moisture of coal blend increases specific heat consumption and charging
hopper jamming in addition to higher thermal shock to oven refractory.
Magnetic water system is used to treat the water hardness. When normal
water is passed through heavy magnetic field, the bond orientation of H-O-H
bond gets changed and because of this effect, the surface tension of water
gets reduced. This property of magnetic water system was used in the
process of moisture addition in coal blend at Coal Handling Plant (CHP-1) of
BSP. Because of the reduced surface tension of the magnetized water, its
spreadability over the coal particles increases and the problem of dust
emission could be arrested with less amount of water. Dry coal has the
highest bulk density; but as the moisture content is increased, the bulk density
drops steadily. At some moisture concentration, usually in the range of 5 to 9
percent, depending upon the granulometry, a minimum occurs; with further
increase in moisture the bulk density increases
Under this project, total four numbers of magnetic water conditioners were
installed, where water is added to Coal blend to control its moisture level.
After the introduction of the system, about 12 to 14 % reduction was observed
in the surface tension of water. Several trials were conducted and it was found
that moisture of coal blend could be reduced from 8.5 % to 7.5 % level without
any adverse affect on dust emissions. As a result, the Bulk density of the coal
charge (dry basis) increased from 738 kg/m3 to 752 kg/m3.

Under this project, with the usage of magnetized water system, primary
objective was to reduce the moisture content in coal blend and consequently
improvement in bulk density was aimed.
Purpose of the introduction of magnetic water system, was to get water with
reduced surface tension. When normal water is passed through heavy
magnetic field, the surface tension of water gets reduced. This property of
magnetic water system was used in the process of moisture addition in coal
blend at Coal Handling Plant (CHP-1) of Bhilai Steel Plant. Because of the
reduced surface tension of the magnetized water, its spreadability over the
coal particles increases and the problem of dust emission could be arrested
with less amount of water.
Therefore, our approach was to reduce the moisture level in coal without
increasing the adverse effect of dust emission. So that, after the introduction
of magnetic water system, it would be possible to reduce the moisture level in
coal and hence with reduced moisture level and with proper crushing,
possibility in the improvement of bulk density was to be explored.
After the installation of the magnetic water system, following experiments
were done:
Surface tension test
Establishing optimum level of moisture
Screen analysis test
Bulk density
Surface tension test
Surface tension measurement for both treated and untreated water was done
by two methods - direct method and indirect method.
In direct method the sample for both the treated and untreated water was
collected and tested by processor tensiometer. Results are shown in Table 1.
In indirect method, samples for both the treated and untreated water was
taken in separate beakers and using capillary, meniscus height was

measured. The difference in the height was taken as surface tension
reduction. Results are shown tin Table 2. It is obvious from the table no 1 & 2
that surface tension of the magnetized water reduces by more than 11%

Establishing optimum level of moisture
For Jhe test of wetability effect on the coal wet screen test was done. The coal
blend wetted with normal water was tested in the screen and the same coal
with wetted with magnetic water was also tested in the screen. The results are

shown in Table 3 & 4. Table 3 is showing the screen analysis of coal blend at
various moisture levels. Data are indicating that, as moisture is increasing the
(-) 1.0 mm size fraction decreases. In Table 3, with normal water at, 8.5 %
moisture level, which was the regular moisture level prior to the installation of
the magnetic water conditioner, the (-) 1 mm size fraction was at the level of
10 to 11 %. From Table 4, it is clear that with introduction of magnetic water,
(-) 1 mm fraction decreases indicating that dust emission is less with magnetic
water. It is also obvious from the Table 3 & 4 that dust emission level shall be
same if magnetic water is used in the range of 7.5 to 8 % instead of normal
water at the level of 8.5 %. Therefore, similar level of wetting of the coal could
be obtained from less moisture level, if magnetized water was being used
instead of normal water.


Bulk Density test
Bulk Density tests were done as per the ASTM, D291-86, by drop method,
variation in bulk density of the coal blend with moisture content by addition of
normal and magnetized water are presented in Table 5 & 6 respectively. With
usage of normal water the average bulk density was 800 kg/m3 (wet basis)
and 733 kg/m3 (dry basis). With the use of magnetized water the Bulk density
has increased at the level of 814 kg/m3 (wet basis) and 751 kg/m3 (dry basis).

Table 6: Coal Bulk Density Vs Coal Moisture (Magnetized water)
Numerous modifications may be made to the present invention, which still fall
within the intended scope hereof. Thus, it should be apparent that there has

been provided in accordance with the present invention an improved method
for controlling bulk density of coking coal that fully satisfies the objectives and
advantages set forth above. Although the invention has been described in
conjunction with specific embodiments thereof, it is evident that many
alternatives, modifications and variations will be apparent to those skilled in
the art. Accordingly, it is intended to embrace all such alternatives,
modifications and variations that fall within the spirit and broad scope of the
appended claims.

WE CLAIM:
1. An improved method for controlling bulk density of coal blend
comprising of:
mixing an solution of magnetic water with coal blend to control the
moisture level.
2. The method as claimed in claim 1, wherein moisture of the coal blend
is re'duced to 8.5 % to 7.5 % without any adverse effect on dust emissions.
3. The method as claimed in claim 1, wherein the bulk density of the coal
blend is increased from 738 kg/m3 to 752 kg/m3.
4. The method as claimed in claim 1, wherein the magnetization of water
causes the reduction of the surface tension of water to 12 - 14% and increase
in flowability of the coal blend.
5. The method as claimed in claim 1, wherein the said method is
configured to reduce the moisture content in coal blend and consequently
improvement in bulk density.