FIELD OF INVENTION
The present invention relates to a method of melting of glass wherein petroleum coke with
pressurized air is injected to the furnace through single screw pump coupled to each port
attached to the burners of the furnace.
PRIOR ART & BACKGROUND
In a conventional arrangement, furnace oil & LNG used to be the fuel of choice in the various
types of furnace systems including glass furnace as well as other heating units in various
industries. High costs of fuels, suitable for such high temperature furnaces, imposed a limitation
and thus an alternate solution in the form of a comparatively less expensive fuel was desired.
Furnace oil was widely used as a furnace fuel in conventional systems. The fuel burning
technology consisted of fuel pump, pipelines, furnace oil heating skid, metering system &
complete programmable logic controller system. The burner usually was the mechanical device
that combines fuel with desired amounts of air before delivering the homogenized mixture to
the point of ignition in a combustion chamber following which the fuel enters into the furnace
in an atomized form. The furnace oil was preheated to desired temperature in order to achieve
effective atomization & fuel efficiency.
Petroleum coke has been earlier used in furnace systems for various purposes, certain methods
for which are discussed herein suggesting the use of petroleum coke in melting of glass in glass
furnaces.
US 3,969,068 teaches a method and apparatus for direct coal firing of glasstank furnaces wherein
pulverizedcoal entrained in an air stream is impelled through a nozzleinto the furnace and combusted in
the atmosphere directly above the melt in a glassfurnace, to form a luminous flame, the direct coal firing
preferably being used in conjunction with supplementary conventional heat sources.
Shown herebelow isa schematic illustration of the coalfiring apparatusfor glassfurnaces in accordanceto
the US3,969,068. US 6748883 teaches a control system for controlling the storing, feeding and burning of a
pulverized fuel in a glass melting furnace, wherein a series of burners are arranged one in front
of the other to carry out combustion and non-combustion cycles during a glass melting process.
Pulverized fuel feeding systems are provided, which are filled up and emptied out with the
pulverized material for providing a constant flow of the pulverized fuel to each of the burners
during the glass melting process. The control system including control means for monitoring
and controlling the filled up and discharge out of said pulverized fuel feeding system based on
the measurement and monitoring of the amount of pulverized fuel that is being stored and fed
by the pulverized fuel feeding system. Control means are provided for monitoring at least one
operating variable involved on the glass melting furnace, the control means detecting a series
of different variable during the glass melting process and means for controlling the alternation
of the combustion and non-combustion cycles to each burner, based on the monitoring and
feeding of the pulverized fuel to the burners and in base to the operating variables of the glass
melting process.
Shown below is a schematic view of the system for feeding and burning a pulverized fuel in
accordance with the invention as taught in US6, 748, 883 US 6, 748, 883 teaches that for operating the glass melting furnace, the fuel is fed to the
burners and, the combustion air supplied is controlled by measuring the airflow generated at
the exit of the combustion fan and top of the structure, the quantity of oxygen and combustible
material present to ensure the statistics of the combustion air fed required for complete
combustion of the fuel being supplied.
US 6,789,396 teaches a method and system for feeding and burning pulverized fuel, such as
petroleum coke, in a glass melting furnace, which includes a glass melting and a plurality of
burners associated with a pair of sealed regenerative chambers disposed side-by-side which act
as heat exchangers, the burners are arranged in a series of ports that are associated with the
glass melting region of the furnace. The system includes means for supplying the pulverized fuel
by each one of the burners for melting glass raw materials. The emissions of flue gases
produced by the combustion process of the fuel in the furnace are controlled in order to
maintain clean the flue gases and for reducing the emission of impurities from the fuel such as
SOx, NOx and particulates. The regenerative chambers are manufactured with selected
refractories such as, magnesium, zircon-silica-alumina or magnesia and Zirconium-silicate, for counteracting the erosive and corrosive effects produced by the combustion process of the fuel
in the glass melting chamber. A burner is also provided for feeding the petroleum coke, the
burner including means to simultaneously mix a primary air and pulverized fuel-air mixture for
the burning of the pulverized fuel.
Illustrated below is a block diagram of an embodiment of the system for feeding and burning
the petroleum coke in accordance to the invention as taught in US6,789, 396 U,S 7,143,610 is a continuation-in-part of application US 10/601,167 which is granted as US
6,789,396 and teaches a method and system feed and burn pulverized fuel, such as petroleum
coke, in a glass melting furnace having burners associated with sealed regenerative chambers
which act as heat exchangers. The system supplies the pulverized fuel for melting glass raw
materials. The emissions of flue gases produced by the combustion process of the fuel in the
furnace are controlled in order to maintain clean the flue gases and for reducing the emission
of impurities from the fuel such as sax, NOx, and particulates. The regenerative chambers are
manufactured with selected refractories such as magnesium, zircon-silica-alumina, or magnesia
and zirconium-silicate, for counteracting the erosive and corrosive effects produced by the
combustion process of the fuel in the glass melting chamber. A burner feeds the petroleum coke and simultaneously mixes a primary air and pulverized fuel-air mixture for the burning of
the pulverized fuel.
Illustrated below are various sections of a burner suitable to be used in a glass furnace utilizing
petroleum coke as the fuel. IN 227837 teaches a method and system for feeding and burning pulverized fuel, such as
petroleum coke, in a glass melting furnace, which includes a glass melting and a plurality of
burners associated with a pair of sealed regenerative chambers disposed side-by-side which act
as heat exchangers, the burners are arranged in a series of ports that are associated with the
glass melting region of the furnace. The system includes means for supplying the pulverized fuel
to set of burners for melting glass raw materials.
The emissions of flue gases produced by the combustion process of the fuel in the furnace are
effectively controlled in order to maintain clean the flue gases and for reducing the emission of impurities from the fuel such as SOx, NOx and particulates. Combustion process and operating
parameters have been improved to provide complete combustion of petroleum coke. Complete
handling, conveying and combustion system have been modified to support petroleum coke
operation.
It is observed that the existing furnace systems already being used for melting glass uses gear
pumps in the fuel oil circuit. One of the disadvantages of using such gear pumps is the poor
handling of the binary fuel mixture of solid and gas and thus the economics of the furnace
management resulting into poor yields of the desired material. The earlier systems were more
adapted for using the liquidized fuel systems and thus faced several problems in handling of
solid fuels effectively. The Applicant has attempted to come out with an improved solution
towards the melting of glass in a glass furnace using petroleum coke instead of using
conventional furnace fuels using improved burners. It is further observed that many other
furnace systems have used gravimetric coke feeding equipment in order to feed the fuel to
burners, leading to complication in the fuel management.
By way of the present invention, the Applicant has also succeeded in saving a considerable
amount of energy cost which constitutes around 40% of total product cost. Hence the present
invention is a cost effective way of reducing the energy cost of melting glass and effective
utilization of petroleum coke as an alternate fuel in glass melting furnace. The Applicant has
utilized petroleum coke as the furnace fuel in the glass melting furnace system in the present
invention and has endeavored to develop a system for pulverizing, handling and conveying and
using the desired furnace fuel within glass furnace.
Such improved system is discussed in the description of the instant specification together with
few working examples in order to illustrate the said instant experimental set-up.
OBJECTIVE OF THE PRESENT INVENTION
The objective of the present invention is to provide a method of melting of glass wherein
pulverized petroleum coke with pressurized air is injected to the furnace through single screw pump coupled to each port attached to the burners of the furnace for enhanced energy
management and cost economy.
FIGURES:
Detailed schematic diagram of the furnace system illustrated in Fig 1
DESCRIPTIONOFTHE PRESENTINVENTION
A figurative comparison between outcome of usage of fuel oil, which has been commonly used
in such types of glass furnaces for the melting of glass and petroleum coke is given below to
further illustrate the usefulness of petroleum coke, specifically in glass furnaces, such
comparison being tabulated as below:
1. Petroleum Coke Vs. Fuel Oil Properties:
Details Fuel Oil Petroleum Coke
Calorific Value Kcal/Kg ;Net Calorific 9600 7700
Value
Ash Content % 0.1% Max 0.5%
Sulphur Content % 3.5% to 4% 0.5 %to 6%
2. Petroleum Coke Vs. Fuel Oil Cost Comparison for 360 TPD Furnace~
(Metric Ton per day i.e. 360 Ton of glass is produced per day)
Particulars UO~I Comparison
Fmnace Pull per day 11T 360
Specific Melting Energy - WIO Elec Boost Kcal.1kg 1000
Total Fmnace Melting Energy -'"Via Boost Kcal/day 360000000
GURRE~"T -FIJRNACE OIL ,HSD , LNG
NCV - Fmnace Oil kc.a1tkg 9600
FO landed Cost Rs./Kg 42
Fa Requirement Kg/day 37500
Effective Cost offumace Oil Rs. 1575000
PROPOSED;.. PETROLEUM: COKE ""
NCV - Petroleum coke Kc.a1 7700
PET Coke landed cost Rs.IKg 13.5
PET COKE Requirement Kg/day 48750
Effective Cost of Pet coke Rs 658125 The present invention relates to a method of melting of glass wherein pulverized petroleum
coke with pressurized air is injected to the furnace through single screw pump coupled to each
-,
port attached to the burners of the furnace for enhanced energy management and cost
economy.
The present invention further relates to the use of raw petroleum coke being crushed &
pulverized to 160-200 microns to achieve smooth firing & flame geometry. Flame geometry,
temperature & other characteristics are maintained by effective instrumentation & automation
of the feeding & mixing system. Glass furnace combustion system is modified to burn
pulverized petroleum coke in the furnace. The air fuel mixture, fuel being petroleum coke is
subjected to compressed feeding rate and is synchronized on the basis of flame temperature &
O2 levels. Service silos, pneumatic control valves, screw feeders, pulverized fuel feeding pumps,
dual phase mixers have been installed to supply proportionate amount of air fuel mixture into
the furnace. Specific grade of petroleum coke is used in the manufacturing of glass after
necessary processing, in order to optimize the sulphur levels, which is basically an impurity.
An important feature of the present invention is the burner used for the treating the petroleum
coke fuel in the binary phase in order to achieve desired grade of glass. The desired flame
geometry is measured by such burners and feed pressure. The feed pressure is another
important factor in terms of furnace operation and is preferably in a range of 2 to 6 bars. Such
feed pressure is required to inject the petroleum coke into the furnace. An indefinite value of
the pressure will cause irregular injection rate of the petroleum coke which will ultimately
effect the burning of total system. The feed rate and quantity applied in the present invention is
also another critical and contributing factor for the overall operation. Emissivity of petroleum
coke is on higher side resulting into the flame being considerably much hotter and brighter.
The furnace system of the present invention typically consists of pneumatic valves, screw pump
and screw conveyors, overall action of which is controlled by an automated system; constant feed is maintained to pump to send pulverized fuel, with continuous and
uniform material flow controlling the flame all along;
System has high accuracy feed rate control mechanism which helps in maintaining the
requirements of the furnace temperature control accuracy;
A significant and unique feature of the instant invention is the introduction of the screw
conveyor and solid handling screw pump whereas conventionally a gear pump is used in the
fuel oil circuit. Since the transporting media is completely different, the system of the present
invention is designed to transport binary mixture of solid-gas fuel material. The pump is used
for measuring and fluidization system. In the present invention, fuel burners are connected
directly to the mixing chamber through screw pump. These screw pumps can be controlled
individually or by port control, therefore fuel feed rate through individual burner / port basis
can be measured and controlled. The fuel is injected into the furnace through multiple burners.
These burners are mounted on the left and right hand port of the furnace. These individual
ports are connected to the main header of the flue line. This main header is connected to the
mixing chamber and screw pump. The fuel direction is controlled automatically through a
conventional control system, commonly termed as SCADAsystem (Supervisory Control and
Data Acquisition system).
The advantage of using single screw conveyor system is that such screw conveyor system
controls the fuel feed rate on overall supply to port so the total quantity of fuel injected to the
furnace can be measured and controlled. In stark contrast, fuel quantity feed through
individual burner is difficult and cumbersome for determination. Utilization of such a screw
conveyor system results in better control over the entire system, resulting into a uncomplicated
and versatile operational atmosphere which in turn contributes to better yield, cost
effectiveness of the entire furnace system as well as fuel management as well as significantly
low and controlled pollution. The single screw conveyor per port system also contributes to the enhancement to uncluttered
workability aptly aided by an automated system which taken as a whole enhances the further
efficiency of the system and further establishes overall control.
Another significant feature of the present invention is the particle size of the solid petroleum
coke which is pulverized to a range of 160 micron - 200 micron, enabling it to float through air
and result in effective combustion, also forming a homogenized gaseous mixture thereby
increasing the burning efficiency.
An embodiment of the present invention is a method of melting glass in a glass furnace, said
method comprising the steps of:
a) pulverizing the petroleum coke to size in the range of 160 micron to 200 micron;
b) pulverized petroleum coke of step (a) is transported to the mixing chamber by
screw pump along with compressed air under pressure applied in a range of 2-6 bar;
c) petroleum coke of step (b) is then fed to a multiplicity of burners by a single screw
pump, which is coupled with each port attached to the burners, at a pre-determined
feed rate, into the furnace in order to achieve desired quality of glass.
Another embodiment of the present invention is the method, wherein the feed rate of the
pump is in a range of 2 - 6 metric tonnes / hour.
Yet another embodiment of the present invention is the method, wherein the fuel burners are
connected directly to the mixing chamber through screw pump.
Another embodiment of the present invention is the method wherein, optionally a multiplicity
of screw pumps may be deployed depending on the size of the furnace.
In order to illustrate the proposed invention, schematic drawing / figures of various
arrangements of furnace is provided here below, to be put in place for petroleum coke usage. BASIC EQUIPMENT SETUP
Glass furnace of approximate consumption of 1.3 Kg of petroleum coke and having melting
capacity of 260 TPD (Ton per Day) and consumes around 25 MT of furnace oill day. Petroleum
coke is pulverized using a 200 mesh, wherein the industrial grade petroleum coke is pulverized
to 160-200 micron such pulverized material being stored in an overhead Silo ref 1 of Fig 1 & 2
of capacity of 60 MT.
The petroleum coke is lifted to Silo platform by electro-mechanical hoist, material is then
screened to remove foreign material and coarse grade. This is done through specially designed
rotary screens ref 20 of Fig 1 & 2. Screened material is then fed through screw conveyors ref 3
of Fig 1 & 2 and rotary airlock to dense phasel lean phase systems to transfer it storage silos.
A conventional screw feeder I rotary airlock is placed beneath the Silo, this system transfers
material from Silo to the conveying media at a controlled rate (the rate varies from 2000 -6000
kg I hr r. Feeding the pulverized material varies depend upon the temperature requirement and
is crucial for the operation, and thereby protecting the conveying media from abrupt change in
flow rate. Feed rate is controlled through variable frequency drives.
Conventional belt conveyors are unable to transmit particle size of 200 mesh material, hence in
order to do so pipe diameter of 300 mm varying with feed rate of 150 mm-300 mm is chosen
for the instant experimental working setup. The pipe is connected to the top of screw pump ref
2 of Fig 1 & 2.
The screw pump is mounted on the floor of furnace by suitable base plate. The base plate is
mounted on the floor beam of furnace floor. The screw pump controls the feed rate of the
pulverized fuel.
The rate of volume transfer in the screw pump is proportional to the rotation rate of the shaft.
In industrial control applications, such device is conventionally used as a variable rate feeder by varying the rotation rate of the shaft to deliver a measured rate or quantity of material into a
process. The capacity of the screw pump is 2.0 MT/ hr to 6.0 MT/ hr land a motor rating of 7.5
KW/15 KW is coupled with the screw pump. RPM of the motor determines the feed rate of the
screw. One compressed air line, ref 5 ( green line) of Fig 1 & 2 is fixed to the screw, at
discharge end. The exit chute of the screw pump is connected with the mixing chamber, ref 4 of
Fig 1 & 2. One compressed air line is attached to the mixing chamber. It mixes air with
pulverized coke and form solid- gas form. The working air pressure is in a range of 2 - 6 bars.
The binary mixture of solid & gas mixture is transmitted through 50-65 NB pipe line & return
line is taken from the main line with a shut-off valve, ref 7 of Fig 1& 2. The main line is divided
into two parts and enters into the furnace through two ports. Shut off valves are fixed to the
individual branches of pipelines and also to the main header. The branch pipelines are
connected with the diamond burner, ref 41 of Fig 1 & 2 which has individual three burners. The
actual burning process takes place here. The positions of the valves are shown in the
accompanying figures in the description of the instant invention.
WORKING EXAMPLE
Based on the equipment setup as illustrated in the above paragraphs of the description taken
together with the drawings / figures, fuel material is charged into the system comprising of the
equipment set-up.
Experiment No.1
Utility pipe line was charged with compressed air and Screw feeder and Vibro feeder were
started and following observations were made:
- Air was escaping through leakages & Flange joints etc.
- Vibro feeder was not able to handle particles size of 200 mesh.
- Suction pipe was chocking frequently. Compressed air was blowing Pet Coke in the backward direction resulting very poor rate
of transmission.
- Mainly air was entering into the furnace. The quantity of PETCoke reaching burner is of
low. The flow was intermittent and continued for 15 minute. The color of flame was
white & flame can be observed from batch charger area.
Rectifications / Improvements carried out:
- Vibro feeder was taken out of the circuit and pipe was directly connected to the silo.
Also a flapper at the inlet of the pipe was fixed to prevent back pressure of
compressed air.
- All the joints were checked and gasket was fixed in the connection of pipe and screw
feeder inlet chute to prevent leakages.
- Level sensor was installed
Experiment No.2:
The entire experimental set-up as in Experiment No. 1 was re-started and the following
observations were made:
- Petroleum coke was getting chocked in the delivery pipe line.
- Screw feeder run at optimum speed of 635 rpm. It was frequently tripping at high
speed.
- Air pressure was reduced at the mixing chamber to optimize mixing and flow ability
Rectifications / Improvements carried out:
- Delivery end pipe line was dismantled; sharp corner joints & unnecessary bends were
removed.
- Long radius bend was installed.
- Upper limit of motor speed fixed.
- NRV (Non Return Valve: this is a mechanical valve which allows fluid to move through only
one direction) arrangement provided to avoid back flow of the fluidized mixture.
Experiment No.3:
The entire experimental set-up was restarted and the following observations were made:
- Pet Coke carrying to the furnace has improved but not upto the desired level. The entire system was running smoothly without much chocking
- The flame was bright and was visible through peep holes.
Rectifications / Improvements carried out:
- Elevation of screw feeder was lifted to Port Gallery level to get adequate pressure & slope
at the delivery point.
- Also the pipeline was connected with other two burners.
- Reversal system / automation done.
- Fine sieve (600 mesh) installed at pet choke location to avoid entry of foreign material.
- Air connection provided to Mixing bed in such a way to generate venture effect.
- Compressed air nozzles fitted at various locations to avoid clogging of PETcoke.
- VFD installed for screw to vary feed rate as per furnace temperature.
- Burners adjusted to provide adequate length of the flame.
Experiment No.4:
The system was started once again and it shows substantial improvement.
- Flowability of PETCoke & Fluidized mixture improved upto desired level.
- Flame geometry maintained to meet furnace operating parameters.
- Air fuel mixture maintained to get complete combustion.
- All installed burners running successfully with reversal mechanism automation.
- Desired Glass maintained & no issues with glass quality & combustion parameters.
- System is running smoothly from last 10 days in auto mode.
- Flame characteristics are better than oil flame. i.e. Bright flame.
By way of the instant invention, the Applicant have succeeded in saving a considerable
amount of energy cost which constitutes around 40% of total cost of the glass plant. Hence
the instant invention is a cost effective way of reducing the energy cost of melting and
utilization of petroleum coke as an alternate fuel in glass melting furnace.
WE CLAIM:
1. A method of melting glass in a glass furnace, said method comprising the steps of:
a} pulverizing the petroleum coke to size in the range of 160 micron to 200 micron;
b} pulverized petroleum coke of step (a) is transported to the mixing chamber by
screw pump along with compressed air under pressure applied in a range of 2-6 bar;
c} petroleum coke of step (b) is then fed to a multiplicity of burners by a single screw
pump, which is coupled with each port attached to the burners, at a pre-determined
feed rate, into the furnace in order to achieve desired quality of glass.
2. A method as claimed in claim 1, wherein the feed rate of the pump is in a range of 2 - 6
metric tonnes / hour.
3. A method as claimed in claim 1, wherein the fuel burners are connected directly to the
mixing chamber through screw pump.
4. A method as claimed in claim 1, wherein optionally a multiplicity of screw pumps may
be deployed depending on the size of the furnace.