CLIAMS:We Claim:
1. A method for pre-heating of bustle main before blowing-in of blast furnace comprising

involving venting duct on cold blast or snort valve to suck in natural air from outside atmosphere and creating a natural draft;

subjecting the thus sucked in natural air to heating such as to increase its sensible heat required for said bustle preheating;

feeding to the bustle main for its desired preheating; and

finally exiting the air after preheating through back draft chimney.

2. A method as claimed in claim 1 comprising

blanking of the down legs from bustle main during the pre-heating process and removing the blowpipes to isolate the furnace proper;

creating said natural draft by opening the snort valve slowly for allowing the ambient air to get sucked through venting duct of snort valve into the cold blast line without using blower;

making the air sucked in through snort valve to pass through one or more of the well heated stoves to increase its sensible heat and finally feeding to the bustle main at controlled volume flow rate;

making gases after heating the bustle main to exit through the back draft chimney.

3. A method as claimed in anyone of claims 1 or 2 wherein the volume of air sucked in is controlled by adjusting the regulator of snort valve which in turn is based upon actual flow feedback from flow element fitted in cold blast line.

4. A method as claimed in anyone of claims 1 to 3 wherein when said snort valve is opened, the volume of air passing through the duct increases from 100Nm3/min to stabilize around 500Nm3/min flow rate after a few heat up cycles.

5. A method as claimed in anyone of claims 1 to 4 wherein functioning of said stoves is based upon selecting the one with higher heat content in keeping with normal operations.

6. A method as claimed in anyone of claims 1 to 4 wherein said process of bustle pre- heating through natural draft takes approx 2 days and is run in parallel to the maintenance job taking place in the furnace, thus reducing the shutdown time.

7. A system for carrying out the method for pre-heating of bustle main before blowing-in of blast furnace as claimed in anyone of claims 1 to 6 comprising

venting duct of snort valve adapted to suck in natural air from outside atmosphere and creating a natural draft;

said venting duct operatively connected to one or more of the well heated stoves for subjecting the thus sucked in natural air to heating such as to increase its sensible heat required for said bustle preheating ;

operative connection of said thus heated natural air to bustle main for its desired preheating; and

back draft chimney providing for finally exiting the air after preheating of said bustle.

Dated this the 17th day of January, 2014
Anjan Sen
Of Anjan Sen & Associates
(Applicants Agent)
,TagSPECI:FIELD OF THE INVENTION

The present invention relates to a method for bustle heating by natural draft before blowing in of the Blast Furnace and a system thereof. More particularly, the present invention is directed to a method for bustle pipe heating before blowing in of blast furnace wherein to create the natural draft, the blower is not used and snort valve is slowly opened, allowing the ambient air to get sucked into the cold blast line at controlled flow rate and the air thus sucked in through snort valve is made to pass through one of the well heated stoves to increase its sensible heat and finally fed to the bustle main to pre-heat up to a temperature of at least 600ºC so that it doesn’t take away any sensible heat from the blast air. Moreover, jobs like furnace refractory, shell repairs shall be continued in parallel to the bustle heating as the bustle pipe is disconnected from the furnace proper. The gases after heating the bustle main is made to exit through the back draft chimney. This reduces the shutdown time as compared to bustle heating through conventional blower route favouring cost effective and energy efficient operation with improved BF productivity.

BACKGROUND OF THE INVENTION

It is well known that the bustle main pipe circumscribes the blast furnace at the tuyere level, distributing the hot blast coming from the stoves to the blast furnace via tuyeres. After long duration shutdown of the furnace, of the order of 5-6 days, the bustle main loses its heat and temperature falls down to ambient temperature of or around 50ºC. Therefore, at the time of the blow in of the furnace when hot blast is passed through the cold bustle pipe, a major portion of the sensible heat of the blast volume is absorbed by the cold bustle refractory. This leads to a drop in the heating value of the hot blast air resulting in lower heat transfer into the furnace. This makes the ramp up process slow as the ignition of coke in front of the tuyeres slows down. The inadequate heat pumped into the furnace results in more coke to be charged to match the heat requirement to establish smelting. Therefore before blowing-in of the furnace the bustle pipe must be pre heated up to a temperature of at least 600ºC so that it doesn’t take away any sensible heat from the blast air or else it may result in prolonging the ramping-up of the furnace.

The bustle heating activity takes around 1 day and is the last activity in a series of all maintenance jobs in the furnace. Normally the process of bustle heating is carried out with the blast air coming from the blowers. This consumes a lot of energy and incurs huge cost as the air required to heat the bustle pipe is quite low in volume as compared to the blower capacity. Also the use of blower comes under the critical activity path which is not desirable. Under such circumstances the maintenance work in and around boiler & blower is restricted. Bustle heating by blower requires blanking of the blowpipes from the furnace and then reverting it back at the time of the blow-in which prolongs the shutdown time. This process of blanking and reverting back requires putting down of blowpipes which can consume further 20 – 24 hrs. Also because of blanking of the blowpipes and high pressure from the blower side there is no possibility of any job to be carried out in and around tuyere platform.

There has been therefore a need in the art of Blast furnace operation to provide for a system and method for energy efficient and cost effective bustle pipe pre-heating before blowing in of the Blast Furnace avoiding use of costly air blower and simply by introduction of ambient air by natural draft made to pass through one of the well heated stoves to increase its sensible heat so that the bustle heating is carried out at less time without disturbing the ongoing maintenance work inside blast furnace near the tuyeres, without prolonging the shutdown time and no sensible heat from the blast air is taken away during blowing in favouring faster ramping-up of the furnace.

OBJECTS OF THE INVENTION

The basic object of the present invention is directed to provide a method and system for pre-heating of bustle main before blowing in of the blast furnace in a cost effective and energy efficient manner at less time favouring reduced shutdown time of the blast furnace.

A further object of the present invention is directed to provide a method for pre-heating of bustle main before blowing in of the blast furnace by using natural draft to allow controlled flow of heated atmospheric air through the bustle pipe without involving expensive blower operation.

A still further object of the present invention is directed to provide a method for pre-heating of bustle main before blowing in of the blast furnace wherein no substantial sensible heat of the blast volume is absorbed by the cold bustle refractory during blowing in favouring faster ramping–up of the furnace.

A still further object of the present invention is directed to provide a method for pre-heating of bustle main before blowing in of the blast furnace wherein bustle heating is carried out simply by natural draft by taking natural air through venting duct of snort valve as opposed to conventional use of blast air from blower.

A still further object of the present invention is directed to provide a method for pre-heating of bustle main before blowing in of the blast furnace wherein maintenance jobs related to tuyere or in that area can be continued without any hindrance due to blanking of the blowpipes from the furnace for pre-heating of bustle and then reverting it back at the time of the blow-in, favouring faster maintenance reducing the shutdown time of the blast furnace.

A still further object of the present invention is directed to provide a method for pre-heating of bustle main before blowing in of the blast furnace wherein volume/flow rate of air sucked in through snort valve is selectively controlled for desired controlled rate of heating of bustle main.

A still further object of the present invention is directed to provide a method for pre-heating of bustle main before blowing in of the blast furnace wherein gases after heating the bustle main is made to exit through the back draft chimney.

SUMMARY OF THE INVENTION

The basic aspect of the present invention is thus directed to a method for pre-heating of bustle main before blowing-in of blast furnace comprising

involving venting duct of snort valve to suck in natural air from outside atmosphere and creating a natural draft;

subjecting the thus sucked in natural air to heating such as to increase its sensible heat required for said bustle preheating;

feeding to the bustle main for its desired preheating; and
finally exiting the air after preheating through back draft chimney.
A further aspect of the present invention is directed to said method comprising

blanking of the down legs from bustle main during the pre-heating process and removing the blowpipes to isolate the furnace proper;

creating said natural draft by opening the snort valve slowly for allowing the ambient air to get sucked through venting duct of snort valve into the cold blast line without using blower;

making the air sucked in through snort valve to pass through one or more of the well heated stoves to increase its sensible heat and finally feeding to the bustle main at controlled volume flow rate;

making gases after heating the bustle main to exit through the back draft chimney.

A still further aspect of the present invention is directed to said method wherein the volume of air sucked in is controlled by adjusting the regulator of snort valve which in turn is based upon actual flow feedback from flow element fitted in cold blast line.

A still further aspect of the present invention is directed said method wherein when said snort valve is opened, the volume of air passing through the duct increases from 100Nm3/min to stabilize around 500Nm3/min flow rate after a few heat up cycles.

Yet another aspect of the present invention is directed to said method wherein functioning of said stoves is based upon selecting the one with higher heat content in keeping with normal operations.

A further aspect of the present invention is directed to said method wherein said process of bustle pre- heating through natural draft takes approx 2 days and is run in parallel to the maintenance job taking place in the furnace, thus reducing the shutdown time.

A still further aspect of the present invention is directed to a system for carrying out the method for pre-heating of bustle main before blowing-in of blast furnace as described above comprising
venting duct of snort valve adapted to suck in natural air from outside atmosphere and creating a natural draft;

said venting duct operatively connected to one or more of the well heated stoves for subjecting the thus sucked in natural air to heating such as to increase its sensible heat required for said bustle preheating;

operative connection of said thus heated natural air to bustle main for its desired preheating; and

back draft chimney providing for finally exiting the air after preheating of said bustle.

The objects and advantages of the present invention are described hereunder in greater details with reference to the following accompanying non limiting illustrative drawings.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

Figure 1: shows schematically the existing system to implement the method for pre-heating of bustle main according to the present invention involving the flow of the natural air sucked in by snort valve from atmosphere, made to pass through one of the heating stoves, and its path is shown by the dotted lines.

Figure 2 (a): shows the general setup of the bustle main, down legs, blow pipe and the tuyeres for implementing the method for pre-heating of bustle main according to the present invention.

Figure 2 (b): shows the procedure followed according to the present invention for preheating of bustle main in which blanking is done at the down legs and blowpipe is removed to isolate the furnace proper.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING FIGURES

The present invention is directed to provide a method and system for pre-heating of bustle main before blowing in of the blast furnace in a cost effective and energy efficient manner by sucking in heated atmospheric air using natural draft, avoiding use of costly air blast with higher energy content from blower, consuming less time for maintenance, favouring reduced shutdown time of the blast furnace.

Accompanying Figure 1 shows Bustle heating by natural draft which is done by taking natural air(1) through venting duct(not shown) of snort valve(2) as opposed to use of blower, which takes place in general case. The use of blower comes at a cost and it also hinders with the critical activity path during maintenance. To create the natural draft, the blower is not used and snort valve(2) is slowly opened, allowing the ambient air(1) to get sucked into the cold blast line(3). The volume of air sucked in can be controlled by adjusting the regulator(not shown) of snort valve(2) which in turn is based upon actual flow feedback from flow element fitted in cold blast line. As the snort valve is opened, the volume of air passing through the duct increases from 100 Nm3/min to stabilize around 500 Nm3/min flow rate after a few heat up cycles. The air sucked in through snort valve is made to pass through one of the well heated stoves(S1 ,S2 or S3) to increase its sensible heat and finally fed through hot blast line (4) to the bustle main(5). The functioning of the stoves(S1, S2, S3) here is based upon selecting the one with higher heat content just like in normal operations. All the down legs(12) from the bustle main(5) remains blanked(9) during this process and therefore any maintenance jobs related to tuyere(7) or in that area can be continued without any hindrance. Moreover, jobs like furnace refractory, shell repairs shall be continued in parallel to the bustle heating as the bustle pipe(5) is disconnected from the blast furnace proper(17). The gases after heating the bustle main(5) is made to exit through the back draft chimney(11). This process of bustle heating through natural draft takes approx 2 days and is run in parallel to the maintenance job taking place in the furnace(17). Thus it reduces the shutdown time as compared to bustle heating through conventional blower route.

Accompanying Figure 1 shows the flow of the natural air(1) sucked in by snort valve(2) from atmosphere and its path(3) is shown by the dotted lines. The natural air is passed through any one of the heated stove’s(S1, S2 or S3) cold and hot blast valve and then to the bustle main(5). The heated natural air is made to exit through the back draft chimney(11).

The venting duct of the snort valve(2) or any other vent on cold blast line is used to suck in natural air from the outside atmosphere and finally made to exit through back draft chimney valve(10) after heating the bustle main(5). It saves huge energy and cost of running a blower for a small quantity of air required for this purpose. This process can run parallel to the other activities being performed in the furnace. Its time saving to the extent of 2 days as compared to conventional method and avoids double work of blanking and de-blanking the furnace.

Accompanying Figure 2 (a) shows the general setup of the bustle main(5), down legs(12), blow pipe(14), peep hole(13), and the tuyeres(15). Figure 2 (b) shows the procedure followed here in which blanking is done at the flanges of down legs(16) and blowpipe is removed to isolate the furnace proper(17).

It is thus possible by way of the present invention to provide a method for pre-heating of bustle main by natural draft before blowing in of the blast furnace in a cost effective and energy efficient manner using the existing facilities by slowly sucking in atmospheric air through the snort valve, heating the air by passing through any stove and enter into the bustle main at controlled flow rate to heating to a desired temperature, without the use of blower such that the maintenance work or refractory repair/relining can proceed simultaneously during such preheating of bustle main thereby reducing the shutdown period of the blast furnace.

We Claim:
1. A method for pre-heating of bustle main before blowing-in of blast furnace comprising

involving venting duct on cold blast or snort valve to suck in natural air from outside atmosphere and creating a natural draft;

subjecting the thus sucked in natural air to heating such as to increase its sensible heat required for said bustle preheating;

feeding to the bustle main for its desired preheating; and

finally exiting the air after preheating through back draft chimney.

2. A method as claimed in claim 1 comprising

blanking of the down legs from bustle main during the pre-heating process and removing the blowpipes to isolate the furnace proper;

creating said natural draft by opening the snort valve slowly for allowing the ambient air to get sucked through venting duct of snort valve into the cold blast line without using blower;

making the air sucked in through snort valve to pass through one or more of the well heated stoves to increase its sensible heat and finally feeding to the bustle main at controlled volume flow rate;

making gases after heating the bustle main to exit through the back draft chimney.

3. A method as claimed in anyone of claims 1 or 2 wherein the volume of air sucked in is controlled by adjusting the regulator of snort valve which in turn is based upon actual flow feedback from flow element fitted in cold blast line.

4. A method as claimed in anyone of claims 1 to 3 wherein when said snort valve is opened, the volume of air passing through the duct increases from 100Nm3/min to stabilize around 500Nm3/min flow rate after a few heat up cycles.

5. A method as claimed in anyone of claims 1 to 4 wherein functioning of said stoves is based upon selecting the one with higher heat content in keeping with normal operations.

6. A method as claimed in anyone of claims 1 to 4 wherein said process of bustle pre- heating through natural draft takes approx 2 days and is run in parallel to the maintenance job taking place in the furnace, thus reducing the shutdown time.

7. A system for carrying out the method for pre-heating of bustle main before blowing-in of blast furnace as claimed in anyone of claims 1 to 6 comprising

venting duct of snort valve adapted to suck in natural air from outside atmosphere and creating a natural draft;

said venting duct operatively connected to one or more of the well heated stoves for subjecting the thus sucked in natural air to heating such as to increase its sensible heat required for said bustle preheating ;

operative connection of said thus heated natural air to bustle main for its desired preheating; and

back draft chimney providing for finally exiting the air after preheating of said bustle.

Dated this the 17th day of January, 2014
Anjan Sen
Of Anjan Sen & Associates
(Applicants Agent)

ABSTRACT

TITLE: A METHOD FOR PRE-HEATING OF BUSTLE MAIN BEFORE BLOWING-IN OF BLAST FURNACE AND A SYSTEM THEREOF.

The present invention relates to a method for bustle heating by natural draft before blowing in of the Blast Furnace and a system thereof. In the present method for pre-heating of bustle main before blowing in without using blower, to create the natural draft, snort valve is slowly opened, allowing the ambient air to get sucked into the cold blast line at controlled flow rate and the air thus sucked in through snort valve is made to pass through one of the well heated stoves to increase its sensible heat and finally fed to the bustle main to pre-heat up to desired temperature. The gases after heating the bustle main is made to exit through the back draft chimney. Moreover, jobs like furnace refractory, shell repairs can be continued in parallel to the bustle heating as the bustle pipe is disconnected from the furnace proper. This reduces the shutdown time favouring cost effective and energy efficient operation with improved BF productivity.
(Figure 1)