Claims:We Claim:

1. A system for online de-clogging of pre-scrubber in a gas cleaning plant comprising :

a pre-scrubber tower including a conical gas entry pathway and spray nozzles centrally arranged at different levels inside the pre-scrubber tower for pre-cleaning of dirt from the gas ;

a conical sump at lower end of the pre-scrubber for collecting the particulate matters in slurry form generated during pre-cleaning of the dirt from the gas;

pipelines for conveying the pre-cleaned gas, generated by the pre-scrubber; to the AG scrubber for its further cleaning;

water spray ring headers including a top spray ring header outside of said pre-scrubber tower towards the top end with adequate number of flat-jet nozzles that covers the full circumferential area inside the conical gas entry region of the pre-scrubber tower, adapted for de-clogging and uprooting the settled particulate matters and a bottom spray ring header provided outside of said pre-scrubber tower, focusing the conical sump area and with adequate number of flat-jet spray nozzles, adapted for de-clogging and uprooting the settled particulate matters inside the conical sump and at slurry outlet pipe of the Pre-scrubber;

pump and motor means for delivering pre-set capacity of water through said water jet spray nozzles with cooperative control valves at said conical gas entry pathway internal face at the top portion of the pre-scrubber tower and said conical sump internal face towards the lower end of the pre-scrubber tower;

said selectively disposed jet nozzles adapted for de-clogging and uprooting settled particulate matters operable in tandem with operation of gas cleaning pre-scrubber for desired online de-clogging of pre-scrubber in a gas cleaning plant.

2. The system as claimed in claim 1 comprising :

said Pump & Motor to deliver pressurised volume of water as per pre-set capacity to major locations including (i) Top spray ring-header at 24m to 26m preferably +25m level, (ii) Bottom spray ring-header at..14m to 16m..preferably +15m level and (iii) Jet Nozzle, installed below the conical sump at the slurry outlet pipe;
Said Water spray ring-headers comprises two ring-headers, located outside the Pre-scrubber, at two different levels, focusing the two most identified critical locations of possible build-ups/accumulations of particulate matters inside the Pre-scrubber; 8 to 12 preferably about 10 number of flat-jet nozzles each in the spray ring-header installed to cover the full circumferential area inside the Pre-scrubber;
the spray face of each nozzle is directed towards the nearest side wall with the top spray ring-header located approximately at 25m level, focusing the top conical portion of the Pre-scrubber and the bottom spray ring-header located at approximately at 15 m level, focusing the slant surfaces of the conical sump of the Pre-scrubber;

said Control Valves: provided based on the operative pipeline size, working pressure head and generating maximum required flow rate of water (40 m3/h) including manually operable gate valves provided at places for isolation purposes wherein one manually operated butterfly valve is provided for regulation of water flow control at outlet of the pump and one no. of manually operated ball valve is provided for installation along with Pressure Gauge in the system, one no. of manually operated NRV each is provided at discharge line and by-pass line of the pump, one no. of manually operated PRV is provided at discharge line of the pump, one no. of strainer (Y type strainer) of suitable capacity to arrest suspended particles of input water is provided at suction line of the pump, strainer elements , one no. of variable area flow meter (Rotameter) with its flanges, matching pump outlet pipe size, pressure gauges , pressure switch to trip the pump whenever there is a total blockage of outlet pipe.

3. The system as claimed in anyone of claims 1 or 2 comprises multi-stage high pressure pump with its drive unit, operator’s control panel, spray ring-headers, spray nozzles, different control valves, in-situ indicators, flow-meters, SS pipelines .

4. The system as claimed in anyone of claims 1 to 3 comprising two water spray ring-headers installed outside the circumferential wall of the Pre-scrubber, connecting with every flat-jet spray nozzle, installed inside the pre-scrubber.

5. The system as claimed in anyone of claims 1 to 4 comprising flange means for connecting every flat-jet spray nozzle, installed inside the Pre-scrubber with the spray ring-header, provided at outside circumference of the Pre-scrubber, said flange connection facilitates for easy dismantling of spray nozzle for its fast replacement.

6. The system as claimed in anyone of claims 1 to 5 comprising flat-jet spray nozzle with unique swivelling head to modify the focusing spray point up to 60 degrees to suitably focus the identified area inside the Pre-scrubber.

7. A method for manufacture of the de-clogging system as claimed in anyone of claims 1 to 6 comprising :

Installing the pump - motor assembly with its main control panel;
water inlet tapping to the pump taken from any existing water header available at a height of +3m and at a horizontal distance of 3m from a pump installation shed;
laying down the delivery line of the pump to a vertical height of +15m (for 1st spray ring-header) and to a height of +24m (for 2nd spray ring-header), taking support of the pre-scrubber tower;
power tapping for motor at the pump shed taken through a cable;

providing valve station mainly comprising of various control valves including by-pass cum pressure control valve, non-return valves, a flow switch, gate valves, a strainer which are located near the pump assembly, inside the pump-house shed for ease of their control operations and maintenance., providing one number of manual isolation valves is provided at the entrance point of each spray ring-headers for isolation of the respective portion of spraying;
providing spray ring-headers at +15m & +25m level positioned around the outer shell of pre-scrubber;

providing around 8 to 12 preferably 10 nos., of spray nozzles in each of the spray ring-headers which are evenly positioned around the pre-scrubber and their tips of the nozzle protruding inside the pre-scrubber;

the spray nozzles are fitted with their respective spray ring-headers through flanged joints for their ease of maintenance/replacement, one each of pressure gauge is provided at inlet & outlet of the pump, inlet of each spray ring-headers for in-situ indication of water pressure.

when the pump is put on, high-pressure water is thus allowed to flow through pipe to one of the spray ring-header (as per the position of the respective isolation valve) and sprays as water-jets inside the pre-scrubber wall through said 10 numbers of spray nozzles targeting some localized areas;

providing means for selectively controlling water-jet impingement in uprooting the settled particulate matters from their location based upon the flow and pressure of the water-jets;

said pump having a re-circulation water line at its delivery with a by-pass pressure setting facility such as to re-circulate the extra water at the delivery line, back into input line, whenever the delivery pressure exceeds the set level.

8. A method for online de-clogging of pre-scrubber in a gas cleaning plant involving the system as claimed in anyone of claims 1 to 6 comprising :
operating the installed on-line water-jet de-clogging system online in tandem with the operation of the pre-scrubber.

9. The method as claimed in claim 8 wherein the step of de-clogging is carried out alternatively through one of the spray ring-headers regularly through impinging water-jets at all critical areas inside the pre-scrubber for prevention of any accumulation of particulate matters of BF gas.

Dated this the 30th day of March, 2022

Anjan Sen
Of Anjan Sen & Associates
(Applicant’s Agent)
IN/PA-199
, Description:FIELD OF THE INVENTION
The present invention relates to a system for online de-clogging of pre-scrubber in Gas Cleaning Plant (GCP) using high pressure water-jet spray. More particularly, the present invention provides for an online system for de-clogging of pre-scrubber in GCP wherein water-jet de-clogging system works in tandem with the operation of the Pre-scrubber. This de-clogging system mainly comprises a multi-stage high pressure pump with its drive, control panel, ring type spray headers with required number of spray nozzles, Control valves, Pressure & Flow indicators, pipes etc. When this de-clogging system operates, high pressure water jets are directed through spray nozzles installed at two numbers of ring type spray-headers, positioned at different levels, covering all the critical locations, inside the Pre-scrubber. The pressure and volume of each water-jet are designed suitably to cater both the requirements of (a) preventing the probabilities of particulate matters of the dirty BF gas settling at inside wall and conical sump of the Pre-scrubber and (b) removing/clearing-out the particulate matters’ build-up, if any formed already at the critical locations inside the Pre-scrubber.

BACKGROUND OF THE INVENTION

The gas cleaning system (Scrubber) of Blast Furnace (BF) is comprised with pre-scrubber located in the upper half of the scrubber shell and three annular gap elements in lower part of the scrubber shell in a single tower. The main purpose of the scrubber is to clean the contaminated top gas of the blast furnace for its further use as fuel gas for heating blast air in the hot blast stoves as well as supplemental fuel in the steel plant. The scrubber also helps to reduce the temperature of the cleaned BF gas to increase its calorific value and to pressure balance the top gas at the outlet of the blast furnace. In this process of top gas cleaning, particulate matter of the contaminated gas is removed by injecting water spray into the dirty gas through number of spray nozzles, centrally arranged at different levels inside the pre-scrubber. The pre-cleaned BF gas, after having passed the water curtains in the Pre-scrubber, enters into the AG scrubber for its further cleaning process. Whereas, the water with the particulate matter (removed from the BF gas)in slurry form, is collected in the conical sump of the Pre-scrubber and is finally discharged to the thickener.

During the process of conveying the slurry (water with particulate matter) from the conical sump of the pre-scrubber to the thickener, some of the coarse particulate matter get disintegrated from the slurry and keep build ups at few critical locations in the conical sump such as on slant surfaces, slurry outlet etc., of the pre-scrubber, due to lack of agitation in the slurry, stagnation tendency in the slurry in the conical sump, very high content of particulate matter in the slurry etc. In the long-run of pre-scrubber operation, these slowly accumulating particulate matters, develops into bigger blocks at its place finally to clog the slurry outlet pipe of the pre-scrubber completely. When the conical sump’s slurry outlet pipe is fully blocked, the Scrubber’s control system automatically switch-off the gas cleaning system, in order to prevent the possibility of the slurry entering the clean gas pipe. This leads to imposed close down of the blast furnace operation immediately, as the gas cleaning system controls the pressure balance of the top gas at the BF outlet. As these progressive increases of clogging of the slurry outlet is not noticeable from outside until it is fully chocked, only the break-down maintenance strategy is the option available.

Similarly, during the process of segregating the particulate matter from the dirty BF gas by spray water curtains, some fine solid particles of the dirty gas escapes from water jets and stick onto nearby inside wall of the pre-scrubber and in the long-run keep-on building-up layer by layer. This continuous accumulation inside the Pre-scrubber’s wall, that is not noticeable by the operator from outside, cause continuous decrease in the useful volume of the spray cleaning space. This leads to reduction in the efficiency of the Scrubber. These build-ups at the top, sometime disintegrate from its place on the inside wall by its increased weight and fall down in to the conical sump, and chock the slurry outlet pipe of the conical sump.

Problems and Limitation of Existing system:

Frequent clogging of the conical-sump of the Pre-scrubber, caused by the progressive build up/accumulation of particulate matters, which are segregated from the slurry,at slant surfaces and at slurry outlet pipe of the conical sump. A fully clogged Pre-scrubber, enforces the gas cleaning system to put-off, that intern leads to unplanned shut-down of the Blast Furnace (BF). An approximate 48 hours of plant shut-down is required to clear the clogged Pre-scrubber for resuming the operation of the gas cleaning plant. A fully clogged Pre-scrubber is also pushing the safety of the operation at high risk as there are chances for the slurry also entering the pipes of cleaned gas.

Limitations:
As the Pre-scrubber is of a completely closed entity like a black-box, the progression/development status of the particulate matters’ accumulation/build up, inside the Pre-scrubber is not noticeable from outside of the Pre-scrubber, until it is fully clogged. However, there is neither any mean/systemexists that prevents theprobability of clogging of the Pre-scrubber due to build-up/accumulation of solid dust particulate matter at few critical places inside the Pre-scrubber, nor to clear-out the already formed build-up/accumulated particulate matter forcibly from its place from inside the Pre-scrubber.

Solution implemented to solve the problems:
In this innovation, an “online water-jets basedde-cloggingsystem” has been installed inside the Pre-scrubber. This water-jet de-clogging system works in tandem with the operation of the Pre-scrubber. This de-clogging system mainly comprises a multi-stage high pressure pump with its drive, control panel, ring type spray headers with required number of spray nozzles, Control valves, Pressure & Flow indicators, pipes etc. When this de-clogging system operates, high pressure water jets are directed through spray nozzles installed at two numbers of ring type spray-headers, positioned at different levels, covering all the critical locations, inside the Pre-scrubber. The pressure and volume of each water-jet are designed suitably to cater both the requirements of (a) preventing the probabilities of particulate matters of the dirty BF gas settling at inside wall and conical sump of the Pre-scrubber and (b) removing/clearing-out the particulate matters’ build-up, if any formed already at the critical locations inside the Pre-scrubber.

OBJECTS OF THE INVENTION

The basic object of the present invention is directed to providea system for online de-clogging of pre-scrubber in Gas Cleaning Plant(GCP) using high pressure water-jet spray.

A further object of the present invention is directed to providea system for online de-clogging of pre-scrubber in GCP wherein said water-jet de-clogging system works in tandem with the operation of the Pre-scrubber.

A still further object of the present invention is directed to saidsystem for online de-clogging of pre-scrubber in GCP whereinhigh-pressure water jets are directed through spray nozzles installed at two numbers of ring type spray-headers, positioned at different levels, covering all the critical locations, inside the Pre-scrubber.

A still further object of the present invention is directed to saidsystem for online de-clogging of pre-scrubber in GCP whereinpressure and volume of each water spray-jet are designed suitably to prevent on one hand settling of particulate matter of gas from BF on inside wall and conical sump of the Pre-scrubber and on the other hand removing/clearing-out the particulate matters’ build-up, if any formed already at the critical locations inside the Pre-scrubber.

A still further object of the present invention is directed to saidsystem for online de-clogging of pre-scrubber in GCP that prevents the settlement of particulate matter at top part inside wall of the Pre-scrubber by continuously dislodging the particulate matters from its early stage of formation of build-ups through continuous impeachments of high-pressure water-jets and hence it eliminates the possibility of clogging of the conical sump of the Pre-scrubber, causes by fall down of bigger build-ups on its weight from the top into the conical sump and clog its slurry outlet.

SUMMARY OF THE INVENTION

The basic aspect of the present invention is directed to a system for online de-clogging of pre-scrubber in a gas cleaning plant comprising:

a pre-scrubber tower including a conical gas entry pathway and spray nozzles centrally arranged at different levels inside the pre-scrubber tower for pre-cleaning of dirt from the gas ;

a conical sump at lower end of the pre-scrubber for collecting the particulate matters in slurry form generated during pre-cleaning of the dirt from the gas;

pipelines for conveying the pre-cleaned gas, generated by the pre-scrubber; to the AG scrubber for its further cleaning;

water spray ring headers including a top spray ring header outside of said pre-scrubber tower towards the top end with adequate number of flat-jet nozzles that covers the full circumferential area inside the conical gas entry region of the pre-scrubber tower, adapted for de-clogging and uprooting the settled particulate matters and a bottom spray ring header provided outside of said pre-scrubber tower, focusing the conical sump area and with adequate number of flat-jet spray nozzles, adapted for de-clogging and uprooting the settled particulate matters inside the conical sump and at slurry outlet pipe of the Pre-scrubber;

pump and motor means for delivering pre-set capacity of water through said water jet spray nozzles with cooperative control valves at said conical gas entry pathway internal face at the top portion of the pre-scrubber tower and said conical sump internal face towards the lower end of the pre-scrubber tower;

said selectively disposed jet nozzles adapted for de-clogging and uprooting settled particulate matters operable in tandem with operation of gas cleaning pre-scrubber for desired online de-clogging of pre-scrubber in a gas cleaning plant.

A further aspect of the present invention is directed to said system comprising:

Said Pump & Motor to deliver pressurized volume of water as per pre-set capacity to major locations including (i) Top spray ring-header at 24m to 26m, preferably +25m level, (ii) Bottom spray ring-header at. 14m. to 16m preferably +15m level and (iii) Jet Nozzle, installed below the conical sump at the slurry outlet pipe.
Said Water spray ring-headers comprises two ring-headers, located outside the Pre-scrubber, at two different levels, focusing the two most identified critical locations of possible build-ups/accumulations of particulate matters inside the Pre-scrubber; 8 to 12, preferably about 10 number of flat-jet nozzles each in the spray ring-header installed to cover the full circumferential area inside the Pre-scrubber;
the spray face of each nozzle is directed towards the nearest side wall with the top spray ring-header located approximately at 25m level, focusing the top conical portion of the Pre-scrubber and the bottom spray ring-header located at approximately at 15 m level, focusing the slant surfaces of the conical sump of the Pre-scrubber;
Said Control Valves: provided based on the operative pipeline size, working pressure head and generating required flow rate of water (40 m3/h) including manually operable gate valves provided at places for isolation purposes wherein one manually operated butterfly valve is provided for regulation of water flow control at outlet of the pump and one no. of manually operated ball valve is provided for installation along with Pressure Gauge in the system, one no. of manually operated NRV each is provided at discharge line and by-pass line of the pump, one no. of manually operated PRV is provided at discharge line of the pump, one no. of Y-strainer of suitable capacity to arrest suspended particles of input water is provided at suction line of the pump, one no. of variable area flow meter based Rotameter with its flanges, matching pump outlet pipe size, pressure gauges , pressure switch to trip the pump whenever there is a total blockage of outlet pipe.

A still further aspect of the present invention is directed to said system comprising multi-stage high pressure pump with its drive unit, operator’s control panel, spray ring-headers, spray nozzles, different control valves, in-situ indicators, flow-meters, SS pipelines .

A still further aspect of the present invention is directed to said system comprising two water spray ring-headers installed outside the circumferential wall of the Pre-scrubber, connecting with every flat-jet spray nozzle, installed inside the pre-scrubber.

A still further aspect of the present invention is directed to said system comprising flange means for connecting every flat-jet spray nozzle, installed inside the Pre-scrubber with the spray ring-header, provided at outside circumference of the Pre-scrubber, said flange connection facilitates for easy dismantling of spray nozzle for its fast replacement.

A still further aspect of the present invention is directed to said system comprising flat-jet spray nozzle with unique swivelling head to modify the focusing spray point up to 60 degrees to suitably focus the identified area inside the Pre-scrubber.

Another aspect of the present invention is directed to a method for manufacture of the de-clogging system as described above comprising:

Installing the pump - motor assembly with its main control panel;
water inlet tapping to the pump taken from any existing water header available at a height of +3m and at a horizontal distance of 3m from a pump installation shed;
laying down the delivery line of the pump to a vertical height of +15m (for 1st spray ring-header) and to a height of +24m (for 2nd spray ring-header), taking support of the pre-scrubber tower;
power tapping for motor at the pump shed taken through a cable;
providing valve station mainly comprising of various control valves including by-pass cum pressure control valve, non-return valves, a flow switch, gate valves, a strainer which are located near the pump assembly, inside the pump-house shed for ease of their control operations and maintenance., providing one number of manual isolation valves is provided at the entrance point of each spray ring-headers for isolation of the respective portion of spraying;
providing spray ring-headers at +15m & +25m level positioned around the outer shell of pre-scrubber;

providing around 8 to 12 preferably 10 nos., of spray nozzles in each of the spray ring-headers which are evenly positioned around the pre-scrubber and their tips of the nozzle protruding inside the pre-scrubber;
the spray nozzles are fitted with their respective spray ring-headers through flanged joints for their ease of maintenance/replacement, one each of pressure gauge is provided at inlet & outlet of the pump, inlet of each spray ring-headers for in-situ indication of water pressure.
when the pump is put on, high-pressure water is thus allowed to flow through pipe to one of the spray ring-header (as per the position of the respective isolation valve) and sprays as water-jets inside the pre-scrubber wall through said 10 numbers of spray nozzles targeting some localized areas;
providing means for selectively controlling water-jet impingement in uprooting the settled particulate matters from their location based upon the flow and pressure of the water-jets;
said pump having a re-circulation water line at its delivery with a by-pass pressure setting facility such as to re-circulate the extra water at the delivery line, back into input line, whenever the delivery pressure exceeds the set level.

A further aspect of the present invention is directed to said method for online de-clogging of pre-scrubber in a gas cleaning plant involving the system as described above comprising :

operating the installed on-line water-jet de-clogging system online in tandem with the operation of the pre-scrubber.

A still further aspect of the present invention is directed to said method wherein the step of de-clogging is carried out alternatively through one of the spray ring-headers regularly through impinging water-jets at all critical areas inside the pre-scrubber for prevention of any accumulation of particulate matters of BF gas.

The above and other aspects and advantages are described hereunder in greater details with reference to following accompanying non-limiting illustrative drawings.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1: shows a Schematic diagram of Pre-scrubber (Existing).
Figure 2: shows Schematic diagram of the water-jets based online de-clogging system of Pre-scrubber according to present invention.
Figure 3: shows the Flat-Jet Nozzle with swivelling head with lock nut installed in present system.
Figure 4: shows the High Pressure pump and motor assembly installed at site for present system.
Figure 5: P&I diagram of water-jet based online de-clogging system of Pre-scrubber according to present invention.

Figure 6: shows the locations for deposits of particulate matter inside the Pre-scrubber.

Figure 7: Spray Ring-Header with Nozzle.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS
As stated herein before,the present invention relates to a system for online de-clogging of pre-scrubber in Gas Cleaning Plant(GCP) using high pressure water-jet spray.This water-jet de-clogging system works in tandem with the operation of the Pre-scrubber. This de-clogging system mainly comprises a multi-stage high pressure pump with its drive, control panel, ring type spray headers with required number of spray nozzles, Control valves, Pressure & Flow indicators, pipes etc. When this de-clogging system operates, high pressure water jets are directed through spray nozzles installed at two numbers of ring type spray-headers, positioned at different levels, covering all the critical locations, inside the Pre-scrubber.

In the existing Scrubber system of GCP, dirty BF gas from Blast furnace enters into the Scrubber (a combination of Pre-scrubber and Annular Gap (AG) scrubber) based Gas Cleaning System from the top. There are several spray nozzles are placed centrally inside the Pre-scrubber to create a water spray curtain into the incoming dirty BF gas. In the process, the particulate matter (solid particles) of the dirty gas is segregated from the gas and mixes with sprayed water as Slurry and discharges to the thickener outside through a buffer storage i.e., Conical Sump of the Pre-scrubber. Whereas the pre-cleaned gas enters into AG scrubber through canopy covered pipes for further cleaning process. The schematic diagram of the Pre-scrubber is shown in Figure 1.

Problems of existing system and the reasons responsible for the problems:
As per the designed purpose of the Pre-scrubber system, all the dust particles of the dirty gas (particulate matter) are either go with the sprayed water as ‘slurry’ to thickener, placed outside the Scrubber system or go with the pre-cleaned gas into AG scrubber, placed underneath the Pre-scrubber through the three pipes for cleaned gas. These pipes are covered at the top with respective canopy to prevent entering of the cleaning water.
However due to some existing system’s design inefficiencies of gas cleaning:
(a) some of very fine particulate matters are keep settling on inside wall of the Pre-scrubber, instead of going either with slurry or with pre-cleaned gas. In the long-run of operations, these accumulations of the solid particles on the inside wall of Pre-scrubber, significantly increases the wall thickness at few places that intern reduces the useful volume of the spray cleaning area, causing decrease in the effectiveness of gas cleaning operation. These accumulations/build-ups on the inside walls, keep on increases its size as the time goes, falls down on its own weight into the conical sump and chocks the sump’s slurry outlet pipe.
(b) Some of the heavy particulate matters of the slurry, segregates themselves from the water, due to poor agitation and long stagnation of the slurry inside the conical sump. These disintegrated heavy particles from the slurry, keep settling on few critical places such as the slant surfaces and slurry’s outlet pipe of the conical sump, finally end up with clogging of the Pre-scrubber.

Changes proposed for de-clogging of pre-scrubber:
1) Introduction of ‘a new high-pressure water-jets spray system for online de-clogging of the Pre-scrubber’ focusing all the identified critical locations inside the Pre-scrubber.
2) This newly introduced water-jet spray system (used for de-clogging the pre-scrubber) is a separate system and operates independently without linking with the operation of the existing water spray system (used for cleaning the dirty gas). Hence this newly introduced de-clogging system does not have any effect on the performance of the Pre-scrubber on its gas cleaning efficiency.

The schematic diagram of the newly introduced water-jet based de-clogging system for Pre-scrubber is shown in accompanying Figure 2.
The newly introduced de-clogging system consists of the following major components/sub-systems:
a) Water spray ring-headers: There are 2 ring-headers, located outside the Pre-scrubber, at two different levels, focusing the two most identified critical locations of possible build-ups/accumulations of particulate matters inside the Pre-scrubber. There are 10 number of flat-jet nozzles each in the spray ring-header installed to cover the full circumferential area inside the Pre-scrubber. These nozzles are of special type uniquely designed with swivelling head with lock-nut arrangement. The photograph of the installed jet nozzle with unique swivelling head is shown in Figure 3. The spray face of each nozzle is directed towards the nearest side wall. The top spray ring-header (#1) is located approximately at 25m level, focusing the top conical portion of the Pre-scrubber. The bottom spray ring-header (#2) is located at approximately at 15 m level, focusing the slant surfaces of the conical sump of the Pre-scrubber.
b) High Pressure multi-stage pump: One 7 stage, horizontal high-pressure pump of approximately 40m3/hr capacity at 400m head has been procured and installed at ground level, inside a pump house near the Scrubber. This pump is driven through 90KW motor. The high-pressure water is delivered to both the spray ring-headers at +25m and +15m levels through ss made pipes. The installed high-pressure pump and motor assembly is shown in Figure 4.

The P&I diagram of the installed, ‘water-jet based de-clogging system of Pre-scrubber’ is shown in accompanying Figure 5.
The spray nozzles installed in the new “De-clogging of Pre-scrubber system is used for removing or clearing-out the already deposited/accumulated/build-up of particulate matter from the inside wall and slurry outlet pipe of the Pre-scrubber. These nozzles do not have any effect on cleaning efficiency of Pre-scrubber.

Hence it is not appropriate to compare the newly installed nozzles (used for clearing-out the accumulated particles) with exiting spray nozzles of the Pre-scrubber (used for cleaning the dirty BF gas).

For clear understanding the purpose of the newly installed nozzles (de-clogging), the probable locations of the accumulated particulate matters (sludge) i.e., on top conical portion of the Pre-scrubber and at inside the conical sump are shown in accompanying Figure 6.

Pump & Motor: To deliver high pressure and high-volume water as per designed capacity to major three locations such as (1) Top spray ring-header at +25m level, (2) Bottom spray ring-header at +15m level and (3) Jet Nozzle, installed below the conical sump at the slurry outlet pipe.

Water spray ring-headers: There are 2 ring-headers, located outside the Pre-scrubber, at two different levels, focusing the two most identified critical locations of possible build-ups/accumulations of particulate matters inside the Pre-scrubber. There are 10 number of flat-jet nozzles each in the spray ring-header installed to cover the full circumferential area inside the Pre-scrubber. These nozzles are of special type uniquely designed with swivelling head with lock-nut arrangement. The photograph of he installed jet nozzle with unique swivelling head is shown in Figure 3. The spray face of each nozzle is directed towards the nearest side wall. The top spray ring-header (#1) is located approximately at 25m level, focusing the top conical portion of the Pre-scrubber. The bottom spray ring-header (#2) is located at approximately at 15 m level, focusing the slant surfaces of the conical sump of the Pre-scrubber.

Control Valves: Different types of valves with SS 304 internal and other instruments as specified below in adequate numbers as necessary in the system is designed and provided in the pipeline network, considering the pipeline size, working pressure head and maximum required flow rate of water (40 m3/h) etc. Manually operated gate valves in adequate quantities are providedat places for isolation purposes. One no. of manually operated butterfly valve is considered for regulation of water flow control at outlet of the pump.One no. of manually operated ball valve is considered for installation alongwith every Pressure Gauge in the system.One no. of manually operated NRV each is considered at discharge line and by-pass line of the pump.One no. of manually operated PRV is considered at discharge line of the pump. One no. of strainer (Y type strainer) of suitable capacity to arrest suspended particles of input water is considered at suction line of the pump. Strainer elements are of SS-304 or better. One no. of variable area flow meter (Rotameter) with its flanges, matching pump outlet pipe size. IP-55 or better, accuracy +/- 2% (min) of measured value, is also installed. Adequate numbers of pressure gauges as necessary in the system are considered. One number pressure switch is provided to trip the pump (to safeguard), whenever there is a total blockage of outlet pipe.

The pump - motor assembly with its main control panel is installed inside a 4m x 3m pump-house shed, newly constructed at ground level, near the existing hydraulic control room of GCP. The steel structurally supported, pump-house shed has been constructed with RCC foundations and PCC+IPS flooring. All the four sides and roof of the shed are covered by CGI sheets with a door at front. The shed is also provided with 1T capacity manual chain pulley block for maintenance of the installed system.
Water inlet tapping to the pump has been taken from the existing water header available at a height of +3m and at a horizontal distance of 3m from the pump shed through SS pipe of 100NB. The delivery line of the pump has been laid through SS pipe of 80NB to a vertical height of +15m (for 1st spray ring-header) and to a height of +24m (for 2nd spray ring-header), taking support of the pre-scrubber tower. Power tapping for motor at the pump shed has been taken through a 150 sq.mm x 4 core cable, from the GCP’s MCC room located at a horizontal distance of 100m.

The valve station mainly consisting of various control valves such as a by-pass cum pressure control valve, non-return valves, a flow switch, gate valves, a strainer etc., are located near the pump assembly, inside the pump-house shed for ease of their control operations and maintenance. One number of manual isolation valves is provided at the entrance point of each spray ring-headers for isolation of the respective portion of spraying.

The spray ring-headers at +15m & +25m level are positioned around the outer shell of pre-scrubber. There are 10 nos., of spray nozzles in each of the spray ring-headers which are evenly positioned around the pre-scrubber and their tips of the nozzle protruding inside the pre-scrubber. The positioning of the spray nozzles on the wall of the Pre-scrubber with the spray ring-header is shown in Figure 7.

The spray nozzles are fitted with their respective spray ring-headers through flanged joints for their ease of maintenance/replacement. One each of pressure gauge is provided at inlet & outlet of the pump, inlet of each spray ring-headers for in-situ indication of water pressure.
When the pump is put on, high-pressure water flows through pipe to one of the spray ring-header (as per the position of the respective isolation valve) and sprays as water-jets inside the pre-scrubber wall through 10 numbers of spray nozzles targeting some localized areas.
The effectiveness of water-jet impingement in uprooting the settled particulate matters from their location totally depends upon the flow and pressure of the water-jets. The pump has a re-circulation water line at its delivery with a by-pass pressure setting facility. This facility helps to re-circulate the extra water at the delivery line, back into input line, whenever the delivery pressure exceeds the set level.

The installed on-line water-jet de-clogging system is operated online in tandem with the operation of the pre-scrubber. The installed system is presently operated alternatively through one of the spray ring-headers regularly through impinging water-jets at all critical areas inside the pre-scrubber for prevention of any accumulation of particulate matters of BF gas.

It is thus possible by way of the present invention to provide an online water-jets based de-clogging system of pre-scrubber of GCP of blast furnace having following advantageous features:
(a) A high-pressure water-jets based de-clogging system that clears-out/remove the accumulated build-up of particulate matters of dirty BF gas from inside the Pre-scrubber. Continuous operation of this water-jets based de-clogging system in tandem with regular operation of gas cleaning system helps in preventing any further accumulation of particulate matters of the dirty BF gas inside the pre-scrubber. Hence this newly implemented system improves the availability and reliability of the Pre-scrubber.

(b) This system comprises a multi-stage high pressure pump with its drive unit, operator’s control panel, spray ring-headers, spray nozzles, different control valves, in-situ indicators, flow-meters, SS pipelines etc. (Refer Figure 5)

(c) Two nos. of SS-304 made, water spray ring-headers (Refer Figure 7), installed outside the circumferential wall of the Pre-scrubber, connecting with every flat-jet spray nozzle, installed inside the pre-scrubber.

(d) Unique flange system,that connects everyflat-jet spray nozzle, installed inside the Pre-scrubber with the spray ring-header,provided at outside circumference of the Pre-scrubber. This flange connection facilitates for easy dismantling of spray nozzle for its fast replacement. (Refer Figure 7).

(e) Flat-jet spray nozzle with unique swivelling head (Refer Figure 3), to modify the focusing spray point up to 60 degrees to suitably focus the identified area inside the Pre-scrubber.