Claims:We Claim:

1. A system for post pickling arresting of acid and salt carryover by pickled coils in pickling line comprising:

means for post pickling rinsing by spraying rinsing water, collection of rinsing water from bottom and recirculation upto desired pH of rinsing water followed by means for squeezing of the rinsing water over the strip surface,

said means for post pickling rinsing comprising:

combination of plurality of cold rinsing tanks followed by plurality of hot rinsing tanks,

each said cold rinsing tanks and hot rinsing tanks provided with selectively disposed spray headers including top spray hearers and bottom spray headers for rinsing of the pickled coils from top and bottom during passage through said rinsing tanks wherein the said top spray headers are disposed with respect to tank body such as to maintain a reduced spray height in the range of 370 to 390 mm preferably about 380 mm and said bottom spray header is maintained spray height of 380 to 400 mm for desired complete coverage of the strip for rinsing ; and

said means for squeezing of the rinsing water comprising pneumatic squeezing means .

2. The system as claimed in claim 1 wherein said rinsing spray headers disposed close to the strip are strengthened by fiber reinforced plastic linings to sustain damages from strip movement and high temperature of rinsing water in the range of 85 to 900C.

3. The system as claimed in anyone of claims 1 or 2 comprising polytetrafluoroethylene (PTFE) line pipelines connected to said spray hearers.

4. The system as claimed in anyone of claims 1 to 3 wherein the top spray headers are provided to have stiffness of the rinsing header ensured at 85-90°C of rinsing water, such that header should not sag during continuous operation and bottom spray headers are provided to have [similar mechanical property to withstand 85-90°C temperature of rinsing water such as to maintain reduced spray height for desired coverage witout any sagging.

5. The system as claimed in anyone of claims 1 to 4 comprising said top spray headers operatively connected involving fixed piping arrangements and rinsing tanks provided with flanged end connection in other side of tank to provide strength and stiffness This also provide provision for periodic inspection and flushing of top headers from other side. Necessary modification in the tank made to provide flange end connection to the top headers from other side.

6. The system as claimed in anyone of claims 1 to 5 comprising spray nozzles including flat spray, Spray pressure:1.5-2 bar, Flow rate: 16 lpm (±10%) at 2 bar, Spray angle:90°, Min Bore diameter: 3 mm, material: Polypropylene.

7. The system as claimed in anyone of claims 1 to 6 wherein said pneumatic squeezing means comprises:

pneumatic cylinder assembly with bellow comprising of clevis, spring and connecting pin,
pneumatic Valve Stand including FRL unit, hand operated valves,
refrigerant type Air Drier, and
air receiver.

8. The system as claimed in anyone of claims 1 to 7 comprising pneumatic cylinders mounted in squeezer rolls, wherein two pneumatic cylinders are provided for each squeezer roll, clevis & connecting bracket for operatively connecting a piston rod with choke of top squeezer roll for mounting the pneumatic cylinder, each set of pair of pneumatic cylinders for each squeezer roll is operated by pneumatic valve, said pneumatic valves including preferably hand operated 3 position valve and pressure relief valves for operating the cylinders with cooperatively connected pneumatic valve station for operating the pneumatics of all the set of squeezer rolls with said pneumatic means provided to maintain squeezing pressure of 15000 to 17000 N preferably 16000 N on each side of the squeezer rolls.

9. The system as claimed in anyone of claims 1 to 8 comprising rinsing system including five tanks comprising three cold and two hot rinsing tank and squeezing system comprising seven sets of squeezing rolls including :

d) Pneumatic Cylinder Assembly having:
Bore - 200 mm,
Stroke - 155 to 165 preferably 160mm with rubber bellows to cover piston rod and connecting rod,
Double acting with adjusted cushioning at both ends;
e) Pneumatic Valve Stand including FRL unit:
Linear Slide Valve 1” BSP Hand Lever Operated (3 Position);
f) Air Dryer Unit comprising:
Refrigerated type compressed air dryer,
Air quantity: 230 to 270 preferably about 250 m3/hr., Operating pressure: 2.5 to 4.0 preferably about 3.5 Bar(g),
Outlet pressure dew point: +2 to +6 preferably + 4 C to 6 C.

Dated this the 20th day of March, 2021
Anjan Sen
Of Anjan Sen & Associates
(Applicants’ Agent)
IN/PA-199

, Description:FORM 2
THE PATENT ACT 1970
(39 OF 1970)
&
The Patent Rules, 2003
COMPLETE SPECIFICATION
(See Section 10 and Rule 13)

1 TITLE OF THE INVENTION :
A SYSTEM FOR POST PICKLING ARRESTING OF ACID AND SALT CARRYOVER BY PICKLED COILS IN PICKLING LINE.



2 APPLICANT (S)

Name : STEEL AUTHORITY OF INDIA LIMITED.

Nationality : Indian.

Address : Research & Development Centre for Iron & Steel,
Doranda, Ranchi, Jharkhand, India. PIN-834002.






3 PREAMBLE TO THE DESCRIPTION

COMPLETE

The following specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF THE INVENTION
The present invention relates to a system for post pickling arresting of acid and salt carryover by pickled coils in pickling line. More particularly, the present invention is directed to said system for post pickling, controlled rinsing and squeezing to prevent acid/salt carryover to remove any acid residues that could cause corrosion later on and ensure achieve cleaner and brighter pickled strip surface before cold reduction.

BACKGROUND OF THE INVENTION
Pickling Line-2 (PL-2) of Applicant’s Bokaro Steel Plant (BSL) has a Hydrochloric (HCl) acid pickling line with capacity of 0.80 mt/yr. The line width of PL-2 is 1420 mm. The thicknesses of the coils processed at PL-2 are in the range of 1.2-5 mm and the maximum speed is 450 m/min in delivery side. Efficiency of pickling line plays an important role in getting a cleaner and brighter strip surface before cold reduction. After the pickling process is finished, the pickled strip is rinsed with water to remove any acid residues that could cause corrosion later on. Thus, post pickling, rinsing and squeezing are done to prevent acid/ salt carryover and achieve brighter pickled surface.
There are three cold and two hot rinsing tanks at PL-2 for preventing acid carry over and achieve clean and bright strip surface. The layout of PL-2 is depicted in Fig.1. The rinsing water is sprayed from top and bottom spray headers on the strip to remove the acid and salt carried from pickling tanks. The rinsing water is collected from the bottom of the tank and recirculated through rinsing pump to rinsing spray headers. The flow rate of the rinsing pump of each tank is 55 m3/hr at 2 bar. Top-up water is added to maintain water level in rinsing spray header. Once the pH of the rinsing water reaches a specified level, it is discarded and fresh water is filled up in the tank. The first three tanks after pickling are for cold rinsing and last two tanks are meant for hot rinsing of pickled strip. There are two top and two bottom rinsing spray headers in each section. Thus there are total ten top rinsing spray headers and ten bottom rinsing spray headers. The arrangement of distribution spray header of one of the rinsing tank is shown in Fig.2. Top spray header was attached to tank cover and flexible hose was used to connect the top spray header with distribution spray header(Fig.3). The flexible hose was frequently damaged leading to leakages and reduced rinsing efficiency as shown in Fig.4.
Further, the rubberised squeezer rolls are used to squeeze out the rinsing water over the strip surface during rinsing in pickling lines. Each set of squeezer roll, comprises of 2 rubberized rolls supported at both end. The pressure is applied on the top roll at both the end and bottom roll is supported in the frame. Earlier, the pressure between top and bottom squeezer rolls was adjusted by spring loaded mechanism resulting in lesser squeezing pressure.
Thus, Inadequacy in rinsing system and lesser squeezing pressure led to acid/ salt carryover from pickling line and surface defects like black patch in downstream operations.

Constraint with previous rinsing system:
a) Rinsing System:
• Top spray header was attached to tank cover and flexible hose was used to connect the top spray header with distribution spray header. The flexible hose was frequently damaged leading to leakages and reduced rinsing efficiency.
• Due to frequent leakages, around 50% of the rinsing headers were not in use. Thus, flow distribution within a rinsing tank was not uniform.
• Sagging of top headers led to improper coverage of strip width.
• Bottom rinsing headers were rested on tank refractory. This led to damage of headers by in case of strip movement in downward direction.
• The spray height of top spray header was 856 mm from the strip. With this spray height, three was reduced rinsing impact from top headers. Thus, inadequate rinsing contributed to acid/salt carryover and surface defects like black patch in downstream operations.

b) Squeezing System:
• The pressure between top and bottom squeezer rolls is adjusted by spring loaded mechanism resulting in lesser squeezing pressure (Fig.5).
• Lesser squeezing pressure contributed to acid/salt carryover and surface defects in downstream operations.

There has been thus a need to develop an improved system to arrest acid and salt carryover from the pickled coils in pickling line and thereby avoid surface defect and corrosion in down stream application and obtain cleaner and brighter pickled strip surface prior to cold reduction.

OBJECTS OF THE INVENTION
The basic object of the present invention is directed to provide a system for post pickling arresting of acid and salt carryover by pickled coils in pickling line.
A further object of the present invention is directed to a system for post pickling arresting of acid and salt carryover to avoid surface defect like black patch or corrosion of sheet surface in downstream operations.
A still further object of the present invention is directed to a system for post pickling arresting of acid and salt carryover to improve cleanliness and brightness of pickled strips.
A still further object of the present invention is directed to provide a system for post pickling arresting of acid and salt carryover by pickled coils in pickling line for improvement in surface reflectance after pickling by 10% (from 80% to 90%).
A still further object of the present invention is directed to provide a system for post pickling arresting of acid and salt carryover by pickled coils in pickling line to favour reduction in surface chloride level of pickled coils by 50% (from 400 to 200 mg/m2/side).

SUMMARY OF THE INVENTION

The basic aspect of the present invention is directed to a system for post pickling arresting of acid and salt carryover by pickled coils in pickling line comprising:

means for post pickling rinsing by spraying rinsing water, collection of rinsing water from bottom and recirculation upto desired pH of rinsing water followed by means for squeezing of the rinsing water over the strip surface,

said means for post pickling rinsing comprising:

combination of plurality of cold rinsing tanks followed by plurality of hot rinsing tanks,

each said cold rinsing tanks and hot rinsing tanks provided with selectively disposed spray headers including top spray hearers and bottom spray headers for rinsing of the pickled coils from top and bottom during passage through said rinsing tanks wherein the said top spray headers are disposed with respect to tank body such as to maintain a reduced spray height in the range of 370 to 390 mm preferably about 380 mm and said bottom spray header is maintained spray height of 380 to 400 mm for desired complete coverage of the strip for rinsing; and

said means for squeezing of the rinsing water comprising pneumatic squeezing means.

A further aspect of the present invention is directed to said system wherein said rinsing spray headers disposed close to the strip are strengthened by fiber reinforced plastic linings to sustain damages from strip movement and high temperature of rinsing water in the range of 85 to 900C.

A still further aspect of the present invention is directed to said system comprising polytetrafluoroethylene (PTFE) line pipelines connected to said spray hearers.

A still further aspect of the present invention is directed to said system wherein the top spray headers are provided to have stiffness of the rinsing header ensured at 85-90°C of rinsing water, such that header should not sag during continuous operation and bottom spray headers are provided to have [similar mechanical property to withstand 85-90°C temperature of rinsing water such as to maintain reduced spray height for desired coverage without any sagging.

Another aspect of the present invention is directed to said system comprising said top spray headers operatively connected involving fixed piping arrangements and rinsing tanks provided with flanged end connection in other side of tank to provide strength and stiffness, that also provide provision for periodic inspection and flushing of top headers from other side, wherein necessary modification in the tank made to provide flange end connection to the top headers from other side.

A further aspect of the present invention is directed to said system comprising spray nozzles including flat spray, Spray pressure:1.5-2 bar, Flow rate: 16 lpm (±10%) at 2 bar, Spray angle:90°, Min Bore diameter: 3 mm, material: Polypropylene.

A still further aspect of the present invention is directed to said system wherein said pneumatic squeezing means comprises:

pneumatic cylinder assembly with bellow comprising of clevis, spring and connecting pin,
pneumatic Valve Stand including FRL unit, hand operated valves,
refrigerant type Air Drier, and
air receiver.

A further aspect of the present invention is directed to said system comprising pneumatic cylinders mounted in squeezer rolls, wherein two pneumatic cylinders are provided for each squeezer roll, clevis & connecting bracket for operatively connecting a piston rod with choke of top squeezer roll for mounting the pneumatic cylinder, each set of pair of pneumatic cylinders for each squeezer roll is operated by pneumatic valve, said pneumatic valves including preferably hand operated 3 position valve and pressure relief valves for operating the cylinders with cooperatively connected pneumatic valve station for operating the pneumatics of all the set of squeezer rolls with said pneumatic means provided to maintain squeezing pressure of 15000 to 17000 N preferably 16000 N on each side of the squeezer rolls.

A further aspect of the present invention is directed to said system comprising rinsing system including five tanks comprising three cold and two hot rinsing tank and squeezing system comprising seven sets of squeezing rolls including:

a) Pneumatic Cylinder Assembly having:
Bore - 200 mm,
Stroke - 155 to 165 preferably 160mm with rubber bellows to cover piston rod and connecting rod,
Double acting with adjusted cushioning at both ends;
b) Pneumatic Valve Stand including FRL unit:
Linear Slide Valve 1” BSP Hand Lever Operated (3 Position);
c) Air Dryer Unit comprising:
Refrigerated type compressed air dryer,
Air quantity: 230 to 270 preferably about 250 m3/hr., Operating pressure: 2.5 to 4.0 preferably about 3.5 Bar(g),
Outlet pressure dew point : +2 to +6 preferably + 4 C to 6 C.

The above and other advantages of the present invention are described hereunder in greater details with reference to the accompanying non limiting illustrative drawings.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig 1-5 relate to features of existing system and Fig 6-12 relates to modified spray rinsing and squeezing system according to present invention as follows:
Fig.1. Layout of Pickling Line-2, CRM.
Fig.2. Distribution of Rinsing pipeline of one tank.
Fig.3. Arrangement of Rinsing Top Headers.
Fig.4. Hose connection of Top Headers.
Fig.5. Manual Squeezing System.
Fig.6. Location of Top Spray header in a Rinsing tank.
Fig.7. Drawing of Modified Rinsing Header.
Fig.8. Modified Rinsing Headers.
Fig.9. Modified PTFE Line Pipelines.
Fig.10. Design of Pneumatic Squeezing System.
Fig.11. Scheme of Pneumatic Squeezing System.
Fig.12. Modified Squeezing System.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO ACCOMPANYING DRAWINGS
The present invention is directed to provide a system for post pickling arresting of acid and salt carryover by pickled coils in pickling line and thereby reducing surface defects and improving the cleanliness and brightness of pickled sheets.
At existing Pickling Line-2, there are three cold and two hot rinsing tanks along with seven set of squeezer rolls for removing acid and salt from the pickled strip surface.
Earlier, the top rinsing spray headers were fixed in rinsing tank covers and connected to main pipelines by hoses. Rinsing was not effective due to increased spray height. In the previous squeezing system, pressure was set manually, resulting in reduced squeezing and non-uniform pressure on the both side of squeezer rolls, leading to rinsing water, salt and acid carryover along with strip. Further, in previous system, removing and fixing of hoses during maintenance led to frequent leakages from the hoses and pipelines resulting in lower water level in rinsing tanks and hence, insufficient rinsing of the strip.
The previous rinsing system as illustrated through Fig 1-5, was modified by relocating the top spray headers from tank cover to tank itself. Further, introduction of modified rinsing spray headers and pipelines were done to improve the rinsing efficiency. The earlier squeezing system has been modified by incorporating pneumatic system for effective squeezing pressure. The pneumatic system was designed to maintain the squeezing pressure of 16000 N on each side of the squeezer rolls.

Design of new Rinsing System:
The rinsing system of all the five tanks have been redesigned for relocating the top spray headers from tank cover to tank body(Fig.6). Relocating the top spray headers from tank cover to tank body, has led to optimum spray height (380 mm) leading to efficient rinsing. Rinsing spray headers have been modified with reduction in spray height and to ensure complete coverage of strip (Fig.7). The spray nozzles were selected to improve water impingement on the strip for effective rinsing. Spray headers have been additionally strengthened by Fiber Reinforced Plastic (FRP) linings to sustain damages from strip movement and high temperature of rinsing water (Fig.8). The Polytetrafluoroethylene (PTFE) line pipelines were also redesigned as per site constraint, for each tank to accommodate the relocation of modified headers (Fig.9).
Thus, the major modifications carried out in the rinsing system of PL-2, CRM, BSL are:
a) Relocating the top spray header from tank cover to tank body. The stiffness of the rinsing header ensured at 85-90°C of rinsing water, such that header should not sag during continuous operation.
b) Re-design of top spray header due to change in spray height from the strip.
c) Replacement of top and bottom spray headers as per new design.
d) Replacement of flexible hose with fixed piping for top spray header connections leading to reduced rinsing water leakages and ease in maintenance.
e) Necessary modification in each rinsing tank to support top spray headers on the other side of the tank.
f) Modification in distribution spray headers, valves, pipes, bends etc. for new top & bottom spray headers.
g) Nozzle details: Flat spray, Spray pressure:1.5-2 bar, Flow rate: 16 lpm (±10%) at 2 bar, Spray angle:90°, Min Bore diameter: 3 mm, Material: Polypropylene

Modification of Squeezing System:
The previous squeezing system has been modified by incorporating pneumatic system for effective squeezing pressure as shown in Fig.10.
The pneumatic system mainly comprises of
• Pneumatic cylinder assembly with bellow consisting of clevis, spring and connecting pin
• Pneumatic Valve Stand including FRL unit, hand operated 3 position valves
• Refrigerant type Air Drier
• Air receiver

The schematic diagram of modified squeezing system is shown in Fig.11. Pneumatic cylinders have been mounted in all the seven sets of squeezer rolls. Two pneumatic cylinders are required for each squeezer roll. Necessary modifications were carried out in clevis & connecting bracket for connecting piston rod with choke of top squeezer roll for mounting the pneumatic cylinder. Each set of pneumatic cylinders ( 2 nos) for each squeezer roll is operated by pneumatic valve. Pneumatic valves (hand operated 3 position valve and pressure relief valves) has been selected for operating the cylinders. Pneumatic valve station to be fabricated and installed at the identified location for operating the pneumatics of all the seven set of squeezer rolls. The installed system is shown in Fig.12.
Details of major components:
a) Pneumatic Cylinder Assembly:
• Bore - 200 mm min.
• Stroke - 160mm with rubber bellows to cover piston rod and connecting rod
• Double acting with adjusted cushioning at both ends
b) Pneumatic Valve Stand including FRL unit:
• Linear Slide Valve 1” BSP Hand Lever Operated (3 Position)
c) Air Dryer Unit:
• Refrigerated type compressed air dryer
• Air quantity: 250 m3/hr., Operating pressure: 3.5 Bar(g).
• Outlet pressure dew point : + 4 C to 6 C

Usefulness of the invention

With the above mentioned innovation, the quality of pickled coils have improved in PL-2, CRM, BSL. The efficiency of the installed system was measured in terms of surface reflectance of pickled coils by tape test using smoke stain reflectometer (Model No- M43D). The surface reflectance has improved from 80% to 89% after installing the modified systems.
Similarly, surface chloride level were also measured before initiation of the project as base data. The surface chloride has reduced by 40% (from 400 to 238 mg/m2/side) after installing the modified systems. The surface chloride were measured using titration method for both before and after installing the total system.
Modification in rinsing system has also led to ease in maintenance, as loose parts such as hose have been replaced with fixed piping. This has also helped in unwanted leakages of acidic water and improved rinsing.
The invention has also led to reduction in delay on account of bad quality. The average delay due to bad quality has reduced by 48% (from 5.23 hours/ month to 2.67 hours/month).