Tech. Info.

1.1 Pickling Line
Pickling Line is a process of removing strip scale and impurities on carbon steel plate surface physically (chemically) Oxide layer generated on the surface of carbon steel, depending on the heat treating temperature and cooling rate, are 3 kinds such as typically FeO (Wustite), Fe3O4 (Magnetite) and Fe2O3 (Hematite) in general and most of them are FeO and take about 95% in total oxides.

The following figure shows the oxide layer on the surface of carbon steel.

As for chemical means for removing metal surface scale, there are hydrochloric acid pickling, sulfuric acid pickling, fluoric acetic acid alkali molten salt method but hydrochloric acid and sulfuric acid are generally used for acid pickling for carbon steel surface. Sulfuric acid was most used initially, but sulfuric acid is most favored owing to the development of acid collection technologies and acid-resistant equipment and facilities .As sulfuric acid has low oxidize metal solubility, acid pickling time takes twice more under the same temperature and concentration conditions than hydrochloric acid pickling and energy consumption is high due to high temperature requirements. The largest advantage of using hydrochloric acid is high regeneration efficiency as all acid stained on the surface in various ways or in liquid state can be collected and dissolved steel can be extracted in oxidized steel form to be used for other purposes.

The chemical reaction formula using hydrochloric acid pickling method is as followings.

Fe2O3 + 4HCl ⇒ 2FeCl2 + 2H2O + 1/2 O2

Fe3O4 + 6HCl ⇒ 3 FeCl2 + 3H2O + 1/2 O2

FeO + 2HCl ⇒ FeCl2 + H2O

Fe + 2HCl ⇒ FeCl2 + H2

The waste acid generated in the above chemical formula is transferred to the acid collection facilities, the acid collection facilities regenerate waste acid by the thermal hydrolysis method and re-provide to the acid pickling process. The relation between the acid pickling process and acid collection process are shown as the following figure.

1.2 Acid Regeneration Process

Waste acid generated in the pickling line is stored in the waste acid tank (T-300A / B water operation Tank), pass through a filter by the waste acid pump (P-300 A / B) by pass filter, and supplied to a separator after the residual material is removed.

The waste acid supplied is mixed with concentrated acid which was supplied earlier, supplied to the upper part of Venturi by condensed tower circulation pump(P-130 A/B Concentrator Circulation Pump) and the solution condensed by direct contact with high temperature gas (380 ~ 400 ℃) discharged from the roaster. So the process (absorption and rinsing) after a separator can be made with polymer materials.

Waste acid solution supplied from a separator is condensed into about 75% of the initial volume by evaporation due to calories of roaster gas. The higher temperature of Roaster gas, the higher concentration efficiency of waste sulfuric acid solution is but rinsing water should be supplied to prevent over crystallization. Dust (fine oxidized steel) is slowly dissolved by hydrochloric acid and concentration of FeCl3 further increases.

Part of concentrated acid supplied from the concentration tower circulation pump (P-130 A / Concentrator Circulation Pump) to Venturi is supplied to the spray nozzle within the roaster by roster supply pump (P-110 A/B Roaster Spray Pump).

The hydrolysis reaction within a reactor occurs as follows:

2FeCl2 + 2H2O + 1/2O2 ⇒ Fe2O3 + 4HCl

2FeCl3 + 3 H2O ⇒ Fe2O3 + 6HCl

H2O(Liquid) ⇒ H2

HCl(Liquid) ⇒ HCl(Gas)

Energy required for the thermal hydrolysis reaction is supplied by 3 burner units installed in the tangent line at the bottom of the Roaster. Burner System supplied calories needed for the thermal hydrolysis reaction by forming flow (spiral flow) where of internal flame rotates.

When flame is emitted from Burner System maintains the inside of Roaster at 650 ~ 700 °C, the high-temperature gas goes upward within Roaster and gets out of Roaster after cooling at 380 ~ 400 °C due to reaction with condensed acid. First, oxide dust, hydrogen chloride, high temperature roaster exhaust gat pass through Cyclone, a centrifugal dust collector and flows into the Venturi and separator process after removing fine dust.

Roaster exhaust gas cooling at Venturi & Separator process flows into the upper part of Absorber. Filling substance is filled in Absorber as it should improve reactivity by extending contact area at the time of gas-liquid contact with absorption rinsing and the gas flowed into the bottom contact with absorptive liquid supplied from Rinse Water Pump (P-320 A/B) in the upper part while passing through filling material layer to regenerate 18~20wt% acid. Regenerated acid produced is stored at the tank and supplied to pickling process by the regeneration pump.

The process gas discharged from Absorber is transferred to Scrubber by Exhaust Fan (F-180) which maintains the total process at the vacuum (-).Exhaust Fan (F-180) of variable type (VVVF) changes operation velocity by the reference of internal pressure of Roaster and maintains the pressure of whole process by changing the velocity in reference to internal pressure of Roaster which an operator inputs.

The component of hydrochloric acid of which is contained while passing through the process gas scrubber which is flowed in Scrubber by a fan is removed and emitted to the air. Scrubber is emitted into the air through stack by inputting, circulating NaOH into rinsing water and neutralizing HCl and Cl2 in gas.

Neutralization reaction formula within a scrubber is shown below..

HCl + NaOH ⇒ NaCl + H2O

Cl2 + 2NaOH ⇒ NaCl + NaClO + H2O

Iron oxide (Fe2O3 Iron oxide which passes the screen is moved into Oxide Storage Bin by Conveying Fan (F-210) and released after storage and packing. , Iron Oxide) generated by the pyrolysis reaction of CWA within roaster falls to the bottom of Roaster by self-load and lumps which are often generated are crushed by the Lump Breaker and discharged.
Iron oxide which is supplied constantly by Rotary Valve is provided to TSC (Twin Screw Conveyor) and lumps which are not crushed at Lump Breaker is separated from oxidized steel in the transferring pipe screen and discharged.

Iron oxide which passes the screen is moved into Oxide Storage Bin by Conveying Fan (F-210) and released after storage and packing.

1.3 Sleeve Unit Process
1. Sleeve Unit Is Process To Raw Metal Sheet Each Size Rolling & Making Metal Sleeve.
2. Sleeve- Making Process Step’s.

2.1 Metal Cut Sheet Quality Check.
– As Per Standard Requirement Metal Cut Sheet Size (Length*Width*Thickness) & Sheet Cut Edge Check.

2.2 “V” Grinding.
– Purpose Of Both Edge “V” Grinding Is Making For Good Strength Joint Aera.

2.3 Sheet Bending.
– As Per Standard Diameter (ID & OD) Rolling Metal Sheet Also Check Proper Round Shape.
– Max Rolling Capacity :- Width 1450mm, Thickness 16mm

2.4 Sleeve Tacking.
– Both Edge Tack Weld Is To Hold Parts Of An Assembly In Proper Alignment Temporarily Until The Final Welds Are Made.

2.5 Final Welding (Co2 & Arc).
– Weld From Both Sides Of The Joint, A Full-Penetration Weld Is Easier To Accomplish. For Thin Material The Edges Can Be Butted Together.

2.6 Final Grinding (Polishing)
– Grinding Is A Material Removal & Surface Generation Process Used To Finish Final Metal Sleeve Made.

2.7 Quality Inspection.
– Sleeve Diameter, In & Out Final Grinding Size, Both Edge Area Match, Cracks Or Holes On Final Welding Point.

3.Bending Machine Operation Process.