ALKALINE FLUSHING, PICKLING & PASSIVATION FOR HRSG WATER TUBE BOILER x 3 UNITS FOR GENERATING, ECONOMISER, MAIN STEAM & EVAPORATOR TUBE BANKS AT ND PAPER MILL BANTING PLANT. 2023
3 HRSG SYSTEMS – NINE DRAGON PAPER MILL.
Main Objective of chemical circulation: (Alkaline boil out + pickling & passivation)
Superheater tubes material identify as A-213M T22 (chrome Molly) LP & HP, A106M GrB (CS), A312M TP304 (SUS)sections & related steam & water drum of HRSG water tube boiler to remove the organic substances such as oil, grease, tube coatings (not inclusive of Japanese black) to prevent metal protection and achieve pickling process the most. The related relaxed impurities at tube inner surface/wall shall be flushed out using a high temp water at 65ºC circulation and followed with chemical circulation to pickling to passivation the tubing’s on its proposed concentration. While circulation every 2hrs a pH reading will be observed to maintain chemical concentration, followed with a phosphate test @ 2ppm, fe test, pH test & visual oil trace.
- To provide 3units chemical circulation pump/dosing pump at min 8-10 bar saturated pressure to circulate the internal with return manifold, filter stand, filter bags and qualified technicians to remove an internally formed harden and rust, scale formations. Provision 8pax skilled technician to perform the alkaline boil out & pickling & Passivation process with provision proper temporary pools, hoses, fittings, chemicals, related PPE for safe work, consumables, provision of Di water & holding tanks (IBC),
- To make a temporary isolation, remove & refit insulations and looping with the piping flanges, a leak test (x1 times) will perform with Demin/fresh hot water for 3 hours, continue to introduce alkaline based chemical gradually add solution in water and to circulate for minimum 5-6 hours to reach equilibrium state, where the ambient temperate approx 65°C reached.
- Random check on the steam & water drum. Circulation/soak with – boiled out solutions at 0.05% concentration for min 8-24hours. Drain effluent and flush with Demin water and a pH reading will be observed as a chemical neutralized <9pH.
- For pickling process adding pickling solution with 75% concentration and circulate 6 – 10 hrs until pH 4 -5 was observed to remove any hardly build rust at tube internals & drums respectively.
- Followed with a passivation process adding passivation solutions 35% (concentration) and circulate for 4hrs.
- Neutralising process adding 55% (concentration) of chemical for produce a protective film at tube internals and drums and circulate for 6hrs.
- Alkaline flushing procedure application specifically on condition of the wall surface of tubes & drums to observe where oxides development, rust eliminated after the process circulation works.
- Final check on drum for oil traces if any.
- Upon reaching the state of equilibrium stop circulation/application and drain the effluent.
