Operational experience for the recycling of process water and acids Realist projects I. Project INDIA (2017) ZLD for rinse water HCl pickling line II. Project China (2017) ZLD for rinse water and spent acid HCl pickling line III. Project Schweden (2011) ARP for spent mixed acid pickling line ZLD = Zero Liquid Discharge ARP = Acid Regeneration Plant 1
I. Project INDIA: ZLD for rinse water HCl pickling line 2
I. Project INDIA: ZLD for rinse water HCl pickling line 3
I. Project INDIA: ZLD for rinse water HCl pickling line 4
I. Project INDIA: ZLD for rinse water HCl pickling line HCl/Chloride ppm < 4300 Phosphate ppm < 1100 Sulphate ppm < 8 Iron as Fe-II ppm < 1300 Zinc as Zn-II ppm < 1100 Lead ppm < 20 Cr6+ ppm < 15 BOD ppm <60 COD ppm <350 Total Suspended Solid ppm <150 Total Dissolved Solids ppm <7800 5
I. Project INDIA: ZLD for rinse water HCl pickling line II. membrane units / concentration I. conventional waste water treatment 6
I. Project INDIA: ZLD for rinse water HCl pickling line 7
I. Project INDIA: ZLD for rinse water HCl pickling line 8
I. Project INDIA: ZLD for rinse water HCl pickling line Ultrafiltration: • design: hollow fiber modules • 3 modules a 60 m² = 180 m² • specific flow ~ 45 – 55 l/m²*h • feed pressure ~ 1.5 bar • back flushing every ½ h for 30 sec. • Chemical Enhanced Backwash (CEB) every 6h for 90 sec. 9
I. Project INDIA: ZLD for rinse water HCl pickling line Reverse Osmosis I: • design: spiral wound module • 2 pressure pipes 8“ x 6 elements a 36 m² = 432 m² • specific flow ~ 13 l/m²*h • maximum feed pressure ~ 30 bar • feed ~ 6.5 g/l NaCl / ~ 10.5 mS/cm • concentrate ~ 20 g/l NaCl / ~ 30 mS/cm • permeate ~ 0.1 g/l / ~ 175 µS/cm • operation with acid dosing to feed • anti scaling dosing • chemical cleaning every 7 – 10 days 10
I. Project INDIA: ZLD for rinse water HCl pickling line Reverse Osmosis II: • design: spiral wound modules • 2 pressure pipes 4“ x 5 elements a 12 m² = 120 m² • specific flow ~ 11 l/m²*h @ 43-48 bar • maximum feed pressure ~ 55 bar • feed ~20 g/l NaCl / ~ 30 mS/cm • concentrate ~ 40 - 45 g/l NaCl / ~ 53-56 mS/cm • permeate ~ 0.2 g/l / ~ 350 µS/cm • chemical cleaning every 7 – 10 days 11
I. Project INDIA: ZLD for rinse water HCl pickling line III. thermal concentration 12
I. Project INDIA: ZLD for rinse water HCl pickling line 13
I. Project INDIA: ZLD for rinse water HCl pickling line Special feature: condensation and heat transfer 14
I. Project INDIA: ZLD for rinse water HCl pickling line 15
I. Project INDIA: ZLD for rinse water HCl pickling line 16
I. Project INDIA: ZLD for rinse water HCl pickling line Summary: • recovery of 85 - 90% of the waste water as high quality fresh water • low amount of final dry by product • pre concentration of sodium salts in 2 step reverse osmosis unit • final thermal concentration in corrosion resistant columns • simple thermal concentration process • in combination low thermal energy consumption only thermal concentration: ~ 0,65 kWh/kg combined UO / thermal process: ~ 0,13 kWh/kg → for rinse water from HCl pickling lines or similar application 17
II: Project China: ZLD for rinse water and spent acid HCl pickling line 18
II. Project China: ZLD for rinse water and spent acid HCl pickling line 19
II. Project China: ZLD for rinse water and spent acid HCl pickling line rinse water spent acid design flow 1.5 0.75 m³ /h HCl/Chloride 23 180 g/l Phosphate 3,25 g/l Iron as Fe-II 7,5 120 g/l Zinc as Zn-II 2,5 g/l NaOH 5 g/l MnO 2 2 g/l KMnO 4 1 g/l 20
II. Project China: ZLD for rinse water and spent acid HCl pickling line 21
Project China: ZLD for rinse water and spent acid HCL pickling line 22
II. Project China: ZLD for rinse water and spent acid HCl pickling line 23
II. Project China: ZLD for rinse water and spent acid HCl pickling line 24
II. Project China: ZLD for rinse water and spent acid HCl pickling line 25
II. Project China: ZLD for rinse water and spent acid HCl pickling line 26
II. Project China: ZLD for rinse water and spent acid HCl pickling line 27
II. Project China: ZLD for rinse water and spent acid HCl pickling line Batch treatment mixer (commissioning): • filling & mixing • 90 kg CaCO 3 • 50 kg cement • dosing concentrate & mixing • 82 l (~ 107 kg) concentrate → total batch time ~ 5 minutes → further optimization & reduction cement of dosing by operator after commisissiong 28
II. Project China: ZLD for rinse water and spent acid HCl pickling line Summary: • ZLD for rinse water and spent acid • recovery of ~ 95% of the waste water as fresh water • thermal concentration in corrosion resistant columns • high volumetric concentration ratio C f,V = 14 - 23 • simple thermal concentration process • heat recovery by heat transfer condensation – evaporation • low investment costs compared to WWTP & HCl - ARP → for rinse water & spent acid from hydrochloric pickling lines or similar application → HCl ARP available? → re use / discharge of residual dry product ??? 29
III. Project Schweden: ARP for spent mixed acid pickling line Bag House Metal oxid Filter Crystalli- Micro- Nano- Evapo- Roaster Belt Filter ration filtration filtration zation Pickling Line Absorp- tion HF/DeNOx Waste Gas 30 Steuler T otal A cid R egeneration STAR
III. Project Schweden: ARP for spent mixed acid pickling line Improvement by Steuler Total Acid Regeneration STAR ◼ free acid separation and metal fluoride concentration in upstream membrane units ◼ crystallization and dewatering of metal fluoride crystalls ◼ low water evaporation in roaster ◼ reduction of natural gas consumption ◼ almost no HNO 3 in metal fluoride filter cake → high HNO 3 recovery ◼ reduction of chemical consumption → reduction of operation costs 31
III. Project Schweden: ARP for spent mixed acid pickling line Technical design data waste acid origin stainless steel strip pickling line metal built up step 1: 135 kg/h step 2: 220 kg/h waste acid flow rate step 1: up to 8,500 l/h step 2: up to 13,500 l/h temperature 55 - 65 °C waste acid components 125 - 250 g/l HNO 3 total 40 - 80 g/l HF total 30 g/l Metals HF recovery > 96% HNO 3 recovery > 92% 32
III. Project Schweden: ARP for spent mixed acid pickling line 33
III. Project Schweden: ARP for spent mixed acid pickling line tank farm microfiltration unit nanofiltration unit 34
III. Project Schweden: ARP for spent mixed acid pickling line evaporation bag house filter top of the roaster vacuum belt filter crystallization / chiller 35
III. Project Schweden: ARP for spent mixed acid pickling line metal fluoride filter cake vacuum belt filter 36
III. Project Schweden: ARP for spent mixed acid pickling line Steuler Roaster: • feed flow up to approx. 700 l/h • diameter 1.550 mm 37
III. Project Schweden: ARP for spent mixed acid pickling line 38
III. Project Schweden: ARP for spent mixed acid pickling line Special features ◼ HF regeneration efficiency HF > 96% / HNO 3 regeneration efficiency > 92% ◼ metal regeneration > 98% with very low fluoride concentration < 0.8% ◼ low energy consumption ~ 1.800 MJ/m³ acid (approx. 60% of common Roaster) ◼ very low waste water flow and nitrate emission ◼ operation at part load with approx. 75 % energy consumption at 60% metal removing ◼ operation with volume reduction (waste acid / regenerated ~ 95%) ◼ extension from 135 kg/h to 220 kg/h metal separation with quite low additional costs ◼ reuse of internal water from chemical pumps and vacuum pump ◼ high requirements for safety, operation and maintenance 39
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