J ACID PLANT CAPACITY INCREASE

1. J ACID PLANT CAPACITY INCREASE PRESENTER: SIYABONGA MALEVU COMPANY: CHEMICAL INITIATIVES DEPARTMENT: TECHNICAL

2. J PLANT BACKGROUND

3. J PLANT BACKGROUND FULL RATES PRIOR TO CAPACITY INCREASE • Production rate: 500 tons/day of H2SO4 • Air flow rate: 45 000m3/hr • Sulphur rate: 7 tons/hr • Burner SO2 conc.: 10.5% (burner temp of 1000 oC) • Catalyst loading: LP12O for 1st and 2nd pass & LP110 for 3rd & 4th pass • Converter overall conv.: 99.5% • SO2 emission: 350 – 500ppm

4. PRE-PROJECT SIMULATION DATA • Production rate: 547tons/day of H2SO4 • Air Flow rate: 47 500m3/hr • Sulphur rate: 7.4 tons/hr • Burner SO2 conc.: 11% (Burner temp: 1025 oC) • Catalyst loading: LP120:1st&2nd Pass, LP110:3rd pass&VK69: 4th Pass • Overall converter conv.: 99.79% • SO2 emission: 100 – 350ppm

5. CONVERTER MODIFICATION • 3rd pass catalyst loading increased by 18.6% (from 20 350 to 25 000 litres). • The extra 4 650 litres obtained from 4th pass. • 4th pass LP110 catalyst replaced with VK69 catalyst. • 4th pass catalyst loading increased by 26.7 % (from 22 000litres to 30 000litres). • 3rd and 4th pass thermocouples re-allocated to accommodate the increased catalyst bed depths.

6. VK 69 BENEFITS • High surface area ------ high activity • High void fraction ------ low pressure drop • Reduced SO2 emissions • Increased production with low SO2 emission levels • Long lifetime

7. EVALUATION OF CAPACITY OF MAJOR EQUIPMENT Critical investigated areas were: • AIR BLOWER CAPACITY Prior – running at 43 000m3/h at discharge pressure 42 kPa Design max capacity – 47 500 m3/h at 47 kPa discharge pressure Blower curves – 47 500 m3/h at 46.5 kPa discharge pressure Possible by increasing blower vanes angle to maximum Increase power consumption by 4 kW. • SULPHUR BURNER CAPACITY Sulphur consumption – increase from 6.8 ton/h to 7.4 ton/h Consultation with original designers – burner large enough to increase acid plant by 20%. • CONVERTER CAPACITY 3RD Pass maximum catalyst volume: 25 100 litres 4th Pass maximum catalyst volume: 30 300 litres Increase 4th pass pressure drop from 0.5 kPa to 0.79 kPa. • COOLING CAPACITY Burner temperature increased to 1025 0C. 1st Pass Converter temperature decrease from 433 to 430 0C WHB #1 – enough capacity for additional 1.8 ton/h steam generation

8. EVALUATION OF CAPACITY OF MAJOR EQUIPMENT • Drying, Interpass, Final Absorption Towers • Sulphur pump, BFW pump, Acid pumps • Hot and cold heat exchangers • Main Benefits: • Additional 47 ton/day acid production • Additional 43.2 ton/ day steam generation • Payback period: 6 months

9. ECONOMIC EVALUATION • Main Benefits: • Additional 47 ton/day acid production • Additional 43.2 ton/ day steam generation • Payback period: 6 months

11. Prior to implementation: 477 tpd • Target : 547 tpd • After implementation : 533 tpd Failure of maintaining the 4th pass inlet temperature below 405 0C without compromising the desired export steam temperature at the boiler station

13. ACID PLANT 20% UPRATE PHASE II 550 to 600 MTPD EXPORT STEAM TEMPERATURE AIR BLOWER CAPACITY MAIN COOLING TOWER CAPACITY PLANT PRESSURE DROP OPERATE THE BOILER AT MAX PRESSURE REDUCE CONVERTER PRESSURE DROP REDUCING HEAT LOSSES @ EXPORT LINE REDUCE IAT & FAT PRESSURE DROP GENERATE ELECTRICITY FROM STEAM