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WHRB boiler for 100 tpd sponge,steam output temperature problem raised from 400degC to 480degC
Sponge Iron units running 300 tpd klin having WHRB to generate steam at 64 ata, 485degC considering gas from klin 72,000 nm3/hr at 9500C, over a period of long running have detoriation of coal and iron ore quality. The total gas generation from klin has reduced for 100 tpd only 18,000 nm3/hrand ABC temperature 8500C.
The ideal 100 tpd klin with good quality coal (GCV 3500Kcal/kg) with less ash below 25%. Gas generation from 100 tpd klin is 24,000nm3/hr , 950oC and steam generated 10.5 tph , 64 ata, 485oC. Accordingly turbine selected 64ata, 4850C and consumption of turbine of steam increases as less 420oC and below turbine trips. In some cases due to low temperature steam and by pass of safety system of turbine which leads to entire rotor blade broken and major shut down of system.
DEVI IRON & STEEL POWER Ltd. Dharsima , Raipur is having combined 3x100 tpd WHRB (common boiler) 30 tph, 4850C. During operation we initially could not attain temperature of 4300C due to coal quality which varies from supplier to supplier and steam generation also low due to less gas volume.
Turbine operation became critical due to less temperature because trip was set 4100C at turbine inlet & vice versa steam consumption increased and generation was low.
To Incease the steam temperature. We have taken following step and success was tremendous.
1. Super heater was placed in pass – 03 in previous design.
2. 1st pass 8500C flue gas temperature water walls, 3rd pass super heater where passing temperature was below 4500C and steam temprature 4300C max.
3. We extended. Super heater of thick S.S heavy gauge horizontal coils in 1st pass.
4. The result we achieved immediately from even two klin at ABC temperature 9000C steam temperature 4800C-4900C .
5. When steam temperature was high even less quantity of steam generation we can safely run the generation. However pressure are controllable.
6. Devi Iron & Power Ltd. Running with grid operator 33 KV.
Note- My experience with WHRB steam generation it is possible to raise the steam temperature with a little modification in WHRB boilers. However basic design of boiler to be studied first and modificatio is possible.
