Case Study- for WHRB - DEVI IRON & STEEL POWER Ltd Dharsima , Raipur

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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 , 950^oC and steam generated 10.5 tph , 64 ata, 485^oC. Accordingly  turbine selected 64ata, 485⁰C and consumption of turbine of steam increases as less 420^oC 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.       1^st pass 850⁰C flue gas temperature water walls, 3^rd 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 1^st 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.