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.

New Concept of Waste Heat Steam Generation

Raipur Power Gen has developed a New concept of WHRB( Waste Heat Recovery Boiler) from sponge Iron Kiln.

In General Sponge Iron Kiln we have for example 100tpd( tones per day ) that generates 24,000 cum/hr hot gases at 950degC to be used for WHRB to produce steam of 10 tph (tones per hour ) , 64ata, 485degC with each boiler attached with 100 tpd Sponge Iron Kiln .
We know in this we would need 3 WHRB’s would be needed under 3 separate kiln.
In the new concept that RPG has developed we have combined 3X100 tpd sponge from Hot Gas duct in one WHRB (waste heat recovery boiler) having isolation slide gate (water cooled ) at inlet of hot duct on riser side.
This slide valve can withstand temperature upto 1600degC and by valve controlling we can control the pressure inside the kiln if necessary.

After combining all the three duct’s in one WHRB we can get waste gas of 3X24000cum/hr & corresponding steam generation 30 tph (tonne per hour) for running steam turbine generator. And now if one kiln is under shutdown we are providing pulverized coal nozzle to generate more gas vice versa we would get more steam from waste heat boiler. The coal nozzles and slide gates valves are imported.

The Operation of this kind of a project under my guidance will begin from JUNE 09.
For which boilers are under erecting stage.

The total design and concept has been verified by boiler design experts.
We sincerely and firmly believe and wish that we will achieve success in our developmental project and in future times this can be used with coal dust in plant for recycle.

D.Mukherjee
9827172172