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dhayanandhan
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Engineering Fields - Mechanical Engineering - New Member

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Location: CHENNAI, TAMIL NADU, INDIA.
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Short Fall of Boiler Capacity

09/08/2014 1:53 PM

Dear CR4 Members,

The RESIDUE after crushing Sugar Cane and removal of juice, is called BAGGASSE with 50% Moisture, directly sent to Boilers for burning as Fuel and generate Steam, produce Power in a back-pressure turbine, the exhaust steam from Turbine is sent to Process for boiling the juice and make sugar.

The Baggasse contains high percentage of VOLATILE MATTER and burns with a long flame. Baggasse is rich in Oxygen to the extent 41% and excess air used is 30% to 35 % and the Gross Calorific Value is 2000 KCal./Kg. of Baggasse. Steam to Baggasse Ratio is 2.2 to 2.3

If the same Boiler is suitably designed for coal burning with conveyors etc., and installed to burn coal (with Gross Calorific Value of 5400 K.Cal/Kg. of coal) the Boiler Capacity falls to 80% of the capacity, to that of Baggasse burning. Excess air used 20% to 22%. Steam to Coal Ratio is 5.5 to 5.6.

Inspite of Higher Calorific Value for coal than Bagasse and Lesser Excess Air Percent, for coal, how and why the capacity of the Boiler is falling when we switch over to Coal.?

DHAYANANHDAN.S
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Crabtree
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#1

Re: Short Fall of Boiler Capacity

09/08/2014 2:19 PM

Because it BURNS SLOWER.

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bigg
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#2

Re: Short Fall of Boiler Capacity

09/08/2014 3:44 PM

With the high moisture and excess air, I'm surprised you don't lose more capacity. I think you would get better results if you could dry the baggasse first.
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tcmtech
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Location: South of Minot North Dakota
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#3
In reply to #2

Re: Short Fall of Boiler Capacity

09/08/2014 4:25 PM

Maybe thats what they want to use the coal fired boiler for?

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Unredundant
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#4

Re: Short Fall of Boiler Capacity

09/08/2014 5:01 PM

Is there residue coating the tubes?

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phoenix911
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#7
In reply to #4

Re: Short Fall of Boiler Capacity

09/09/2014 11:13 PM

Fouling

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Crabtree
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#5

Re: Short Fall of Boiler Capacity

09/08/2014 5:58 PM

You need to DITCH THE CONVEYORS. You need a facility to PULVERISE THE COAL, together with a REVISED BURNER ARRANGEMENT that handles the coal as a DUST and blows it in with AIR. Otherwise you're KNACKERED.

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phoenix911
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#8
In reply to #5

Re: Short Fall of Boiler Capacity

09/09/2014 11:15 PM

They are difficult to start, but after they are lit it's pretty efficient.

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Unredundant
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#9
In reply to #5

Re: Short Fall of Boiler Capacity

09/10/2014 9:16 AM

How is the pilot and proven flame managed? Darn! forgot to Google it......

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ormondotvos
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#6

Re: Short Fall of Boiler Capacity

09/09/2014 1:15 AM

I think the key issue here is the high water content of the bagasse. Is there some way you can use waste heat to partially dry the bagasse? Maybe a wide flat conveyor belt to nowhere and back? Isn't it usually very hot where sugar cane grows? It would seem that most of your burn calories are producing steam outside the boiler.

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diagon123
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#10

Re: Short Fall of Boiler Capacity

09/15/2014 3:14 AM

The effective surface area for combustion is higher in bagasse ( because of its thread like structure ) than coal. The size of coal will be a crucial factor when you want to burn coals.

As suggested Pulverizer is necessary. A more efficient way will be to produce water gas or coal gas.

drying the bagasse will help again in improving efficiency... the flue gas can be used for drying.

Why not use bagasse for other purposes like...you sell it to Palm oil industry for the reduction of peroxide value ?

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bigg (1); Crabtree (2); diagon123 (1); ormondotvos (1); phoenix911 (2); tcmtech (1); Unredundant (2)

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