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Anonymous Poster

Chimney Height

04/12/2008 1:36 AM

Hi,

I am project engineer of Rolling Mill that will produce special stainless steel & alloy steel. The reheating furnace uses light diesel oil of CV 9800 Kcal/Nm3. It has chimney of 60 meter height. I think, it is too high. Consequently project cost will goes up. Can it possible to reduce height of chimney & by how much?
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Hendrik
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#1

Re: Chimney Height

04/12/2008 2:37 AM

The hight of the chimney may be prescribed by law. first check there.

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TVP45
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#2

Re: Chimney Height

04/12/2008 5:14 AM

How does chimney height affect the project cost if you already have it built? Is this natural draft?

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Milo
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#3
In reply to #2

Re: Chimney Height

04/12/2008 11:02 PM

I suspect that your taking the verb tense literally is the root cause of your conjecture.

Enjoy your evening.

milo

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TVP45
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#4
In reply to #3

Re: Chimney Height

04/13/2008 5:37 AM

Yes. Quite so. The question makes more sense if I read it in future tense.

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ratnagiri
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Join Date: Mar 2007
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#5

Re: Chimney Height

04/13/2008 9:26 AM

I think your question is why your company has spent so much money on such a tall chimney.

Reasons could be-

1) The local authority regulations.The chimney does not eliminate the pollutants but dilutes by dispersing the same in large area.The dispersion area is proportional to the height.% Sulphur content in fuel normally decides the height.

2) Natural draft requirement.
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Anonymous Poster
#6

Re: Chimney Height

04/13/2008 5:55 PM

Since the chimney draft is basically determined by the density of the discharge gases and the stack height, and since the gas density is nominally a function of temperature, could you insulate the chimney to reduce the average density and increase the draft?
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ratnagiri
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#7

Re: Chimney Height

04/13/2008 11:02 PM

Complete data is required to evaluate chimney height.IF you have installed all essential heat recovery system then flue gas temp will have less influence on chimney height.Insulation is to protect the workmen & steel stack from high temp also to check the temp does not go below acid dew pt .
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ahmedalqassab
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Join Date: Jan 2008
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#8

Re: Chimney Height

04/14/2008 12:52 AM

[edit] Estimating Stack Effect Ventilation

The natural ventilation flow rate can be estimated with this equation:

U.S. customary units:

where:

QS

= Stack vent airflow rate,

ft³/s

A

= cross-sectional area of opening,

ft² (assumes equal area for inlet and outlet)

Cd

= Discharge coefficient for opening

g

=

gravitational acceleration, 32.17 ft/s²

Hd

= Height from midpoint of lower opening to neutral pressure level (NPL),

ft

NPL

= location/s in the building envelope with no pressure difference between inside and outside (ASHRAE 2001, p.26.11)

TI

= Average indoor temperature between the inlet and outlet,

°R

TO

= Outdoor temperature, °R

SI units:

where:

QS

= Stack vent airflow rate,

m³/s

A

= cross-sectional area of opening,

m² (assumes equal area for inlet and outlet)

Cd

= Discharge coefficient for opening

g

=

gravitational acceleration, 9.807 m/s²

Hd

= Height from midpoint of lower opening to neutral pressure level (NPL),

m

NPL

= location/s in the building envelope with no pressure difference between inside and outside (ASHRAE 2001, p.26.11)

TI

= Average indoor temperature between the inlet and outlet,

K

TO

= Outdoor temperature, K

By using forced ventilation yes you can do so, with authority approval.

for more information please visit:en.wikipedia.org/wiki/Natural_ventilation
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ahmedalqassab (1); Anonymous Poster (1); Hendrik (1); Milo (1); ratnagiri (2); TVP45 (2)

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