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| Sulphuric Acid on the WebTM | Technology Manual | DKL Engineering, Inc. |
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Knowledge for
the Sulphuric Acid Industry Introduction
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A sulphur furnace is exposed to high temperatures from the combustion of sulphur to sulphur dioxide. The materials of construction must be capable of withstanding temperatures as high as 1200ºC (2192ºF). The furnace shell is generally carbon steel. The specific grade of steel will vary depending on
the expected operating shell temperature (i.e. Cold Shell or Hot Shell design). For cold shell design A36 steel will be adequate. For hot shell designs A515 Gr. 70, A516 Gr. 70 or
A285 Gr. C may be used. If the shell can see extreme low temperatures an impact
tested steel may be required. The brick lining serves two purposes:
The above is achieved by using both refractory brick and
insulating brick. Multiple layers are typical
for mechanical reasons and to eliminate a direct leak path to the shell. For most furnaces a 343 mm (13½”) layer of
refractory (insulating and fire brick) is adequate to maintain shell temperatures at
acceptable levels. When the furnace operating
temperature is higher, increased thickness (457 mm (18”)) of refractory brick will be
necessary. Refractory brick comes in standard brick sizes regardless
of the supplier. Standard brick dimensions
are 9” x 4½” x 2½” and 9” x 4½” x 3”. Other sizes and shapes are available as standard. Insulating brick is generally applied between the steel shell and the exposed layer of fire brick. As its name implies its purpose is to reduce heat transfer and insulate the shell from the hot process gases. Insulating brick should conform to ASTM C155 – Standard Classification of Insulating Firebrick which covers heat insulating materials known as insulating firebrick. Insulating bricks are classed according to their bulk density and the behaviour in the reheat change test conducted at the specified temperature. Eight groupings are defined in the specification:
Fire brick provides protection from the high operating temperatures in the furnace and are more resistant to mechanical damage and chemical attack than insulating brick. Fire bricks are composed of various combinations of alumina and silica containing materials. The chemical composition can vary from almost 100% alumina and little silica to 100% silica and little alumina. Fire bricks are classified into two broad categories; fireclay and high-alumina bricks. Fireclay brick are classified based on physical propeties while high-alumina bricks are classified primarily on alumina content.
Typically, a super duty (a fireclay refractory having an Orton pyrometric cone
equivalent above 33) fire
brick is used containing 45 wt% or greater alumina content. Bulk density of refractory materials ranges from 2.19 to 2.24 g/cm³. Castable refractory may be used in parts of the sulphur
furnace design. Areas where castable
refractory may be used are the front of the furnace where the sulphur gun and nozzles are
located, manways, sightglasses, etc. The
castable refractory is held in place by anchors which are resistant welded to the shell.
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2006, 2007, 2008 DKL
Engineering, Inc., All Rights Reserved |
