Materials of Construction - Sulphur Furnace
November 8, 2002

Introduction Shell Refractory Brick Lining Insulating Brick Fire Brick Castable Standards

Associated Links Sulphur Burning Sulphur Furnace Sulphur Systems

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Introduction

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).

Shell

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.  The selection of material will be a function of maximum operating temperature of the shell, design pressure and availability and cost of the material.

If the shell can see extreme low temperatures an impact tested steel may be required.

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Refractory Brick Lining    

The brick lining serves two purposes:

• reduce temperature at shell

• protect shell from corrosive gases and liquids

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. 

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Insulating Brick

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:

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Fire Brick

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.

Class	Type	PCE (min)	Modulus of Rupture (MPa/psi) (min)	Alumina Content (% Al2O3)
Fireclay Brick
Super-duty	Regular	33	4.14 / 600
	Spall Resistant	33	4.14 / 600
	Slag Resistant	33	6.89 / 1000
High-duty	Regular	31ln$
	Spall Resistant	31ln$	3.45 / 500
	Slag Resistant	31ln$	8.27 / 1200
Semi-silica			2.07 / 300
Medium-duty			3.45 / 500
Low-duty			4.14 / 600
High-Alumina Brick
50		34		50 ± 2.5
60		35		60 ± 2.5
70		36		70 ± 2.5
80		37		80 ± 2.5
85				85 ± 2.0
90				90 ± 2.0
99				97 (min)

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.

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Castable

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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Standards

ASTM C16	Test Method for Load Testing Refractory Brick at High Temperatures
ASTM C20	Standard Test Methods for Apparent Porosity, Water Absorption, Apparent Specific Gravity, and Bulk Density of Burned Refractory Brick and Shapes by Boiling Water
ASTM C24	Test Method for Pyrometric Cone Equivalent (PCE) of Fireclay and High-Alumina Refractory Materials
ASTM C27	Standard Classification of Fireclay and High-Alumina Refractory Brick
ASTM C113	Test Method for Reheat Change of Refractory Brick
ASTM C133	Test Methods for Cold Crushing Strength and Modulus of Rupture of Refractories
ASTM C134	Standard Test Methods for Size, Dimensional Measurements, and Bulk Density of Refractory Brick and Insulating Firebrick
ASTM C155	Standard Classification of Insulating Firebrick
ASTM C210	Standard Test Methods for Reheat Change or Insulating Firebrick
ASTM C800	Standard Test Methods for Apparent Porosity, Water Absorption, Apparent Specific Gravity, and Bulk Density of Burned Refractory Brick and Shapes by Boiling Water
ASTM C914	Standard Test Method for Bulk Density and Volume of Solid Refractories by Wax Immersion