18-06-2011, 10:20 AM
Presented By
Kazi Mahmudul Haque Bhadhon
Md. Tanvir Faisal
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REFRACTORY BRICK INDUSTRY DESIGN
INTRODUCTION
Refractory Bricks are bricks that can withstand high temperature.
A block of refractory ceramic material.
Should not spall under rapid temperature change, and their strength should hold up well during rapid temperature changes.
Dense firebricks are used in applications with extreme mechanical, chemical, or thermal stresses.
In other, less harsh situations, more porous bricks are used.
DIFFERENT TYPES OF REFRACTORIES
Different grades of refractories
Low-duty (Max. Temp. 1750°F, 24-26% alumina)
Medium duty(Max. Temp. 2700°F, 34-38% alumina)
High Duty(Max. Temp. 2850°F, 36–40% alumina)
Super Duty(Max. Temp. 2900°F, 40–44% alumina)
High Super Duty(Max. Temp. 3000°F–3150°F, 40–44% alumina.)
PRODUCT SELECTION
Fireclay Brick.
High Alumina Brick.
Insulating Fireclay Brick.
REASON FOR SELECTION
Applications:
Fire Clay Bricks
For lining Iron blast furnaces
Used in annealing, roasting and reheating furnaces; glass melting furnace and other frequently cooled furnace.
Used in flues, chimney linings, steel casting, pottery, cement and fertilizers industries.
High Alumina Bricks
Used in very high temperature locations, such as, electric arc furnace roof.
Used in making thermal equipment of metallurgy, petroleum, chemical industry, construction materials, machinery etc.
Insulating Bricks
Used in annealing furnaces, forging furnaces, electric arc furnaces and boilers.
WHY SELECT(MARKET)
Fire clay refractory products are used by almost every industry, which has heat processing in the production process. Iron and steel, cement, petrochemicals, sugar, non-ferrous metal, glass and ceramic industries are some of the user industries.
Iron and Steel industries account for 75% of the consumption of refractories. Thus, the demand for refractories is dependent on the growth of iron and steel industries in the country.
GENERAL SHAPE OF THE PRODUCTS
Most bricks are pressed or extruded. Common shapes are straights, arches, wedges, keys, rotary kiln blocks (RKBs) and square-edge tiles.
STANDARD SIZES OF PRODUCTS
The standard refractory brick size is 9 x 4 ½ x2 ½ inches, also known as one brick equivalent (beq).
The different sizes are given below-
Straights—the standard straight is 9×4½×2½ inches or 9×4½×3 inches and available in larger sizes up to 18 inches long, 9 inches wide, and 4½ inches thick.
Square edge tile—This term refers to “big” straights, which comprise 12×12 inches up to 24×12 inches with thickness ranging from 1½ to 3 inches.
Soaps—A term used to describe a half brick in width such as 9×2¼×2½ inches or 9×2¼×3 inches.
Splits—A term used to describe a the thickness of a brick thinner than 2½ inches, i.e., splits come in 1, 1¼, 1½, and 2 inch thicknesses.
Arch—This shape tapers in thickness along the width over its entire length and is used to make sprung or circular barrel arched roofs either 4½ inches or 6 inches in thickness.
Wedge—This shape tapers in thickness along the entire length of the brick and is used to make sprung or circular barrel arches 9, 12 or 13 inches in thickness.
Skew—A shape having a certain taper on one side or end to enable a sprung arch to be built. Four major types are available in both side and end skews that relate to the rise of the arch.
Specification for High Alumina Brick
Al2O3 ≥ 82.5%
Fe2O3 ≤ 2.0%
SiO2 ≤ 11.5%
Bulk density ≥ 2.7 gm/cc
Apparent porosity ≤ 23%
Specification for High Silica Brick
SiO2 ≥ 96%
Fe2O3 ≤ 0.8%
(Al2O3+R2O3) ≤ 0.5%
True density ≤ 2.34 gm/cc
Apparent porosity ≤ 22%
PROCESS LAYOUT
RAW MATERIALS
Bijoypur Clay.
Black clays: bought from Ashulia.
Red clay.
Quartz.
Granular grog.
Feldspar.
Bauxite.
Saw dust.
COMPOSITION OF clays
Bijoypur clay
Al2O3 (28-30%) ; SiO2 (68-70%) ; FeO (Traces)
Black clay
Al2O3 (26-28%) ; SiO2 (70-72%) ; Others.
Red clay
Al2O3 (22-23%) ; SiO2 (75-78%) ; Others.
RAW MATERIALS PROCESSING
Steps Involved in Raw Material Processing
→ Crushing & Grinding
→ Pre-Treatment(optional)
→ Screening
→ Mixing
CRUSHING & GRINDING
Raw materials are ground to obtain proper sizes of materials
Common equipments are various types of crushers, pulverizers, hammer mills, ball mills, pan mills etc.
JAW CRUSHER will be used as
Cost effective
Time efficient
PRE-TREATMENT
Molded firebricks or refractories shrink considerably during firing.
To reduce this shrinkage, the raw materials are generally pre-treated i.e. fired/calcinated at higher temperature for considerable periods of time which bring about the complete mineral conversion and hence stabilizes the material.
The Goal can be achieved by using GROG.
PRE-TREATMENT (CONTD.)
The raw materials for insulating bricks need some additional pre-treatments.
The highly plastic “Black Clay” (or, ‘Ashulia Clay’) is mixed with sawdust and water and kept under shade for about one month which enables it to mix in the highest compactness and with uniform distribution of the sawdust.
SCREENING
Sorting out desired sized materials from a wide size distribution.
Screening of the materials being crushed is necessary so that the required product can be passed on to the brick making machinery and the coarser material returned to the crushers.
Can Be Done By
Screening Net
Shaking Screen Machine
MIXING
Composition of brick is adjusted by blending of different minerals, fluxing/binding agent.
Blending is carried out not only by composition but also by size. The ratio between the course and the fine fractions are maintained to get the desired packing density.
Control of ultimate porosity and strength can be possible.
PUG MILLS
MOULDING
Hand Molding
Dry press process
Uniaxial Pressing Machine
Semi-dry process
Slip casting etc.
DRYING
To minimize shrinkage during firing.
To reduce cracking and distortion.
Can be done by,
Natural Drying
Forced Drying
Flue gas from the Tunnel Kiln.
FIRING
A number of kilns can be used
Tunnel Kiln
Beehive Oven
Hoffmann Kiln
Vertical shaft Kiln
WHY TUNNEL KILN?
Continuous Process
High Production Rate
More Economic
Relatively Fast Process
Machining
Especially for insulating firebricks, the evaporation of volatile matters cause deformation or dimensional changes of the brick. Other type bricks may also require finishing.
For this reason, after firing the bricks are machined to close dimensions possible.
STORAGE
Fired, machined products are stored in shelves in sheds according their type.
The humidity level, temperature, air flow etc. inside the shed should be maintained to exact suitable conditions.
TRANSPORT
Raw Materials Transport
5 Trucks
Products Transport
5 Trucks
