aluminabricks, Author at RS Kiln Refractory Bricks

High Zirconia Blocks Description

High zirconia blocks are also called pure zircon bricks, their principle crystalline phase is zircon. Raw material of high zirconia block is zircon sand, with about 90% of zircon by weight. Zircon fine ore has very small granularity, so is not suitable to produce refractory bricks directly. To make coarse granule pure zircon firebricks, zircon fine ore should be pre-sintered or fused into zircon clinker. After sintering, the density of zircon fine ore is increased, bulk density can reach to 3.5g/cm3.

High Zirconia Blocks Characteristics

The weight percent of ZrO2 in pure zircon refractory is about 65%. High zirconia block is almost completely consisted of zircon crystals, only a little amount of glass phase and free ZrO2 appears in it. The true density of high zirconia blocks is about 4.55g/cm3, max. 4.62g/cm3. Ordinary zirconia block’s bulk density is between 3.6~3.8g/cm3, apparent porosity is higher than 13%. Dense zirconia brick’s bulk density is between 3.8~4.0g/cm3, apparent porosity is about 5%. High dense zirconia brick’s bulk density is larger than 4.0g/cm3, apparent porosity is less than 1.0%.

High zirconia blocks have very high viscosity even in high temperature, so its refractoriness is high, usually higher than 1825℃. The cold crushing strength of high zirconia bricks is between 100~430Mpa, modulus of rupture can reach to 17.8~76.3Mpa, refractoriness under load(RUL) is higher than 1650℃. With the reduce of mineralizer quantity and the increasement of sintering temperature, RUL can reach to 1750℃. So high zirconia bricks is a high grade firebricks which can resist high temperature load action and mechanical abrasion.

Zircon has low thermal expansion rate, so high temperature sintered zirconia blocks or fused cast zirconia blocks has good volume stability. From room temperature to 1400℃, its thermal expansion rate is only 0.5%. Refiring for 2 hours at 1500℃, residual shrinkage rate is only 0.04%~0.20%.

High dense zircon refractory will have lower thermal shock resistance if there is no corase granules. But if it is composed of multi-granularity particles, thermal shock resistance will be significantly improved.

High zirconia blocks have good resistance to molten metals & molten slag corrosion and permeation. High dense zirconia refractory has more better performance, for example, the extent of basic molten slag corrosion is only 1/3 of mullite refractory.

Fused high zirconia blocks have the characteristics of high corrosion resistance, low foaming rate and stone rate, almost no pollution to the glass liquid.

High Zirconia Blocks Physiochemical Index

Item			RS-G88	RS-G95
Chemical Composition %	ZrO2	≥	89	93.6
	SiO2	≤	9	5.3
	Al2O3	≤	1	1
	Na2O	≤	0.05	0.51
	Others	≤	1.6	1
Physical Properties	Cold Crushing Strength (MPa)	≥	400	400
	True Density (g/cm³)	Typical	5.1	5.3
	Liner Thermal Expansion (%)	1000℃	0.65	0.7
	Liner Thermal Expansion (%)	1500℃	0.1	0.3

High Zirconia Blocks Application

Zircon refractory are mainly used in continuous casting ladle inner lining and other parts where suffers severe molten slag corrosion. High zirconia blocks are also used for the masonry of copper and aluminum smelting furnaces casting nozzles. Besides, high zirconia blocks can also be used in glass kilns, where contacts with glass liquid directly and upper structure, as well as separation bricks between fused cast zirconia corundum bricks and silica bricks. Fused high zirconia blocks are suitable for various glass furnaces, especially high quality glass furnaces and special glass furnaces, such as glass bath wall, throat, electrode bricks and so on.

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Dec 24 2018

Sialon Bonded Sic Refractories

Sialon Bonded Sic Refractories Description

Sialon bonded SiC refractories are normally β-Sialon bonded SiC material. Sialon is the general name of compounds consisted of Si, Al, O, N and other elements. β-Sialon has many similar properties of Si3N4 based ceramic material, such as high rigidity, excellent mechanical performance, corrosion resistance, thermal shock resistance, low linear expansion coefficient. Its thermal conductivity is lower than β-Si3N4, but oxidization resistance is better than β-Si3N4, as well as better corrosion resistance to Al, Fe and Zn molten liquid and alkali.

Sialon bonded SiC bricks are mainly used as inner lining of blast furnace bosh or furnace belly. It is regarded as the second generation of SiC bricks used for blast furnaces. The principle crystalline phase of Sialon bonded SiC material is SiC, secondary phase is β-Sialon. Sialon bonded SiC bricks have relatively more Al2O3 compared with Si3N4 bonded SiC bricks.

For blast furnace SiC refractory, SiC content is usually between 70%~80%. With the SiC content, Sialon bonded SiC refractory has slightly higher linear expansion coefficient than Si3N4 bonded SiC refractory, while slightly lower thermal conductivity.

Sialon Bonded Sic Refractories Characteristics

Sialon bonded SiC refractory has very excellent high temperature and high temperature mechanical performances, most Sialon bonded SiC refractory’s 1400℃ modulus of rupture(MOR) is higher than cold MOR.

Sialon bonded SiC refractory also has excellent alkali corrosion resistance. Its alkali corrosion resistance is significantly better than Si3N4 bonded SiC refractory, which makes it more suitale to be used in places of blast furnace where have severe alkali corrosion.

Sialon bonded SiC has excellent oxidization resistance.

Sialon bonded SiC has excellent thermal shock resistance.

Sialon bonded SiC has excellent blast furance slag corrosion resistance.

Generally speaking, compared with Si3N4 bonded SiC material, Sialon bonded SiC has better basic slag corrosion resistance, iron, aluminum and other molten metal corrosion resistance.

Sialon Bonded Sic Refractory Application

Sialon bonded SiC products have been applied in many large scale blast furnaces, molten reduction iron smelting furances (COREX furnace lining, where has severe corrosion damage). Sialon bonded SiC are also used in nonferrous metals industry, such as zinc smelting, aluminum smelting and so on.

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Dec 24 2018

The Application Of Silicon Carbide Refractories

Silicon Carbide Refractory Description

Due to the excellent high temperature performances of silicon carbide refractory, they are widely used in steel industry, nonferrous metals industry, petrol industry, power plant, chemical industry and so on.

The Advantages of Silicon Carbide Refractory

High mechanical strength.

Good thermal conductivity.

Excellent thermal shock resistance and abrasion resistance.

Good slag corrosion resistance and alkali corrosion resistance.

Excellent oxidization resistance.

Good erosion resistance to some molten metals.

SiC refractories applications

Silicon Carbide Refractory Used In Steel Industry

Si3N4 and Sialon bonded SiC & corundum SiC composite refractories are mainly used in steel industry. For example, the lower part of blast furnace bosh, belly, tuyere combination bricks, tuyere sleeve, iron runner, cupola inner lining, coke oven head, heating furnace sliding rail, converter and electric furnace tapping hole.

Silicon Carbide Refractory Used In Nonferrous Metals Industry

Oxide bonded SiC, Si3N4, Sialon, Si2N2O bonded SiC refractories are widely used in nonferrous metals ( aluminum, zinc and copper, etc) smelting. Aluminum electrolysis cell inner lining, aluminum refinery furnace lining, zinc retort vessel lining, zinc fine distillation tower tray, ISP furnace condenser and rotor, fine copper smelting stand furnace, ASARCO furnace bosh lower part working lining and holding furnace inner lining, molten metals tube, metal smelting crucible, iron powder reduction smelting sagger, aluminum and zinc liquid temperature testing thermocouple protection tube, aluminum casting ceramic raiser tube and so on.

In Ceramics Industry

Oxide bonded SiC, Si3N4 and Si2N2O bonded SiC refractoryies can be used as muffle board and kiln furniture of ceramics kilns, high temperature burning nozzle, glass annealing furnace lining, ceramic sintering furnace lining, muffle furnace inner lining, rotary cement kiln clinker cooler, radiation heating tube, cyclone separator inner lining, etc.

Silicon Carbide Refractory Used In Metallurgy

The protective coating tube of radioactive pyrometer, thermocouple pyrometer and pyrophotometer. The blades of ore selecting stirrer. Sand pump inner lining and swirler nozzle.

Silicon Carbide Refractory Used In Chemistry

Fertilizer nitriding furnace inner lining, petrol vaporizer, desulfurization furnace and organic scrap incinerator inner lining, heat exchanger and so on.

Silicon Carbide Refractory Used In Chemical Fiber Industry

Sand furnace inner lining.

Silicon Carbide Refractory Used Petroleum Industry

Spray nozzle, encapsulation element, valve plates and so on.

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Aluminum Industry Refractory

Dec 24 2018

Alumina Rotary Kiln Refractory

Aluminum Smelting Industry Description

The world’s annual aluminum output takes the top position among nonferrous metals production, far larger than other nonferrous metals. Refractory material consumption of aluminum industry is much more than the total consumption of copper, lead and zinc smelting. The production of aluminum including 2 steps, first, produces alumina from bauxite by wet method, second, uses industrial alumina as raw material, adopts molten salt electrolytic process to produce aluminum. High temperature kilns used for aluminum production are rotary kiln, molten salt electrolytic tank, aluminum smelting furnaces, etc.

Refractory material consumption of industrial aluminum smelting furnaces is large, that’s because, during producing Al2O3, basic material will have very severe corrosion to alumina rotary kiln refractory material. When smelting aluminum, even the temperature is relatively low, aluminum liquid has very strong permeability, once it permeates into firebricks, it will react with SiO2 and reduces Si from the firebricks, which will destroy their structure and cause the looseness, spalling and damage of furnace lining.

So SiO2 containing refractory materials are also not suitable for the masonry of aluminum smelting equipments. High alumina bricks and carbon refractories are usually used for ordinary aluminum industry furnaces.

Alumina Rotary Kiln Description

Rotary kiln is thermal equipment for the sintering of alumina clinker. During manufacturing alumina, alumina bauxite, pure alkali and lime are proportionally loaded into rotary kiln, calcined at 1200~1300℃, the calcined bauxite clinker needs to be further processed to make Al(OH)3. After sintering in 1200℃ rotary kiln, Al2O3 are produced by Al(OH)3.

The sintering process are: high temperature flame and the raw material reversely move in the rotary kiln. Lime and bauxite raw material pulp(contains 40% water) or Al(OH)3(contains 12%~18% water) is loaded form kiln tail. After low temperature drying and dehydration, heating and high temperature sintering, calcined clinker will be unloaded from kiln head, while high temperature gas flows from kiln head to tail. So the kiln can be divided into preheating zone and high temperature sintering zone. To avoid pulp material adhering to kiln lining during sintering and to strengthen heat exchange efficiency, chains are set between refractory material brickwork, when kiln body is in rotary motion, the chains will continuously strike raw materials and lining bricks, which will affluence the service life of kiln lining.

Alumina Rotary Kiln Refractories Properties

The rotary kiln body used for alumina production is steel board welded cylinder, inner lining is constructed by refractories. The working environment of refractory materials are harsh, so they should have these characteristics: strong alkaline corrosion resistance, can continuously work at 1200~1300℃ high temperature and won’t damage, can resist material erosion and impaction, can resist the souring of high temperature air current.

Alumina Rotary Kiln Refractories Category

Reractories used in rotary kiln are mainly high alumina bricks and magnesia bricks. Low temperature drying kiln usually adopts fireclay bricks as inner lining refractory. At sintering zone, there is often an insulating lining between kiln wall and firebricks inner lining, which is often built by diatomite bricks, ceramsite bricks or refractory fiber felts.

Item	Kiln name	Refractory material
Sintering zone(1200~1300℃)	Alumina clinker sintering kiln, aluminum hydroxide calcination kiln	Low calcium aluminate bonded refractory concrete, phosphate bonded high alumina bricks, high alumina bricks, fireclay bricks
Cooling zone	Alumina clinker sintering kiln, aluminum hydroxide calcination kiln	phosphate bonded high alumina bricks, fireclay bricks

Alumina Rotary Kiln Unshaped Refractories

Currently, unshaped refractories are popularly used in aluminum industry. Rotary kiln inlet where constantly suffers materials high temperature abrasion and thermal shock stress, is vulnerable to deformation damage. At alumina clinker sintering kiln transition zone, the temperature is between 400℃~1000℃, alkaline corrosion and mechanical damage are severe, the inner lining often spalls or falls off. So steel fiber castable which has good abrasion resistance is are usually used in rotary kiln.

Item		GJZL-40	GJZL-45	GJZL-70
Al2O3 % ≥		40	45	70
CaO %		/	≤2.5	≤2.1
Refractoriness ℃		1690	1710	≥1790
Working temperature ℃		1250	1300	1450
Fastness to alkali		I	I	II
Bulk density g/cm3	1200℃,3h	1.80	2.30	2.57
Linear change rate %	1200℃,3h	-0.5	-0.3	-0.2
Cold crushing strength Mpa	1200℃,3h	30	50	70
Modulus of rupture Mpa	1200℃,3h	8	9	10
Characteristics		Base resistance, abrasion resistance, thermal shock resistance, energy saving	Alkali resistance, abrasion resistance, spalling resistance, thermal shock resistance	Alkali resistance, high strength, spalling resistance, thermal shock resistance
Applications		Transition zone, preheating zone, kiln hoop	Kiln inlet, preheating zone, chains zone	Decomposition zone, kiln inlet, cooling zone feeding chamber, cooler.

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Aluminum Industry Refractory

Dec 20 2018

Alumina Roasting Furnace Refractories

Alumina Roasting Furnace Refractories Description

The roasting of aluminum hydroxide is the last procedure of alumina production. Its main purposes are drying adhered water and crystallization water in aluminum hydroxide and transforming some γ-alumina into α-alumina. Most alumina manufacturer in China have totally or partly adopted fluidized roasting equipments. Fluidized roasting equipments are classified into fluidized flash roasting furnace, circulating fluidized roasting furnace and suspension roasting furnace. Refractories for these 3 types of roasting furnaces are not the same, but large quantity of unshaped refractory( plastic refractory and refractory castable) are used, more specifically, 50%~70% of refractory consumption is unshaped refractory.

Alumina gas suspension roasting furnace is the specialized equipment for aluminum hydroxide roasting. The craft and automation level are both very high, roasting process takes place at high temperature furnace body ( 1200℃) and high speed atmosphere. The processed alumina has high rigidity, good flowability, meanwhile, there are strict quality standard on alumina products, any mixing of impurity can directly affect the product performance. So the refractory materials used in alumina gas suspension roasting furnace should have the following characteristics: high refractoriness, good abrasion resistance, high strength, good thermal stability, good integrity, good tightness.

Alumina Gas Suspension Roasting Furnace Refractory

Item		SLH-1	SLH-2	SLH-3	SLH-4
Al2O3 % ≥		45	65	65	45
Refractoriness ℃		1710	1770	1730	1690
Working temperature ℃		1100	1300	1300	1100
Suggested quantity t/m3		2.50	2.60	3.30	3.25
Bulk density g/cm3	1200℃,3h	/	2.30	2.30	/
Linear change rate %	1200℃,3h	/	±0.3	±0.3	/
Cold crushing strength Mpa	1200℃,3h	/	90	60	/
Modulus of rupture Mpa	1200℃,3h	/	14	8	/
Characteristics		Good volume stability, high low & middle temperature strength, scouring resistance, abrasion resistance, thermal shock resistance		Strong adhesion ability, good volume stability, thermal shock resistance, scouring resistance, high low & middle temp. strength
Applications		The casting of low & middle temperature lining	The casting of high temperature lining	The gunning and coating of high temperature lining and low workability parts	The gunning and coating of low &middle temperature lining and low workability parts

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Dec 20 2018

Wear Resistant Firebrick

Wear Resistant Firebricks Description

High strength wear resistant firebricks, or also called abrasion resistant firebricks are shaped refractory materials. Refractory bricks has standard sizes and can be processed as per required dimensions during construction. High strength wear resistant refractory bricks have been very popular in recent years. Abrasion resistant firebricks are usually made by corundum, silicon carbide or other abrasion resistant materials, and processed by special crafts. Wear resistant firebricks have high mechanical strength, high density, good abrasion resistance and so on. Abrasion resistant firebricks are widely used in various kinds of industrial furnaces and kilns, such as high temperature zone, strong mechanical abrasion zone and so on. Among them, silicon nitride bonded silicon carbide bricks has the best wear resistance (room temperature wear resistance is about 1.8cm3).

Wear Resistant Firebricks Characteristics

Strong wear resistance and good eolation resistance, ideal for strong abrasion area.
The thermal conductivity is good because of pores in refractory brick. Under the unit temperature gradient, the unit heat flow rate through the material is related to the porosity.

3, good slag resistance, can resist high temperatures slag erosion and corrosion.

High-strength wear-resistant firebricks have good impact resistance, high strength and long service life.

Wear Resistant Firebricks Physiochemical Index

Item	RSNM-A	RSNM-80	RSNM-75	RSNM-70
Al2O3 % ≥	5.0	80	75	70
SiO2% ≤	/	15	20	25
Bulk density g/cm3 ≥	2.65	2.90	2.80	2.70
Cold crushing strength Mpa ≥	150	100	85	72
Modulus of rupture Mpa ≥	45	15	13	11
Refractoriness ℃	1820	1790	1790	1790
Refractoriness under load ℃（0.2Mpa）	1580	1550	1530	1500
Thermal conductivity w/m·k (350℃) ≤	16.0(1000℃)	1.49	1.49	1.49
Thermal shock resistance / times (1000℃, water cooling)	/	20	20	20
Wear resistant cm3	2.5	5.8	8.3	9.6

Wear Resistant Firebricks Applications

Wear-resistant refractory bricks are mainly used for circulating fluidized bed boilers, boiling furnaces and other industrial furnaces. In the past two decades, with the popularization and application of industrial furnaces such as circulating fluidized bed boilers and boiling furnaces, high requirements have been placed on the wear resistance of refractory materials. Traditional refractory materials, such as clay bricks and ordinary high-aluminum bricks, could not meet service life demand. For example, the service life of a typical clay brick in a serious abrasion part of the circulating fluidized bed is only about 3 to 6 months. So wear-resistant refractory bricks are developed, their wear resistance are far better than that of ordinary refractory bricks. Wear resistant firebricks’ service life is between 1 and 2 years.

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Dec 20 2018

Silicon Carbide Bricks

Silicon carbide bricks are high grade refractory material, its main chemical composition is SiC. Silicon Carbide Fire Bricks have both normal temperature and high temperature mechanical strength, good thermal conductivity, small linear change rate, excellent thermal shock resistance, excellent high temperature abrasion resistance and fairly good chemical corrosion resistance. The Fire Bricks in RS Refractory Manufacturer are popularly used in steel industry, nonferrous metal industry, chemical industry, power plants, ceramics industry and so on.

Silicon Carbide Bricks Classification

Silicon carbide bricks can be divided into different categories based on SiC content, binder types and quantity. According to binder types, SiC bricks can be divided into:

Oxide bonded SiC bricks. The bonding phase is Al2O3-SiO2 series silicate, including clay bonded silicon carbide brick, mullite bonded silicon carbide brick and silica bonded SiC brick.
Nitride bonded silicon carbide brick. The bonding phases are Si3N4, Si2N2O, Sialon and other covalance compounds.
Self bonded SiC bricks. Including β-SiC bonded SiC bricks and re-crystallization SiC bricks.
Siliconizing reaction sintered SiC bricks. SiC and free Si consisted engineering ceramics material.

Normally, SiC products with less than 50% SiC are called semi SiC refractory, including clinker SiC refractory, high alumina SiC refractory, zircon SiC refractory, mullite SiC refractory and Corundum SiC refractory, etc.

Oxide Bonded Silicon Carbide Brick

The mineral phases of oxide bonded silicon carbide bricks are quartz, mullite and silicate glass phase. Based on the difference of bonding phases, oxide bonded SiC bricks can be divided into SiO2 bonded SiC bricks, mullite bonded SiC bricks and clay bonded SiC bricks.

Clay Bonded Silicon Carbide Brick

Clay bonded silicon carbide bricks contain 50%~90% SiC, binding material is binding clay, usually added in sillimanite, andalusite, kyanite and other mineral fine powder. The sintering temperature is between 1350~1450℃. The quantity and types of binding material can directly affect the performance of clay bonded SiC bricks. With the increase of clay content, oxidization resistance is improved, but thermal conductivity, refractoriness under load temperature, thermal shock resistance and high temperature strength will all decrease.

Clay bonded SiC refractory are mainly used as muffle boards of various kinds of industrial kilns and furnaces, ceramic kiln furniture ( refractory slab, sagger and so on). But due to the clay bonding phase in SiC refractory, Clay bonded SiC refractory high temperature performance is greatly affected.

Mullite Bonded Silicon Carbide Brick

Mullite bonded silicon carbide bricks developed on basis of clay bonded SiC refractory. The bonding raw material are high purity Al2O3 and SiO2 micro powder or fine powder, sometimes sillimanite, andalusite and kyanite fine powders are also added. The bonging phase are mainly mullite, with low glass phase. In mullite bonded SiC bricks, SiC content is between 65%~85%, sintering temperature is between 1350~1500℃. Mullite bonded SiC bricks have significantly better high temperature performance than clay bonded SiC bricks. Mullite bonded SiC bricks are widely used in ceramic industry, nonferrous metals industry, machinery industry and so on.

Silica Bonded Silicon Carbide Brick

SiO2 bonded SiC bricks has far better high temperature performance than clay bonded SiC refractory, high temperature modulus of rupture is higher than mullite bonded SiC refractory. Silica bonded SiC bricks are mainly used as kiln furniture.

Oxide Bonded Silicon Carbide Brick Specification

Item	Clay bonded SiC refractory	Mullite bonded SiC refractory	SiO2 bonded SiC refractory	SiO2 bonded SiC refractory
Bulk density g/cm3	2.5	/	2.70~2.75	2.78
Apparent porosity %	14~18	14~16	7~8	5.8
Cold crushing strength Mpa	100	/	130	150
Modulus of rupture Mpa(1400℃)	13	24~26	/	30~50
Linear expansion coefficient ℃^-1	4.6*10^-6	/	4.9*10^-6	4.8*10^-6
Thermal conductivity W·(m·K)^-1(1000℃)	11	/	15.7~16.9	16.2（1000℃）
SiC %	>85	>70	≥90	89.8
SiO2 %	/	/	/	8.9
Al2O3 %	/	/	/	0.5
Fe2O3 %	/	/	/	0.5

Silicon Carbide Bricks Manufacturer

RS Refractory Bricks Supplier, is one of the silicon carbide bricks manufacturer. If you want to learn more about Silicon Carbide Bricks price, and more details of Silicon Carbide refractory Bricks. Please Contact Us, we will give you back as soon as possible.

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Dec 20 2018

Silicon Nitride Bonded Silicon Carbide Bricks

Silicon Nitride Bonded Silicon Carbide Bricks Description

Silicon nitride bonded silicon carbide bricks are the most widely used nitride boned SiC refractories. Nitride bonded SiC materials have many excellent high temperature performances such as high mechanical strength, good thermal conductivity, small linear expansion coefficient, good thermal shock resistance, alkali corrosion resistance, oxidization resistance, molten metal liquid( zinc, copper, aluminum, lead,etc) corrosion resistance, as well as high temperature abrasion resistance. Si3N4 bonded SiC bricks are composite refractory, main crystalline phase is SiC, secondary crystalline phase is α-Si3N4 and β-Si3N4.

Si3N4 Bonded SiC Bricks Characteristics

Low apparent porosity.

Excellent high temperature mechanical strength.

Good high temperature creep resistance, at 0.2 Mpa load condition, RUL beginning temperature is higher than 1800℃.

High modulus of rupture.

Good thermal conductivity.

Very high alkali corrosion resistance.

Excellent oxidization resistance.

Prominent thermal shock resistance.

Excellent slag corrosion resistance.

Have strong cryolite corrosion resistance , ZnO corrosion resistance and electrolyte permeation resistance.

Si3N4 Bonded SiC Bricks Physiochemical Index

Item	Si3N4 bonded SiC brick	Sialon bonded SiC brick	Fine Si3N4 bonded SiC brick
SiC %	75.04	73.54	66~80
Si3N4 %	22.18	/	20~30
Al2O3 %	0.37	/	/
Fe2O3 %	0.27	0.32	/
Bulk density g/cm3	2.73	2.72	2.80
Apparent porosity %	13.3	14	≤11
Cold crushing strength Mpa	229	220	580
Modulus of rupture Mpa（1400℃）	65.2	56.7	180 (1200℃)
Linear expansion coefficient ℃^-1 (20~1000℃)	4.5*10^-6	4.7*10^-6	4.4*10^-6
Thermal conductivity w·（m·K）^-1 1000℃	18.4	18.2	/

Si3N4 Bonded SiC Bricks Application

Si3N4 bonded SiC refractories are widely used in steel industry, nonferrous metals industry, ceramics industry and so on. Blast furnace refractory materials corrosion reasons include: alkali corrosion, CO, Zn, SiO and water vapor oxidization, abrasion, low thermal conductivity, thermal shock and slag corrosion. In light of this condition, Si3N4 bonded SiC bricks are the ideal products for blast furnace inner lining. The service life of silicon nitride bonded silicon carbide bricks inner lining can reach to 10~15 years. It is the first choice of large scale blast furnace inner lining refractory material.

SiN4 bonded SiC refractory is the best choice of new generation aluminum reduction cell inner lining. It can decrease horizontal electric current, increase side part heat diffusion, decline cell temperature, enhance electric current efficiency and save energy. Besides, the service life of aluminum reduction cell is greatly prolonged. SiN4 bonded SiC bricks have good thermal conductivity, cryolite corrosion resistance, oxidization resistance and scouring resistance. During using, SiN4 bonded SiC bricks inner lining can form a thick and stable protective layer, which in turn effectively prolongs the service life of aluminum electrolysis cell.

Si3N4 bonded SiC bricks are also used as kiln furniture of ceramic kilns.

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Aluminum Industry Refractory

Dec 19 2018

Aluminum Reduction Cell Refractory

Aluminum Reduction Cell Description

Aluminum reduction cell is the core equipment for the production of electrolytic aluminum. Aluminum reduction cells are usually rectangular steel shells, with carbon bricks inner linings. Carbon anode suspends in aluminum reduction cell, while carbon cathode locates at the bottom. Molten Cryolite, aluminum fluoride, lithium fluoride and so on are usually used as electrolyte. Al2O3 is smelted at 970℃ and electrolyzed into metal aluminum at bottom cathode and oxygen at anode, oxygen can react with carbon anode and produce CO2 or CO. The heat released by electrochemical reaction can keep aluminum and aluminum reduction cell molten state, aluminum liquid is discharged from reduction cell at intervals, and some quantity of alumina and cryolite are added into the cell. Electrolysis temperature is kept between 900~1000℃.

Aluminum Reduction Cell Cathode Refractory

Refractory materials used in aluminum reduction cell cathode should have good electricity conductivity and good cryolite, NaF and aluminum liquid corrosion resistance. The bottom working lining of aluminum reduction cell is formerly lined by carbon block, but it can react with sodium and form new compound, the working lining’s structure becomes loose, mechanical strength deceases, and crack also appears in the carbon blocks. Electrolyte and aluminum liquid can permeate into carbon block through the cracks, and react with carbon to form Al4C3, which causes the further expansion of carbon block cracks, and finally leads to the severe corrosion of inner lining and the deformation of aluminum reduction cell shell. Therefore, amorphous carbon bricks are gradually replaced by semi graphitized carbon bricks or graphitized carbon bricks.

Aluminum Reduction Cell Side Wall Refractory

The damage reasons of aluminum reduction cell side wall inner lining are air caused material oxidization, high temperature molten cryolite, NaF and aluminum corrosion, moving molten liquid scouring and erosion, temperature fluctuation and thermal expansion caused thermal stress.

Amorphous carbon blocks and graphite carbon blocks are used to mason the side wall of aluminum reduction cell, the lethal defect of carbon based refractories is bad oxidization resistance and low mechanical strength. To prevent oxidization, and keep relatively large electric resistance, SiC refractory materials are gradually developing, among them, silicon nitride bonded silicon carbide bricks have the best application effect. The advantages of silicon nitride bonded silicon carbide bricks are: excellent high temperature mechanical performance, good thermal conductivity, easy to form condensed slay at inner side, large electric resistance, can reduce side way electricity loss, good oxidization resistance, won’t react with aluminum liquid, cryolite and other molten body, can large scale reduce lining bricks thickness and increase reduction cell volume. For example, the carbon bricks lined side way thickness is about 200~400mm, while the thickness of silicon nitride bonded silicon carbide bricks lined wall is only 75mm.

Silicon Nitride Bonded Silicon Carbide Bricks Physiochemical Index

Item	Standard value	Tested value
SiC %	≥72	73
Si3N4 %	≥21	23
Si %	≤1.0	0.3
Fe2O3 %	≤1.0	0.4
Apparent porosity %	≤17	15
Bulk density g/cm3	≥2.65	2.70
Cold crushing strength Mpa	≥150	220
Modulus of rupture Mpa(1400℃,0.5h)	≥53	65
Thermal conductivity w·（m·K）-1(1000℃,2h)	≥17	18.5

Aluminum Reduction Cell Bottom Blockage Layer

During electrolytic aluminum production, Na and NaF vapor, liquid can permeate into insulating lining from bottom cathode materials. So the thermal conductivity of insulating lining will increase and correspondingly decrease aluminum reduction cell thermal efficiency, the working atmosphere will degenerate till the damage of reduction cell. A new type of dry impervious material can be paved between cathode refractory and insulating lining, it can not only prevent the permeation of electrolyte but also has good heat preservation performance.

Dry Impervious Material Physiochemical Index

Item	Dry impervious material
(Al2O3+ SiO2) %	≥90
Refractoriness ℃	≥1630
Bulk density g/cm3	1.60~1.65
Thermal conductivity w·（m·K）^-1(400℃)	0.40
Thermal conductivity w·（m·K）-1(600℃)	0.47

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Aluminum Industry Refractory

Dec 19 2018

Aluminum Smelting Furnace and Holding Furnace Refractory

Aluminum Smelting Furnace and Holding Furnace Description

Gas-combustion or oil-combustion fixed or tilting reverberators are usually used for aluminum ingots and scrap aluminum melting and alloying, sometimes, resistance reverberator or induction crucible furnace are also adopted.

Although the temperature of aluminum liquid and aluminum alloy is only 700~800℃, magnesium, silicon, manganese and other element in aluminum and aluminum alloys are very active, easy to react with some components in refractory material and cause refractory damage. The main damage mechanisms of aluminum smelting furnaces are:

Aluminum liquid has very low viscosity, is easy to permeate into refractory material.
Some alloy elements in aluminum and its alloys have very strong reduction ability, their reduction-oxidization reaction is strong heat release reaction. Some alloy elements such as Mg have very high vapor pressure, their vapor is more liable to penetrate into refractory material and then be oxidized, finally cause the metamorphism , structure looseness and damage of refractory material.
During large scale aluminum smelting furnace working, continuously added aluminum ingots and alloy will have great impaction and abrasion to furnace inlet and furnace bottom.
The addition of aluminum ingots, the discharge of aluminum liquid and temperature fluctuation in furnace can do thermal shock damage to refractory lining.

Aluminum Smelting Reverbertator Refractories

Aluminum smelting reverbertator refractories should resist aluminum liquid and magnesium vapor infiltration, have excellent abrasion resistance and thermal stress impaction, etc. Furnace lining where contact with aluminum liquid usually adopts high alumina bricks containing 80%~85% of Al2O3. For high purity aluminum smelting, corundum bricks or mullite bricks are usually adopted. At furnace bed slope and scrap aluminum feeding parts, where corrosion and abrasion is frequently happened, silicon nitride bonded silicon carbide bricks are often used. At aluminum runner and aluminum tapping hole, aluminum scouring is severe, so self bonded or silicon carbide bonded silicon carbide bricks are adopted, zircon bricks are also used for the masonry of inner lining. For furnace lining, where don’t contact with aluminum liquid, clay bricks, fireclay castable or plastic refractory are usually used. The inner lining of aluminum running trough usually adopts silicon carbide bricks or fused foam silica precast blocks.

With the enlargement aluminum smelting furnace and the strengthening of smelting, high strength anti-aluminum permeation castable which has excellent permeation resistance, abrasion resistance and thermal impaction resistance are widely used in aluminum smelting furnace.

High Strength Anti-Aluminum Permeation Castable

Item	Index
Al2O3 %	75.6
CaO %	1.25
Refractoriness ℃	1790
Bulk density g/cm3(110℃,24h)	2.85
Crushing strength MPa (1000℃,3h)	126.42
Modulus of rupture Mpa (1000℃,3h)	15.67
Linear change rate % (1000℃,3h)	+0.01
Abrasion index	4
Thermal shock resistance times (1100℃,water cooling )	≥5

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