Industrial Refractory Archives - Page 2 of 4

The ladle is an extremely important metallurgical equipment in the steelmaking process. Its role is not only the ladle for carrying molten steel in the traditional sense but also the core carrier of the refining process outside the furnace. The choice of Refractory Materials for Ladle Lining is not only related to the life and cost of the ladle but also directly affects the output and cleanliness of molten steel. Let’s look at the use and development of refractory materials for ladle lining in a steel plant in the past 20 years.

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Development of refractory materials for ladle lining

According to a steel mill, they have 3 types of the ladle. In the order of commissioning, they are 120 t ladle, 150 t ladle, and new 150 t ladle, of which the new 150 t ladle is modified from the original 40 t ladle. The refractory materials used in different ladles are different due to different specific production requirements.

40 t ladle

Initially, the lining of the 40t ladle was entirely made of alumina-magnesia machine-made bricks, the thickness of the bottom bricks was 300 mm, and the thickness of the wall was 120 mm. Due to the shortcomings of alumina-magnesia machine-made bricks such as thermal shock stability and poor high-temperature strength, the life of the 40 t ladle bottom is only about 40 furnaces, which cannot be synchronized with the body bricks. Later, magnesia-carbon bricks were used for the bottom of the bag, and alumina-magnesia machine-made bricks were used for the wall and slag line, and the overall service life reached more than 100 furnaces.

120 t ladle

At the initial stage of production, the Refractory Materials for Ladle Lining of 120t ladle is made of alumina-magnesia machine-made bricks, the thickness of the bottom brick is 300 mm, and the thickness of the wall brick is 160 mm. In the early stage, the life of the ladle can be up to 90 furnaces when it is cast directly on the ladle. After the application of the refining process, as the refining ratio continues to increase, the life of the ladle is significantly reduced. The main reason is that the electrodes of the LF refining furnace heat up the molten steel and slag near the slag line, and the alumina-magnesia bricks are quickly melted and lost at high temperatures. In addition, refining will extend the residence time of molten steel in the ladle and also accelerate the erosion of alumina-magnesia bricks. Beginning in 2009, full magnesia carbon bricks have been used in 120t ladle. Magnesia carbon bricks have excellent slag resistance and high-temperature stability, and their service life can reach more than 110 furnaces in a smelting environment with a high refining ratio.

150 t ladle

Steel grades such as cold-rolled plates for automotive plates produced by the 150 t converter system have strict requirements on the carbon content and cleanliness of the molten steel. Therefore, from the initial stage of production, the 150 t ladle has adopted the process route of ladle bottom, clad wall alumina-magnesia machine-made bricks, and slag line magnesia-carbon bricks. At the same time, considering the CAS furnace process, the breathable brick is set in the center of the bottom of the bag, just in the molten steel impact area, and the molten steel has a serious impact on the breathable brick. In addition, due to the poor high-temperature performance of the alumina-magnesia machine-made bricks, the bottom working lining and the air-permeable bricks are severely broken. The life of the ladle is only about 70 furnaces, which cannot meet the needs of production rhythm. Later, magnesia carbon bricks were also used at the bottom of the package, and the problem of broken bricks and excessive melting loss at the bottom of the package was improved.

Application of Carbon-free Lining Materials

After a series of technical optimizations, the steel plant’s refractory materials for ladle are basically finalized. That is, magnesia-carbon bricks with 14% C mass fraction are used for the bottom and slag line, the walls are made of alumina-magnesia machine-made bricks combined with lignosulfonate, and the permanent layer is made of alumina-magnesia castable. The ladle of this material can basically meet the production rhythm of converters and continuous casting at that time. The three bricks and slag line bricks are replaced once every 20-30 furnaces are used, and the slag line bricks are replaced 1 to 2 times during the entire service process. With the development and production adjustment of various steels, the proportion of refining outside the ladle furnace is getting higher and higher. Low-carbon and ultra-low-carbon automobile panels have strict requirements on the carbon content of the lining. Traditional linings can no longer meet the production needs, so carbon-free linings have emerged.

Since 2015, steel plants have tested corundum spinel-based carbon-free materials on 150t ladle and will be promoted throughout the plant in 2016. The upgraded ladle bottom and wall are corundum spinel bricks, and the slag line uses improved magnesia-carbon bricks with 14% C mass fraction.

Corundum Spinel Bricks

The corundum spinel brick is developed under the background of the leapfrog development of refractory raw material production technology. It is a comprehensive upgraded product of alumina-magnesia machine-made bricks. The main raw materials are fused corundum, sintered corundum, fused magnesia fine powder, Al2O3 powder, alumina-magnesia spinel powder, pure calcium aluminate cement, and additives. It has the advantages of good high-temperature stability, strong corrosion-resistance, and high matrix strength.

There are 2 types of corundum spinel brick, organic pressed brick and prefabricated block. The former uses lignosulfonate as the binding agent, and the latter uses cement or alumina gel as the binding agent. The ladle built with prefabricated blocks has a better actual use effect. The machine-made bricks are easy to peel off on the upper part of the bag wall and the bricks are easy to break in the impact area of the bottom of the bag. The main reason is that the machine-made brick fine powder and aggregate are forcibly pressed together by the brick press. During use, the spinel reaction volume expands, which will cause the matrix to crack and become loose. In addition, the critical size of the machine-made brick aggregate is smaller than that of the prefabricated block, and the thermal stress caused by the temperature difference between the hot end and the cold end of the bottom-clad brick can easily break the brick body with a thickness of 300mm. The thermal strength of the prefabricated block is higher than that of the machine-made brick, so the bottom of the prefabricated block is not prone to faults.

The main phases of alumina-magnesia machine-made bricks are corundum, periclase, and mullite. The main phases of corundum spinel machine-made bricks are corundum, periclase, spinel, and α-Al2O3 micro powder. The main phases of the corundum spinel prefabricated block are corundum, spinel, α-Al2O3, and tricalcium aluminate. For details, please see Figure 2.

Figure 2 XRD patterns of alumina-magnesia machine-made brick (B1), corundum spinel machine-made brick (B2), and prefabricated block (B3)

The corundum spinel prefabricated block has two binder systems. One is pure calcium aluminate cement and alumina-rich spinel powder. The other is a gel combination system of ρ-Al2O3 gel, fused magnesia fine powder, and SiO2 fine powder. The prefabricated block of the cement-spinel system has the characteristics of high thermal strength, small volume expansion, and strong erosion resistance, and is suitable for use in the bottom working layer of the package. The prefabricated block of the gel-magnesia fine powder system has good slag resistance and thermal shock performance due to the in-situ generation of magnesia-alumina spinel and is suitable for the working lining of the clad molten pool. Starting in 2018, the steel plant eliminated corundum spinel machine-made bricks. All prefabricated blocks are used for the bottom and wall of the bag, and the melting loss of the working lining is effectively reduced.

High-performance Slag Line Magnesia Carbon Brick

The proportion of LF refining in steel plants is as high as 60%. Some steel grade liquid slags have low basicity, low viscosity, and thin slag layer. These process characteristics bring great challenges to the slag line working layer. The slag line material before 2015 was ordinary magnesia carbon brick, and the main raw materials were ordinary fused magnesia, antioxidant, flake graphite, and phenolic resin. Its corrosion resistance and oxidation resistance are not strong, and the melting rate is very fast. In accordance with the characteristics of the refining process of the steel plant, the magnesia carbon brick formula has been greatly adjusted since 2016. Use 98 fused magnesia as an aggregate and fine powder to improve the corrosion resistance of magnesia carbon bricks. Partially modified graphite is used to replace flake graphite and a nano-carbon source is introduced, which significantly improves the thermal shock resistance and mechanical properties of magnesia carbon bricks. The overall performance of the slag line magnesia carbon brick has been greatly improved.

In recent years, the changes in the physical and chemical properties of ladle slag line bricks are shown in Table 3. Since 2012, the magnesia carbon brick formula has been adjusted three times to improve the grade of magnesia. Improve the performance of graphite, reduce the high-temperature flexural strength to improve corrosion resistance.

Table 3 Ladle slag line magnesia carbon brick — Table 3 Comparison of physical and chemical properties of magnesia carbon bricks in the ladle slag line in recent years.

Optimization of Permanent Layer Refractory Materials

Before 2016, the permanent layer material used in steel mills’ ladle was traditional alumina-magnesia castable. The mass fraction of alumina is 65% to 70%, and the mass fraction of magnesium oxide is 8% to 10%. The material has the advantages of low cost and good volume stability at medium temperature. However, long-term use in a medium and low-temperature environment has serious attenuation of strength (hereinafter referred to as thermal attenuation), and the problem of poor volume stability at high temperatures is more obvious. In addition, alumina-magnesia castables are heavy materials with high bulk density and large thermal conductivity, which are not conducive to the development of lightweight ladle and the improvement of thermal insulation.

Beginning in 2017, high-alumina castables have been used on the ladle, with a bulk density of 2.453 ~ 2.55g/cm3. It not only guarantees the safety of the permanent layer but also takes into account the heat preservation. Due to the limited crane lifting capacity of the 120t converter smelting system, it is necessary to design a more lightweight ladle permanent layer material. Finally, mullite castable was used, and its bulk density was 2.0～2.1g/cm3. After laboratory tests and field tests, the two new permanent layer materials are significantly better than alumina-magnesia castables in terms of medium and high-temperature strength, volume stability, and corrosion resistance (see Table 4).

Table 4 Comparison of permanent layer pouring and cooking performance

Development Trend of Refractory Materials for Ladle Lining

The general development trend of ladle refractories is to reduce consumption and improve cleanliness. Reducing consumption not only refers to reducing the cost of refractory materials per ton of steel in ladle but also requires reducing the consumption of refractory materials per ton of steel. The purpose is to reduce the pollution of refractory materials to molten steel. To improve cleanliness, on the one hand, use anti-melting lining materials, on the other hand, select non-carbon materials, calcium materials, and other refractory materials that do not pollute molten steel to meet the requirements of producing high-grade clean steel. The next stage of the development direction of steel mill ladle refractories is mainly the following aspects. (1) The permanent layer promotes high-strength and light-weight materials to improve the thermal insulation of the ladle. (2) Promote the whole pouring scheme of the working lining to improve the service life. (3) Establish an information platform for online monitoring of steel ladle, and improve operational safety by implementing safety monitoring.

Learn more about the ladle refractories…

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Cement Kiln Refractory

Apr 22 2020

Application of Alkaline Resistant Brick in Cement Kiln

Alkaline Resistant Brick, it is made of low-alumina refractory clay as the main raw material. Because of its chemical composition, it can form a certain thickness of alkali-resistant protective layer on its surface. Therefore, it is widely used in the cement pre-differentiation kiln system as the brick lining. Rongsheng refractory manufacturer has stocks of Alkaline Resistant Bricks and refractory mortar for cement kilns lining, and supports customized Alkaline Resistant Bricks for cement kilns.

RS High Quality Alkaline Resistant Brick for Sale

Working Environment in Cement Kiln

Because the Alkaline Resistant Brick products have the characteristics of stable volume, strong resistance to alkali erosion, and penetration resistance. The application of Alkaline Resistant Bricks in cement kiln is mainly in the preheater, decomposition furnace, tertiary air duct and other parts of cement kiln.

Refractory Configuration in Cement Kiln — Refractories Configuration in Cement Kiln

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Compounds causing damage in cement kilns: alkali metal oxides (potassium oxide and sodium oxide), sulfates and chlorides. They are brought into the cement kiln system through raw meal. And because traditional fuels are more and more replaced by residues and alternative fuels, the compounds that cause damage are more brought into the kiln. Therefore, the internal circulation of alkali and sulfur varies depending on the degree of volatilization.

In the production of cement rotary kiln, it comes from harmful ingredients such as alkali, sulfur and chlorine in raw materials and fuel. In the high temperature zone, the sulfates and chlorides will escape with the kiln gas. In addition to the erosion damage to the alkaline bricks in the firing zone and transition zone, the damage he caused has been to the kiln smoke chamber, differentiation furnace, preheater and so on. As the temperature drops, it coagulates and enriches, and it can penetrate into the ordinary clay bricks and react with the brick body to generate swellable minerals. Clay bricks crack and brick lining fall off, which called “alkali crack” damage.

Application of Alkaline Resistant Brick

In addition, because of the high temperature of the clinker leaving the kiln, the alkali continuously evaporates from the clinker. Corrosion of the clay bricks at the hot end of the grate cooler, the kiln head smoke chamber and the kiln door cover constitutes an “alkali crack”. Alkali-resistant brick is an alkaline resistant clay brick with Al2O3 content of 25% -28%. It can cause the alkali in the kiln gas to condense on the brick surface and quickly react with the brick surface. It forms a high-viscosity glaze layer, which closes the continuous corrosion channels of alkali to the inside of the refractory brick body, avoiding “alkali cracking”, and then protect the furnace bricks.

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RS Alkali Resistant Brick Manufacturer

The Alkaline Resistant Bricks used in cement kilns are high-quality refractory bricks with strong alkali-resistant ability, good thermal shock resistance and high cost performance. If there is much chlorine in the cement kiln, the SiO2 content in the refractory brick can be increased appropriately. Increase the ability of the refractory brick surface to be combined with chlor-alkali to make sticky, and make alkali-resistant clay brick resistant to chlor-alkali corrosion. In addition, different alkali-resistant bricks, such as high-strength Alkaline Resistant bricks, light-weight insulation alkali-resistant bricks, etc., can be used for the brick lining according to different parts of the cement kiln.

Rongsheng refractory material manufacturer provides customers’ furnace bricks with high-quality. You can buy Refractory brick products from RS Manufacturer at affordable prices. While solving the furnace bricks lining problems for you, it saves your costs.

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Copper Metallurgy Refractory

Dec 28 2018

Copper Smelting Flash Furnace Refractory

Flash smelting is one of the most advanced copper ore smelting technique. During flash smelting, dry sulfurized fine ore powder, flux, oxygen or oxygen rich air or preheated air are injected into high temperature reaction tower hearth, the ore powder quickly realizes desulfurization, smelting, slag forming and so on. The molten metal enters into sediment bath for further slag making, and the concentrated metal can separate with slag. Flashing smelting furnace is self heating equipment, the heat is generated from sulfur oxidization in concentrate ore. This copper smelting technique combines roasting smelting and some blowing smelting together, has very high smelting intensity.

The reaction in flash furnace features intense and fast reaction speed, large thermal release intensity and complex furnace atmosphere, so the requirement on furnace lining refracotries is very high. Flash furnaces can be divided into Outokumpu flash furnace and Inco flash furnace. They are both composed of cylindrical reaction tower, sediment bath and cylindrical flue.

Reaction tower

Reaction tower is the most important part of flash furnace, air flow containing concentrate ore powder is injected into tower from the top, the chemical reaction of ore powder is carried out in a transient and melts into molten flow, which enters into sediment bath with high speed. Thus, tower lining would suffer severe scouring, erosion and abrasion caused by air current and high temperature high speed molten metal. The inner lining of reaction tower usually adopts magnesia chrome bricks, the steel shell of reaction tower are cooled by spraying cold water. At upper part of reaction tower, temperature is about 900~1100℃, oxygen partial pressure is high, so Fe3O4 protection layer is formed at tower wall, so direct bonded magnesia chrome bricks can be used here. At middle and lower part of reaction tower, the temperature is relatively high, about 1350~1550℃, and this part should endure the scouring, erosion and abrasion of molten metal. So fused cast magnesia chrome bricks are used as lining bricks, and water cooling jacket is installed at this part. Tower top are built by sintered magnesia chrome bricks.

Sediment bath

Sediment bath is rectangular molten bath, with 2.5~5m height, 3~10m length. The function of sediment bath is to further finish slag making reaction and separate molten metal. The working environment of sediment bath refractory is also very harsh, the end wall and side wall of sediment bath also suffers the scouring and erosion of high speed high temperature air current and molten metal. Especially slag line zone furnace wall, which would be scoured by continuously waving molten metal, and is the most quickly damaged part. So slag line magnesia chrome refractories should have good sulfur permeation resistance and slag erosion resistance. Sediment bath bottom should not only bear load but also endure high temperature and chemical corrosion, so rebounded magnesia chrome bricks can be used here.

Smoke flue

Smoke flue mainly suffers high temperature smoke current (containing molten slag and dust) scouring and erosion, so direct bonded magnesia chrome bricks are usually used.

Item	Fused cast magnesia chrome brick	Direct bonded magnesia chrome brick	Fused rebonded magnesia chrome brick	Synthesized magnesia chrome bricks	Magnesia chrome castable.
MgO % ≥	54	70	66	65	45
Cr2O3 % ≥	20	12	16	16	20
SiO2 % <	2.9	1.3	2.0	1.2	4.5
Refractoriness under load ℃	>1700	>1700	>1700	>1700	>1650
Apparent porosity %	<13	<16	<15	<15	/
Crushing strength Mpa≥	80	55	66	55	25
Bulk density g/cm3 >	3.35	3.10	3.3	3.25	2.85
Application	Sediment bath slag line	Sediment bath crown, ascending flue top	Sediment bath side wall, reaction tower top, triangle zone, ascending flue side wall	Reaction tower wall	H shape beam water cooling component surrounding

For some parts, where has complicated structure or difficult for the masonry of firebricks, high quality magnesia chrome castable is usually used.

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Cement Kiln Refractory

Dec 26 2018

Cement Industry Refractories

Rotary Cement Kiln Refractories

Based on the working condition of rotary cement kiln components, corresponding refractory materials should be chosen to meet the production requirement and obtain ideal cost performance.

Unloading port and unloading belt: Unloading belt usually adopts 70-80% high-alumina brick, thermal shock resistant high alumina brick, spinel brick, chrome-brick. For discharge port, high alumina brick and corundum heat resistant concrete are usually used, sometimes, silicon carbide brick or castable is also a good choice.
Sintering zone: Magnesia chrome brick, sodium polyphosphate bonded magnesia brick, alkali resistant brick and directly bonded magnesia chrome brick are often used at sintering zone. Although magnesia iron spinel brick has better kiln coating adhesion effect, it’s price is too high, so low chrome periclase spinel brick are popularly used at this part.
Transition zone: Corundum brick, 50-80% high alumina brick, direct bonded magnesia brick, ordinary magnesia chrome brick and spinel brick.
Cooling zone: magnesia chrome brick, high alumina brick, phosphate bonded high alumina brick, magnesia alumina spinel brick, etc.
Decomposition zone: Clay bricks and high alumina bricks are used at the part adjacent to preheating zone. 50-60% high-alumina bricks, ordinary magnesia chrome bricks or spinel bricks are used at high abrasion and high temperature zone that connects transition zone.
Pre-heating zone: alkali resistant insulating clay bricks.
Preheater system: alkali resistant brick and insulating brick.
Cooling machine system: refractory brick, lightweight castable, insulation material. Material loading part and high temperature zone can adopt general application magnesia chrome bricks, high-alumina bricks and clay bricks can be used for the medium and low temperature areas.

Main Refractories Physiochemical Index

Item	Anti spalling high alumina brick	Periclase spinel bricks	Silicon carbide mullite bricks	Magnesia alumina spinel bricks	Magnesia iron spinel bricks	Direct bonded magnesia chrome bricks
A1203	≥70	6~9	≥63	1-14	4-6	/
MgO	/	≥78	/	82-81	87-92	≥80
Fe2O3	/	/	/	0.8	3-5	/
Cr2O3	/	2-4	/	/	/	8
Refractoriness (℃)	1780	/	≥1790	/	/	/
0.2MPa RUL	≥1470	≥1700	≥1600	≥1700	≥1700	≥1650
CCS (MPa)	≥45	≥50	≥90	≥63	50	≥45
Bulk density (g/cm3)	2.5-2.6	≥3	≥2.6	2.85-3.0	2.85-3.0	≥2.9
Thermal conductivity W/(m·k)	1.4	/	2.5	2.8	2.6	/

New Type Dry Rotary Cement Kiln Refractories

Preheater mechanical chained pipe: ordinary alkali resistant brick, alkali resistant castable.
Decomposition furnace: anti-stripping high alumina brick, high alumina castable, alkali resistant brick, alkali resistant castable.

3.Tirtary air ducts: high strength alkali resistant bricks, alkali resistant castable.

Grate cooler: high alumina castable, alkali resistant castable, stripping resistant high alumina brick, SiC composite brick, ordinary high alumina brick, chamotte brick.
Kiln hood: anti-flaking high alumina brick, ordinary high alumina brick, high alumina castable.
Burner: high alumina castable, corundum castable.
Rotary kiln front hood: corundum castable, steel fiber high alumina castable, alkali resistant brick, SiC composite brick
Lower transition zone: alkaline brick, anti-flaking high alumina brick.
Sintering zone: basic brick, high quality phosphate high alumina brick.
Upper transition zone: alkaline brick, anti-flaking high alumina brick.
Decomposition zone: alkaline brick, high quality phosphate high alumina brick, anti stripping high alumina brick.
Pre heating zone: Flaking resistant high alumina brick, phosphate high alumina brick, alkali resistant insulating brick, alkali resistant chamotte brick.
Rear kiln inlet: high alumina castable.

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Steel industry refractories

Dec 26 2018

Runner Bricks

Runner Bricks Description

Runner brick refers to a hollow refractory brick which is masoned at the groove of bottom plate for ingot casting. Its function is connecting king brick and steel ingot mold, so molten steel or iron can be transported into corresponding molds and casted into different shapes. Runner bricks are rectangular special shaped firebricks with many specifications and dimensions. Commonly used runner bricks are clay runner bricks and high alumina bricks. To reduce the friction during the flow of molten steel and prevent steel leakage, the inner wall of the runner brick should be smooth, with tight joint. Based on steel species, output and craft requirement, runner bricks can be divided into central hole king bricks, double holes king bricks, 3 holes king bricks, 4 holes runner bricks, tail bricks and so on.

Runner Bricks Characteristics

Widely used in various types of steel casting (including stainless steel and different kinds of alloy steels).

High refractoriness, good cracking resistance and strong corrosion resistance.

Regular and intact shape, smooth inner hole, accurate size.

Good high temperature performance, scouring resistance, deformation resistance and spall resistance.

Runner Bricks Physiochemical Index

Item	Clay runner brick	High alumina runner brick
Al2O3 %	≥ 42	≥65
Fe2O3 %	≤ 2.5	≤2.5
Refractoriness ℃	≥1680	≥1780
Apparent Porosity(%)	≤24	≤25
Bulk Density (g/cm3)	≥2.20	≥2.25
Cold Crushing Strength Mpa	≥25	≥45
Refractoriness under load ℃ （0.2Mpa）	≥1390	≥1450

Interaction Between Runner Brick And Molten Steel

With the increasing demand on steel quality, cleaning steel production is more and more popular. Generally speaking, oxygen, sulfur, phosphorus, hydrogen, nitrogen and other non-metal impurities are the main factors affecting the purity of steel. There is a direct relationship between the refractory material used for steelmaking and the purity of steel. Runner bricks are usually used in bottom casting method, they contact with the molten metal directly and suffers severe scouring and chemical corrosion, which seriously affects the quality of the casted products. So the quality of runner bricks has great influence on the quality of cast steel.

RS brand clay runner bricks and high alumina bricks with good scouring resistance and erosion resistance are widely used by lots of customers. From numerous production experiences, they are proved to have better performance.

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Copper Metallurgy Refractory

Dec 26 2018

Copper Smelting Reverberator Refractories

Copper Smelting Reverberator Description

Copper concentrate ore smelting reverberator is rectangular, chamber type flame furnace, which adopts coal or heavy oil as fuel. The heat exchange of reverberator not only relies on flame reverberation, but also the radioactive heat transmission of furnace top, furnace wall and high temperature gases. The production process of reverberator is continuous, the smelting process takes place under oxidizing atmosphere and 1500~1550℃ temperature. Furnace slag is composed of iron, silicon, calcium and aluminum oxides. When the molten slag splashes on furnace wall and furnace top refractory masonry, the refractory materials will suffer corrosion and damage. The highest temperature in the reverberator is at furnace top, can reach to 1800℃. Refractory materials for this place should have high refractoriness under load temperature, good thermal shock resistance, high bulk density, small linear change rate and good slag corrosion resistance.

Copper Smelting Reverberator Refractories

The reverberator bottom mainly adopts sintered integral bottom, magnesia iron ramming mix are usually used as sintering layer material. Magnesia iron ramming mix are made from magnesia sand, iron oxide powder and brine.

Magnesia Iron Ramming Mass Index

Item	Component	Ratio	Granularity/mm	Note
Magnesia sand	MgO	78 %	Coarse sand:3~6mm; Middle sand: 1~3mm; fine sand 0~1mm	Should be dried ath 120℃~150℃ before using.
	CaO	<3.5%
	SiO2	<5%
	H2O	<0.5%
Iron oxide	FeO+Fe2O3	>95%	0.147~0.104	Melting point lower than 1400℃, dried at 120~150℃
Iron oxide	SiO2	<4%	0.147~0.104	Melting point lower than 1400℃, dried at 120~150℃
brine				Density between 1.3~1.4g/ml

The furnace wall of copper smelting reverberator are usually built by magnesia bricks, magnesia alumina bricks which have good corrosion resistance, thermal impact resistance. At some important parts such as powder coal combustor surrounding and converter slag entrance and so on, chrome magnesia bricks are used to prolong the service life. Large scale copper smelting reverberator usually adopts hanging type furnace top, made from magnesia alumina bricks.

Furnace top and vault are usually built by silica brick, magnesia alumina bricks, direct bonded magnesia chrome bricks, phosphate bonded magnesia chrome bricks. Furnace wall is built by sintered magnesia bricks, magnesia chrome bricks, chrome magnesia bricks, magnesia alumina bricks.

Furnace bed is usually constructed by lightweight clay bricks, sintered magnesia bricks, magnesia ramming mix.

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Copper Metallurgy Refractory

Dec 26 2018

Copper Smelting Blast Furnace Refractory

Copper Smelting Refractory

Compared with steel smelting, nonferrous metals smelting has more complex crafts, longer process procedures and more types of smelting furnaces. The production crafts of copper smelting comprise: pre-processing, matte smelting, copper blowing smelting, pyro-metallurgical refining and electrolyte refining.

Copper ore smelting methods can be classified into pyrometallurgy and wet metallurgy. Compared with wet metallurgy, pyrometallurgy has lower energy consumption, better adaptation to mineral grades and larger smelting scale, so pyro-metallurgy smelted copper accounts for 90% of all copper yield. Among copper pyrometallurgy smelting crafts, flash smelting and bath smelting are in dominant position.

Bath smelting is a high efficient self heating smelting method, which adopts direct blasting and intense bath agitation to swiftly realize the main chemical reactions between gas, liquid and solid phases. It is suitable for the smelting, sulfuring, oxidizing, reducing, blowing smelting and fuming of nonferrous metals materials. Flash smelting is the method that feeds dry and concentrate sulfide ore, flux, oxygen or oxygen rich air, or preheated air into high temperature furnace, raw material are quickly oxidized and melted at suspension state. The pyrometallurgy of copper including two steps: copper sulfide concentrate ore making matte smelting and matte blowing smelting.

Matte Smelting Furnace

Matte is half done copper frit which are smelted by adding silica, lime and other flux. Copper content of matte varies based on the types of smelting furnace, usually between 30%~50%. Matte smelting furnaces can be classified into blast furnace, reverberator, flash furnace and so on. Flash furnace is in the dominant position, the second is reverberator, others are isa furnace, Noranda reactor and so on.

Copper Blast Furnace

The method of making matte by copper concentrate ore in inclosed blast furnace are widely used in some countries. Copper blast furnace are composed of furnace top, furnace bosh, internal crucible, furnace hearth, tuyere and so on. During smelting, concentrate ore is added into furnace through hopper, the added ore makes the furnace a closed environment. Concentrate ore, coke, flux and other solid material are loaded from furnace top, high pressure air are blew into furnace from lower part of furnace bosh tuyere equipment. The up moving hot air will fully contact with down moving materials and make them melted, oxidized or reduced. Furnace slag and matte will separate with each other when entering into fore crucible through throat. Molten slag mainly comprises SiO2-FeO-CaO series material, the highest temperature of tuyere upper part smelting zone is 1350℃.

Copper Blast Furnace Refractory

Furnace top cover is consisted of cover board and water jacket, lateral side lining is made of chamotte bricks and asbestos board, covered by steel board. Furnace are consisted of water jackets, throat hole and furnace bottom are built by magnesia bricks.

Copper blast furnace upper part usually adopts clay bricks, chrome bricks. Tuyere and upper oblique furnace wall is built by clay bricks. The working lining of copper blast furnace is constructed by magnesia chrome bricks or chrome bricks.

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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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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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