Secondary Raw-materials For Refractory Industry - IMFORMED

Secondary Raw-materials for Refractory Industry Dr. N Sahoo Director (Technical) Chaitanya Refractory Pvt. Ltd. & Global Recycling Kolkata

50 – 70% cost of refractory products is due to the cost of their raw materials . Therefore world wide attempt is made to reduce the cost of products by suitably designing the product compositions with use of some cheaper secondary rawmaterial .

M/S Chaitanya Refractory Pvt Ltd and their associate Global Recycling are in the business of producing and marketing secondary raw-materials in India and abroad . Following two activities are done by us to produce secondary raw materials . A ) Reprocessing of waste refractory products and making usable refractory raw-materials. B) R & D work to use different industrial wastes as refractory raw materials and commercialization of the developed process.

A ) Reprocessing of waste refractory products and making usable refractory raw-materials. Production of magnesia having 85 – 95 % MgO from used magnesia carbon bricks. Production of glass free AZS grains from used AZS bricks . Production of dense Alumina grains having 90-95% Al2O3 from waste alumina grinding media, spent alumina & rejected alumina articles.

B ) Use of different industrial waste as refractory raw materials as below Fused Alumina Chrome grains for bricks and monolithic. Forsterite bonded Fused Alumina chrome grains for bricks and monolithic. MgO enriched Fused Alumina chrome grains for bricks and monolithic. Fused corundum spinel grains for bricks and monolithic.

Now we cite a few examples how our secondary raw materials are used in different refractory products .

Used Magnesia Carbon Bricks

MgO Grains from recycled magnesia-Carbon Bricks MgO CaO SiO2 Al2O3 Fe2O3 B.D gm/cc (1-3) mm (0-1) mm 94.75 % 1.22 1.48 1.25 0.89 3.37 85.26 % 1.06 2.46 6.39 0.62 ----

Application of MgO recovered from recycled Magnesia- Carbon Bricks: Magnesia-Carbon and AMC Bricks. Burnt magnesia, Mag-Chrome bricks Basic Ramming mass, Gunning mass , tundish spraying mass and mortar etc.

Fused AZS Grains

Fused AZS Grains We produce AZS grains from the used AZS blocks procured from glass industries. The hot face of the used block is chipped up to the level of penetration of glassy material. Then the unaffected portion is crushed and screened to different size fractions.

Properties of AZS Grains (Wt %) ZrO2 32 (min) Al2O3 46 (min) SiO2 18 (max) Fe2O3 0.5 (max) Na2O K2O 1.5 (max) B.D (gm/cc) 3.6 (min)

Na2O content in fused AZS bricks The mineralogical phases of fused AZS bricks are baddeleyite (ZrO2), corundum (Al2O3), mullite (3Al2O3. 2SiO2) and a little amount of glassy phase. In order to reduce and eliminate the residual thermal stresses , small amount glassy phase is essential in fused cast AZS bricks . About 1.3 to 1.5 % Na2O is required to generate required quality of glassy phase by reacting with SiO2 present in the bricks .Therefore 1.3 to 1.5 % alkalis is specified in Fused AZS bricks by different manufactures as shown in Table -1.

Specification of Fused AZS Bricks-: Sl. No. 1 Name of Company Government of India Bhabha atomic Rsearch Center Nuclear Recycling Board KNPD 2 jk azs 33/ 36/ 41 fused cast azs 3 Zhengzhou Peak land Industries Co. Ltd Item 1 2 3 Alkali 1.3 1.3 - AZS-33 1.30 AZS-36 1.35 AZS-41 1.30 AZS-41 1.3 AZS36 1.4 AZS-33 1.5 Na2O K2O Na2O

Application of AZS Grains: About 30 % of WFA / BFA can be replaced by AZS grains in castables & pre-cast products. 50–60 % AZS grains can be blended with virgin raw materials for making AZS monolithic and mortar for glass industries. 20–30 % fused AZS grains in alumina carbon and high Alumina slide gate plates. 60–70 % AZS can be used for making Tundish Nozzles

Fused Alumina Chrome (FAC)

Chemical composition (Wt %) Al2O3 80 min Cr2O3 13 min CaO 1 max Fe2O3 0.5 max MgO 1.0 max TiO2 Na2O 0.5 max 0.6 max

Physical Properties: B.D (gm /cc) Hardness (Mohs) 3.6 8.4 Melting Temperature SK 40 (1920 ⁰C) Mineralogical Phase solid solution of Al2O3 & Cr2O3 Grading, 3/5 , 1/3 , 0/1 , 150 mesh & 250 mesh

Application: 40 -50 % FAC grains in LC-80 and LC-90 castables / precast products for EAF delta, Roof of VD/ VAD 60-70 % FAC grains in LC-80 castable for the mouth of torpedo ladle. Use of 30% FAC in LC-90 castables for making precast seating block and well block. 50- 60 % FAC in LC-80 / LC-90 precast block for the reheating furnace bottom. FAC based burnt bricks for incinerators. 50 - 60 % FAC fine for making 90 K mortar As abrasive grains .

Process :

Composition of LC – 80 Indian Bxt (3 – 5) mm India Bxt (1 – 3) mm Sillimanite sand FB FAC (1 – 3) mm FB FAC (0 – 1) mm Indian Bxt -150 mesh Secar 68 v Micro silica 9400 HGMR – 30 (Micro fine Alumina) SHMP powder Water for casting B. D (gm/cc) 20 % 20 10 10 10 10 5 5 10 0.1 part 5 parts 2.80 CCS (kg/cm2) Drying at 1100C- 980 Firing at 14500C 1053

Bottom Pouring Refractories

Properties of Bottom Pouring refractories with 50 % FB FAC Al2O3 % Fe2O3 TiO2 CaO MgO Cr2O3 A.P % B.D (gm/cc) CCS (kg/cm2) App.Specific. Gravity RU.L. ( ta ) PCE 79.0 1.0 1.8 0.6 6.1 7.9 17.9, 2.95, 690, 3.6, 14400C SK 33 (17450C )

Chaitanya Refractory Pvt. Ltd. & its associate Global Recycling are processing and marketing about 2000 mt. secondary refractory raw materials per month. This results in saving of a huge amount of natural resources. The use of secondary refractories will become mandatory in future in the refractory industry due to environmental and commercial reasons.

B ) Use of different industrial waste as refractory raw materials as below Fused Alumina Chrome grains for bricks and monolithic. Forsterite bonded Fused Alumina chrome grains for bricks and monolithic. MgO enriched Fused Alumina chrome grains for bricks and monolithic. Fused corundum spinel grains for bricks and monolithic.