CLIAMS:1. A process for preparing the tap hole clay for plugging the tap hole of blast furnace, the process comprising the steps of:
- crushing the raw materials into pieces to the desired size followed by weighing the raw materials on the digital weighing machine to the weight of at least 2 kg batch
- sieving the crushed raw materials in a vibrating sieve shaker to avoid clogging
- mixing the bauxite from the said sieved raw material homogeneously in dry conditions with other dry materials consisting of plastic fire clay, silicon carbide, coke, pitch and powder resin for 10-20 minutes
- adding the preheated wash oil to the said running mixture and mixing it for 10-20 minutes
- mixing the preheated tar decanter sludge to the said mixture and mixing it for 10-20 minutes
- collecting the discharged mixture from the mixer in a container for obtaining a tap hole clay suitable for smooth operation of tap hole.

2. A process as claimed in claim 1, wherein the composition of sieved bauxite aggregates are 80-88% of Al2O3, 2% Fe2O3, 4% of TiO2,0.7% of Alkali, 0.5% of moisture respectively.

3. A process as claimed in claim 1, wherein the size of sieved plastic fire clay is -1mm, Silicon carbide is -100microns, pitch is -1mm, coke breeze is -1mm and powder resin is 200mesh size.

4. A process as claimed in claim 1, wherein the plastic fire clay contains 35-40%w/w of Al2O3, 45-50% w/w of SiO2, 1.0-1.5%w/w of Fe2O3, 2-3%w/w of moisture.

5. A process as claimed in claim 1, wherein the Silicon carbide contains 85-88%w/w of SiC, 2-3%w/w of SiO2, 0.80-1.0%w/w of free Carbon, 2.75-3.0%w/w of Fe2O3, 0.80-0.95%w/w of free Silica, 0.2-0.7%w/w of moisture, 3.5-4.0%w/w of others.

6. A process as claimed in claim 1, wherein the Pitch contains 19.21-25.64 %w/w of Quinoline insoluble, 54.34-59.25%w/w of toluene insoluble, 63.43-65.74%w/w of coking value, 0.15-0.20%w/w of ash content, 30.45-35.94%w/w of Beta resin

7. A process as claimed in claim 1, wherein powder resin contains 8.20-10%w/w of hexamine content, 10-25%w/w of ash content

8. A process as claimed in claim 1 , wherein the wash oil contains 2.77-4.9%w/w of naphthalene,1.5-2.0% of moisture

9. A process as claimed in claim 1 , wherein the wash oil was preheated to 60-70°c in drier.

10. A process as claimed in claim 1 , wherein the tar decanter sludge was preheated to 80-100°c.

11. A process as claimed in claim 1, wherein the coke contains 82-84%w/w of carbon, 15-18%w/w of ash, 0.5-0.8% w/w of volatile material
12. A process as claimed in claim 1, wherein the tar decanter sludge contains 8.5-9% of Carbon, 4.5-5% of hydrogen, 53-54% of volatile matters, 3.5-4% of moisture.

13. A process as claimed in claim 1, wherein the solubility of pitch with wash oil is due to high softening point of Pitch in the range of 170-176°c.

14. A process as claimed in claim 1, wherein the quality in tap hole clay can be improved by restricting the ash content in the resin.

15. A process as claimed in claim 1, wherein the curing or setting time of tap hole clay depends on the gel time of resin at 150°c which is in the range of 75-90°c.

16. A process as claimed in claim 1, wherein the distillation range of wash oil used is 220-350°c to achieve the maximum solubility of pitch and increasing the fluidity of the pitch.

17. A process as claimed in claim 1, wherein the mixture is placed in a sand rammer by pouring the mixture into a mould of 50mm diameter and around 50mm height and applying 20 strokes by the said sand rammer to achieve tap hole clay of 50mm diameter and 50mm height.

18. A process as claimed in claim 1, wherein the mixer used is muller mixer.

19. A tap hole clay for plugging the tap hole of blast furnace comprising

of the following ingredients:
Materials Percentage (%)
Bauxite aggregates 30 - 32
Plastic clay 9.5 - 10.5
Silicon carbide 14 - 16
Pitch 14 - 15.5
Powder resin 6 - 7
Coke 7.5 -8.5
Wash oil 7.4-8.6
TDS 2.4-3.6

20. A tap hole clay as claimed in claim 19, wherein pitch and wash oil are used as a binders.

21. A tap hole clay as claimed in claim 19, wherein the coke is used to increase the porosity which allows inside gas of blast furnace to escape through the clay thereby heating up the mass and hardening it within a short period.

22. A tap hole clay as claimed in claim 19, wherein the silicon carbide used has a high melting and high thermal conductivity which makes it suitable for using as an ingredients in the tap hole clay and reduces the erosion of the clay when hot metal flows through the tap hole.

23. A tap hole clay as claimed in claim 19, wherein the plastic fire clay gives plasticity in tap hole clay and extruding properties which is

very much required to plug the tap hole.

24. A tap hole clay as claimed in claim 19, wherein the tar decander sludge is used as partial replacement to the wash oil.
,TagSPECI:Field of Invention

The invention relates to a process for preparing the tap hole clay for plugging the tap hole of blast furnace from the Tar decanter sludge generated and the tap hole clay made thereof. Tap hole clays are unshaped refractory which are used to plug the tap hole of Blast Furnace and the tap hole clay made must have the capability of being drilled during tapping. Plugging compositions for blast furnace tap holes comprising Bauxite aggregates, plastic clay, silicon carbide, pitch, powder resin, coke, wash oil and tar decanter sludge. They are characterized by enhanced compressive strength at elevated temperatures, increased plasticity, increase thermal conductivity temperatures and high melting point as compared to conventional binders thereby recycling the tar decanter sludge generated in the iron and steel industries.

Background
The blast furnace is a tall shaft-type furnace with a vertical stack superimposed over a crucible-like hearth. The outer shell of a blast furnace is made up of steel. The refractory lining is provided inside the shell. The blast furnace is broadly divided into:
• Stack, whose wall slopes outwards going downwards
• Belly, the cylindrical portion below the stack
• Bosh, located below the belly and sloping inwards going downwards
• Hearth, located below the bosh and tuyere region and the cylindrical portion, where tap hole is located.
The charge of the blast furnace consists of Lumpy iron ore (the ore is either Hematite or Magnetite of 10/40 mm sized), in the form of, in the form of pellets and sinters, limestone, dolomite as flux and metallurgical coke. It operates on a counter-current principle; the charge moves slowly down in the furnace shaft and the current of gas that reacts with the charge moves upward. This operation is known as reduction smelting. The furnace has two functions to perform: (1) to reduce the oxides of iron to the metallic state, and (2) to fuse the entire mass to form molten metal and liquid slag.

The molten iron and slag are removed, or casted, from the furnace periodically. The casting process begins with drilling a hole using a drilling machine, called the tap hole. Tap hole is an outlet for hot metal and slag produced in a Blast Furnace. During casting, molten iron flows into runners that lead to transport ladles. Slag also flows into the tap hole clay filled iron notch at the base of the hearth and is directed through separate runners to a slag granulation plant adjacent to the cast house, or into slag pots for transport to a remote slag pit.

The Disposal of Tar decanter sludge produced as byproduct is difficult because it is a sticky material and it easily melts during the Indian summer. When melted, it spreads and further pollutes the disposal area. Moreover tar decanter sludge contains various toxic organic compounds, which are classified as hazardous waste within the Hazardous Waste Management and Handling Rules. As a result, it becomes obvious to recycle this hazardous by-product.

Tar is a valuable byproduct of coke oven plant. High-temperature tars, contain large proportions of aromatic compounds, phenols, cresols, naphthalene, benzene and its homologues, and anthracene as important constituents. They are produced by the cracking of the primary tars which result from the breakdown of the coal structure itself. It is the aromatics that pose the most danger to both humans and fish and wildlife. Chronic effects of some of the constituents in coal tar include changes in the liver and harmful effects on the kidneys, heart, lungs, and nervous system. Coal tar is among 31substances classified by the Chief of the Worker Health and Safety Unit of the California Department of Food and Agriculture as having "high carcinogenic or oncogenic potential".

Most of the coal tar by-products have different uses, but coal tar sludges remain as a waste product. The disposal of these material is coming under close scrutiny of environmental regulatory agencies. A waste fraction known as tar decanter sludge (TDS) is of increasing importance since it has been classified as a “listed” hazardous waste by the U.S Environmental Protection Agency. It is required that the plants, where these kind of by-products are produced must dispose of this sludge either by internal recycling in the process (within the plant) or by hauling it to an approved secure landfill.

The importance of having a good quality tap hole clay is more and more obvious as the volume of the blast furnace is going larger & larger and the complexity of casting operation is increasing accordingly.
Keeping into the view all the above aspects the present invention describes the method for manufacturing the tap hole clay from the Tar decanter sludge produced in the coke oven plant as a by-product.

Object of Invention:

• The object of the present invention is the use of Tar decanter sludge produced in the coke oven plant partly, as a lubricant as well as solvent material, for the preparation of tap hole clay
• Another object of the present invention is the recycling of hazardous tar decanter sludge thereby removing an important environmental pollution problem.

Prior Art

WO 1997041264 A1 teaches about the process and device are disclosed for closing a tap hole. A plugging mass is pressed by a tap hole plugging machine into the tap hole to be closed and thermally set therein. The plugging mass is tempered in the tap hole plugging machine in such a way that its temperature is set at a processing temperature at which the plugging mass is very ductile. For this purpose, the tap hole plugging machine has a device for tempering the plugging mass in the plugging chamber (4) which preferably includes a device for heating the plugging mass before it is pressed into the tap hole and a device for cooling the plugging mass in the tap hole plugging machine while and/or after it is pressed therein.

US Patent No. US4,399,982 teaches about a blast furnace tap hole plugging composition comprising a coal tar binder, refractory filler and a very heavy aromatic petroleum oil which fails to polymerize at the high heating rates experienced during normal application of the tap hole mix to the tap hole. Preferred aromatic petroleum oils useful in the present invention have a minimum boiling temperature of 700° F. and above and a boiling range between 700° F. and 1000° F. Methods of making and using such
plasticized tar bonded blast furnace tap hole mixes are also disclosed.

WIPO Patent Application WO 2012011880 A2 teaches about an invention relates to a composition of plastic refractory material intended for stopping-in tap holes of blast furnaces intended for molten iron production. The nature of the invention lies in an appropriate composition of material made by grogs of refractory shales and silica sand, additives enhancing resistance to molten metals, plasticizers of clay and resins. An appropriate proportion of refractory grogs, clays, carbon additives is mixed with an appropriate proportion of Novolak and Phenolic - resol resin in a mixer and by shaping homogenous mass to loaves under vacuum, when loaf bulk density of about 2,100 kg.m'3 is reached. Mixing time is controlled in dependence on temperature of mass mixed and must not exceed 40 °C. According to the invention, mass compaction occurs, e.g. at pressure 8 MPa per loaf surface of e.g. 250 x 120 mm. When designing mass composition for a final customer, it is possible to select an appropriate proportion, combination of synthetic resins of the Novolak and resol type, in order to obtain technological effect required for its application.

Detailed Description

Tap hole clays are used for plugging of the tap hole of blast furnace. The major objective of this material is not only to plug the Tap hole but also to be drilled for the subsequent cast. The mud gun pushes the tap hole clay into tap hole of blast furnace where it hardens and checks the hot metal and slag from coming out of blast furnace.
Modern blast furnaces work with a tap hole length 2-3.5 meter. The tap hole clay has the task of closing the tap hole and to protect the walls on the inside as they are particularly stressed by the intense tapping flow.

The tap hole clay must consistently and safely perform the following functions:

• Flow when pushed by the clay gun, to plug the tap hole.
• Cure within the tap hole during the plug to tap time but without shrinkage to ensure air tight seal.
• Be drilled in an acceptable time.
• Allow a stable, controlled melt stream at tap without spray
• Withstand erosion and corrosion by iron and slag.
• Form a stable substrate for the next plug
• Provide a stable and controllable tap hole length.

These factors are best achieved by considering not just the clay but the tap hole environment as a whole. Tap hole length is of vital importance for achieving a long blast furnace campaign. A longer tap hole draws liquids from nearer the center of the hearth, while a short tap hole promotes peripheral flow leading to hearth wear. This is a function of the amount of clay injected and also of the erosion resistance of the clay. Thus there is a requirement of a tap hole which wears in a smooth and predictable way. A smooth hole promotes laminar flow and a smooth tapping stream, which in turn reduces wear in the trough and can make a significant contribution to controlling cast house refractory costs. The clay required should be erosion/corrosion resistant but produce a smooth bore during drilling and tapping.
The main by product in the process of coke making is crude coke oven gas and this contains lot of valuable chemicals. Coal Chemical Plant recovers Ammonia (NH3), Tar and Benzol from CO-Gas. The primary By-products from Crude CO Gas are Ammonium Sulphate (NH4) 2 SO4, Crude Tar, Crude Benzol and cleaned coke oven gas. Coke oven gas contains: Crude Tar- 3.2 % , Ammonia (NH3) - 0.3% or 7-10 gm/Nm3of coke oven gas, Crude Benzol - 0.7% or 20 gm/Nm3 of coke oven gas. Production of coke oven gas per ton of dry coal is 350 Nm3 at calorific value of 4300 Kcal/Nm3.

The Coke Oven Gas (CO Gas) leaves the ovens at a temperature 800oC and is cooled in goose necks and in gas collecting mains in the batteries by means of spraying Ammonia liquor (Flushing liquor) from 8000 C - 800 C.

Further it is cleaned to recover valuable by-products. During this process TDS is generated

In a Iron and Steel making plant, yearly production of tar decanter sludge is around 2800-2900tons/year.
According to an embodiment of the invention, a process for preparing the tap hole clay for plugging the tap hole of blast furnace, the process comprising the steps of:
- crushing the raw materials into pieces to the desired size followed by weighing the raw materials on the digital weighing machine to the weight of 2 kg batch
- sieving the crushed raw materials in a vibrating sieve shaker to avoid clogging of sieves
-mixing the bauxite from the said sieved raw material homogeneously in
dry conditions with other dry materials consisting of plastic fire clay,
silicon carbide, coke, pitch and powder resin for 10-20 minutes
- adding the preheated wash oil to the said running mixture and mixing it for 10-20 minutes
-mixing the preheated tar decanter sludge to the said mixture and mixing it for 10-20 minutes
-collecting the discharged mixture from the mixer in a container and use as a tap hole mass

According to an embodiment of the invention, the percentage of different materials used for manufacture of the tap hole clay is as follows:
Materials Percentage (%)
Bauxite aggregates 30 - 32
Plastic clay 9.5 - 10.5
Silicon carbide 14 - 16
Pitch 14 - 15.5
Powder resin 6 - 7
Coke 7.5 -8.5
Wash oil 7.4-8.6
TDS 2.4-3.6

The different ingredients used for the manufacture of tap hole clay are described below:
• Bauxite is an aggregate material, containing higher percentage of Al2O3, has a high melting point. So that tap hole clay can withstand very high temperature.
Properties Amount
Al2O3 (%) 85-88
Fe2O3 (%) (max) 2
TiO2 (%) (max) 4
Alkali (%) (max) 0.7
Moisture (%) (max) 0.5
Density (ton/m3) 3.2

• Plastic Fire Clay is very fine powder composed of Al2O3, SiO2 and some chemically combined water. It is used to give plasticity in tap hole clay, gives extruding properties which is very much required to plug the tap hole.
Properties Amount
Al2O3 (%) 35-40
Fe2O3 (%) 1.0-1.5
Moisture (%) 2-3
Loss on Ignition(LOI) (%) 10-12
Refractoriness 1700oC
Size (-)1mm (80% min)
• Silicon Carbide (SiC) is having high melting point, high volume stability, high abrasion resistance and high thermal conductivity which make it suitable for using as an ingredient in the tap hole clay. It reduces the erosion of the clay when hot metal flows through the tap hole.
Properties Amount
SiC (%) 85-88
SiO2 (%) 2.95
Free Carbon (%) 0.85-1.0
Total Fe2O3 (%) 2.75-3.0
Free Silica (%) 0.80-0.95
Others (%) 3.5-4.0
Moisture (%) 0.50
Size -100 microns
• Pitch is used as a binding material, dissolves in wash oil and works as abinder at high temperature.
Properties Amount
Softening Point (oC) 170 (min) - 176 (max)
Quinoline insoluble (%) 19.21 (min) - 25.64 (max)
Toluene insoluble (%) 54.34 (min) - 59.25 (max)
Coking Value (%) 63.43 (min) - 65.74 (max)
Ash content (%) 0.15 (min) - 0.20 (max)
Beta resin 30.45 (min) - 35.94 (max)
Size (-)1mm (60% min)
• Powder Resin is used to increase the speed of setting of mass in tap hole (curing time) which will reduce the holding time of mass in tap hole, gives more time to make it ready for next tapping.
Properties Amount
Gel time (Second) at 150oC 75-90
Hexamine content (%) 8.20-10
Melting point (oC) 100
Ash content (%) 10-25
Size 200 mesh more than 90%
• Coke is used to increase porosity, increase volume of the mass and decrease density, this allows the gas to escape through the mass.
Properties Amount
Carbon (%) 82-84
Ash (%) 16-18
VM (%) 0.5-0.8
Size (-)1 mm
• Wash Oil is mainly used for improving the fluidity of pitch and bonding in the mass and makes the mass fluid enough for good workability.

Properties Amount
Specific Gravity at 30oC 1.080-1.087
Drop point (oC) 200-230
Moisture (%) 2.0 (max)
Naphthalene (%) 2.77- 4.9
Distillation range (oC) 100% between 220-350oC

• Tar decanter sludge contains carbon, silicon, volatile matters and oil with moderately good binding properties.
Properties Amount
Carbon (%) 8.76
Hydrogen (%) 4.78
Volatile Matter (%) 53.25
Moisture (%) 3.86

The sieve analysis was carried out with a wide range of sieve sizes 1-3 mm (coarse fraction or CF), 0-1mm (middle fraction or MF) and (-)200 mesh or =75µm (small fraction or SF) and sieved in a vibrating sieve shaker to avoid the clogging of sieves as well as to ensure efficient sieving.All the materials are sieved according to the size mentioned in the composition table.
According to an embodiment of the invention, all the raw materials are weighed on the digital weighing machine.Proper blending is very important to the clay to attain homogeneous mix.

The muller type mixer provides additional mixing forces over that of more conventional mixers to assure that the mulling is an extension of mixing resulting from the intensification of work forces. The work forces are applied via the tread of weighted mulling wheels. The weight, and thereby the mixing efficiency, is controlled through a spring suspension arrangement on the wheel that is fully adjustable and allows the user to increase or decrease the amount of work that is applied to the mixture via the mulling wheel. This extension of mixing has proven to be a successful method in a wide range of applications.

According to an embodiment of the invention, the Bauxites were taken in a Muller mixer along with other dry materials like plastic clay, silicon carbide, coke, pitch and powder resin and mixed homogeneously in dry condition for 10-15 minutes. The typical size fraction of the dry mix sample collected just before mixing the lubricant was noted as given below:

+1mm +0.5mm +180mesh -180 mesh
17.5 - 19.5 (%) 12 - 13.5 (%) 20-23(%) 44.40(%)
Then wash oil is added in mixer at (heated oil) 65-70 degrees centigrade, mixing continued with wash oil for 3–5minutes. After that 80-100degrees centigrade heated tar decanter sludge is slowly added as per calculated amount and mixing continued for 10-15 minutes. The entire process has taken about 30-35 minutes. The lumpy mass discharged from the mixer was collected in a container and cut manually to pieces around 150 grams and kept in the boxes. This plastic mass can be directly used to plug the tap hole of Blast Furnace.

According to an embodiment of the invention, ramming is done to form the sample on to the required shape by placing it in the mould. The sample of diameter 50mm, height 50mm. Proper lubrication should be made before placing the sample in the mould so that Sample can be easily removed. Sample was prepared by giving 20 strokes using sand rammer. Then the Samples were de-moulded and first dried in the drying oven at 100-120oC for 30minutes and then fired in a gas fired furnace at 10000C for 8 hrs at reducing atmosphere.

To characterize the prepared tap hole clay suitable for smooth operation of tap hole, different tests have been carried out both for green and fired samples. The typical characteristics of tap hole clay are as given under:
Apparent Porosity (%) Bulk Density (gm/cc)
(Green Sample) Bulk Density (gm/cc)
(Fired Sample) Cold Crushing Strength (kg/cm2)
25-31 1.95-2.04 1.60- 1.68 50-58

The invention will be described with reference to following example without restricting the scope of the invention.

Example -1:
A process for preparing the tap hole clay for plugging the tap hole of blast furnace, the process comprising the steps of:
- crushing the raw materials into pieces to the desired size followed by weighing the raw materials on the digital weighing machine to the weight of 2 kg batch
- sieving the crushed raw materials in a vibrating sieve shaker to avoid clogging of sieves
-mixing the 31% of bauxite from the said sieved raw material homogeneously in dry conditions with other dry materials consisting of 10% of plastic clay, 16% of silicon carbide, 8% of coke, 15% of pitch and 7% of powder resin for 15 minutes
- adding the preheated wash oil at 65°c to the said running mixture and mixing it for 15 minutes
-mixing the preheated tar decanter sludge at 100°c to the said mixture and mixing it for 15 minutes
-collecting the discharged mixture from the muller mixer in a container for obtaining a tap hole clay suitable for smooth operation of tap hole.

Example-2
A process for preparing the tap hole clay for plugging the tap hole of blast furnace, the process comprising the steps of:
- crushing the raw materials into pieces to the desired size followed by weighing the raw materials on the digital weighing machine to the weight of 2 kg batch
- sieving the crushed raw materials in a vibrating sieve shaker to avoid clogging of sieves
-mixing the 30% of bauxite from the said sieved raw material homogeneously in dry conditions with other dry materials consisting of 9.5% of plastic clay, 14% of silicon carbide, 7.5% of coke, 14% of pitch and 6% of powder resin for 10 minutes
- adding the preheated wash oil at 70c to the said running mixture and mixing it for 10 minutes
-mixing the preheated tar decanter sludge at 80c to the said mixture and mixing it for 10 minutes
-collecting the discharged mixture from the muller mixer in a container for obtaining a tap hole clay suitable for smooth operation of tap hole.

While the invention has been described in detail with the help of a preferred embodiment, the invention is not limited to the disclosed examples. Other variations can be deducted by those skilled in the art without leaving the scope of protection of the claimed invention.