TITLE:
Isolation and production of Activated carbon from Tar decanter sludge
FIELD OF INVENTION:
This invention relates to a method for production of activated carbon from Tar decanter
sludge.
Further, the invention also relates to the source from which the Activated carbon is
produced. The used material is a by-product of the coke making process, which is
generally categorized in the hazardous waste category.
The present invention targets at value creation from the waste generated, inside the
steel making industry. The waste generated is generally discarded or disposed of, thus
the present invention not only will provide for better waste utilization but will also add
very high value to the waste.
BACKGROUND OF THE INVENTION:
Coke plant is the integral part of the steel making industry using BF-BOF route. Coke is made by coal carbonization, i.e. heating coal in the absence of oxygen at high temperatures. In blast furnace coke acts as a reducing agent, source of thermal energy, and for providing physical support to the overburden material. During the coking

process of converting coal into coke using recovery coke oven, numerous by-products are produced. The volatile matter present in the coal vaporizes in the process and leaves the coke oven chambers as hot, raw coke oven gas. After leaving the coke oven chambers, hot gas is quenched by spraying flushing liquor, which results in a liquid condensate stream and a gas stream. This liquid condensate is the mixture of tar, flushing liquor, and carbon particles. The liquid condensate flows into tar decanters where the tar is separates from water. The heavier solid particles separate out from the tar and are removed. This heavier particle of carbonaceous nature is known as tar decanter sludge.
Every year huge amount of tar decanter sludge is produced in Tata steel as a byproduct of coke making process. The sludge falls into the hazardous waste category and proper disposal and handling of the waste is required. All the generated sludge is generally disposed off by mixing with raw coal and sending it to the coke plant for coking. The present study targets to generate some beneficial value from the sludge, which is otherwise considered as a waste material.
In the present study, the sludge recovered from the plant is used for the development of Activated carbon,

OBJECTS OF THE INVENTION:
An object of the present invention is to propose a method for the production of activated carbon from Tar decanter sludge.
Another object of the present invention is to propose an alternate raw material for the production of activated carbon.
Still another object of the present invention is to produce activated carbon from waste material for waste water treatment.
Further object of the present invention is to generate value from the by-product generated during the coke making process which is a waste.
BRIEF DESCRIPTION OF THE INVENTION:
This invention relates to a method for the production of activated carbon from Tar decanter sludge isolating the carbonaceous material from the sludge obtained from the plant,

heating the isolated carbonaceous material at a temperature of 400°C in the presence of air to remove aliphatic and aromatic volatile hydrocarbons,
subjecting the carbonized material to the step of activation using an alkali to produce activated carbon.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Fig 1: shows the process flow diagram.
Fig 2: shows TGA-MS results: (a) % mass vs temp, (b) Ion current vs temp. (CO2).
Fig 3: shows 10 g of the isolated material was initially carbonized in the tube furnace at the temperature of 420°C soaking time of 110min at normal atmosphere, maintaining the flow rate of air as 0.5 Ipm. The rate of heating was maintained to be 2°C/min. After the completion of the process the sample was brought back to normal room temperature. Shows the carbonization step temperature profile.
Fig 4: shows the uniformly blended sample is loaded in a tube furnace and then the tube furnace was heated to 400oC soaking the sample for 30 min. and then the temperature was raised to 850°Csoaking period of 80 min. under Nitrogen (N2)

atmosphere, flow rate of 0.5 Ipm. The activated samples are cooled down to room temperature followed by acid washing (2% H2S04) to neutralize the strong alkaline character from the crystallization of Potassium Carbonate. Shows the chemical activation step temperature profile.
Fig. 5: shows the series 1- maximum color removal efficiency Series 2- minimum color removal efficiency observed.
DETAILED DESCRIPTION OF THE INVENTION-
The present invention provides alternate material, which is produced in huge quantity as a by-product during coke making process; to produceActivated carbon. Thus, ensuring better utilization of the by-product generated andadding a high value to the product. The method comprises of two major steps, first step is to isolate the carbonaceous material from the sludge obtained from the plant; second step involves the activation of the carbonaceous material obtained after isolation using alkali (chemical activation) and thermal activation. The third step involved the application of the developed material, in this step the developed material was used to remove color from the steel effluent. The details of the steps are given below:

1) Isolation Step: The sludge obtained from the plant contains around 20-30 % poly aromatic hydrocarbons (PAHs, eg tar). To separate the fixed carbon particles from the sludge, solvent washing was done using Ethyl Acetate (C5H802). The sludge was mixed with the solvent and then kept overnight in an air tight container and then separated using nylon membrane (pore size0.45Micron) vacuum filter. The solids obtained were dried in the hot air oven at 103°C for 24 hours.
Material characterization: The characterization of the material obtained after isolation was done. The material obtained after washing was characterized for proximate analysis and ultimate elemental composition.
Proximate analysis: DSC-TGMS analysis of the material was done, DSC-TGA curve is as shown, fig. 2. It is observed that maximum mass loss occurs in the temperature range of 550 to 700°C, also the dip is observed in the DSC curve in the similar temperature range showing some exothermic process taking place. Also, CO2, NO2, and SO2gas was detected in the effluent gas stream at the same temperature range.
Ultimate analysis: It was observed that the waste material mainly contains around 88-90% carbon, 5-6% oxygen and 2-3% ash; tablelThe specific surface area of the sample was observed to be around 11.119 m2/g.


2) Carbonization: The isolated carbonaceous material is heated at 400°C in the presence of air to remove aliphatic and aromatic volatile hydrocarbons present in the carbon sample, if any. For this, 10 g of the isolated material was initially carbonized in the tube furnace at the temperature of 420°C soaking time of 110min. (fig.3) at normal atmosphere, maintaining the flow rate of air as 0.5 Ipm. The rate of heating was maintained to be 2°C/min. After the completion of the process the sample was brought back to normal room temperature
3) Activation: The carbon particles obtained carbonization is chemically activated using Alkali (KOH). Various ratios of carbon: alkali was prepared ranging from 1:1 to 1:4. The cooled carbonized sample was milled with Potassium Hydroxide (KOH) pellets until uniform gradation. The uniformly blended sample is loaded in a tube furnace and then the tube furnace was heated to 400°C soaking the

sample for 30 min. and then the temperature was raised to 850°Csoaking period of 80 min. (fig.4), under Nitrogen (N2) atmosphere, flow rate of 0.5 Ipm. The activated samples are cooled down to room temperature followed by acid washing (2% H2S04) to neutralize the strong alkaline character from the crystallization of Potassium Carbonate. The pH values are regulated with distilled water until neutral range (6-7). The washed sample is dried in a hot air oven for 5 hours at 105° C to remove moisture.A carbon blank is also run along in the carbonization and activation step.
4) Adsorption: The activated material was used to remove color from the BOT wastewater.
1. A high value material was produced from the waste decanter sludge, which falls in the category of hazardous waste.
a. New value-added material was produced from waste material
b. Production of activated carbon (AC) from the waste sludge. Thus, adding
value to the waste.
c. Method was developed for isolation and preparation of AC from sludge.

Example 1:
In this example Carbonized carbon samples were mixed in ratio of 1:1 with the alkali (KOH) pellets and the sample was milled using hand mortal pestle to obtain a uniform powdered mixture.
The sample was then placed in the tube furnace for activation. After the completion of the activation process the sample was thoroughly washed with acid followed by washing with Dl water to remove any unreacted potassium hydroxide (KOH), and pH is normalized (6-7). The sample was then dried and used to remove color from the BOT waste water. The dosage used was 8g/l, the sample was continuously stirred for 5 min, it was allowed to settle for another 10 min and finally it was filtered using ordinary filter paper and the color was checked using colorimeter. The color removal efficiency was also compared with commercially available wood charcoal activated carbon. Also, a blank carbon sample was tested simultaneously to check the effect of activation. The result of the removal is as shown in table 2. The specific surface area of the sample was observed to be around 27.26 m2/g.


Example 2:
In this example Carbonized carbon samples were mixed in ratio of 1:2 with the alkali (KOH) pellets and the sample was milled using hand mortal pestle to obtain a uniform powdered mixture.
The sample was then placed in the tube furnace for activation. After the completion of the activation process the sample was thoroughly washed with acid followed by washing with Dl water to remove any unreacted potassium hydroxide (KOH), and pH is normalized (6-7). The sample was then dried and used to remove color from the BOT waste water. The dosage used was 8g/l, the sample was continuously stirred for 5 min, it was allowed to settle for another 10 min and finally it was filtered using ordinary filter paper and the color was checked using colorimeter. The color removal efficiency was also compared with commercially available wood charcoal activated carbon. Also, a blank carbon sample was tested simultaneously to check the effect of activation. The result of the removal is as shown in table 3. The specific surface area of the sample was observed to be around 871.53 m2/g.


Example:3
In this example Carbonized carbon samples were mixed in ratio of 1:3 with the alkali (KOH) pellets and the sample was milled using hand mortal pestle to obtain a uniform powdered mixture.
The sample was then placed in the tube furnace for activation. After the completion of the activation process the sample was thoroughly washed with acid followed by washing with Dl water to remove any unreacted potassium hydroxide (KOH), and pH is normalized (6-7). The sample was then dried and used to remove color from the BOT waste water. The dosage used was 8g/l, the sample was continuously stirred for 5 min, it was allowed to settle for another 10 min and finally it was filtered using ordinary filter paper and the color was checked using colorimeter. The color removal efficiency was also

compared with commercially available wood charcoal activated carbon. Also, a blank carbon sample was tested simultaneously to check the effect of activation. The result of the removal is as shown in table 4.The specific surface area of the sample was observed to be around 1172.83 m2/g.


WE CLAIM:
1. A method for the production of activated carbon from Tar decanter sludge, the
process comprising:
isolating the carbonaceous material from the Tar decanter sludge; heating the isolated carbonaceous material at a temperature of 400°C in presence of air to remove aliphatic and aromatic volatile hydrocarbons; and treating the carbonized material with an Alkali to produce activated carbon.
2. The method as claimed in claim 1, wherein the step of isolating carbonaceous material from the Tar decanter sludge further comprises separatingfix carbon particles from the sludge by solvent washing and then drying the solid in an oven at 103°C for 24 hrs.
3. The method as claimed in claim 2, wherein the solvent is Ethyl Acetate (C5H802).
4. The method as claimed in claim 1, wherein the step of chemical activation further comprises heatingcarbonized material and alkali in predetermined ratio to 400°C for 30 min; thereafter soaking to 850°C for 80 min under Nitrogen (N2) atmosphere;and cooling down to room temperature followed by acid washing.

5. The method as per any of the preceding claims, wherein said step of activation preferred using carbonized material with alkali in the ratio (carbonized material:alkali) varying from 1:1 to 1:4.
6. The method as claimed in claim 4, wherein said alkali is KOH.
7. The method as claimed in claim 4, wherein acid washing is done with 2% H2S04.
8. The method as claimed in claim 4, wherein flow rate of Nitrogen (N2) is maintained at 0.5 Ipm.
9. The method as claimed in claim 4, wherein carbonized material and alkali are heat at a heating rate of preferably 4 °C/minute.