Title of Invention	"AN IMPROVED PROCESS FOR PRODUCING PITCH FOR IMPREGNATING GRAPHITE ELECTRODES USED IN ELECTRIC ARC FURNACES".
Abstract	An improved process for producing pitch for impregnating graphite electrodes used in electric arc furnaces, v/hich is capable of producing value-added pitch of low 'quinoline insolubles' (Ql) content i.e. less than 2% by weight, viscosity 60-70 centipoise at 220°C and softening point 50-70°C, from the coal tar obtained in the high temperature carbonization of coaking coals into metallurgical cokes, and highly cost-effective, characterised in that the process comprises the steps: (a) heating the dehydrated coal tar and tar oils containing oils like creasote oil in separate containers to a temperature of 75-95°C; (b) mixing thoroughly the heated tar and oils in another container in the ratio of 40:60 to 60:4O by weight; (c) transferring the mixture into a reactor, such as herein described, through the feeding funnel (6) and maintaining the temperature of the mixture at 70-90°C by adjusting the position of the burner (8) with respect to the reactor bottom part (11); (d) allowing settling and precipitation of QI at the bottom part (11) of the reactor at ambient temperature for a period of 12 to 24 hours; (e) discarding the 'QI rich' lower portion of the mixture, constituting 25-359% of the total volume thereof through drain valve (7); (f) transferring the remaining portion of the mixture to a conventional coal tar distillation plant; (c) distilling the mixture at a temperature of 330-360°C to obtainzas the pitch for impregnating graphite electrodes. Reference: Figure 1 of the accompanying drawings.

Title of Invention

"AN IMPROVED PROCESS FOR PRODUCING PITCH FOR IMPREGNATING GRAPHITE ELECTRODES USED IN ELECTRIC ARC FURNACES".

Abstract

An improved process for producing pitch for impregnating graphite electrodes used in electric arc furnaces, v/hich is capable of producing value-added pitch of low 'quinoline insolubles' (Ql) content i.e. less than 2% by weight, viscosity 60-70 centipoise at 220°C and softening point 50-70°C, from the coal tar obtained in the high temperature carbonization of coaking coals into metallurgical cokes, and highly cost-effective, characterised in that the process comprises the steps: (a) heating the dehydrated coal tar and tar oils containing oils like creasote oil in separate containers to a temperature of 75-95°C; (b) mixing thoroughly the heated tar and oils in another container in the ratio of 40:60 to 60:4O by weight; (c) transferring the mixture into a reactor, such as herein described, through the feeding funnel (6) and maintaining the temperature of the mixture at 70-90°C by adjusting the position of the burner (8) with respect to the reactor bottom part (11); (d) allowing settling and precipitation of QI at the bottom part (11) of the reactor at ambient temperature for a period of 12 to 24 hours; (e) discarding the 'QI rich' lower portion of the mixture, constituting 25-359% of the total volume thereof through drain valve (7); (f) transferring the remaining portion of the mixture to a conventional coal tar distillation plant; (c) distilling the mixture at a temperature of 330-360°C to obtainzas the pitch for impregnating graphite electrodes. Reference: Figure 1 of the accompanying drawings.

Full Text	The invention relatet to in improvedprocess for producing pitch suitable for impregnating graphite electrodes used in electric arc furnaces. The invention relates more particularly to a process for producing pitch of 'quinoline insolubles’ (QI) content less than 2% by weight, viscosity after ageing at 220°C for 72 hours in the range of 60-70 centipoise and softening point in the range of 50-70°C (K & D)-from coal tar obtained in the high temperature carbonization of coaking coals into metallurgical cokes. The pitch produced in the existing process from coal tar contains higher QI of 7-1196 and is of higher viscosity after ageing of above 140 centipoise, and is therefore found to be unsuitable for impregnating graphite electrodes, as it does not impart the required-performance characteristics to the electrodes, such as low reactivity, low porosity and low electrical resistivity; has an appreciable surface tension at the impregnation temperature; can not properly wet the surface of the electrodes; and does not yield a sufficiently high coke residue after graphitization of the electrodes. The object of the present invention is to providean improved process for producing pitch having reduced QI content of less than 2%, viscosity after ageing in the range of 50-70 centipoise and softening point in the range of 50-70°C (K & S), which is found to be suitable for impregnating graphite electrodes. The other object is to provide a process which is capable of producing value-added pitch. Yet another object is to provide a process of high cost effectiveness. The invented process comprises essentially the following steps :- (a) mixing dehydrated coal tar, produced in high temperature carbonization of coking coals into metallurgical coke and tar oils containing heavy oils and creosote oil; (b) heating the mixture to a temperature of 75-95°C; (c) allowing settling and precipitation of the 'quinoline insolubles' (QI) at the bottom part of the mixture by retaining the mixture at the said temperature for a sufficiently long time; (d) discarding the 'Q1 rich' bottom part of the mixture; and (e) distilling the ' QI lean' top part of the mixture to obtain the residue as the pitch suitable for impregnating graphite electrodes. Thus the invention provides an improved process for producing pitch for impregnating graphite electrodes used in electric arc furnaces, which is capable of producing value-added pitch of low'quinoline insolubles' (QI) content i.e. less than 2% by weight, viscosity 60-70 centipoise at 220°C and softening point 50-70°C, from the coal tar obtained in the high temperature carbonization of coaking coals into metallurgical cokes, and highly cost-effective, characterised in that the process comprises the steps : (a) heating the dehydrated coal tar and tar oils containing oils like creasote oil in separate containers to a temperature of 75-95°C; (b) mixing thoroughly the heated tar and oils in another container in the ratio of 40:60 to 60:40 by weight; (c) transferring the mixture into a reactor, such as herein described, through the feeding funnel and maintaining the temperature of the mixture at 70-90°C by adjusting the position of the burner with respect to the reqctor bottom part; (d) allowing settling and precipitation of QI at the bottom part of the reactor at ambient temperature for a period of 12 to 24 hours; (e) discarding the 'QI rich' lower portion of the mixture, constituting 25-35% of the total volume thereof through drain valve; (f) transferring the remaining portion of the mixture to a conventional coal tar distillation plant; (g) distilling the mixture at a temperature of 330-360°C the residue to obtain the residueas the pitch for impregnating graphite electrodes. The invention is described fully and particularly by way of example only, without restricting its scope in any manner, with reference to the accompanying drawings in which - Figure 1 shows the sketch of a prototype reactor designed and constructed for performing various experiments for optimising the critical parameters of the invented process. With reference to Fig. 1, the reactor comprises a jacketed vessel (1) having a water feeding line (2) and a water draining line (3) to the jacketed part (4) containing water (5). A feeding funnel (6) is provided at the top of the reactor for feeding a preheated mixture of dehydrated coal tar and tar oils into the reactor. A drain valve (7) is provided at the bottom c of the reactor for draining out the QI rich part of the mixture at the end of a specified period of settling and precipitation of QI in the reactor. A burner (8) is externally mounted to heat the reactor with a view to maintaining the temperature the mixture (9) therein at a specified level by compensating for the loss of heat from the reactor, but without disturbing the mixture during the settling and precipitation of the QI therein. A thermometer (10) is introduced into the mixture to record the temperature thereof. The position of the bufner with respect to the bottom part (11) of the reactor, which is conical, is adjustable for controlling the temperature of the mixture. The upper part (12) of the reactor is cylindrical having the ratio of height to internal diameter of 1.2. The ratio of the height of the cylindrical upper part to the maximum depth of the conical bottom part is 3.4. Detailed experiments were performed using the reactor (Fig. 1) for optimising the following three critical parameters of the process :- (i) Ratio (w/w) of the dehydrated coal tar to tar oils in the mixture; (ii) Temperature of the mixture, to be maintained during settling and precipitation of QI; and (iii) Time to be allowed for settling and precipitation of QI. A typical example of the experiments performed is described below : 5 kg of dehydrated coal tar and 5 kg of tar oils are heated separately in two buckets to a temperature of 85°C, transferred to and mixed together in a third bucket, by stirring the mixture to attain a temperature of 80°C. The mixture is then fed into the reactor through feeding funnel (6). The burner (e) is positioned suitably to maintain the temperature of the mixture (9) in the reactor at 80°C. After allowing 16 hours for settling and precipitation of QI at the bottom part (11) of the reactor, the QI rich lower portion of the mixture, constituting about 3096 of the total volume, collected ^ at the bottom part, is drained out through valve (7) and the QI lean upper portion of the mixture, constituting about 70% of the total volume, is subjected to distillation in a known distillation column at a temperature upto 340-350°C. The residue left on completion of the distillation is the pitch which contains less than 2% QI, is of viscosity after ageing at 220°C for 72 houwsin the range of 60-70 centipoise and of softening point 50-70°C (K & S), and is found suitable for impregnating graphite electrodes. Typical results of the experiments performed are presented in Tables 1 to 3. Table 1 illustrates the effect of lowering the ratio of coal tar to tar oils in the mixture on the QI content of the QI lean portion of the mixture after allowing A hours for settling and precipitation thereof. It is noted that the reduction in QI content in the QI lean portion of the mixture is more pronounced at a lower ratio i.e. 30:70 of coal tar to tar oils in the mixture. But because of the operational problems arising from a rapid vapourization of tar oils during the subsequent distillation of the QI lean portion of the mixture if the ratio of coal tar to tar oils is made much below 50:50, the said ratio is optimised at 50:50. The effect of temperature of the mixture of coal tar and tar oils in the reactor on the reduction of QI content in the QI lean portion of the mixture is shown in Table 2 from -which it is noted that QI reduction is greater at a higher temperature. Table 3 shows the effect of the time allowed for settling and precipitation of QI in the reactor. It is noted that the reduction of QI content in the QI lean portion of the mixture is greater at a longer time of settling and precipitation. The conventional coal tar distillation plant for producing pitch of a relatively high QI content can be used after minor modifications thereof for an industrial scale production of Ditch in the invented process. Since the pitch of low QI content, viscosity and softening point, suitable for impregnating graphite electrodes, is an appreciably high value-added product and since the existing distillation plant for coal tar can be used at a marginal investfment for modifications, the invention provides a highly cost effective process for producing pitch of impregnating characteristics. TABIE 1. (Table Removed) T-ABLE 3 (Table Removed)

Full Text

The invention relatet to in improvedprocess for producing pitch suitable for impregnating graphite electrodes used in electric arc furnaces.
The invention relates more particularly to a process
for producing pitch of 'quinoline insolubles’ (QI) content less
than 2% by weight, viscosity after ageing at 220°C for 72 hours
in the range of 60-70 centipoise and softening point in the
range of 50-70°C (K & D)-from coal tar obtained in the high
temperature carbonization of coaking coals into metallurgical
cokes. The pitch produced in the existing process from coal
tar contains higher QI of 7-1196 and is of higher viscosity
after ageing of above 140 centipoise, and is therefore found
to be unsuitable for impregnating graphite electrodes, as it
does not impart the required-performance characteristics to
the electrodes, such as low reactivity, low porosity and low
electrical resistivity; has an appreciable surface tension at
the impregnation temperature; can not properly wet the surface
of the electrodes; and does not yield a sufficiently high coke
residue after graphitization of the electrodes.
The object of the present invention is to providean improved process for producing pitch having reduced QI content of less than 2%, viscosity after ageing in the range of 50-70 centipoise and softening point in the range of 50-70°C (K & S), which is found to be suitable for impregnating graphite electrodes.
The other object is to provide a process which is capable of producing value-added pitch.

Yet another object is to provide a process of high cost effectiveness.
The invented process comprises essentially the following steps :-
(a) mixing dehydrated coal tar, produced in high
temperature carbonization of coking coals into metallurgical
coke and tar oils containing heavy oils and creosote oil;
(b) heating the mixture to a temperature of 75-95°C;
(c) allowing settling and precipitation of the 'quinoline
insolubles' (QI) at the bottom part of the mixture by retaining
the mixture at the said temperature for a sufficiently long time;
(d) discarding the 'Q1 rich' bottom part of the mixture;
and
(e) distilling the ' QI lean' top part of the mixture to
obtain the residue as the pitch suitable for impregnating
graphite electrodes.
Thus the invention provides an improved process for producing pitch for impregnating graphite electrodes used in electric arc furnaces, which is capable of producing value-added pitch of low'quinoline insolubles' (QI) content i.e. less than 2% by weight, viscosity 60-70 centipoise at 220°C and softening point 50-70°C, from the coal tar obtained in the high temperature carbonization of coaking coals into metallurgical cokes, and highly cost-effective, characterised in that the process comprises the steps :
(a) heating the dehydrated coal tar and tar oils containing oils like creasote oil in separate containers to a temperature of 75-95°C;

(b) mixing thoroughly the heated tar and oils in another
container in the ratio of 40:60 to 60:40 by weight;
(c) transferring the mixture into a reactor, such as herein
described, through the feeding funnel and maintaining the
temperature of the mixture at 70-90°C by adjusting the position
of the burner with respect to the reqctor bottom part;
(d) allowing settling and precipitation of QI at the bottom
part of the reactor at ambient temperature for a period of 12 to
24 hours;
(e) discarding the 'QI rich' lower portion of the mixture,
constituting 25-35% of the total volume thereof through drain
valve;
(f) transferring the remaining portion of the mixture to a
conventional coal tar distillation plant;
(g) distilling the mixture at a temperature of 330-360°C
the residue
to obtain the residueas the pitch for impregnating graphite electrodes.
The invention is described fully and particularly by way of example only, without restricting its scope in any manner, with reference to the accompanying drawings in which -
Figure 1 shows the sketch of a prototype reactor designed and constructed for performing various experiments for optimising the critical parameters of the invented process.

With reference to Fig. 1, the reactor comprises a jacketed vessel (1) having a water feeding line (2) and a water draining line (3) to the jacketed part (4) containing water (5). A feeding funnel (6) is provided at the top of the reactor for feeding a preheated mixture of dehydrated coal tar and tar oils into the reactor. A drain valve (7) is provided at the bottom
c
of the reactor for draining out the QI rich part of the mixture at the end of a specified period of settling and precipitation of QI in the reactor. A burner (8) is externally mounted to heat the reactor with a view to maintaining the temperature the mixture (9) therein at a specified level by compensating for the loss of heat from the reactor, but without disturbing the mixture during the settling and precipitation of the QI therein. A thermometer (10) is introduced into the mixture to record the temperature thereof. The position of the bufner with respect to the bottom part (11) of the reactor, which is conical, is adjustable for controlling the temperature of the mixture. The upper part (12) of the reactor is cylindrical having the ratio of height to internal diameter of 1.2. The ratio of the height of the cylindrical upper part to the maximum depth of the conical bottom part is 3.4.
Detailed experiments were performed using the reactor (Fig. 1) for optimising the following three critical parameters of the process :-
(i) Ratio (w/w) of the dehydrated coal tar to tar oils in the mixture;

(ii) Temperature of the mixture, to be maintained during settling and precipitation of QI; and
(iii) Time to be allowed for settling and precipitation of QI.
A typical example of the experiments performed is described below :
5 kg of dehydrated coal tar and 5 kg of tar oils are heated separately in two buckets to a temperature of 85°C, transferred to and mixed together in a third bucket, by stirring the mixture to attain a temperature of 80°C. The mixture is then fed into the reactor through feeding funnel (6). The burner (e) is positioned suitably to maintain the temperature of the mixture (9) in the reactor at 80°C. After allowing 16 hours for settling and precipitation of QI at the bottom part (11) of the reactor, the QI rich lower portion of the mixture, constituting about 3096 of the total volume, collected
^
at the bottom part, is drained out through valve (7) and the QI lean upper portion of the mixture, constituting about 70% of the total volume, is subjected to distillation in a known distillation column at a temperature upto 340-350°C. The residue left on completion of the distillation is the pitch which contains less than 2% QI, is of viscosity after ageing at 220°C for 72 houwsin the range of 60-70 centipoise and of softening point 50-70°C (K & S), and is found suitable for impregnating graphite electrodes.
Typical results of the experiments performed are presented in Tables 1 to 3.

Table 1 illustrates the effect of lowering the ratio of coal tar to tar oils in the mixture on the QI content of the
QI lean portion of the mixture after allowing A hours for settling and precipitation thereof. It is noted that the reduction in QI content in the QI lean portion of the mixture is more pronounced at a lower ratio i.e. 30:70 of coal tar to tar oils in the mixture.
But because of the operational problems arising from a rapid vapourization of tar oils during the subsequent distillation of the QI lean portion of the mixture if the ratio of coal tar to tar oils is made much below 50:50, the said ratio is optimised at 50:50.
The effect of temperature of the mixture of coal tar and tar oils in the reactor on the reduction of QI content in the QI lean portion of the mixture is shown in Table 2 from -which it is noted that QI reduction is greater at a higher temperature.
Table 3 shows the effect of the time allowed for settling and precipitation of QI in the reactor. It is noted that the reduction of QI content in the QI lean portion of the mixture is greater at a longer time of settling and precipitation.
The conventional coal tar distillation plant for producing pitch of a relatively high QI content can be used after minor modifications thereof for an industrial scale production of Ditch in the invented process.

Since the pitch of low QI content, viscosity and softening point, suitable for impregnating graphite electrodes, is an appreciably high value-added product and since the existing distillation plant for coal tar can be used at a
marginal investfment for modifications, the invention provides a highly cost effective process for producing pitch of impregnating characteristics.
TABIE 1.
(Table Removed)

T-ABLE 3
(Table Removed)

Documents:

2126-del-1996-abstract.pdf

2126-del-1996-claims.pdf

2126-del-1996-correspondence-others.pdf

2126-del-1996-correspondence-po.pdf

2126-del-1996-description (complete).pdf

2126-del-1996-drawings.pdf

2126-del-1996-form-1.pdf

2126-del-1996-form-19.pdf

2126-del-1996-form-2.pdf

2126-del-1996-form-4.pdf

2126-del-1996-form-60.pdf

2126-del-1996-gpa.pdf

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Patent Number

232034

Indian Patent Application Number

2126/DEL/1996

PG Journal Number

13/2009

Publication Date

27-Mar-2009

Grant Date

15-Mar-2009

Date of Filing

27-Sep-1996

Name of Patentee

STEEL AUTHORITY OF INDIA LIMITED

Applicant Address

ISPAT BHAWAN, LODHI ROAD, NEW DELHI-110 003

Inventors:

#	Inventor's Name	Inventor's Address
1	HARSRAJ KRISHNARAO CHATI	STEEL AUTHORITY OF INDIA LIMITED, RESEARCH & DEVELOPMENT CENTRE FOR IRON AND STEEL; RANCHI -834002
2	CHANDRAN PREMALATHA	STEEL AUTHORITY OF INDIA LIMITED, RESEARCH & DEVELOPMENT CENTRE FOR IRON AND STEEL; RANCHI -834002
3	TILAKRAJ BHASKARRAO CHAHANDE	STEEL AUTHORITY OF INDIA LIMITED, RESEARCH & DEVELOPMENT CENTRE FOR IRON AND STEEL; RANCHI -834002
4	JAYANTI VINKATA SITARAMA	STEEL AUTHORITY OF INDIA LIMITED, RESEARCH & DEVELOPMENT CENTRE FOR IRON AND STEEL; RANCHI -834002

PCT International Classification Number

C10C 3/06

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA