FIELD OF INVENTION:
The present invention relates to carbonization of coal and coal blends and in particular to the developing of a carbonization furnace for determining the carbonization mechanism of coal and coal blend with adequate control on carbonization process parameters and also achieve desired quick characterization of coal and coke. The furnace of the present invention is preferably adapted to accommodate about 30 kg charge of coal and coal blend and also for post-carbonization dry quenching facility for rapid cooling of coke to instill desired strength properties. The carbonization furnace of the invention would enable maintaining historical trends for all vital carbonization parameters and would have an in-built fault finding system. Thus the carbonization furnace of the present invention would serve as an energy optimized device consuming very little electrical energy, for quick characterization of coal and coke and the experimental determination of mechanism of carbonization, on which very little specific information is available, and is therefore directed to have wide industrial applicability and use.
BACKGROUND AND PRIOR ART:
Carbonization of coal is a unique process where the heating control plays a pivotal role in coal making.
In particular, it is well known in the art of carbonization of coal and coal- blend in industrial coke ovens that it is a unique process where coal goes into the softening state at an elevated temperature range of 400-460°C. Thereafter, coal starts solidifying and formation of semi-coke starts. Actual hard enriched coke is obtained around and in excess of a temperature of 1000°C. The rate of evolution of moisture and volatile matter plays a significant role in the carbonization of coal and coal blend. With the rise in temperature, the moisture in coal first starts evolving, followed by the low boiling point components of the coal volatile matter. There are various reactions that occur during the carbonization process e.g. polymerization, co-polymerization, poly-condensation, cracking etc. All these reactions affect the overall performance of the carbonization process. Since it is difficult to study the
2
mechanism of these complex process and reactions taking place inside the furnace/oven, monitoring of some of the key parameters like weight loss of the gross coal charged in the oven, pressure at the centre of coal mass, temperature control at furnace wall and monitoring differential temperature gradient etc. can be of significance in determining and understanding the mechanism of coal carbonization process.
Conventionally, it is known to utilize coke ovens for determining carbonization of coal, evaluation of new coals for coke making.
The existing process of determining the carbonization characteristic of coal is carried out in pilot coke oven of 300 kg charging capacity with movable wall and heating system based on instrumentation with PID control. Such oven is known to have been utilized to evaluate new coal specimens for suitability for coke making. Carbonization of coal is a unique process where the control of the heating process, rate of heating/cooling, maximum temperature for coking and holding time (soaking) at specified temperature are all critical factors for determining desired coke characteristics. The heat transfer takes place from both side walls through conduction, convection and mainly radiation. The principle of heating in such coke ovens is based upon master-slave PID control. However, such method of heating and its control was found to be not uniform in various zones because of presence of door leakage and other failure parameters including heat loss from furnace walls to environment, adversely affecting the quality of resulting coke. The carbonization process which is essentially carried out in absence of air and at an uniform positive pressure of 10-15mm of water inside the furnace through out the cycle time of operation of 16-18 hours could hardly be accurately controlled in the existing pilot oven. Importantly, in such known systems, it has been extremely difficult to maintain the same pressure inside the furnace during eighteen hours operation. Moreover, in the existing methods of carbonization, the analysis of heating process or standardization of other control parameters were not possible, making it difficult to identify reasons for any failure of process to achieve desired coke properties.
3
Even with the provisioning of the PLC based control for the existing 300 kg oven, it has not been possible to know the mechanism of carbonization with sufficient details so that desired quality of coke from given character of coal sample, could be achieved with certainty in actual operation of industrial coke oven plant, usually slotted type. Because of this reasons, furnace shutdown was frequent resulting in poor quality of coke at the end of long carbonization process time of 16-18 hours. It was therefore the need for quality coke making process to develop a furnace for standardizing methods of the mechanism of carbonization, with full provisioning of control measures for all intervening parameters for quick characterization of coal and coke.
OBJECTS OF THE INVENTION:
It is thus the basic object of the present invention to provide for a pilot coal carbonization furnace /oven for industrial application which would facilitate quick and more confirmatory characterization of coal and coke.
Another object of the present invention is directed to the development of a pilot coal carbonization furnace for quick characterization of coal and coke which would further enable determination of the mechanism of coal carbonization with superior control on process parameters to ascertain desired properties of coke from given character of charge of coal and coal blend.
A further object of the present invention is directed to a coal carbonization furnace to achieve faster carbonization process maintaining uniform carbonization conditions all through the oven, uniform temperature heating control through PLC in all the zones of the walls of the furnace and uniform positive pressure level of the oven throughout the carbonization period .
Yet further object of the present invention is directed to a coal carbonization furnace to achieve faster carbonization process, which would also enable
4
continuously monitoring the center gas pressure during carbonization and also the oven pressure during the entire carbonization period.
A further object of the present invention is directed to the development of a coal carbonization furnace to achieve faster carbonization, which would be further adapted to measure the movement of the plastic layer inside the coal mass in the furnace during carbonization.
Another object of the present invention is directed to the development of a user friendly coal carbonization furnace to achieve faster carbonization, which would be further adapted to generate historical trend of the carbonization pattern.
Yet another object of the present invention is directed to the development of an user friendly and cost-effective coal carbonization furnace which would have the facility for weight loss during carbonization, variety of quenching facilities including dry quenching facility for the hot coke mass at higher temperature, pressure dry quenching facility and mixed quenching facility (dry and wet).
Yet another object of the present invention is directed to a coal carbonization furnace which would be having in-built system for fault finding to thereby provide for a more confirmatory process of carbonization of coal.
Yet another objective of the present invention is directed to achieve the said uniform heating rate in a pilot coal carbonization furnace at all locations inside the oven by way of selective refractory material with the furnace walls separated into selective zones to facilitate quick heat transfer at a pre-determined rate with means for temperature control and continuous monitoring of progress of temperature across walls and the differential temperature gradient.
Another important object of the present invention is to rationalize the uniform heating rate of the coal and coal blend mass and to avoid heat loss from furnace
5
wall in order to achieve an energy optimized device consuming very little electrical energy for carbonization process.
SUMMARY OF THE INVENTION:
The basic aspect of the present invention is therefore directed to a pilot furnace adapted for controlled carbonization mechanism of coal and coal blend such as to favour controlled generation of quality coke comprising
means for monitoring and uniform temperature control in the furnace such as to heat the coal/coal blend in the predetermined uniform manner from the walls of the oven to achieve consistency in character of coke produced throughout the oven;
thermocouples means provided to monitor-(i) progress of temperature across the wall and (ii) differential temperature gradient;
means to monitor the rate of evolution of volatile matter based on the wet loss of the coal/blend charge with respect to time;
means to monitor the internal oven gas pressure and controlling the desired internal oven pressure;
means for maintaining desired soaking temperature for the coke produced;
and
a PLC based controller operatively connected favouring the controlled
carbonization.
A further aspect of the present invention directed to said pilot furnace adapted for controlled carbonization comprising
6
Means for uniform temperature control in six zones of the furnace separately through PLC, such as to heat the coal/coal blend in the predetermined uniform manner from both the walls of the oven to achieve consistency in character of coke produced throughout the oven;
auxiliary thermocouple means placed from the coke side of the furnace door adapted to monitor-(i) progress of temperature across the wall and (ii) differential temperature gradient can be measured;
means for determining the rate of evolution of volatile matter from the wet loss curve for the coal/blend charge with respect to time and measured by load cell connected to PLC;
pressure transmitter means adapted for monitoring and measuring the internal oven gas pressure operatively connected to the butterfly valve mounted on the outgoing pipe and actuated by a step motor receiving signal from PLC based on the response of said pressure transmitter;
PLC controller means for efficient control on inside pressure and uniform heating at all positions operatively connected to pressure transmitter and thermocouples on selective locations in the said furnace to achieve uniform carbonization conditions all through the oven;
means for maintaining desired soaking temperature for the coke produced in a batch/charge for required time duration till the next blend is made ready for charging.
According to a still further aspect of the present invention directed to a pilot furnace adapted for controlled carbonization, adapted to be operatively associated with dry and/ or mixed (dry and wet) quenching facility in a hermetically sealed chamber having means for blowing Nitrogen from beneath the coke mass ;
7
said hot coke chamber is mounted in another chamber having side gaps for the passage of forced cooling air draft from a blower for external cooling of said hot coke mass;
means to study effect of pressure cooling efficiency vis-a-vis the coke properties;
means for providing storing historical trend for all carbonization parameters.
A still further important aspect of the present invention directed to a pilot furnace adapted for controlled carbonization comprising means for measuring the relative rate of evolution of inherent moisture of coal/coal blend, moisture of coal added separately and volatile matter for the entire duration of carbonization process.
According to a further aspect of said pilot furnace adapted for controlled carbonization, comprising refractory materials favoring quick heat transfer to the coal/blend charge at a predetermined uniform rate through out the oven, comprising hot face refractory and said six separate zones of the furnace built up with Silicon Carbide Nitride bonded slabs of desired thickness for quick heat transfer from heating zone to the wall.
According to yet another aspect of the pilot furnace of the present invention, adapted for controlled carbonization wherein the heating of the furnace is carried out by straight in diameter silicon carbide heating elements placed vertically.
According to another aspect of the present invention directed to said pilot furnace adapted for controlled carbonization, wherein the furnace is insulated to avoid loss of heat in the environment and is energy optimized, consuming very little energy for the entire carbonization process for a coal charge.
8
A still further aspect of the present invention directed to a pilot furnace adapted for controlled carbonization, comprising means for generating and recording historical trend of the carbonization pattern and is equipped with an in-built fault finding system.
According to yet another important aspect of the present invention directed to a process for controlled carbonization of coal and coke, in said pilot furnace already described, comprising the steps of-
monitoring and uniform temperature control in the furnace such as to heat the coal/coal blend in the predetermined uniform manner from the walls of the oven to achieve consistency in character of coke produced throughout the oven;
using thermocouples means to monitor-(i) progress of temperature across the wall and (ii) differential temperature gradient;
monitoring the rate of evolution of volatile matter based on the wet loss of the coal/blend charge with respect to time;
monitoring the internal oven gas pressure and controlling the desired internal oven pressure;
maintaining desired soaking temperature for the coke produced; and
using said PLC based controller operatively connected for determining the controlled carbonization.
A still further aspect of the present invention directed to a process for controlled carbonization of coal and coke, comprising the steps of-
9
feeding a small proportion of coal charge preferably of about 30 kg coal/coal blend having about 2% to 10 wt% of moisture and 20-30wt % of Volatile matter, in said pilot oven;
heating of coal/blend in said pilot furnace to soften at about 400°C-460°C and obtaining coke at around 1000°C through carbonization process comprising various reactions such as polymerization, co-polymerization, poly-condensation cracking and the like;
uniform temperature controlling the six selective zones of the two walls of pilot furnace separately through PLC controller operatively connected to thermocouples; to achieve uniform carbonization all through the oven by monitoring-(i) progress of temperature across the wall, and (ii) differential temperature gradient that is measured;
uniform positive pressure level is maintained and monitored inside the oven and at center of coal mass through out the carbonization period by cooperative functioning of pressure transmitter, PLC and butterfly valve mounted on outgoing pipe;
relationship between different rate of gas evolution with time and pressure providing for better understanding of carbonization process such that a fingerprint is obtained for a particular coal blend;
measuring the movement of the plastic layer inside the coal mass in the furnace during the carbonization;
weight loss of the bulk coal sample is measured by load cell connected to PLC and the rate of evolution of volatile matter, determining the carbonization mechanism and characterizing the coke in terms of its physical and chemical properties, obtained from the weight loss curve with respect to time.
10
According to yet another aspect of the present invention directed to a process for controlled carbonization of coal and coke wherein said
- carbonization period of 4.5 hrs to 5.5 hrs is estimated based on industrial carbonization process in slotted oven;
- coke obtained, following the above steps, from a charge of 30 kg coal having 2-10wt% of moisture and 20-30wt % of volatile matter by straight coal/blend carbonization range between 21kg to 24 kg.
A further aspect of said process for controlled carbonization of coal and coke wherein said process comprises
- after the hot coke is placed into the dry/wet quenching facility, the Furnace is maintained at a specified temperature of about 850°C, till the next blend is ready for charging;
- dry/wet or mixed quenching of the carbonized coke at 1000°C by preferred rapid cooling using nitrogen flow from beneath the hot coke cake in a hermetically sealed chamber avoiding coke burning by atmospheric oxygen to obtain desired hardness of coke ; cooling of coke is also performed externally by blowing air through the flow passages of a surrounding chamber.
A still further aspect of the present invention directed to a process wherein the historical trend of the all carbonization pattern comprising all the parameters, is generated and maintained.
Present invention and its objectives and advantages are described in greater details with reference to accompanying non-limiting illustrative figure.
BRIEF DESCRIPTION OF THE FIGURE:
Figure 1A: is the illustration of the facility layout for the best embodiment of the pilot coke oven according to the present invention;
11
Figure IB: is the illustration of main furnace assembly of the present invention showing its different components and their locations.
Figure 1C: is the illustration of coke quenching trolley assembly used for coke making facility in pilot furnace;
Figure ID: is the illustration of the charging hopper for charging coal and coal blend in pilot furnace;
Figure IE: is the illustration of the Gas burning assembly in the pilot coke oven;
Figure IF: is the illustration of the Pusher assembly for the pilot coke oven;
Figure 2: is the illustration of weight loss curve for coal charge with respect to time obtained for complete carbonization of a given coal/blend sample to obtain coke of desired characteristics.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING FIGURE:
The present invention is thus directed to a coal carbonization pilot furnace (PF) developed to determine the carbonization mechanism of coal and coal blend and also for quick characterization of coal and coke, with superior control on process parameters to ascertain desired properties of coke from given character of charge of coal and coal blend, in an energy optimized process.
Reference is invited to accompanying Figure 1A to IF wherein importantly, the pilot furnace (PF) of the present invention is adapted for determining the mechanism of carbonization in a way so that by following same procedure of control on operating parameters, same/similar coke quality is produced in the industrial coke oven of slotted type.
12
To achieve uniform heating of coal mass at all locations within the carbonization furnace of the present invention, the furnace involve dividing the heat propagating walls into six selective zones (Wl to W6), each provided with temperature control means through thermocouples (TC) installed at these six locations and relevant data collected and processed by Programmable Logic (PLC) controller on continuous basis. The auxiliary thermocouples(ATC) are placed from the coke side of the oven door for monitoring of - (i) Progress of temperature across the wall and (ii) Differential temperature gradient measurements. These are significant factors for assessing the carbonization process.
Another unique feature of the pilot carbonization furnace of the present invention is the measurement of rate of weight loss of the coal mass sample due to evolution of volatile matter during coal carbonization, which is a determining step for knowing the mechanism. This measure of weight loss of bulk coal sample is achieved with the help of a load cell (LC) connected to PLC. Accompanying Figure 2 illustrates graphically the rate of weight loss due to evolution of volatile matter can be determined from the weight loss curve (WLC) with respect to time. This rate normally varies from one coal sample/blend to the other. The physical and chemical properties of the coke produced depend on the rate at which evolution of volatile matter takes place. This observation in the pilot oven also can be applied in determining the mechanism of carbonization process in industrial conditions. Moreover the relative rate of evolution of moisture of the coal added separately, inherent moisture of the coal/coal blend and volatile matter in the span of entire carbonization time can be measured.
Moreover, in the above pilot carbonization furnace of the invention, the same provides for the measurement of the internal gas pressure with the help of pressure transmitter (PT), which is related to the rate of evolution of moisture and volatile matter from the hot coal mass. The relationship between different rate of gas evolution with time and pressure can give better understanding of carbonization process and a fingerprint can be obtained for a particular coal blend.
13
The carbonization pilot furnace/oven (PF) of the present invention is further to maintain the uniform pre-determined pressure at the desired level, usually a positive pressure head of 10-15 mm, of water column; through out the duration of the carbonization process and such oven pressure is maintained at desired level and monitored by means of a pressure transmitter and the butter fly valve (BV) connected to the outgoing pipe(OP) on the oven top. The said butterfly valve(BV) is operatively connected to a stepper motor(MT) and actuated based on the PLC controller. The said butterfly valve receives signal from the pressure transmitter through PLC for required percentage opening keeping the oven pressure at a pre-decided value, as already indicated, that favour desired coke characterization.
The weight capacity of the furnace has been further selectively decided preferably at 30 kg of coal charge at a time. The volatile matter of the coal ranges from 20 to 30 % and therefore the coke obtained from 30 kg coal charge of straight coal carbonization and coal blend would range between 21 to 24 kg of coke. In smaller proportions of coal blend, crushing will be uniform with 30 kg coal charge. Mixing of moisture as per the plant condition will also be homogeneous.
The pilot furnace, of 30 kg coal charge capacity, for determining the carbonization mechanism of coal and coal blend of the present invention is also associated with dry quenching facility where the hot coke mass at temperature more than 1000°C is pushed by a pusher ram from the furnace into a chamber. This chamber(HC) is hermetically sealed for avoiding coke burning from atmospheric oxygen. In addition this facility provides means for cooling of the hot cake of coke with the help of nitrogen flow beneath the hot coke cake. Thus, in the present process the coke mass is cooled very quickly and the coke produced is of better quality from strength point of view. The cooling of hot cakes of coke is also done externally by a blower(BL) placed beneath the hot coke chamber. The hot coke chamber is mounted in another chamber providing side gaps in between, for passage of forced cooling. Provisions are also made to study the effect of pressure cooling on cooling efficiency of coke vis-a-vis the coke properties achieved. Provisions are also
14
possible in the present set up to follow mixed quenching, comprising both dry and wet quenching facilities.
Also, the furnace of the present invention has been selectively obtained of refractory material adapted for quick heat transfer at a pre-determined rate. Importantly, the heating rate is found to be very important from the carbonization point of view where the entire coal/coal blend are required to be heated uniformly throughout the oven. For such purpose, hot face refractory(HFR) and the wall of six separate zones are built up with silicon carbide nitride bonded slabs of thickness suitable for quick heat transfer from heating zone to the wall. Heating of the coal and coal blend in the furnace is carried out using selectively straight in diameter silicon carbide heating elements(HE) placed vertically. The above features of the furnace thus enable the uniform heating of the coal and coal blend in the pre-determined rate from both the side walls of the oven and that the continuous operation of the furnace will not hamper the walls and the life of the heating elements. Coke produced in this manner will be thus consistent through out the oven.
With the afore described process control measures and continuous monitoring of the desired parameters in the pilot furnace of the present invention, the carbonization period in the pilot furnace has been achieved at a range of 4.5 to 5.5 hours, founded on calculations that favour industrial carbonization process carried out in coke ovens, of slotted type. After the carbonization process, the heating at specified temperature of about 800°C is usually maintained through out the time till the next blend is ready for charging.
Importantly also the said pilot furnace being adapted for preventing any loss of heat from the furnace wall to the outer environment, is found to be an energy optimized furnace consuming very little electrical energy for maintaining the rate of heating rate of coal charge and holding the specified temperature till next charge.
15
Moreover, apart from the control measures, in the pilot carbonization furnace, in respect of uniform rate of heating of coal mass all through the furnace and maintaining and monitoring, steady temperatures at desired level and for uniform furnace pressure through out the carbonization process and center coal mass pressure etc., by adapting said PLC controller, thermocouples(TC) in six selective zones, pressure transmitters(PT) and auxiliary thermocouples(ATC) on oven door, the control on carbonization achieved by way of the present invention also provides for historical trend analysis for all the carbonization parameters and an in-built fault detection for wrong parameter values that may lead to process failure and poor quality of coke.
It is, therefore, possible by utilizing the pilot furnace of the present invention for determining the mechanism of carbonization to achieve coke characterization of desired properties from given sample of coal and coal blend at a faster rate in a fully controlled environment on the deciding parameters in an energy optimized manner, which can be replicated in the real life situation in industrial carbonization process in coke oven of slotted type with improved productivity and consistent quality at less cost. The comparative strength of the (CSR) of coke obtained from 250kg and 30 kg carbonization oven, with dry as well as wet quenching are illustrated in the accompanying Table 1.
16
TABLE 1:

SI. Coal Blend Coke from 250kg Coke from 250kg
No. carbonization Furnace with carbonization Furnace with
wet quenching wet quenching

Type % CRI CSR CRI CSR
1-1 IMP
PRIME
MEDIUM 50 40 10 25 58 22 62
2 IMP
PRIME
MEDIUM 60 30 10 24 60 23 63
3 IMP
PRIME
MEDIUM 70 20 10 23 62 21 65
4 IMP PRIME 50 50 23 61 20 66
5 IMP PRIME 60 40 21 63 20 67
6 IMP PRIME 70 30 19 65 18 70
The coal carbonization pilot experimental furnace of the invention thus would provide for quick characterization of coal and coke and also to determine the carbonization mechanism of coal and coal blend, with superior control on process parameters to ascertain desired properties of coke from given character of charge of coal and coal blend, in an energy optimized process. Importantly, the pilot furnace for coal carbonization of the invention is adapted to achieve faster carbonization process with efficient control on inside pressure and uniform heating at all positions through PLC controller means operatively connected to pressure transmitter(PT) and thermocouples(TC) on selective locations in the said furnace, to
17
achieve uniform carbonization conditions all through the oven. Further, the PLC control is adapted to achieve predetermined uniform rate of heating of the entire coal mass at all locations of the furnace/oven by dividing the furnace inner wall surfaces into six zones and continuous monitoring thereof through thermocouples(TC) selectively installed and six thermocouples selectively placed on the said wall locations and four auxiliary thermocouples placed on the coke side of the oven door(OD), to monitor temperature distribution across the furnace wall and to measure differential temperature gradient, respectively.
Importantly also, the process of carbonization in the pilot oven/furnace of the invention is further provided with means to generate historical trend of the carbonization pattern in terms of known variable parameters.
The invention would thus provide for a pilot furnace adapted to rationalize the uniform heating rate of the coal and coal blend mass and avoid heat loss from furnace wall in order to achieve an energy optimized device consuming very little electrical energy for carbonization process as well as maintaining desired specified temperature for effective carbonization.
Advantageously, the pilot experimental furnace for carbonization with PLC control, of the invention is further provided with an in-built system for fault detection in case of any failure of process so that the corresponding reason/s can be identified and corrective action be taken.
18
We Claim:
1. A pilot furnace adapted for controlled carbonization mechanism of coal and
coal blend such as to favour controlled generation of quality coke comprising
means for monitoring and uniform temperature control in the furnace such as to heat the coal/coal blend in the predetermined uniform manner from the walls of the oven to achieve consistency in character of coke produced throughout the oven;
thermocouples means provided to monitor-(i) progress of temperature across the wall and (ii) differential temperature gradient;
means to monitor the rate of evolution of volatile matter based on the wet loss of the coal/blend charge with respect to time;
means to monitor the internal oven gas pressure and controlling the desired internal oven pressure;
means for maintaining desired soaking temperature for the coke produced;
and
a PLC based controller operatively connected favouring the controlled
carbonization.
2. A pilot furnace adapted for controlled carbonization as claimed in claim 1
comprising
Means for uniform temperature control in six zones of the furnace separately through PLC, such as to heat the coal/coal blend in the predetermined
19
uniform manner from both the walls of the oven to achieve consistency in character of coke produced throughout the oven;
auxiliary thermocouple means placed from the coke side of the furnace door adapted to monitor-(i) progress of temperature across the wall and (ii) differential temperature gradient can be measured;
means for determining the rate of evolution of volatile matter from the wet loss curve for the coal/blend charge with respect to time and measured by load cell connected to PLC;
pressure transmitter means adapted for monitoring and measuring the internal oven gas pressure operatively connected to the butterfly valve mounted on the outgoing pipe and actuated by a step motor receiving signal from PLC based on the response of said pressure transmitter;
PLC controller means for efficient control on inside pressure and uniform heating at all positions operatively connected to pressure transmitter and thermocouples on selective locations in the said furnace to achieve uniform carbonization conditions all through the oven;
means for maintaining desired soaking temperature for the coke produced in a batch/charge for required time duration till the next blend is made ready for charging.
3. A pilot furnace adapted for controlled carbonization as claimed in anyone of claims 1 to 2 adapted to be operatively associated with dry and/ or mixed (dry and wet) quenching facility in a hermetically sealed chamber having means for blowing Nitrogen from beneath the coke mass ;
said hot coke chamber is mounted in another chamber having side gaps for the passage of forced cooling air draft from a blower for external cooling of said hot coke mass;
20
means to study effect of pressure cooling efficiency vis-a-vis the coke properties;
means for providing storing historical trend for all carbonization parameters.
4. A pilot furnace adapted for controlled carbonization as claimed in anyone of claims 1 to 3 comprising means for measuring the relative rate of evolution of inherent moisture of coal/coal blend, moisture of coal added separately and volatile matter for the entire duration of carbonization process.
5. A pilot furnace adapted for controlled carbonization as claimed in anyone of claims 1 to 4 comprising refractory materials favoring quick heat transfer to the coal/blend charge at a predetermined uniform rate through out the oven, comprising hot face refractory and said six separate zones of the furnace built up with Silicon Carbide Nitride bonded slabs of desired thickness for quick heat transfer from heating zone to the wall.
6. A pilot furnace adapted for controlled carbonization as claimed in anyone of claims 1 to 5 wherein the heating of the furnace is carried out by straight in diameter silicon carbide heating elements placed vertically.
7. A pilot furnace adapted for controlled carbonization as claimed in anyone of claims 1 to 6 wherein the furnace is insulated to avoid loss of heat in the environment and is energy optimized, consuming very little energy for the entire carbonization process for a coal charge.
8. A pilot furnace adapted for controlled carbonization as claimed in anyone of claims 1 to 7 comprising means for generating and recording historical trend of the carbonization pattern and is equipped with an in-built fault finding system.
21
9. A process for controlled carbonization of coal and coke, in a pilot furnace as
claimed in any one of claims 1 to 8, comprising the steps of-
monitoring and uniform temperature control in the furnace such as to heat the coal/coal blend in the predetermined uniform manner from the walls of the oven to achieve consistency in character of coke produced throughout the oven;
using thermocouples means to monitor-(i) progress of temperature across the wall and (ii) differential temperature gradient;
monitoring the rate of evolution of volatile matter based on the wet loss of the coal/blend charge with respect to time;
monitoring the internal oven gas pressure and controlling the desired internal oven pressure;
maintaining desired soaking temperature for the coke produced; and
using said PLC based controller operatively connected for determining the controlled carbonization.
10. A process for controlled carbonization of coal and coke as climed in claim 9
comprising the steps of-
feeding a small proportion of coal charge preferably of about 30 kg coal/coal blend having about 2% to 10 wt% of moisture and 20- 30% of volatile matter, in said pilot oven;
22
heating of coal/blend in said pilot furnace to soften at about 400°C-460°C and obtaining coke at around 1000°C through carbonization process comprising various reactions such as polymerization, co-polymerization, poly-condensation cracking and the like;
uniform temperature controlling the six selective zones of the two walls of pilot furnace separately through PLC controller operatively connected to thermocouples; to achieve uniform carbonization all through the oven by monitoring-(i) progress of temperature across the wall, and (ii) differential temperature gradient that is measured;
uniform positive pressure level is maintained and monitored inside the oven and at center of coal mass through out the carbonization period by cooperative functioning of pressure transmitter, PLC and butterfly valve mounted on outgoing pipe;
relationship between different rate of gas evolution with time and pressure providing for better understanding of carbonization process such that a fingerprint is obtained for a particular coal blend;
measuring the movement of the plastic layer inside the coal mass in the furnace during the carbonization;
- weight loss of the bulk coal sample is measured by load cell connected to PLC and the rate of evolution of volatile matter, determining the carbonization mechanism and characterizing the coke in terms of its physical and chemical properties, obtained from the weight loss curve with respect to time.
11. A process for controlled carbonization of coal and coke as clamed in anyone of claims 9 or 10 wherein said
23
- carbonization period of 4.5 hrs to 5.5 hrs is estimated based on industrial carbonization process in slotted oven;
- coke obtained, following the above steps, from a charge of 30 kg coal having 2-10wt% of moisture and 20-30 % of volatile matter, by straight coal/blend carbonization range between 21kg to 24 kg.
12. A process for controlled carbonization of coal and coke as clamed in anyone
of claims 9 to 11 wherein said
- the coke after obtained after carbonization is heated at a specified temperature of about 800°C and is maintained till the next blend is ready for charging;
- dry/wet or mixed quenching of the carbonized coke at 1000°C by preferred rapid cooling using nitrogen flow from beneath the hot coke cake in a hermetically sealed chamber avoiding coke burning by atmospheric oxygen to obtain desired hardness of coke ; cooling of coke is also performed externally by blowing air through the flow passages of a surrounding chamber.
24
13. A process as claimed in anyone of claims 9 to 12 , wherein the historical trend of the all carbonization pattern comprising all the parameters, is generated and maintained.
14. A pilot furnace for determining carbonization mechanism of coal and coal blend and a process for carbonization of coal and coal blend with controlled parameters using the same substantially as herein described with reference to accompanying non-limiting illustrative figure.
The present invention relates to a Carbonization Furnace for determining the carbonization mechanism of coal and coal blend with adequate control on carbonization process parameters adapted to achieve desired quick characterization of coal and coke. The pilot furnace is preferably adapted to accommodate about 30 kg charge of coal and coal blend for carbonization with controlled uniform temperature and internal gas pressure using Thermocouples(TC) and pressure transmitter (PT) through PLC on continuous basis, to favour desired rate of heat transfer to and from walls inside the oven and also for post-carbonization dry and or wet quenching facility, for rapid cooling of coke, to instill desired strength properties. The carbonization mechanism would enable maintaining historical trends for all vital carbonization parameters with an in-built fault finding system. Thus the pilot furnace would optimize energy consumption for quick characterization of coal and coke and the experimental determination of mechanism of carbonization, favoring obtaining desired coke characteristics in real plant scale operation, and is therefore directed to have wide industrial applicability and use.