Claims:We Claim:

1. A coke dry quenching(CDQ) system including negative pressure in coke discharging zone enabling dragging atmospheric air into the system comprising:

said coke discharging zone including coke chamber, slide gate, and working zone ;
a top suction line operatively connected to said coke discharge zone such that leakage gases including hot hazardous gases from said coke chamber are drawn out of said coke discharging zone ahead of its entry into the working zone along with dragging in of ambient air into the working zone for better working conditions in said coke discharging zone.

2. A coke dry quenching(CDQ) system as claimed in claim 1 wherein said top suction line is operatively connected to slide gate cover/dust chute on top of said working zone at one end and a suction pressure source/vacuum pump at other end.

3. A coke dry quenching(CDQ) system as claimed in anyone of claims 1 or 2 comprising
a controlling ball valve installed on said suction line to operatively connect it to said vacuum pump/suction pressure source as and when required;
a vacuum gauge to measure and indicate the negative pressure created inside coke discharging zone through said suction line;
openable manhole cover/inspection hole on Vibrofeeder casing to allow entry of ambient air coming through manhole into coke discharging zone by suction effect under the vacuum created therein for faster driving out of hot and hazardous gases and reduce oxygen deficiency to desired level to enable carrying out repair/replacement /maintenance of any one or more of equipments like Discharging chute, Vibrofeeder casing and Rotary Seal Valve.

4. A coke dry quenching (CDQ) system as claimed in anyone of claims 1 to 3 wherein said top suction line is selectively operable in isolation or in combination with the existing dedusting system connected to Vibrofeeder casing to create required negative pressure in discharge zone.

5. A coke dry quenching (CDQ) system as claimed in anyone of claims 1 to 4, wherein said top suction line draws hot and hazardous gases and normalize deficient oxygen level within a short period even when the cooling nitrogen gas is in circulation through the CDQ plant which is still operating.

6. A method for driving out hot and hazardous gases flow current in coke discharging zone of coke dry quenching(CDQ) system to reduce break down timings and for safe working involving the system as claimed in claims 1 to 5 comprising

closing slide gate and stopping the rotary seal valve before under taking any maintenance work in coke discharging zone;
purging with nitrogen in coke discharging zone;

operating the top suction line connected to slide gate in action either alone or in combination with existing suction line, by opening respective control valves to provide route for escape of CO, nitrogen or other hazardous gases with cooling nitrogen Gas Circulation Blower speed as low as possible;
Regulating suction in suction line as per pressure in quenching chamber such that new line suction pressure is greater than chamber pressure;

Along with allowing atmospheric air to enter the coke discharging zone for faster cooling and drop in temperatures for easy access and /or operation utilities.

7. A method as claimed in claim 6 comprising stopping purge fan before opening Manhole for proper sealing of rotary seal valve;
Opening manhole/inspection door of Vibrofeeder after ensuring a negative pressure inside manhole/inspection door;
Entering through manhole for required maintenance work after normalization upon checking CO level to be zero or within allowable limit and oxygen level as atmospheric level inside coke discharging zone;
Closing manhole after completion of maintenance job;
Isolating new suction line before opening slide gate;
Starting Purge Fan before starting Rotary Seal Valve;
Starting coke discharging as per regular sequence by controlling discharge rate with Vibrofeeder as per chamber parameters condition.

8. A method as claimed in claim 7 wherein said regulated suction pressure in the suction line is greater than chamber pressure.

9. A method as claimed in anyone of claims 6 to 8 wherein time taken for said normalization of CO level and oxygen deficiency level is in the range of 5 to 10 min, preferably 10 minutes.

10. A method as claimed in anyone of claims 6 to 9 wherein in case of suction falling insufficient with existing dedusting system, a separate vacuum pump is connected, which is capable to drag gases with new suction line.

Dated this the 9th day of July, 2016
Anjan Sen
Of Anjan Sen & Associates
(Applicants Agent)

, Description:FIELD OF THE INVENTION
The invention relates to a coke dry quenching (CDQ) system including negative pressure in coke discharging zone enabling dragging atmospheric air into the system to change the gas flow current for hazardous gases in coke discharging zone to make it free from High Level of CO Gas as well as to remove deficiency of oxygen by allowing entry of fresh atmospheric air through inspection hole/manhole of Vibrofeeder casing and a method of its implementation. The proposed system and method also makes area safer to carryout maintenance job as well as reduce breakdown timing for Coke Dry Quenching (CDQ) Plant by not allowing any hazardous gas to come into working zone by extracting all gases just below of slide gate and creating a reverse cycle of gases which will have only atmospheric air circulating through coke discharging zone. The system comprises a negative pressure/suction line connected to slide gate cover or dust chute through ball valve and pressure gauge, to extract the hazardous gas from the point of source and maintaining selective negative pressure in relation to circulating quenching gas pressure/chamber pressure so that fresh atmospheric air is allowed to enter into the discharging zone through Vibrofeeder inspection hole/manhole to cool down the temperature inside discharge zone to safe working limit in a very short period of time to enable engineers/technicians to carryout maintenance of CDQ equipments comprising particularly of Slide Gate, Rotary seal valve, Vibrofeeder casing and coke discharging chute, while plant is in operation and quenching gas(Nitrogen) is circulating through the plant.

BACKGROUND OF THE INVENTION

Traditionally dry quenching process is being adopted for the cooling of Coke produced from the Coke Oven Battery in Steel Plants. Previously water was used as cooling media to cool the hot coke which not only consumes large volume of water but also releases harmful pollutants which is also not permitted buy the government latest regulations. Also the hot gas generated from the quenching process is released to atmosphere without any commercial use.

Coke Dry Cooling Plant is a clean technology that uses gas (Nitrogen) instead of water in an enclosed system to cool the hot coke. The hot gas can be recycled to create electricity. As a result, money is saved from conserving electricity and pollution is reduced from lower emission of CO2 and other pollutants. So overall current trend of steel industry is to move towards CDQ/CDCP technology where current innovation made is highly useful.

In CDQ plant of applicants, the existing dedusting system comprised vacuum/suction line gas flow current connected to Vibrofeeder casing which was unable to handle gases effectively as route for gases was through working zone. Thus attending to breakdown of equipments in discharge zone mainly comprising of slide gate, Vibrofeeder, rotary seal valve and discharge chute were difficult and time consuming as well as unsafe for maintenance people.

In prior approach, there is always some positive pressure in coke discharging zone due to gases coming from slide gate as leakage, which is unavoidable without stopping plant for a long time (Plant shutdown lasted for few hours to days for making coke discharging zone completely free from hazardous gases even sometime more than this depending on type of job need to be carried out in coke discharging zone of plant).

According to prior set up, gas flow current for hazardous gases created by suction system goes through working zone and critical machine’s which is critical from safety point of view as well as takes more time for engineer’s to start maintenance job as temperature of gases remains too high to enter in coke discharging for CDQ plant.

Thus according to prior approaches, one of the main drawbacks in coke discharging zone was that it was not easily accessible to carry out hot jobs (such as welding and gas cutting which system frequently required in case of any breakdown) due to deficiency of oxygen and High CO gas and there was chances of formation of explosive gases due to confined space zone.

Another main drawback with prior approach is during repair/ replacement of machines in coke discharging zone. Sometime due to major problem in coke discharging zone, replacement of rotary seal valve or Vibrofeeder is required. In the existing system, the gas flow being routed through these machines, access to CDQ equipments was very difficult due to hazardous gases as well as due to high temperature of gases which use to come from chamber through slide gate as leakage.

Moreover existing vacuum/suction line(dedusting system) gas flow current was unable to handle gases effectively as route for gases was through working zone. In order to make access inside coke discharging zone, system required a delay to start job (starting from few hours hrs to more depending on plant condition and type of breakdown), causing loss of steam generation and dry quenched coke which further used to minimize productivity of plant.

Thus the basic technical problem of existing vacuum/suction line is that it was not possible to extract hot and hazardous gases from discharge zone of CDQ plant where the suction line is connected to Vibrofeeder casing as a cyclone type situation arises near manhole where mixing of hazardous gases happen with atmospheric air due to large volume of leaked gases, secondly tendency of coke discharging tray (Vibrofeeder tray) is to divert gases towards inspection door.

There has been thus a need in the operation of existing CDQ plant to provide a method and apparatus to create a negative pressure in coke discharging zone for coke dry quenching plant (coke oven) to quickly drive out hazardous gases, reduce temperature and allow entry of fresh air to enable to attend the breakdown of equipments in discharge zone in a fast safe and reliable manner.

OBJECTS OF THE INVENTION

The basic object of the present invention is directed to provide a coke dry quenching (CDQ) system including negative pressure in coke discharging zone enabling dragging atmospheric air into the system to change the flow path of hazardous gases away from the discharge zone and allow entry of fresh atmospheric air to ensure desired level of Oxygen availability for enabling people to attend breakdown in the discharge zone of CDQ plant.

A further object of the present invention is directed to provide a system and method to create required negative pressure in coke discharging zone for coke dry quenching plant (coke oven) to drive away hazardous gases, reduce temperature and ensure oxygen availability in discharge zone by connecting a negative pressure/suction line to slide gate cover or dust chute to remove hazardous gas from the point of source.

A further object of the present invention is directed to provide a system and method to create required negative pressure in coke discharging zone for coke dry quenching plant (coke oven) to drive away hazardous gases, reduce temperature and ensure oxygen availability by maintaining selective negative pressure in relation to circulating quenching gas pressure/chamber pressure to allow entry of atmospheric air into the discharging zone.

SUMMARY OF THE INVENTION

The basic aspect of the present invention is directed to a coke dry quenching (CDQ) system including negative pressure in coke discharging zone enabling dragging atmospheric air into the system comprising:

said coke discharging zone including coke chamber, slide gate, and working zone ;
a top suction line operatively connected to said coke discharge zone such that leakage gases including hot hazardous gases from said coke chamber are drawn out of said coke discharging zone ahead of its entry into the working zone along with dragging in ambient air into the working zone for better working conditions in said coke discharging zone.

A further aspect of the present invention is directed to a coke dry quenching(CDQ) system wherein said top suction line is operatively connected to slide gate cover/dust chute on top of said working zone at one end and a suction pressure source/vacuum pump at other end.

A still further aspect of the present invention is directed to a coke dry quenching (CDQ) system comprising
a controlling ball valve installed on said suction line to operatively connect it to said vacuum pump/suction pressure source as and when required;
a vacuum gauge to measure and indicate the negative pressure created inside coke discharging zone through said suction line;
controllable manhole cover/inspection hole on Vibrofeeder casing to allow entry of ambient air coming through manhole into coke discharging zone by suction effect under the vacuum created therein for faster driving out of hot and hazardous gases and reduce oxygen deficiency to desired level to enable carrying out repair/replacement/maintenance of any one or more of equipments like Discharging chute, Vibrofeeder casing and Rotary Seal Valve.

A still further aspect of the present invention is directed to a coke dry quenching (CDQ) system wherein said top suction line is selectively operable in isolation or in combination with the existing dedusting system connected to Vibrofeeder casing to create required negative pressure in discharge zone.

Another aspect of the present invention is directed to a coke dry quenching (CDQ) system, wherein said top suction line draws hot and hazardous gases and normalizes deficient oxygen level within a short period even when the cooling nitrogen gas is in circulation through the CDQ plant which is still operating.

A further aspect of the present invention is directed to a method for driving out hot and hazardous gases flow current in coke discharging zone of coke dry quenching (CDQ) system to reduce break down timings and for safe working involving the system as described above comprising

closing slide gate and stopping the rotary seal valve before undertaking any maintenance work in coke discharging zone;
Purging with nitrogen in coke discharging zone;
operating the top suction line connected to slide gate in action either alone or in combination with existing suction line, by opening respective control valves to provide route for escape of CO, nitrogen or other hazardous gases with cooling nitrogen Gas Circulation Blower speed as low as possible;
Regulating suction in suction line as per pressure in quenching chamber such that new line suction pressure is greater than chamber pressure;
Along with allowing atmospheric air to enter the coke discharging zone for faster cooling and drop in temperatures for easy access and /or operation utilities.

A still further aspect of the present invention is directed to a method comprising
Stopping purge fan before opening Manhole for proper sealing of rotary seal valve;
opening manhole/inspection door of Vibrofeeder after ensuring a negative pressure inside manhole/inspection door;
Entering through manhole for required maintenance work after normalization upon checking CO level to be zero or within allowable limit and oxygen level as atmospheric level inside coke discharging zone;
Closing manhole after completion of maintenance job;
Isolating new suction line before opening slide gate;
Starting Purge Fan before starting Rotary Seal Valve;
Starting coke discharging as per regular sequence by controlling discharge rate with Vibrofeeder as per chamber parameters condition.

Another aspect of the present invention is directed to a method wherein said regulated suction pressure in the suction line is greater than chamber pressure.

Yet another aspect of the present invention is directed to a method wherein time taken for said normalization of CO level and oxygen deficiency level is in the range of 5 to 10 min, preferably 10 minutes.

A further aspect of the present invention is directed to a method wherein in case of suction falling insufficient with existing dedusting system, a separate vacuum pump is connected, which is capable to drag gases with new suction line.

The above and other objects and advantages are described hereunder in greater details with reference to the following accompanying non limiting illustrative drawings.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

Figure 1: illustrates schematically an embodiment of existing Coke Dry Quenching (CDQ) Plant and the discharge zone/area where the invention is applicable.

Figure 1A: illustrates process flow diagram for conventional process implemented through the existing CDQ plant.

Figure 2: is the schematic illustration of an embodiment of old or existing system for handling hazardous gas flow in coke discharging zone for CDQ Plant.

Figure 3: schematically illustrates an embodiment of the system for handling hazardous gas flow in coke discharging zone according to present invention by creating negative pressure in discharge zone wherein the suction line is connected to slide gate dust chute in CDQ Plant with indication of hazardous gas flow path with dark arrow and atmospheric air entry path with dotted arrow.

Figure 4: schematically illustrates an embodiment to show in an enlarged view the exact location and particular equipment in discharge zone of CDQ plant where the new system has been implemented with Suction line from Slide gate casing or from dust chute connected to slide gate casing.

Figure 5: illustrates schematically the suction system wherein slide gate dust chute is connected with existing dedusting system with a suction pump/fan connection through dedusting system.

Figure 6: shows graphically (a) the saving in normalizing time by the new system for handling hot and hazardous gases in coke discharging zone as compared to the existing system ;(b) CO gas normalizing trend and (c) Oxygen normalizing trend with time for new system as compared to old system.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS

The present invention described herein comprises a coke dry quenching (CDQ) system including negative pressure in coke discharging zone enabling dragging atmospheric air into the system and method of handling hazardous gases in coke discharging zone to minimize time for attending breakdown as well as to make safe access for engineer to work for maintenance job.

Reference is first made to accompanying Figure 1 that illustrates conventional Coke dry quenching plant Layout. It includes a chamber, Primary dust catcher, boiler to extract heat from circulating gas, control valves and a gas circulating fan. Firstly CDQ plant receives hot coke from battery and cooling of coke is done in chamber by circulating nitrogen gas with the help of gas circulating fan. Heated gas includes some dust which is separated in Primary dust catcher and multicyclone. Heat from circulated gas is extracted by boiler which is further utilized for generating steam to run turbine for captive power generation.

The conventional process flow diagram for the existing CDQ plant operation is presented in the accompanying Figure 1A wherein the details of steps involved in conventional dry quenching of coke obtained from coke oven battery have been shown and wherein step 5 illustrates the area of application of the present invention in Cold coke discharging through discharging zone of CDQ Plant which Includes slide gate, Discharging chute, Vibrofeeder casing, and Rotary Seal Valve.

In old methodology coke discharging zone always use to remain contaminated with high CO level and deficient oxygen which affects normal hot jobs and use to take much more time than new methodology including risk of explosive gas formation due to confined space area.

Referring next to Figure 2 in existing design of utility model we have one line(8) connecting to dedusting system from Vibrofeeder casing(2). According to standard operating procedure, whenever we open manhole (3) of coke discharging zone, this existing Vacuum/dedusting line (8) taken into action for creating suction in coke discharging zone to suck all hazardous gases (such as High CO, Deficient oxygen, High Nitrogen etc) for creating safe working environment as well as to reduce breakdown or preventive maintenance time for Rotary Seal Valve as well as Vibrofeeder, including replacement of Rotary Seal Valve in case of breakdown.

It may be seen in Figure 2 that dry quenched coke comes from the coke chamber(1) to the slide gate(5) which is opened as per plant operation to allow passage of coke to the Vibrofeeder casing(2) for controlled discharge of coke at desired rate.
A rotary seal valve (4) is provided to perform the function of coke discharging at a control rate as well as perform the function of sealing to maintain pressure in chamber. The existing suction line (8) is connected to the Vibrofeeder casing (2) through a ball valve (7) to extract the hazardous gases and dusts being connected to existing dedusting system.

According to previous system and methodology (as shown in Figure 2) of gas flow current for hazardous gases during carrying any maintenance job in coke discharging zone with existing suction/vacuum pipeline system remained as follows into the system:-

Manhole of discharging zone
Discharging Chute Vibrofeeder Casing
Vacuum line / Dedusting Line

This takes lot of time to bring high CO level and deficient oxygen to normal working range which further reduces steam and dry coke productivity of CDQ plant.

With existing design as shown in Figure 2, there was always high CO Level and deficiency of oxygen in Coke discharging zone. Reason was leakage of gases from slide gate and limitation of existing design for handling those gases. There was always +ve pressure in coke discharging zone due to continuous leakage of gases from slide gate (source for gases is CDQ chamber which is always filled with hot coke). Previously it was very difficult, time consuming and highly unsafe to replace machine which comes in coke discharging zone (Vibrofeeder, Rotary seal valve as well as repairing of RSV liner etc.) and this required stopping of CDQ plant (stopping of cooling nitrogen gas circulation into the system)operation.

A principal feature of the present invention is to change flow of hazardous gas current so that coke discharging area in CDQ plant can be made easily accessible for hot jobs (such as welding, cutting etc). To achieve this modified system of handling hazardous gases has been introduced in CDQ plant by way of the present invention by creating negative pressure in the discharging zone.

Accompanying Figure 3 schematically illustrates an embodiment of the system for handling hazardous gas flow in coke discharging zone according to present invention by creating negative pressure in discharge zone wherein the suction line is connected to slide gate dust chute in CDQ Plant with indication of hazardous gas flow path with continuous arrow and atmospheric air entry path with dotted arrow. It is apparent from Figure 3 that a New Suction Line(9) ( Dia 200 mm) is connected at one end to the slide gate dust chute(6) which at other end is connected to the existing dedusting vacuum system through a Ball Valve(10) to Operate New Suction Line(DN200). A Vacuum Gauge(12) for New Line is installed to measure the line pressure. This new suction line (9) can work in combination or isolation with existing dedusting line(8) connected to Vibrofeeder casing as shown in Figure 2. With the introduction of the new system of handling gas, gas route will not allow any hazardous gas to come into working zone by extracting all gases just below of slide gate(5). Also it will create a reverse cycle of gases which will have only atmospheric air circulating through coke discharging zone which particularly include slide gate, Rotary seal valve, Vibrofeeder casing and discharging chute. As sufficient atmospheric air into system is now made available, so temperatures in working zone will be ambient temperature in a short span of time which eliminate problem of suffocation as well. Moreover, chances of formation of explosive gases due to deficiency of oxygen and High CO gas due to confined space zone are also avoided.

With new design of hazardous gas extraction system according to present invention, a new suction/vacuum line is provided (from Slide gate casing or slide gate dust chute depending on design of plant as shown in figure 4) which further changed the gas flow current for hazardous gases by sucking it before entry to coke discharging zone as illustrated below:

Hazardous Gases from chamber

Vibrofeeder Casing
Coke Discharging Zone Manhole New and Existing
(Atmospheric Air) Rotary Seal Valve (Vacuum /Dedusting line)

Accompanying Figure 4 illustrates schematically the new suction line and the hazardous extraction system according to the present invention with enlarged top view and side view of the slide gate dust chute(6) to which the new suction line(9) is now connected and the other end is connected to the existing dedusting system vacuum source/suction line common header.

Figure 4 represents the equipment (Slide Gate (5) as in figure 3) which is used for making change in existing design to tackle problem relating to hot and hazardous gas in discharge zone experienced in prior art. When slide gate is in closed position, whole casing get free space which is enough to provide passage for escape of gases. New vacuum line (9) is connected with dust chute (6) of slide gate casing. It can alternatively be connected directly to upper side or lower side of slide gate casing as per space availability in plant. New system of vacuum line is developed only to use when slide gate is in close position.

Accompanying Figure 5 illustrates schematically the suction system wherein slide gate dust chute is connected with existing dedusting system with a suction pump/fan connection through dedusting system to develop required negative pressure inside the discharge zone of CDQ plant.

Another advantage of the system according to the present invention is its simplicity and negligible investment. New changes can be made easily without changing any parameters of plant’s operation and no space constrains for implementing new system into action which can be seen in the accompanying drawings easily.

With new system, a significant temperature drop can be achieved easily in a very short time which is primary necessity in order to do any maintenance job in confined space for engineers during maintenance job within short span of time. This temperature drop is achieved in new design, as there is negative pressure in coke discharging zone which drags atmospheric air into the system. A negative pressure (vacuum/suction) ranging from 4 to 6 kpa is more than sufficient to create a negative cycle for atmospheric air to enter into coke discharging zone as well as to remove hot and hazardous gases from their generating source which depends on plant size and plant condition too.

A new SOP (Standard operating procedure) is also created to operate the new suction line as and when needed. The steps to carry out the method of driving out the hot gases and make entry of atmospheric air inside discharging zone to create favorable condition to undertake repair/maintenance work in coke discharge zone involving the new system, when CDQ plat is in operation are as follows:

Step:-1
Close slide gate (5) and in order to attain any Breakdown/maintenance work in coke discharging zone and stop Rotary seal valve (4).
Step:-2
Start Purging nitrogen in coke discharging zone for sometime (say 15 minutes as in regular operation usually do, it may vary according to size of plant). Take new vacuum line(9) or both new(9) as well as existing suction line(8) into action by opening respective control valves to provide route for escape of nitrogen and other gases in coke discharge zone.
Step:-3
Meanwhile bring Gas Circulation Blower speed as low as possible according to chamber (1) parameters along with Step 2.
Step:-4
Now regulate suction in new line as per pressure in chamber (new line suction (usually 4 kpa enough as size and volume of gases is not large)>chamber pressure).
Step:-5
Stop Purge Fan before opening Manhole (Purpose of purge fan is to provide air sealing to RSV by maintaining a positive pressure in drive and non drive side casing).

Step-6
Now start MANHOLE /INSPECTION door (3) opening but ensure 100% PPE (personnel protective equipment, especially BREATHING APPARATTUES) for people in surrounding area.
No doubt new system is consistent and effective, even then safety should always be given a priority (as coke discharging zone is a confined space entry).
Step-7
Ensure a negative pressure near manhole/inspection door (3) before entry as well as check level of CO (Make sure it is zero or within allowable limit and oxygen level as atmospheric level i.e. 20.95 %.)
Step:-8
If in case suction falls insufficient with dedusting system, a separate vacuum pump must be connected, this must be capable to drag gases with new suction line.
Step:-9
Now proceed for work to clear breakdown/maintenance job or replacement of equipment such as Vibrofeeder/RSV or liner plate etc or any hot jobs.
Step:-10
Close manhole (3) after completion of job.
Step:-11
Isolate new line (9) before opening slide gate (5).
Step:-12
Start Purge Fan before starting Rotary Seal Valve (4) as sealing of RSV is very important.
Step:-13
Now as per regular sequence start coke discharging by controlling discharge rate with Vibrofeeder as per chamber parameters condition.
Experimental Results:

The results of performance trial of the new system for driving out hot and hazardous gases along with entry of atmospheric air in the coke discharging zone of CDQ plant shows that there is minimum saving of 45 minute in Normalizing Activity with new system of gas flow (High CO level and Deficient Oxygen Normalizing time period) as compared to conventional practice which is critical from productivity point of view as well as from safety point of view. The trial data are presented in the following table 1.

Table 1:

Sl. No Activity Time for activity with old utility model(min) Time for activity with new utility model(min)
1 Slide gate closing
5 5
2 Nitrogen purging
15 15
3 Manhole opening
5 5
4 High Co Level And Deficient Oxygen Normalizing Time Period
50 5
5 Manhole closing(except foreign material removing time)
5 5

The comparison of performance of new system as compared to the existing system for normalizing CO and Oxygen level in discharge zone are presented in the accompanying Figures 6(a) to (c) wherein Figure 6(a) shows the graphically saving in time for normalizing by the new system as compared to old system. Figure 6(b) shows graphically CO gas level normalising in coke discharging zone with respect to time period with new and old extraction systems. It usually takes much longer time to bring CO level to zero level which is seen in graph with old system. Figure 6(c) shows graphically deficient Oxygen Level Normalizing time period for coke discharging zone with old methodology verses new methodology with respect to time. It usually takes much longer time to bring Oxygen level to normal level with existing/old system as compared to new system which can be seen in graph.

Present invention is implemented in such a way that it can utilize with and without previous system of hazardous gas sucking facility. Best way is to use both previous and new suction/vacuum pipe line simultaneously for getting more effective results as follows:-

1. Use existing system during nitrogen purging in coke discharging zone so that all coke dust get sucked without damaging any equipment.
2. After nitrogen purging both suction/vacuum pipelines, new and existing, must be used. When new line is put into action, a new gas flow current will be in system which will drag ambient air into the system which is required for doing jobs related to replacing of critical machines or doing hot jobs during breakdown.

The new system is particularly effective with following two conditions:-

1. In order to achieve sustainability of new gas flow current, pressure of new suction/vacuum line (generally named as dedusting line) must be greater than chamber pressure.
2. Layout for new design depend on plant’s site condition and design of coke discharging zone which must be taken into consideration for getting desired results.

It is thus possible by way of the present invention to provide a system for extraction of hazardous gases in discharge zone of coke dry quenching (CDQ) plant by creating negative pressure in discharge zone to make the area safer to carryout maintenance job as well as reduce breakdown timing for Coke Dry Quenching (CDQ) Plant by extracting all gases just below of slide gate and creating a reverse cycle of gases which will have only atmospheric air circulating through coke discharging zone. The system comprises a negative pressure/suction line connected to slide gate cover or dust chute through ball valve and pressure gauge, to extract the hazardous gas from the point of source and allow entry of fresh atmospheric air into the discharging zone through Vibrofeeder inspection hole/manhole to cool down the temperature inside discharge zone to safe working limit in a very short period of time to enable engineers/technicians to carryout maintenance of Rotary seal valve, Vibrofeeder and coke discharging chute, while plant is in operation and quenching gas(Nitrogen) is circulating through the plant. The system and method according to the present invention thus enable a steady, reliable and efficient operation of the CDQ plant with consistency which includes negligible risk involvement for equipment getting damaged and safety of people working in the area.