WO2016193788A1

WO2016193788A1 - System for the collection of fugitive emissions during coke transfer to the quenching tower and discharge onto the wharf

Info

Publication number: WO2016193788A1
Application number: PCT/IB2015/054198
Authority: WO
Inventors: Stefano PELUFFO
Original assignee: O.M.E.V. Srl
Priority date: 2015-06-03
Filing date: 2015-06-03
Publication date: 2016-12-08

Abstract

The present system, planned for plants producing coke by distillation of coal, allows to collect, besides the emissions produced during pushing, also the diffuse emissions produced on the quenching Car by the incandescent coke, during the path of the coke Guide machine to the quenching tower, and those produced by the coke just quenched during the path of the Car from the quenching tower to the discharge wharf. Such function is accomplished by a suitable movable Hood, independent from the pushing Hood fastened to the coke Guide, that translates in synchronism with the quenching Car, draws the emissions produced by the coke present on the Car and it conveys them, through the duct on which it runs, to the suction- filtering assembly.

Description

SYSTEM FOR THE COLLECTION OF FUGITIVE EMISSIONS DURING COKE TRANSFER TO THE QUENCHING TOWER AND DISCHARGE ONTO THE WHARF

Technical field

The invented system is intended for the use in plants producing coke by distillation of coal in order to convey the diffuse emissions produced, after coke pushing, during the phases of transfer of the coke present on the quenching Car.

Prior art

Coke pushing - Coke pushing is the final operation of the coking cycle; at the end of coking, the oven (111.1 fig.l pos.l) is still isolated from the external atmosphere and it is connected with the collecting main (pos.1.4) of the battery that conveys the raw coke gas developed during the distillation process.

The pushing sequence is divided in the following steps :

• positioning the Pusher machine (pos.2) and the coke Guide machine (pos. 3) at the chamber of the oven to be pushed;

• isolating the oven from the collecting main and opening the lid;

• opening the doors at both the sides (pos.1.1 and 1.2);

· pushing the coke on the quenching Car by means of the pushing ram (pos.2.1) present on the Pusher machine .

During the pushing phase the quenching Car (pos.8) slowly moves at the front of the coke Guide such to distribute the coke along the whole length of the Car.

At the end of pushing, by removing the pushing ram, by re-positioning the doors, by closing the lid of the ascension pipe (pos.1.3) and by re-opening the connection with the collecting main, the oven is ready for a new charging cycle.

The preponderant emission into the atmosphere during the pushing phase derives from the transfer of the coke from the chamber to the quenching Car, while lower emissions occur upon the opening of the lid and of the doors on both the sides of the oven and when translating the Car towards the quenching tower and then from the quenching tower to the discharge wharf.

Coke quenching - There are two methods for the quenching of incandescent coke: wet quenching and dry quenching.

By wet quenching the quenching Car transports the coke under the quenching tower. By spraying water the coke is drastically cooled down, from the temperature of about 1000 °C it goes to a temperature of about 80 °C. The steam generated in such process is released into the atmosphere by a suitable tower that represents the emission source to the atmosphere. An amount of water sprayed on the coke is not converted into steam but since it remains at the liquid state it is recovered and used again in the following quenching cycles, after decanting the coke dust. Simultaneously a water refilling allows the amount converted into steam and evaporated to be restored. At the end of the coke quenching, the Car moves at the predetermined discharge zone on the wharf and it deposits the quenched coke. During this movement still a given amount of steam comes from the Car which is wasted in the air. The coke on the wharf therefore is conveyed on the conveyor belt that sends it to the screening tower for the size screening selection. When dry quenching is applied, the quenching Car transports the hot coke into a vertical quenching chamber. The inert quenching gas circulates around the chamber, which is isolated from the atmosphere avoiding combustion, while it cools the coke down. The gas is cooled by a heat exchanger in order to recover thermal energy. The cooled coke is discharged on the conveyor belts that convey it to the selection plant.

Reduction of emissions during pushing

Several techniques have been developed for minimizing dust emissions at the coke side of the batteries during the pushing phase:

• Use of side covers from which the dust and gases are drawn and conveyed, through a duct, towards a bag filter.

• Use of coke Guide machines integrated with hoods, fixed suction duct and bag filter for purifying gases.

• Maintaining the coke in the oven for a suitable time and with a sufficient and homogenous heating such to obtain its complete distillation and such to avoid "green pushes".

• Use of suitable quenching Cars (above all used for dry quenching) that minimize the amount of coke exposed to the atmospheric air.

(ref. "Best Available Techniques (BAT)- Reference Document for Iron and Steel Production Industrial Emissions - Directive 2010/75/EU Integrated Pollution Prevention and Control - 2013") .

Drawbacks of currently used systems

The main system for collecting emissions upon pushing currently in use in coke plants (coke Guide Machine integrated with Hood) is limited to draw and convey the produced fumes and dusts exclusively from the moment when the doors of the chamber to be pushed are opened up to the complete transfer of the coke on the quenching Car, the period when such emissions are preponderant. For this reason the current systems provide suction Hoods operating at the coke Guide machine or as a single body therewith, not considering the emissions produced in the period when the Car just filled with incandescent coke is moved towards the quenching tower, and after quenching, when the Car with the coke translates from the quenching tower to the discharge wharfs.

All such emissions are part of the diffuse emissions, not conveyed and therefore not quantifiable.

The more and more severe regulations as regards pollution and public health require to eliminate such emissions and to convey them to treatment plants and to controlled points for the release in the atmosphere (stacks, chimneys etc.).

For example in the case of the company ILVA of Taranto the Ministry of the Environment has prescribed that the company, in accordance to paragraph 3.5.3 "Reduction of diffuse emissions" (prescription n.37) of the preliminary intermediate conclusive opinion, submits a study intended to evaluate the conveying of the diffuse emissions, today not conveyed, related to the phase of transfer of the coke from the pushing point to the quenching point, as well as from the quenching tower to the point of discharge on the belt.

The current hoods, both movable and integral with the coke Guide cannot be used for conveying said emissions. The movable Hoods have apertures interfacing with the coke Guide for the passage of the coke during pushing and therefore they cannot follow the quenching Car. Air would enter through such apertures limiting the fume suction or the fumes would go out from such apertures. In order to use Hoods fixed to the coke Guide machines it would be necessary to move the coke Guide for following the Car extending the time of the pushing cycle and with longer residence time of the incandescent coke on the Car (upon the end of pushing the coke Guide may move only after cleaning the frame of the oven and closing the oven by re-positioning the door) .

Suggested solution

In order to overcome the limits described above OMEV srl has planned a system collecting such emissions described below.

The innovation consists in dividing the collection system into two independent parts (see 111.1 fig.2 and ill.2), one dedicated exclusively to the pushing phase called as "Pushing Hood" (fig.3, 5 and 6 pos.4) , that moves integrally with the coke Guide machine (pos.3), but that can be easily disconnected from the coke Guide in use and fastened to the stand-by coke Guide, and the other one dedicated to the quenching Car (pos.8) that works is synchronism thereto called as "Movable motorized Quenching Car suction Hood" (fig.3, 5 and 6, pos .5) .

Both the Hoods stand and convey the fumes in the same suction duct (pos.6) through which they come to the suction- filtering plant (Ill.l fig.l pos.7).

When it is necessary to use an emergency coke Guide machine (in case of failure or maintenance of the one in use) the pushing Hood has to be disconnected from the coke Guide in use and fastened to the emergency coke Guide such to allow the Movable motorized Quenching Car suction Hood to travel up to near the stand-by coke Guide.

For operating each new collecting system has to be composed of the following parts (see Ill.l fig.l and 111.2 fig. 3, 4 ,5 and 6):

• N. 2 coke Guide machines (pos.3) (of which one operating and one as a stand-by machine) arranged for the connection to the pushing Hood.

• N.l pushing Hood (pos.4) intended to draw the emissions during the phases of pushing and transfer of the coke from the distillation chamber to the quenching Car. Such hood is fastened to the coke Guide machine in use.

• N.l movable motorized Quenching Car suction Hood (pos.5) intended to draw all the diffuse emissions of the quenching Car during its path from the coke Guide to the quenching tower and from the quenching tower to the discharge wharf.

• N.l duct (pos.6) conveying the fumes from the collection zones to the suction- filtering assembly. Such duct acts also as a support and as a guide for the Hoods since it is equipped with suitable rails.

• N.l suction- filtering assembly (pos.7) composed of a cyclone (pos.7.1), bag filter (pos.7.2), fans (pos.7.3) and a stack for the discharge in the atmosphere (pos.7.4).

Movable motorized Quenching Car suction Hood

The movable motorized Quenching Car suction Hood (see 111.3) is the innovation of the system. It allows the quenching Car full of incandescent coke to be followed along the translation from the discharge point from the oven chamber to the quenching tower. The suction is guaranteed by a belt- lifter system integral with the support structures of the movable motorized Quenching Car suction Hood that allow, by lifting the rubber belt placed for covering the duct, the Hood and the suction duct to be connected. The translation of the movable motorized Quenching Car suction Hood is independent and in synchronism with the quenching Car. Before the Car enters the quenching tower the suction Hood stops in a parking position "outside" the quenching tower. Once the quenching operation ends the quenching Car leaves the tower by stopping under the movable motorized Quenching Car suction Hood. The residual steam is drawn by the suction Hood that, synchronized with the quenching Car, starts the common translation phase to the discharge point on the wharf. Once the operations discharging the coke on the wharf have ended, the movable motorized Quenching Car suction Hood + quenching Car assembly performs the translation towards the new oven to be pushed. Near the coke Guide the quenching Car proceeds with its travel towards the pushing position while the movable motorized Quenching Car suction Hood comes alongside the pushing Car integral with the coke guide.

The operation sequence is described below (see 111.4) .

A) start of pushing phase: the movable motorized Quenching Car suction Hood (pos.5) is alongside the pushing Hood (pos.4) . The pushing ram pushes the coke contained in the oven chamber, through the coke cage placed on the coke Guide, onto the quenching Car (pos.8) that starts to slowly translate for allowing it to be uniformly filled.

B) end of the pushing phase

C) stop of the quenching Car under the suction Hood. This allows the Hood and the quenching Car to contemporaneously start with a predetermined acceleration and speed. D) translation of the Car and the Hood towards the quenching tower .

E) stop of the quenching Car and Hood near the quenching tower (pos.ll).

F) movement of the Car under the tower and quenching the coke. Movement of the coke Guide machine with the relevant Hood and the Pusher machine to the new oven to be pushed.

G) Exit of the quenching Car from the tower and stop under the suction Hood for the connection.

H) translation of the quenching Car and of the Hood towards the coke discharge wharf.

I) translation of the quenching Car and of the suction Hood towards the coke Guide. The suction Hood comes alongside the pushing Hood integral with the coke Guide machine.

L) disconnection of the quenching Car from the suction Hood and its positioning in the initial pushing zone under the pushing Hood.

In 111.6 fig.14 the zone between a working location of the coke Guide (pos.3) and the quenching tower (pos.ll) is shown in plan view, with dotted hatching, where the diffuse emissions take place and are not drawn (only the Hood pos.4 is present that works at the coke Guide) while fig.15 shows, with cross hatching, the analogous zone where the emissions of the Car are drawn and sent to the filter (pos.7) by travelling the quenching Car suction Hood (pos.5)

The parts composing the movable motorized Quenching Car suction Hood are the following (see 111.3 fig.7, 8 and 9) :

• Hood and pipeline connecting to the duct (pos .5.1)

• Translation carriages with idler and drive wheels (pos.5.2)

• Bearing structure supporting the hoods (pos .5.3)

• Electrical power cable reel (pos.5.4)

• Electrical cabinet (pos.5.5)

• Automatic dampers for adjusting the air stream (pos .5.6)

• Belt-lifter (5.7)

• Electrical system

• Centralized lubrication system

• Electrical cabinet air-conditioning system. The hood (pos.5.1) may be made as a single body or may be composed of two hoods placed side by side each one supported by a structure (pos.5.3) made with welded and bolted profiles. Such structures are rigidly fastened above the translation carriages (pos.5.2) and are stiffened by means of braces. The individual hood or the hoods placed side by side with the relevant pipeline connecting to the duct allow fumes coming from the car to be collected and conveyed to the fixed duct (pos.6) and from this one to the filter. They are made with sheets and profiles obtained from sheets, welded and/or bolted. The hoods have an outer geometrical shape as a parallelepiped and for all the lower part on battery side they continue with a reduced sector that will allow, in case of need, them to slide under the coke Guide. The hood covers completely the area of the quenching Car intended to receive the coke. In the inner part of the hood, at a height defined by the lower border, shuttering panels can be mounted such to have a uniform suction on the whole collection surface or a gap may be created such to exclude or limit the suction in the central area and to concentrate it in the perimetral part. The translation carriages support the hood and allow it to translate on the duct. Each one of the two carriages travels between the rails of the duct by means of 4 wheels placed in the lower part (one of which is motorized) and two wheels placed on the upper part (one of which is motorized) . The upper wheels serve for opposing the eccentricity of the load due to the hoods placed overhanging with respect to the carriage. On the axle of the 4 driving wheels an orthogonal axis reduction gear is directly splined coupled to the self-braking electric motor. In order to obtain controlled accelerations and decelerations of the machine, as well as in order to obtain low speeds necessary for the centering on the quenching Car and in the area of the quenching towers, speed governors (frequency converters) are provided for each motor. The carriages are connected with each other by a hinged frame upon which the cable reel is placed. Inside each translation carriage a belt- lifter system is housed, that allows, by lifting the belt placed for covering the fume suction duct (pos.6) the latter and the hood to be connected. Such belt-lifter is composed of 4 idler pulleys, two of which equipped with containment skirting and a series of support rollers. Before the pipeline enters under the belt- lifter there is provided a butterfly damper that, driven by an electromechanical actuator, allows the air flow rate drawn by each hood to be opened, closed and adjusted if necessary.

Pushing Hood (fastened to the coke guide in use)

The pushing Hood (see 111.5) is integral with the coke Guide (pos.3) and it allows the emissions due to the phase pushing the coke from the chamber of coke ovens to the quenching Car to be drawn. Such Hood is dragged by the coke Guide on which it is installed.

A cable reel (pos.4.9) placed on the bearing structure (pos.4.1) of the pushing Hood provides electric power supply to the coke Guide.

The pushing hood is semi -automatically disconnectable from the coke Guide on which it is fastened and it can be placed again on the other coke Guide if it is necessary to carry out extraordinary maintenance operations or in case of failure of the coke Guide.

Such operation has to be carried out in a dedicated area (for example at the tower of the coal fig.13 pos.13), where the sliding bearings between hood and coke guide and the electric power supply are disconnected. By means of a bracket (fig.13 pos.12) to which two hydraulic cylinders are fastened (pos.12.1), the structure of the Hood above the coke Guide, after being disconnected from the coke guide itself, is raised enough to allow the coke Guide underneath to translate and to free the space for the stand-by machine. Now the structure of the Hood is lowered and the Hood is again connected with the coke Guide and the the electric power supply cables are subsequently connected. The movements of the coke Guide during such phases are made possible by generator sets integrated within the machines.

The parts composing the pushing Hood are the following:

· N.l bearing structure (pos.4.1)

• N.l hoods and pipeline (pos.4.2)

• N. 2 translation wheels (pos.4.3)

• N. 1 belt-lifter (pos.4.4)

• N. 1 automatic damper (pos.4.5)

· N. 1 cable reel (pos.4.6)

• N.l electrical system

• N.l lubrication system

The support of the bearing structure on the upper frame of the coke Guide is accomplished by n.2 sliding bearings (pos.4.7) that allow compensating the deviations between theoretical measurements and the real ones of the distance between centers and the difference in height of the rails of the coke Guide with respect to those of the suction duct (pos.6).

Above each sliding bearing the attachments are placed allowing the pushing Hood to be supported during the replacement of the coke Guide described above.

The hoods and pipeline are made with sheets and profiles obtained by sheet, welded and/or bolted made of steel with different thicknesses. The central hood has a parallelepiped geometrical shape with a height higher than that of the pushing cage placed on the coke guide. On the side of the central hood, in the upper zone there are two emergency stacks (pos.4.9) to allow fumes to be exhausted in case of failure of the suction- filtering systems. On each one of the two sides of the central hood two hoods are placed still with a parallelepiped geometrical shape but with a lower height, that allow what escapes from the suction of the central hood to be drawn.

On the bearing structure above the coke guide two further hoods are placed. The main one faces above the door of the oven chamber and it draws the fumes emitted by the door opening operation till the end of pushing, while the other one draws the fumes emitted by the door during the cleaning operation. Such fumes are conveyed towards the latter by the containment walls of the door cleaners present on the coke guide.

For the travel of the pushing Hood above the duct n.2 wheels are provided (pos.4.3).

A belt-lifter system is placed integral with the support structures of the hood which allows, by lifting the belt placed above the duct, the latter and the hoods to be connected. Such belt- lifter will be composed of n.4 idler pulleys, two of which equipped with containment skirting and a series of support rollers .

Before the pipeline enters under the belt- lifter there is placed a butterfly damper divided into 2 parts: the upper one (1/3 of the surface of the damper) is dedicated to the suction of the fumes above the door of the oven chamber and of those produced by the door during the cleaning operation, while the lower one (2/3 of the surface of the damper) is dedicated to the suction of the fumes collected by the central hood and by the two lateral ones during pushing. The opening/closure and adjustment of the upper and lower valve are carried out independently by n.2 electromechanical actuators.

Electrical system - the Hood is not equipped with its own electrical system but it houses some components of the coke guide machine.

Coke Guide machine - The coke Guide machine acts for conveying the coke, during pushing, from the oven chambers to the quenching Car.

The coke guide machine has to be arranged for fastening the pushing Hood and it has to allow the movable motorized quenching Car suction Hood to pass in case of use of the emergency coke Guide machine.

The main coke Guide machine and the emergency one must have the same characteristics. The coke Guide machine has to be made as having a single working position (after having positioned the machine on the oven the operations for opening-closing the oven, inserting the coke cage, cleaning the frame, cleaning the door, are carried out without moving the machine) .

The parts that compose the coke guide machine are the following:

· Bearing structure and auxiliary structures • n. 4 translation carriages each one composed of an idler wheel and a drive wheel.

• N.l Doorlifter (equipment for lifting door)

• N.l coke cage with fume suction side wall and movable fume containment walls connecting to the pushing hood

• n.l frame cleaner (equipment for cleaning the frames of the chamber, the support seat of the door) .

• N.l door cleaner (equipment for cleaning doors) with fume suction side walls.

• n. 1 arrangement for the attachment of the pushing Hood

• Electrical cabinet, hydraulic cabinet and operator room

• n.l electrical system

• n.l hydraulic system

• n.l air system

• n.l centralized lubrication system.

Brief description of the drawings

111.1: Fig.l is the cross-section of a battery, while Fig.2 is a partial cross-section of the battery where the quenching Car with the relevant suction Hood above it is pointed out.

111.2: Fig.3 is a longitudinal view of the movable motorized quenching Car suction Hood and of the pushing Hood placed side by side, Fig.4 is a cross-sectional view of the quenching Car suction Hood, Fig.5 is the cross-sectional view of the pushing Hood fastened to the coke Guide machine, fig.6 is the planimetric view of the hoods side by side.

111.3 quenching Car suction Hood: Pig.7 is the longitudinal view, Fig.8 is the cross-section view, Fig.9 is the planimetric view.

111.4 operating sequence of the movable motorized quenching Car suction Hood.

111.5 pushing Hood: Fig.10 is the longitudinal view. Fig.11 is the cross-section view, Fig.12 is the planimetric view. Fig.13 is a particular system for lifting the pushing Hood for replacing the coke Guide.

111.6 Fig.14 is the typical planimetric view of a current battery highlighting the area where the diffuse emissions produced by the coke on the Car take place (with dotted hatching). Fig.15 is the typical planimetric view of a battery highlighting the area where such emissions are collected by the movable motorized quenching Car suction Hood (cross hatching) .

Claims

1. System for collecting and conveying diffuse emissions after coke pushing, during its transfer to the quenching tower and relevant discharge on the wharf characterized in that the suction on the quenching Car occurs by means of a movable motorized Hood.

2. System according to the preceding claim, characterized in that the suction Hood of the quenching Car has a translation movement synchronized with that of the quenching Car.

3. System according to claim 1, characterized in that the operation of the suction Hood of the quenching Car is independent from that of the pushing Hood integral with the coke Guide.

4. System according to claim 1, characterized in that the suction Hood of the quenching Car may have a uniform suction on whole the surface by inserting therein shuttering panels or a perimetral suction.

5. System according to claim 1, characterized in that the pushing Hood may be easily disconnected from and connected to a coke Guide machine and another one, present on the same battery.

6. System according to claim 1, characterized in that the coke Guides are arranged for the rapid connection and disconnection of the pushing Hood.

7. System according to claim 1, characterized in that the movable motorized quenching Car suction Hood may be used both on plants with wet coke quenching and on plants with dry coke quenching.

8. System according to claim 1, characterized in that the coke Guide at rest with the cage placed towards the oven side and without the pushing Hood allows the movable motorized quenching Car suction Hood to pass.