02 Cokemaking Process (54 Slides)

Coke Oven View

DrawingDrawing MachineMachine

Charging Car

CokeCoke GuideGuide

Coke Oven View

Pyrolysis Physical Profile

Coking System

Swelling - Coking Pressure

Output of volatile material from coal and coke that is forming.

Rise of pressure inside the plastic layers, which pushes the coke against the wall and compresses the coal between them and the coke does not let the gas get out completely.

Ressolidification

Cracks

Ressolidification

Contraction

Coke detached from the wall

Contraction

Coke detached from the wall

Carbonification Time

Coke Oven Plant ViewCoke Oven Plant View

Coke

Oven

Plant

View

Pusher

Side

Coke

Side

Coke Oven Plant View


Charging

car

Pusher

Machine

Oven

Leveling

Bar

Quenching

Car

Blending

Coke

Guide

Piston

CokeCoke ChargingCharging

1-The Charging car is positionated to start charging.

2- Coal is loaded in the oven according a standard procedure.

3- The Charge is leveled by the leveling bar.

4- Completed coking process the coke oven doors are opened, the coke guide and quenching car are positioned.

5- The incandescent coke is pushed by the pusher machine.

Horizontal Horizontal FurnacesFurnaces BatteryBattery

The walls of a coke oven are not parallel.

The oven has a taper in the width of the oven, for ease of drawing operation.

(PS) (CS)

Taper

Taper


Coal Bunker

02 silos with capacity of 1500 t.

Feed system that distributes coal by rotating chute in two silos.

Level is controlled by the operator's control room.

Charging Car

The function of the charging car is put into the furnace the mixture of coal and control the furnace charge.

The load of coal is weighed and then the car turns to an empty oven. Under the command of the operator, the car sits on the oven you want, and after the transfer of its load, returns to the Coal Bunker where is made a new weighing.

Charging Car

Coke Oven Plant Equipments

Coke Guide Drawing Machine

Charging Car

Coke Oven Plant ViewCoke Oven Plant View


Coke Dry Quenching (CDQ)

Coke Dry Quenching (Coke Dry Quenching (GiprokoksGiprokoks))

Parameter CDQ Wet CDQ -

Wet

DI 15 -

150 83,4 79,6 3,8Reactivity JIS 16,7 23,5 6,8

Volatile Matter 0,42 0,75 0,33

Porosity 46,8 50,7 3,9

Average Size 62,5 64,7 2,2

Distribution (mm)+ 100+ 75

+ 50

+ 38

+ 25

+ 0 (zero)

4,921,8

40,0

23,1

7,8

2,4

7,925,0

40,9

16,2

5,3

4,7

3,03,2

0,9

6,9

2,5

2,3

Comparative Between Coke Dry Quenching and Coke Wet QuenchingComparative Between Coke Dry Quenching and Coke Wet Quenching

CDQ – Coke Dry Quenching

What is the Driven Force of the Coking Process:What is the Driven Force of the Coking Process:

The driven force is temperature.

Combustion is an oxidation reaction, whose processing agent is oxygen free

or combined, and has products such as CO2, H2O and heat.

The heating system can be divided in two units: the combustion chambers and regenerators (located underneath the ovens and walls of heating, recovering the sensible heat of the fumes).

The combustion gas is admitted at half of these chambers and the combustion is ensured by the introduction of preheated air. An upward combustion happens in these chambers. The other half of the chamber ensures the evacuation of descended smoke.

View – Coke Oven Plant

ByBy--product Battery Combustionproduct Battery Combustion

The rich gas (COG) or the mixed gas (COG + BFG) are taken from the by-product of the plant and / or gasometer.

The pipeline are designed to carry the appropriate volume of gas with supply pressure also suitable.

Physical

Events

During

Cokemaking

Process

(coke

oven

plant

–

slot)

Pyrolysis Thermal Profile

Time Curve

Cokemaking process

By-product oven Coke mass

Combustion chamber

Heating wall Heating wall

Positive pressure

Vertical line of cleavage

of coke mass

Horizontal front coking Horizontal front coking

Free zone

Conduction Conduction

ByBy--Products BatteryProducts Battery

ByBy--Products BatteryProducts Battery

Objectives: coke production with consistent high quality, appropriate thermal efficiency and low emission of contaminants in withdrawing.

Appropriate conditions for achieving the goals:

Homogeneous charge in terms of moisture, particle size and charge density

(which highlights the importance of coal preparation and charging techniques

of coal in coke oven).

At the end of the coking cycle, just before withdrawing, the temperature of coke

in the charge center (equidistant from the walls of heating) should be the

same (around 1050 oC).

In order to obtain uniform conditions of temperature inside the charge is

necessary to adjust and control the vertical and horizontal temperature

profiles of each and heating wall along the entire length of the battery.

Curves Curves ofof TemperatureTemperature RiseRise WithinWithin thethe Charge Charge ofof CokeCoke OvenOven

Coking Time (h)

Tem

pera

ture

(ºC

)

Wall

Middle

Stable production. Smallest possible change in production leads to an efficient operation. So it is better withdrawing stably and non-stop for shift changes, meal breaks etc..

Ovens properly completed. Leads to better production rates and lower energy consumption per tonne. It also reduces the space above the charge to the formation of naphthalene (good charging systems and adding oil helps to have well-filled ovens).

Maintenance and preservation.As in any plant a good maintenance / preservation (door frames and walls) is a indispensable prerequisite.

Consistency of the coal blend (formula, blending, particle size and moisture).Regulating the supply of gas so that combustion is complete and the amount of

excess air is equal to the practical minimum.

Correct adjust of heat to the whole heating wall in order to have uniform coking.

Optimum time of reversal. There is an optimum time in order to have the best efficiency. Each battery has its optimum time.

Efficient Operation of Coke BatteryEfficient Operation of Coke Battery


Regularity of withdrawing scale.

Maintaining of proper pressure balanceMeasurements and main controls. An important requirement for efficient operation is to measure and control the parameters that affect the process.


Heating control: Various methods are used to this control, with the common goal of stable operation (coking optimization and minimization of energy consumption).

Combustion control: it is essential that the products of combustion in the burnt gas be measured, especially CO and O2, if its value is known it assists in the proportion of the air/ gas for the burning and help to control the damper of the chimney. In order to achieve good control may be required individual adjustment of one or more ovens using portable analyzers.

Operational Control of Coke BatteryOperational Control of Coke Battery

Temperature ControlTemperature Control

1.

Control of the heating characteristics, temperature measurement along the walls (all the wall chambers are monitored) and average temperatures of the

battery (selected chambers, usually two per wall, are monitored).

Measures Objective : Distribution avaliation of the battery heating

2. Data presentation:

2.1. curve or graph of chamber temperature per individual oven.2.2. Graphic of battery average taperature.2.3. Battery temperature distribution.

Operational Control of Coke BatteryOperational Control of Coke Battery

Heating ControlHeating Control

1. Supply pressure of the heating gas.2. Heat imput.3. Heat input versus caloric value.4. Wobbe index versus the square root of difference pressure across the battery

Combustion ControlCombustion Control

1. Quantification of burnt gas.2. Burnt gas analysis (O2 e CO)

Battery Average Temperature

The temperature measurement of the hundreds combustion chambers would be laborious and no practical. What do you do? Measure thetemperature of some selected chambers (central chambers or fifthchambers from the coke side and pusher side of all walls except the end walls of the battery.)

Optical and infrared pyrometers (focused on the bottom of the chambers in smoke, in the space between the holes of gas and air or at the base of gas burner coke oven)

Temperature Crosswall Distribution

Due the width increase of the PS to the CS oven, the temperature also increases gradually in this direction (the purpose is that coking times are similar along the entire length of the oven).

The average temperature of the wall is obtained by the arithmetic average of its chambers, eliminating the measures of the extreme chambers (two CS and two PS).

Taper (function of the furnace tapering) is the temperature difference between the third and antepenultimate chamber wall. The taper is achieved by regulation of sliding bricks located in inlet air and gas holes at the base of the chamber through the holes of inspection on top of the battery.

Temperature Temperature CrosswallCrosswall DistributionDistribution

Tem

pera

ture

(ºC

)

Chamber

Battery 6m

Temperature of Extreme Chambers

Individual control by regulating the flow of air and gas for those chambers (the end of each regenerator).

The temperature of those chambers is lower for protection of metallic structures nearby, preventing formation of carbon deposit on the refractory of the doors and reducing the heat loss.

Vertical Distribution of Temperature

The more uniform distribution of temperature more uniform quality of coke.When the combustion is in only one stage (base of the chamber), the adjustment

of the vertical distribution is done acting on the calorific value of gas and in the excess of air (factors that determine the height of flame).

Hot top favors the formation of graphite and arising problems(difficulty of withdrawing, hanging, leaking doors, etc).

Temperature Vertical DistributionTemperature Vertical Distribution

Cok

ing

Tim

e (h

ours

)

Chamber Average Temperature (ºC)

Coking Rate ChargeCoking Rate Charge

Charge density of 820kg/m3

Coking heat of 400kcal/kg

Moisture of 10%

Wall thickness of 100mm

K = (σ/ t) (B/2)2

K

= coking index

σ

= charge density (t / m3)B = oven width

For more uniform the heating of the coke oven walls be, there is always irregular distribution of temperature inside the charge due the non-uniformity of charge density and differences in geometry of the oven that range from pusher side to coke side .

Additional time (may be a few hours) to amortize the deficiencies in the distribution of temperature, for the charge has not temperatures significantly lower at the end of the coking cycle.

Soaking TimeSoaking Time

Soaking TimeSoaking Time

As consequence, the mass of coke may not show uniform contraction and industrial practice shows lateral retraction ranged from 1 to 12 mm. If the temperature differences are really significant, part of the charge may not detach from the walls and the charge can only be withdrawing with difficulties or even stay hanged.

Charge contraction

Reasons for soaking time Amortization of differencesIn charge temperature

Coke quality

Operational security

Strength

Reactivity

2 4 6 8 10 12 14 16

Hours After Charging

Vert

ical

Con

trac

tion

(%)

2

4

6

8

10

Cok

e M

ass

Tem

pera

ture

(°C

)

200

400

600

800

1000

1

2

3

1

2

3

2 - Vertical Contraction (CS)

3 – Vertical Contraction (PS)

1 – Coke Mass Temperature

CharacteristicCharacteristic Curve Curve ofof Vertical Vertical CokeCoke ContractionContraction

Coke of Charge Coke of Charge TopTop

Source: VCom, Seminário

ABM 2004

0,80,9

1

1,15

0

0,2

0,4

0,6

0,8

1

1,2

Top Charging BriquetteBlending

Preheating StampCharging

Cha

rge

Den

sity

(t/m

3 )

Coke Oven Plant With Stamp ChargeCoke Oven Plant With Stamp Charge

The coke is transferred from the battery ramp to the blastThe coke is transferred from the battery ramp to the blast--furnace.furnace.

Appropriate and consistent crushing

SamplingUniformity levelDistribution of coal in the yardsStacking and withdrawingRemaining time

Efficient mixing, to facilitatethe interaction between the coals and avoidfluctuations in the composition of the mixture

Appropriate and consistent routine ofsilos filling.

Maintenance of minimumstock

Efficient proportioning ofcomponents coal.

Opening sequence of hopperscontinuous flow, and leveling controlcharge.

Determination of coking end point.

Well preserveds ovens and consistentConditions of heating.

Effective control of the quantity ofwater, duration of quenching and uniformallocation of water on the surfaceof the coke mass in the car.

Rota do carvão

AvaliationAvaliation ParametersParameters ofof CokingCoking CoalCoal

•Moisture•Ash•Volatile matter

•Rank•Maceral composition

•Rank•Size

•Rank

•Rank•Maceral composition•Size•Plasticity

Low content of sulphur, phosphorus and others elements.

•Low content of sodium, potassium and zinc.

COAL AS RECEIVED CRUSHED COAL

•New size

MISTURE


•Mixture formule•Size(80 a 85%< 7 #)

•Mixture formule•Average rank index•Maceral composition•Size•Plasticity

•Low content of sulphur, phosphorus and others elements.


COKEMAKING COKE BLAST- FURNACE

•Moisture release•Volatile evolution•Ash concentration

•High carbon content•Low ash content

•Volatile matter < 1%

•Low coking pressure•Suitable contraction

•FUEL

•REDUCER

•Provide carbon to pig iron.

•Coke oven dimension•Load moisture•Wall temperature•Coking rate•Coke handling

•Concentration of phosphorus and others elements content and reduction of sulphur content.

•Concentration of sodium, potassium and zinc content.

•Final temperature

•Suitable quenching

•Suitable size•Small size distribution•Strength

•Low content of sulphur, phosphorus and others elements.


•Low reactivity with CO2

•Low water content.

•Permeabilizer

•Not pig iron contaminant

•Not operation disturber.

+

+


•Rank•Maceral composition

•Rank

•Rank•Maceral composition•Size•Plasticity

Low content of sulphur, phosphorus and others elements.


•Average rank index

•Average rank index•Maceral composition

++

+

Documents

02 Cokemaking Process (54 Slides)