report - heat balance of a reheating walking beam furnace - vsp

HEAT BALANCE OF REHEATING WALKING

BEAM FURNACE

Submitted by

NAME: N.V.S.KALYAN ADMN. NO.: 2012JE1025

DEPARTMENT OF MECHANICAL ENGINEERING

INDIAN SCHOOL OF MINES, DHANBAD

Under the guidance of

N. VENUGOPALA RAO, AGM (M), EMP. NO: 116986, DEPT. MMSM, VISAKHAPATNAM STEEL PLANT.

VIZAG STEEL PLANT - MMSM CERTIFICATE

This is to certify that the Project Report on HEAT BALANCE

OF REHEATING WALKING BEAM FURNACE submitted by

NAME: N.V.S.KALYAN ADMN. NO.: 2012JE1025

COLLEGE: INDIAN SCHOOL OF MINES, DHANBAD

is a record of Bonafide work carried out by him, under the

guidance and supervision during the period of 18th MAY

2015 to 30th MAY 2015.

N. VENUGOPALA RAO,

AGM (M),

DEPT. MMSM,

VISAKHAPATNAM STEEL PLANT.

CONTENTS

INTRODUCTION - STEEL

WORLD STEEL STATISTICS

INDIAN STEEL INDUSTRY

VIZAG STEEL PLANT - RINL

MEDIUM MERCHANT AND STRUCTURAL MILL (MMSM)

INDUSTRIAL FURNACE

WALKING BEAM REHEATING FURNACE

THERMAL ANALYSIS OF THE FURNACE

OBSERVATIONS

CALCULATIONS

HEAT BALANCE SHEET

CONCLUSIONS

INTRODUCTION

STEEL

Steels are alloys of Iron and Carbon, widely used in

construction and other applications because of its high tensile

strength and low cost. The Carbon in typical Steel alloy may

contribute up to 2.1% of its weight. Varying the amount of

alloying elements, their formation in the steel either as solute

elements or as precipitated phases controls the qualities of

steel such as Hardness, Ductility and Tensile Strength.

For many thousands of years steel used to be produced

in Bloomery furnaces but after the efficient production

methods for Blister Steel and Crucible Steel in 17th century,

expansion of steel took extensively. With the invention of

Bessemer process in the mid-19th century, a new era of mass

produced steel began and this was followed by the

introduction of Siemens-Martin process and Gilchrist-Thomas

process of Quality of Steel. With these introductions Mild

Steel replaced Wrought Iron.

Further refinements in the process, such as basic oxygen

steelmaking (BOS), largely replaced earlier methods by

further lowering the cost of production and increasing the

quality of the metal. Now, Steel is one of the most commonly

used engineering materials in the world, with more than 1.3

billion tons being produced annually. It is a major component

in buildings, infrastructure, tools, ships, automobiles,

machines, appliances and weapons.

Generally Steels are of two kinds, namely Plain Carbon

Steel and Alloy Steel. Carbon Steel is simply composed of

Iron and Carbon. It is again divided into three kinds, namely

Low Carbon Steel or Mild Steel, Medium Carbon Steel and

High Carbon Steel. Low Carbon Steel by weight consists

carbon from 0.05% to 0.3%. It is made basic oxygen and open

hearth furnaces and is used for forging work, rivets, chains

and machine parts that does not need high strength. Medium

Carbon Steel has more carbon content and is more stronger

than Mild Steel. It is also difficult to cut, bend and weld

compared to Low Carbon Steel. It generally contains 0.3% to

0.6% carbon by weight. It is used for making of bolts, shafts,

car axles, rails and other parts or tools that require strong

metal. High Carbon Steel, also known as Carbon Tool Steel,

contains 0.6% to 1.5% carbon by weight. The best grades of

this steel is manufactured in Electric furnace. It is used to

make tools such as crowbars, drills, taps, dies, reamers, files,

cold chisels and hammers.

Alloy Steels are obtained by combining steel with one or

more other elements, usually metals. These steel are

generally heat treated for improving properties such as

increased hardenability, corrosion resistance and retention of

hardness and strength at high temperatures. There are three

classes of Alloy steels, namely Constructional Alloy Steel,

Alloy Tool Steel and Special Alloy Steel. Constructional Alloy

Steel is used for making of shafts, gears, levers, springs, bolts,

piston pins, connecting rods and steel used for construction

of buildings, bridges, auto frames, railroads and ships. Total

alloy content of these steel ranges from 0.25% to about 6%.

Alloy Tool Steel is used for making of cutting and forming

tools. The total alloy content of this steel ranges from 0.25%

to 38%. Special Alloy Steels are designed for extreme service

requirements. They include steels with very high heat,

corrosion or wear resistance.

WORLD STEEL STATISTICS

Steel is a cornerstone and key driver for the world’s

economy. The steel industry directly employs more than two

million people worldwide, plus two million contractors and

four million people in supporting industries. Including

industries such as construction, transport and energy, the

steel industry is a source of employment for more than 50

million people. It is at the core of the green economy, in

which economic growth and environmental responsibility

work hand in hand. It is the main material used in delivering

renewable energy: solar, tidal and wind. Steel is 100%

recyclable and can be used in new products and applications

amounting to significant energy and raw material savings. The

amount of energy required to produce a tonne of steel has

been reduced by 50% in the past 30 years.

Steel is everywhere in our lives. No other material has

the same unique combination of strength, formability and

versatility. Steel surfaces are hygienic and easy to clean.

Surgical and safety equipment and commercial kitchens are

all made with steel. Almost 200 billion cans of food are

produced each year. Steel cans ensure that food remains safe

and nutritious while saving energy as refrigeration is not

needed. Steel is an innovative and progressive industry

committed to the safety and health of its people. The

industry is committed to the goal of an injury-free workplace.

Safety metrics show that the lost-time injury frequency rate is

decreasing. Globally, the steel industry spends more than €12

billion per year on process improvements, new product

development and future breakthrough technology.

WORLD CRUDE STEEL PRODUCTION 1950 TO 2013

MAJOR STEEL-PRODUCING COUNTRIES 2012 AND 2013

TOP STEEL-PRODUCING COMPANIES 2013

STEEL PRODUCTION AND USE: GEOGRAPHICAL

DISTRIBUTION 2013

WORLD IRON ORE TRADE BY AREA 2013

MAJOR IMPORTERS AND EXPORTERS OF STEEL 2013

INDIAN STEEL INDUSTRY

The Indian steel industry has entered into a new era of

development since 2007-08, riding high on the resurgent

economy and robust demand for steel. Rapid rise in

production has resulted in India, becoming the 4th largest

producer of crude steel and the largest producer of sponge

iron in the world. Indian Steel Industry has just delivered a

decade of exponential revenue and profit growth.

The Indian steel industry has achieved significant

milestones in terms of growth in capacity, production and

exports to become a major player in the global steel industry.

Between FY2008 and FY2013, India’s steel production has

grown at a compound annual growth rate (CAGR) of about 7

percent.

Indian revenue (top four companies) grew close to 4x,

while the operating profits grew approximately by 5x during

the past decade.

MAJOR INDIAN STEEL INDUSTREIS

COMPANY PRODUCTS Steel Authority of India Ltd. (SAIL)

Semis, Structurals, Rods, Bars, Rebars, Plates, Pig Iron and Special Steel

Rashtriya Ispat Nigam Ltd. (RINL)

Structurals, Plain rounds, Bars, Plain Wire Rods in Coils, Forged rounds and Special Steel

Tata Steel Ltd. Flats, Longs, Structurals, Agricultural Implements and Bearings

Essar Steel India Ltd. Plates, Pipes, Factory welded beams, Trapezoidal blanks, Chequered plates, Hot and Cold rolled Steel Sheets

Bhushan Steel Cold rolled Steel Sheets, Strips and Coils

JSW Steel Ltd. Hot rolled Steel Sheets, Strips and Coils

Jindal Steel and Power Ltd.

Iron and Steel

Ispat Industries Ltd. Hot rolled Steel Sheets, Strips and Coils

Welspun Maxsteel Ltd. Tubes and Pipes

INDIAN STEEL INDUSTRY STRUCTURE

The Indian steel industry is divided into primary and

secondary sectors. The primary sector comprises a few large

integrated steel providers producing billets, slabs and hot

rolled coils, among others. The secondary sector comprises

small units focused on the production of value added

products such as cold rolled coils, galvanized coils, angles,

columns, beams and other re-rollers, and sponge iron units.

Both sectors cater to different market segments.

On the basis of ownership, the Indian steel industry is

broadly divided into private and public sector enterprises.

The private sector dominates production— accounting for

almost 78 percent of the finished steel output—while the

public sector has higher capacity utilizations.

The capacity share of the top five Indian steel players

stood at 51 percent of the total capacity (87.3 MTPA) in fiscal

year (FY) 2011.

VIZAG STEEL PLANT – RINL

Visakhapatnam Steel Plant, popularly known as Vizag

Steel is the most advanced steel producer and largest single

site plant in India, with the help of German and soviet

technology. Its products have been rated the best in the

world market. Almost 80% of its income comes from the

exports of steel products to Japan, Germany, United States,

Singapore, Dubai, Australia, South American countries and

many more. The company has grown from a loss making

industry to 3 billion dollar turnover company registering a

growth of 203.6% in just 4 years.

LOCATION

The plant is located in Visakhapatnam city, which is on

the coast of Bay of Bengal. Visakhapatnam city is an

important commercial center of Andhra Pradesh. It has the

deepest port and is one of the principal outlets for country’s

exporting Iron ore. The city has many large industries such as

Hindustan Petroleum refinery, Bharat Heavy Plates Electricals

ltd., Coromandal Fertilizers, Hindustan Shipyard etc. The city

is situated on the main broad gauge railway line between

Kolkata and Chennai and is well connected with other major

cities and state capitals by rail, road and air. The

Visakhapatnam steel plant is located south west of

Visakhapatnam Harbor and is about 26 Km from

Visakhapatnam city.

MAIN FACILITIES OF THE PLANT

DEPARTMENT FACILITY FEATURES CAPACITY

Coke oven 4 coke oven batteries of 67 ovens

each, of height 7m with 1000%

dry Quenching

2.261 Mt of blast

furnace coke (3 bat.)

Sinter Plant 2 sinter machines with 312 Sq.m

grate area

5.256 Mt of gross

sinter

Blast Furnace 2 nos. 3200 m3 blast furnace with

bell less top equipment and cast

house slag granulation

3.4 Mt of hot metal

Steel melting Shop 3 nos. 133Cn.m LD converter with

6 nos.

4 strand bloom casters

3.0 Mt of Liquid Steel

2.82 Mt Cast Bloom

Light and Medium

Merchant Mill

7 strands continuous Billet Mill

and 22 Strands, 2 strand

continuous Bar Mill with

“Tempcore” technology for Rebar

rolling

1.857 Mt billets

0.710 Mt

Bar products

Wire Rod Mill 4 strand 25 strands continuous

mill with “Stelmor” cooling

0.850 Mt Wire rods

Medium Merchant and

Structural Mill

20 strands continuous mill 0.850 Mt Medium

structural products

MAJOR UNITS OF THE PLANT

Raw Material Handling Plant (RMHP)

The Raw Material Handling Plant (RMHP) receives the

basic raw materials required for the steel making process

from various sources through railway wagons and by road.

These are stacked by stackers and reclaimed by re- claimers

and distributed to various departments of VSP through

conveyor system. The Iron Ore Fines, Iron Ore Lump, Sized

Iron Ore, Limestone (BF & SMS grades), Dolomite (BF & SMS

grades), Sand, Quartzite and Manganese lumps are stacked at

Ore& Flux Yard. The Imported Coking Coal (ICC), Medium

Coking Coal (MCC) , Boiler Coal (BC) are stacked in Coal Yard.

Coke is sent directly to Blast Furnace after tippling from ore

and flux wagon tipplers.

Coke Ovens & Coal Chemical Plant (CO&CCP)

Blast furnace require huge quantities of strong,

hard and porous solid fuel in the form of hard metallurgical

coke for supplying necessary heat for carrying out the

reduction and refining reactions. Coke is manufactured by

heating crushed cooking coal (<3mm) in absence of air at a

temperature of 1000ºC for 16-18 hours. At VSP the other 3

coke ovens batteries, 7m tall & having 67 ovens each, each

oven has a volume of 41.6 m3 and can hold up to 31.6 tons of

dry coal charge. Red hot coke is pushed out of the oven and

sent to coke dry cooling plants where nitrogen gas is used a

cooling medium. The heat recovery from nitrogen is done by

generating steam and expanding in two backpressure

turbines to produce 7.5MW power each respectively.

Another feature is the dry cooling of coke carried out by the

inert gas nitrogen thus, reducing pollution considerably.

Sinter plant (SP)

Sinter is a hard and porous ferrous material obtained by

agglomeration of iron ore fines, coke breeze limestone fines,

metallurgical wastes like flue dust, mill waste, LD slag etc.

Sinter is a better feed material to blast furnace in comparison

to iron ore lumps and its usage in blast furnaces help in

increasing productivity, decreasing the coke rate and

improving the quality of hot metal produced. Sintering in two

sinter machines of 312 m2 by heating the prepared feed on a

continuous metallic belt made of pallets at 1200-1300ºC. Hot

sinter discharged from sintering machine is crushed to 5mm

to 50mm size and cooled before dispatching to blast furnace.

Sinter plant of VSP has the capacity to produce 5.256 MT of

sinter per annum, which will cater for 80 % of Iron bearing

feed to Blast furnace. Two Sintering machines of Dwight Lloyd

type having 312 M2 total grate area are provided for this

purpose. Sinter machine is designed to operate at the rate of

1.2 T/hr/M2 for 330 days in a year.

Calcining and Refractory Material Plant (CRMP)

CRMP, i.e. Calcining & Refractory Materials Plant is an

integrated unit of Visakhapatnam Steel Plant. This plant plays

a significant role in the manufacturing of liquid steel. The

main customer of CRMP is Steel Melting Shop (SMS).

Calcining plant produces lime and calcined dolomite,

which are used for refining of hot metal to steel in the

converter. This plant has 5 rotary kilns of 325 tons/day

capacity. Lime is produced by Calcining limestone and

calcined dolomite is produced by Calcining dolomite.

Limestone is procured from Oman & Thailand and Dolomite

(SMS grade) from Madharam mines of VSP. The size of both

the raw materials is (25 - 60) mm. Both the raw materials are

received and stacked at RMHP.RMHP reclaims these

materials and conveys to LSDS (Limestone & Dolomite

Screening Plant) via a stream of conveyors. LSDS has two

screens of 25mm size (VS6 & VS7) to screen out the minus

fraction from raw materials. The -25mm size is sent to RMHP

for use in Sinter Plant. The +25mmsize limestone is stored in

bunker 5 and +25mm dolomite is stored in bunker 6. These

materials are then conveyed to the stone bins of all the kilns

by operating the weigh feeders below the two bunkers.

Limestone and dolomite are charged to separate kilns.

Blast Furnace (BF)

VSP has two Blast Furnaces named as “Godavari” &

“Krishna” with an effective volume of 3200 m3, each of which

are the largest in the country equipped with Paul worth Bell

less top equipment with conveyor charging. Blast Furnace is

charged with coke, iron ore and sinter from the top and

produces about 5000 tons of molten iron per day. Its novel

circular cast house with four tap holes ensures continuous

tapping of hot metal. The annual production capacity of these

Blast Furnaces is 3.4 million tons of liquid iron. Provision

exists for granulation of 100% liquid slag at blast furnace cast

house and utilization of blast furnace gas top pressure (1.5-

2.0 atmospheric pressure) to generate 12 MW of power in

each furnace by employing gas expansion turbines.

Steel Melting Shop (SMS)

Steel is an alloy of iron with carbon up to 1.8%. Hot

metal produced in the blast furnaces contain impurities such

as carbon (3.5-4.25%), silicon (0.4-0.5%), manganese (03.-

0.4%), sulphur (0.04%max) and phosphorus (0.14% max) is

not suitable as a common engineering material to Improve

the quality that impurities are to be eliminated or decreased

by oxidation process.

VSP employs three top blown oxygen converters called

LD- convertors each having 133m3 volume capable of

producing three million tons of liquid steel annually. 99.5% of

pure oxygen at 15-16 KSCG pressure is blown in the convertor

through an oxygen lance having convergent – divergent

copper nozzles at the blowing end. Oxygen oxidizes the

impurities present in the hot metal that are fixed as slag with

basic fluxes such as lime. During the process heat is

generated by exothermic reactions of oxidation of metalloids

like Si, Mn, p & c and temperatures rising 1700ºC enabling

refining and slag formation. Different grades of steel of

superior quality can be made by this process by controlling

the oxygen blow or addition of various Ferro alloys or special

additives such as FeSi, FeMn, Si-Mn, coke breeze, Al in

required quantities while liquid steel is being tapped from the

convertor into a steel ladle. Convertor gas produced as a

byproduct is used as secondary fuel.

Continuous casting department (CCD)

Continuous casting may be defined as teaming of liquid

steel in a mould with a false bottom through which partially

solidified bar is continuously withdrawn at the same rate at

which liquid steel is teamed in the mould. Facilities at a

continuous casting machine include a lift and turntable for

ladles, copper mould, oscillating system tundish, primary and

secondary cooling arrangement to cool the steel bloom. Gas

cutting machines is used for cutting the blooms in required

lengths of 6m long. At VSP we have six-4strand continuous

casting machines capable of producing 2.82 million tons per

year blooms of size 250X250mm and 250X320mm. The entire

quantity of molten steel produced (100%) is continuously cast

in radial bloom casters, which help in energy conservation as

well as production of superior quality products.

Rolling Mills

Blooms produced in SMS-CCD do not find much

applications as such and are required to be shaped into

products such as billets, round, squares, angles (equal and

unequal), channels, I-PE beams, HE beams, wire rod and

reinforcements by rolling them in, there sophisticated high

capacity, high speed, fully automated rolling mills, namely

Light and Medium Merchant Mills (LMMM), Wire Rod Mills

(WRM) and Medium Merchant and Structural Mill (MMSM).

Light and Medium Merchant Mill (LMMM)

The cast blooms from continuous casting department

are heated and rolled in the two high speed and fully

automated rolling mills namely Light & Medium Merchant

Mill (LMMM) and Medium Merchant & Structural Mill

(MMSM). The billets produced in LMMM are further rolled in

Bar Mill / Wire Rod Mill (WRM). The finished products include

wire rods & long products like Reinforcement bars, rounds,

squares, flats, angles, channels, billets etc. LMMM comprises

of two units in the billets/break down mill 250 320 mm size

blooms are rolled into billets of 125 mm size after heating

them in two nos. of walking beam furnaces of 200T/hr

capacity each. This unit comprises of 7 stands (2 horizontal

859 1200mm) and 5 alternations vertical and horizontal

stands (730 1000 mm and 630 1000 mm) billets are supplied

from this mill to bar mill of LMMM, wire rod mills (WRM).

Wire Rod Mill (WRM)

The Wire Rod Mill of VSP is high speed 4 strand No-Twist

continuous mill designed to produce 8,50,000 T of wire rod

coils. The mill is designed to produce plain wire rods from 5.5

mm to 12.7 mm diameter and Rebar in 8mm, 10mm and

12mm diameter in coil form. However sizes up to 14mm are

being rolled presently. The mill is constructed at an elevated

level of +5350 mm. Rolled billets of 125 mm x 125 mm square

cross section, length ranging from 9.8 m to 10.4 m and

weighing approx 1250 kgs are used as input material. The mill

is designed to roll steel stock of 0.9% max Carbon content.

Medium Merchant and Structural Mill

The Medium Merchant and Structural Mill (MMSM) is one

of the modern rolling mills of Visakhapatnam Steel Plant. This

is a single strand continuous mill having production capacity

of 8, 50,000 T/year. The important feature of this mill is that

Universal beams (both parallel and wide flange) have been

rolled first time in India using Universal stands. Parallel flange

beams have advantage over conventional beams as, for the

same weight; the section is stronger and stiffer due to greater

moment of inertia and higher radius of gyration.

Roll Shop and Repair Shop (RS & RS)

Roll Shop and repair shop plays a major role in fulfilling

the technological needs of all the mills and caters in respect

of Roll Pass Design, Roll redressing, roll assembles, guides,

and few maintenance spares. During Rolling, Roll passes tend

to wear out and gradually lose their initial shape resulting in

the size or surface finish of the product being rolled deviated

from the allowable tolerances. This is remedied by Redressing

that is by turning the rolls to restoring the width and depth of

pass to its original dimensions. The main activities are roll

pass design, redressing of rolls, new rolls turning, assembly of

rolls with bearings, preparation of guides, and their service

and manufacturing or repair of mill maintenance spares. The

roll pass design section designs development of new

sections, modification of existing pass designs for improving

the productivity and quality, preparation of rolling schedules,

groove detail and distribution and template drawings, part

programming for grooving of rolls on CNC lathes.

Thermal Power Plant and Blower House (TPP&BH)

VSP has a separate thermal power plant to meet

substantial part of its power requirement. The power plant

also includes blower house for blowing hot air to the blast

furnaces. The power plant utilizes surplus coke oven and blast

furnace gasses for heating boilers. To meet the balance

requirement of the boilers thermal coal is procured. Thus the

power plant helps in reducing cost of production of VSP.

Service Units (Works)

Power Engineering Maintenance (PEM) - Power

Engineering Maintenance (PEM) department is doing

Capital repairs, Breakdown maintenance, Preventive

maintenance of Rotary equipments like Turbo-

Generators, Turbo-blowers, Turbo compressors, High

capacity Exhausters, Fans, Pumps and Hydraulic

Couplings.

Central Maintenance-Mechanical (CMM) - Central

Maintenance Mechanical (CMM) department is one of

the major service departments in VSP which is carrying

out major mechanical maintenance and conveyor belt

replacement activities throughout the plant. CMM is the

first maintenance section in VSP, which is implementing

one of the best Ten practices i.e., work Flow and Control

Management as a part of QMS. In this System internal

work order is issued to the respective zone and feedback

is received at Central Office after work is completed. In

the feedback, duration, manpower and identification of

conveyor belt, supplier name and quantity etc., are

recorded. As all works are carried out through work

order system, accuracy of data is ensured which enables

in reducing the shutdown periods.

Quality Assurance & Technology Development

(QA&TD) - The Quality Assurance and Technology

Development have been set up to take care of activities

pertaining to quality control of raw materials, Semi-

finished products and finished products. These dept.

laboratories are provided at major dept. like C & CCD,

BF, SMS, and Rolling Mills etc. The department controls

the process by providing process charts for production of

quality products. Quality Assurance and Technology

Development carries out final inspection and testing

including spark testing of finished products and assigns

grades to them.

MEDIUM MERCHANT AND STRUCTURAL MILL

(MMSM)

This is a single strand continuous mill having rolling

capacity of 8, 50,000 Tons per year. In this mill, Universal

beams both parallel and wide flange are rolled for the first

time in India.

Walking Beam Furnaces will be utilized to reheat the

blooms of 250mm thick x 250mm width x 6000mm long in

two rows to 1200°C. The stock will travel through the furnace

by means of walking and stationery beams, properly lined,

which will be cooled by means of an ECS producing steam.

MMSM is one of the modern rolling mills of Visakhapatnam

Steel Plant.

The input material is weighing nearly 2,900 Kg. The mill

has flexibility in design to adjust the production program, size

wise and grade wise to meet the market demand. The quality

and tolerance levels of the finished products meet the Indian

and International Standards.

Products manufactured in the MMSM are Rounds,

Squares, Flats, Equal angles, Unequal angles, Channels,

Beams HE type, Beams IPE type.

Process

There are two reheating furnaces in MMSM, each having

130 Tons /hour capacity. 250mm X 250mm/6m blooms from

SMS bloom storage yard are charged into the furnaces and

heated up to 1200°C.

Mixed Gas is used in the furnace for heating the blooms.

Mixed Gas is a mixture of Coke Oven Gas, Blast furnace Gas

and LD Gas. As the mixture continuously varies, calorific value

of Mixed Gas also varies between 1700 and 2400 kcal/m3.

For proper combustion inside the furnace air and gas are

mixed in a definite ratio. This depends up on the calorific

value of the mixed gas. If the calorific value increases, air

requirement also increases. Similarly, if the calorific value

reduces, less quantity of combustion air will be sufficient.

Hence, proper Air / Gas Ratio should be ensured for effective

combustion to take place. By ensuring proper ratio of air and

gas, blooms are heated in the furnace. The heated blooms are

discharged and rolled in 20 stands continuous mill. The mill

train of MMSM contains of a total of 20 stands as follows -

Roughing Train – Consists of 4 High Horizontal stands, 2

Vertical stands and 2 Combination stands.

Intermediate Train – Consists of 2 High Horizontal stands,

2 Horizontal stands and 2 Combination stands.

Finishing Train – Consists of 4 Horizontal stands and 2

Combination stands.

INDUSTRIAL FURNACE

Industrial process heating furnaces are insulated

enclosures designed to deliver heat load for heat processing.

Generally furnaces operating below 1200F are called Ovens.

But In general, Coke Ovens operate at above 2200F. In

Ceramic industries, furnaces are called as Kilns and in

Petroleum and CPI (Chemical Process Industries), furnaces are

termed as Heaters, Kilns, After Burners, Incinerators and

Destructors.

Industrial furnaces are generally classified into two

categories namely, Batch type and Continuous type

Furnaces. In Batch type furnace the job will be in stationary

position. Batch type furnaces are again divided as Box, Slot,

Car, Bell, Elevator, Pot and Dip-Tank type furnaces. In

Continuous type furnace the output will be continuous and of

large volume at regular intervals. Continuous type furnaces

are divided as Pusher type, Walking Hearth type, Rotary

Hearth type and Walking Beam type furnaces.

WALKING BEAM REHEATING FURNACE

Walking Beam Furnace heat the steel blooms, casted in

CCD, to the rolling temperature of 1200°C. Two pushers push

the bloom into the furnace from the bloom charging side.

Blooms travel on skid pipes through heating zones and then

solid hearth in soaking zones. The furnace has five zones out

of which three are called heating zones and two are soaking

zones. There are in total 59 burners. The combustion air is

preheated to 500°C in air recuperator. Flue gases are used for

preheating the combustion air before being exhausted to the

atmosphere through chimney. Furnace pressure in soaking

zone is maintained positive. Control and measuring

instruments required to control furnace pressure and

temperature as well as efficient fuel utilization are provided.

Evaporative Cooling System (ECS) is used for skid pipe cooling

during which waste heat steam is produced.

Equipment Specifications

The walking beam furnace is used for heating

blooms of plane carbon steel, low alloy steel; free cutting

steel, medium and high carbon steel from ambient to about

1200⁰C. The furnace is charged in two rows for 6mts long

blooms and also with a provision of charging of 12mts

blooms. The particular about the walking beam furnace is as

given below:

Length 21.7m

Width 18.5m

Furnace Height 4.2m

Maximum Effective Area 240 m2

Furnace Hearth Output 0.54T/ m2 -hr

Zones Burners Temp (⁰C)

Zone 1(Top Zone, Roof) 12 1125-1225


Zone 3(Front Zone) 8 1108-1220



Stack Height (Chimney) 85m

Mixed Gas Flow 50000 Nm3/hr

Pressure 600mmwc(min) -

1000mmwc(max)

Capacity 130T/hr

Net Heat Value 2000kcal/ Nm3

Exhaust Gas Heat Recovery Air and Gas Recuperators

Furnace Pressure Control Damper Flow Control

Refractories Alumina Brick, LWBF, Mica

Insulator and Wool.

Walking Beam (Skids)

Operation

Blooms are moved forward step by step, avoiding any

friction or rubbing during its conveyance through the furnace.

The blooms are gently lifted from the stationary beams,

moved forward by walking beam and gently placed on

stationary beams. The walking beam supporting ports are

fastened to a movable frame which are equipped with rollers

and permit the vertical and horizontal movement for transfer

of blooms. The walking beams and stationary beams are

fabricated out of seamless tubes.

Charging and discharging equipment

The blooms are conveyed and positioned in front of the

furnace on roller table by electrical control. After positioning

the blooms on the roller tables, the blooms are transferred

on the charging table by means of charging device in single

row by means of discharging device. Two discharging device

are suitable row or two-row operation.

Hydraulic Power Pack Unit

A centrally located hydraulic power pack unit is provided

for operation of the various hydraulic cylinders foe walking

beam mechanism. The power pack unit consists of fluid tanks,

pumps with drives and control, necessary solenoid valves,

check valves pressure relief valves, filters etc. One standby

pump with drive unit is also provided.

Skids and Support Tube Cooling System

Evaporating cooling system (ECS) is provided for cooing

of the skids and support tubes. Steam generated is divided to

plant steam network. The evaporated cooling system

comprises of separating drums, recirculating pumps,

demineralised water, water, water storage tanks, feed pumps

with necessary pipes, valves, fitting, gadgets and necessary,

instrumentation. Besides cooling of skid tubes and support

tubes by ECS, foiling items are also cooled by water.

1. Charging and discharging lintels

2. Discharge doors

3. Hydraulic oil

4. TV cameras

Combustion Systems

Burners

Adequate number of burners of suitable design to

fire mixed gas in preheating, heating (top and bottom) are

provided. The burners are provided. The burners are

provided with peepholes and ignition ports for easy operation

and firing. The burners connected load is 20% higher than the

fuel consumption rate, which is calculated on the basis of

maximum furnace output.

Combustion air fan

The furnace is provided with two combustion air

fans one in operation and as a standby. The fan of centrifugal

type, directly coupled to the driving motor. The rated

capacity of the fan is 30% higher than the volume of air

required for maximum connected load of the burners

considered 10% excess air. The blowers are equipped with

adjustable directional blades on the suction side.

Water gas exhaust system

1. Chimney: Products of combustion are exhausted from

the preheating section of the furnace through

underground fuel channel leading to a chimney. The

height of the chimney is decided considering draft

and statutory regulations. The chimney is of self-

supporting type, constructed out of reinforced steel

plant and lined with refractory material.

2. Dampers: Dampers for automatic pressure controlling

the waste gas is made of heat resistant material to

withstand the temperature pf the waste gases.

3. Air and Gas Recuperators: Connection type multi

tabular air and gas Recuperators are provided in the

waste gas flue channel. The unit is discharged for

preheating the inlet air to the burners manifold to a

temperature of around 450ᵒ and a mixed gas leading

to the burner manifold to a temperature of around

380ᵒ. The Recuperators tube is made up of suitable

heat resistance steel to withstand the higher

temperature of waste gas. Hot air bleed off

arrangement is provided in the duct leading to the

burner.

4. Dilution of Air Fan: A centrifugal blower complete

with accessories is provided for supplying cold air in

the waste flue gas upstream of the recuperator to

prevent the recuperator tubes from overheating.

5. Lagging: The combustion air pipe, gas pipe and pipe

between the recuperators and the burners is lagged

extremely with insulating materials or lines internally

with refractory material depending on the diameter.

The lagging is protected by galvanized sheet

wrapping.

Refractories and Insulation

The roof of the furnace is flat suspended type which is

built-up with shaped roof hanged bricks made out of

superheat duty fire bricks. The roof hanger bricks are bagged

up with a layer of insulating matter and it is made of heat

resistant steels.

The doors are lined with high temperature insulating

constables. The waste gas flue upstream of the recuperator is

lined with the cold faced lined brick. One ventilation course

of red brick is provided between the refractory brick and

concrete walls. Thickness of the refractory layers in the waste

gas flue is so chosen that maximum temperature in the flue

concrete face does not exceed 150⁰C.

The wall is lined up with a high alumina fire bricks with

cold faced insulating bricks and insulating blocks.

The furnace hearth is lined with high alumina fire bricks

backed up with cold faced insulating bricks and insulating

blocks. The movable and stationary beams are lined with high

alumina constables backed up by insulation materials.]

THERMAL ANALYSIS OF THE FURNACE

Performance Evaluation of a Furnace

Thermal efficiency of process heating equipment, such

as furnaces, ovens, heaters, and kilns is the ratio of heat

delivered to a material and heat supplied to the heating

equipment.

The purpose of a heating process is to introduce a

certain amount of thermal energy into a product, raising it to

a certain temperature to prepare it for additional processing

or change its properties. To carry this out, the product is

heated in a furnace. This results in energy losses in different

areas and forms as shown in Sankey diagram figure 4.10. For

most heating equipment, a large amount of the heat supplied

is wasted in the form of exhaust gases.

These furnace losses include –

Stored Heat Loss - First, the metal structure and insulation

of the furnace must be heated so their interior surfaces

are about the same temperature as the product they

contain. This stored heat is held in the structure until the

furnace shuts down, then it leaks out into the surrounding

area. The more frequently the furnace is cycled from cold

to hot and back to cold again, the more frequently this

stored heat must be replaced. Fuel is consumed with no

useful output.

Wall Losses - Additional heat losses take place while the

furnace is in production. Wall or transmission losses are

caused by the conduction of heat through the walls, roof,

and floor of the heating device, as shown in Figure.

Once that heat reaches the outer skin of the furnace and

radiates to the surrounding area or is carried away by air

currents, it must be replaced by an equal amount taken

from the combustion gases. This process continues as long

as the furnace is at an elevated temperature.

Material Handling Losses - Many furnaces use equipment

to convey the work into and out of the heating chamber,

and this can also lead to heat losses. Conveyor belts or

product hangers that enter the heating chamber cold and

leave it at higher temperatures drain energy from the

combustion gases. In car bottom furnaces, the hot car

structure gives off heat to the room each time it rolls out

of the furnace to load or remove work. This lost energy

must be replaced when the car is returned to the furnace.

Cooling Media Losses - Water or air cooling protects rolls,

bearings, and doors in hot furnace environments, but at

the cost of lost energy. These components and their

cooling media (water, air, etc.) become the conduit for

additional heat losses from the furnace. Maintaining an

adequate flow of cooling media is essential, but it might be

possible to insulate the furnace and load from some of

these losses.

Radiation Losses - Furnaces and ovens operating at

temperatures above 540°C might have significant radiation

losses, as shown in Figure. Hot surfaces radiate energy to

nearby colder surfaces, and the rate of heat transfer

increases with the fourth power of the surface's absolute

temperature. Anywhere or anytime there is an opening in

the furnace enclosure, heat is lost by radiation, often at a

rapid rate.

Waste Gas Loss - Waste-gas loss, also known as flue gas or

stack loss is made up of the heat that cannot be removed

from the combustion gases inside the furnace. The reason

is heat flows from the higher temperature source to the

lower temperature heat receiver.

Air Infiltration - Excess air does not necessarily enter the

furnace as part of the combustion air supply. It can also

infiltrate from the surrounding room if there is a negative

pressure in the furnace. Because of the draft effect of hot

furnace stacks, negative pressures are fairly common, and

cold air slips past leaky door seals, cracks and other

openings in the furnace. Figure, illustrates air infiltration

from outside the furnace. Every time the door is opened,

considerable amount of heat is lost.

Efficiency of Furnace

The efficiency of a furnace is the ratio of useful output to

heat input.

Efficiency ƞ = Heat output

Heat Input

The furnace efficiency can be determined by both direct

and indirect method.

Direct Method

The efficiency of furnace can be judged by measuring

the amount of fuel needed per unit weight of material.

The quantity of heat to be imparted (Qout) to the stock can be

found from

Indirect Method

Similar to the method of evaluating boiler efficiency by

indirect method, furnace efficiency can also be calculated by

indirect methods. Furnace efficiency is calculated after

subtracting sensible heat loss in flue gas, loss due to moisture

in flue gas, heat loss due to openings in furnace, heat loss

through furnace skin and other unaccounted losses.

Qout = MS x Cps (TD – TC)

In order to find out furnace efficiency using indirect

method, various parameters that are required are hourly

furnace oil consumption, material output, excess air quantity,

temperature of flue gas, temperature of furnace at various

zones, skin temperature and hot combustion air temperature.

Instruments like infrared thermometer, fuel efficiency

monitor, surface thermocouple and other measuring devices

are required to measure the above parameters.

Heat lost through Flue gases, HF = VFG x CPFG (TFG-TS)

Heat lost through ICW, HW = VCW x ρW x CPW x ∆TCW

Heat lost through radiation from doors, HR = 4.96E x

[(TO+273/100)4 – (TS+273/100)4] x A x dt

Heat lost through radiation and convection, HRC = AS x a x

(TEW – TS)1.25 + 4.88E x [(TEW+273/100)4 – (TS+273/100)4]

Heat lost through moisture in Air, HMA = Actual mass of air

x Humidity factor x Specific Heat x Temperature diff.

Heat lost through moisture in Gas, HMG = Moisture in Gas x

Specific Heat x Temperature diff.

Notations – Ms – Mass of Stock heated Cps – Specific Heat of Bloom material TD – Bloom Discharging Temperature TS – Ambient Temperature VFG – Volume of Flue gases CPFG – Specific Heat of Flue gases TFG – Flue gas furnae exit Temperature VCW – Volume of ICW supplied CPW – Specific Heat of Water ∆TCW – Rise in temperature of ICW TO – Temperature of opening door A – Area of the opening door dt – Opening time of the doors AS – Area of Surface TEW – Furnace External wall temperature

Loss Percentages

HF% = 𝐇𝐅 𝐱 𝟏𝟎𝟎

𝐂𝐕 𝐨𝐟 𝐅𝐮𝐞𝐥

HW% = 𝐇𝐖 𝐱 𝟏𝟎𝟎

𝐂𝐕 𝐨𝐟 𝐅𝐮𝐞𝐥 𝐱 𝐆𝐚𝐬 𝐅𝐥𝐨𝐰

HR% = 𝐇𝐑 𝐱 𝟏𝟎𝟎


HRC% = 𝐇𝐑𝐂 𝐱 𝟏𝟎𝟎


HMA% = 𝐇𝐌𝐀 𝐱 𝟏𝟎𝟎


HMG% = 𝐇𝐌𝐆 𝐱 𝟏𝟎𝟎


Furnace Thermal Efficiency, ƞ = 100 – HF% - HW% - HR% -

HRC% - HMA% - HMG%

OBSERVATIONS

PARAMETERS UNITS FURNACE 1 FURNACE 2

TOTAL GAS FLOW m3/h 5618 5291 5254 5214 9658 9693 9973 9983

TOTAL AIR FLOW m3/h 16952 16956 17047 16857 27943 27712 28383 28768

MIXED GAS CV Kcal/m3 2362 2364 2345 2355 2346 2373 2392 2413

NUMBER OF BLOOMS HEATED

93 93 93 93 87 87 87 87

BLOOMS ROLLED 27 28 27 26 39 40 40 41

MASS OF EACH BLOOM Ton 2.67 2.67 2.67 2.67 2.67 2.67 2.67 2.67

BLOOM DISCHARGING TEMPERATURE

OC 1174 1173 1175 1174 1177 1178 1180 1181

BLOOM CHARGING TEMPERATURE

OC 33 33 33 33 33 33 33 33

FLUE GAS EXIT TEMPERATURE

OC 541 540.4 541 540.4 542.3 543 543.7 544.3

AMBIENT TEMPERATURE OC 33 33 33 33 33 33 33 33

VOLUME OF ICW SUPPLIED

m3/h 68.83 69.21 69.02 68.88 57.75 58.23 59.10 59.09

PRESSURE RISE IN ICW bar 4.22 4.21 4.18 4.19 4.3 4.29 4.29 4.27

OPENING TIME OF DOORS (CHARGING & DISCHARGING)

h 1.11 1.11 1.11 1.11 1.04 1.04 1.04 1.04

CHARGING DOORS TEMPERATURE

OC 80 80 80 80 80 80 80 80

DISCHARGING DOORS TEMPERATURE

OC 90 90 90 90 90 90 90 90

FURNACE EXTERNAL WALL TEMPERATURE

OC 45 45 45 45 45 45 45 45

MOISTURE IN FUEL GAS m3/h 2.97 2.97 2.97 2.97 2.97 2.97 2.97 2.97

SPECIFIC HEAT OF FLUE GAS – 0.3 kcal/m3-oC

SPECIFIC HEAT OF FUEL GAS – 0.3 kcal/m3-oC

SPECIFIC HEAT OF AIR – 0.3 kcal/m3-oC

SPECIFIC HEAT OF BLOOM – 0.165 kcal/m3-oC

DENSITY OF AIR – 1.27 kg/m3

SPECIFIC HEAT OF WATER – 1 kcal/kg-oC

HUMIDITY FACTOR OF AIR – 0.654

CHARGING DOOR AREA – 6.7m x 0.77m x 2 Doors

DISCHARGING DOOR AREA – 6.7m x 1.2m x 2 Doors

ROOF AREA – 282 m2

HEARTH AREA – 282 m2

SIDE WALL AREA ( MILL SIDE & BSY SIDE ) – 182 m2

DENSITY OF WATER – 1000 kg/m3

CALCULATIONS

PARAMETER UNITS FURNACE 1 FURNACE 2

Heat given by Fuel Gas

Mcal/h 12593.72 23402.41

Heat due to oxidation

Mcal/h 6704.1 6272.1

Heat in the material

Mcal/h 13572.02 20194.81

Heat lost through Flue gas

Mcal/h 3396.09 5821.74

Heat lost to ICW Mcal/h 100.94 87.50

Heat lost through doors due to radiation (Charging & Discharging)

Mcal/h 9.07 8.58

Heat lost through walls of furnace due to radiation and convection

Mcal/h 45.19 45.19

Heat lost to moisture in air

Mcal/h 1861.62 3115.10

Heat lost to moisture in Fuel Gas

kcal/h 303.56 305.88

HEAT BALANCE SHEET

Furnace 1

INPUT OUTPUT

Description Value (Mcal/h) Description Value (Mcal/h)

Percent %


12593.72 Heat in the material

13572.02 70.33%


6704.1 Heat lost through Flue gas

3396.09 17.59%

Heat lost to ICW 100.94 0.52%


9.07 0.04%


45.19 0.23%


1861.62 9.49%


303.56 1.54%

Unaccounted losses

9.33 0.04%

Total 19297.82 Total 19297.82 100%

Thermal Efficiency of the Furnace = 70.33% (Direct Method)

= 70.55% (Indirect Method)

Furnace 2

INPUT OUTPUT

Description Value (Mcal/h) Description Value (Mcal/h)

Percent %


23402.41 Heat in the material

20194.81 68.05%


6272.1 Heat lost through Flue gas

5821.74 19.62%

Heat lost to ICW 87.50 0.29%


8.58 0.03%


45.19 0.23%


3115.10 10.49%


305.88 1.03%

Unaccounted losses

95.71 0.32%

Total 29674.51 Total 29674.51 100%

Thermal Efficiency of the Furnace = 68.05% (Direct Method)

= 67.99% (Indirect Method)

CONCLUSION

The present efficiency of furnace in terms of

performance is more than satisfactory. There are many

potions for increasing the energy efficiency.

Employing air –gas ratio control technology and

regenerative burner is the most effective way to increase

efficiency in most furnaces. To fight the challenges of rising

energy cost and environmental regulations, a close co-

operation of the end user, the furnace builder and the burner

manufacture is necessary to choose the best possible

configuration with respect to -

Performance Energy efficiency

Low emissions

Low Maintenance

Not higher than needed investment costs.

We formed furnace efficiency with waste heat recovery

system is very much more compare to actual furnace

efficiency. By following the above action with upcoming

technologies the furnace efficiency can be increases further

more. Efficiency increase measure nothing but fuel saving

fuel save means energy saving, we can turned it as revenue

saving.

Due to technological obsolescence and the high rate of up

gradation the availability of spares and its associated techno

economics influence the running of the system. In such cases

sustaining an old system economically is not feasible and up

gradation to an updated system is not a matter of choice but

a matter of choice but a matter of consumption.

report - heat balance of a reheating walking beam furnace - vsp

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