Maerz Ofenbau Lime Burning Technology 2008 En

7/28/2019 Maerz Ofenbau Lime Burning Technology 2008 En

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Maerz

Lime Burning Technology


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Our Company

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Maerz Ofenbau AG was established in 1950

in Zurich, Switzerland, by Austrian magnesite

producers to design and sell open hearth

furnace technology to the worldwide steel

industry.

In 1965 Maerz began the design and

construction of the MAERZ Parallel Flow

Regenerative (PFR) Lime Kiln, characterised

by its high thermal efficiency and superiorlime quality, now generally known as the

MAERZ PFR Kiln.

The initial design was an oil-fired lime kiln of

150 tpd capacity. Soon larger units were

designed and gas firing technology was

added to oil firing. In the late seventies a

patented system to apply pulverised solid

fuels was introduced. Today Maerz offers

designs for PFR Kilns with nominal capacities

between 100 and 800 tpd and with firing sys-

tems for virtually all types of liquid, gaseousand pulverised solid fuels.

As a further milestone, in the late eighties,

Maerz introduced the Maerz Finelime Kiln.

This vertical-shaft kiln type allows the calci-

nation of small-size limestone and dolomite,

which in the past had to be processed in

rotary kilns with significantly lower thermal

efficiency, i.e. higher heat consumption.

In 1995 RCE Industrieofenbau Engineering

GmbH, located in Radenthein, Austria, a

specialist in the field of furnaces and kilns

for the production of refractory materials,


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Our Achievements

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became a subsidiary company of Maerz,

adding its high-efficiency single shaft kiln

to the existing product portfolio.

To satisfy the steadily increasing market

demand in Eastern Europe, Maerz established

a subsidiary engineering division MaerzOfenbau s.r.l. in Timioara, Romania, in

2005.

In 2006 Maerz joined the Polysius Group,

becoming the centre of lime business activi-

ties of the entire Group.

With Polysius know-how and personnel re-

sources, Maerz now also offers rotary kilns,

annular shaft kilns, suspension calciners and

equipment up- and downstream of the lime

kilns, thus turning into a full-line supplier of

kilns and associated equipment for the lime

industry.

By combining Maerz, Polysius and RCEs

know-how and experience in the lime burning

technology field, Maerz is in a unique position

to offer tailor-made solutions to its cus-

tomers.

The different kiln systems such as PFR

Kilns, Single Shaft Kilns, Rotary Kilns or

Suspension Calciners do not compete with,

but complement each other.

Depending on the application conditions, such

as production capacity, type of fuel, raw mat-

erial feed size, lime quality required, etc. the

decision for a certain kiln type is made by

evaluating the balance between cost, techno-

logical reliability and flexibility.

It is Maerzs policy on the basis of an extensive

product portfolio to carefully assess all initial

conditions before recommending the most suit-

able kiln technology to its customers to meetthe specific project conditions and to achieve

the required product quality.

Maerz the world leader in the construction

of lime kilns is not only in a position to offer

the most energy-efficient type of lime shaft kiln

existing to date but also the most comprehen-

sive scope of lime burning equipment.

Supported by a global network of representa-

tives and partners, Maerz can present the lar-

gest number of reference plants installed

worldwide in the lime industry by one singlecompany.

Large photo + Fig. 1

Headquarters of

Maerz Ofenbau AG in Zurich,

Switzerland.

Fig. 2 4 From the Idea

to the Start of Production.


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Lime is one of the most widespread and ver-

satile chemicals produced and applied world-

wide.

Quicklime and hydrated lime

have been used in many civilisa-

tions for more than 3000 years.

Starting from the construction

and building industry in the early

days, the uses of lime, dolomiticlime and dolomite have become

almost countless.

Vital in the steel, building and

chemical industries, as well as

in agriculture, lime is a basic

raw material that has made an

essential contribution to many

of the achievements of our

modern world.

Global production of lime isestimated to be approx. 300

million tons per year, where-

of the sales-relevant portion

amounts to approx. 120 million

tons per year. In industrialised

countries the yearly per capita

consumption of lime products

amounts to approx. 80 kg.


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Applications of Lime

Iron and steelmaking

- capturing of impurities inthe steel bath

- iron ore sintering

- desulphurisation

Non-ferrous metals

- beneficiation of non-ferrous

metal ores, e.g. copper

- recovery of gold and silver

in cyanide extraction

- flotation processes for lead,

nickel, zinc, molybdenum

and uranium

Construction and building

- mortars and plasters- sandlime bricks, aerated

concrete bricks

Chemical industry

- manufacture of sodium

alkalis, e.g. soda ash

- production of calcium carbide

Environmental applications

- treatment of water, waste

water and sewage

- air pollution control

Agriculture

- liming of soils, forests and

lakes

- compound fertilisers

Soil stabilisation

- stabilisation of road beds

for high performance roads

- construction of airport

runways, parking lots and

railway tracks

PCC industry

- paper industry

- paints and coatings

- plastics

The most important consumers of lime, dolomitic lime and

dolomite are:


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Types of

Kilns and Calciners

Kiln type

Capacity [tpd]

Stone size [mm]

Heat input [kJ/kg]

[kcal/kg]

Key criteria

Services

Revamping

Upgrading Modernisation

Alternative Fuels

Automation

Spare parts

Rectangular

PFR Kiln

E1 E6

100 400

30 120

3390 3650

810 870

high reactivity

lime

PFR Kilns

Multi-fuel firing systems

Conversion to alternative fuels Advanced charging technology for increase of quarry yield and production

Circular

PFR Kiln

R1 R5

300 800

30 160

3390 3650

810 870

high reactivity

lime

Finelime

Kiln

F1 F3

200 400

15 40

3310 3560

790 850

high reactivity

lime


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Product Portfolio

Annular Shaft

Kiln

A1 A3

200 600

15 200

3800 4100

910 980

high CO2-content

in off-gas

Annular Shaft Kilns

Application of solid fuels

Single Shaft Kilns

Conversion of mixed feed

kilns to solid fuel dust firingwith significant increase of

kiln capacity

Rotary Kilns

Conversion to preheater kilns

Sulphur bypass system

Single Shaft

Kiln

H1 H5

50 300

10 100

4100 4610

980 1100

medium to hard

burnt lime

Preheater

Rotary Kiln

500 1200

10 50

4820 5650

1150 1350

high production rate

low sulphur product

Suspension

Calciner

300 1200

0.03 2

5450 5860

1300 1400

finest raw material

size


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PFR Kilns

The PFR (Parallel Flow Regenerative) kiln type is

characterised by two vertical shafts connected by

a cross-over channel.

This allows parallel flow heating, i.e. the paral-

lel flow of limestone and hot gases as well as

regenerative preheating of the combustion air in

one shaft (the burning shaft) whilst the mixture of

combustion gases and lime cooling air simultane-

ously preheats the limestone in the second shaft

(the non-burning shaft). Each shaft cycles through

the burning and non-burning mode at intervals of

approx. 10 to 15 minutes.

The Parallel Flow Principle is ideal for producing

high reactivity quicklime at the highest thermal

efficiency of all modern lime kilns.

PFR Kilns are available for capacities from 100 to

800 mt/day and can be fired with gaseous, liquid

and pulverised solid fuels.

Depending on the required production capacity,

the limestone grain size to be processed and the

fuels available, PFR Kilns of rectangular, circular

or Finelime design are proposed.


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Parallel Flow Regenerative Shaft Kilns

Rectangular PFR Kiln

The simplest design of a PFR

Kiln is to place two shafts with

rectangular cross section side

by side lengthwise in such a

manner that the kiln gases can

flow directly from one shaft to

the other via a direct cross-over

channel. Because of its geom-etry this kiln type is simple to

manufacture with reduced re-

quirements for steel structure

and refractory materials.

This straightforward and cost-

efficient kiln type is mainly ap-

plied for output rates up to 400

tons of burnt lime or dolomite

per day.

As from 1966, Maerz has builtroughly 200 rectangular kilns

worldwide operating with gas-

eous, liquid and pulverised solid

fuels.

Circular PFR Kiln

For larger capacities, e.g. from

300 to 800 tons per day, kilns

of circular cross section are rec-

ommended. These kilns feature

circular ring channels collecting

the combustion gases before

they enter the non-burning shaft

via the cross-over channel. Thegases exit the burning shaft and

enter the non-burning shaft ra-

dially around the complete shaft

perimeter, thereby guaranteeing

an even heat distribution.

A bucket positioned vertically

above each shaft is used for

charging raw stone into the

kiln shafts. Stone distribution

is further improved by rotat-

ing the bucket during chargingfrom conveyor belts or vibrat-

ing feeders. The circular shaft

design facilitates uniform stone

and fuel distribution during

charging, as well as calcination

throughout the complete shaft

cross section.

Since 1966, more than 200 cir-

cular Maerz Kilns operating

with gaseous, liquid and pulver-

ised solid fuels, or a combinationof these, have been built world-

wide.

Finelime Kiln

Typical stone sizes processed

in conventional vertical shaft

kilns are larger than 30 mm.

Stone sizes of 6 to 30 mm can

be calcined in rotary kilns, but

with lower thermal efficiency. To

solve this shortcoming, Maerz

has developed a special type ofPFR Kiln the Finelime Kiln.

While maintaining the unique

features of PFR Kiln principles,

i.e. the parallel flow of material

and combustion gases in the

burning zone and the regenera-

tive preheating of combustion

air, the Finelime Kiln is able to

burn limestone sized between

approx. 15 and 40 mm at ther-

mal efficiencies superior to con-ventional PFR Kilns.

Since 1989 the year of its

introduction Maerz has built

approx. 35 Finelime Kilns world-

wide.

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Large photo

Rectangular PFR Kiln.

Fig. 1 Circular PFR Kiln.

Fig. 2 Finelime Kiln.

Fig. 3 Startup burner.

Fig. 4 Refractory lining

work.


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Fig. 1 Pusher of t he Preheater.

Fig. 2 View into a Rotary Kiln.

Fig. 3 Preheater Rotary Kiln.

Preheater Rotary Kiln

Preheater Rotary Kilns are the preferred

technology for the burning of limestone and

dolomite if the following conditions apply:

high production capacity, preferably

greater than 1,000 tpd

small stone feed size, e.g. 15 to 40 mm

maximum fuel flexibility

production of low sulphur lime (e.g. for

the steel industry) despite the usage of

cheap, high sulphur fuels.

The energetic efficiency of a rotary kiln is

highly enhanced by a shaft preheater that

uses the kiln off-gases to preheat and par-

tially calcine the limestone.

The modular preheater design most effec-

tively combines heat transfer with optimal

accessibility for maintenance during opera-

tion.

Our technology of preheater rotary kilns is

based on the joint know-how of Polysius

and Maerz.

Polysius contributes its broad knowledge of

rotary kilns and its R&D capabilities while

Maerz contributes profound process knowl-edge of lime burning such as gas flow pat-

terns in bulky material beds.


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Rotary Kilns

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Large photo New-Generation

Lime Shaft Preheater.

Fig. 4 The Sulphur Bypass System.

Sulphur Bypass System

Todays steel industry has a growing de-

mand for lime with minimal sulphur con-

tent.

Furthermore, the sharp increase in fuel

costs has created the necessity of looking

for cheaper fuel sources in order to limit

operating costs. Unfortunately, the usage ofcheaper fuels often means an increased in-

put of sulphur and other impurities into the

kiln system.

A special sulphur bypass system was

developed by Polysius to allow the firing of

high sulphur fuels for the production of low

sulphur lime in rotary kilns being equipped

with a shaft preheater.

In this novel system, the countercurrent

streams of material and kiln exhaust gasesare separated between preheater and rotary

kiln. The material is subject to a hot screen-

ing and classifying process.

The sulphur bypass system provides a very

effective solution to produce low sulphur

quicklime even when using highly contami-

nated fuels.


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Suspension Calciner

The POLCAL process was developed by

Polysius based on their extensive experi-

ence in the field of thermal treatment of bulk

materials acquired over many decades. It is

especially suitable for treating fine-grained

limestone and dolomite.

Materials within a grain size range of 0.03 to2 mm can be processed in this gas suspen-

sion process.

POLCAL systems have several vertically

arranged cyclone stages and a reactor for

thermal treatment of the raw materials as

well as one or several cooling cyclones to

cool the treated product. The individual

cyclone stages are interconnected by gas

ducts.

With production capacities ranging between300 and 1,200 tpd of burnt product, liquid,

gaseous and to a certain extent solid

fuels are applicable. The fuel is supplied

via several injectors arranged around the

reactor.

By varying the temperature and/or resi-

dence time in a conditioning drum installed

downstream the reaction chamber, the de-

gree of reactivity of the burnt material can

readily be adjusted to meet customer re-

quirements.


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Shaft Kilns Suspension Calciners

543

Large photo Single Shaft Kiln.

Fig. 1 Suspension Calciner.

Fig. 2 Cyclone of the Suspension Calciner.

Fig. 3 Detail of an Annular Shaft Kiln.

Fig. 4 Annular Shaft Kiln.

Fig. 5 Oil Burner of an Annular Shaft Kiln.

Annular Shaft Kiln

The Annular Shaft Kiln is characterised byits annular shaped shaft cross section lo-

cated between an outer and inner refractory

lined cylindrical steel shell.

The main feature of this kiln type is the

continuous stream of exhaust gases with a

high CO2-content, ranging between 26 and

32 %, depending on the type of fuel used.

Furthermore, the kiln allows the adjustment

of the reactivity of the quicklime produced

from soft to medium burnt. These charac-

teristics have made the Annular Shaft Kiln

the preferred choice for PCC and soda pro-

duction.

A wide range of fuels can be applied on this

kiln with production ranging between 200

and 600 tons per day.

Single Shaft Kiln

Special applications of lime, e.g. in the pro-duction of sandlime bricks and aerated con-

crete bricks or blocks, require hard burnt,

low reactivity quicklime. The RCE designed

single shaft lime kiln satisfies this require-

ment.

Based on the design of the RCE High Tem-

perature Kiln, mainly used in the refractory

materials industry for sintering magnesite,

dolomite and alumina, and in response to

market requirements, a high efficiency sin-

gle shaft kiln for the calcination of limestone,

dolomite and magnesite was subsequently

designed and patented. The main features

of this novel single shaft kiln type are:

the use of cooled, retractable side

burners

a wide range of product reactivity due

to the easy adjustability of operating

temperatures and

the high specific output per shaft

cross section.


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Services

Research and Development

Excellent technological competence is the key

to winning over and retaining customers as well

as to exploiting growth potential in existing and

new markets. Increasing the size of production

units and improving the operating economy

of production plants are main development

priorities.

Maerz makes use of the Polysius Research

Centre. With its modern equipment, this is one

of the leading institutions for technological

development in the mineral industry.

Customer Services

Maerz can assist their customers in many

different ways and offers the following services:

Project feasibility studies

Engineering services

Supply of key equipment for lime, dolomite

and magnesite kiln plants

Turn-key erection of complete kiln plants

Supervision services for erection, commis-

sioning and operation of kiln plants

Spare parts supply

Technical audits on kiln plants in operation

Training of operating and maintenance

personnel

After sales services including consulting for

operating and maintenance problems

Elaboration of modernisation proposals.


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The World Leader in Lime Kilns

References

About 500 new kilns for the lime and dolomite in-dustry have been built since 1950 in some 60 coun-

tries by Maerz, Polysius and RCE.

Since their introduction in the late 1950s, the Maerz

PFR Kilns have become standard equipment in the

lime and dolomite industry. Their superior thermal

efficiency, paired with the flexibility of being able to

apply virtually all types of fuel and raw materials,

has made them an excellent choice whenever the

installation of new calcining equipment is an issue.

For special applications, such as production capacities of more

than 1000 tons per day, the requirement to burn powdery raw

material or to produce low reactivity lime, a continuous off-gas

flow from the kiln with high CO2-content and the production of

low sulphur lime, rotary kilns, single shaft kilns, annular shaft

kilns and suspension calciners complement Maerzs product

Documents

Maerz Ofenbau Lime Burning Technology 2008 En