WE’RE ON FIRE FOR THE MOST EFFICIENT LIME KILNS. · PDF filelime bricks. THE PFR KILN....

W E ’ R E O N F IR E F O R

T H E M O S T E F F IC I E N T L IM E K I L N S .

E V E RY Y E A R , M O R E T H A N 3 0 0 M I L-

L I O N T O N S O F L I M E A N D D O L O M I T E

A R E B E I N G C A L C I N E D. M O S T LY I N

M A E R Z K I L N S .

For over 3000 years, burnt lime has been a basic

material in the construction business. Today, it is

also an important component for the chemical indus-

try, agriculture and especially for the steel industry.

Maerz kilns calcine the largest share of the amount

needed worldwide – more than kilns from any other

manufacturer. There are good reasons for the suc-

cess that Maerz kilns enjoy: Highest efficiency.

Lowest energy consumption. Broad range of kiln

types. Individual solutions depending on location,

raw material and available fuel. Maerz’ portfolio

comprises all modern kiln types.

02 |

T H E H P S K I L N .

F O R H A R D - B U R N T L I M E , T H E L O W-

R E A C T I V E Q U I C K L I M E .

The HPS kiln from Maerz functions on the principle

of counter flow. Combustion gases flow from bottom

to top traversing the feedstock; while fuel is only

added towards the end of the burning zone. Upon

completion of the combustion process higher energy

input can be used to raise the peak temperature in

the burning zone: Thus, the CaO crystallites fuse

and reduce the specific surface of burnt lime. This

process produces low reactive lime, which is ideal,

e.g., for the production of aerated concrete and sand

lime bricks.

T H E P F R K I L N .

F O R S O F T- B U R N T L I M E , T H E H I G H -


The PFR kiln from Maerz is ideal for the production

of soft-burnt lime. The lime is calcined in a parallel

flow. The feedstock and the combustion gases move

in the same direction from top to bottom. The energy

needed for the calcination is supplied at the begin-

ning of the calcination process. This ensures that

the peak temperature in the burning zone is low

enough so that the resulting CaO crystallites do not

fuse. The specific surface of burnt lime thus remains

intact. This burnt lime is highly reactive and ideal,

e.g., for the steel industry.

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Temperature in °C

Time in hours

Typical Temperature Profile in a Single Shaft Kiln

04 |

Tim

e in

hou

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Temperature in °C

TYPCIAL TEMPERATURE PROFILE OF A MAERZ PFR KILN. TYPICAL TEMPERATURE PROFILE OF A MAERZ HPS KILN.

Temperature in °C

Tim

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0.00

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17.500 400 800 1200 1600 0 400 800 1200 1600

Feedstock Exhaust gases Air

Feedstock Exhaust gases Air

com

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flow

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air

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air/

gas

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THE PFR K ILNS FROM MAER Z.

EFF IC IENT PRODUC T ION OF L ARGE

QUANT I T IES OF BURNT L IME .

A PFR kiln (parallel flow regenerative shaft kiln) con-

sists of two vertical shafts and a connecting cross-

over channel. Both shafts work with each other.

While one calcines the product, the other preheats

the stone. In the burning shaft the lime is calcined

in parallel flow. The hot combustion gases are then

transferred through the crossover channel to the

non-burning shaft where they preheat the limestone

in counter flow in the upper area of the shaft. The

flow direction of the gases is reversed at regular

intervals. This allows the regenerative preheating of

the stone to take place (the stone in the preheating

zone of the kiln acts as heat exchanger) and thus

for the maximum use of the heat contained in the

kiln gas.

The principle of calcination in parallel flow is ideal

for the production of high-reactive quicklime. A PFR

kiln from Maerz processes up to 800 tons of burnt

lime per day. Gaseous, liquid or pulverised solid fuels

as well as different combinations of these may be

used. Depending on the required output and grain

size of the limestone to be processed, Maerz designs

rectangular, circular or Finelime PFR kilns.

| 05

®

T H E R E C TA N G U L A R P F R K I L N F R O M

M A E R Z . F O R U P T O 4 0 0 T O N S O F

B U R N T L I M E P E R D AY.

The most cost-efficient and simple design of a PFR

kiln: two burning shafts with a rectangular or hexa-

gonal cross section are placed next to each other.

Through a direct crossover channel the combustion

gases flow from one shaft to the other. The rect-

angular cross section simplifies the fabrication of the

kiln by imposing fewer challenges on the steel con-

struction and the refractory material. This simple

and cost-efficient PFR kiln is usually used for outputs

of up to 400 tons of burnt lime per day. Since 1966,

Maerz has installed more than 200 rectangular PFR

kilns worldwide.

06 |

T H E C I R C U L A R P F R K I L N F R O M

M A E R Z . F O R U P T O 8 0 0 T O N S O F

B U R N T L I M E P E R D AY.

For the production of larger capacities of burnt lime

per day (300 to 800 tons) Maerz recommends PFR

kilns with a circular design. These kilns have a circu-

lar shaft cross section and circular ring channels for

gas flow. In these channels the combustion gases of

the burning shaft are collected before flowing through

the crossover channel to the non-burning shaft. In

the non-burning shaft the hot gases in turn flow

through the circular ring channels along the whole

circumference of the shaft. The circular shaft cross

section and the gas distribution along the whole cir-

cumference of the shafts ensure an even heat distri-

bution in large kilns – indispensable for high lime

quality. Since 1966, Maerz has installed more than

300 circular PFR kilns worldwide.

| 07

T H E F I N E L I M E K I L N F R O M M A E R Z .

S O Y O U C A N M A K E B E T T E R U S E O F

Y O U R L I M E S T O N E D E P O S I T S .

Limestone that is calcined in conventional shaft kilns

usually has a grain size of more than 40 millimetres.

Smaller-grained stones, not more than 6 to 50 milli-

metres in size, are often calcined in rotary kilns –

which, however, feature very high heat consumption.

To solve this problem, Maerz developed a highly

specialised PFR kiln: the Finelime® kiln.

How does it work? The special geometry of this kiln

and the special charging of the feed material guar-

antee ideal heat distribution, even when processing

small-grained stone.

The principle of the PFR kiln, i.e., the calcination of

lime in one shaft and the preheating of the stone

with the hot kiln gas in the other shaft, is also used

in the Finelime® kiln. Thus its heat consumption is

significantly lower compared to rotary kilns. Since

1989, when it was first introduced onto the market,

Maerz has installed approximately 60 Finelime® kilns

worldwide.

08 |

®

T E C H N I C A L D ATA .

R E C TA N G U L A R P F R K I L N . C I R C U L A R P F R K I L N .

F I N E L I M E K I L N .

| 09

KILN TYPESRECTANGULAR

PFR KILNCIRCULAR PFR KILN

FINELIME® KILN

KILN TYPE E1 – E6 R1 – R5 F1 – F3

CAPACITY(tons per day)

100 – 400 300 – 800 200 – 400

GRAIN SIZE(mm)

30 – 120 30 – 160 15 – 40

HEAT SUPPLY(kJ/ kg)

(kcal / kg)3390 – 3650810 – 870

3390 – 3650810 – 870

3310 – 3560790 – 850

MAIN PRODUCTHigh-reactive

quicklimeHigh-reactive

quicklimeHigh-reactive

quicklime

®

T H E H P S K I L N F R O M M A E R Z .

F O R T H E C A L C I N AT I O N O F L O W-


Low-reactive burnt lime is used for the production

of sand lime bricks, aerated concrete bricks and

aerated concrete blocks. Previously, no modern

shaft kiln was really well adapted to the production

of low-reactive burnt lime. This is why Maerz de-

signed, constructed and patented a new single-shaft

kiln, the HPS kiln (high-performance shaft kiln). It

consistently delivers low-reactive burnt lime with

the best quality and the highest energy efficiency.

Maerz HPS kilns feature:

• Use of cooled burner lances, which protrude

into the hot bed of material and are

adjustable.

• Precisely adjustable operating temperature

resulting in individual specific product

reactivity.

• Highest specific heat load in correlation to

shaft diameter and thus highly compact design.

10 |

H P S K I L N S: T E C H N I C A L D ATA .

| 11

HPS KILN

KILN TYPE H1 – H5

CAPACITY(tons per day)

100 – 300

GRAIN SIZE(mm)

10 – 80

HEAT SUPPLY(kJ/ kg)

(kcal / kg)4100 – 4610980 – 1100

MAIN PRODUCTLow-reactive

quicklime

S P E C I A L P R O D U C T S F R O M M A E R Z .

PFR and HPS kilns are not everything. Maerz also

offers other kiln types for specific purposes. For

instance the annular shaft kiln for all applications

requiring a continuous stream of exhaust gases and

a high CO² content in the exhaust gas. We can also

process fine-grained limestone or sand in our

suspension calciner POLCAL®. And last but not least

we have developed a technology for preheater rotary

kilns, which enables the use of cheap fuels with high

sulphur content without raising the sulphur level in

burnt lime. Ask us if you are looking for a special

solution.

E X P E R I E N C E A N D R E S E A R C H

F U E L E A C H O T H E R . F O R C O N S TA N T

I M P R O V E M E N T O F Q U A L I T Y.

Maerz has already built more than 600 lime kilns

worldwide. More than any other manufacturer. We

have gained a lot of experience from this, yet we

continue to drive our research and development.

With each kiln that we build we continue to refine

new technologies and to surpass ourselves.

Thanks to its sophisticated technology and wide

range of different kiln types, Maerz became the

leading supplier for the global lime kiln market. Each

kiln can be individually adapted to suit all the re-

quirements and conditions imposed by the location,

e.g. the altitude above sea level, the quality of the

lime-stone or the available fuel.

Maerz knows all about the different types of lime-

stone and dolomite. Globally. Before designing a new

plant, we carry out tests in our laboratories with the

stone to be calcined. Thus we can adapt each plant

perfectly to its purpose – and make it the ultimate

benchmark for all relevant criteria.

H I G H E S T E N E R G Y E F F I C I E N C Y.

W I T H E V E RY F U E L .

Maerz PFR kilns achieve the highest thermal effi-

ciency of any modern lime kiln: more than 80 per

cent. We not only promise you this figure. We achieve

it with fuels such as:

• natural gas

• heavy fuel oil

• pulverised coal

• liquefied gas

• off-gas from steel-making process

• wood dust

• waste oil

• as well as with a combination of various fuels.

12 |

| 13

L O W E S T C O N S U M P T I O N O F F U E L A N D

E L E C T R I C A L E N E R G Y.

The typical heat consumption (based on the fuel’s

lower calorific value) lies between 3480 and 3850 kJ

(830–920 kcal) per kilogram or 2.99 to 3.32 MBtu

per short ton of lime, depending on the chemical

analysis and the grain size as well as the type of fuel

used. The consumption of electrical energy depends

on the grain size, the fuel and the kiln’s altitude

above sea level. The consumption amounts to 25 to

45 kWh per ton of lime.

E M I S S I O N L E V E L S T H AT A R E A L S O A N

A D VA N TA G E F O R T H E E N V I R O N M E N T.

In PFR kilns there is no open flame with a high tem-

perature. This is why hardly any nitrogen oxides are

produced. The flames in the kiln are entirely sur-

rounded by material with a lower temperature. The

stone directly absorbs the heat for the calcination

process. Thus the peak flame temperature is reduced

– along with the formation of nitrogen oxides. The

interaction of all components and the fine-tuning of

the lime plant also play their part in achieving low

emission levels.

14 |

M A E R Z ’ C U S T O M E R S E R V I C E

O P E R AT E S J U S T A S I M P E C C A B LY A S

I T S K I L N S D O . G L O B A L LY.

Maerz supports its customers in different ways –

anytime, fast and everywhere. Also after the com-

missioning of a turnkey plant. These are the services

Maerz offers:

• Feasibility studies for your project

• Planning and engineering of lime kilns and

entire lime plants

• Turnkey assembly of lime kilns and entire lime

plants

• Support with assembly and commissioning

from our specialists

• Technical training of your employees for

operation and maintenance

• Supply of spare parts

• After sales service including consultation on

operation or maintenance issues

• Suggestions on how to modernise existing

plants, e.g. by retrofitting to adapt to different

fuels or by modernising the control system

B E T T E R S A F E T H A N S O R RY.

A reliable control system monitors and controls the

operation of the plant. It also operates unmanned.

Should a serious incident arise, the kiln will shut

down automatically. Constant control also means

prevention of breakdowns and thus more efficient

operation.

S M O O T H P R O J E C T H A N D L I N G

F R O M A T O Z .

Maerz meets all customer requirements and fulfils

all expectations – thanks to our experience, know-

how and a wide range of different kilns. And also

because we are Swiss. We keep our promises. We

deliver excellent quicklime quality and efficiency in

plant operation, on time and on budget.

WE’RE ON FIRE FOR THE MOST EFFICIENT LIME KILNS. · PDF filelime bricks. THE PFR KILN....

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Transcript of WE’RE ON FIRE FOR THE MOST EFFICIENT LIME KILNS. · PDF filelime bricks. THE PFR KILN....