preheatersandprecalciners (1)

7/21/2019 preheatersandprecalciners (1)

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PREHEATERS &

PRECALCINERS State of the art design

LUCY - Low pressure drop cyclones

NOxreduction

Burning of solid secondary fuels


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In modern cement kilns, the sintering

temperature is achieved by burning fuels in therotary kiln and precalciners. The raw meal ispreheated in the suspension preheater.

One of the benchmarks for any kiln is the

efficiency of heat transfer within the system.

PSP Engineering covers all of the equipment needed in a modern cement production plant:

Low pressure drop cyclones for modern

preheaters

Low NOxcalciners suitable for the

combustion of a variety of fuels including

difficult to burn solid secondary fuels

Rotary kilns with two or three support

configuration

Floating frame technology for kilns with

three or four roller stations

Ancillary components such as by-pass

systems, kiln inlet & outlet seals, chutes,

splash boxes, flaps, vortex finders and

dividers

State-of-the-art Pendulum Clinker Coolers

for optimum heat recuperation supplied inassociation with IKN

Modern firing systems for single fuels or for

a combination of fuels

The introduction of precalciner technology

successfully increased clinker productionwhile keeping the rotary kiln at a manageable

dimension. Precalcination rates in excess of

90% are achieved with roughly 60 % of the total

fuel directed to the precalciner.

Since combustion and precalcination of raw

material takes place outside of the rotarykiln, the heat loading of the rotary kiln can

be reduced. The use of shorter rotary kilns is

made possible.

The governing factor for the heat consumptionof any modern kiln is the performance of

the suspension preheater together with its

precalciner. Heat is released from the burning

process in the rotary kiln and precalciner andtransferred to the raw meal within the parallel

flow through cyclone stages. This heat transferis dependent on optimum meal distribution into

the riser ducts and the separation from the gas

stream in modern low pressure drop cyclones.

Each cyclone stage is sealed against gas shortcircuiting by a pendulum flap.

LUCY-type cyclone preheater with low pressure drop cyclones

Heat transfer takes place in the connecting

ducts among the various cyclone stages and is

dependent on:

Optimum meal dispersion into the gas

stream

Adequate residence time of the raw

material within the hot gas (parallel /co-

current flow pattern)

Efficient separation of raw meal at each

cyclone stage at lowest possible pressuredrop

While the number of cyclone stages

determines the specific fuel consumption, itstill is a compromise between the efficiency

of the preheater and drying requirements of

the raw meal. Cyclones with a high separation

efficiency and low pressure drop are typicallyused as the top-most stage, where separation

efficiency of 95 97% is required.

Kiln line for 1100 tpd with calcining system

KKN/AS for low NOx

3D model of a high separation cyclone for the

top stage of the preheater

3D model of a cyclone with low pressure drop

designed for the lower stages of the preheater

PREHEATERS

Preheaters

3D model of a five stage LUCY-type preheater

with calcining channel


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Preheaters

One criterion for designing the top-most

cyclone stage is applied to the lower cycloneswith the emphasis on minimising pressuredrop. The latest generation of PSP Engineering

cyclones reduces the overall pressure drop

by 20% compared with cyclones of traditional

design. Modern six-stage cyclone preheaterscan be operated with heat consumption below

690 kcal/kg.

Left: Where strong climatic differences cause

fluctuations in raw material moisture during

the kiln campaigns, split raw meal feed points

to the top and second up most cyclones is

considered. This switch over the lower fresh

feed points makes higher temperature exhaust

gases available by bypassing the top cyclone

stage.

Splash box

Adequate design of the splash boxesensures good distribution of raw mealinto the riser duct gas stream.

Cyclone flaps

Flaps with counterweights seal off thebottom of each cyclone to avoid shortcircuiting of process gases through

the cyclones, where the gas would re-

entrain material up to the next cyclone

stage. The flaps are designed for easyaccess and flexible adjustment. For

easy movement the flaps and their

counterweights are supported by knives

Segmented vortex finders

Vortexfinders are placed eccentricallyinto the spiral of the cyclone. The

vortex finders for cyclones of the lower

stages are made of cast segments with

a special alloy capable to withstand the

high temperature and chemical attacksfrom the kiln gas

Preheater LUCY with KKN/AS calcining system

in a 2700 tpd kiln line


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PRECALCINER

The modular design of the precalciners of PSP

Engineering permits a tailor made solution to

meet specific process requirements.

The design is ideal for the burning low grade

fuels or solid waste materials while providing

an efficient tool to control NOxemission.

The range of possible precalciner configurations:

Calcining channel

typeTertiary air duct

Burning of

secondary fuels

NOxreduction

capability

No. of calcining

stages

KKN-AT - Partially - 1

KKN-AS Yes Partially Yes 1

KS-AS-W Yes Yes Yes 2

The preheated material enters the calcining

channel at the inclined bottom part where the

burners are located. The shape of this lower

part of the inlet chamber warrants an efficientmixing of raw meal and fuel within the gas.

Recirculation ensures that heavier particles of

raw meal and/or fuel clusters remain here for

a longer period of time. The gas flow carriesthe raw meal particles upwards to the middle

part with its circular cross section.

This circular section transitions into a swirlhead. The swirl head forms the upper

part of the calcining channel. Combustion

and precalcination of the raw material

are completed in this intensely turbulentrecirculation zone.

Apart from the simple operation, the

arrangement of the precalciner channel

reduces overall heat consumption. The

temperature is controlled by introducing rawmaterial.

Advantages of the KKN-AT calcining channel:

Modular design allows for firing in the riserduct of up to 25% of the total fuel and easy

upgrading to precalciners with tertiary airduct

Innovative arrangements in a birds typeextension of an existing preheater tower

make KKN precalciner ideal equipment for

small scale upgrading projects.

A separate tertiary air duct supplies oxygen-richcombustion air to the lower part of the calciningchannel.The shape of this lower part of the

inlet chamber warrants an efficient mixing of

tertiary air, material and fuel. Recirculation

extends the residence time of heavier particlesof material and fuel clusters.

In case of NOxreduction, tertiary air supply is

split into the lower part and an additional supplyis introduced into the transition zone below the

swirl head.

The adjustable split ration between these two

entry points helps to control the generation of

thermal NOxwithin a reducing and an oxygen

rich atmosphere in the upper part of thecalcining channel.

The swirl head forms the upper part of thecalcining channel. Combustion is completed inthis intensely turbulent recirculation zone under

oxygen rich conditions.

Advantages of the KKN-AS calcin ing channel:

Firing of up to 60% fuel

NOxreduction

Innovative design allows to easily upgrade

an existing preheater tower

Maximum flexibility due to several fuel feed

points

Upgradeable with SNCR (Selective Non-

Catalytic Reduction)

Calcining channel KKN-ATcontains the

characteristic of a classic AT (air throughcalciner) where all the combustion air is drawn

through the kiln.

Calcining channel KKN-ASwith separate

tertiary air duct and with combustion air supply

above meal and fuel feed points

Calcining channel KKN-AT

Calcining channel KKN-AS

Precalciners


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The increasing demands for using differenttypes of fuels including solid waste materials

led to the development of precalciners that

reliably burn these types of fuels.

The KS-AS-W calcining system fromPSP Engineering is a two-stage system,

combining off-line and in-line calciner

technology. The combustion chamber is thefirst calcining stage, designed as an off-linecalciner suitable for the combustion of almost

any type of fuel, including hard-to-burn-fuels

such as larger size alternative fuels. Burning in

oxygen-rich air with a hot core in the centre ofthe chamber ensures quick ignition.

The walls of the combustion chamber are

protected by recirculating material. The

calcining channel together with its swirl headis the second calcining stage. The kiln exit

gas mixes with the gas and material streams

from the combustion chamber. Additional fuel

is introduced into the calcining channel. Thelayout of the calcining channel ensures long

residence time for optimum heat transfer and

good burn out rates, and NOxreduction.

Due to the high temperature core in thecombustion chamber a fuel mix of shredded

tires and a wide mixture of processed recycled

material such as plastics, wood, paper and

cloth can be fired. Temperatures of 1100-1200 C are measured in the core. Intensive

heat transfer in the chambers centre ensures

quick ignition of solid fuels. A meal curtain

maintains lower temperature along the walllining.

Precalciners

A combustion chamber with solid alternative

fuels feeding system

Calcining channel KS-AS-Wwith combustion

chamber and tertiary air duct for burning of

solid alternative fuels

A reconstructed preheater of a 4000 tpd kiln

with calcining channel and swirl head

Two-stage calcining system KS-AS-W

3D model of the KS-AS-W calcining system


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www.pspengineering.cz

Kiln systems/Preheaters & Precalciners_EN01/05

The producer reserves the right to modify products and/or their parameters without prior notification.

2005 PSP Engineering a.s.

PSP Engineering a.s. is a leading

supplier of specialized equipment

and complete production plants

for the building material and

mineral processing industries. PSP

Engineering has been involved in the

design and construction of cement

plants, lime works, quarry and crushing

plants, as well as gravel and sand pits

for more than 50 years.

preheatersandprecalciners (1)

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