RED RIVER IN CLINKER COOLER

1. Fine dusty clinker2.Segregtion in kiln due to

wide range in particle size.Material characteristics ,

and rotation of kiln

3. Cooler design,air flow distributionNon-uniform clinker bed

4.Operation and maintenanceof cooler

Hot fine dust , wide granulometry in size and the consequent segregationare the key reasons for the red river formation in coolerWhen the cooling air tries to penetrate the closely packed fine clinker dust layer the air gets heated and expands manifold in volume , fluidizes dust and it stars flowing like water much faster than the grate speed and stops when it becomes black with bubbles. The shear stress exerted by theair results in kinetic energy of the mass, like thixotrpic in non newtonianfluids. Higher the shear force ( here air flow velocity ) higher the fluidityover a period of time.Finer and hotter the dust the more it shoots like flooded wild river.Some designers tried to put some dam ring in conventional grate coolersor flow arrestors on its way to reduce its velocity but it did not helpas it jumps over the hurdles. This hot clinker dust erode and burn the plates .These are the reasons that make the cooler designers to inventnew generation coolers .The stationary inclined grates with control flow aeration and controlled flow air regulators reduced red river problems considerably .In some new generation also coolers the problems still exists.

Reason for red river

1.Dusty clinker and improvements

To day it is common problem that clinker is dusty. In 1 mm sieve, if pass- through is

15-20 % it is a normal clinker. In classic wet process the clinker nodules are

very good like pebbles. In this dry process with precalciner and higher production ,the

fines generation is on the higher Side. Volatiles like sulfur ,alkalies and alternate fuels

further aggravate this . Forced kilns and reduced conditions are also key reasons for

dusty Clinker. Ring formation in the outlet or in the burning zone deteriorates

nodulisation and force the kiln to operate on higher rpm which shifts clnker discharge

away from center of the cooler

• The nodulisation can be improved by modifying Alumina and silica

ratio, to great extent. Optimise the liquid with right viscosity yield good nodules

• Grinding the raw meal finer helps too especially when quartz and calcite are present .

• Good homogenised raw meal having standard deviation in CaO <0.2 and

SiO2 < 0.02 will reduce dust fraction in clinker.

• Addition of mineralisers like MgO , if limit allows, improve the nodularity.

• Intense convergent flame without impinging the charge also helps to reduce

the fines in the clinker.

• Higher rpm aids good nodulisation but not more than requirement and with

11-12% filling.

There are many more reasons for poor nodulisation.

In 1 mm sieve if the pass through is around 15 % is

Normally considered to be good clinker.

Q

Q1>Q2

<Q3

More escape Of cooling airLess recuperation

good nodulesBest

recuperation

Less passageOf air, onlyfluidisation occurs

Bad recuperation

0.2* D

This segregated fine

Dust causes red river

Least ResistanceTo air flow

More resistance

To air flow

100 75 50 25 20 15 10 5 2 1 0.1 0.5 0 mm

Un cooled

area(lumps

and big balls)

Reddsh core

When broken

Best recuperation area

Red river area

Cooling efficiency curve

Segregation inside the kiln at the discharge end

The hotter fine dust, it gets lifted farther up inside the kiln and good nodules cascade

farther down which results in segregation. If the kiln has shark teeth at the kiln tip

it becomes worse which results in more intense red river or even snowman formation.

Higher rpm also aids segregation .Higher secondary air velocity causes circulation of

fine dust between cooler and kiln which makes dust more sticky. Secondary and

Tertiary air take off velocity in the hood is to be less than 5 m/s.The fine dust falls

on towards the rotation side of the kiln. Though theCooler center point is offset

by 0.2 D of kiln , expecting center of clinker Discharge and center of cooler falls on

the same line but it never happens .Technology has not been fully developed to

have uniform clinker distribution on cooler grate But the cooling air distribution has

been achieved by mechanical air flow Controllers which regulates air flow depending

upon the resistance created by Clinker bed and its packing density. Latest generation

coolers like SF cooler, IKN pendulum , Eta cooler and pyro floor are already in use.

This helps in reducing the red river problem or at least reduction In cooler grate

Plate damage considerably.

bad distributionbetter distributionBest distribution worst distribution

Required rpm High rpm Very high rpmHigher rpm

Normal segregation High segregation Higher segregation Very high segregation

Influence of Kiln rpm on particle segregation and distribution of clinker bed in cooler

New generation cooler

Mechanical flow regulators in the new generation coolers optimise the cooler

Air flow avoiding starvation or excess flow. This can be rearranged in either case

altering the orifice size.

Mechanical air flow regulators

Automatic air flow regulator installed underneath the grates

Solution

The ultimate solution is to produce good nodules. Coolers are designed for good

Nodules and 25 mm is the reference .Modify the chemistry with good

homogenisation to get good uniform nodules .

Good convergent flame in center of the kiln , without impinging on charge reduces

dust fraction .Oxidised conditons in burning zone will have control over volatiles

Which improves nodulisation.

Distribution of coolng air helps to reduce the red river . Combination of stationary

Inclined KIDs and controlled air flow regulators in the rest of the grate reduce the

Redriver.

Narrow down the stationary KIDS with thicker clinker bed , atleast 600-700mm

thick bed helps further.

Thank you for your kind attention

- K.P.PRADEEP KUMAR