How to Control the Hot Meal

How to control the hot meal Pyroprocessing

PR-PYR P06-11 V1

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Introduction ƒ Every plant should determine the boundaries of their own process by taking regular samples of hot meal, measuring its Cl&SO3% and asking the operators in charge of tower cleaning, the type of build-up they encountered.

Prerequisites ƒ Combustion optimization ƒ Hot meal sampling procedure

1 How to sample hot meal Time frame ƒ Sampling & analysis should be done on a daily basis (3/day recommended).

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How to control the hot meal Pyroprocessing

PR-PYR P06-11

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Action Steps 1.

Sample & analyse ƒ Sample hot meal and perform analysis on a daily basis (3/day recommended). ƒ Keep record of the chemical analysis for investigation purposes. ƒ If available, SO2 gas analysis give the fastest indication for sulphur volatilisation level

2.

Set the limits ƒ Set the limit based on plant characteristic. Chlorine and SO3 maximum content can be different from plant to plant depending also on the existence of a bypass installation

ƒ Set plant limits for main fuel sulphur and make sure the purchasing department respect these limits. ƒ Establish limits for chlorine content in raw mix or alternative raw materials as well as in waste fuels

1 Example in the annex

3.

Develop a control chart ƒ Develop a chart of different quantities of volatile components and mark clearly on the chart, different zones of build up conditions.

ƒ With the above performance monitoring tools, adjust on appropriate levers discussed later in the document to achieve optimum conditions of operation.

1 Example of chart below Graph 1: for hot meal sulphur & chlorine versus area of no build-ups, minor build-ups, heavy build-ups etc…

Limits of coating tendency is based on general experience can be used as first indication of plant situation.

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How to control the hot meal Pyroprocessing

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PR-PYR P06-11

Action Steps Graph 2: Specific example of Sugar Creek Control chart.

With this graph Sugar Creek (USA) is following their own kiln specific coating tendency.

Last 7 Days of 5th Stage Samples 1,75

Chlorine (%)

Heavy Coating

Acceptable Coating

1,50

1,25

1,00

0,75

Known plugging zones!!!!

0,50

No Coating 0,25

0,00 00 3,

80 2,

60 2,

40 2,

20 2,

00 2,

80 1,

60 1,

40 1,

20 1,

00 1,

80 0,

60 0,

40 0,

20 0,

00 0,

Sulfur (%) Heavy Coating

4.

No Coating

2/16 to 2/24

Average

Optimisation of combustion ƒ Make sure the position of burner is optimized (align with kiln axis recommended but it depend on impulse level). Also make sure burner settings are adjusted for the type of fuel used.

ƒ ƒ ƒ ƒ

5.

Optimise the location of waste fuel injection to avoid fuel drop out Check the burning condition – O2 level Reduce coarse fuels with poor combustion properties Change on fuel or raw material promoting volatile cycles (if possible)

Build a plant procedure for Hot Meal ƒ Create a plant procedure for hot meal SO3 and Cl control that the operators should know how to react in case of limit exceeded.

Procedure Template developed by

How to control the hot meal Pyroprocessing

PR-PYR P06-11

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Appendix 1.

Example of a Plant Procedure for Hot Meal Cl > limit value : ƒ increase by pass rate ƒ change on fuel input or raw materials promoting Cl cycles ƒ increase cleaning cycle and inspection frequency on the preheater

SO3 > limit value : ƒ ƒ ƒ ƒ

2.

check the burning condition – O2 level reduce coarse fuels with poor combustion properties change on fuel or raw material promoting volatile cycles (if possible) increase cleaning cycle and inspection frequency on the preheater

Levers to adjust volatile content in hot meal ƒ If volatile content in hot meal exceeded the limit value, it is important to react promptly to determine the promoter of the volatile cycle and then to eliminate the source.

ƒ While for SO3 volatilisation there are levers to reduce the level of the phenomena (by adjusting the O2 level or flame), for Chlorine volatilisation there is nothing to do except removing the source. You have to react quickly because Chlorine-related problems often lead to plugging up of the cyclones.

ƒ Check for modification on raw mix composition (SO3, Cl, alkali) and try to adjust ƒ Check for main fuel sulphur. Alert purchasing department in case of sulphur exceeding plant limit. In both cases it can take a little time to adjust the volatile input. Meanwhile try to run with more oxidised atmosphere to reduce the volatilisation and , very important, intensify the cleaning cycle and the inspections on the preheater to remove as much as possible the build ups .

ƒ Check your combustion indicators (adjust O2 level properly, no CO, fuel dosing stability, raw mix uniformity).

ƒ In case of shredded materials fed to the back end, riser duct or precalciner, check the size of the shredded pieces and reduce the dimension if necessary, in order to eliminate local reducing conditions.

ƒ Evaluate the sulphur/chlorine input via fuels and try to reduce the one who is promoting SO3/Cl cycles. Poor fuel burnout in case of precalciner kiln can also cause high kiln inlet SO2. Try to optimise combustion in the calciner

1 How to optimise a precalciner.

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