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Alkali - Sulfur - Chlorine Balance

A kiln can look stable while sulfur and chlorine are quietly building a circulation. This balance follows the material flows through the kiln system, checks whether the numbers close, calculates the chlorine actually reaching the high-temperature zone, and shows where the present situation sits against the selected kiln criteria. Press YOUR BALANCE on the board to enter your plant data.

Why this matters now

Alternative fuel rates keep rising and the chlorine, sulfur and alkali that come with them decide whether the kiln runs or blocks. Most plants find the limit by hitting it.

What this tool helps decide

See what is building up in the kiln before it closes the preheater, and how much alternative fuel the chemistry will actually take.

What subscription adds

Track the circulating elements kiln by kiln over time, keep each balance against the date it was measured, and hand over a report that shows the trend rather than one reading.

Connected to the industry conversation on alternative fuel substitution, chlorine bypass and kiln stability reported in World Cement, CemNet and Global Cement.See process-tool plans

Where your elements are going

The kiln

The workbook criteria and input labels change with the kiln type.
Daily production.
kJ/kg clinker.
m.
m.
Use the oxygen level relevant to the selected kiln system.
%.
%.
%.
%.
%.

Fuels

Fuel type / CV / S / rate / fineness
FuelCV kJ/kgS %t/hFineness %<90µm

Stack emissions

ppm dry at measured O₂.
% O₂.
ppm dry at measured O₂.
% O₂. Leave blank to use SO₂ O₂.

Kiln feed

t/h, dry basis as fed.
%.

Dust flows

t/h, separate from kiln feed.
t/h as fed.
t/h. For the boundary this is an output and is removed from the net input.
t/h to cement / sale / disposal.
Dust chemistry: SO₃ / K₂O / Na₂O / Cl / LOI

Hot meal / grate dust

Available for suspension and grate preheater systems. If you have two preheater strings, enter both; the tool uses the same 50/50 averaging convention as the workbook.
String 1
String 2 (optional)
KILN SYSTEM BALANCE BOUNDARY KILN FEED raw meal + included dust FUELS SO₂ / HCl stack emissions DUST REMOVED DUST REUSED / RETURNED CLINKER measured output HIGH TEMPERATURE ZONE
THE BALANCE
THE KILN HEALTH CHECK
Mass balance error
—
Relevant Cl input
—
Clinker SO₃
—
Alk / SO₃ ratio
—
Sulfur volatility
—
Calculated Cl in clinker
—
Calculated heat
—
Clinker Na₂Oeq
—
Total SO₃ input
—
Total Cl input
—

Main results

Material balance, point by point

What to do about it

How the numbers are worked out

Boundary. The supplied program uses the kiln system as the practical balance boundary. Kiln feed, other dust input and fuels cross into the boundary; clinker, bypass/intermediate dust, filter dust flows and SO₂/HCl emissions cross out. This makes the balance representative of the actual kiln system while avoiding the sampling burden of raw materials before the mill.

Mass balance. The tool compares total input and total output. The supplied handbook states that a good balance should close with a mass-balance error below 3%.

Calculated chlorine in clinker. Calculated Cl = all Cl inputs − all Cl outputs except clinker. The result is then expressed as g Cl/t clinker. The handbook emphasizes that this calculated value is useful, but the relevant Cl input is more important when assessing additional chlorine-containing fuels.

Relevant chlorine input. Relevant Cl = all Cl inputs − Cl in reused dust − Cl emission. It represents the net chlorine actually reaching and passing through the high-temperature zone. The applicable limit changes with kiln type and dust-removal/reuse arrangement in the supplied workbook.

Alk/SO₃ ratio. Following the workbook: [(K₂O/94) + (Na₂O/62) − (Cl/71)] × 80 / SO₃. The corresponding Na₂O equivalent is K₂O × 62/94 + Na₂O.

Sulfur volatility. Where hot-meal data are available, the workbook uses the clinker and hot-meal SO₃ and LOI values to estimate the fraction of sulfur evaporated. A value above 0.7 is flagged in the supplied handbook as an indication of poor combustion and possible causes include burner alignment/setting, long lazy flame, low kiln-inlet oxygen or lump fuel.

Sampling discipline matters. The handbook recommends stable kiln conditions, a mass-balance error below 3%, and balance errors below 20% for SO₃, K₂O and Na₂O in a good balance. Chlorine error can be higher. For blockage/coating assessment it gives a typical 8-hour balance with hourly sampling.