IPCC cement production based on clinker

The IPCC Tier 2 methodology represented herein calculates emissions based on the quantity and properties of the clinker produced, as well as an estimate of the emissions associated with the production of cement kiln dust.

This approach is based on the following assumptions about the cement industry and clinker production:

1. The majority of hydraulic cement is either portland cement or a similar cement, which requires portland cement clinker
2. There is a very limited range in the CaO composition of clinker and the MgO content is kept very low
3. Plants are generally able to control the CaO content of the raw material inputs and of the clinker within close tolerances
4. Even where the output of clinker is calculated by a plant rather than directly measured, there is generally close agreement between the two determination methods when audits are performed
5. The CaO content of clinker from a given plant tends not to change significantly over the years
6. The main source of the CaO for most plants is CaCO₃ and, at least at the plant level, any major non-carbonate sources of CaO are readily quantified (see Section 2.2.1.2 below)
7. A 100 percent (or very close to it) calcination factor is achieved for the carbonate inputs for clinker manufacture, including (commonly to a lesser degree) material lost to the system as non-recycled CKD
8. Dust collectors at plants capture essentially all of the CKD, although this material is not necessarily recycled to the kiln

Next, specify the quantity of clinker produced using the massClinker profile item value. The quantity returned represents the CO₂ emissions associated with the specified production, assuming default values for a number of clinker properties and no production of cement kiln dust.

Overriding default emissions factor

Users can override the default values for clinker calcium oxide (CaO) content and the proportion of this CaO which is sourced from carbonates, which are used to derive the emissions per unit of clinker produced.

The calcining of 1 tonne of limestone (CaCO₃) produces 0.5603 tonnes of CaO and 0.4397 tonnes of CO₂. It follows that the quantity of CO₂ emitted per tonne of CaO produced is 0.7848 tonnes. By specifying the proportion of CaO within the clinker, and the proportion of this CaO which was originally sourced from CaCO₃, the CO₂ emissions per unit mass of clinker can be derived.

To set the clinker CaO content, specify a decimal fraction (i.e. 0-1) using the clinkerCaOFraction profile item value. If left unspecified, this value defaults to 0.65 following IPCC guidelines. To specify the proportion of CaO derived from carbonate minerals, users can similarly specify a decimal fraction (i.e. 0-1) using the carbonateCaOFraction profile item value. The latter value defaults to 1 - i.e. 100% of CaO is assumed to be sourced directly from carbonates - if left unspecified.

Cement kiln dust

Users can also specify the some information relating to cement kiln dust which was not recycled to the kiln. Such dust represents feedstock 'lost' from the basic calculation, and so the emissions associated with this incompletely calcined dust are accounted for by deriving a correction factor which is applied to the primary emissions factor.

To incorporate the emissions associated with cement kiln dust, set the quantity of cement kiln dust not recycled to the kiln using the massCementKilnDust profile item value. Next, set the fraction calcination of the dust using the cementKilnDustCalcinedFraction profile item value. The calculation assumes that the proportion of original carbonate in the cement kiln dust is the same as in the raw kiln feed.