Cement Plant

A Research Study on Heat integration at a Cement Plant

As far as the cement making industry in the world is concerned, ingenious scientists have consistently devoted time to research on better and more advanced ways of cement making.

As a result of this, two primary technological advancements have been suggested for getting carbon dioxide from the cement plants, and these are Post-Combustion Capture (PCC) and oxy-firing.

At first, scientific studies and research were by no means favourably disposed to the idea of using the Post-Combustion Capture for Cement production as they (studies) favoured the oxyfuel capture technology.

The reason for this was because of the estimated high cost involved which led to the assumption that an auxiliary gas-fired boiler would be needed to provide the heat for removing carbon dioxide. With this impression, the idea of making opportunities for heat generation was virtually nonexistent.

However, from research, it appears that the Post-Combustion Capture is just the perfect technology in an Integrated Cement Plant  because it does not require any far reaching overhaul of the cement making process.

The post-combustion capture technique is not entirely pitch perfect as it has its challenges which are attributable to the fact that it requires rather outrageous amounts of low-grade heat to resurrect the solvent once the carbon dioxide has been removed from the flue gas.

The inspiration behind the research which led to the discovery of these innovative means of cement making is attributable to the pressing need to discover other ways in which waste heat from a cement plant could be utilised to meet the energy requirements for post-combustion capture.

One of the most pertinent questions at the research stage was the question of how much power could be obtained using the waste heat from an Integrated Cement Plant.

From the research, it was discovered that there are three possible ways through which significant amounts of heat could be lost in the cement plant, and they include: through the Preheater, Through the Kiln and the cooler.

The total heat losses from the cement plant were estimated alongside how they could be used to reform solvent. Flowing from the estimations and calculations using particular media or conditions, it was discovered that only a third of the heat losses were available for the application of post-combustion capture.

In furtherance of the research, three different scenarios which cut across various stages of heat recovery coupled with the impacts of improved solvents and the use of the different fuels in the kiln were tested.

Using the models, four different changes were observed to discover how to increase the amount of carbon dioxide captured using waste heat from the plant.

The changes are as follows:

The First Change is the conversion of the fuel from coal to gas, and at this stage, there was no glaring variation of the carbon dioxide captured through the post-combustion capture process.

The second change is in the form of the inclusion of heat losses from the experiment, and this resulted in a remarkable increase in the heat losses in a day which in turn led to an increased percentage of the produced carbon dioxide.

The third change is to move to a larger and more commercially available solvent with a lower recycling rate.

This in effect, means that by the use of less recycling energy, the waste heat could be used to process more solvent and this ultimately led to a remarkable increase in the post-combustion capture rate by 35.5%.

From the experiment and research, the final stage would be the replacement of amine-based solvents with ionic liquids which have been shown to have lower regeneration requirements. The use of these ionic liquids with lower renewal requirements would result in an irreversible increase of captured carbon dioxide to about 89%. The figures used in the research are a bit on the moderate side.

Hence, if more following values are used, it is possible that higher levels of heat could be recovered from the Integrated Cement Plant leading to an even greater amount of carbon dioxide recovered.

On a final note, a major challenge obstacle to the post-combustion capture method of cement production in cement plants is the fact that the process is quite financially demanding and as such, it would be necessary to develop cheaper ways to capture the heat.

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