Air Emmisions

As the world begins to focus on the impact that mankind is having on our planet, particularly the threat of global warming, various industries are making profound efforts to minimise their environmental impact and provide more benign and constructive alternatives towards improving their manufacturing processes. This is a key focus area of the SA cement industry. Essentially, the ACMP is trying to combat two major sources of air emissions generated by the cement manufacturing process: Particulate Emissions, and Greenhouse Gas Emissions. It should be noted that in both instances the ACMP has made great strides in reducing the impact of these as will be documented below.

  

a). Particulate Emissions Particulate emissions can be broken down into two categories: Fugitive Emissions (dust), and Point Source Emissions (from kiln exhaust and milling plant stacks) The ACMP has significantly reduced overall particulate emissions to the atmosphere (for example, Holcim’s Dudfield kilns 2 and 3). In some instances these are significantly below the national requirement and comparable with the best international legislated requirement. (South African legislation demands that producers measure and report on point source particulate emissions, according to the conditions prescribed in their Air Registration Certificates). In many instances the use of bag house filters is currently reducing Particulate Emissions to levels equivalent to world best practice. In so far as Point Source Emissions are concerned, the installation of appropriate filter equipment, including cyclones, electrostatic precipitators or bag house filters, is paying dividends.  The modern cement manufacturing plant has in excess of 200 bag houses suppressing dust.

b). Greenhouse Gas Emissions
The correlation between greenhouse gas increases in the atmosphere and ‘Global Warming’ is well documented. The ACMP supports the urgent need to reduce global CO2 emissions and has successfully initiated programmes to contribute towards this international drive.


 

PPC Dwaalboom Batsweledi Project The PPC Dwaalboom project involves state-of-the-art technology that includes vertical roller mills, a low NOx in-line precalciner, a six stage preheater and the latest crossbar grate cooler. The upgraded plant will be energy efficient and will operate at significantly improved emission levels.

c) Other Emissions

Manufacturing cement also contributes to other emissions, such as Oxides of Nitrogen (NOx), Oxides of Sulphur (SO2) and emissions of various other streams such as H2O, HCI, NH3, HF, organic compounds and metals.

In the case of NOx (formed by the reaction of nitrogen and oxygen from the air used for combustion) this is formed largely in the high temperature zone of the main flame. However, a number of ACMP members have been able to reduce their NOx emissions by:

• Implementing advanced kiln management systems, and

• Installing specifically designed, low NOx burners and pre-calciners

SO2

In so far as SO2 emissions are concerned, these are low. This is attributed to the scrubbing effect brought about between the kiln exhaust gas passing through the finely milled raw meal (largely limestone) in the kiln and the kiln preheater tower. In addition, South African cement manufacturers use raw materials that contain very little sulphur. However, it should be understood that SO2 emission levels are subject to the quality of the raw materials used in the cement manufacturing process.

Further promising news is that all ACMP members will be adopting new measures that will ensure uniform reporting standards and future industry setting of goals. These measures are being developed by an environmental committee developed for the South Africa Cement Industry Emission Measuring and Reporting programme.