New Concept: Waste Heat Utilization During Clinker Cooler Dedusting

Depending on its design, a clinker cooler generates approximately 1.4 – 2.0 Am3 of exhaust air per kilogram of clinker. During normal operation, this exhaust air has a temperature of circa 220 – 300 °C and a dust load of circa 10 mg/Nm³.  During upset operation, these values can increase for short periods of time to 450 °C and 30 g/Am³.

The primary objective of exhaust gas cooling - to conform the gas temperatures to the economically available filter media (defined filter intake temperature) and achieve the associated reduction in the exhaust gas volume flows to be cleaned - is based initially on economic reasons. However, since the cooling of process gases releases significant amounts of energy, our commitment to environmental awareness also leads us to regularly include options for regenerative waste heat utilization in our concepts. As an example: the cooling of 200,000 Am³/h of dry air by 100 °C corresponds to a thermal output of circa 3.5 megawatts [MW].

The New Concept for Waste Heat Utilization
The cooling of exhaust gases during clinker cooling dedusting is accomplished primarily through the use of an air/air heat exchanger. The heat exchanger transfers the heat to the cooling air. In this concept, the heat introduced into the cooling air is transferred to a thermal loop and subsequently made available for use as energy. The additionally installed air/oil heat exchanger is also operated using only heated cooling air and not with the exhaust gas flow. This ensures high operating safety and reliability because contamination and deposits are excluded. Further, in contrast to the process gas integrated variant with a pre-separation stage using a cyclone group, this method of heat extraction offers the additional advantages of lowering pressure losses and reducing the need for additional machinery and dust transport devices, which results in lower investment costs.

The heat recovered in this way can be used to dry raw materials, for pre-heating fuels (especially secondary fuels) or for space heating, whereby a constant transfer of heat is an important prerequisite. Depending on the way in which the energy is used, the additional costs for air/oil heat exchangers and piping are amortized within a few months. Upgrading to this method of heat recovery is also recommended in the case of existing air/air heat exchangers because of the low cost and the method’s significant economic benefits.

Newsworthy: Orders Already Received For Two Projects
Two new projects are already in the engineering or delivery phase following this previously presented, new concept for waste heat utilization during the clinker cooler dedusting process. In one of the projects, for example, unused heat will be recovered using an air/air heat exchanger to cool exhaust gases to a maximum temperature of 130 °C. In the future, this will recover a total of 1.3 MW of energy that will be used to pre-heat heavy oil.

In another project, Scheuch is integrating a two-stage air/air heat exchanger that includes a heat displacement system for later utilization of energetic heat. Scheuch is also implementing a new EMC filtration plant with 8-meter filter bags for this project.