Because of the temperature peaks of 500 °C and higher that occur in upset mode, in most cases Scheuch installs an air/air heat exchanger upstream of the bag filter for gas cooling purposes. It is critical that this system has a carefully designed control and safety concept that enables the heat exchanger to respond to upset mode in good time.
The main benefits that EMC technology offers in clinker cooler dedusting applications are the significantly longer service lives of the filter bags and the reduced differential pressure levels – resulting in reduced operating costs throughout the plant's life cycle.
EMC filter technology from Scheuch has revolutionised dedusting in the cement industry and set new standards in bag length, pressure loss, cleaning pressure and bag service life. The results point to a clear reduction in life cycle costs (LCC). Thanks to its patented status, EMC is unique and is deemed to be the Best Available Technology (BAT) for process filters – even when compared with electrostatic and reverse-air filters. More than 200 EMC filter plants installed within the first ten years of this technology outline its pre-eminent status worldwide.
The Scheuch IMPULS filter is a high-capacity filtering separator that delivers outstanding cleaning performance combined with an excellent degree of separation. It is used for the dry separation of solid matter, primarily in the extraction of contaminants from machinery and the workplace, as a process filter in material recycling, or for conveyed material separation purposes.
Thanks to the specially shaped twin nozzles on the jet pipe, the pulsed free jet pulls along an envelope of clean gas from the primary compressed air as it makes its way to the injector. The two gas flows are mixed in the injector by means of pulse exchange and, at the same time, experience a significant increase in pressure. This ensures highly efficient cleaning throughout the bag length and filter bags that require cleaning less frequently.
Proven in practice for decades, the IMPULS cleaning system has become a byword for low operating costs:
A plant's ability to demonstrate a high level of safety and reliability is essentially dictated by its key components. The radial fan is one of the components at the heart of every extraction, dedusting, exhaust and flue gas purification, and pneumatic conveying plant. It helps to meet customer requirements with a level of quality that guarantees fault-free operation and excellent performance between maintenance intervals.
When it comes to ensuring availability and operational safety in dedusting plants, conveying mechanisms are just as crucial as fans and filter systems.
All conveying mechanisms can also be used in explosive, dust-laden atmospheres as defined in Directive 94/9/EC (ATEX).
In the cement industry, rotary valves are used as continuous discharge or dosage devices with slight negative pressure/overpressure for air exclusion purposes. The advantages of rotary valves lie in their comparatively low construction size combined with a high, speed-dependent conveying output, their ability to be used in a wide range of temperatures and with various pressure differences, and the relatively low energy costs associated with them.
Tube-type and trough screws are used to continuously transport bulk materials, at throughput volumes of 2 to 500 m³/h and with screw diameters between 200 and 1000 mm.
The longer the material conveying path and the higher the quantity of material that needs to be transported, the more sensible a choice high-pressure systems become. The main components of these are a high-efficiency rotary blower plus a rotary valve and an injector. Together, they ensure efficient conveying even when dealing with significant material quantities. High-pressure systems are ideal for use with conveying quantities of 1 to 100 t/h, conveying systems of up to 1500 m in length, and nominal widths between 88 and 500 mm.
Material loading stations consist of a rotary valve with an injector directly attached to it. The rotary valve loads the material into the pneumatic conveying system in a controlled manner. If it needs to handle items that cause wear, the system can also be lined with special materials.
Some years ago, virtually all kiln and clinker cooler filters – as well as some cement mill filters – were the electrostatic precipitator (ESP) type. As these have become unable to live up to growing requirements relating to emission limit values as well as operational safety and availability, however, electrostatic precipitators across the world are steadily being converted into bag filters. Compared with electrostatic precipitators, these ensure significantly lower clean gas dust loads and a consistent degree of separation.
The result is that almost every customer today plumps for the bag filter variety when installing new kiln filters.
Electrostatic precipitator housings are generally very tall in comparison to bag filters, making them ideal for conversion to EMC filters with bags which, over time, have grown to as much as 12 m in length. Excellent use can be made of the available space without the need to extend the housing – saving costs and cutting down on assembly time as conversion can usually be carried out during a scheduled inspection.
Thanks to Scheuch's comprehensive modular system comprising a range of filter head widths and bag lengths, it is possible to find exactly the right module for any housing dimension and thus maintain the required filter area. During the process of planning the engineering work for the conversion, a CFD flow analysis is performed where necessary in order to ensure a uniform inflow for all filter bags.
In heat exchangers, heat from exhaust gas is transferred to cooling air. The most common type of heat exchanger is the air/air type, which in most cases is operated in cross-flows or cross-counterflows. It is the ideal choice for dry exhaust gases. The gas to be cooled is led inside the pipe by inflow hoods, and ambient air is used to cool it in the external cross-flow by means of axial fans. Air/air heat exchangers (one or several) can be used on both the exhaust gas side and the cooling air side, depending on what the application requires.
The primary purpose of exhaust gas cooling is to adapt the gas temperatures in line with whichever filter media are available at an economically viable level (i.e. the defined filter inlet temperature) and, as a result, to reduce the exhaust gas volume flows that are to be cleaned. Therefore, the initial focus is on economic measures.
Since significant quantities of energy are released during the process of cooling process exhaust gases, however, we also consider how to make our systems more environmentally friendly and take advantage of regenerative waste heat utilisation in our concepts. As an example, cooling 100,000 Nm³/h of dry air by 100°C corresponds to a heat output of approximately 3.5 megawatts [MW].