EMC: 8 m filter bag achieves best results in practice

In 2005, ThyssenKrupp India commissioned Scheuch GmbH, of Aurolzmünster, Austria, to supply a filter system for dedusting a new clinker kiln line (production rate: 7500 t/d) for Gulf Cement Company at Ras al Khaimah/United Arab Emirates.

 

Selection criteria

The decisive factors in the award of this contract were, on the one hand, the 8 m filter bags planned by Scheuch for this ­application, which would permit a compact design for the EMC filter and reduce the system‘s footprint to around a third compared to the reverse air filter originally envisaged. Other concomitant benefits include significant savings for the filter substructure, foundations, access facilities (structural steel) and extraction elements. In addition, the guarantees (for a period of three years) offered by Scheuch for differential pressure, bag service-life, compressed air consumption and cleaned gas residual dust content, with a much higher face velocity compared to competing bidders, were also critical in the decision in favour of EMC technology (Table 1).

 

Technical solution

Scheuch’s EMC filter was equipped with 8 m long filter bags and designed for a maximum air flow rate of 1 550 000 Am³/h (direct operation). In view of local climatic conditions and the need to conserve limited natural resources, the decision on cooling of the waste gases in direct operation was in favour of the addition of fresh air. The use of fiber glass bags with a PTFE coating permits filter inlet temperatures of up to 250 °C under continuous operation conditions.

 

Project implementation

In addition to the EMC filter system itself (Fig. 1), Scheuch’s scope of supply also included the entire filter hardware, compressed air supply, the filtration control and dust extraction systems, instrumentation, supervision of installation, and commissioning, the latter being completed on time in December, 2006. A performance test (Table 2) conducted jointly during commissioning confirmed the high efficiency of EMC technology, and the fulfillment or even improvement of all the promised guarantee values, such as a residual dust content in the cleaned gas of < 1 mg/Nm³ and a filter differential pressure well below 15 mbar. Scheuch also provided special training courses for the operating staff covering the operation, maintenance and supervision of the system.

Results after 39 months

A concluding performance measurement was performed in the presence of GCC in February of this year, at the end of the guarantee period (Table 2). The results had been recorded during the three years of operation and guarantee period by a special DATALOGGING system in the EMC filtration control system (Fig. 2), and were therefore foreseeable.

All the data measured confirmed trouble-free adherence to the values guaranteed at award of contract, despite the fact that the kiln‘s daily output had in the meantime been increased from 7500 to 8400 tonnes. Face velocity in compound operation is 0.9 m/min. (95  % of operating time) for a total pressure drop across the filter of < 11 mbar. The current data for face velocity in direct mode of operation is 1.3 m/min. (5  % of operating time) for a total pressure drop across the filter of < 15  mbar, with simultaneous non-destructive cleaning of the filter bags at a pressure of < 3.0  bar. Cleaned gas dust concentration at the stack is < 1.0  mg/Nm³ in both modes of operation. It was thus possible to maintain the guaranteed cleaned gas dust content (<  5.0  mg/Nm³) without difficulty throughout the guarantee period.

 

Analysis of the filter bags (Fig. 3) showed that they are still in extremely good condition, despite the greatly fluctuating operating conditions. The original bags can be expected to remain in operation for at least ­another 12 months, following completion of the guaranteed 36 months. This underlines the optimum dimensioning of this filter installation, the non-destructive cleaning performance of EMC technology, and the correct selection of the filter medium.

 

Gulf Cement Company has from the inception been extremely satisfied with Scheuch’s EMC technology for kiln dedusting and praises the supplier for its high technical standards and capabilities, including its activities in the construction and commissioning of the installation.

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