Large cement lines: just one process fan is enough

Air-handling specialist Venti Oelde can equip plant areas of large cement processing lines with only one single, powerful centrifugal fan (Fig. 1). When compared with using two combined centrifugal fans, the customer saves on investment, energy and space.

As a component of large cement lines with high flow volumes, the single powerful centrifugal fan offers numerous technical and economic advantages in comparison with two parallel operating fans. In cooperation with Venti Oelde, planners and plant constructors can depend on one large fan, even if the flow volume is higher than 1 000 000 m³/h.

For several years now larger and larger cement lines are being commissioned. Kiln lines with a capacity of more than 10 000 t/d are no longer a rarity. Plant components must, therefore, be correspondingly dimensioned. Typical examples of these components are raw mill and cement mill fans, kiln fans for pre-heaters or filter fans, for example for the cooler exhaust air from large filters.

 

Technology keeps up

Until about five years ago the great rotor mass of large centrifugal fans would have required the use of expensive slide bearings. For this reason, in the past two fans were usually used in parallel operation (Fig. 2).

In the meantime, how­ever, there are large-sized roller bearings available, thus considerably reducing the cost of the bearing units. These now make the economical operation of one large fan possible. Many years of operational experience have proved this technical solution to be effective.

 

Positive experience with

excellent performance

Venti Oelde heavy-duty fans have been successfully utilized in the cement industry for many years all over the world: for example, raw mill fans with flow volumes of up to 1 700 000 m³/h and a drive power of more than seven MW. Venti Oelde’s cement mill fans, kiln fans and filter fans can handle flow volumes of between 1 100 000 and 1 700 000 m³/h at a drive power of four, five or more MW.

 

A direct comparison

For instance, one raw mill fan downstream of a cyclone compared with two smaller fans makes clear the technical advantages and cost benefit (Tab. 1). Flow volume at the inlet, dust content, static pressure difference and inlet temperature are identical in both cases; rotation speed and shaft output with dust are, in the case of the single fan, pleasingly lower.

 

Enormous saving potential

In a direct comparison the example shows an energy saving of 396 kW, or of more than 5 %. Calculated on an annual basis the saving is 3300 MW. Based on an energy price of 8 Ct/kWh and 8400 hours of operation, the saving is about Euro 260 000 every twelve months. Furthermore, the CO2-emission is also considerably reduced, which is environmentally friendly and offers a further saving potential.

The use of only one large fan also lowers investment costs. An operator can save more than 8 % in comparison to two-fan operation.

 

Further advantages

Using a single large fan saves not only costs but also valuable space as well as reducing erection time (Fig. 3). Two parallel operating machines no longer have to be synchronised. Furthermore, less measurement and control equipment and noise protection measures are required. Moreover, pressure losses caused by additional ducting and bends are avoided. Finally, the technically mature technology ensures high availability and low maintenance effort.

 

Venti Oelde –

the air-handling expert

Venti Oelde has many years of experience in designing and constructing large fans. The company is well-known for its “large solutions”: apart from the cement industry Venti also supplies fans to the iron and steel industry, where, for example, there are sintering and pellet plants with flow volumes of up to three million m³/h in operation.

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