Technical report of the BEUMER Group: Reliable energy supplier

The new business segment AFR systems at BEUMER Group makes it possible for

cement and lime plants to use alternative fuels:

Reliable energy supplier

Cement manufacturing is particularly energy-intensive. In order to reduce

the use of expensive primary fuels like coal and oil, cement plant

operators focus increasingly on alternative fuels and raw materials (AFR).

The use is generally focused on the fuels. Neither the manufacturing

process, the end product, nor the emissions may be affected. Therefore,

high-caloric wastes that cannot be further recycled, e.g. from plastic and

packaging residues, paper, composite material or textiles, have to be

treated beforehand to be ready for incineration.

In order to help customers efficiently convey, store and dose the treated

fuels, BEUMER Group has established the new business segment AFR systems.

Germany, October 1973: For political reasons, Arab countries reduced their

oil production, which caused oil prices to skyrocket. This was a very

precarious situation, because crude oil was an important energy source,

also for the cement industry to operate their rotary kilns. With this

first oil crisis, plant operators started to shift towards using

cost-effective fuels and raw materials.

Besides mineral waste that can be used as alternative raw material, the

market primarily employs the use of fuel alternatives, because

approximately 30 per cent of production costs are spent on energy. In

addition to fluid alternative fuels, such as used oil or solvents, the

majority of solid fuels consist of complete or shredded scrap tyres, scrap

wood, or mixtures of plastic, paper, composite materials or textiles.

After they have been treated and quality-controlled, they show calorific

values similar to brown coal. The calorific value of scrap tyres is even

comparable to that of stone coal. When producing cement, it is also

necessary to ensure that the quality of the ash residues matches the

quality of the end product. As all material components are completely

incorporated into the clinker and mineralised. Their use makes for an

economic production process. In addition, primary raw and fuel supplies

are conserved and landfill volume is reduced.

Pre-treated secondary fuels are mostly supplied from external vendors,

ready for incineration. BEUMER Group now offers tailor-made AFR systems to

lime and cement plants for the safe transport and storage of solid

materials. Based on wide-ranging experiences and the customer's

requirements, the systems comprise the entire chain, from receiving and

unloading the delivery vehicle, up to storing, sampling, conveying and

dosing solid alternative fuels. BEUMER Group, provider of intralogistics,

supplies its customers worldwide now with three systems, from one single

source.

Tailored to every application

BEUMER Group's program includes the starter system that is used at the

main burner. In the cement and limestone industry, primary fuels are

usually ground to grain sizes of less than 100 micrometres and fed via the

burner. At the end of the rotary kiln, the burner heats up to 2000 °C, the

temperature that is needed for limestone, sand, clay and ore to react and

become clinker as an intermediate product. In order to use solid secondary

fuels in the clinkering zone burner, they should deliver a calorific value

that is at least similar to brown coal (ca. 22 ± 2 MJ/kg), have grain

sizes of less than 30 millimetres and burn out while being fed.

The oven-ready material is usually delivered in moving-floor trailers.

BEUMER Group provides a docking station that also serves as storage on

site. Once the trailer is emptied, it is completely replaced or refilled

in the large tent using a wheel loader. The material is metered

volumetrically and conveyed to the clinkering zone burner. This solution

is deliberately designed as a test system. This way, the operator can test

their suppliers, the quality of the fuels and their furnace behaviour.

Solution for the calciner

With the second system, the calciner can be fed with more coarse

alternative fuels, such as tyre derived fuel or the fuels described above,

but in a more coarse state. They are generally less processed, contain

three-dimensional particles and therefore require more time to burn out

than for example the more intensively processed, exclusively

two-dimensional secondary fuels for the main burner.

The coarse calciner fuel is delivered in moving-floor trailers or tippers.

The secondary fuels are quickly unloaded and stored temporarily in a

dust-proof way. Another storage serves as a flow buffer, which can hold

the overall capacity of 900 cubic metres of the preceding bunker. From

here, the Pipe Conveyor transports the material to the calciner in the

preheater tower. Here, the secondary fuel is weighed and dosed. During the

feed towards the hearth in the calciner, there is often the risk that the

material or the conveying system can catch fire due to thermal radiation

or pulsations. For this reason, the valveless special feed was developed,

so the material can be safely fed to the calciner.

In order to ensure safe and automatic fuel supply after successful

testing, BEUMER Group provides systems for permanent operation with high

thermal substitution rates. The systems consist of the receiving area and

a storage system, where the crane system can store material of different

quality into different storage zones and boxes. Experiences so far have

shown that you always have to calculate with disruptives or quality

deficits in the fuel. This is why the entire storage and conveying

technology in the hall can be provided with equipment that is able to

separate metal, wet and three-dimensional disruptives from the fuel for

the main burner and keep disrupting oversized grains from the calciner

fuel.

Equipped with the necessary sensor technology, the operation runs

automatically. The crane can be used independently for homogenisation, in

order to minimise quality variations or feed the lines towards the main

burner and the calciner.

Pipe Conveyor stands the test

Schwenk Zement AG's product diversity and production capacity make their

plant in Bernburg one of the largest and most efficient cement plants in

Germany.

In order to reduce energy costs, the cement plant is increasingly using

secondary fuels that are engineered in external processing plants into

high-quality fuels with defined product parameters.

Until now, the manufacturer had been using drag chain conveyors. After

almost a decade of use and numerous modifications however, more and more

maintenance was required. The fuel quality also improved over time, so

that, due to its density of 0.2 t/m3, the existing technology was no

longer sufficient to convey the required quantities towards the main

burner. This created the need for a reliable, eco-friendly and

low-maintenance solution. In addition, the new conveyor needed to be

optimally adapted to the curved routing in the plant.

Schwenk Zement KG opted for the BEUMER AFR system with its Pipe Conveyor

to feed the main burner with alternative fuels. The system works almost

completely automatically, from receiving to the feeding system of the

rotary kiln. Cranes pick up the engineered secondary fuels in the

storehouse and fill them into the discharge bunkers with their discharge

equipment. From there, a chain belt conveyor transports the fuel

continuously towards the Pipe Conveyor, which conveys it to the weigh

feeders before the main burner.

The curved Pipe Conveyor at the core of the system requires little

maintenance and its enclosed design and quiet operation protect against

emissions and the wind-blown dispersal of the fuel. It is able to connect

long distances without interruption and navigate tight curve radii that

adapt to the individual conditions of the plant.