Incineration: Trend-setting for waste management

BONN: Where do we put the rubbish?

A worldwide question. The burdensome mountains of waste which we produce day by day are piling up to a problem. Fortunately, new technological solutions make pollutant-free disposal possible without big rubbish heaps.

The city of Bonn's waste concept is exemplary for an integrated utilization and disposal concept - an active contribution to environment protection with the following objectives: waste avoidance, collection and recycling of valuable materials, disposal of pollutants, environmentally sound incineration of unavoidable residual waste, energy-recycling through the gaining of long-distance heating and electricity, as well as the environmentally sound disposal of incineration residues through utilization or "absolutely safe deposit", as an engineer of the Mullverwertungsanlage (MVA) Bonn put it.

The city of Bonn, with its population of about 300,000 (in an area of 140 square kilometers), has to deal annually with about 130,000 - 140,000 tons of combustible residual waste for final disposal. Household rubbish makes up about 66 percent of this, business waste similar to household rubbish accounts for about 27 percent, and about seven percent is special waste.

Bonn's rubbish utilization plant is designed to handle an annual waste total of about 180,000 tons. The MVA operates 24 hours a day, including weekends and public holidays. The plant is made up of three totally separate and independent process chains, which consists of an incineration grate, a waste heat boiler and a multiple-stage flue gas dust collector. One of the three chains is always in reserve so that in the case of possible faults and inspections disposal security can be assured at all times.

The rubbish moves from the waste bunker to the waste oven where it is completely burnt at high temperature. The first cleansing of the smoke gases takes place in the furnace through a reduction of the toxic nitrogen oxides.

The remaining cinders reach the cinder bunker, from where they are directed to further utilization, and the energy freed by the waste incineration is delivered as steam to the neighboring heating power plant of the Stadtwerke Bonn. The multiple-stage flue gas cleansing begins with the entry of the flue gases into the spray dryer. In the following electro-filter the solid, dust- like particles are removed before the flue gases go into a three- stage flue gas wash. In the last stage follow the precipitation and destruction of the dioxins and furfuranes before the cleansed flue gases leave the plant via the 318-ft high chimney.

The waste problems which a few years ago appeared to be insoluble are being neutralized essentially by modern incineration plants and filter facilities, which in Germany are the precondition for the approval of such plants.

-- Inter Nationes