Biowanze, CropEnergies AG, Wanze, Belgium

Bran- and gas-fired boiler for bioethanol factory

In November 2006 we were awarded the contract for the supply of a bran- and natural gas-fired boiler for a new bioethanol factory under construction in Wanze, Belgium. The factory was commissioned in 2009.

The factory is owned by the German company CropEnergies AG and it is located near the Belgian town of Wanze. Each day it produces 758,000 litres, or 200,242 gallons, of alcohol. BioWanze is the largest supplier of bioethanol in Belgium and also one of the most innovative biomass plants in Europe.

BioWanze plant

A bran-fired boiler

The boiler is fired primarily with bran, which is a residue from the milling of wheat grain used for the production of ethanol. The steam from the boiler is expanded through a steam turbine to provide low pressure steam for the heating processes in the ethanol factory. The power is sold to the grid as green electricity. Usually, bran is used for cow feed, but the increasing amount of bran available and its favourable electricity prices have made the use of bran for generating power more profitably. The bran boiler is unable to supply all the required steam on bran only, and it was decided to use natural gas (n-gas) for the remaining energy input.

The n-gas is utilized in an external superheater and the flue gas is led to the bran boiler. The external n-gas superheater allows a compact design and high conversion of n-gas to electricity.

An increasing demand for bioethanol to be mixed with petroleum

The European initiative to increase the share of the energy consumption within the transport sector based on renewables to 6% has led to an increasing demand for bioethanol to be mixed into the petroleum. Bioethanol is a fossil free alternative to petroleum and BioWanze produces 758 m3 of ethanol per day.

The technologies used at BioWanze

The bran is delivered to the boiler-dosing silo and fed into the boiler with feeding screws. The combustion takes place on a water-cooled vibrating grate. This grate is very suitable of handling biomass of low calorific value (LCV).

In order to avoid clogging, the boiler is designed with two empty boiler passes to ensure sufficient cooling of the fuel gas before entering the convection part. The bran fuel is expected to generate fouling and slag on the walls in the empty boiler passes, which have therefore been equipped with water sooth blowers.

The flue gas from the external superheater is mixed into the bran boiler in front of the convection section. The boiler and economizer are the vertical type. The bottom ash is removed with a submerged chain conveyor and carried to an open ash pit.

What we supplied to the BioWanze bioethanol factory

  • Feeding silo
  • Vibrating grate
  • Boiler
  • External n-gas superheater
  • Dry flue gas cleaning
  • Instruments
  • Construction
  • Commissioning

BioWanze illustration

Plant design data

Process parameters Values Units
Nominal capacity 20 t/h bran
Heating values  13.5 – 17 MJ/kg
Steam flow  100  t/h
Bran boiler temperature  430 °C
Final temperature  520  °C
Pressure  93  bara
Feed water temperature 105  °C
Emission guarantees out of the boiler:
CO  145  mg/Nm3
NOx  278  mg/Nm3
Dust  18  mg/Nm3
NH3  30  mg/Nm3
HCI  25  mg/Nm3
SO 179  mg/Nm3
TOC  50  mg/Nm3

*) The emission values refer to 6% dry O2