Heat and Power Production from Straw

Abstract

The fact that from 1990 the burning of straw in the fields is no longer permitted has accelerated the development of efficient and reliable Danish heat and power plants using straw.

Today about 30 district heating plants (2–10 MW thermal) are producing low price energy for the customers. Futhermore 4–6 combined heat and power plants (5–30 MW thermal) will be constructed during the next 2–3 years.

The combustion technique is based upon three main principles using:

• Chopped straw

• Whole big bales

• Grated big bales

The boiler temperature should be higher than 800–1000°C to provide a satisfactory combustion reducing the emission of carbonmonooxide, unburned particles and dioxin. However the low softening temperature of the straw ashes (850–1100°C) leaves a rather narrow temperature interval for the optimal combustion.

Economically straw firing is rather profitable especially due to the Danish energy tax on oil. An “average customer” may save approximately 20% every year.

A future aspect is combined heat and power production using straw. Steam production and gasification are two of the possibilities being tested in the Danish demonstration programme sponsored by the Danish Energy Department and the Power Plants. An electrical power of 450 MW based on domestic fuels is the target of the programme.