Performance of an effectively integrated biomass multi-stage gasification system and a steel industry heat treatment furnace

• The challenges of replacing fossil fuel with renewable energy in steel industry furnaces include not only reducing CO2 emissions but also increasing the system energy efficiency. In this work, a multi-stage gasification system is chosen for the integration with a heat treatment furnace in the steel powder industry to recover different rank/temperature waste heat back to the biomass gasification system, resulting higher system energy efficiency.A system model based on Aspen Plus was developed for the proposed integrated system considering all steps, including biomass drying, pyrolysis, gasification and the combustion of syngas in the furnace. Both low temperature (up to 400 °C) and high temperature (up to 700 °C) heat recovery possibilities were analysed in terms of energy efficiency by optimizing the biomass pretreatment temperature.The required process conditions of the furnace can be achieved by using syngas. No major changes to the furnace, combustion technology or flue gas handling system are necessary for this fuel switching. Only a slight revamp of the burner system and a new waste heat recovery system from the flue gases are required.Both the furnace efficiency and gasifier system efficiency are improved by integration with the waste heat recovery. The heat recovery from the hot furnace flue gas for biomass drying and steam superheating is the most promising option from an energy efficiency point of view. This option recovers two thirds of the available waste heat, according to the pinch analysis performed. Generally, depending on the extent of flue gas heat recovery, the system can sustain up to 65% feedstock moisture content at the highest pyrolysis temperature studied.

Ämnesord

NATURVETENSKAP  -- Fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences (hsv//eng)

Nyckelord

Biomass gasification

Energy efficiency

Fuel substitution

Integration

Pyrolysis

Steel industry

Biomass

Carbon dioxide

Combustion

Flue gases

Flues

Fossil fuels

Fuels

Furnaces

Gasification

Heat treatment

Iron and steel industry

Steelmaking

Synthesis gas

Temperature

Waste heat

Waste heat utilization

Waste incineration

Waste treatment

Biomass gasification system

Biomass pre treatments

Combustion technology

Heat treatment furnaces

Pyrolysis temperature

Waste heat recovery systems

Heat treating furnaces

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