Method and system for cleaning of and heat recovery from hot gases

Abstract

Exhaust gas, produced in a thermal reactor (1) that is fed with solid fuel can be cooled and in a gas cooler (4) which produce a condensate that is further cooled in a condensate cooler (7) which produce energy. By using air moisturizing and particle separation technology the exhaust gas and the excess condensate can be clean and the energy efficiency of the plant can be increased. The method can be used for a broad spectrum of fuels and conversion technologies.

Description

[0001]This invention relates inter alia to a method and a system for cleaning of and heat recovery from hot gases, e.g. flue gas, produced in a thermal reactor, or—more specific—using water to cool and clean gases, released by thermal conversion (gasification or combustion) of fuels e.g. biomass, waste, coal, oils, gases or mixtures of these, by having three process steps:[0002]Removal of contaminants (particles, salts, acids etc.) from gas in a water based scrubber;[0003]Removal of contaminants of the scrubber water by use of centrifuges and / or hydro cyclones;[0004]Heat recovery of the energy obtained in the scrubber water.[0005]Furthermore, the invention relates to methods and systems for[0006]Moisturizing the air for a thermal reactor in two moisturisers[0007]Removal of particles in the scrubber water[0008]Recirculation of particles from the scrubber to the fuel system.[0009]In an overall perspective, the invention may be seen as relating to handle particles in water which partic...

AI Technical Summary

Problems solved by technology

The water is usually heated in a closed circuit and led to a point of consumption, after which the water is returned to the heat production unit after release of the thermal energy.

The restriction to cool the gas is normally:The temperature of the return water of the district heating networkOutdoor air, and in this case the heat energy of the gas is wasted.

But thermal reactors have restrictions on the type of fuel to be used.

Especially bag filters and electrostatic filters are very effective towards particulate filtration, whereas cyclones and scrubbers typically are less effective, but also normally cheaper.

When scrubber water is not regularly cleaned, the particle and salt content may become rather high, and the scrubber water may cause re-entrainment of contaminants into the gas.

When scrubber water is loaded with particles the scrubber-district heating heat exchanger may have a short lifetime as coarse particles erode the heat exchanger.

Hydro cyclones are not used in condensing scrubbers as the water fractions with the high particle load needs further filtration, and therefore are the hydrocylone not cost efficient.

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