Controlling Slagging and/or Fouling in Furnaces Burning Biomass

Abstract

The description relates to controlling slagging and / or fouling in biomass burning furnaces. Combustion of such a biomass the fuel with air produces combustion gases containing sodium and / or potassium compositions, and the combustion gases are treated by contacting the combustion gases with kaolin and aluminum hydroxide. At least one of the kaolin and aluminum hydroxide can be introduced with the fuel, in a combustion chamber, with reburn fuel or with overfire air. For fuels also high in zinc and / or heavy metals, magnesium hydroxide is introduced into the combustion chamber or following heat exchangers.

Description

FIELD OF THE INVENTION[0001]The invention relates to controlling slagging and / or fouling in biomass burning furnaces.BACKGROUND OF THE INVENTION[0002]Combustion of biomass is increasing because it is considered to provide significant greenhouse gas reduction benefits to the environment. Many advocate its use as being carbon neutral because biomass consumes the same amount of CO2 from the atmosphere during growth as is released during combustion. Advantageously, it can be blended with high-sulfur fuels, such as some coals, to achieve lower carbon and sulfur emissions than from the coal alone. In addition, biomass co-firing can also result in lower NOx because the flame temperature is typically lower and fuel nitrogen in biomass is converted to NH radicals by combustion, and this can reduce NOx by nonselective reduction.[0003]In the exemplary situation of factories or other industrial plants that produce large amounts of biomass waste and use it for fuel in combustors to supply heat a...

AI Technical Summary

Benefits of technology

The invention is about a method to reduce slagging problems when burning fuels that contain zinc and heavy metals. It suggests adding magnesium hydroxide to the combustion chamber or after heat exchangers. The dosage of magnesium hydroxide per ton of fuel should be between 0.5 to 7.5. The patent also provides some examples to explain the method. Overall, this method helps to reduce the slagging issue and improve the efficiency of combustion.

Problems solved by technology

In addition, biomass co-firing can also result in lower NOx because the flame temperature is typically lower and fuel nitrogen in biomass is converted to NH radicals by combustion, and this can reduce NOx by nonselective reduction.

In the exemplary situation of factories or other industrial plants that produce large amounts of biomass waste and use it for fuel in combustors to supply heat and / or electricity, there has been noticed a tendency toward slagging or fouling, but mainly fouling brought on by a mechanism known as sinter fouling.

While biomass fuels have many advantages, they are usually rich in potassium and / or sodium compositions, which can drastically change the character of the ash.

Potassium and sodium containing ash presents problems that have not been adequately controlled by existing technology.

The capture and phase state change of the potassium and sodium vapors is a problem for proper operation of a biomass fueled furnace, either partially or solely, because such reactions effectively cause a mechanism known as sintering fouling.

In bubbling and circulating fluidized bed boilers and furnaces, bed material may also be at the temperature zone required to cause potassium and sodium vapor condensation to occur, resulting in bed material agglomeration.

This can lead to further fouling.

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