What are the advantages of downdraft gasifier?
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What are the advantages of downdraft gasifier?


Downdraft gasifiers are used as a solution for tar problems in the gas stream. This design of gasifier is also called a parallel flow gasifier. Here, air/oxygen is introduced above the oxidation zone. The generated generator gas or syngas is discharged from the bottom, causing the gas and fuel to move in the same direction. As the fuel and gas are in motion, the distillation products and acids are converted into gases such as methane, carbon monoxide, hydrogen and carbon dioxide.


What are the advantages of downdraft gasifier?

1.Easy configuration and operation of the gasifier

2.High plant efficiency

3.Relatively low oxidant (oxygen or air) requirements

4.Less complex feedstock preparation using coarse feedstock particles

5.Produces gas at relatively low temperatures, thus eliminating the need for expensive high-temperature heat recovery equipment

6.Feedstock flexibility

7.High “cold-gas” thermal efficiency, when the heating value of the produced hydrocarbon liquids is accounted for

8.High methane content in product gas

9.Long feedstock residence time in gasifier and slag flow characteristics require carefully controlled feed size distribution for proper operation

10.Hydrocarbon liquids such as tars and oils are produced; increased effort to clean produced gas if it is used for applications other than direct heating


How does the gas move in a downdraft gasifier?

In this type of gasifier, the incoming solid fuel moves downward with the gas through the drying zone, the pyrolysis zone, the oxidation (combustion) zone, and the reduction zone. In the drying zone, the water is evaporated and the solid fuel is dried.


How does a downdraft gasifier solve the tar entrainment problem?

Solutions to the problem of tar entrainment in the gas stream have been found through the design of parallel flow or downdraft gasifiers where primary gasification air is introduced into or above the oxidation zone in the gasifier.


Can downdraft gasifiers be operated with slag fuels?

Downdraft gasification reactors are able to operate with slag fuels if they are specially modified (continuous moving grate and/or external pyrolysis gas firing).