Pyrolysis Processes in the Absence of Oxygen

3 Pyrolysis Processes in the Absence of Oxygen Thermal Black Process 

The thermal black process operates discontinuously and generally utilizes natural gas as a feedstock. A production unit consists of two cylindrical furnaces connected to one another, in which refractory bricks are piled one on top of another for heat storage with a large cavity in between. The two furnaces are operated alternately while the first furnace is being heated to the reaction temperature (ca. 1300 to 1500°C) with a stoichiometric mixture of air and combustible gas (mainly natural gas), natural gas is fed into the second already heated furnace and is thermally pyrolyzed. Since the reaction is endothermic, the furnace cools and the gas flows are switched when a critical minimum temperature is reached and the first furnace utilized, while the second is heated up again. The cycle time is about 5 minutes. 

The reaction products are quenched by water sprays in a cooling zone and the carbon black separated in filter units. The yield is ca. 35% of the carbon content of the feedstock and combusted gas. The residual gas consists almost entirely of hydrogen and can be mixed with natural gas for heating the furnace or for diluting the gas to be pyrolyzed. Coarser carbon black is produced than in the lamp black process, with primary particle sizes of 120 to 200 nm or 300 to 500 nm being attained depending upon whether the natural gas is diluted with inert gas or not. 

Acetylene black process operates continuously by exothermic pyrolysis of acetylene 

In the acetylene black process the tubular reactor only has to be heated once to 800°C by the combustion of an acetylene/air mixture. The pyrolysis reaction is then carried out with pure acetylene, which proceeds strongly 

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