Pyrolysis process utilizing pyrolytic oil recycle

In a continuous process for producing a solid residue and a clean, enriched gaseous product from a cellulosic material that pyrolyzes to a solid residue and a gaseous mixture, which gaseous mixture comprises condensible organic vapors, water vapor, and noncondensible fractions, the steps comprising:

• (a) continuously pyrolyzing a feed of said cellulosic material as a moving packed bed in which the temperature varies, and passes through a maximum value of about 760.degree. to 1150.degree. Celsius at an intermediate level, to produce said residue and said gaseous mixture, said gaseous mixture having entrained therein a significant amount of fine particles of said residue, and having a temperature of about 110.degree. to 400.degree. Celsius;
• (b) injecting pyrolytic oil into said gaseous mixture to scrub said residue particles therefrom and to effect condensation of a portion of said condensible vapors thereof, thereby enabling recovery of a relatively clean gaseous product and a pyrolytic oil mixture containing said residue particles;
• (c) filtering said pyrolytic oil mixture to separate it into an oil portion and a filter cake, said filter cake containing pyrolytic oil and residue particles in a weight ratio of about 1 to 10:1;
• (d) recycling said filter cake by introducing it into said bed for treatment in said step (a);
• (e) recycling said oil portion of said pyrolytic oil mixture to provide said injected pyrolytic oil of said step (b);
• (f) effecting the condensation and recovery of a substantial amount of the organic vapors and water vapor present in said gaseous mixture subsequent to said step (b);
• and
• (g) recycling at least a portion of the condensate from said step (f) by injecting it into said residue at the bottom of said bed to effectively quench said residue, said recycling steps being controlled with respect to the rate of introduction of said cellulosic feed material so as to produce an enriched gaseous product, and a net yield of pyrolytic oil amounting to at least 3 percent based upon the weight of said feed.

In a continuous process for producing a solid residue and a clean, enriched gaseous product from a cellulosic material that pyrolyzes to a solid residue and a gaseous mixture, which gaseous mixture comprises condensible organic vapors and water vapor, and noncondensible fractions, the steps comprising:

• (a) continuously pyrolyzing a feed of said cellulosic material as a moving packed bed in which the temperature varies, and passes through a maximum value of about 760.degree. to 1150.degree. Celsius at an intermediate level, to produce said residue and said gaseous mixture, said gaseous mixture having entrained therein a significant amount of fine particles of said residue, and having a temperature of about 110.degree. to 400.degree. Celsius;
• (b) injecting pyrolytic oil into said gaseous mixture to scrub said residue particles therefrom and to effect condensation of at least a portion of the condensible fraction thereof, thereby enabling recovery of a relatively clean gaseous product and a pyrolytic oil mixture containing said residue particles;
• (c) filtering said pyrolytic oil mixture to separate it into an oil portion and a filter cake, said filter cake containing pyrolytic oil and residue particles in a weight ratio of about 1 to 3:1;
• (d) recycling said filter cake by introducing it into said bed at a subsurface level at least about two feet below the surface of said bed, above said intermediate level and at which the temperature is at least about 260.degree. Celsius, for cracking of said oil contained in said filter cake;
• (e) recycling said oil portion of said pyrolytic oil mixture to provide said injected pyrolytic oil of said step (b), said recycling steps being controlled with respect to the rate of introduction of said cellulosic feed material so as to produce an enriched gaseous product, and a net yield of pyrolytic oil amounting to at least 3 percent based upon the weight of said feed.

In a continuous, substantially non-polluting process for producing a solid residue and a relatively dry, purified gaseous product from a cellulosic material that pyrolyzes to a solid residue and a gaseous mixture, which gaseous mixture comprises condensible organic vapors and water, and noncondensible fractions, the steps comprising:

• (a) continuously pyrolyzing a feed of said cellulosic material as a moving packed bed to produce said residue and said gaseous mixture, said gaseous mixture having entrained therein a significant amount of fine particles of said residue;
• (b) injecting pyrolytic oil into said gaseous mixture to scrub said residue particles therefrom and to effect condensation of a portion of said condensible vapors thereof, thereby enabling recovery of a relatively clean gaseous product and a pyrolytic oil mixture containing said residue particles;
• (c) removing said residue particles from said pyrolytic oil mixture to provide an oil portion;
• (d) recycling said oil portion of said pyrolytic oil mixture to provide said injected pyrolytic oil of said step (b);
• (e) effecting the condensation and recovery of a substantial amount of the organic vapors and water vapor present in said gaseous mixture subsequent to said step (b), to produce a purified gaseous mixture;
• (f) recycling at least a portion of the condensate from said step (e) by injecting it into said residue at the bottom of said bed to effectively quench said residue;
• and
• (g) effecting the condensation and recovery of water vapor remaining in said purified gaseous mixture to produce a relatively dry, purified gaseous product and a relatively clean wastewater stream.