Continuous feed pyrolysis chamber for decomposing solid waste

A pyrolysis reactor decomposes solid organic waste materials by heating the materials with a fast fluidized particulate source of heat which are admitted to one end of a chamber through first and second inlet pipes. The products of decomposition together with the particulate source of heat are removed through an outlet pipe at the other end of the chamber. The chamber has an intermediate section adjacent the inlet pipes of reduced diameter forming a throat which improves the mixing of the heating particles and the organic waste particles for faster heat transfer.

FIELD OF THE INVENTION 
This invention relates to solid waste disposal systems, and more 
particularly, to a continuous flow chamber for the pyrolysis of solid 
organic waste. 
BACKGROUND OF THE INVENTION 
The disposal of wastes both from municipal and industrial sources, such as 
trash, rubbish, garbage, animal wastes, agricultural wastes, and waste of 
plastic processing operations is rapidly becoming of immense national 
concern. The cost of disposal ranks third behind public schooling and 
highways as municipal expense in the United States. 
It is estimated that each individual in the country generates between 4 and 
6 pounds of waste per day, that the industrial output is equivalent to 
approximately 5 pounds of solid waste per person per day. Previous methods 
of mass waste disposal, such as landfill, are becoming impossible, while 
others such as incineration are costly and result in air pollution 
problems. 
A vast majority of the waste which is presently disposed of contains 
products which are immediately recyclable back into the economy or 
products into which the waste can be converted for recycle back to the 
economy. Directly recyclable constituents are the various metals present, 
such as aluminum and steel, and glass. For the most part, the organic 
solid waste fraction is subjected to flash pyrolysis as an operation 
independent of recovery of the directly recyclable inorganic fraction and 
any organic portion recovered as pulp. Flash pyrolysis yields carbon 
containing solid residue of pyrolysis or char, condensible pyrolytic oils 
and combustible gases. 
In the flah pyrolysis process, particulate solid organic waste which 
includes particulate inorganic constituents, a particulate source of heat, 
the carbon containing solid residue of pyrolysis and/or an inorganic heat 
source formed by decarbonization of the carbon containing solid residue of 
pyrolysis, and a carrier gas which is nondeleteriously reactive with 
respect to the pyrolysis products, are combined and passed under turbulent 
flow conditions through a pyrolysis zone maintained at a temperature from 
about 600.degree. to about 2200.degree. F or in the instance of the 
inorganic heat source, below its fusion temperature, i.e. 
1425.degree.-1450.degree. F. The preferred temperature range is from about 
800.degree. to about 1350.degree. F. The carbon containing solid residue 
of pyrolysis with the solid source of heat after separation from the 
pyrolytic oils and gaseous components is reheated as part of a loop, by 
total or partial combustion and decarbonized to the particulate source of 
heat for recycle back to the pyrolysis zone. 
In the pyrolysis process, the solid organic waste exists as discrete 
particles having a diameter less than 1 inch, and are preferably of a size 
less than about 5 mesh, preferably less than 8 mesh. The particulate 
source of heat, e.g. the carbon containing solid residue of pyrolysis 
(char) and/or the inorganic heat source (ash) formed by carbonization of 
the former, for ease of mass transport, is generally of a particle size in 
the range from about 10 to about 1,000 microns. Although any carrier gas 
which is nondeleterious, i.e., essentially oxygen free, to the products of 
pyrolysis may be used as a transport gas for both the organic solid waste 
and the particulate source of heat, it is preferred for expediency in the 
process to use the gases which are the byproducts of the pyrolysis 
operation itself. 
In the process, the organic solid waste which is normally at a temperature 
from ambient to about 100.degree. F must rapidly be heated to the 
pyrolysis temperature. Heating of the organic solid waste occurs 
predominately by solids to solids contact with the particulate inert 
source of heat. Thorough mixing under solid transport conditions within a 
fraction of a second becomes essential. 
The present invention is directed to an improved pyrolysis reactor which 
enables a continuous pyrolysis reaction under flow conditions with a 
single pass of the particulate organic feed in contact with the 
particulate source of heat within a relatively short chamber at residence 
times of a fraction of a second. 
SUMMARY OF THE INVENTION 
The present invention provides a transport flash pyrolysis reactor having 
an elongated three zoned vessel with first and second inlets at one end 
and an outlet at the other end. Fast fluidized inert hot particulate 
source of heat flows continuously through the chamber from one inlet and 
organic solid waste particles are introduced in the other inlet and 
combined in a first blending zone where pyrolysis is initiated. Thorough 
mixing of the particulate solid waste and particulate source of heat is 
achieved by providing an intermediate zone of reduced cross-sectional area 
adjacent the blending zone. The reduced cross-sectional area zone 
substantially increases the relative velocity of the solid particulate 
source of heat and the organic solid waste to increase the turbulence of 
the flow and thereby induce intimate mixing to increase the rate of 
solid-to-solid heat transfer which occurs within the remaining length of 
the reactor. As a consequence, residence time required for pyrolysis is 
reduced to a fraction of a second.

DETAILED DESCRIPTION 
Referring to the drawing in detail, the transport pyrolysis chamber 
includes three separate zones or sections, a lower or input section 10 
which serves for combining and blending the particulate feed, an 
intermediate section 12 of reduced diameter and an upper or outlet section 
14. The lower section 10 includes a pair of inlet pipes 16 and 18. The 
upper section 14 includes an outlet pipe 20. 
The lower section 10 is constructed from an outer metal pipe 22 terminating 
in an upper flange 24. The inlet pipe 16 is an axially aligned outer metal 
pipe 26 terminating in a lower flange 28 for coupling the pyrolysis 
chamber to a feed of the particulate source of heat (not shown). A second 
input pipe section 30 forms an acute angle intersection with the inlet 
pipe section 26 and terminates in a coupling flange 32 for coupling the 
chamber to a source of solid organic feed particles (not shown). The inlet 
section 10 is normally constructed with an inner lining of refractory or 
other suitable heat resistant material, indicated generally at 34. The 
inner lining 34 is concentric with the pipe section forming the outer 
metal walls, the intermediate annular space being filled with a suitable 
high temperature insulating material, as indicated at 36. 
The intermediate section of reduced diameter and reduced cross-sectional 
area 12 similarly has an outer metal pipe 40 terminating at its lower end 
in a coupling flange 42 and at its upper end in a coupling flange 44. A 
reduced diameter passage is formed through the intermediate section by an 
inner metal tubular member formed by cylindrical section 46 from which 
extends on either side tapered metal frustoconical sections 48 and 50. The 
cylindrical section 46 and the two conical sections 48 and 50 are formed 
from suitable heat resistant material such as Inconel. The annular space 
between the outer metal pipe 40 and the inner venturi-type member is 
filled with a suitable high temperature refractory type insulating 
material. 
The upper section 14 similarly includes an outer metal pipe 52 having a 
lower coupling flange 54. The outer pipe 52 has an outwardly tapered 
section 56 and an upper expanded diameter section 58 to which an outlet 
pipe 60 is joined in a T-connection. The outlet pipe 60 terminates in an 
outer flange 62. An inner refractory liner 64 forms an elongated 
cylindrical chamber, the upper end of which joins the outlet pipe 60. The 
top of the chamber is provided with a removable access cap 66. The annular 
space between the outer metal wall and the inner refractory wall is filled 
with suitable insulation material 65. 
The lower section of the pyrolysis chamber above the inlet pipes is of 
preferably the same internal diameter as the chamber in the upper section 
14. This diameter is reduced by the conical sections 48 and 50 down to the 
reduced diameter of the section 46. The internal diameter of the section 
46 is preferably of the order of 0.6 to 0.7 times the internal diameter of 
the upper and lower sections of the pyrolysis chamber. Moreover, the 
intermediate section of the reduced diameter is positioned substantially 
closer to the inlet pipes than to the outlet pipe 60. Three sections form 
an initial blending zone, an intermediate zone for increasing particle 
velocity, and a final pyrolysis zone. All operate under turbulent flow 
conditions with Reynolds number being maximized in the intermediate zone. 
In operation, organic feed is admitted into the inlet pipe 18 and along the 
axis of the reactor. The organic feed is in the form of solid particles 
preferably of 8 mesh or less in size. The organic particles are mixed with 
sufficient product gas or other gas which is nondeleteriously reactive 
with the products of pyrolysis to fluidize the particles and move them 
upwardly into a pyrolysis chamber. The particulate source of heat, which 
may be the carbon containing solid residue of pyrolysis or "char" and/or 
an inorganic heat source formed from decarbonization of the carbon 
containing solid residue of pyrolysis or "ash" is admitted to the 
pyrolysis chamber through the inlet 16 at an angle to the feed of the 
solid waste. The weight ratio of inert particulate source of heat to the 
organic feed particles is typically in the range of 2:1 to 10:1 or more. 
The temperature of pyrolysis, while possibly limited by the softening 
point of the particulate source of heat, is typically in the range of 
about 600.degree. to 2200.degree. F, preferably about 800.degree. to 
about 1350.degree. F. The organic solid waste typically enters the 
pyrolysis chamber at a temperature of about 100.degree. F and the 
particulate source of heat enters at a temperature higher than the 
pyrolysis temperature. The inert particulate source of heat and organic 
waste converge in the lower chamber and are blended. Pyrolysis of the 
organic waste is initiated. To achieve thorough mixing to perfect required 
short residence time pyrolysis, they are accelerated through the 
intermediate constricted section. The Reynolds number for the fluid flow 
through the venturi section is substantially double that for the rest of 
the pyrolysis chamber, resulting in high agitation and, therefore, a much 
more thorough and intimate mixture of the very hot particulate source of 
heat and the particles of organic solid waste. The velocity of flow 
produces a Reynolds number of about 50,000 to about 500,000 or more in the 
lower and upper chambers and about 100,000 to about 1,000,000 or more in 
the restricted section, the flow rate being above the critical Reynolds 
number for laminar flow. As a result, the temperature of the organic feed 
particles is quickly raised in the pyrolysis chamber by heat transfer from 
the particulate source of heat to the temperature at which pyrolysis of 
the organic solid waste into gas, carbon containing solid residue of 
pyrolysis, and oil products takes place. The gas and oil products and 
solids exit at the outlet of the pyrolysis chamber. 
By providing the intermediate restricted section, heat transfer between the 
hot inert particles and the organic feed particles is greatly enhanced, 
permitting the overall length of the pyrolysis chamber to be substantially 
reduced as well as reducing the residence time of the particles in the 
pyrolysis chamber. For example, a pyrolysis chamber of 12 feet in length 
between the inlet and outlet may be operated with complete pyrolysis at 
total residence times of 0.2 second. Thus, a relatively compact high 
volume flash pyrolysis unit is provided which enables heat transfer 
between two solid constituents in extremely short times.