Note: Descriptions are shown in the official language in which they were submitted.
~08~1646
,,~
Background of the ~nvention
: The present invention is directed to the pyrolysis of
:: organic solid wastes from industrial and municipal sources.
. The disposal of wastes both from municipal and indus-
: trial sources~ such as trash, rubbish, garbage, animal wastes,
agricultural wastes, and waste of plastic processing opera-
tions is rapidly becoming of immense national concern. The
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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. Preveious 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 ma~ority 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 bac 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 may be sub~ect to a flash pyrolysis as an -
operation independent of recovery of the directly recyclable
inorganic fraction and any organic portion recovered as pulp.
Flash pyrolysis yields char~ pyrolytic oil and gases as
products.
:
,
SummarY of the Invention
According to the invention, a pressure seal is estab-
lished on one or both cross connections of apparatus for
carrying out an essentially closed loop pyrolysis process.
This prevents backflow of oxygen containing gas to the
pyrolysis side of the apparatus and/or valuable products of
- pyrolysis to the oxidizing burner side of the apparatus.
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1081646
The present invention therefore provides apparatus for pyrolyzing
organic solid waste comprising: (a) a transport pyrolysis reactor providing
a first inlet for receiving particulate organic solid waste and a second
inlet for receiving a particulate source of heat selected from the group con-
sisting of a carbon containing solid residue of pyrolysis, an inorganic heat
source formed by decarbonization of the carbon containing solid residue of
pyrolysis, and mixtures thereof adjacent one end of the transport pyrolysis
reactor and an outlet for the products of pyrolysis adjacent the opposed end
of said transport pyrolysis reactor; (b) means for passing particulate
organic solid waste into the first inlet of said transport pyrolysis reactor
and means for passing the particulate source of heat in a nondeleteriously
reactive transport gas into the second inlet of said transport pyrolysis
reactor for combination and passage with the particulate organic solid waste
through the transport pyrolysis reactor under turbulent flow conditions for
a time sufficient to pyrolyze the organic solid waste to yield the carbon
containing solid residue of pyrolysis, pyrolytic oils, and gases at a given
pressure at the second inlet of the transport pyrolysis reactor; (c) means
for separating the particulate source of heat and carbon containing solid
residue of pyrolysis from the pyrolytic oils and gases exiting the outlet of
the transport pyrolysis reactor; (d) a first collection vessel providing an
outlet at the base thereof for collection of the particulate source of heat
and carbon containing solid residue of pyrolysis; (e) means for depositing
the separatedparticulate source of heat and carbon containing solid residue
of pyrolysis in the first collection vessel; (f) a burner having an inlet for
receiving the carbon containing solid residue of pyrolysis and particulate
source of heat from the first collection vessel; (g) a first transport con-
duit connected from the outlet of the first collection vessel to the inlet
of the burner; (h) means for introducing a transport gas into the first
transport conduit to transport the separated particulate source of heat and
carbon containing solid residue of pyrolysis from the first collection vessel
to the burner; (i) means for passing the separated particulate source of heat
and carbon containing solid residue of pyrolysis through the burner, at a
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10~1646
given burner inlet pressure, in the presence of a gaseous source of oxygen
for a time sufficient to form the particulate source of heat by at least
partial decarbonization of the carbon containing solid residue of pyrolysis
for passage to the pyrolysis reactor; (j) a second collection vessel provid-
ing an outlet at the base thereof; (k) means for depositing at least a portion
of the formed particulate source of heat in the second collection vessel;
(1) a second transport conduit connected from the outlet of the second
collection vessel to the second inlet of the pyrolysis reactor; (m) means for
introducing the nondeleteriously reactive transport gas into the second
transport conduit to transport the partlculate source of heat from the second
collection vessel to the pyrolysis reactor; (n) first means for establishing
a higher pressure at the outlet of the first collection vessel than the given .
pressure at the inlet to the burner to prevent reverse flow through the con-
necting transport conduit; and (o) second means for establishing a higher
pressure at the outlet of the second collection vessel than the given pres-
sure at the second inlet of the pyrolysis reactor to prevent reverse flow
through the connecting transport conduit.
.
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108164~i
Specifically, particulate organic solid waste and a
fluidized particulate heat source are passed through a pyro
- lysis reactor at a given temperature under turbulent flow
conditions for a time sufficient to pyrolyze the organic
solid waste to char, pyrolytic oils, and gas. The inlet of
the pyrolysis reactor is at a given pressure. The particulate
heat source is separated from the pyrolytic oils and gas and
deposited in a first collection vessel. The separated parti-
culate heat source is transported in a fluidized state from
the first collection vessel to the char burner through which
it passes in the presence of oxygen and char for a time
sufficient to heat the particulate heat source above the given
temperature. The inlet of the char burner is at a given
pressure. The heated particulate heat source is deposited in
a second collection vessel from which it is transported to
the pyrolysis reactor. A higher pressure is established at
the outlet of one of the collection vessels than the given
pressure at the inlet to which it is connected to prevent
reverse flow to the one collection vessel. Reverse flow to
the other collection vessel is also prevented.
Preferably, reverse flow to the other collection
vessel is also prevented by establishing a higher pressure at
the outlet of the other collection vessel than the given pres-
; sure at the inlet to which it is connec~ed. The high pressure
at the outlet of each collection vessel is established by a
vertical standpipe extending downwardly from the corresponding
collection vessel such that the bottom of the standpipe de-
fines the outlet of the corresponding collection vessel. The
~ 1646
particles in the corresponding collection vessel are aerated
to a dense fluidized state. During transport to the cor-
responding inlet by a transport conduit, the particles are
further aerated into a substantially less dense fluidized
state. Each transport conduit comprises an angle riser having
a low end and a high end, an angle bend connecting the bottom
of the standpipe to the low end of the angle riser, and a
vertical riser having a bottom connected to the high end of
the angle riser, and a top connected to the corresponding
inlet, i.e., the inlet of the pyrolysis reactor or the inlet
of the char burner.
Other features of the invention are described below
in connection with the detailed description.
Brief Description of the Drawings
The features of a specific embodiment of the best
mode contemplated of carrying out the invention are illustrated
in the drawings, in which:
Figure 1 is a schematic diagram of apparatus for carry-
ing out a pyrolysis process in accordance with the principles
of the invention;
Figure 2 is a side elevation view of the cross connec-
tion from the ash surge hopper to the pyrolysis reactor shown in
Figure l;
Figure 3 is a side elevation view illustrating in more
detail the angle bend and angle riser shown in Figure 2; and
Figure 4 is a sectional view of the angle riser shown
in Figure 3, which is typical of the entire cross connection.
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1081646
Detailed Description of the Specific Embodiment
There is provided in accordance with this invention,
apparatus to carry out an essentially closed loop process
for the pyrolysis of the organic solid waste fraction of
municipal and industrial wastes.
As used herein, the term 'organic solid wastes" means
the predominately organic portion derived from as received
waste source, domestic and/or industrial in origin, after
gross separation into an inorganic constituent such as iron,
aluminum, glass and other values including paper pulp. Be-
cause of the several comminuting operations attendant to the
gross sepa~ation, there may appear in the organic solid
waste fraction some inorganic solid fines. In municipal
waste, the fines are predominately glass. The inorganic
fraction constituents, except for fly ash, is "ash" formed
from the char.
The organic constituents of the organic solid wastes
include cellulosic materials, plastic, rubber stock, and
animal waste~ Included in the meaning of '~cellulosic
materials" are paper, tree trimming and bark, sawdust, crop
waste~ vegetable and fruit processing waste~ and the like.
"Plastics" include discarded household plastics, as well as
the waste of industrial polymer forming and processing opera-
tions. "Rubber stock" includes waste tires. "Animal wastes"
include household discards~ slaughter house wastes, poultry
processing wastes, manure, and the like.
Resulting from a generally sundry mixture of waste
materials after gross separating substantially inorganic
.
.
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~081646
values, the organic solid waste may have, after drying to
the extent prepared for ~ransport to a pyrolysis reac~or,
the following typical analysis:
TABLE 1
Constituent% by Weight
;
Organics 92.29
Metals 0.38
Glass 1.69
Other Inorganics 2.02
Water 3.62
When the organic solid waste is pyrolyzed, there is
formed a mixture of char, pyrolytic oils, and gas. The gas
includes transport gas and gases resulting from pyrolysis. The
gas on a dry basis consists primarily of the oxides of carbon
and hydrogen
The char may, depending on the waste source, contain
from about 50 to about 70% ash, the balance being carbon.
Bulk density of the char is from about 5.5 lbs/cu. ft. to
12.5 lbs/cu. ft.
Ash, has, in contrast, a bulk density between about
55 lbs/cu. ft and 70 lbs/cu. ft. Its hard, glasslike nature
makes an ideal source which may be readily generated from
within the process itself. The ash has a fusion temperature
between about 1425F and about 1450F, and a particle and
skeletal density of about 150 lbs/cu. ft.
:`
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~081~46
The pyrolytic oils formed while varying in nature
depending upon the composition of the waste material pro-
cessed and pyrolysis conditions employed are at the same
time unique. They may be characterized as an oxygenated.
complex organic fluid, typically up to 40% and in some cases
up to 85% soluble in water, acids or base. Solubility in
polar organic solvents such as glycerol is limited and the
pyrolytic oils are relatively insoluble in non-polar organic
solvents, such as diesel oil, carbon tetrachloride, pentane,
decane, benzene, toluene, and hexane. The pyrolytic oil,
however, can be successively blended and mixed with various
#6 fuel oils. Combustion stability of the mixture is about
the same as #6 fuel oil alone.
A typical example of an elemental analysis of the
pyrolytic oil is that obtained from the pyrolysis of a waste
material containing about 70% cellulosics. The oil thus
obtained will contain from about 52% to about 60% carbon~
from about 6% to about 8% hydrogen, from about 1% to about 2%
nitrogen, and from about 29% to about 33% oxygen. The
empirical formula which best fits the pyrolytic oil analysis
is C4H802. Specific gravities are unusually high~ ranging
from about 1.1 to about 1.4.
By a l'non~eleteriously reactive" transport gas~ there
is meant a gas stream which is essentially lacking in free
oxygen. Although consitiuents may react under non-oxidizing
conditions with pyrolysis products to upgrade their value, to
be avoided are constituents which degrade pyrolysis products.
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~164~
With reference to Figurc 1, organic solid waste from which there
has been a gross separation of inorganics and which is comminuted to particles
having a maximum particle dimension less than 1 inch, preferably a particle
size less than 5 mesh, and more preferably less than 8 mesh, is dried and
stored in tank 10. The organic solid waste is conveyed at a desired rate by
screw conveyor 12 to transport line 14. The solid organic waste is transport-
ed through transport line 14 as a concentrated fluidized mass using a
transport gas, preferably product gas of the process to pyrolysis reactor 20.
The transport gas is introduced directly to line 14 and at several points
along its length through line 16 from a source of transport gas designated by
the encircled letters "TG". If the organic feed rate is in excess of that
required by the pyrolysis reactor 20, control valve 18 is closed and control
valve 22 is opened, enabling a portion of the solid organic waste to be divert-
ed by line 24, separated from its transport gas, which is introduced through
line 26 by cyclone 28, and returned to tank 10.
Simultaneous with the introduction of the organic solid waste into
pyrolysis reactor 20, a particulate heat source along with its transport gas
is also introduced thereto. The particulate heat source may be any material
capable of transferring heat to the organic solid waste to cause its pyrolysis
into gases, pyrolytic oils, and char. The preferred heat source is char, the
ash derived from the decarbonization of char, and mixtures thereof. Ash
derived from the decarbonization of char is a particularly preferred heat
source because it is relatively attrition free, and is of high bulk density, `
which minimizes the elevation required to achieve the pressure seal discussed
below.
; Pyrolysis reactor 20 is operated, depending upon the temperature and
; the nature of the particulate heat source, at a temperature from between about
600F and the introduction temperatures of the particulate heat source to the
; flash pyrrolysis reactor. Reactor temperature is essentially sustained by the
particulate heat source. Within this temperature range, pyrolysis occurs
primarily with liquification below about 1400F and by gasification at tempera-
tures above 1400F. Where char is the source of heat, temperatures will range
-- 8 --
lV81g~46
from about 600F to about 2000~F. Where ash in whole or in part is a source
of heat, the upper temperature limit is ascertained by the fusion temperature
of the ash which is between about 1425F and 1450F. Ash, the preferred
source of heat, requires, when used, an operating temperature between 600F
and 1400F. The preferred pyrolysis temperature is between about 900F and
1350F.
In pyrolysis reactor 20, heat transfer occurs primarily by solids
to solids, with some solids to gas to solids heat transfer occurring. In
general operation, organic solid waste feed temperature is approximately 100F,
and its transport gas from ambient up to about 500F. The preferred transport
gas for both the organic solid waste and the particulate heat source is the
gas resulting from the pyrolysis of the organic solid waste.
Residence time during pyrolysis is generally less than 10 seconds,
preferably from 0.1 to 2 seconds, and more preferably, from about 0.2 to 0.4
second. The weight ratio of the particulate heat source to organic solid waste
will vary depending upon temperature of the particulate heat source and the
temperature desired in the pyrolysis reactor 20. Generally about 2 to about
20, preferably from 4 to 6 pounds of the particulate heat source per pound of
the comminuted organic solid waste is fed to the pyrolysis reactor 20. To
achieve intimate mixing, turbulent flow conditions are required. Reynolds
flow index numbers, therefore, will exceed 2,000 with Reynolds numbers in ex-
cess of 50,000 frequently employed.
Products of the pyrolysis, including the particulate heat source,
leave reactor 20 via line 44 and enter product cyclone 46 where heavy particles
and particles of large diameter are separated. Particles settle through dip
leg 48 into the constricted area 58 of stripper hopper 60. Finer dense par-
ticles and char particles are separated by cyclone 62 and are fed to hopper 60
through dip leg 64. Each dip leg has on its end a flap valve to prevent back-
flow of fluidizing gas in hopper 60 from interrupting the operation of cyclones
46 and 62. Cyclones 46 and 62 are designed to operate at a high efficiency
to maximize separation of particles from the gas stream. Thus, cyclones 46
and 62 serve to separate the particulate heat source and the char produced by
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108164~
pyrolysis from the pyrolytic oils and gas.
The residual gas stream, which includes the condensible pyrolytic
oils and product gases, leaves by line 66 and enters fines separator cyclone
70, where fine char particles are recovered. The fine char particles descend
dip leg 72 into char bin 74 for recovery as product. Inert aeration gas at a
low temperature is introduced at the base of char hopper 74 to cool the char
and maintain the char in a free flowing semifluid state.
The residual gases, substantially free of fines, pass by line 76 to
quench venturi scrubber 78 where, by the introduction of a quench oil, the
pyrolytic oils are caused to condense from the gas stream and collect in
vessel 80. A second quench venturi scrubber 82 is used to remove residual
pyrolytic oil which collects in settler 84. After scrubbing the gas in
scrubber 86 and compression in compressor 87, residual condensates are collect-
ed in separator 88 to provide product gas for use in the process as transport
gas. Excess gas may be flared to the atmosphere.
The char and the particulate heat source collect in the lower,
narrow zone 58 of hopper 60 and are maintained at a predetermined level by the
rate of solids withdrawal through standpipe 92. The rate of such withdrawal
is controlled by setting slide valve 94, which is located at the bottom of
standpipe 92. Aeration gas, normally the product gas from a source designated
in Figure 1 by the encircled letters "AG", is introduced into the vertical
and angles side of zone 58 to maintain the solids in a dense fluidized state.
Aeration gas also serves to remove or strip oils which cling to the surface
of the particles. The stripped oils are exhausted back to the product gas loop
via bypass line 41. Normally, the level of the dense fluidized particles co-
incides with the top of narrow zone 58. Thus, particles which are entrained
by the aeration gas, except extreme fines, lose velocity in the upper expanded
section when they rise above the dense particle level and fall back below the
level of the dense fluidized particles in zone 58. The aeration gas also cools
the particles in hopper 60.
Particles in zone 58 are mixtures of the particulate heat source and
char. Where the particulate heat source is char alone, the content is essen-
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.j ,, ~ .
~()8~646
tially particulate char. Standpipe 92 extends into zone 58 of hopper 60 and
thus serves to selectively couple the particles of intermediate weight to
standpipe 92. Aeration gas is also introduced into standpipe 92 at distribut-
ed points along its length.
In the instance where char alone is present, the larger char par-
ticles tend to gravitate toward the base and the finer toward the top, with
particles representing a cross section of the particles in zone 58 being at
the middle. Thus, the particles admitted to standpipe 92 tend to represent
the average particle size of the particles in zone 58.
Where zone 58 contains product char and a different high density heat
source such as ash, the heavier ash particles tend to gravitate toward the
bottom and the lighter char particles toward the top. By mixing with the
aeration gas, the particles at the point of sampling, 93, represent composition-
wise, the composition of the char and ash entering hopper 60.
If the extension of standpipe 92 into hopper 60 were eliminated, the
feed to standpipe 92 would tend to contain only large particles if char alone
is present, or a predominance of the dense particles if char and a different
high density heat source are used in the pyrolysis operation. The large and/or
dense particles at the bottom of zone 58 are broken up by the aeration gas
and eventually rise upward. The point of sampling 93 is, as shown, screened
to reject clinkers.
Hopper 60 and standpipe 92 serve as a collection vessel for the mix-
ture of particulate heat source and char. The bottom of standpipe 92 serves
as the outlet of the collection vessel. The column of dense fluidized par-
ticles in standpipe 92 and zone 58 lying above it produce a high potential
pressure head that establishes a higher pressure at the bottom of standpipe
92 than the pressure at the inlet of char burner 100. The pressure at the in-
let of valve 94 is preferably about 1.5 to 3 times the pressure at the inlet of
char burner 100 to account for line losses and variations in burner inlet
pressure. This high potential pressure head provides the major driving force
; for the transport of the mixture of particulate heat source and char to char
burner 100, and provides a pressure seal to prevent reverse or backflow from
108164~;
char burner lO0.
Angle bend 95 connects the bottom of standpipe 92 to the low end
of angle riser 96. The bottom of vertical riser 98 is connected to the high
end of angle riser 96, and the top of vertical riser 98 is connected to the
inlet of char burner lO0. Angle riser 96 and vertical riser 98 serve as a
particle transport conduit through which the particles at the bottom of stand-
pipe 92 are transported by a transport gas. The transport gas is introduced
in part by a plurality of nozzles 97 distributed along angle riser 96 and at
angle bend 95. Nozzles 97 are fed by gas line 99. Nozzles 97 are oriented
to project gas along the direction of flow in angle riser 96 to lift the trans-
ported particles to vertical riser 98. At this point, substantially more
transport gas is introduced by nozzle 101, which provides a final suction-
transport force to lift the particles under high gas flow rates to char burner .
100. The transport gas introduced into angle riser 96 lifts the particles
at the bottom of standpipe 92 up to the bottom of vertical riser 98 and re-
duces the density somewhat of the fluidized particles. The transport gas
introduced by nozzle 101 lifts the particles up to char burner 100 and sub-
stantially reduces the density of the fluidized particles. As a result, the
potential pressure head at the bottom of vertical riser 98 is substantially
less than that at the bottom of standpipe 92. Additional transport gas is
introduced at distributed points along the length of vertical riser 98. The
described cross connection from stripper hopper 60 to char burner 100 thus
provides a pressure seal to prevent backflow of oxygen containing gas to the
pyrolysis side of the apparatus.
If zone 58 contains char and a different high density heat source,
i.e., ash, and too many fines are present in zone 58, too much ash will be
present at point of sampling 93 and the top of zone 58 will be rich in char.
Thus, the described cross connection will not supply enowgh char to char
burner 100 to achieve the desired particle temperature therein. To provide
for this contingency, a screened sampling point 85 located near the top of
zone 58 is connected by a downwardly sloping conduit 89 and an upwardly slop-
-~ ing conduit 90 to vertical riser 98 at a point near the top end of angle riser
- 12 -
1081646
96. A normally closed valve 91 is disposed between conduit 89 and conduit 90.
When too many fines are present in zone 58, valve 91 is opened and char-rich
fluidized particles are supplied to char burner 100 through conduits 89 and 90,
to supplement the particles supplied through standpipe 92.
In char burner 100, the particles used for pyrolysis are raised to
the temperature requisite for introduction to the pyrolysis reactor by par-
tial or total combustion. In the instance where char is the source of heat, a
portion of the char is combusted in the presence of the air introduced as the
transport gas through nozzle 101 and along the length of vertical riser 98
and/or by combustion air introduced by line 102 to char burner 100. The air is
preheated in exchanger 104 by the flue gas from char burner 100. Control may
be exercised over the combustion conditions in char burner 100 by limiting the
amount of air introduced. The source of air is designated in Figure 1 by the
encircled letters "AIR".
Where ash is to be employed as the source of heat, char burner 100
must be maintained at a temperature below the fusion temperature of the ash
formed as a consequence of oxidative decarbonization of char. To form ash,
combustion in char burner 100 is from about 80% to 100% complete, and suffi-
cient air is introduced to achieve this end. To control combustion tempera-
ture, water is introduced along with air to convert the water into mist, which
acts as a uniform quench to absorb the heat of combustion through vaporization.
In the instance of the use of ash as the heat source, char burner 100 is main-
tained at a temperature between 1350F and 1400F. Water requirements from the
water source designated in Figure 1 by the encircled letters "H20", are main-
tained and controlled by valve 103.
- The products from char burner 100 leave by line 106 and pass through
burner cyclones 108 and 110. Both cyclones are low efficiency cyclones to con-
trol the size of the particles separated from the gas streams and eliminate
from them, fines. Cyclone 108 serves primarily for the separation of coarse
particles and cyclone 110 for particles of intermediate size. The collected
particles are transferred by dip legs 112 and 114 to insulated surge hopper 116.
As illustrated in Figure 1, the particles in surge hopper 116 and
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181~1646
standpipe 40 are maintained in a dense fluidized state by the flow of
aeration gas therethrough. In the event that ash is the source of heat and
combustion in the burner is incomplete, air is introduced as part of the
aeration gas to complete combustion with controlled introduction of a water
mist as a quench.
The rate of solids withdrawal through standpipe 40 is controlled
by setting slide valve 38, which is located at the bottom of standpipe 40.
Hopper 116 and standpipe 40 serve as a collection vessel for the particulate
heat source. The bottom of standpipe 40 serves as the outlet of the collec-
tion vessel. The column of dense fluidized particles in standpipe 40 and
hopper 116 lying above it produce a high potential pressure head that
establishes a higher pressure at the bottom of standpipe 40 than the pressure
at the inlet of pyrolysis reactor 20. The pressure at the inlet of valve 38
is preferably about 2 to 3 times the pressure at the inlet of pyrolysis
; reactor 20 to account for line losses and reactor inlet pressure variations.
This high potential pressure head provides the major driving force for the
transport of the particulate heat source to pyrolysis reactor 20 and provides
a pressure seal to prevent reverse or backflow from pyrolysis burner 20.
Angle bend 36 connects the bottom of standpipe 40 to the low end of
angle riser 42. The bottom of vertical riser 30 is connected to the high
end of angle riser 42J and the top of vertical riser 30 is connected to the
inlet of pyrolysis reactor 20. Angle riser 42 and vertical riser 30 serve
as a particle transport conduit through which the particles at the bottom of
standpipe 40 are transported by a transport gas. The transport gas is intro-
duced in part by a plurality of nozzles 32 distributed along angle riser 42
and at angle bend 36. Nozzles 32 are fed by a gas line 34. Nozzles 32 are
oriented to project gas along the direction of flow in angle riser 42 to lift
the transported particles to vertical riser 30. At this pointl substantially
more transport gas is introduced by nozzle 35, which provides a final suction-
transport force to lift the particles under high gas flow rates to pyrolysis
reactor 20. The transport gas introduced into angle riser 42 lifts the par-
ticles at the bottom of standpipe 40 up to the bottom of vertical riser 30,
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~81646
and reduces the density somewhat of the fluidized particles. The transport
gas introduced by nozzle 35 lifts the particles up to pyrolysis reactor 20
and substantially reduces the density of the fluidized particles. As a result,
the potential pressure head at the bottom of vertical riser 30 is substantial-
ly less than at the bottom of standpipe 40. Additional transport gas is
introduced at distributed points along the length of vertical riser 30. The
described cross connection from surge hopper 116 to pyrolysis reactor 20 thus
provides a pressure seal to prevent backflow of valuable product gas and oil
to the oxidizing burner side of the apparatus.
Since pyrolysis occurs at some temperature intermediate of the tem-
perature of the particulate heat source introduced into pyrolysis reactor 20
and the temperature of the feed, for minimum utilization of the particulate
heat source, the transport gas for the particulate heat source should approach
its temperature. While air, if required, may be introduced to standpipe 40
as a fluidizing gas, the gas present beyond slide valve 38 is the non-
deleterious carrier gas.
For good transport, the particles in surge hopper 116, are in a
particle size range between about 10 to about 2000 microns, preferably between
about 20 to about 1000 microns. To maintain the particles in surge hopper
116 within the desired particle size range, requires some periodic manipula-
tion of the particles in surge hopper 116. In the instance where the par-
ticles become too fine, the level of particles in surge hopper 116 is raised
by reducing the rate of withdrawal through line 118. This alone or in
combination with the introduction of a small amount of transport gas into the
hopper of cyclone 110 serves to disrupt the operation of cyclones 108 and 110
to reduce their efficiency still further. This separates fewer fines from
the gas streams and increases the Gverall average particle size in surge
hopper 116.
If, in contrast, the particlesbecometoo coarse, particles are with-
drawn through line 118 at a rate greater than production for passage to
elutriator quench drum 120. By the flow of an elutriating gas, the fines are
returned by line 122 to hopper 116 to decrease the overall average particle
.
', . ~ ` '
:- . :
~08164~;
size in hopper 116.
Surge hopper 116 is provided with bypass line 124 to remove fines
entrained by its fluidizing gas.
The product not required for return to pyrolysis reactor 20 is pass-
ed from elutriator quench drum 120 to product trim cooler 123 for withdrawal
of char or ash.
~ The fines from char burner 100, along with any fines removed with
- exhaust gas from hopper 116 by line 124, pass from cyclone 110 through velo-
city reduction zone 128 to a cyclone 129, where some of the fines are removed.
The remainder of the fines pass through line 126 to velocity reduction zone
130. After removal of settled fines in velocity reduction zone 130, the flue
gas is used in heat exchanger 104 prior to passage to a suitable stack.
The vertical arrangement of standpipe 40, angle riser 42, vertical
riser 30, pyrolysis reactor 20, cyclones 46 and 62, stripper hopper 60,
standpipe 92, angle riser 96, vertical riser 98, char burner 100, cyclones
108 and 110, and ash surge hopper 116 are important. A vertical scale, de-
signated 133 in Figure 1, illustrates the vertical arrangement of the compon-
ents over a height of approximately 60 feet. Basically, cyclones 46, 62, 108,
and 110, pyrolysis reactor 20, and char burner 100 are all arranged at about
the same elevation near the top of the facility; hoppers 60 and 116 are
located at about the same elevation directly below cyclones 46 and 62 and
cyclones 108 and 110, respectively, the bottoms of standpipes 40 and 92 are
located at about the same elevation; the bottoms of vertical risers 30 and 98
are located at about the same elevation; the inlets of pyrolysis reactor 20
and char burner 100 are substantially higher in elevation than the bottoms of
standpipes 40 and 92, respectively.
For start up, there is employed reservoir 132 which is used to
transport particulate materials to hopper 116 for initiation of the pyrolysis
process. Any inert material such as sand or glass, may be heated and used
for initial start up. It is, however, gradually supplanted by the char or
ash formed in the pyrolysis process.
~"
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.
~081~46
Reference is made to Figures 2, 3, and 4 for a detailed descrip-
tion of the cross connection from surge hopper 116 to pyrolysis reactor 20.
Standpipe 40 comprises pipe sections 40a, 40b, and 40c. Nozzles 41a, 41b,
and 41c extend through the side wall of pipe sections 40a, 40b, and 40c res-
pectively, to provide aeration gas to standpipe 40. Slide valve 48 connects
the bottom of standpipe 40 at pipe section 40c to angle bend 36. Pressure
instrumentation taps 45 and 47 extend through the side wall of section 40c and
angle bend 36, respectively, on opposite sides of slide valve 38. The inputs
of a differential pressure sensor 51 are connected to taps 45 and 47, respec-
tively. When the pressure difference across slide valve 38 drops below a
predetermined minimum value, indicating that reverse flow is imminent, dif-
ferential pressure sensor 51 produces a signal that shuts off slide valve 38.
Angle riser 42 comprises a pipe section 53 and a quarter elbow 55.
As depicted by cross-sectional view of section 53 in Figure 3, the entire
cross connection including angle bend 36, section 53, and elbow 55, has an
annular outer layer of heat insulation 57 and an annular inner layer of heat
insulation 59, which is composed of an abrasion resistive material. In one
embodiment, the inside diameter of the cross connection is 15 inches, the in-
side diameter of layer 57 is 10 inches, and the inside diameter of layer 59 is
6 inches. Nozzles 32a, 32b, and 32c extend through the wall of angle bend 36
to its interior. Nozzles 32d, 32e, 32f, and 32g extend through the wall of
section 53 at uniformly distributed points along its length to its interior.
Nozzles 32h and 32i extend through the side wall of elbow 55 to its interior.
As illustrated in Figure 3, all of these nozzles are oriented to inject gas
into the interior of the cross connection in the desired direction of particle
; transportation and their outlets are located along the edge of the interior of
the cross connection so as to be out of the gas stream. The gas ejected from
nozzles 32a through 32i tends to draw the particles entering angle bend 36
into section 53 and to lift such particles through section 53 and elbow 55 to
vertical riser 30. Nozzle 35 extends through elbow 55 toward the bottom of
vertical riser 30; the gas ejected therefrom carries particles upwardly to
pyrolysis reactor 20. A temperature tap 63 is employed to monitor the tempera-
- 17 -
108~b~46
ture in elbow 55.
Vertical riser 30 comprises pipe sections 30a, 30b, 30c, 30d, and
30e. Nozzles 31a, 31b, 31c, 31d, and 31e extend through the side wall of pipe
sections 30a, 30b, 30c, 30d, and 30e, respectively, to provide transport gas
to vertical riser 30. Pressure instrumentation taps 27 and 29 extend through
the side wall of sections 30a and 30c, respectively.
The cross connection from stripper hopper 60 to char burner 100 is
identical to the cross connection described above in connection with Figures
2, 3, and 4, except that the cross connection need not be insulated and that
standpipe 92 and vertical riser 98 are slightly shorter than standpipe 40
and vertical riser 30, respectively.
The use of the double closed loop apparatus of this invention
eliminates the need for the use of rotary lock valve and the like through the
standpipes and transport conduits used to cross connect the two sides of the
system. While rotary lock valves can be used for hopper 60, no practical
' valve exists to enable the feed of the high temperature particulate feed
contained in surge hopper 116 on a continuous basis. Because the standpipe
pressures are a function of particle density, the preferred particulate
source of heat is the high density ash formed by decarbonization of char.
While nowise limiting, the following example is illustrative of
the presently preferred practice of the invention.
EXAMPLE
Organic solid waste resulting from the treatment of municapal solid
waste to remove the inorganic constituents, is dried and comminuted to a
particle size less than 8 mesh. The organic solid waste having the composition
shown in Table 2 is fed at a rate of 9491.4 pounds per hour to a pyrolysis
reactor using as the carrier gas a product gas of the composition shown in
Table 3.
:
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. .
~0~1646
TABLE 2
Component Wei~ht %
Organic 92.29
Metals 0.38
Glass 1.69
Inorganics 1.40
Other Solids 0.62
Water 3.62
TABLE 3
Carrier Gas
Composition Volume
_.
H2S 0.31
N2 0.86
2 32.42
CO 31.13
H2 10.54
CH4 5.13
C2H4 2.56
C2H6 0.88
C3 0.88
H20 15.28
Total 100.0
Av. M.W. 28.43
The carrier gas has a temperature of 500F, and the organic solid waste to ;~ ,
carrier gas weight ratio is 2Ø The nominal solids temperature is 100F.
Inlet pressure is 13 psig.
Simultaneously, 49,831 pounds per hour of an ash formed from de-
carbonization of char is transported along by about 480 pounds per hour of
the carrier gas employed to the pyrolysis reactor. Ash temperature is about
1350F. Approximate particle density is as follows: 60 lbs/cu. ft. in surge -
hopper 116; 65 lbs/cu. ft. in standpipe 40; lbs/cu. ft. in angle riser 42; and
15 lbs/cu. ft. in vertical riser 30. Approximate static pressure is as
- 19 -
1081~;~6
follows: 23 psig at the inlet of slide yalve 38; 21 psig at the bottom of
standpipe 40; 17 psig at the bottom of vertical riser 30; and 14 psig at the
inlet of pyrolysis reactor 20. Nominal operating pressure of pyrolysis reactor
20 is 10.5 psig. Approximate aeration gas flow rate is as follows: 2 scfm
into standpipe 40; 46 scfm into angle riser 42 through nozzles 32; 51 scfm
into the bottom of vertical riser 30 through nozzle 35; and 5 scfm along the
length of vertical riser 30.
The average temperature in pyrolysis reactor 20 is 950F. Average
residence time of the organic solid waste and ash is 0.6 second.
After pyrolysis, the discharge composition from pyrolysis reactor
20 is 12,883.6 pounds per hour of gas, including 3,659 pounds per hour of
water, 1,829.5 pounds of char, and the total ash fed to the pyrolysis reactor.
The gas effluent is passed to a first product cyclone which separates 51,120
pounds per hour of solids from the gas stream and a second cyclone which
separates 269 pounds per hour of solids from the gas stream. The balance of
the gas stream advances to fine cyclone which separates 207 pounds per hour of
essentially fine char, as product from the gas stream. After quench separation
of pyrolytic oil, the residual gas stream at a rate of 13,419 pounds per hour,
is made available as a heating gas and gas for the process. The excess is
flared to the atmosphere. The composition of the pyrolytic oil and char is
shown in Table 4.
TABLE 4
DRY CHAR AND DRY PYROLYTIC PRODUCT COMPOSITIONS ~Wt. %)
Char Oil
Carbon 48.8 57.0
Hydrogen 3.3 7.7
Nitrogen 1.1 1.1
Sulfur 0.2 0.2
Chlorine 0.3 0.2
Ash 33.0 0.2
Oxygen 13.3 33.6
- 20 -
~081646
The physical properties and particle size distribution of the
ash and char fed to the product cyclones is shown in Table 5.
TABLE 5
.
Ash ~irgin Char
Composition, wt. % 96.5 3.5
Particle density, lbs/ft3 150.0 112.0
Skeletal density, lbs/ft3 150.0 150.0
Se~tled bulk density, lbs/ft 58.0 12.0
Size Distribution, Wt. %
0 ~ 10 microns 1.2 34.0
10 ~ 20 7.8 24.0
20 ~ 40 13.0 19.0
40 ~ 80 16.0 10.0
80 ~ 12Q 18.0 4.0
120 ~ 160 13.0 2.0
160 ~ 200 10.0 1.5
200 ~ 400 15.0 2.5
400 ~ 600 2.5 1.2
600 ~ 1000 2.0 1.1
1000 ~ 2000 1.5 0.7
2000
Of the particles 99.96% are received as an ash char mixture, and the balance
as fine char product.
Of the mixture of ash and char collected in the stripper hopper 60,
solids are removed at a rate of 51,388 pounds per hour, and fed to char burner
100. Approximate particle density is as follows: 50 lbs/cu. ft. in zone 58
; of stripper hopper 60; 55 lbs/cu. ft. in standpipe 92; 50 lbs/cu. ft. in
angle riser 96; and 16 lbs/cu. ft. in vertical riser 98. Nominal operating
pressure of char burner 100 is 9.3 psig. Approximate static pressure is as
follows: 22 psig at the inlet of valve 94; 18 psig at the bottom of standpipe
92; 15 psig at the bottom of vertical riser 98; and 11 psig at the inlet of
char burner 100. Approximate aeration gas flow rate is as follows: 2 scfm
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. - , ,
10~1646
into standpipe 92; 59 scfm into angle riscr 96 through nozzles 97; 53 scfm
into the bottom of vertical riser 98 through nozzle 101; and 4 scfm along
the length of ~ertical riser 98.
Decarbonization of the char by oxidation in char burner 100 is at
an average burner temperature of 1350F. Char is supplied in excess of that
required to achieve total decarbonization in char burner 100. To maintain
burner temperature, water is fed as a fog to burner 100 at a rate of 2904
lbs/hr. The resultant ash and gases are passed to a first burner cyclone
which separate ash at the rate of 49,914 pounds per hour and then to a second
burner cyclone which receives ash at the rate of 306 pounds per hour. The
ash collects in hopper 116 and is maintained at the ash particle size shown
in Table 5. Residual gas stream containing 120 pounds per hour of fines is
passed to a fines accumulator. The ash collected in ash storage hopper is
withdrawn as product net recovery rate of 84 pounds per hour. The flue gas
from the char burner is employed to preheat the air required for combustion.
In this instance, the air is heated to a temperature of 650F by indirect
heat exchange with flue gas following which the flue gas is flared to the
atmosphere. In the operation, nominal residence time in the pyrolytic reactor
is 0.3 second, and in char burner 0.6 second. Average residence time of
solids in ash stripper is 3 minutes, and the ash surge hopper 5.5 minutes~
