Note: Descriptions are shown in the official language in which they were submitted.
120~2~i
BACKGROUND OF THE lNVENTION
This invention relates to the partial oxidation
of a liquid hydrocarbon fuel to produce synthesis gas.
More specifically, it relates to a process for
simultaneously producing two clean product streams of
synthesis gas, one gas stream with a high and the other gas
stream with a low, ~20/dry yas mole ratio by the partial
oxidation of heavy hydrocarbon feedstocks containing high
metal concentrations.
When a heavy liquid hydrocarbon fuel containing
high metal concentrations such as vacuum resid is reacted
by partial oxidation, entrained in the hot, raw gas stream
is particulate carbon and ash, i.e., nickel, vanadium, and
iron compounds. After the raw gas stream is cleaned free
from particulate matter, it is economically desirable to
dispose of the particulate carbon in the gas generator.
However, recent commercial experience in gasifying heavy
feed stocks containing high metal concentrations with 100%
soot recycle has shown that the convection type gas coolers
in the system may be then subject to shutdown because of
fouling. Deposits may plug the gas cooler tube inlets or
may collect downstream in the low-temperature sections of
the gas cooler tubes. These problems and others are now
avoided by the subject invention.
The hot raw effluent gas stream from the reaction
zone of a partial oxidation gas generator may comprise
principally H2, C0, C02, and H20 together with other
gaseous constituents, and minor amounts of entrained
particulate matter, i.e., particulate carbon and ash~ The
1~3~Z~S
hot, raw effluent gas must be cooled and cleaned to produce syn-
thesis gas or fuel gas. Synthesis gas is important commercially
as a source of feed gas for the synthesis of hydrocarbons or
oxygen containing organic compounds, or for producing hydrogen
or ammonia.
Entrained particulate carbon and ash may be removed
from the raw effluent gas by quenching and scrubbing with water
such as described in coassigned U.S. Patent 3,232,728. Cleaning
the effluent gas by scrubbing with an oil-carbon slurry is des-
cribed in coassigned U.S. Patent 3,639,261. Recovery of the
soot~ from carbon-water dispersions in a carbon-recovery faci-
lity is described in coassigned U.S. Patent Numbers 2,999,741;
2,992,906; 3,044,179; and 4,134,740. Typical decanting proce-
dures are described in coassigned U.S. Patent Numbers 3,980~592
and 4,014,786.
i~
2~35
According to one aspect of the present invention there
is provided a partial oxidation process comprising:
(1) reacting a reactant fuel feedstream comprising
a heavy hydrocarbon fuel feedstock containing high metal concent-
rations in admixture with a liquid dispersion compri.sing soot
in a liquid carrier with a free-oxygen containing gas in the
presence of a temperature moderator at an autogenous temperature
in the range of about 1700 to 3500F. and a pressure in the
range of about 5 to 300 atmospheres in the reaction zone of a
first free-flow noncatalytic partial oxidation gas generator
to produce a hot, raw stream of synthesis gas comprising H2, C0,
C02, particulate carbon, ash, and at least one material from the
group H20, CH4, H2S, COS, H2 and Ar;
(2) quench cooling and scrubbing with water at least
a portion of the hot, raw synthesis gas stream from (1), and
separating a partially cleaned synthesis gas stream from a
stream of liquid dispersion comprising particulate carbon, water r
and ash;
(3) simultaneously with (1) reacting a heavy hydrocarbon
fuel feedstock containing high metal concentrations with a free-
oxygen containing gas in the presence of a temperature moderator
at an autogenous temperature in the range of about 1700F to
35000F and a pressure in the range of about 5 to 300 atmospheres
in the reaction zone of a second free-flow noncatalytic partial
oxidation gas generator to produce a hot, raw stream of synthesis
gas comprising H2, C0, C02, paxticulate carbon, ash, and at least
one material from the group H20, CH4, H2S, COS, H2 and ~r;
(4) splitting the hot, raw synthesis gas stream from
(3) into first and second hot-split synthesis gas streams;
(5) cooling in a convection-type gas cooler all of the
first hot, split gas stream from (4), scrubbing the partially
z~s
cooled gas stream with water, and separating a clean product
stream of synthesis gas with a low H20/dry gas mole ratio from
a stream of liquid dispersion of particulate carbon, water, and
ash;
(6) quench cooling and scrubbing with water all of the
second hot, split gas stream from (4), and separating a partially
cleaned synthesis gas stream from a stream of liquid dispersion
comprising particulate carbon, water, and ash;
(7) mixing together the partially cleaned synthesis
gas streams from (2) and (6), scrubbing the combined streams
with water, and separating a clean product stream of synthesis
gas with a high H20/dry gas mole ratio from a stream of liquid
dispersion comprising particulate carbon r water r and ash;
(8) combining the streams of liquid dispersion com
prising particulate carbonr water, and ash from (2) r (5), (6),
and (7); and separating in a soot-recovery zone separate streams
of clarified water, ash, and a liquid dispersion comprising soot
in a liquid carrier; and
(9) mixing al.l of the liquid dispersion comprising
soot in a liquid carrier from (8) with fresh heavy hydrocarbon
fuel feedstock containing high metal concentrations, and intro-
ducing said mixture into the first partial oxidation gas genera-
tor in (1) as said reactant fuel feedstream.
~ cc~r~ing*o another aspect of the present invention
there is provided a system for sumultaneously producing two
clean product streams of synthesis gas having high and low
H20/dry gas mole ratios, respectively, comprising: at least one
free-flow partial oxidation gas generator with a refractory
lined reaction zone from which all of the hot raw effluent gas
is discharged into a quench tank containing water for quench
cooling and scrubbing, at least one free~-flow partial oxidation
i~ - 3a -
~z~Z~315
gas generator with a refractory lined reaction zone and a gas-
diversion means for splitting the hot raw effluent gas stream
into two split streams, and a convection-type gas cooler connected
to said gas diversion means for cooling one split stream of the
hot raw effluent gas stream, a gas scrubber and gas-liquid sepa-
rating means for receiving partially cooled synthesis gas streams
from said convection-type gas cooler and providing a clean
product stream of synthesis gas with a low H20/dry gas mole ratio;
and, flow control means in the lines for controlling the intro-
duction of all of the hot raw synthesis gas produced by one gasgenerator into its associated quench tank, and the introduction
of one of said split, hot raw synthesis gas streams produced by
the other gas generator into its associated quench tank, while
simultaneously introducing the remaining split hot raw synthesis
gas stream into the gas cooler; a gas scrubber and gas-liquid
separating means for receiving all of the partially cleaned
quenched streams of synthesis gas from the quench tanks in each
train and providing a clean product stream of synthesis gas with
a high H20/c1ry gas mole ratio, and a separate stream of liquid
dispersion of particulate carbon, water, and ash; a soot-recovery
facility for receiving all of the li~uid dispersion of particulate
carbon, water and ash from the quench tanks and gas scrubber and
gas-liquid separation means in both trains and providing
separate streams of ash, clarified water, and liquid dispersion
of soot; conduit means connected to at least one gas generator
whose hot raw synthesis gas stream is totally quenched for
introducing a reactant fuel feedstream comprising a mixture of
heavy hydrocarbon fuel feedstock containing high concentrations
of metal compounds in admixture with the liquid dispersion of
soot, a free-oxygen containing gas, and a temperature moderator;
and conduit means connected to the remaini.ng gas generating means
for simultaneously introducing a reactant fuel feedstream
- 3b -
2~5
comprisin~ a mixture of heavy hydrocarbon fuel feedstock con-
taining high concentrations of metal compounds, a free-oxygen
containing gas, and a temperature moderator.
SUMMARY
In accordance with the invention, the feedstock to a
partial oxidation process for the simultaneous continuous pro-
duction of two streams of cleaned synthesis gas having high and
low H20/dry gas mole ratios respectively may comprise a heavy
hydrocarbon fuel containing high metal concentrations as well as
all of the soot rich in metal valves recovered in the process.
Two free-flow noncatalytic refractory lined partial
o~idation gas generators are used. All of the hot raw synthesis
gas produced in the first gas genera~or is quench cooled in
water in a quench tank; and, simultaneously, all of the hot raw
synthesis gas produced in the second gas generator is split into
two separate hot, raw gas streams. One of said split gas
streams is quench cooled in water in a quench tank. Simultane-
ously, the other split gas stream is cooled in a convection-
type gas cooler by indirect heat exchange with boiler feed water,
without the tubes in the gas cooler plugging o~^ fouling. The
two ~uench cooled gas streams are combined and scrubbed free
from particulate matter, i.e., particulate carbon and ash with
water to produce a clean product stream of synthesis gas having
a high H20/dry gas mole ratio. Simultaneously, the stream of
synthesis gas leaving the gas coole~ is separately scrubbed free
from particulate matter to produce a clean product stream of
synthesis gas having a low H20/dry gas mole ratio. The streams
of carbon-water-ash dispersion from all of the quench tanks and
gas scrubbers is processed in a soot-recovery facility to
- 3c -
1~2Q~Z8~
separate clarified water, ash, and to produce a liquid
dispersion of soot in water or in a liquid hydrocarbon
carrier. All of this dispersion is then introduced into
the first gas generator as a portion of the liquid
hydrocarbon fuel feed. Fouling and plugging of the tubes
of a convection-type gas cooler associated with the second
gas generator is prevented even though there is total
carbon recycle in the process by: (1) lowering the fraction
of ash in the gas stream going to the gas cooler due to
split flow, and (2) decreasing the total metals in the feed
tv the second gas generator by eliminating the metals
normally recycled in the soot recycle.
BRIEF DESCRIPTION OF T~IE DR~WING
The invention will be further understood by
reference to the accompanying drawing. The dra~wing is a
schematic representation of a preferred embodim,ent of the
process.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
.
A more complete understanding of the invention
may be had by reference to the accompanying drawing which
illustrates one embodiment of the invention in which
conventional partial oxidation gas generators 1 and 2 are
simultaneously and continuously operated.
Synthesis gas generator 1 is fed with a fuel
mixture from line 3 which comprises heavy liquid
hydrocaxbon fuel containing high concentrations of metal
compounds from line 4 and a liquid dispersion of soot
containing metals in a liquid carrier from line 5 by way of
a conventional soot reco~ery facility 6 as previously
~Z0~28S
described. Actually, 'che heavy :Liquid hydrocarbon fuel in
line 4 is pumped by means of pump 7 through line 8, heater
9 (optional), and lines lO and 11 into mixer 14 where it is
mixed with the liquid dispersion of soot from line 5. Part
of the hydrocarbon fuel feedstock in line lO is preferably
sent to soot-recovery facility 6 by way of line 56, valve
57, and line 58 to provide the bulk of the liquid carrier
for the soot in line 5. The fuel mixture in line 20 is
mixed in line 3 with a temperature moderator such as steam
from line 99.
The mixture of fuel and steam in line 3 is
introduced into the free-flow noncatalytic reaction zone
15, lined with thermal insulating refractory 16, of gas
generator 1 by way of one passage in burner 17 located in
the top of gas generator 1. At the same time, a stream of
free-oxygen containing gas from line 18 is passed through
line 19 and is introduced into reaction zone 15 of gas
generator 1 by way of another passage in burner 17. The
autogenous partial oxidation of the fuel mixture then takes
place in the reaction zone of gas generator 1 to produce a
hot, raw synthesis gas stream containing unreacted
entrained particulate carbon and ash. During normal
operation, all of the hot raw synthesis gas stream is
quench cooled and scrubbed with water in a quench tank
located below the reaction zone. Thus, in the preferred
embodiment, with flow control means 22 closed in refractory
lined transfer line 23, or alternatively flow control means
valve 39 closed, all of the raw synthesis gas leaving
reaction zone 15 is passed down through thermal refractory
4~85
lined gas dive.rsion chamber 24, refractory lined passage 12, dip-
tube 25 and into quench water 26 contained in the bottom of a
conventional-type quench tank 27 located below reaction zone 15.
Flow control means 22 is a blank flange plate or valve located
in the line upstream or downstream from gas cooler 29 for con-
trolling the flow rate, or starting or stopping t:he passage of
the split, hot, raw synthesis gas stream therethrough.
The partially cleaned quench cooled stream of syn-
thesis gas with most of the particulate carbon and ash removed
leaves quench tank 27 by way of line 45 and is mixed with a
second stream of partially cleaned quench cooled stream of syn-
thesis gas from line 55, to be further described. The mixture
of gases is passed through line 46, and into venturi scrubber
4~ where it is scrubbed free of any remaining entrained particu-
l.ate carbon and ash with water from line 47. The mixture of syn--
thesis gas and liquid dispersion comprising particulate carbon,
water, and ash enters gas scrubbing and separation column 49
through line 50. A clean product stream of synthesis gas having
a high H2O/dry gas mole ratio in the range of about 1.0 to 2.0,
preferably about 1O2 to 1.8, such as 1.5 leaves by way of line
51 at the top of separator 49, and the liquid dispersion compris--
ing particulate carbon, water and ash leaves through bottom line
52, valve 53 and line 54.
The liquid dispersion comprising particulate carbon,
water, and ash in the bottom of quench tank 27 is passed through
line 6~, valve 61, line 62 and into line 63 where it is mixed
with the dispersion comprising
lZ(~Z8S
particulate carbon, water, and ash from lines 54 and 64
i~rom separator 49.
During normal operation about 45 to 55 volume
percent, such as 50 vol.% of the plant-design total
synthesis gas output is produced by gas generator 1.
Simultaneously with the operation of gas
qenerator 1, gas generator 2 is also being operated to
produce the remainder of the plant-design total synthesis
qas output. Preferably, synthesis gas generators 1 and 2
alre substantially of the same size and produce gas at the
same rate. Flow control means 85 in refractory lined line
86-87 is open, or alternatively flow control means such as
valve 108 is open, and the hot raw synthesis gas produced
in refractory lined reaction zone 88 of gas generator 2 is
split into two gas streams in thermal refractory lined
gas-diversion chamber 89. Flow control means 85 is a blank
flange plate or valve located in the line upstream or down-
stream from gas cooler 101 for controlling the flow rate,
or starting or stopping the passage of the split hot raw
synthesis gas stream therethrough. Heavy hydrocarbon fuel
feedstock containing high concentrations of metal compounds
from line 4, pump 7, line 8, optional heater 9, lines 10
and 90 is mixed in line 91 with a temperature moderator
such as steam from line 92. The mixture of fuel and steam
is introduced into the reaction zone of gas generatox 2 by
way of one passage in burner 100. In contrast with the
reactant fuel fed to gas generator 1, there is no soot
dispersion containing metals from line 5 mixed with the
reactant fuel feed to gas generator 2. A stream of
--7--
~2~42~5
free-oxygen containing gas from line 18 is passed through
line 96 and is introduced into reaction zone 88 of gas
generator 2 hy way of burner 100.
As previously mentioned, during normal operation
the raw effluent synthesis gas stream from reaction zone 88
in gas generator 2 is split into two hot, raw synthesis gas
streams. The two split, raw synthesis gas streams may be
produced at the same gas rate. For example, th~e first
split, hot raw synthesis gas stream may comprise about 10
to 40 vol.%, say 25 vol.~ of the plant-design total
synthesis gas output and may be passed through refractory
lines 86-87, flow control means 85, and conventional
convection-type gas cooler 101 where it passes in indirect
heat exchange with boiler feed water (BFW). The BFW enters
through line 102 and leaves as saturated or superheated
steam through through lines 97- 98. This steam is employed
as the temperature moderator in one or both gas generators.
Alternatively, a portion of steam may be xemoved for use
elsewhere in the system through line 110, valve 111 and
line 112.
The partially cooled synthesis gas leaves gas
cooler 101 through line 103 and is cleaned in gas scrubbing
a:nd separation column 104. The gas stream leaves by line
105 and is scrubbed free from entrained particu:Late carbon
a:nd ash in venturi scrubber 76 with water from line 78.
T:he mixture of synthesis gas and water passes through line
106 into column 104.
A stream of liquid dispersion of particulate
carbon, water, and ash leaves gas scrubber and separator
~2~ Z~3S
104 through line 115, valve 116, line 117, and is mixed in
line 118 with the stream of liquid dispersion of
particulate carbon, water, and ash from line 124 to be
described further. Further mixing takes place in line 70
with the stream of liquid dispersion of particulate carbon,
water, and ash from line 63. Conventional lock hoppers
~not shown) may be used to remove the liquid dispersion of
particulate carbon/ water, and ash from the bottoms of
quench tanks 27 and 73 and gas scrubbing and separation
columns 33, 49, and 104.
The stream of liquid dispersion of particulate
carbon, water, and ash in line 70 is processed in
soot-recovery facility 6.
Soot-recovery facility 6 may be any suitable
conventional mode for separating clarified water and a
portion of the ash from the liquid dispersion of
particulate carbon, water, and ash to produce the liquid
dispersion of soot in line 5. The clarified water stream
leaves through line 72 and a portion may be recycled to
quench tanks 27 and 73 by way of lines 74 and/or 75
respectively. Another portion of the clarified water may
be recycled to venturi scrubbers 35, 48 and 76 by way of
lines 36, 47 and 78, respectively. The stream of liquid
dispersion of soot in a liquid carrier from the group
liquid hydrocarbon fuel, water, and mixtures thereof is
passed through line 5 into mixer 14, previously described.
Soot comprises particulate carbon containing high metal
values. The remainder of the metals and metal compounds
leave the system through line 71 as the ash stream.
_g_
~2~42~S
A clean product stream of synthesis gas having a
low H20/dry gas mole ratio in the range of about 0.05 to
0.5 r such as about 0.1 leaves column 104 throu~h overhead
line 107, valve 108, and lines 109 and 41.
The second split, hot raw synthesis gas stream
may comprise the remainder of the hot, raw synthesis gas
produced in reaction zone 88 of synthesis gas generator 2.
For example, the second split, hot, raw, synthesis gas
stream may comprise about 10 to 40 vol.%, say 25 vol.% of
the plant-design total synthesis gas output. The term
'plant-design total synthesis gas output' is the total
volume of product gas that the system is designed to
produce, including both streams of synthesis gas with high
and low H~0/dry gas mole ratios, respectively.
The first and second split streams of hot, raw
synthesis gas are simultaneously processed. The second
split stream of hot, raw synthesis gas is passed through
chamber 89, refractory lined passage 13, dip-leg 120 into
water 121 contained in the bottom of a conventional-type
quench tank 73 located below reaction zone 88~ The
entrained particulate carbon and ash are removed form the
gas stream by the turbulent scrubbing action of the quench
water. The two streams of quench cooled and scrubbed
synthesis gas from lines 55 and 45 are mixed together in
line 46 and further cleaned in the manner previously
discussed to produce the clean product stream of synthesis
gas with a high H20/dry gas mole ratio in line 51. A
liquid dispersion comprising particulate carbon, water, and
ash in the bottom of quench tank 73 is removed through line
--10--
1204285
122, valve 123, line 124, and is mixed in line 118 with the
stream of liquid dispersion of particulate carbon, water
and ash from line 117, as previously described.
Quench water 26 and 121 in quench tanks 27 and 73
respectively and the quenched gas stream leaving the quench
tanks are at a temperature in the range of about 300 to
600F. such as about 400 to 500F. Similarly, the
temperature of the stream of synthesis gas in line 51 is in
the range of about 300 to 600F., such as about 400 to
500F.
In another embodiment, a conventional-type gas
cooler and scrubbing tower is provided downstream from gas
generator 1. This provides the system with greater
flexibility since either gas generator 1 to 2 but not both
could be operated to produce two split streams of hot, raw
synthesis qas - one hot split gas stream being cooled with
water in a quench tank while the othex hot, split gas
stream is cooled in a gas cooler. Simultaneously, all of
the hot, raw synthesis gas produced in the remaining gas
generator is quench cooled with water in a quench tank.
Further, all of the soot produced in the process and
separated in the soot recovery facility is recycled as a
portion of the feed to the gas generator from which all of
the hot, raw synthesis gas is normally directly quench
cooled in water. Accordingly, in this second embodiment
with all of the hot raw, synthesis gas produced in gas
generator 2 being passed directly into quench tank 73, flow
control means 22 or alternatively 39 is open and flow
control means 85 or alternatively 108 is closed. Further,
- --11--
4~35
the feedstream in lines 3 and 91 are switched to gas
generators 2 and 1, respectively. The hot, raw split gas
stream in insulated lines 23 and 28 is cooled in
conventional convection-type gas cooler 29 by indirect heat
exchange with boiler feedwater (BFW) from line 30~
Saturated or supPrheated steam is produced and leaves
through outlet line 31 for admixture with at least one of
1:he reactant feedstreams in lines 3, 20, 91, or 96. The
1:emperature of the partially cooled gas stream leaving gas
cooler 29 or alternatively in the other embodiment from gas
cooler 101 is in the range of about 250 to 750F., such as
about 350 to 500F. The partially cooled synthesis gas in
line 32 is cleaned in gas scrubbing and separation column
33, passed through line 34 into venturi scrubber 35 and
scrubbed free from particulate carbon and ash with water
from line 36, passed through line 34 into venturi scrubber
35 and scrubbed free from particulate carbon and ash with
water from line 36, and then passed through line 37 into
column 33. The temperature of the stream of synthesis gas
leaving column 33 or alternatively in the other embodiment
from column 104 is in the range of about 200 to 400F.,
such as about 250 to 350F. A product stream of clean
synthesis gas having a low H20/dry gas mole ratio in the
range of about 0.05 to 0.5, such as about 0.1 is removed
from vessel 33 by way of line 38, valve 39, and lines 40
and 41. A water dispersion produced by scrubbing the
entrained particulate carbon and ash from the split stream
of synthesis gas is removed from the bottom of vessel 33 by
way of line 42, valve 66, and line 67, and mixed in line 70
~z(~4~8S
with the streams of liquid dispersion comprising
particulate carbon, water, and ash from lines 54, 64, 63
and 118.
Advantageously, the flexibility of this system is
such that either one or two streams of synthesis gas may be
continuously produced even though one of the gas generators
or associated gas cooler may have to be shut down for one
reason or another. For example, with both synthesis gas
generatoxs 1 and 2 of the same size, if either gas
generator had to be shut down, then during standby of the
shutdown gas generator, the gas generator remaining in
operation is capable of producing through quench one gas
stream in the amount of up to about 75 vol.%, such as 50-75
vol.% of the plant-design total synthesis gas output with
no gas stream being cooled in a convection-type gas cooler.
Alternatively, during standby of one gas generator, the
other gas generator in operation and fitted with a gas
cooler is capable of producing one split gas stream through
quench in the amount of up to about 50 vol.%, such as 30 to
50 vol.%, of the plant-design total synthesis gas output;
and simultaneously cooling in an associated convection-type
gas cooler for limited periods of time a second split gas
stream in the amount of up to about 25 vol.%, such as about
10 to 25 vol.% of the plant-design total synthesis gas
output.
Partial oxidation gas generator 1 for producing
the hot, raw synthesis gas containing entrained particulate
carbon and ash comprises a vertical unpacked free-flow
noncatalytic cylindrical shaped steel pressure vessel lined
2~S
with refractory, such as shown in coassigned U.S. Patent No.
2,809,104. A typical quench drum is also shown in said patent.
~artial oxidation gas generator 2 with a quench tan]c and gas
cooler for producing split streams of synthesis gas is shown in
coassigned U.S. Patent No. 4,141,696. A bu~ner, such as shown
in coassigned U.S. Patent No. 2,928,460, may be used to intro-
duce the feed streams into the reaction zone of the gas gene-
rators. The atomic ratio of free oxygen to carbon in the fuel
(O/C ratio), is in the range of about 0.6 to 1.6, and preferably
about 0.8 to 1.4. The exothermic partial oxidation reaction
takes place in the presence of a temperature moderator selected
from the group steam, water, CO2, N2, cooled and cleaned re-
cycled synthesis gas and mixtures thereof. When steam or water
is used as a temperature moderator, the H2O/fuel weight ratio in
the reaction zone is in the range of about 0.1 to 5~ and prefer~
ably about 0.2 to 0.7. The partial oxidation reaction takes
place in the reaction zone of the partial oxidation gas gene-
rator at an autogenous temperature in the range of about 1,700
to 3,500F., such as in the range of about 2,000 to 2,800F.,
and a pressure in the range of about 5 to 300 atmospheres, such
as about 15 to 200 atmospheres.
The composition of the hot, raw effluent gas stream
directly leaving the reaction zone of the partial oxidation gas
generator is about as follows, in mole percent: H2 10 to 70,
CO 15 to 57, CO2 0.1 to 25, H2O 0.1
~1
~2~4~8S
to 20, CH4 nil to 60, H2S nil to 2, COS nil to 0.1, N2 nil
to 60, and Ar nil to 2Ø Particulate carbon is present in
the range of about 0.2 to 20 weight % (basis carbon content
in the feed). Ash is present in the range of about 0.05 to
5.0 wt. %, such as 0.1 to 1.0 wt.% (basis total weight of
fuel feed) when no soot dispersion from line 5 is mixed
with the heavy hydrocarbon fuel feedstock (as in line 91),
and in the range of about 0.2 to 20.0 wt.~ when the soot
dispersion from line 5 is in admixture with the heavy
hydrocarbon fuel (as in line 3).
Depending on the composition after removal of the
entrained particulate carbon and ash by quench cooling
and/or scrubbing with water and with or without dewatering,
the gas stream may be employed as synthesis gas, reducing
gas, or fuel gas.
The heavy liquid hydrocarbon fuel containing high
metal concentrations which is used as the principal fuel
feed in partial oxidation gas generators 1 and 2 is
generally unsatisfactory for use as a fuel for many
purposes because of the corrosive nature of the ash. The
corrosiveness of the ash is due primarily to the oxidation
products of the naturally-occuring metal compounds.
Advantageously, by the subject process these comparatively
low cost fuels may now be used as a source for synthesis
gas. These heavy liquid hydrocarbon fuels have a density
in degrees API of 10 or less, and an initial boiling point
of greater than 400F. Such as in the range of about 400
to 600F., say 450 to 500F, when measured at atmospheric
pressure in accordance with standard test methods of the
-15-
~2~Z~35
American Society For Testing and Materials.
Naturally occurring metalic compounds or
principally vanadium, nickel and iron, and traces of
chromium and molybdenum, if any, including oil-soluble
materials, colloidally dispersed metallic compounds and
complex organometallic compounds, are present in these
heavy liquid hydrocarbon fuels. The metals and compounds
are present in combined amounts ranging from about 10 parts
per million (ppm) to over 5000 ppm, such as about 50 to
2000 ppm, say over 250 ppm (basis weight of the fuel). The
reaction products of said metal constituents leave the
reaction zone of the gas generator as metallic, oxide and
sulfide ash particles entrained in the effluent gas stream.
A portion of the ash, i.e. about 5 to 75 wt.%
(basis weight of ash) is separated from quench cooling and
scrubbing water in th~ conventional soot recovery facility
6, for example by sedimentation. The remainder of the ash
is recycled to the gas generator along with ~he liquid
dispersion of soot. The liquid carrier in the soot
dispersion is selected from the group water, liquid
hydrocarbon fuel, and mixturçs thereof. The solids content
is in the range of about 0.1 to 8.0 wt.%, such as about 1.0
to 6.0 wt.~, and comprises a combination of particulate
carbon and ash. About 5 to 50 wt.% of the soot comprises
the metals Ni, V, and Fe and their reaction pro~ucts; and
the remainder is carbon.
Heavy liquid hydrocarbon fuel containing high
metal concentrations suitable for use in the subject
process may be selected from the group consisting of crude
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~2~4Z~3S
residua from petroleum distillation and cracking process
operations, petroleum distillate, reduced crude, whole
crude, asphalt, coal tar, coal derived oil, shale oil, tar
sand oil, and mixtures thereof. Pumpable slurries of solid
carbonaceous fuel, e.g. particulate carbon, petroleum coke,
and mixtures thereof in a vaporizable carrier,~uch as
water, liquid hydrocarbon fuel and mixtures thereof are
included within the definition of said heavy liquid
hydrocarbon fuel.
The free-oxygen contaiing gas employed in the
subject process is selected from the group consisting of
air, oxygen-enriched air, i.e., greater than 21 mole % 2
cmd substantially pure oxygen i.e. greater than 95 mole %
t)2. The temperature moderator is selected fxom the group
consisting of steam, water, C02-rich gas, nitrogen, and
recycled synthesis gas.
lZ~2~S
EXAMPLE
The following example illustrates a preferred
embodiment of this invention pertaining to the continuous
operation of a partial oxidation process employing heavy
hydrocarbon ~uel feedstocks containing high me1:al
concentrations and total soot recycle without plugging and
Eouling the tubes of a downstream convection-type gas
cooler.
While preferred modes of operation are
illustrated, the Example should not be construed as
limiting the scope of the invention. The process is
continuous and the flow rates are specified on an hourly
basis for all streams of materials.
160,408 lbs. of a vacuum resid having a gravity
of 2.0 degrees API and an Ultimate Analysis in weight
percent as follows: C 83.45, H 10.10 , N 0.35 , S 5.5 ,
and O 0.6 and containing the following metals in parts per
million (ppm) V 594, Ni 98, and Fe 64 in admixture with
5530 lbs. of recycled unreacted carbon in a liquid
dispersion comprising 5.0 wt.% of soot with metals in a
liquid carrier comprising said vacuum resid are mixed with
65,981 lbs. of steam fxom gas cooler 101 at a temperature
of 574F and a pressure of 1165 psig. The mixture is passed
through a passage in burner 17, at a temperature of 560F.
and a pressure of 1120 psig. The burner is located in the
upper end of conventional vertical refxactory lined
free-flow noncatalytic unpacked synthesis gas generator 1.
Simultaneously, a stream of 174,453 lbs. of
substantially pure oxygen i.e., 99.5 mole % 2 at a
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temperature of 300F and a pressure of 1165 ps:ig. is passed
through another passage of the burner. The feed streams
impinge, mix and the partial oxidation and other related
reactions then take place in the reaction zone of gas
generator 1. A stream of 8.80 million standard cubic feet
(SCF measured at 60F., 14.7 psig.) of hot raw synthesis
gas leaves the reaction zone of the gas generator at a
temperature of 2,596F and a pressure of 1,050 psig. The
composition of the raw, synthesis gas in chamber 24 is
shown in Column 1 of Table 1. ~bout 2,822 lbs. of
unreacted particulate carbon and 1,413 lbs. of ash are
entrained in the raw synthesis gas. The term 'ash'
includes all of the reaction products of the metal
compounds in the fuel feed to the gas generator.
With a flow control means for line 23 closed,
such as 22 or alternatively 39, all of the hot raw gas
stream leaving reaction zone 16 is introduced into quench
water in quench tank 27, carrying with it substantially all
of the entrained particulate matter, i.e., particulate
carbon and ash being produced. The stream of raw synthesis
gas is cooled and cleaned by the quench water and by
supplemental scrubbing with water in venturi scrubber 48
and scrubbing and separating column 49 to produce the clean
product stream of synthesis gas with a high H20/dry gas
mole ratio of 1.57. This product stream of synthesis gas
in line 51 comprises 30.45 million SCF and has the
composition shown in Column 2 of Table 1.
Simultaneously, 164,304 lbs. of a feedstream of
vacuum resid from line 4 at a temperature of 574F and a
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~2Q4~35
pressure of 1,165 psig. in admixture with 63,8:38 lbs. of
steam from gas coolPr 101 is passed through one passage of
burner 100 located in the upper end of conventi.onal
vertical refractory lined free-flow noncatalyti.c unpacked
synthesis gas generator 2. A feedstream comprising 167,612
lbs. of substantially pure oxygen i.e., 99.5 mole ~ 2 from
line 18 at a temperature of 300F. and a pressure of 1,165
psig. is passed through another passage of burner 100. The
feedstreams impinge, mix, and the partial oxidation and
other related xeactions then take place in the reaction
zone of gas generator 1. A stream of 8.59 million standard
cubic feet (SCF) (measured at 60F., 14.7 psig.) of raw
synthesis gas leaves the reaction zone of gas generator 2
at a temperature ~f 2,504F. and a pressure of 1,050 psig.
The composition of the raw synthesis gas in chamber 89 is
shown in Column 3 of Table 1. About 2,706 lbs. of
unreacted particulate carbon and 165 lbs. of ash are
e~ntrained in the stream of raw synthesis gas.
With flow control means for line 86 open, such as
~5 or alternatively 108, all of the raw effluent gas stream
l.eaving reaction zone 88 is immediately split into two hot
raw gas streams in gas-diversion chamber 98. The first
split hot raw gas stream comprising 4.29 millio:n SCF of raw
synthesis gas is passed through insulated passages 86 and
87, and cooled in gas cooler lQl. The second split stream
comprising the remainder of the hot raw effluent gas stream
is simultaneously passed through dip-leg 120 and quench
cooled in quench tank 73. The actual split between the two
trains may be controlled by back pressure valves in each
line.
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~2Q4;~:~35
The partially cooled first split gas stream
]eaving gas cooler 101 is scrubbed with water to produce
4.30 million SCF of clean synthesis gas with a low H20/dry
qas mole ratio of 0.093. This product stream of synthesis
gas in line 41 has the composition shown in Column 4 of
Table I.
The water dispersion of particulate matter is
removed from quench tanks 27 and 73 and from gas scrubbing
and separating towers 33, 49 and 104 and processed in
conventional soot recovery facility 6. About 697~503 lbs.
of clarified water (line 72), 719 lbs. of ash (line 71),
and 140,910 lbs. of a soot-vacuum resid dispersion (line 5)
axe obtained. The water is recycled to the quench tanks
and scrubbers, ~he ash is removed and sent to a metals
recovery plant for sepaxating by-product vanadium and
nickel, and the soot-vacuum resid dispersion is mixed with
the heavy hydrocarbon fuel and recycled to gas generator 1
as a portion of the fuel, as previously described.
TABLE I
GAS COMPOSITION
Column No. 1 2 3 4
Drawin~ Reference No. 24 51 89 41
% ~ ~OLE -~ - - -
C0 44.87 19.29 44.25 44.34
H 39.51 16.99 40.23 40.31
C~ 4.33 1.86 4.21 4.22
H ~ 9.51 Ç1.10 9.53 9.71
C~4 0.36` 0.15 0.36 0.36
Ar 0.12 0.05 0.12 0.12
N2 0.09 0.04 0.09 0.09
H S 1.15 0.50 1.15 1.15
C~S 0.06 0.03 0.06 0.06
Metals and Metal
Compounds ~PPM) 3470 - 420
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~Z~ 2~5
By the subject invention, even though there is
total carbon recycle in the process the metals content of
the raw, split gas stream continuously enterinq a
convection-type gas cooler may be limited to a value which
will not exceed that corresponding to the metals content of
the fresh hydrocarbon fuel feedstock. Build-up of metal
deposits and fouling of boiler tubes may be thereby
prevented and the life of the gas cooler extencled.
Advantageously, the subject system provides for
flexible operation and equipment back-up. In t:he event one
yas-cooler or gas scrubber has to be shut down, for example
for maintenance, a large proportion of the plant-design
total synthesis gas output can be continuously produced by
the other train. Further, two product streams of synthesis
gas with high and low H20/dry gas mole ratios respectively
may be simultaneously produced frsm low cost fuels
containing a high metals content and total recycle of all
soot produced in the system and with no substantial
plugging or fouling of a convection-type gas cooler in the
system.
The process of the invention has been described
yenerally and by examples with reference to heavy
hydrocarbon fuel and synthesis gas having particular
compositions for purposes of clarity and illustration only.
It will be apparent to those skilled in the art from the
foregoing that various modifications of the process
disclosed herein ran be made without departure from the
spirit of the invention.
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