вход по аккаунту


Патент USA US2113536

код для вставки
April 5, 1938.
Filed March 5, 1936
3 Sheets-Sheet l
,/f,1/////l/11//f/f/// /
I5, ,
///«5. I'
/////\ \
April 5, 1.938.
Filed March 5, 193s
s sneéts-sheet s
Patented Apr. 5, 1938`
John J. Grobe, George Miller Hebbard, and Ralph
E. Schneider, Midland, Mich., assignors to The
Dow Chemical Company, Midland, Mich., a
corporation of Michigan
Application March 5, 1936, Serial No. 67,336
1 Claim. (Cl. 2130-170)
'This invention relates to a method and appa
ratus for producing unsaturated hydrocarbon
gases by pyrolysis or cracking of hydrocarbons.
More particularly, it is concerned with improve
6 ments> in the cracking of hydrocarbon oils yby
means of superheated steam, whereby heavy oils
or tars may be cracked to produce a gas mix
ture high in oleiines or acetylene.
A method of cracking hydrocarbon oils to pro
!0 duce gaseous olei'lnes is described in United
States Patent No. 1,962,502, which consists in
vaporizing oil, preheating the vapors and then
mixing such vapors with superheated steam in
amount and at a temperature such that the
l5 oil is heated to a suitable cracking temperature,
substantially all of the heat required for the
cracking being supplied by the superheated
steam. The oil vapors are preheated to a tem
perature of about 550° to 700° C., while the
20 superheated steam is supplied at a temperature
between about 950° and 1200° C., so as to produce
in the resultant mixture a temperature between
'700° and 1000° C., this lbeing the range within
which gaseous oleñnes are chiefly formed. The
25 cracking is carried out in the presence of sur
faces of magnetic iron oxide, FesOr, which acts
as an anti-catalyst to prevent carbon formation.
The hot reaction gases, having a. high content
of gaseous oleñnes, are passed in heat exchange
30 with the incoming oil to vaporize and preheat
withstand high temperatures or the action of
combustlon gases and steam at such tempera
tures for an extended period of time. The avail
able metals are subject to distortion and em
brittlement by the action of the heat, as well 5
as to severe chemical attack by the hot gases.
- It is an object of the present invention to
provide an improvement in the method of the
aforesaid Patent No. 1,962,502, whereby heavy
oils can be cracked successfully to produce un- 10
saturated gaseous hydrocarbons with the same
facility as in the case of light oils. A further
object is to increase the production of ethylene
relative to the higher oleñnes.
Still another _
object is to increase the production of unsatu- l5
rated gases of the acetylene series. Another
object is to make practically possible in an eco
nomical manner the supplying of superheated
steam at temperatures much higher than are
now feasible with usual metallic equipment. 20
Other objects will' appear as the description
The heavy oil.;, for the cracking of which our
method or process is primarily intended, include
crude petroleum, heavy distillate oils, gas oil, 25
residuum oils, fuel `oil, tar oils, as well as tars
derived from wood and coal distillation.
We have found that heavy oils can be cracked
successfully on a commercial scale by injecting
the oil substantially as liquid directly into a 30
the same, then further cooled to condense water ' current of steam superheated to a temperature
and separate the latter from the permanent materially above about 1000° C., e. g. between
The commercial practice of the aforesaid
„o method has disclosed certain limitations and dis
advantages. It was -found that the preliminary
vaporization of the oil an., preheating of the
vapors, while proceeding satisfactorily with a
petroleum distillate such as kerosene, could not
40 be carried out practically with heavier oils, be
cause such heavy oils in some cases could not
be vaporized and in other cases would be par
tially cracked in the process, accompanied by
tar and carbon formation which soon caused
45 stoppage of the preheating coils. The method,
therefore, was successful for use only with light
1000° and 1350° C., thus avoiding the necessity
for separately vaporizing the oil and preheating
the vapors, and also preventing carbonization 35
and the attendant difficulties caused thereby.
We have alsol found that by using such highly
superheated steam the yield of ethylene relative
to higher oleñnes is increased, this result being
more marked when’the steam is superheated to 40
temperatures above about 1200° C.
'I'his is of ’
great practical advantage, inasmuch. as ethylene
is more desirable commercially- than the higher
oleñnes, and the expense of separating the ethyl
ene from the higher oleñnes is reduced in the 45
proportion that the content of higher oleñnes in
the gaseous product is lowered. It has 'also been
found that our improved method is adapted to
producing directly a gaseous product having a
higher content of acetylene than is obtained by 60
oils which could be vaporized and preheated with
out incipient cracking and resultant formation
of tar and carbon.
Another limitation was caused by the inability
other processes based upon a thermal treatment
of commercial superheaters to deliver super
heated steam for long continued operation at a. of hydrocarbons. In 'a range of temperatures
temperature appreciably higher than about 1000° between 700°. and 1000° C. the gaseous products
to 1050° C., due to the fact that no practical - of the cracking are chiefly oleñnes, but, as the
55 construction metals were known which could cracking temperature is raised to around 1000° C. 65
and higher, commercial yields of acetylene are
In order to produce superheated steam eco
nomically on a commercial scale at temperatures
in excess-of about 1000” C., suitable for use in
our improved method or process, we have adapt
ed a “stove” type of superheater in which a per
vious mass of high temperature refractory ma
terial is first heated to a high temperature and
10 then used for transmitting heat tothe steam.
ing section 4. superheater section I is formed
by a cylindrical steel shell,` having a conical
top, the whole provided with a lining of refrac
tory and heat insulating material. Within
superheater I, at the left, is a vertical heat
storage chamber 5, enclosed by arcuate walls 6,
which rise to a point some distance below the
top'of shell I, the one wall following the curva
ture of the outside shell, and the opposite wall
having a reverse curvature, as shown particular
This type of apparatus requires the use of alter
ly in Figs. 2 and 3.
nate periods of heating the refractory material
and for superheating steam by contact with the
hot refractory to a suiilciently high temperature
superheater chamber proper, and is fllled with
15 for mixing with the oil to crack the same under
the desired conditions. Such intermittent mode
of operation, comprising alternate periods of
“firing” and of cracking, tends to cause tem
perature variations in the gases during the re
20 spective periods.
These variations, however,
particularly in the cracking period, may be re
duced greatly by disposing a body of heat ab
sorbent material in the path of the current of
superheated steam, to serve as_ a heat storage
25 or ballast, absorbing heat during the early part
of the cracking period and giving it up during
the later part of the period, thereby smoothing
The space 1 to the right
of wall 6 forms a second chamber which is the
refractory brick checker-work nearly to the top
of wall 6, leaving an open combustion space 8 15
at the top of superheater section I. At the bot
tom of superheater chamber 1 is a ñue 9 leading
to a stack I0, in which flue is a steam inlet pipe
II and stack valve I2. At the top of combustion
space 8 is an opening I3 communicating with
an air chamber I4, within which opening I3 is
located an oil or gas burner I5.
ing with vertical chamber 5 near the bottom is
a horizontal cracking chamber 4, lined with re
fractory material, such as fire brick. An expan 25
sion joint I6 is provided in the outer steel cas
ing I1 of cracking chamber 4, which joins at
out the temperature curve in the cracking zone . its further end with a condenser and cooler I9.
and enabling a control of the cracking tempera
30 ture within a few degrees.
By our improved method we are able to crack
heavy oils injected directly into a current of the
superheated steam of sufficiently high tempera
ture and produce an equal or higher yield of
35 unsaturated gases at a steam consumption no
greater than was formerly required to crack va
porized and preheated light oils according toÄ the
method of the aforesaid Patent No. 1,962,502.
Although in our method the reactions in the
40 cracking zone take place in a temperature range
whereat steam and hydrocarbons are known to
react to form water gas, i. e. CO-i-Hz, the instan
-taneous cracking of the oil, followed by imme
diate cooling, produces a gas mixture containing
negligible amountsof CO and only such amounts
of hydrogen as are derived principally from the
decomposition of the heavy hydrocarbons. We
have also found that under the conditions of our
improved method the use of magnetic iron oxide
50 is not required to prevent carbon formation, and
continuous operation may be maintained with
out the presence of any known anti-catalyst for
carbon formation.
Our improved method and apparatus ‘therefor
is fully described in the annexed drawings and
following specification.
In said annexed drawings:
Fig. 1 is an elevation, largely in section, of a
preferred `form of apparatus comprising a self
60 contained unit for superheating steam
cracking oil.
line 39, controlled by valve 38, While cooling
water and condensates are removed through
drain 40. Reactor 4 is equipped with tempera 65
ture indicating means, such as thermocouple 4I.
The apparatus operates upon a cycle made up
of three periods, namely, a firing period, a purge
period, and a cracking period. During the first,
or firing, period fuel injected through burner 60
Fig. 5 is a curve sheet showing the variation
in yield of unsaturated gases according to the
I5 is burned in combustion space 8. 'I‘he hot
combustion gases sweep through the checker
work inv chamber 1, to heat the same to a high
temperature, and thence out through flue 9 to
stack I0. At the start of the firing period valves 65
24 and 21 for fuel and air supply to burner I5,
also stack valve I2 are opened, all other valves
being closed. Combustion proceeds until the
upper checker-work in section 1 reaches a suit
able high temperature, i. e. a temperature of 70
about 1300° C. or higher, as observed by the
cracking temperature.
color of the checker-work when viewed through ,
Fig. 2 is a horizontal cross section on the line
2-2 of Fig. 1.
Fig. 3 is a horizontal cross section on the line
3-3 of Fig. 1.
Fig. 4 is a diagrammatic plan view of an appa
ratus including two superheating and cracking
units interconnected to give continuous gas pro
Oil to be cracked is supplied to chamber 4
through injector I8. Within chamber 5 is a 30
pier 20 of refractory material with an arched
opening at the lower end opposite the inlet to
cracking chamber 4, as shown in Figs. 1 to 3.superheater section I is equipped with one or
more explosion disks 2| and a sight glass 22.
Materials are supplied to the apparatus as
followsz-Fuel for combustion is carried to burn
er I5 by pipe 23 having a control valve 24, and
steam for cleansing and blanketing the burner,
as hereinafter explained, is supplied during cer
tain periods through steam pipe 26 in which is
valve 25. Air for combustion is supplied to air
chamber I4 by air-duct 28 controlled by valve 21.
Steam introduced into flue 9 through pipe II
is controlled by valve 29. Oil injector I8 in
cracking section 4 is supplied with oil and with'
steam for atomizing the oil through pipes 32 and
33, respectively, which are controlled by valves
30 and 3I. Cooler I9 is supplied with water
through water pipe 35, in which is a valve 34, 50
and gaseous products are removed either through
vent pipe 31, controlled by valve 36, or by gas'
sight glass 22 or as indicated »by an optical py
Referring to Figs. 1-3, the apparatus com
prises a vertical superheater section I, of rela
rometer, not shown. »In starting a new unit,
75 tively large size, with which is combined a crack-' it is of course necessary to determine experi
mentally the proper rates of firing to give the
desired temperature in a given firing period.
'I'he i'lring period is followed by a brief purge
period, the purpose of which is to sweep the
apparatus free of air and combustion gases.
Stack valve I2, fuel valve 24, and air valve 21
including time for changing valves. during which
period steam was passed through the whole as
sembly from the stack opening in the super
heater to the condenser blow-off vent, and a 15
minute firing period during which oil was cracked,
as previously described in detail.
, When operating( on this 30 minute cycle, the
are closed, cooler vent valve 36 and water sup
ply valve 34 are opened, and steam is admitted average consumption of materials per hour was
to flue 9 and burner I5 by opening valves 29` 1820 pounds of steam at ñve pounds gauge pres
and 25À in steam lines II and 26, respectively, ' sure superheated to a temperature of 1155° C._-|
10° C., measured at' bottom of chamber 5, and
the former supplying volume steam for purg
530 pounds of fuel oil having a speciñc gravity
ing, and later for cracking, and the latter sup
plying steam in smaller amount to cleanse the of 0.895, supplied at a temperature of 165° C.,
burner passages and also to blanket the burner which was atomized by" 66 pounds of steam at
_150 pounds pressure. In the stated propor
15 I5 and protect the same from radiant heat.
As soon as the system is purged, the vent valve tions the average temperature in the cracking
36 is closed, gas-line valve 38 is opened, and the zone was approximately 850° C. Oil used for
cracking period is commenced by opening oil and combustion was in the ratio of about 0.44 pound
per pound of Voil cracked.
steam valves 30 and 3|, respectively, thus admit
On a continuous run of 800 hours, approxi
20 ting oil to injector I8, where it is atomized by
the steam and injected into the current of su-> mately 1,800,000 cubic feet of cracked gas were
perheated steam in chamber 4. The proportions produced at a production rate varying from 4600
to 5400 cubic feet per hour. An approximate av
of oil supplied to injector I8 and of steam ad
mitted to' the superheater through pipe> II are erage analysis of the gas, in percentage by weight,
25 adjusted to give the desired temperature of the Was:
mixed gases and vapors in the cracking zone,
H2 ________________________________ ______
CH4l ______________ __ _____________________ _.
eter 4i.
C2H2 __________________________________ __
The oil is cracked down to gas almlostv
To operate the apparatus," automatic valve-op
erating mechanism of any suitable known, type
may be employed for coordinating the vopening
and closing of the various valves.
Since a single-unit installation, such as de
scribed, produces gas intermittently, two similar
units may be arranged to operate in parallel on
cycles so related that a continuous supply of gas
is produced, as shown diagrammatically in Fig
Ol Ul ure 4, the operation of which will be readily ap
parent from the foregoing description.
In practice the following results have been ob
tained in operating a superheater-reactor unit as
shown in Figs. 1 to 3. The apparatus had an in
60 ternal diameter of 4 feet 9 inches and an over
all height of about 30.feet, the brick checker
work occupying a space of 20 feet in height
and 13 square feet in cross-sectional area, in
which the brick were laid to form straight, ver
tical gas passages two inches square. The heat
ballast chamber had an open cross-sectional area
of two square fee't. The cracking' chamber con
sisted of a steel shell lined with fire brick form
ing a combustion space approximately six inches
70 in diameter and 48 inches long, which commu
nicated with a water spray cooler.
This unit was operated upon a thirty-minute
cycle, composed of a 14- minute firing period, dur
ing which heat was stored in the superheater
75 checker-work, a purge period of about 1 minute,
which may be indicated, for example, by pyrom
instantaneously, by transfer of heat from the su
perheated steam. The hot gases admixed with
steam pass immediately into cooler I8, wherein
they are brought in contact with a water vspray
which cools the gases and condenses the excessV
steam, the cooled gases being conducted away to
a gas holder through pipe 39, while the condenser
water ñows out through outlet 48.
When the temperature in the cracking cham
ber 4 falls to a point below which it is not desired
to continue cracking, oil control valve 30, steam
valves 25, 28 and 3l, water valve 34 and gas line
valve 38 are closed, stack valve I2, air valve 2'I
and fuel feed valve 24 are opened and burner
I5 is ignited, thus starting a new cycle of oper
ation, which is constantly repeated as the process
is continued.
C21-I4 ______________________ __` __________ __ 44.7
CsHs and higher ________________________ __ 33.7
CO ____________________________________ __
CO2 _____________________________ _, _______ __
N2, O2, etc _________________________ _______ .0.5
In the foregoing example a cracking tempera
ture was chosen which was adapted to produce
approximately a maximum yield of gaseous ole
ñnes. However, a considerable range is permis
sible in the temperature of the cracking Zone,
when practicing the present method, depending
upon the desired composition of the gaseous
By operating at higher temperature
the percentage of total oleiines in the gas pro 45
duced is decreased, but the diminution of yield
of ethylene proceeds at a much slower rate than
that of the higher oleñnes, while, on the other
hand, the percentage of acetylene increases. The
variation in gas composition with' changes in
cracking temperature is shown approximately by
the chart Fig. 5 for temperatures up to 1200° C.
For instance, at 1000° C. the gas produced would
contain about 41 per cent of ethylene, 14 per cent
of higher olefines, and l2 per cent of acetylene, 55
by weight. By raising the cracking tempera
ture above 1000° C. up to l200° or 1400° C., the
percentage of acetylene is increased still further,
while that of the oleñnes fall substantially to
As stated, the percentages of the unsaturated
gases in the product of our process, according
to the curves in Fig. 5, are only. approximate,
since various factors influence the composition
of the gas within certain limits. In particular, 65
we have found that the ratio of ethylene to
higher oleñnes in the gas can be varied by vary
ing the temperature of the superheat'ed steam
employed for cracking the oil, although the aver-.
age gas temperature Iin the cracking zone may
remain substantially the same.
With higher
steam temperatures' the ratio cf ethylene to
higher olei'lnes is higher than with lower steam
temperatures. For example, when using steam
superheated to about 1070° C. and mixing with 75
perature of approximately 850° C. in the cracking
zone, the ratio by weight of ethylene to higher
oleiines in the product was l/1. When, how
many purposes can be employed without addi
tional drying. The cooling of the hot reaction
gases may be accomplished in other ways known
to the art, however, and may be conducted in
ever, superheated steam at about 1230° C. was
one or more stages, as desired. The cooling to a
oil in proportions to maintain an average tem.
temperature below the cracking point, i. e. below
zone remaining at 850° C. as before, the ratio of ~ about 600°-700° C., should be rapid, but below
ethylene to higher oleñnes in the product was that the rate and extent of cooling is limmaterial
as far as this invention is concerned.
1.25/1. In case ethylene is the principal gas
In the practice of our invention we are enabled
ecus product desired. it is most advantageous to
to crack hydrocarbon oils under conditions most
employ steam superheated to a temperature ma.
terially above 1200° C.~ for cracking the oil, the favorable for production of high yields of un
saturated gases without formation of appreciable
average temperature of the gases in the crack
ing zone being maintained preferably between amounts of tar and carbon. We have found that
in long-continued operation of the process no
850° and 1000° C.
By reference to the curves in Fig. 5 it will be carbon accumulations are formed in the crack
seen that our improved process is well adapted to ing chamber, hence there is no necessity to em
the production of acetylene, as well as gaseous ploy special materials or anti-catalysts to in
oleflnes. At cracking temperatures above about hibit carbonl formation. Our apparatus avoids
the use of metallic surfaces for transferring heat
1000° C. the percentage of acetylene in the prod
. uct rises rapidly," whereas that of the oleflnes to the oil vapors being cracked, thereby permit
ting the required high temperature conditions
Apparently the formation of acety
- diminishes.
lene is at the expense of the oleilnes. By raising to be maintained continuously for long periods
the temperature in the cracking zone above 1000° of time under conditions whereat usual metallic
construction materials would be rapidly burnt,
25 C., which is done by employing superheated steam
at temperatures materially above 1200° C. and corroded and destroyed. The process is, there
mixing it with the oil in suitable proportion, a fore, independent of the limitations of metallic
apparatus when exposed to steam and combus
good yield of acetylene is obtained. For exam
ple, at 1200° C. the gaseous product will contain tion gases at high temperatures. The process is
likewise more economical of heat than would be
30 around 25 per cent, by weight, of acetylene, while
the percentage of olefines becomes vanishingly possible in other processes employing externally
heated tubes or retorts for cracking the oil.
small. A further increase in the cracking tem
The particular object of the invention, to en
perature, e. g. to as much as 1400° C., will produce
able the cracking of heavy hydrocarbon oils and
still higher yields of acetylene.
Therefore, our present process is adapted to the like to- produce unsaturated gases, is success
fully accomplished Without sacrifice of yield or
the production of gaseous oleflnes or o_f acety
lene, or both, the percentage yield of gaseous experiencing difllculty due to formation of tar
products being controllable by regulating the and carbon, or to rapid deterioration of appa
temperature of the superheated steam and of the ratus, such as has heretofore limited the produc
used, the average temperature of the cracking
40 mixed gases in the cracking zone.
upon the cracking conditions desired, the temper
ature to which the steam is superheated will be
varied accordingly, in general ranging from about
1000° to as high as 1800D C. For‘producing chief
ly gaseous oleñnes suitable superheated steam
temperatures are between 1000° and 1350° C.,
whereas, when acetylene is the principal product
desired, steam temperatures of from 1200° to as
high as 1800“ may be used. Under the tempera
50 ture conditions described the cracking of the oil
proceeds at substantially atmospheric pressure.
In practice, however, it is advantageous to main
tain a moderate steam pressure, e. g. about 2 to 10
pounds gauge, in the superheating and cracking
55 zones, so as to maintain a sufficient rate of flow
. in the process.
It is important to cool the gases from the
cracking zone rapidly to a point below the normal
cracking temperature, in order to avoid side re
60 actions leading to the formation of saturated
hydrocarbons and carbon monoxide. As already
stated, the cracking to form unsaturated gases
. takes place practically instantaneously, hence
there is no necessity to maintain the gases at the
65 cracking temperature for any appreciable length
of time. The quick and sudden cooling of the
hot gases is effectively accomplished in the man
ner hereinbefore shown, by bringing them into
intimate contact with a water spray in sufñcient
70 volume to condense the steam. Such manner of
cooling is also effective to scrub the gases and re
move therefrom any small amounts of tar, car
bon or incompletely decomposed oil contained
therein. The cooled and` scrubbed gases may be
76 further dried by known means, if desired, but for
tion of rich unsaturated gases from heavy oils. 40
By enabling the cheaper heavy oils to be used
successfully as raw nïaterial an important eco
nomic advantage is gained as compared with'all
processes heretofore used for producing unsatu
rated hydrocarbon gases. It is to be remarked
that the usual steam consumption in our im
proved process, using heavy oil, which may vary
from about 3 to 8 pounds of superheated steam
per pound of oil cracked, depending upon condi
tions and the type of the oil, is equal to the re
sults obtained in the process of the Aaforesaid
Patent No. 1,962,502, wherein it was necessary
to employ a light distillate and to vaporize the
same and preheat the vapors before mixing them
with the superheated steam. The process is not
limited to cracking heavy oils or tars, however,
but is also adaptable to cracking light oils and
distillates, such as the kerosene and gasoline frac
tions obtained in the distillation of petroleum, as
well as hydrocarbons generally, including both
liquid and gaseous materials.
Other modes of applying the principle of our
invention may be employed instead of the one
explained, change being made as regards the
means and the steps herein disclosed, provided
those stated by the following claim or its equiva
lent be employed.
We therefore particularly point out and dis
tinctly claim as our invention:
The methodfor producing unsaturated hydro
carbon gases which comprises passing hot com
bustion gases into contact with a pervious re
fractory mass to transfer heat to the same from
said gases, thereafter passing steam in contact
with the so-heated mass to absorb heat from
the same into the steam whereby superheated
steam at a. temperature above 1000° C. is ob
tained, injecting a heavy oil substantially in the
liquid phase into said superheated steam only in
such proportion that the temperature of the su
perheated steam remains above about '100° C. un
til the gaseous- reaction product is contacted
with a liquid quenching medium.
Без категории
Размер файла
808 Кб
Пожаловаться на содержимое документа