Patent GB-644299-A (GB)
Title: Improvements in or relating to method of cracking hydrocarbons
IPC: C10G9/36
Filed: 1946-11-19
Abstract: <PICT:0644299/IV (b)/1> In a process mainly directed to the production of olefines such as ethylene and acetylene, gaseous hydrocarbons such as ethane or propane, or atomized liquid hydrocarbons such as crude oils are injected into a stream of steam within an externally-heated chrome-nickel alloy cracking tube.  The liquid hydrocarbons may be atomized before the injection by admixture with steam or a gas under pressure such as hydrogen, nitrogen or combustion gases or, when steam is used in atomization, the steam within the cracking tube may be replaced by such a gas.  Oil is delivered by pump 1, Fig. 1, through preheater 2 to mixer 4 where it is atomized and partly vaporized by primary steam through valve 5. The mixture passes down injection tube 6 and issues through openings 9 into a chrome nickel steel alloy cracking tube 7 which is heated by furnace 10 and contains a tubular space reducer 13.  Secondary steam is introduced to the reaction tube by conduit 11 to meet the atomized oil at 8, a small portion being also fed into space reducer 13 to keep it clear of oil vapours.  Products withdrawn through exit 14 are quenched by liquid hydrocarbons or by water and separated by fractional distillation or absorption.  In a modification, Fig. 2, the space between the injection tube and the cracking tube is packed, a portion of the steam being fed through line 22 into the annular space between the injection tube and the packing so as to travel counter to the flow of atomized oil within the tube.  The temperature of the oil or gas issuing from openings 9 is between 250 DEG  F. and 800 DEG  F., preferably 600 DEG  F. to 650 DEG  F. and that of the secondary steam at this point about 100 DEG  F. to 1600 DEG  F., the temperature of the cracking tube in this zone being about 1500 DEG F. to 1900 DEG  F.  The flow of the reactants is adjusted to give a reaction time of about 0.1 to 5 seconds, preferably 0.1 to 1 second. The proportions by weight of hydrocarbon and total steam are between 1 to 0.1 and 1 to 5, preferably between 1 to 1 and 1 to 3.  Such factors as the temperature gradients in the furnace and the turbulence and velocity of the gas streams are varied as by omitting the spacer tube and, if desired, filling the space with packing material and by using fins, deflectors and the like, in accordance with the type of hydrocarbon treated and the product desired, and cracking may be total or partial, in which event the uncracked portion may be recycled for mixture with the feed stock.  The process is usually performed at atmospheric pressure, although sub-atmospheric pressures or super-atmospheric pressures, for example 25 to 100 lbs. sq. inch may be employed. The hydrocarbon may be in emulsion form or may contain catalysts such as alkali metal, phosphorous boron and antimony compounds or anti-carbon forming materials such as borates.  As well as gaseous olefines such as ethylene and acetylene, the products may include butadiene, isoprene, styrene, indene, naphthalene and resinous materials.  Tabular results of tests on fuel oil, deasphalted residual oil and Texas crude oil are given in which 41 to 61.7 per cent of olefines is produced when from 47 to 73 per cent of the feed is cracked.ALSO:<PICT:0644299/III/1> In a process mainly directed to the production of olefines such as ethylene and acetylene, gaseous hydrocarbons such as ethane or propane, or atomized liquid hydrocarbons such as crude oils, are injected into a stream of steam within an externally-heated chrome-nickel alloy cracking tube.  The liquid hydrocarbons may be atomized before the injection by admixture with steam or a gas under pressure such as hydrogen, nitrogen or combustion gases or, when steam is used in atomization, the steam within the cracking tube may be replaced by such a gas.  Oil is delivered by pump 1, Fig. 1, through preheater 2 to mixer 4 where it is atomized and partly vaporized by primary steam through valve 5. The mixture passes down injection tube 6 and issues through openings 9 into a chrome nickel steel alloy cracking tube 7 which is heated by p  furnace 10 and contains a tubular space reducer 13.  Secondary steam is introduced to the reaction tube by conduit 11 to meet the atomized oil at 8, a small portion being also fed into space reducer 13 to keep it clear of oil vapours.  Products withdrawn through exit 14 are quenched by liquid hydrocarbons or by water and separated by fractional distillation or absorption.  In a modification, Fig. 2, the space between the injection tube and the cracking tube is packed, a portion of the steam being fed through line 22 into the annular space between the injection tube and the packing so as to travel counter to the flow of atomized oil within the tube.  The temperature of the oil or gas issuing from openings 9 is between 250 DEG  and 800 DEG  F., preferably 600 DEG  to 650 DEG  F. and that of the secondary steam at this point about 1000 DEG  to 1600 DEG  F., the temperature of the cracking tube in this zone being about 1500 DEG  to 1900 DEG F.  The flow of the reactants is adjusted to give a reaction time of about 0.1 to 5 seconds, preferably 0.1 to 1 second.  The proportions by weight of hydrocarbon and total steam are between 1 to 0.1 and 1 to 5, preferably between 1 to 1 and 1 to 3.  Such factors as the temperature gradients in the furnace and the turbulence and velocity of the gas streams are varied as by omitting the spacer tube and, if desired, filling the space with packing material and by using fins, deflectors and the like, in accordance with the type of hydrocarbon treated and the product desired, and cracking may be total or partial, in which event the uncracked portion may be recycled for mixture with the feed stock. The process is usually performed at atmospheric pressure, although sub-atmospheric pressures or super-atmospheric pressures, for example 25 to 100 lbs. sq. inch may be employed.  The hydrocarbon may be in emulsion form or may contain catalysts such as alkali metal, phosphorus, boron and antimony compounds or anti-carbon forming materials such as borates.  As well as gaseous olefines such as ethylene and acetylene, the products may include butadiene, isoprene, styrene, indene, naphthalene and resinous materials.  Tabular results of tests on fuel oil, de-asphalted residual oil and Texas crude oil are given in which 41 to 61.7 per cent of olefines is produced when from 47 to 73 per cent of the feed is cracked.