US3619416A

US3619416A - Dehydration of bituminous emulsion

Info

Publication number: US3619416A
Application number: US764188A
Authority: US
Inventors: Robert D Hendry
Original assignee: Canada Cities Service Ltd; Imperial Oil Ltd; Royalite Oil Co Ltd; Atlantic Richfield Co
Current assignee: Petro Canada Exploration Inc; Gulf Canada Ltd; Canada Cities Service Ltd; Imperial Oil Ltd; Royalite Oil Co Ltd
Priority date: 1968-10-01
Filing date: 1968-10-01
Publication date: 1971-11-09
Anticipated expiration: 1988-11-09

Abstract

A process for the thermal dehydration of a bituminous emulsion with heat from exhaust steam while simultaneously condensing the exhaust steam is disclosed herein. The process comprises heating a stream of bituminous emulsion by heat transfer from partially cooled steam turbine exhaust steam, to vaporize low boiling materials, principally water, and condense the steam, separating the vapor from the bituminous emulsion to partially dehydrate the emulsion, heating the partially dehydrated emulsion to a higher temperature by heat transfer from the exhaust steam of the steam turbine to vaporize the remaining water, and separating the water vapors from the bituminous stream. Preferably the turbine exhaust steam is first reheated and utilized to heat the fully dehydrated bitumen emulsion prior to subjecting the bitumen to solid-liquid separation by cycloning.

Description

United States Patent Inventor Robert D. Hendry Edmonton, Alberta, Canada Appl. No. 764,188

Filed Oct. 1, 1968 Patented Nov. 9, 1971 Assignees Canada-Cities Service, Ltd.

Calgary, Alberta, Canada;

Imperial Oil Limited; Atlantic Richtield Corporation; Royalite Oil Company Limited, part interest to each DEIIYDRATION 0F BITUMINOUS EMULSION 3 Claims, 1 Drawing Fig.

US. Cl 208/187 Int. Cl C10g 33/00 Field of Search 208/187, 188, 177

References Cited UNITED STATES PATENTS 1,983,832 12/1934 Bailey 208/187 EMULSION Assistant Examiner-G. J. Crasanakis Attorney-J Richard Geaman ABSTRACT: A process for the thermal dehydration of a bituminous emulsion with heat from exhaust steam while simultaneously condensing the exhaust steam is disclosed herein. The process comprises heating a stream of bituminous emulsion by heat transfer from partially cooled steam turbine exhaust steam, to vaporize low boiling materials, principally water, and condense the steam, separating the vapor from the bituminous emulsion to partially dehydrate the emulsion, heating the partially dehydrated emulsion to a higher temperature by heat transfer from the exhaust steam of the steam turbine to vaporize the remaining water, and separating the water vapors from the bituminous stream. Preferably the turbine exhaust steam is first reheated and utilized to heat the fully dehydrated bitumen emulsion prior to subjecting the bitumen to solid-liquid separation by cycloning.

SOLIDS DEIIYDRATION OF BITUMINOUS EMULSION This invention relates to an improved process for the removal of water contained in a bituminous emulsion. More particularly, this invention relates to a process for efficiently utilizing the latent heat of exhaust steam from a turbine to dehydrate and upgrade a bituminous froth or emulsion concurrently with the effrcient operation of a steam turbine power plant.

The invention disclosed herein is concerned with the efficient production of synthetic petroleum oil and other petroleum derivatives from a source such as shale oils or more preferably tar sands. The tar sands are a particularly desirable source of petroleum derivatives because extensive deposits are found on the North American Continent, principally in the Athabasca District of the Province of Alberta in Canada.

Typically, these sands contain about 6 percent to about 20 percent of a hydrocarbon material called bitumen (also referred to herein as oil), from about 1 percent to about 10 percent water, and from about 70 percent to about 90 percent of various mineral solids. The specific gravity of bitumen varies from about 1.0 to about 1.05 and the bitumen has an API gravity of about 8.0 (at 60 F The major portion, by weight, of the mineral solids in the bituminous sand is quartz sand having particle size varying generally between about 45 microns and 2,000 microns. Various other mineral inclusions are also found in the bituminous sand such as clay and silt fines of a particle size below about 45 microns.

Several methods are known or have been proposed for separating the oil from the bituminous sand. Some of these methods involve the use of water for preparing an aqueous slurry of the tar sand at a temperature above 75 F., in order to encourage dispersion and separation of the mineral solids from the bitumen. Most of the quartz sand and portions of the tines are separated from the slurry by various mechanical means, principally flotation separation of the bitumen as an emulsion. The bituminous emulsion or froth which is recovered from the primary separation contains some tine sand particles and a small quantity of coarse sand. Typically, the bituminous emulsion contains from about 10 percent to 60percent water, percent to 20 percent minerals mostly fines, from about 30 percent to 85 percent bitumen, and is subsequently subjected to various mechanical dewatering operations such as mechanical agitation to coalesce the water, and roller dewatering in order to reduce the water content to a minimum.

However, it is generally necessary to reduce the water content of the bitumen to as small an amount as possible, before subjecting the bitumen to various petroleum processing steps. Generally, it is therefore preferred to substantially fully dehydrate the bituminous emulsion and thereby substantially reduce water content of the oil product.

I have invented a method for recovering bitumen from bituminous emulsion of the type described above. More particularly the process contemplates integration of a steam power generation'process with thermal dehydration of a bituminous emulsion in the production of a synthetic crude oil. The latent heat of the exhaust steam from the steam turbine provides heat for the thermal dehydration of the bituminous emulsion, while simultaneously acting to condense the exhaust steam. The process therefore comprises heating a stream of bituminous emulsion with the latent heat from exhaust steam to vaporize water and low boiling material contained in the emulsion, while simultaneously condensing the exhaust steam, and separating the vaporized water from the bituminous emulsion. The process additionally comprises further heating the separated bituminous emulsion by heat transfer from the exhaust steam to vaporize essentially all the remaining water in the bituminous emulsion, separating the vaporized water from the bitumen stream, and returning the condensed water from the exhaust steam to the steam power plant.

It is therefore an object of this invention to provide an improved process for the thermal dehydration of bituminous emulsion.

Another object of this invention is to provide an effcient process for both the thermal dehydration of bituminous material, and the efiicient production of energy.

Still another object of this invention is to provide an integrated process for the heating and dehydration of the bituminous emulsion while simultaneously condensing the exhaust steam from a steam turbine power plant, and returning the condensate to the power plant.

Other objects and advantages of the process of this invention will become apparent to those skilled in the art from the description of the drawings and preferred embodiments which follow.

The drawing shows in schematic form the process of this invention.

More particularly, the drawing shows a stream of bituminous emulsion from a primary separation vessel (not shown) being fed into a retention tank 12 where the emulsion is retained for a period of time generally between 1 and 10 days so as to allow some of the water contained in the emulsion to coalesce. The stored emulsion is then passed over a series of mechanical dewatering rollers 14 which act to remove a fraction of the water contained in the emulsion by allowing the bituminous emulsion to adhere to the surface of the rollers and be removed by the doctor blades 'or similar means while coalesced water not adhering to'the rollers is drained away from the rollers. The rollers dewatered bituminous emulsion which contains from about'20 to '30 percent water is next subjected to thermal dehydration. The use of roller dewatering serves to provide effective means for reducing the water con-. tent of the bituminous emulsion to a relatively constant level so as to provide a relatively uniform stream of bituminous emulsion as feed for thermal dehydration.

The bituminous emulsion feed after being dewatering is preferably heated to -200 F.) in a storage tank 16 and passed via a bituminous feed pipe 18 and feed pump 20 to a predehydration'heat exchanger 22. The feed pump raises the pressure of the preheated'bituminousemulsion to about 30 p.s.i.g. prior to entering the predehydration heat exchanger 22. In the predehydration heat exchanger 22, the temperature of the bituminous emulsion stream is raised by heat transfer from the heating fluid to a temperature at which water contained in the emulsion stream (at' the raised pressure) will vaporize. Where a stream pressure of about 50 p.s.i.g. is maintained, it is preferred that the bituminous emulsion temperature be raised in the predehydration heat exchanger to a temperature of about 275 F. The stream of heated emulsion from the predehydration heat exchanger 22 is then passed to a first dehydration vessel 24 where the vaporized material is separated from the bituminous emulsion stream. A major portion of the vaporized material, principally water, but also including low boiling hydrocarbon material, is removed from the first dehydration vessel 24 via an effluent venting conduit 26 and passed to a contact condenser 28 where it is condensed by mixing it with cooling water from a source not shown. The mixture of cooling water and the condensate is then passed to oil-water separator 30 where light gas-oil is separated therefrom.

The partially dehydrated bitumen stream from the first dehydration vessel 24 is passed via conduit 32 to an interdehydration heat exchanger 34 where the bituminous emulsion is heated as hereinafter described to a higher temperature. .The temperature to which the bituminous emulsion is heated in the interdehydration heat exchanger 34 is deter mined by the maximum temperature at which the heating fluid is supplied to the interdehydration heat exchange and by the economics of the integrated power plant and thermal dehydration process. Basically, the temperature to which the partially dehydrated bituminous emulsion is raised in the interdehydration heat exchanger is limited by the available temperature of the heating fluid, that is the exhaust steam. The heating of the bituminous emulsion stream in the interdehydration heat exchanger substantially vaporizes all the remaining water in the emulsion including some hydrocarbon material.

The heated bituminous emulsion stream is then passed to a second dehydration vessel 36. The second dehydration vessel 36 is maintained at a similar pressure to that of the first dehydration vessel allowing for any pipe resistance losses and process losses. Material boiling below that pressure and temperature are therefore in the vapor phase in the second dehydration vessel and are efi'ectively separated from the steam of liquid bituminous material. The vaporized material is passed from vessel 36 via a conduit 38 to the contact condenser 28 where it is treated as hereinbefore described. The second dehydration step in the vessel 36 serves to remove most of the remaining water present in the bitumen stream.

The fully dehydrated bitumen stream from the second dehydration vessel 36 is then passed through a pump 40 to a postdehydration heat exchanger 42 preparatory to processing the bitumen stream for the removal of solids and the separation of gas oil and naphtha.

The fully dehydrated bitumen stream is heated to a higher temperature in order to reduce its viscosity prior to removing solids by cycloning. The pressure and the temperature of the fluid during cycloning determine somewhat the amount of solids which will be removed from the stream. Accordingly, it is desirable to reduce the viscosity since this does in fact increase the recovery or removal of solids from the stream. Therefore, the dehydrated bitumen stream is heated to about 575 F., in the postdehydration heat exchanger 42 and passed through a surge tank 44 where hydrocarbon material boiling below 575 F. at the particular pressure i.e. 50 p.s.i.g. is vented off. The remaining high boiling hydrocarbon material is then passed through a series of cyclone separators 46, one of which is shown and which functions as described in U.S. Pat. No. 3,383,814 issued on Aug. 29, 1967 to R. A. Given et al. disclosing a process for separating oil from bituminous sand.

Heat for dehydrating the bituminous stream and for preparing the dehydrated bitumen stream for cycloning is obtained by utilizing the latent heat available in the exhaust steam turbine 60 operated as part of an electrical power generating plant (not shown). The power plant is necessary to provide electrical power for the operation of the complete tar sand processing facility. Ordinarily the power plant process would be substantially complete cycle of operations in itself, receiving fuel and cooling water as outside inputs and generating electrical power and possibly steam for use elsewhere. Except for steam generated for use elsewhere for heating purposes, the exhaust steam from the turbine would ordinarily be condensed utilizing available coolants, preferably river or lake water, before being recycled to the steam boilers for reheating to high temperature, high pressure steam. Feed water which is satisfactory for conversion to and use as steam in a steam turbine must meet stringent purity and chemical standards and therefore it is incumbent upon those designing and operating a steam power plant that feedwater loss be maintained at a minimum. Finally, to achieve an efficient use of the steam turbine, the back pressure of the steam turbine condenser must be kept at a minimum in order to reduce the temperature at which the steam would cease to be superheated and become wet. The above described parameters contribute to the difficulty of utilizing the steam generated in the operation of the power plant for any major use other than powering the steam turbine.

More particularly the drawing shows the steam turbine 60, preferably a conventional back pressure steam turbine, receiv ing high temperature and high pressure steam from a steam generator such as a boiler 64, and exhausting spent steam at above atmospheric pressure and relatively high temperature (i.e. a temperature above the boiling point of water at that exhaust pressure) to an exhaust conduit 66 and back to the boiler 64 where the exhaust steam is reheated to somewhat a higher temperature. The steam turbine 60 is operated without a condenser at its exhaust end, resulting in exhaust steam which is dry at exhaust pressure. While the exhaust steam may if desired be used solely for the dehydration of the bituminous emulsion, it is particularly preferred that the steam also be utilized to heat the dehydrated bitumen stream for further processing as described above. The exhaust steam from the turbine 60 is passed through the exhaust conduit 66 to a reheater 68 mounted in the boiler 64 by opening a reheat valve 70 mounted in the exhaust conduit 66. A connecting valve 72 is mounted in a connecting conduit 74 which connects the exhaust conduit 66 directly to a main steam line 76. The main steam supply line 76 is connected at one end to the high temperature side of the reheater 68 and at the other end of the postdehydration heat exchanger 42. A valve 78 is mounted in the main steam supply line 76 between the reheater 68 and the junction between the connecting conduit 74 and the main steam supply line 76 between the reheater 68 and the junction between the connecting conduit 74 and the main steam supply line 76. By opening

valves

70 and 78 and closing connecting valve 72, reheated exhaust steam is supplied to the dehydration process via the main supply line 76. Alternatively exhaust steam directly from the steam turbine is supplied to the process by closing

closing valves

70 and 78 and opening valve 72.

Reheated exhaust steam is supplied to the postdehydration heat exchanger 42, where it serves to raise the temperature of the fully dehydrated bitumen stream to that necessary for effective subsequent processing such as cycloning.

The heating fluid, that is the steam leaving the postdehydration heat exchanger 42, is passed to the interdehydration heat exchanger 34 via conduit 82. The steam entering the interdehydration heat exchanger 34 is preferably at sufficiently high temperature to transfer enough heat (B.t.u./lb.) to raise the temperature of the bituminous emulsion steam passing through the interdehydration exchanger to about 350 F. Alternatively, steam may be sup lied to the interdehydration heat exchanger 34 directly from the main supply line 76 rather than from the postdehydration heat exchanger 42. For this purpose a bypass conduit 80 is directly connected between the steam supply line 76 and conduit 82 which carries the steam from the postdehydration heat exchanger 42 to the interdehydration heat exchanger 34. Suitable valves are located in the bypass conduit and the steam lines to and from the postdehydration heat exchanger. Valve 83 is mounted in the bypass conduit 80 and when open allows steam to pass directly to the interdehydration heat exchanger from the main steam supply line 76. Valves and 84 are mounted respectively in the steam piping to and from the postdehydration heat exchanger, valve 84 being mounted in conduit 82, and valve 85 in the main steam supply line 76 between conduit 80 and the postdehydration heat exchanger.

The exhaust steam after passing through the interdehydration heat exchanger 34 is passed to the predehydration heat exchanger 22 where heat from the exhaust steam is initially transferred to the bituminous emulsion stream. The bituminous emulsion stream as it passes through the predehydration heat exchanger 22 is heated to at most the temperature of the heating fluid stream leaving the interdehydration heat exchanger 34. The utilization of the predehydration heat exchanger 22 and the first dehydration vessel allows a significant portion of the water and low boiling hydrocarbon material to be vaporized and separated from the bituminous emulsion stream before having to. raise the temperature of the partially dehydrated emulsion stream in order to vaporize the remaining water. This accounts for a significant saving in heat energy for the process, since it is not necessary to heat the water and low boiling material previously removed in the first dehydration vessel.

Finally, the exhaust steam from the predehydration heat exchanger 22 is passed to a trim exchanger 86 where partially treated water is heated by heat transfer from the exhaust steam and converted to low temperature steam at about 50 p.s.i.g. for subsequent use in various extraction process requirements such as heating the tar sand slurry during extraction and separation. Since this water is not used as feed for the power plant, it need not be purified to the extent necessary for power plant feed water. The condensed exhaust steam or rather more explicitly the condensate from the trim exchanger 86 is returned via condensate feed conduit 88 back to the boiler 64 for use as feedwater.

While the invention has been described with reference to one of the preferred embodiments, another embodiment also contemplated as part of the invention, and utilizing thesystem described above is as follows. The exhaust. steam is.passed directly from the turbine 60 to the interdehydration heat exchanger 34. For this particular type operation, the

valves

70 and 78 are closed, valves 72 and 83 are opened, and the valves 84' and 85 leading to and from the postdehydrationheat exchanger 42 are closed. Exhaust steam is thereby exhausted directly from the turbine 60 to the interdehydration heat exchanger 34 without reheating. The exhaust steam is subsequently" utilized in the same manner as hereinbefore described to act as a heating fluid for dehydrating the bitumen stream according to'the present invention.

With a view of illustrating the. present invention but not as a limitation thereon, the following examples are given.

EXAMPLE I 990 lbs/hr. of a bituminous emulsion stream containing by weight about 71% oil, about 23% of .water, and about 6% solids are preheated to about 150 F. and pumped at a pressure of about 30 p.s.i.g. to the predehydration heat exchanger 22. Likewise 730 lbs. per hour "of steam at a pressure of 100 p.s.i.g, and a temperature of 460 F. is exhausted from the turbine' 12. The exhaust steam therefore has an enthalpy (h) of about 126 B.t.u./lb. The exhaust steam is passed to the steam reheater 68, reheated to a temperature of about 710 F., thereby increasing in enthalpy to about 1375 B.t.u./lbs. The process is operated as described above and the energy transfer between the bituminous stream and the exhaust steam is as follows.

POSTDEHYDRATION HEAT EXCHANGER 42 Heat Transferred-83,500 B.t.u./hr.

SteamtHeating Fluid) Bituminous Emullion Man 730 lbsJhr. 745 lblJhr. *Temp. (T) in 7l0' F. 350' F. Temp. (T) out 465' F. 575' F. Preuure l00 p.l.i. 50 p.|.i.g. it out I259 B.t.u./lbs.

INTERDEHYDRATION HEAT EXCHANGER 34 Heat Transferred-48,900 B.t.u./hr.

Stclmtfleating Fluid) Bltuminoul Emulsion Thus a total of about 240 B.t.u. per lbs. is extracted from the reheated exhaust steam and utilized in upgrading and dehydrating bituminous emulsion stream. This represents a utilization of about 7kilowatt hour (kw. hr.) per lbs. of exhaust steam.

EXAMPLE u The same fiow rates of 'steamand the bituminous emulsion streams were processed according to the present invention, however, the exhaust steam was neither reheated nor passed 1 directly to the postdehydration heat exchanger. Rather, the

exhaust steam was passed directly to the interdehydration exchanger 34. As such the details given in example I for the interdehydration and predehydration heat exchangers are appressure condenser. Furthermore, the process according to either examples I or ll effectively reduced the water content of the bituminous stream from about 23%to below one tenth of one percent.

Accordingly having described the invention and wishing to cover those'modifications and advantages which would be apparent to those skilled in the art without departing from the spirit and scope of the invention,

I claim:

1. A process for dehydrating a bituminous emulsion utilizing exhaust steam, said exhaust steam being at a temperature of about 460 F. and a pressure of about p.s.i., said process comprising first cooling said exhaust steam by indirect heat transfer in a second'heat transfer zone to a partially dehydrated bituminous emulsion stream, said indirect heat transfer indirectlyzheating said partiallydehydrated emulsion to a temperature of about 3'50 F., thereby substantially vaporizing any remaining water in said partially dehydrated emulsion,

separating said vaporized water from said heated partially dehydrated bituminous stream, thereby obtaining a dehydrated bituminous stream and a cooled exhaust steam, further cooling said cooled exhaust steam by'indirect heat transfer to .said bituminous emulsion in a first heat transferzone, said cooled exhaust steam thereby first indirectly heating said bituminous emulsion in said first heat transfer zone to a temperature sufficient topartially vaporize water from said first heated emulsion, and

separating said partially vaporized water from said first heated emulsion thereby obtaining said first partially dehydrated bituminous emulsion stream.

2. A process for dehydrating a bituminous emulsion'utilizing exhaust steam, said exhaust steam'being at a temperature of about 460 F. and a pressure of about l00 p.s.i., said process comprising first cooling said exhaust steam by indirect heat transfer in a secondheat transfer zone to a partially dehydrated bituminous emulsion stream, said indirect heat transfer indirectly heating said partially dehydrated emulsion to a temperature of about 350 F., thereby substantially vaporizing any remaining water in said partially dehydrated emulsion,

separating said vaporized water from said heated partially dehydrated bituminous stream, thereby obtaining a dehydrated bituminous stream and a cooled exhaust steam,

further cooling said cooled exhaust steam by indirect heat transfer to said bituminous emulsion in a first heat transfer zone, said cooled exhaust steam thereby first indirectly heating said bituminous emulsion in said first heat transfer zone to a temperature of about 275 F. to

exhaust temperature,

further heating said dehydrated bituminous stream by indirectly transferring heat from said reheated exhaust steam in a third heat transfer zone to the dehydrated bituminous stream, and

cycloning the heated, dehydrated bituminous stream,

thereby removing solids therefrom.

Claims

2. A process for dehydrating a bituminous emulsion utilizing exhaust steam, said exhaust steam being at a temperature of about 460* F. and a pressure of about 100 p.s.i., said process comprising first cooling said exhaust steam by indirect heat transfer in a second heat transfer zone to a partially dehydrated bituminous emulsion stream, said indirect heat transfer indirectly heating said partially dehydrated emulsion to a temperature of about 350* F., thereby substantially vaporizing any remaining water in said partially dehydrated emulsion, separating said vaporized water from said heated partially dehydrated bituminous stream, thereby obtaining a dehydrated bituminous stream and a cooled exhaust steam, further cooling said cooled exhaust steam by indirect heat transfer to said bituminous emulsion in a first heat transfer zone, said cooled exhaust steam thereby first indirectly heating said bituminous emulsion in said first heat transfer zone to a temperature of about 275* F. to partially vaporize water from said first heated emulsion, and separating said partially vaporized water from said first heated emulsion thereby obtaining said first partially dehydrated bituminous emulsion stream.
3. The process of claim 1 in which the bituminous emulsion contains solids, and which additionally comprises first reheating the exhaust steam to a temperature above the exhaust temperature, further heating said dehydrated bituminous stream by indirectly transferring heat from said reheated exhaust steam in a third heat transfer zone to the dehydrated bituminous stream, and cycloning the heated, dehydrated bituminous stream, thereby removing solids therefrom.