Patent Application
20160024398
The present invention is related to a process for gravitational upgrading and hydrogenation of heavy oil, extra heavy oil, bitumen and the like by increasing its API value, reduction of its viscosity and removal of part of the sulphur and heavy metals in the oil.
The following general introduction to catalytic cracking highlights present status and the outlined words and sentences focus on the difficulties/precautions which have to be met from case to case.
Catalytic cracker unit (FCCU) processes are widely utilized in the petroleum industry in the upgrading of oils. The ‘heart’ of such processes consists of a reactor vessel and a regenerator vessel interconnected to allow the transfer of spent catalyst from the reactor to the regenerator and of regenerated catalyst back to the reactor. The oil is cracked in the reactor section by exposing it to high temperatures and in contact with the catalyst. The heat for the oil cracking is supplied by the exothermic heat of reaction generated during the catalyst regeneration. This heat is transferred by the regenerated fluid catalyst stream itself. The oil streams (feed and recycle) are introduced into this hot catalyst stream en route to the reactor. Much of the cracking occurs in the dispersed catalyzed phase along this transfer line or riser.
The final contact with the catalyst bed in the reactor completes the cracking mechanism. The vaporized cracked oil from the reactor is suitably separated from entrained catalyst particles by cyclones and routed to the recovery section of the unit. Here it is fractionated by conventional means to meet the product stream requirements. The spent catalyst is routed from the reactor to the regenerator after separation from the entrained oil. Air is introduced into the regenerator and the fluid bed of the catalyst. The air reacts with the carbon coating on the catalyst to form CO/CO2. The hot and essentially carbon-free catalyst completes the cycle by its return to the reactor. The flue gas leaving the regenerator is rich in CO. This stream is often routed to a specially designed steam generator where the CO is converted to CO2 and the exothermic heat of reaction used for generating steam (the CO boiler). The principal difference between the present invention and this prior art, is that CO/CO2 is not routed to any external boiler, but plays a vital part in the present invention by production of hydrogen by the gas/water shift expressed by CO+H2=H2+CO2.
Feed stocks to the FCCU are primarily in the heavy vacuum gas oil range. Typical boiling ranges are 340° (10%) to 525° C. (90%). This allows feedstock with final boiling point up to 900 C. This gas oil is limited in end point by maximum tolerable metals, although the new zeolite catalysts have demonstrated higher metal tolerance than the older silica-alumina catalysts.
The principal difference between present invention and this option is that the present invention is not limited by its metal content as the process reduces the metal content in the order of 90%, forming metal sulphides. In addition the process does not require use of an advanced catalyst, but use fine grain minerals, such as inter alia silicon oxide and olivine as heat carrier.
The fluid catalytic cracker is usually a licensed facility. Correlations and methodology are therefore proprietary to the licensor although certain data are divulged to clients under the licensor agreement. Such data are required by clients for proper operation of the unit, and may not be divulged to third parties without the licensor's expressed permission.
These and other means, including operating instructions, are required for the proper operation of the units. Most of the proprietary data, however, concern the reactor/regenerator side of the process. The recovery side—that is, the equipment required to produce the product streams from the reactor effluent—utilizes essentially conventional techniques in their design and operating evaluation.
Up to the late 1980s feedstock to FCCU were limited by characteristics such as high Conradson carbon and metals. This excluded the processing of the ‘bottom of the barrel’ residues. Indeed, even the processing of vacuum gas oil feeds were limited to
During the late 1980s significant breakthroughs in research and development produced a catalytic process that could handle these heavy feeds and indeed some residues. Feed stocks heavier than vacuum gas oil when fed to a conventional FCCU tend to increase the production of coke and this in turn deactivates the catalyst. This is mainly the result of:
The present invention does not suffer from any of these drawbacks which will be highlighted later.
In the FCCU process conventional feedstock cracking temperature is controlled by the circulation of hot regen catalyst. With the heavier feedstock, with an increase in Conradson carbon there will be a more pronounced coke formation. This in turn produces a high regen catalyst temperature and heat load. To maintain heat balance, catalyst circulation is reduced, leading to poor or unsatisfactory performance. Catalyst cooling or feed cooling is used to overcome this high catalyst heat load and to maintain proper circulation.
In the present invention, the temperature of the energy carrier is controlled by internal cooling in the regenerator for steam production whereby a constant flow of heat carrier can be obtained.
The extended boiling range of the feed, as in the case of residues, tends to cause an uneven cracking severity. The lighter molecules in the feed are instantly vaporized on contact with the hot catalyst and cracking occurs. In the case of the heavier molecules vaporization is not achieved as easily. This contributes to a higher coke deposition with a higher rate of catalyst deactivation. Ideally, the whole feed should be instantly vaporized so that a uniform cracking mechanism can commence. The mix temperature (which is defined as the theoretical equilibrium temperature between the un-cracked vaporized feed and the regenerated catalyst) should be close to the feed dew point temperature. In conventional units this is about 20-30°C. above the riser outlet temperature. This can be approximated by the expression:
T
m
=T
R+0,1 ΔAHc
This mix temperature is also slightly dependent on the catalyst temperature.
Cracking severity is affected by polycyclic aromatics and nitrogen. This is due to the fact that these compounds tend to be absorbed into the catalyst. Raising the mix temperature by increasing the riser temperature reverses the absorption process. Unfortunately, a higher riser temperature leads to undesirable thermal cracking and production of dry gas.
The processing of heavy feedstock therefore requires special techniques to overcome:
Some of the techniques developed to meet heavy oil cracking processing are the following:
The present invention will show how this is solved and demonstrate that it is not needed to use two-stage regeneration.
An important issue in the case of heavy oil fluid catalytic cracking is the handling of the high coke deposition and the protection of the catalyst. One technique that limits the severe conditions in regeneration of the spent catalyst is a two-stage regenerator.
This differs from the present invention as we do not use classic catalysts with rare earth minerals but neutral minerals as heat carrier. In the description of the present invention the terms “catalyst” and “heat carrier” are used interchangeably.
The spent catalyst from the reactor is delivered to the first regenerator. Here the catalyst undergoes a mild oxidation with a limited amount of air. Temperatures in this regenerator remain fairly low, around 700-750° C. From this first regenerator the catalyst is pneumatically conveyed to a second one. Here excess air is used to complete the carbon burn-off and temperatures up to 900° C. are experienced. The regenerated catalyst leaves this second regenerator to return to the reactor via the riser. The technology that applies to the two-stage regeneration process is innovative in that it achieves the burning off of the high coke without impairing the catalyst activity. In the first stage the conditions encourage the combustion of most of the hydrogen associated with the coke. A significant amount of the carbon is also burned off under mild conditions. These conditions inhibit catalyst deactivation.
The present invention operates with a temperature of 800-900 C in the lower part of the regenerator and at 450-550 C in the upper part of the regenerator, which is below the temperature presented above.
It has been found that there is a specific temperature range for the energy carrier that is desirable for a given feed and catalyst system. A unique dense phase energy carrier cooling system provides a technique through which the best temperature and heat balance relationship can be maintained.
These features are a vital part of the present invention.
It is reported that 69% of the enthalpy contained in the heat input to the reactor is required just to heat and vaporize the feed. The remainder is essentially available for conversion. To improve conversion it would be very desirable to allow more of the available heat to be used for conversion. The only variable that in conventional FCCU's units can be changed to achieve this requirement is the feed inlet enthalpy, that is, through preheating the feed. Doing this, however, immediately reduces the catalyst circulation rate to maintain heat balance. This has an adverse effect on conversion. The preheating of the feed, however, is compensated for by cooling the energy carrier. Thus the circulation rate of the energy carrier can be retained and, in many cases, increased. Indeed, by careful manipulation of the heat balance, the net increase in energy carrier circulation rate can be as high as 1 unit cat/oil ratio. The higher equilibrium activity for the energy carrier possible at the lower regeneration temperature also improves the unit yield pattern.
This is an important feature of the present invention, preheating of the oil still allows a high flow of energy carrier and oil feed as the generated CO/CO2 and steam from the atomization of the oil, dramatically reduces the partial pressure of the oil whereby the oil behaves as being evaporated under high vacuum. In addition, the gravitational accelerated colliding jets of energy carriers induces mechanical shear forces which improves the cracking, i.e. allows more of the energy to be utilized in conversion.
In residue cracking commercial experience indicates that operations at regenerated catalyst temperatures above 900° C. result in poor yields, with high gas production due to local thermal cracking of the oil on contact. Where certain operations require high regen temperatures the installation of a catalyst cooler will have a substantial economic incentive. This will be due to improved yields and catalyst consumption.
This is also a feature of the present invention, as low partial pressure permits a low temperature of the energy carrier, which either can be controlled by an internal heat exchanger in the regenerator or by recirculation of flue gas after the downstream system (condensers).
The equilibrium temperature between the oil feed and the regenerated catalyst must be reached in the shortest possible time. This is required in order to ensure the rapid and homogeneous vaporization of the feed. To ensure this it is necessary to design and install a proper feed injection system. This system should ensure that any catalyst back-mixing is eliminated and that all the vaporized feed components are subject to the same cracking severity.
This is achieved in the present invention by the atomisation of the oil, the gravitationally colliding jets of heat carrier and remixing rings inside the oil cracker.
Efficient mixing of the feed finely atomized in small droplets is achieved by contact with a pre-accelerated dilute suspension of the regen catalyst. Under these conditions feed vaporization takes place almost instantaneously.
According to the present invention it is achieved that the low velocity of the energy carrier in the regenerator is accelerated by gravitational forces and reduced cross section area in two collision pipes by entrance into the oil cracker.
Another problem encountered in heavy oil cracking is the possibility that the heavier portion of the oil is below its dew point. To ensure that this problem is overcome, the mix temperature must be set above the dew point of the feed. The presence of polycyclic aromatics also affects cracking severity. Increasing the mix temperature to raise the riser temperature reverses the effect of polycyclic aromatics. In so doing, however, thermal cracking occurs, which is undesirable. To solve this problem it is necessary to be able to independently control the riser temperature relative to mix temperature.
This problem is overcome in the present invention by the low partial pressure of the oil and the fact that the oil cracker temperature is controlled by the injection rate of steam in the atomizing nozzles, which is independent of the feed whereby optional cracking conditions are obtained.
Mix temperature control (MTC) is achieved by injecting a suitable heavy-cycle oil stream into the riser above the oil feed injection point. This essentially separates the riser into two reaction zones. The first is between the feed injection and the cycle oil inlet. This zone is characterized by a high mix temperature, a high catalyst-to-oil ratio and a very short contact time.
This is avoided according to the present invention since the heat transfer, vaporization and cracking takes place instantaneously in the oil cracker and is completed by the entrance of the cyclone.
As described earlier, it is highly desirable to achieve good catalyst/oil mixing as early and as quickly as possible in the process. The method described to achieve this requires the pre-acceleration and dilution of the catalyst stream. Traditionally, steam is the medium used to maintain catalyst bed fluidity and movement in the riser. Steam, however, has a deleterious effect on the very hot catalyst that is met in residue cracking processes. Under these conditions steam causes hydrothermal deactivation of the catalyst.
This is overcome in the present invention by using the off gases from the regenerator (CO/CO2) as the main carrier of the energy carrier and that the heat carrier is injected at a positive angle into the oil cracker whereby the heat carrier flow is turned from an almost downward direction to an upward direction in the oil cracker.
Much work has been done in reducing the use of steam in contact with the hot catalyst. Some of the results of this work showed that if the partial pressure of steam is kept low, the hydrothermal effects are greatly reduced in the case of relatively metal free catalysts. A more important result of the work showed that light hydrocarbons impart favorable conditioning effects to the freshly regenerated catalyst. This was pronounced even in catalysts that were heavily contaminated with metals.
This one of the novel features of the present invention, namely that common mineral oxides may be used as energy carriers for oil with high metal and sulphur content. Furthermore, the use of the flue gas as heat carrier reduces the process temperature to an optimal temperature for hydrogen production by the gas/water shift.
Light hydrocarbon gases have been introduced in several heavy oil crackers since 1985. They have operated either with lift gas alone or mixed with steam. The limitations to the use of lift gas rests in the ability of downstream units to handle the additional gas.
This is also a novel feature of the present invention, namely that we can handle the non-condensable gases in the downstream system. By using the off gases from the regenerator itself to carry the energy carrier, it is also possible to utilize the calorimetric heat in the gas, which reduces the energy consumption.
The cracked products leaving the FCCU reactor represent a wide range of cuts. This reactor effluent is often referred to as a ‘syn’-crude because of its wide range of boiling point materials.
The ‘syn’-crude assay should comprise at least a TBP (True Boiling Point) curve with an analysis of light ends, gravity versus mid-boiling point curve and a PONA for the naphtha and sulphur content versus mid-boiling point for the ‘syn’-crude.
The present invention relates to a FCCU cracking unit which aims at reducing a number of the obstacles associated with existing FCCU-units and, more specifically, shows a FCCU-unit which can be built for small scale operation at a well site whereby heavy feedstock can be processed at the source. The advantage obtained is that feedstock with severe transport properties (pumping capability) can be converted into excellent transport conditions or be used as a diluent oil to be blended with the heavy crude. This kind of blending is used widely in for example Venezuela and Canada. A basic rule is that for every barrel of oil extracted from the reservoir, ¾ barrel of diluent oil is needed to blend the oil into good pumpable conditions.
Designated Collicitor, the technology makes use of the thermodynamic impact from oil droplets colliding with hot solid particles. The Collicitor technology is enclosed in a compact reactor/regenerator concept that inherently includes high-temperature steam generation. The concept relies upon high energy dissipation through the collision of 40 to 60 m/s hot solids jets at 100 to 200 kg/m3capable of breaking the viscous bridges at molecular level. The reaction enthalpy required for thermo-mechanical upgrading is provided from the regeneration of the solids, from which residual coke is burnt off. Hydrogenation is further supported by high-temperature steam instantly impacted with the local temperature peaks caused by colliding particles, thus, enhancing desired hot spot reactions.
The solids to be used are naturally occurring mineral particles. Olivine is used as reference material owing to its tar cracking benefits. Furthermore, the Collicitor process is considered complementary to common extraction techniques because it (also) provides a part of the auxiliary steam required. In current operations, steam is usually generated from natural gas, representing additional cost and environmental impacts.
By using light diluent oil which may have a market price of $ 25-30 per barrel, the value of the oil is reduced to about $15 per barrel and thus a technology where one can produce diluent oil of heavy crude, will have a substantial economical potential.
The present process comprises the following main component:
1. A vertical regenerator with
a) An internal heat exchanger for steam production and
b) Discharge port for spent bed.
c) Fluidization nozzle.
d) Air intakes pipes.
e) Start up burner.
f) Fuel injection line.
Port for makeup of fresh heat carriers.
2. Two down wards pointing collision
3. An vertical oil cracker with
a) Internal remixing rings.
b) Oil atomization nozzle.
c) Port for re-circulating heat carrier.
4. Hopper for heat carrier make up
5. A transfer duct from the oil cracker to a cyclone.
6. A down comer from the cyclone to a loop seal having two exits.
7. A transfer line to a condensing/distillation system.
8. A gas circulation system.
9. A preheating system for the feed.
Below the process will be described in detail by reference to the enclosed drawings, wherein:
Referring to
When the system has reached its operating temperature with a temperature of the heat carrier and combustion gasses of 400 to 600 C at the lower part of the collision pipes 8), pre heated oil from the tank 17) is pumped to the atomization nozzle 10) where the oil is atomized by steam injected into the nozzle 10).
In the cracker, the oil droplets will meet the two colliding and accelerated streams of heat carrier and combustion gasses and become energized by thermal energy from the heat carrier and combustion gasses and extreme mechanical shear forces from the colliding heat carrier and change of momentums by the change of flow direction. In addition to mechanical shear forces from the colliding heat carrier, the colliding particles will give rise semi plastic impacts creating countless hotspots. The total effect of the heat carrier and combustion gasses heats, evaporates and crack the oil.
The combustion gasses which in addition to nitrogen, consists of CO and CO2 will react with the steam from the atomization nozzle and for hydrogen according to CO+H2=H2+CO2. In order to optimize the cracking and absorption of hydrogen into the oil, the internal of the oil cracker 9) is lined with stepwise recirculation elements which generates turbulence and cavitations in the stream which now consists of HC-gas, steam and CO2 and NOx.
As the cracking process disposes of carbon on the heat carrier, the fuel oil injection into the regenerator 1) is gradual reduced whereby excess air from the compressor 2) combusts the associated coke on the heat carrier. The combustion temperature is in the range between 800 and 900 C whereas the target temperature at the lower part of the collision pipes 8) is in the range of 400-600 C, the excess heat in the regenerator 1) is reduced by cooling either with a heat exchanger 23) producing either hot water or steam or with recycling flue gas from a gas blower 21) or a combination of the same.
In the cracking process, sulphur is removed from the oil as elementary sulphur and disposed of on the heat carrier together with portion of the heavy metals in the oil.
When the heat carrier is destroyed, spent bed is discharged via a cone valve 5) and into a spent bed cooler 7) where the temperature is reduced from regenerator temperature to about 125 C. The spent bed is replaced by fresh heat carrier from the hopper 12).
The produced oil is extracted from the condensation or distillation system in a conventional manner.
Because of the low partial pressure of the oil in the exhaust gases, it is possible to run the process at a temperature as low as 450 C.
To have the hydrodynamics of the technology tested, a cold experimental screening tool in plastic was built as shown in the
In order to balance the heat distribution between the regenerator and the oil cracker, a portion of the heat carrier can be diverted over the loop seal 16) at a reduced temperature to the oil cracker where it will blend with the stream from the collision pipes 8) thus giving the target temperature of the inflow up the oil cracker given by:
Q=m
s
*c
s
*t
1
+m
g
*c
g
*t
1=(ms+mrs)*cs*t2+mg*cg*t2 kJ
Where:
ms=heat carrier from the regenerator, kg/h
cs=specific heat for heat carrier, kJ/kgC
t1=temperature in the collision pipes, C
mg=combustion gasses from regenerator, kg
cg=specific heat of combustion gasses, kJ/kgC
mrs=re-circulated heat carrier into oil cracker, kg/hr
t2=target temperature in the bottom of the oil cracker, C
This allow us to fine tune the optimal cracking conditions in the oil cracker and maintaining the mass flow of heat carrier.
A further positive effect of the process is that the re-mixing elements reduce the risk for uncontrolled back mixing and cracking in the cyclone which is observed and controlled by the ext temperature at the inlet to the cyclone. The suppression of over cracking is furthermore suppressed by the fluidization stream of steam in the down comer 15) of the cyclone where the steam molecules together with the non condensable gasses dilute the oil gas flow preventing the oil molecules in re-polymerization.
In the oil cracker, the energy consumption of the heavy oil can be expressed as:
Q=m
o*(co*tp+ro)=kJ/hr
Where:
mo=injected oil, kg/hr
co=specific heat of heavy oil ranging from 2-4 kJ/kgC
tp=process temperature C
ro=heat of evaporation of oil kJ/kg ranging from 200-400 kJ/kg
C=heat of cracking ranging from 500 to 2000 kJ/kg
Note: the cp is an average specific heat for all fractions in the oil and r0=is an average heat of evaporation.
| Number | Date | Country | Kind |
|---|---|---|---|
| MX/A/2013/002908 | Mar 2013 | MX | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2014/054959 | 3/13/2014 | WO | 00 |
