FR2523997A1 - Reducing the Conradson carbon and metals content of heavy oils - by mild cracking in riser reactor - Google Patents

Abstract

Selective vaporisation process for reducing the Conradson carbon (CC) and metals content of heavy petroleum fractions comprises contacting the feed and inert gas with a finely divided inert solid material in a riser reactor under mild cracking conditions, including a high temp. and a short hydrocarbon residence time. The vapour-phase prods. are sepd. from the solids and are cooled to a temp. below that at which significant thermal cracking occurs. The solids are contacted with an oxidising gas to burn off coke deposits and heat the catalysts (sic) to high temp., whereupon the heated solids are returned to the lower part of the riser. The improvement comprises introducing the inert gas into the lower part of the riser and injecting the feed into the riser at a point situated in or above the lower part. The process is esp. useful for producing FCC feedstocks from petroleum residua. Injection of the inert gas as above provides provides greater flexibility in the feed injection rate and/or in the control of the residence time in the riser.

Description

 Method and apparatus for selective vaporization.

 The invention relates to a selective spraying method and apparatus. More particularly, it aims to increase the fraction of heavy crude oils which can be used as catalytic cracking feedstock for the manufacture of high quality petroleum products, particularly automobile gasoline with a high octane number or fuel oil. high quality heavy.

The heavy tails of many crudes are rich in carbonaceous Conradson (sometimes called carbon
Ramsbottom) and metals that are undesirable in catalytic cracked raw materials and in products such as heavy fuel oil. The invention provides an economically advantageous process for selectively eliminating and using these undesirable constituents contained in whole crudes and in atmospheric and vacuum distillation residues, commonly called atmospheric residues and vacuum residues. Terms such as "residues" and the like will be used here in a slightly broader sense than usual, extending to any fraction of petroleum which remains after fractional distillation aimed at removing certain more volatile constituents In this sense, the headless crude which remains after distillation of petrol and lighter bodies is a residue. The unwanted CC (Conradson carbon) and the metal compounds in the crude tend to concentrate in the tailings because most of them are not very volatile. The terms "Conradson1 carbon and" Ramsbottom carbon "refer to the two most commonly used assay methods for this undesirable constituent.

The two methods may show some difference in numerical value for the same sample, but generally the results of either indicate the same characteristic.

 The invention provides an improvement to the process and to the selective vaporization apparatus.

 The present invention relates to a selective vaporization process for the removal of carbon and metals contained in heavy petroleum fractions, consisting in bringing such a fraction and an inert gas, serving to reduce the partial pressure of hydrocarbons, contact with a finely divided inert solid material, under mild cracking conditions at high temperature and with a short residence time of the hydrocarbons, in a confined riser, & separate products in the vapor state from said contact material carrying a in spite of the fuel of non-vaporized constituents of the petroleum fraction, rich in Conradson carbon or in metals, in cooling these products in the vapor state to a temperature lower than that where a significant thermal cracking occurs, in contacting the separate contact material with an oxidizing gas to burn the combustible despite and heat the catalyst to high temperature, and to bring back the contact material tact thus heated i the lower part of the confined column to bring it back into contact with the heavy petroleum fraction, this process being characterized in that, to ensure flexibility in the rate of introduction of the fraction or in the adjustment of the residence time or in these two parameters & at the same time, the inert gas is introduced into the lower part of the confined column and the heavy petroleum fraction is injected at a point located, in the column, in the lower part or above above it.

 The invention also relates to an apparatus for the selective vaporization of a heavy fraction of petroleum, characterized in that it comprises a contact device rising in the form of a vertical pipe, a vertical pipe for hot solids connected to the bottom of the device for uplink contact so as to bring therein a solid, inert and hot contact material, in the finely divided state, means making it possible to bring an inert carrier gas to the bottom of the uplift contact device for suspending the contact in a confined riser column of gas and contact material in the rising contact device, several injection means intended for the introduction of a heavy fraction of petroleum into the rising contact device and spaced at different levels above the bottom thereof, means provided at the top of the rising contact device for separating the vapors from the contact material carrying a combustible deposit, a burner, means while transferring the solid contact material thus separated to the burner, air inlet means to the burner serving to ensure the combustion of the combustible deposit, so that the temperature of the solid contact material rises, and means for transferring the contact material thus heated, from the burner to the vertical pipe for hot solids.

 The selective vaporization process is carried out by contacting a heavy load such as whole crudes, polluted crudes, residues and the like with an inert solid material finely divided in a vertical column confined, under the conditions desired to deposit on the solid heavy constituents rich in CC and / or metals and vaporize other constituents of the filler. This results from temperatures high enough to cause the desired vaporization and very short residence times of the hydrocarbons to avoid significant cracking. This maintains the operation at a low cracking severity to achieve the desired goal, which is to separate more valuable vaporizable constituents from those which are considered as impurities.

Water vapor, light hydrocarbons and the like are added to the confined riser of the selective vaporization installation to decrease the partial pressure of hydrocarbons in the feed and thereby facilitate vaporization.

 At the top of the column, hydrocarbons in the vapor state are separated from the inert solids carrying as deposit the non-vaporized constituents. The vapors are rapidly cooled to a temperature below that where significant thermal cracking occurs and are treated as desired in a catalytic cracker or the like.

 According to certain embodiments of the invention, the contact is made in a rising pipe. In other embodiments, an ascending column of inert solids is established in water vapor, gaseous hydrocarbons or both, and the direction of flow is reversed towards a descending column confined in which we inject the charge.

 Separate inert solids carrying the suit of non-vaporized constituents of the charge are transferred to a burner to burn the suit in air or another oxygen-containing gas. The heat generated by combustion of the deposit raises the temperature of the inert solids which are then brought back to the lower part of the confined riser to provide the heat of selective vaporization of an additional heavy load.

 The invention provides a method and an apparatus for varying the residence time of the hydrocarbons in the riser which defines the vertical riser confined where the selective vaporization is carried out. This is achieved by providing multiple charge injection points in the selective spray riser to compensate for variations in the quantity or quality of the feed material.

Reference is made below to the accompanying drawings, in which s
Figure 1 schematically shows an apparatus suitable for practicing the invention
FIG. 2 represents an embodiment in which the charge is injected into a descending column, which is obtained by reversing the direction of flow of a stream of inert solids in suspension initially established in the form of an ascending column.

 As shown in Figure 1, the main receptacles used are a rising pipe 1 used to make the short contact at high temperature between the hot inert solids and the load, which ends in a separation chamber 2, from which inert solids carrying a deposit of non-vaporized material is transferred to a burner 3 by a vertical pipe 4. The hot inert solids resulting from combustion in the burner 3 are brought back to the base of the rising pipe 1 by a vertical pipe 5, passing through a valve 6.

 A charge containing high-boiling constituents characterized by a high content of CC, of metals or both at the same time, is admitted to the riser pipe 1 by the pipe 7, so as to rise at high speed in the riser pipe 1, while it is in intimate contact with the hot inert solids coming from the vertical pipe 5. Most of the charge vaporizes & the temperature which prevails in the rising pipe because of the hot solids coming from the pipe 5. This vaporization is extremely fast and gives a rapidly rising vapor column in which inert solids are suspended. The parts of the charge which do not vaporize agglomerate on the inert solids, giving a combustible deposit consisting mainly of constituents with a high content of CC and metals.

 The solids are separated from the hydrocarbons in the vapor state at the top of the riser pipe 1, by one of the systems developed for the same purpose in the FCC process well known for cracking hydrocarbons in a riser pipe in the presence of an active cracking catalyst.

A preferred system in the present invention is the riser pipe described in US Patents 4,066,533 and 4,070,159. The upper end of the riser pipe 1 is open, so that, due to their inertia, the solids in suspension are sprayed into container 2. Vapors leave the rising pipe through a side vent thereof and go to the cyclone separator 8 where the solids still in suspension are removed and discharged by a dip tube 9 in the lower part of the container 2. The solids projected from the top of the rising pipe 2 and those coming from the dip tube 9 go down to a dewatering device 10, where the water vapor coming from the pipe 11 facilitates the vaporization of all the volatile hydrocarbons remaining, before the solids carrying a combustible spite enter the vertical pipe 4 to be transferred to the burner 3.

 The vapors separated from the solids entrained in the cyclone 8 go 1 through the conduit 12, to the transfer pipe 13 where they cool below the temperature where a significant thermal cracking occurs, for example by mixing with an appropriate coolant. such as a stream of cold hydrocarbons or battens.

 The burner 3 can have any of the various structures developed to burn combustible deposits formed of finely divided solids, for example the fluid catalytic cracking (FCC) regenerators.

Air admitted to the burner 3 through the pipe 15 provides oxygen for the combustion of the deposit on the inert solid, which gives gaseous combustion products evacuated by the combustion gas outlet 16. The operation is preferably carried out burner so as to maintain the temperature in the burner at its maximum level, usually limited by the metallurgy of the burner. This is achieved by adjusting the temperature of the riser pipe 1 to the minimum that can provide the desired amount of fuel (in the form of a deposit on inert solids) to maintain the maximum temperature of the burner. As is common in thermally balanced FCC units, valve 6 is controlled in response to the temperature at the top of the riser 1 to maintain this temperature at a preset level. This preset temperature is adjusted as well as it is necessary in selective spraying to maintain a desired maximum temperature in the burner 3. To compensate for a tendency towards a lower temperature in the burner 3, the preset temperature of the rising pipe 1 is lowered and vice versa.

The inert solids heated by combustion in the burner 3 are exhausted by means of steam in the burner 3 or the pipe 5 before being brought back to the rising pipe 1.

 The solid contact agent is essentially inert, in the sense that it causes minimal cracking of heavy hydrocarbons in the standardized microactivity test consisting in measuring the quantity of diesel fuel converted into gas, gasoline and coke by contact with the solid in a fixed layer. In this test, the charge is formed of 0.8 g of diesel from the center of the United States with an API density of 27, brought into contact with 4 g of catalyst for a supply time of 48 seconds at 4880C. A catalyst / diesel ratio of 5 is thus obtained at a relative flow rate by weight of 15 h. In this test, the solid used here has a microactivity of less than 20, preferably about 10. A preferred solid is formed of calcined kaolin microspheres. Other suitable inert solids include, in general. any solid meeting the indicated criteria.

The calcined kaolin microspheres preferably used in the process of the invention are known and are used as a chemical reagent with a sodium hydroxide solution in the manufacture of zeolitic catalysts for fluid cracking, as described in the patent.
US 3,647,718. On the other hand, in the practice of the present invention, the calcined kaolin microspheres do not serve as chemical reagent. Thus, the chemical composition of the microspheres used in the practice of the invention corresponds to that of a dehydrated kaolin. Typically, the calcined microspheres contain, by weight, approximately 51 to 53% of Six2, 41 to 45 X of A1203 and O to 1 X of H 2 O, the remainder being formed of small quantities of indigenous impurities, in particular iron, titanium and alkaline earth metals. Generally, the iron content (expressed as Fe203) is approximately 0.5% by weight and that of titanium (expressed as TiO2) approximately 2%
The microspheres are preferably produced by spray drying an aqueous suspension of kaolin. The term 1kaolin ", used here, extends to clays whose predominant mineral constituent is kaolinite, halloysite, nacrite, dickite, anauxite. Preferably, a plastic hydrated clay in fine particles is used, c that is to say a clay containing a significant quantity of particles smaller than 1 pin, in order to manufacture microspheres having an appropriate mechanical strength.

 Although it is preferable, in some cases, to calcine microspheres at temperatures of around 871 to 11490C to obtain particles of maximum hardness, it is possible to dehydrate them by calcination & at lower temperatures, for example between 538 and 8710C, thus converting the clay into material called wmetakaolin ". After calcination, the microspheres must be cooled and fractionated, if necessary, to recover the part which is located in the banana of desired size, for example 20 to 150 pine .

 The pore volume of the microspheres varies slightly depending on the temperature and the duration of the calcination.

Pore size distribution analysis of a representative sample, obtained with an analyzer
Desorpta using nitrogen desorption, indicates that most pores have diameters from 15 to 60 nm.

 The specific surface of the calcined microspheres is usually 10 to 15 m2 / g as measured by the B.E.T. well known using nitrogen absorption. It will be noted that the specific surface area of commercial fluid zeolitic catalysts is much greater, generally exceeding 100 m2 / g as measured by the B.E.T.

 Although the system just described has a superficial resemblance to an FCC unit, its operation is very different. More importantly, the contact riser pipe 1 is operated so as to remove from the charge an amount not exceeding the Conradson carbon index of the supply. This is in contrast to the normal FCC "Conversion" of 50 to 70% measured by the percentage of FCC product that does not boil within the charging range. The percentage eliminated by the present process is preferably of the order of 10 to 20% of the charge and formed of gas, petrol and deposit on the solid contact agent.

It is rare that the quantity eliminated in the form of gas, gasoline and deposit on the inert solid, exceeds, by weight, 3 to 4 times the Conradson carbon content of the charge. This is obtained by a very low cracking severity due to the inert nature of the solid and the very short residence time at the cracking temperature. As is well known, the cracking severity is a function of time and temperature. A higher temperature can be compensated for by a shorter residence time and vice versa.

 The new process provides an adjustment aspect which does not exist in FCC units, for the supply of hydrocarbons or steam to the contact riser. When dealing with materials with a high CC content, the temperature of the burner tends to rise due to an increased supply of fuel to the burner. This can be compensated for by increasing the quantity of hydrocarbons or water vapor supplied to reduce the partial pressure of hydrocarbons in the riser pipe or by recycling water from the upper manifold so that it vaporizes in the rising pipe giving steam.

 Thus, contact with the inert solid in the rising pipe provides a new sorption technique allowing the elimination of polycyclic aromatic compounds from residues (rich in CC and metals) while they are entrained in a current at low partial pressure d 'hydrocarbons due to the hydrocarbons or water vapor supplied to the riser pipe.

 The residue freed from carbon, salts and / or metals is a good quality FCC feed and can be transferred to the feed pipe of a FOC reactor operating in the conventional manner.

 It has been found that the nature of the selective vaporization is a function of the temperature, of the total pressure, of the partial pressure of hydrocarbon vapors, of the residence time, of the charge, etc. An effect of the temperature is a tendency to decrease the combustible deposit on the contact material as the contact temperature rises. Thus, larger proportions of the charge vaporize at higher temperatures and the side effect of thermal cracking of deposited hydrocarbons increases at higher temperatures. These effects of a higher temperature increase the yield of product given by the operation and decrease the fuel brought to the combustion zone in the form of combustible deposit.

 In general, the selective vaporization temperature is higher than the average boiling point of the feed, calculated by dividing by 9 the sum of the points at 10% and 90 s at ASTM distillation. For the heavy materials envisaged by the invention, the contact temperature is usually not appreciably lower than 4820C and it is lower than the temperatures where there is a marked cracking giving high yields of olefins. Thus, even at residence times of only 0.1 seconds or less, the selective vaporization temperatures are lower than about 5660C.

 The residence time for selective vaporization is not precisely calculated by the methods generally used in FCC cracking where the vapor volume increases sharply as the hydrocarbons remain in contact with an active cracking catalyst over the length of a riser pipe. In selective vaporization, the vapors are generated quickly on contact with the hot inert solid and keep an almost constant composition over the length of the riser, slightly increasing with a moderate thermal cracking which seems to be the cracking of the deposit on the inert solid.

Therefore, the residence time of the hydrocarbons in the selective vaporization is calculated with reasonable precision, by dividing the length of the rising pipe, from the point of injection of hydrocarbons to the point where they separate from the inert solids, by the surface velocity of the vapors (hydrocarbons, water vapor, etc.) at the top of the riser. Thus calculated, the residence time of the hydrocarbons in the vaporization will not be appreciably greater than about 3 seconds and it is preferably much shorter, one second at most, for example 0.1 seconds. As indicated above, the residence time and the temperature are correlated so as to ensure conditions of low cracking severity.

The quantity removed from the charge is very approximately equal to the CC content of the charge when operating under the preferential conditions and it rarely exceeds 3 to 4 times the CC content. In addition, the hydrogen content of the deposit is about 3 to 6%, lower than the normal content of 7 to 8% of the FOC coke.

 The invention provides a means of varying the residence time of the hydrocarbons, while keeping the charge rate constant, or of maintaining a constant residence time, with a reduced charge rate. It is obvious that the invention also provides other flexibility factors, namely that the residence times and / or the charge flow rates can be varied without keeping each other at constant levels.

 This effect results from the use of a riser pipe 1 having multiple injection points along its length. When injecting supply hydrocarbons at a point located above the bottom of the riser pipe, an inert gas is injected at the bottom of the latter to drive the inert solids up to the region of injection of hydrocarbons. This inert gas also has the function of lowering the partial pressure of hydrocarbons above the hydrocarbon injection point, thereby promoting selective vaporization. The inert gas is preferably supplied in the form of steam or water, but can be any gas which does not undergo a notable reaction under the conditions which prevail in the riser pipes. Thus, the process can use nitrogen as rising gas, or a hydrocarbon which does not undergo notable thermal cracking under the conditions of the rising pipe. Methane and other light hydrocarbons boiling below about 2320C- are preferred examples of these materials.

 As shown in Figure 1, the riser pipe 1 is provided with injection means making it possible to bring the load by valve pipes, 17 and 18, which can advantageously be spaced respectively at 25% and 50% of the height of the riser pipe 1. In a riser pipe thus modified, the injection pipe 7 at the bottom is provided with valve pipes 19 and 20, making it possible to bring water vapor or other matter to the bottom of the riser pipe 1 recycling systems such as acidified water, recycling gas or liquid hydrocarbons, with or without hydrocarbon feed.

 As mentioned above, water can be allowed to come to the bottom of the riser pipe 1 through the pipe 7, to supply the rising gas in the lower part of the riser pipe 1 and to reduce the partial pressure of hydrocarbons above the charge injection points.

It is understood that the word * water * designates here the liquid phase, unlike water vapor. The supply of liquid water at the bottom of the rising pipe 1 causes the immediate vaporization of the water in contact with the hot inert solids coming from the pipe 5, forming steam for the indicated purpose.

For reasons which are not currently known, the injection of liquid water at the bottom of the riser pipe 1 results in an increased hydrogen content of the vapor withdrawn as produced by the pipe 13, in comparison with the vapor injection d at the bottom of the riser.

It has been found that the addition of sulfur compounds such as hydrogen sulfide, mercaptans and the like, inhibits this tendency to form hydrogen when liquid water is injected.

 It is understood that the injection of liquid water into the bottom of the rising pipe has the effect of lowering the temperature of the inert solid to an extent corresponding to the latent heat of vaporization, plus the heat necessary to raise the temperature of the vapor. of water obtained.

This is compensated by an automatic increase in the supply of hot inert solid at the bottom of the riser and an increase in the inert solid / hydrocarbon ratio in the riser.

 It is also envisaged to add steam, water, recycling gas and liquid hydrocarbon, with the hydrocarbon charge, to the upper injection points, or to add it after the load of hydrocarbons.

The advantage of adding recycling materials such as steam, liquid water, recycling gas or liquid hydrocarbons, after charging, is to increase the speed of circulation of inert solid and thus raising the contact temperature between charge and inert solid. This eliminates the selective vaporization of the heaviest hydrocarbons in the feed and still results in short contact times.
In the embodiment of Figure 2, the flow in the contact riser 1 reverses to enter the container 2 by 8 flowing from top to bottom. Various structures for this purpose have been designed for parallax use in the FOC process, as generally described in column 4, lines 42 to 59, of the patent
US 4,070,159 already cited. As shown in FIG. 2, a column of ascending hot inert solids is established in the rising pipe 1 by injecting steam, liquid water, recycling gas or light stable liquid hydrocarbons at the bottom of the pipe. pipe rising through pipe 7, so that they mix with the inert solids added by pipe 5 and coming from the burner and put them in suspension. We can add residual fractions of charge or recycling, for example steam water, liquid water, recycling gas or liquid hydrocarbons, at points along the length of the riser 1, through pipes 17 and 18 as in Figure 1. At the highest point of the riser 1, the flow is directed horizontally through the part 23 of the contact device and then downwards, through the vertical part 24, towards the open end, with diversion of vapors towards the cyclones 8.

 Significant advantages are achieved by adding part or all of the load to the upper end of part 24 of the contact device. Extremely short contact times characterize this embodiment.

In addition, the force of gravity applied to the inert solid does not cause the "slip" which gives the inert solid a longer residence time in the contact device than to the hydrocarbon vapor generated by the contact of the charge with hot inert solids in the embodiment of FIG. 1. With certain types of residual fractions, it can be seen that the best results are obtained by injecting the total charge, via the pipe 25, into the part directed towards the bottom 24 of the contact device 1. In this type of operation, the rising part of the contact device serves to establish the suspension of hot inert solids in the gaseous medium, which also has the effect of reducing the partial pressure of vapors of hydrocarbons caused by the contact of the residual charge with hot inert solids.

 This system allows the operator increased flexibility in the conduct of selective spraying. With the flexibility inherent in the possibility of varying the ratio between charge and water vapor, it is possible to operate a unit with a wide range of charges and residence time to adapt the operation to variations in quantity and / or quality. of the available load.

Claims (14)

 1.- Selective vaporization process for the elimination of carbon and metals contained in heavy petroleum fractions, consisting in bringing such a fraction and an inert gas, serving to reduce the partial pressure of hydrocarbons, in contact with a material finely divided inert solid, under mild cracking conditions at high temperature and with a short residence time of the hydrocarbons, in a confined riser, to separate products in the vapor state from said contact material carrying a combustible deposit non-vaporized constituents of the petroleum fraction, rich in carbon Conradson or metal, to cool these products in the vapor state to a temperature below that where there is a significant thermal cracking, to contact the separated contact material with an oxidizing gas to burn the combustible deposit and heat the catalyst at high temperature, and to bring the contact material thus heated to the lower part of the confined column to bring it back into contact with the heavy petroleum fraction, this process being characterized by the fact that the inert gas is introduced in the lower part of the confined column and that the heavy petroleum fraction is injected at a point located, in the column, at the lower part or above it.  2.- Method according to claim 1, characterized in that the inert gas is water vapor.  3.- Method according to claim 1, characterized in that the inert gas is a hydrocarbon.  4.- Method according to claim 1, characterized in that the heavy fraction of petroleum is a residual fraction.  5.- Method according to claim 1, characterized in that one varies the injection point to vary the residence time.  6.- Method according to claim 1, characterized in that liquid water is introduced into the lower part of the confined column to generate water vapor as an inert gas.  7.- Method according to claim 6, characterized in that one also introduces a sulfur compound at the bottom of the column.  8.- Method according to one of claims 1 to 7, characterized in that the heavy hydrocarbon fraction is injected into the column at a point located above the lower part, so as to establish in the lower part of the column confined an ascending column of contact material suspended in the inert gas, and that heavy hydrocarbon is injected into the pre-established column of contact material in the inert gas, above the lower part .  9.- Method according to one of claims 1 to 8, characterized in that the direction of flow of the confined column is reversed and that it is poured out in the form of a descending current in an enlarged separation zone to effect the separation between products in the vapor state and the contact material.  10.- Method according to claim 9, characterized in that the heavy petroleum fraction is injected into the downdraft.  11.- Method according to claim 1, characterized in that is introduced into the column of steam, water, recycling gas or liquid hydrocarbon, with the heavy fraction of petroleum or after it.  12.- Method according to claim 1, characterized in that water vapor, water, recycle gas or liquid hydrocarbon is introduced into the column after the heavy petroleum fraction.  13.- Apparatus for selective vaporization of a heavy fraction of petroleum, characterized by the fact that it comprises a rising contact device in the form of a vertical duct, a vertical pipe for hot solids connected to the bottom of the rising contacting device so as to bring therein a solid, inert and hot contact material, in the finely divided state, means making it possible to bring an inert carrier gas to the bottom of the rising contact device for suspending the contact material in a column confined rising of gas and contact material in the rising contact device, several injection means intended for the introduction of a heavy fraction of petroleum in the rising contact device and spaced at different levels above the bottom of the latter, means provided at the top of the rising contact device for separating the vapors from the contact material carrying a combustible deposit, a burner, means making it possible to transfer to the burner on the solid contact material thus separated, means of air inlet to the burner serving to ensure the combustion of the combustible deposit, so that the temperature of the solid contact material rises, and means for transferring the contact material thus heated, from the burner to the vertical pipe for hot solids.  14.- Apparatus according to claim 13, characterized in that the rising contact pipe has a reverse bend at its upper end.