The present invention relates to a method for producing a high value low sulfur fuel from a combination of two heavy hydrocarbonaceous feedstocks while keeping the hy- drogen consumption low.

Processing of heavy fractions of hydrocarbons is a challenge in refineries. These frac- tions may contain large amounts of heteroatoms, especially metals, nitrogen and sulfur, the C:H ratio is often high and the boiling point is too high for most commercial prod- ucts.

Therefore, an appropriate combination of hydrotreatment and cracking is required for these products to be converted into commercially attractive products. The residue of atmospheric pressure feedstock fractionation (i.e. a fractionation operat- ing close to atmospheric pressure, e.g. up to about 2 atmospheres above atmospheric pressure); atmospheric residue; is often the source of such fractions. Traditionally at- mospheric residue has been used for bunker fuel, which has not required extensive conversion after fractionation. With increased requirements to the quality of marine fuel this fraction must instead be directed to further processing in the refinery.

One possible approach is the separation in a vacuum fractionator into vacuum gas oil (VGO) and vacuum residue (VR). VGO will contain moderate amounts of metals and sulfur and will be highly compatible with hydrocracking.

VR will contain a high amount of metals, which are often removed by solvent extraction of an asphalt fraction leaving deasphalted oil (DAO).

During hydrotreatment (HDT) for the purpose of hydrodemetallization (HDM), hydro- denitrogenation (HDN) and hydrodesulfurization (HDS) the structure of the hydrocar- bons may be destabilized, which may produce products boiling in the diesel range, but falling outside diesel specifications.

Cracking, either in fixed beds in the presence of hydrogen as hydrocracking (HC) or in the absence of hydrogen in fluidized beds as Fluidized Catalytic Cracking (FCC) is an attractive process for converting large molecules to smaller molecules. Hydrocracking is mainly attractive for hydrocarbons boiling in the range below 550°C. For higher boil- ing feedstocks accelerated deactivation of the catalyst by coking may occur, especially if the feedstock is too heavy, the conditions are too severe or the feedstock C:H ratio is too high. As an alternative, FCC may be used for feedstock without an upper boiling point limit, since a continuous regeneration of catalyst takes place, where deposited coke will be burnt of the catalyst and with heat being recuperated for the process. A short-coming of the FCC process is that it does not increase the hydrogen content of the products and therefore does not deliver the highest quality, especially for middle distillate products such as jet and diesel fuel.

It has now been identified that by segregating the feedstock according to the severity demanded for hydrodesulfurization and directing the most demanding heavy feedstock, such as deasphalted oil, which typically comprises a high amount of heteroatoms, to hydrotreatment, while directing the less demanding feedstock comprising a low amounts of metals, such as LVGO, to hydrocracking, the H ₂ consumption may be mini- mized and the quality of products may be kept high, compared to a process in which all feedstock is directed to hydrotreatment followed by hydrocracking. Upgrading of a hydrocarbon mixture shall in the following be used to describe any treatment of a hydrocarbon mixture which results in a higher value product. Upgrading may involve the following non-extensive list of conversions; reduction of boiling point to a more attractive range, isomerization to improve the cold flow properties, removal of heteroatoms, conversion of polyaromatics to monoaromatics and conversion of aromat- ics to saturated hydrocarbons.

Hydrotreating shall in the following be used to describe the conversion of a hydrocarbo- naceous molecules by the catalytically promoted hydrogenolysis and hydrogenation ef- fecting heteroatoms such as sulfur and nitrogen to be converted to hydrogen sulfide and ammonia and effecting unsaturated compounds such as olefins and aromatics to be saturated to produce aliphatic structures.

Hydrocracking shall in the following be used to describe the conversion of a hydrocar- bonaceous molecule by the catalytically promoted breaking of carbon-carbon bonds to produce two or more lower molecular weight molecules. Hydrocracking is typically combined with subsequent hydrotreating of the lighter molecules producing fully satu- rated structures, but an amount of hydrotreating also takes place on the hydrocracking catalyst.

The term process severity shall in the following be used to describe the reaction condi- tions. Conditions favoring higher reaction rates, such as higher temperature, higher hy- drogen partial pressure, lower space velocity, and larger catalyst quantities shall be called more severe.

The term demanded severity shall in the following be as a quantitative measure of how severe conditions must be for the demanding feedstock to be processed by hydrotreat- ing or hydrocracking is. For the present examples, the quantification is based on the temperature required for 90% hydrodesulfurization under a set of standard conditions. The demanded severity is deemed to be higher if the temperature required for conver- sion is higher.

The term demanding feedstock shall in the following be used to describe the severity required for conversion of a feedstock. A feedstock to be processed by hydrotreating or hydrocracking is deemed to be more demanding by the extent to which it requires more process severity to achieve a given result. Feedstock A is considered as more de- manding than feedstock B if the required temperature for 90% hydrodesulfurization is higher for feedstock A than for feedstock B. A feedstock is considered significantly more demanding if the difference is at least 5°C.

A broad aspect of the present disclosure relates to a process for conversion of a first hydrocarbonaceous feedstock and a second hydrocarbonaceous feedstock by hydro- processing, in which said first hydrocarbonaceous feedstock is characterized by de- manding a higher process severity compared to said second hydrocarbonaceous feed- stock, said process comprising the steps of combining said first hydrocarbonaceous feedstock with a first gas stream comprising hydrogen forming a hydrotreatment feed, directing said hydrotreatment feed to a hydrotreatment section under hydrotreatment conditions, withdrawing a hydrotreated product from said hydrotreatment section, sepa- rating said hydrotreated product in a first vapor/liquid separator forming a liquid-phase hydrotreated product and a hydrotreated vapor stream, directing an amount of said liq uid-phase hydrotreated product to a stripping step providing at least a stripper light ends stream and a stripped liquid hydrotreated product, forming a hydrocracker feed comprising said second hydrocarbonaceous feedstock and a second gas stream com- prising hydrogen, directing said hydrocracker feed to a hydrocracking section under hy- drocracking conditions forming a hydrocracked product, and directing said hy- drocracked product to a fractionation section from which at least a light product corn- prising a vapor phase, a heavy distillate product and an unconverted oil product are produced, wherein an amount of said hydrotreated vapor stream is directed to said hy- drocracking section, either for being combined with said hydrocracker feed upstream the hydrocracking section, or for being combined with the hydrocracked product up- stream fractionation, and wherein the combined stream optionally is further treated in a further hydrotreatment section upstream said fractionation, with the associated benefit of providing a process in which a demanding hydrocarbonaceous feedstock and a less demanding hydrocarbonaceous feedstock may be treated independently, in a way where the most demanding feedstock is only treated by hydrotreatment and the least demanding feedstock is treated by hydrocracking, and the products may be segregated for independent downstream treatment while reducing capital and operational costs by integrating the sub-processes, and reducing hydrogen consumption according to the requirements. In this configuration, where the most demanding feedstock is treated in a moderately severe hydrotreatement process and the less demanding feedstock is treated by more severe hydrocracking significant process savings are obtained, by fo- cusing on segregated treatments resulting in adequate upgrading, rather than the ex cessive upgrading which would be a result of the traditional approach of treating both streams together.

An amount of said hydrotreated vapor stream, may be directed for being combined with said hydrocracker feed upstream the hydrocracking section, with the associated benefit of such a process allowing a further treatment of the vapor-phase of the hydrotreated stream, such that e.g. middle distillate products may be upgraded by hydrocracking to high quality, while avoiding the risk of the heaviest demanding feedstocks will result in catalyst deactivation by coking.

An amount of said hydrotreated vapor stream, may be directed to the hydrocracking section for being combined with the hydrocracked product, and wherein the combined stream optionally is further treated in a further hydrotreatment section, with the associ- ated benefit of such a process allowing a further treatment of the hydrotreated stream, such that e.g. middle distillate products may be upgraded to high quality, while avoiding the risk of yield loss or catalyst deactivation from the demanding feedstocks being di- rected to contact the material catalytically active in hydrocracking.

In a further embodiment said hydrotreatment section contains a material catalytically active in hydrotreatment, which comprises a first metal taken from the group of tung- sten and molybdenum, a metal taken from the group of nickel and cobalt and a support taken from the group of alumina, silica, titania, silica-alumina, and combinations thereof, with the associated benefit of such a catalytically active material being suited for hydrotreatment in the presence of heteroatoms, such as sulfur.

In a further embodiment said hydrotreatment conditions are characterized as a temper- ature from 300°C to 450°C, a pressure from 5 MPa to 20 MPa, a LHSV of 0.3 hr ¹ to 3 hr ¹ and a hydrogen to oil ratio of 100 to 2000 Nm ³ /m ³ , with the associated benefit of these conditions being suitable for hydrotreatment of demanding feedstocks.

In a further embodiment said hydrocracking section contains a material catalytically ac- tive in hydrocracking which comprises either a first metal taken from the group of tung- sten and molybdenum and second a metal taken from the group of nickel and cobalt, or a noble metal taken from the group of platinum and palladium, an acidic component such as silica-alumina, molecular sieves and combinations thereof and a support taken from the group of alumina, silica and titania, with the associated benefit of such a cata- lytically active material being suited for hydrotreatment in the presence of heteroatoms, such as sulfur.

In a further embodiment said hydrocracking conditions are characterized as a tempera- ture from 300°C to 450°C, a pressure from 5 MPa to 20 MPa, a LHSV of 0.3 hr ¹ to 3 hr ¹ and a hydrogen to oil ratio of 100-2000 Nm ³ /m ³ , with the associated benefit of these conditions being suitable for hydrocracking of heavy feedstocks.

In a further embodiment the hydrocracker catalyst and the hydrocracking conditions are chosen such that 20 to 90% of the fraction of said hydrocracker feed boiling above 370°C is converted to product boiling below 370°C, with the associated benefit of such a moderate hydrocracker conversion limiting the amount of vapor product to the benefit of the overall liquid yield of commercial product. In a further embodiment a recycle stream comprising hydrogen is separated from the hydrocracked product stream and compressed and returned in a parallel flow to both the hydrotreatment step and the hydrocracking step as said first gas stream comprising hydrogen and said second gas stream comprising hydrogen, with the associated bene- fit of enabling a high gas to oil ratio while avoiding excessive addition of hydrogen.

In a further embodiment a recycle stream comprising hydrogen is separated from the hydrocracked product stream and compressed and returned as said second gas stream comprising hydrogen to said hydrocracking step and a hydrogen rich make-up gas stream having a hydrogen purity greater than 90 mole%, 95 mole% or 98 mole% is directed as said first gas stream comprising hydrogen, with the associated benefit of enabling a high hydrogen partial pressure, and thus severity, in the hydrotreatment section, while avoiding excessive addition of hydrogen.

In a further embodiment at least a portion of the liquid hydrodesulfurization product is directed to a fluid catalytic cracking unit, optionally in combination with at least a portion of the liquid hydrocracked product, with the associated benefit of maximizing the value of the product mix, by converting high boiling products to e.g. transportation fuels.

In a further embodiment the hydrogen content of the liquid hydrocracked product is higher than the hydrogen content of the liquid hydrotreatment product, with the associ- ated benefit of the liquid hydrocracked product being of higher potential value when used as transportation fuel, while the liquid hydrocracked product is suitable for FCC processing. In a further embodiment said first heavy hydrocarbonaceous feedstock is taken from the groups comprising heavy vacuum gas oil, deasphalted oil, FCC cycle oil, heavy coker gas oil, visbroken or thermally cracked gas oil and in which said second hydro- carbonaceous feedstock is taken from the group comprising heavy atmospheric gas oil and light vacuum gas oil, with the associated benefit of such a process providing an ef- ficient conversion of such heavy feedstocks.

In a further embodiment said first heavy hydrocarbonaceous feedstock has a density above 900 kg/m ³ or 915 kg/m ³ or 930 kg/m ³ , a total aromatics concentration of greater than 30 wt% or 40 wt% or 50 wt%, and a hydrogen content less than 12.5 wt% or 12.0 wt% or 11.5 wt%, with the associated benefit of the product properties after hydrotreat- ment of such a feedstock being substantially improved as an FCC feed. In a further embodiment at least a portion of the hydrotreatment product is directed as a low sulfur fuel oil component, optionally in combination with at least a portion of the liquid hydrocracked product, wwith the associated benefit of such a process being sim- ple, while providing a low sulfur fuel oil. In a further embodiment a distillate portion of the hydrocracked product is directed as high quality ultra-low sulfur diesel fuel with the qualities of minimum 40 cetane number and maximum 15 wt ppm sulfur or as a high quality ultra-low sulfur kerosene with the quality of minimum 19mm smoke point and suitable for application to aviation turbine fuel, with the associated benefit of such products of high value being produced in an ef- ficient process.

In a further embodiment at least a portion of the hydrocracked product unconverted oil fraction is directed as a lube oil base-stock component or as a feedstock for stream cracking to produce olefins, with the associated benefit of such products of high value being produced in an efficient process.

A further aspect of the disclosure relates to a process for conversion of a raw feed- stock, comprising a first atmospheric feedstock fractionation step at a pressure being less than 250 kPa above atmospheric pressure, from which the residue comprises at least one of said first hydrocarbonaceous feedstock and said second hydrocarbona- ceous feedstock which are treated in a process as described above, with the associ- ated benefit of providing a process for efficiently converting atmospheric residue into commercial products. In a further embodiment the process for conversion of a raw feedstock optionally corn- prises a further atmospheric feedstock fractionation step, and a fractionation step oper- ating at an absolute pressure below 10 kPa receiving residue from one of said atmos- pheric raw feedstock fractionation steps, providing a vacuum gas oil and a vacuum res- idue wherein the vacuum gas oil comprises said first hydrocarbonaceous feedstock and the vacuum residue comprises said second hydrocarbonaceous feedstock, with the associated benefit of providing an efficient process in terms of hydrogen consump- tion as well as product quality, from one feedstock suitable for hydrocracking and an- other feedstock suitable for FCC after hydrotreatment.

A further aspect of the present disclosure relates to a process plant having an inlet for a first hydrocarbonaceous feedstock and an inlet for second hydrocarbonaceous feed- stock, said process plant comprising a hydrotreatment section, a first vapor/liquid sepa- rator, a stripping section, a hydrocracking section and a fractionation section, said pro- cess plant being configured for directing said first hydrocarbonaceous feedstock to the hydrotreatment section, and withdrawing a hydrotreated product from said hydrotreat- ment section, directing said hydrotreated product to a first vapor/liquid separator form- ing a liquid-phase hydrotreated product and a hydrotreated vapor stream, directing an amount of said liquid-phase hydrotreated product to a stripping step providing at least a stripper light ends stream and a stripped liquid hydrotreated product and directing said second hydrocarbonaceous feedstock and a second gas stream comprising hydrogen as a hydrocracker feed to a hydrocracking section forming a hydrocracked product, di- recting said hydrocracked product to said fractionation section having outlets for at least a light product comprising a vapor phase, a heavy distillate product and an uncon- verted oil product, wherein an amount of said a hydrotreated vapor stream is directed to said hydrocracking section, either for being combined with said hydrocracker feed upstream the hydrocracking section, or in a process plant further comprising a hy- drotreatment section for being combined with the hydrocracked product upstream said fractionation section, and wherein the combined stream optionally is further treated in said further hydrotreatment section upstream said fractionation section, with the associ- ated benefit of such a process plant being less expensive in capital cost as well as op- erational cost, compared to a process plant designed for similar conversion without segregation of the feedstock. Detailed description

To comply with fuel standards, the heteroatoms of sulfur and nitrogen are typically re- moved by hydrotreatment, in which hydrogen reacts with the hydrocarbon in the pres- ence of a catalytically active material. The reaction takes place under so-called hy- drotreating conditions. The parameters of hydrotreating conditions include temperature, space velocity, hydrogen partial pressure and catalyst composition and these parame- ters interact in ways which are known to the skilled person and therefore the hy- drotreatment process may be optimized by selecting an appropriate combination of conditions. A set of conditions causing high conversion is called high severity condi- tions. In general, the parameters causing high conversion are higher temperature, lower space velocity and higher hydrogen partial pressure. The use of a catalyst with enhanced activity or an increased catalyst volume will also be considered increased severity even if the other conditions are unchanged. As it is known to the skilled per- son, the appropriate severity for a hydrotreatment process depends on the desired products in balance with the cost, as too high severity may result in extra operational cost and/or product loss.

Where heteroatoms form part of the molecular skeleton, the removal may cause de- composition or cracking of the feedstock molecules into shorter fragments, and thus hydrotreatment will often be related to a reduction in boiling point.

Heavy hydrocarbonaceous feedstocks are commonly processed by hydrocracking for the purpose of conversion to lower boiling products. Hydrocracking involves decompos- ing large hydrocarbon molecules into smaller molecules. During hydrocracking hydro- gen reacts with the hydrocarbon in the presence of a catalytically active material corn- prising a hydrogenation metal and an acid site - typically a molecular sieve or amor- phous silica-alumina. Depending on conditions and the nature of the hydrocracking cat- alyst and especially the acid site, hydrocracking may involve different positions of the molecules.

Hydrocracking is beneficially carried out on a feedstock having a low amount of het- eroatoms such as sulfur and nitrogen, to ensure an efficient process with long process cycles between exchange of catalyst. Hydrocracking of hydrocarbons having a high carbon to hydrogen ratio, e.g. above 7:1 (wt:wt), may be associated with a risk of formation of polynuclear aromatics (PNA) and heavy polynuclear aromatics (HPNA), as well as depositing of carbon on the catalyst (coking). Therefore, high boiling hydrocarbons with a high C:H ratio are undesired in the hydrocracker. Hydrocarbons with a high C:H ratio are also generally higher in aro- matics content and can be more difficult to upgrade to high quality distillate fuels prod- ucts.

Heavy products in a hydrocracking process, are often called unconverted oil (UCO), re- ferring to the fact that even though the molecule may be chemically converted, the boil- ing point is not changed from being above the diesel boiling range.

The highest boiling fractions and the residue of atmospheric pressure fractionation are often the source of such feedstock, and these will be summarized in the following. Tra- ditionally atmospheric residue (AR) has been used for bunker fuel, which has not re- quired extensive conversion after fractionation. With increasing requirements to the quality of marine fuel this fraction must instead be directed to further processing in the refinery. The heavy distillate fraction produced from the crude oil atmospheric distillation tower is called heavy atmospheric gas oil (HAGO). Typically, HAGO is characterized by a fi- nal boiling point less than 510°C.

The residue of atmospheric fractionation, AR, will contain a high amount of heteroa- toms and it typically further separated in a vacuum fractionator.

The separation in a vacuum fractionator into vacuum gas oil (VGO) and vacuum resi- due (VR). VGO will contain moderate amounts of metals and sulfur and will be highly compatible with hydrocracking. The vacuum fractionator is typically equipped with mul- tiple product draws allowing the production of both a light vacuum gas oil (LVGO) prod- uct and a heavy vacuum gas oil (HVGO) product. LVGO is typically characterized by a final boiling point less than 540°C and HVGO is typically characterized by a final boiling point greater than 540°C. VR is often treated by solvent extraction to remove highly aromatic asphaltenes and re- duce carbon residue, leaving deasphalted oil (DAO), which typically has a final boiling point greater than 600°C. The vacuum residue can also be thermally cracked by processes known as delayed coking or visbreaking to produce lighter products with lower boiling range normally des- ignated as heavy coker gas oil (HCGO) and visbroken gas oil (VBGO). Typically, these fractions are characterized by higher sulfur and nitrogen content and lower hydrogen content compared to HVGO.

To carry out conversion of UCO this stream is often directed to a fluid catalytic cracking (FCC) unit, which operates as a 2 section fluidized bed. In one section of the FCC unit catalytic cracking of hydrocarbons occur in an endothermic process without addition of hydrogen, and in a different section exothermic oxidation of carbon deposited as coke on the catalyst surface occurs, releasing heat for the cracking process. Therefore, FCC processes may operate on feedstocks having a high tendency to coking, e.g. due to having a high C:H ratio.

With the present disclosure a process has now been identified, in which demanding heavy feedstocks with high C:H ratios are preferentially directed to FCC and heavy feedstocks with moderate or low C:H ratio are preferentially directed to hydrocracking. Such a process is beneficial, compared to a simpler process in which the feedstocks are combined, hydrotreated and hydrocracked, and in which the heaviest hydrocracked products are directed to FCC. It has further been identified that an appropriate indicator of how demanding such a feedstock is, is the severity required to obtain the same rela- tive hydrodesulfurization, e.g. the temperature required for obtaining 90% hydrodesul- furization in an otherwise identical setup.

The illustrated process for treatment of heavy feedstocks is suitable for segregated treatment of different pairs of demanding and less demanding feedstocks. The de- manding feedstock will often originate from the vacuum residue, e.g. as DAO, HCGO or VBGO, whereas the less demanding feedstock will be a VGO distillate fraction, e.g. HVGO, or possibly LVGO. The process is however also suitable for segregated treat- ment of pairs of distillates, e.g. where the demanding fraction is HVGO and the less de- manding fraction is LVGO or HAGO. With the present disclosure it has been realized that the important criteria for the segregation of the feedstocks are the demanded pro- cess severity of the feedstocks, i.e. the chemical nature of the feedstock, rather than their physical parameters such as boiling point or density, and thereby process configu- rations with increased cost effectivity are realized.

Figures

Figure 1 illustrates an embodiment of the present disclosure, in which the light products of hydrotreatment by-pass the initial beds of hydrocracking.

Figure 2 illustrates an embodiment of the present disclosure, in which the light products of hydrotreatment fully bypass the hydrocracking step.

Figure 3 illustrates an embodiment of the present disclosure, where the hydrogen rich gas to the hydrotreatment step is supplied in a once through mode and combined with the hydrocracking step as makeup hydrogen with no recirculation of hydrogen gas back to the hydrotreatment step.

Figure 4 illustrates the prior art, in which the feedstock is combined, not segregated, and directed first to hydrotreatment and then to hydrocracking.

List of elements in the figures:

102, 202, 302, 402 First hydrocarbonaceous feedstock

105, 205 A first gas stream comprising hydrogen

104, 204, 304, 404 Makeup hydrogen stream

106, 206 Recycle gas comprising hydrogen

108, 208, 308 Heat exchanger

109, 209, 309, 409 Combined hydrotreater feed

1 10, 210, 310, 410 Hydrotreatment section

1 12, 212, 312, 412 Hydrotreated product

1 14, 214, 314 First vapor/liquid separator

1 16, 216, 316 Hydrotreated vapor stream

1 18, 218, 318 Hydrotreated liquid stream

120, 220, 320 Stripping step

122, 222, 322 Stripping medium

124, 224, 324 Stripper light ends stream 126, 226, 326 Stripped liquid hydrotreated product

128, 228, 328, 428 Second hydrocarbonaceous feedstock

130, 230, 330, 430 A second gas stream comprising hydrogen

132, 232, 332, 432 Heat exchanger

134, 234, 334 Hydrocracker feed

136, 236, 336, 436 Process heater

138, 238, 338 438 Hydrocracking section

240 Hydrotreatment bed

142, 242, 342, 442 Hydrocracked product

144, 244, 344, 444 Second vapor/liquid separator

146, 246, 346, 446 Hydrogen rich vapor stream

148, 248, 348, 448 Hydrocracked liquid stream

150, 250, 350, 450 Recycle gas compressor

152, 252, 352, 452 Fractionation tower

154, 254, 354, 454 Light distillate product

156, 256, 356, 456 Heavy distillate product

158, 258, 358, 458 Fractionator bottoms stream

160, 260, 360 Heavy unconverted stream

162, 262, 362, 462 Heavy stream for further upgrading

A demanding first hydrocarbonaceous feedstock 102 e.g. a vacuum residue is com- bined with a first gas stream comprising hydrogen 105, for example a high purity makeup hydrogen stream 104 optionally in combination with a first gas stream compris- ing hydrogen 106 and then preheated by heat exchanger 108 or other means of heat- ing. The combined hydrotreater feed 109 is sent to a hydrotreatment section 110 for hydrotreating reactions in one or more fixed catalyst beds. A primary purpose of the hy- drotreatment section 110 is to upgrade the first hydrocarbonaceous feedstock 102 for the purpose of further processing and conversion in downstream facilities. The hy- drotreated product 112, which is a mixture of vapor and liquid products is separated in a first vapor/liquid separator 114 providing a hydrotreated vapor stream 116 and a hy- drotreated liquid stream 118. The hydrotreated liquid stream 118 is sent to stripping step 120 which utilizes a stripping medium 122 such as steam or hydrogen to remove a stripper light ends stream 124 from the stripped liquid hydrotreated product 126. A less demanding second hydrocarbonaceous feedstock 128 e.g. vacuum gas oil is combined with hydrogen, for example a second gas stream comprising hydrogen 130 and preheated by heat exchanger 132 and then mixed with the hydrotreated vapor stream 116 from the first vapor/liquid separator 114, providing a hydrocracker feed 134 which is preheated by a process heater 136 or other means of heating and flows to the hydrocracking section 138 for both hydrotreating and hydrocracking reactions in one or more fixed catalyst beds. A primary purpose of the hydrocracking section is to effect conversion of the second hydrocarbonaceous feedstock 128 by hydrocracking to make high quality naphtha and distillate products such as ultra-low sulfur diesel. In addition, by combining the second hydrocarbonaceous feedstock with the hydrotreated vapor product 116 from the first stage, this vapor product is further upgraded e.g. by hydro- dearomatization and hydrodesulfurization reactions.

The hydrocracked product 142 from the hydrocracking section 138 is cooled in heat ex- changer 132 and flows to a second vapor/liquid separator 144 that effects separation of the stream into a hydrogen rich vapor stream 146 and hydrocracked liquid stream 148 containing the hydrocracking section products. The hydrogen rich vapor stream 146 is compressed by the recycle gas compressor 150 and returned to the hydrotreatment section 110 and hydrocracking section and 138 as first recycle stream comprising hy- drogen 106 and second recycle stream comprising hydrogen 130. The hydrocracked liquid stream 148 is sent to a fractionation tower 152 or series of fractionation towers to effect separation into multiple distillate products, here shown as a light distillate product 154 and a heavy distillate product 156 which, dependent on feed and hydrocracking severity may include liquefied petroleum gas, naphtha, kerosene and diesel fuel. A fractionator bottoms stream 158 is also produced as a non-distilled fraction of the sec- ond stage product and may be withdrawn separately.

The stripped liquid hydrotreated product 126 and heavy unconverted stream 160 may optionally be combined as a heavy stream for further upgrading 162, which for example may be directed for Fluid Catalytic Cracking (FCC). The level of upgrading and quality of the two streams differ substantially and therefore the streams can be maintained segregated from each other to increase the combined value. Figure 2 illustrates another embodiment of the invention in which a demanding first hy- drocarbonaceous feedstock 202 e.g. a vacuum residue is combined with a first gas stream comprising hydrogen 205, for example a high purity makeup hydrogen stream 204 optionally in combination with a first gas stream comprising hydrogen 206 and then preheated by heat exchanger 208 or other means of heating. The combined hy- drotreater feed 209 is sent to a hydrotreatment section 210 for hydrotreating reactions in one or more fixed catalyst beds. A primary purpose of the hydrotreatment section 210 is to upgrade the feed 202 for the purpose of further processing and conversion in downstream facilities. The hydrotreated product 212, which is a mixture of vapor and liquid products is separated in a first vapor/liquid separator 214 providing a hy- drotreated vapor stream 216 and a hydrotreated liquid stream 218. The hydrotreated liquid stream 218 is sent to stripping step 220 which utilizes a stripping medium 222 such as steam or hydrogen to remove a stripper light ends stream 224 from the stripped liquid hydrotreated product 226.

A less demanding second hydrocarbonaceous feedstock 228 e.g. vacuum gas oil is combined with hydrogen, for example a second gas stream comprising hydrogen 230 and preheated by heat exchanger 232, providing as a hydrocracker feed 234 which is preheated by a process heater 236 or other means of heating and flows to the hy- drocracking section 238 for both hydrotreating and hydrocracking reactions in one or more fixed catalyst beds. The hydrotreated vapor stream 216 from the first vapor/liquid separator 214, is directed to an additional hydrotreatment bed 240 of the second stage reactor. A primary purpose of the hydrocracking section is to effect conversion of the second hydrocarbonaceous feedstock 228 by hydrocracking to make high quality naph- tha and distillate products such as ultra-low sulfur diesel. In addition, by directing the hydrotreated vapor product 216 from the first stage to a hydrotreatment bed 240 down- stream the hydrocracking section, in either the same or a further reactor, this vapor product is further upgraded, without interfering with the hydrocracking section 238 of the second stage reactor.

The hydrocracked product 242 from the hydrotreatment bed 240 is cooled in heat ex- changer 232 and flows to a second vapor/liquid separator 244 that effects separation of the stream into a hydrogen rich vapor stream 246 and hydrocracked liquid stream 248 containing the hydrocracking section products. The hydrogen rich vapor stream 246 is compressed by the recycle gas compressor 250 and returned to the hydrotreatment section 210 and hydrocracking section and 238 as first gas stream comprising hydro- gen 206 and second gas stream comprising hydrogen 230. The hydrocracked liquid stream 248 is sent to a fractionation tower 252 or series of fractionation towers to effect separation into multiple distillate products, here shown as a light distillate product 254 and a heavy distillate product 256 which, dependent on feed and hydrocracking sever- ity may include liquefied petroleum gas, naphtha, kerosene and diesel fuel. A fractiona- tor bottoms stream 258 is also produced as a non-distilled fraction of the second stage product and may be withdrawn separately.

The stripped liquid hydrotreated product 226 and heavy unconverted stream 260 may optionally be combined as a heavy stream for further upgrading 262, which for example may be directed for Fluid Catalytic Cracking (FCC). The level of upgrading and quality of the two streams differ substantially and therefore the streams can be maintained segregated from each other to increase the combined value.

This embodiment has the benefit over the embodiment of Figure 1 , that as the hydrotreated vapor stream 216 is not treated in the hydrocracking section 238 the hy- drogen consumption is lower, and often the product value is unchanged or even higher than the product value of the embodiment of Figure 1.

In the embodiment illustrated in Figure 3, a demanding first hydrocarbonaceous feed- stock 302 e.g. a vacuum residue is combined with hydrogen, for example a high purity makeup hydrogen stream 304 and then preheated by heat exchanger 308 or other means of heating. The combined hydrotreater feed 309 is sent to a hydrotreatment section 310 for hydrotreating reactions in one or more fixed catalyst beds. A primary purpose of the hydrotreatment section 310 is to upgrade the feed 302 for the purpose of further processing and conversion in downstream facilities. The hydrotreated product 312, which is a mixture of vapor and liquid products is separated in a first vapor/liquid separator 314 providing a hydrotreated vapor stream 316 and a hydrotreated liquid stream 318. The hydrotreated liquid stream 318 is sent to stripping step 320 which uti lizes a stripping medium 322 such as steam or hydrogen to remove a stripper light ends stream 324 from the stripped liquid hydrotreated product 326. A less demanding second hydrocarbonaceous feedstock 328 e.g. vacuum gas oil is combined with hydrogen, for example an amount of a recycle stream comprising hydro- gen 330 and preheated by heat exchanger 332 providing as a hydrocracker feed 334 which is preheated by a process heater 336 or preheated by other means of heating and flows to the hydrocracking section 338 for both hydrotreating and hydrocracking re- actions in one or more fixed catalyst beds. A primary purpose of the hydrocracking sec- tion is to effect conversion of the second hydrocarbonaceous feedstock 328 by hy- drocracking to make high quality naphtha and distillate products such as ultra-low sul- fur diesel. Contrary to Figure 1 and Figure 2, the hydrotreated vapor product 316 from the first stage, is not further upgraded, and in addition the reaction stage for the most demanding feed receives make up hydrogen 304 which has a higher hydrogen content than the recycle stream comprising hydrogen 330, and thus provides a higher process severity in the hydrotreatment sections. The hydrocracked product 342 from the hydrocracking section 338 is mixed with the hydrotreated vapor stream 316 from the first stage gas/liquid separator 314, providing a combined stream which is cooled in heat exchanger 332 and flows to a second va- por/liquid separator 344 that effects separation of the stream into a hydrogen rich vapor stream 346 and hydrocracked liquid stream 348 containing the hydrocracking section products. The hydrogen rich vapor stream 346 is compressed by the recycle gas com- pressor 350 and returned to the hydrocracking section 338 as a recycle stream corn- prising hydrogen 330. The hydrocracked liquid stream 348 is sent to a fractionation tower 352 or series of fractionation towers to effect separation into multiple distillate products, here shown as a light distillate product 354 and a heavy distillate product 356 which, dependent on feed and hydrocracking severity may include liquefied petroleum gas, naphtha, kerosene and diesel fuel. A fractionator bottoms stream 358 is also pro- duced as a non-distilled fraction of the second stage product and may be withdrawn separately. The stripped liquid hydrotreated product 326 and heavy unconverted stream 360 may optionally be combined as a heavy stream for further upgrading 362, which for example may be directed for Fluid Catalytic Cracking (FCC). The level of upgrading and quality of the two streams differ substantially and therefore the streams can be maintained segregated from each other to increase the combined value. Figure 4 according to the prior art shows a process in which a demanding first hydro- carbonaceous feedstock 402 is initially combined with a second less demanding sec- ond hydrocarbonaceous feedstock 428 (in practice the two streams may typically have been combined in a single line prior to the upgrading process) and with hydrogen, for example a high purity makeup hydrogen stream 404 optionally in combination with a recycle stream comprising hydrogen 430 and then preheated by heat exchanger 432 and/or other means of heating such as heater 436. The combined hydrotreater feed 409 is sent to a hydrotreatment section 410 for hydrotreating reactions in one or more fixed catalyst beds. A primary purpose of the hydrotreatment section 410 is to upgrade the combined hydrotreater feed 409 for the purpose of further processing and conver- sion in downstream facilities. The hydrotreated stream 412 flows to the hydrocracking section 438 for hydrocracking reactions in one or more fixed catalyst beds. The hydrocracked product 442 from the hydrocracking section 438 is cooled in heat ex- changer 432 and flows to a second vapor/liquid separator 444 that effects separation of the stream into a hydrogen rich vapor stream 446 and hydrocracked liquid stream 448 containing the second stage reaction products. The hydrogen rich vapor stream 446 is compressed by the recycle gas compressor 450 and returned to the hydrotreatment section 410 as a recycle stream comprising hydrogen 430. The hydrocracked liquid stream 448 is sent to a fractionation tower 452 or series of fractionation towers to effect separation into multiple distillate products, here shown as a light distillate product 454 and a heavy distillate product 456 which, dependent on feed and hydrocracking sever- ity may include liquefied petroleum gas, naphtha, kerosene and diesel fuel. A fractiona- tor bottoms stream 458 is also produced as a non-distilled fraction of the second stage product and may be withdrawn separately.

The heavy unconverted stream 458 may be directed as a heavy stream for further up- grading 462, which for example may be directed for Fluid Catalytic Cracking (FCC). Contrary to the embodiments corresponding to Figure 1 , Figure 2 and Figure 3, it is not possible to benefit from the knowledge that the levels of upgrading and quality of the two streams are substantially different and therefore the streams can be maintained segregated from each other to increase the combined value. The process according to Figure 4 has the benefit of having a simpler separation lay- out, but the volumes of the hydrotreatment section and the hydrocracking section re- spectively will be higher than the comparable sections of Figures 1-3, and in addition the lack of possibility to treat the feedstocks according to specific requirements also re- suits in increased hydrogen consumption and thus reduced cost of operation.

Examples

To illustrate the effect of the present disclosure, hydrotreatment and hydrocracking of the products from a delayed coking unit are studied for a process according to the pre- sent disclosure and for a process according to the prior art. The properties of a straight run heavy vacuum gas oil (HVGO) and a heavy coker gas oil (HCGO) from a delayed coking unit are shown in Table 1 , together with the blend of the two in the relative pro- portion of 70% HVGO plus 30% HCGO. The demanded severity is evaluated for each of the three feedstocks by hydrotreating the feedstock to 90% hydrodesulfurization at 1 10 barg, liquid hourly space velocity (LHSV)=1.0 v/v/hr, hydrogen gas to oil ratio (GOR)= 500 Nm ³ /m ³ . As expected, the de- manded severity of the blend, as indicated by the reaction temperature to achieve 90% HDS, is intermediate (354°C) between HVGO and HCGO (370°C).

The common objective of the examples is to achieve 60% conversion to high quality diesel product with the balance of unconverted oil being allocated as feedstock for fur- ther conversion by fluid catalytic cracking (FCC), according to the target specifications shown in Table 2.

By examination of Table 1 , it can be readily seen that the HCGO is heavier, higher in sulfur, nitrogen and aromatics content and with much lower hydrogen content relative to the HVGO feed. Adding HCGO to the HVGO, results in a feed blend that is substan- tially more demanding to catalytically hydrocrack compared to the HVGO by itself. In particular, the higher aromaticity and higher nitrogen content will require higher hydro- gen partial pressure to achieve the necessary conversion and diesel product quality. This is reflected in the demanded severity for hydrodesulfurization, as indicated by the temperature for which 90% hydrodesulfurization is obtained, thus providing a relative measure of how demanding the feedstocks are. According to Example 1 , carried out with a segregated feedstock according to the pres- ently disclosed process, in accordance with Figure 1 , a sufficient conversion at a pres- sure of 110 barg, providing a FCC feed with 500 ppm sulfur and 150 ppm nitrogen is possible. The diesel yield is 48% and the cetane, sulfur and specific gravity require- ments are fulfilled.

According to Example 2, carried out with a mixed feedstock according to the prior art, in accordance with Figure 4, sufficient conversion requires a pressure of 160 barg, providing a FCC feed with 30 ppm sulfur and 5. The diesel yield is 50% and the cetane, sulfur and specific gravity requirements are fulfilled.

The segregated feed approach can achieve the same diesel product quality, even at substantially reduced hydrogen partial pressure, as a consequence of removing the high aromatics component of the feed from the hydrocracking step and the hydrocrack- ing step operating at higher net conversion which helps to reduce diesel density and improve cetane quality. The chemical hydrogen consumption is reduced by approxi- mately 15% for the segregated feed configuration compared to the conventional ap- proach. As a consequence of performing less hydrogenation of the heavy coker gas oil, the unconverted product FCC feed is higher in sulfur and nitrogen content and is heav- ier and higher in aromatics. However, even though the FCC feedstock properties of Ex- ample 2 may be considered slightly better than those of Example 1 , these differences are only of minor relevance, since the FCC process is sufficiently severe to handle the FCC feedstocks from Example 1 and Example 2 equally well. The resulting product is thus still an excellent quality feed for FCC.

As a result of the reduced design pressure for the segregated feed unit, the capital cost is expected to be 5 to 10% less than the conventional combined feed unit. In addition, the consumption of hydrogen is decreased by 14%. Table 1:

Table 2: Table 3: