AU2018291824B2

AU2018291824B2 - Demetallization of hydrocarbons

Info

Publication number: AU2018291824B2
Application number: AU2018291824A
Authority: AU
Inventors: Ole Frej ALKILDE; Angelica HIDALGO VIVAS; Jacob Hjerrild Zeuthen
Original assignee: Haldor Topsoe AS
Current assignee: Topsoe AS
Priority date: 2017-06-30
Filing date: 2018-06-19
Publication date: 2024-03-14
Anticipated expiration: 2038-06-19
Also published as: RU2020103770A; CN209352833U; RU2020103770A3; AU2018291824A1; WO2019002028A1; CN109207198A

Abstract

The present disclosure refers to a process plant and a process for production of a demetallized hydrocarbon from a contaminated hydrocarbon comprising a means for mixing having one or more inlets in fluid communication with a contaminated hydrocarbon inlet and with an acid inlet and having an outlet a settling tank having an inlet, an aqueous phase outlet, and a firsthydrocarbon phase outlet, a means for evaporative concentration having an inlet, a water outlet and a brine outlet, wherein the outlet of said means for mixing is in fluid communication with the inlet of said settling tank and characterized in the inlet of said means for evaporative concentration being in fluid communication with the aqueous phase outlet of said settling tank and the water outlet of said means for evaporative concentration is in fluid communication with the acid inlet and said hydrocarbon phase outlet providing a demetallized hydrocarbon for withdrawal with the associated benefit of such a process plant having a reduced water consumption, in that the acid feed may be a concentrated acid and be diluted by the water withdrawn from the means for evaporative concentration.

Description

Title: Demetallization of hydrocarbons

In the processing of hydrocarbon mixtures the removal of heteroatoms is an important step for the product to comply with specifications and to avoid environmental or opera- tional challenges. Hydrotreating is a common way of withdrawing the heteroatoms e.g. sulfur, nitrogen and oxygen, from the contaminated hydrocarbon mixture by reacting them with hydrogen. However, if metal contaminants are present, even at relatively low concentrations, the activity of the catalysts can be severely affected. The metal contaminants may result in solid products, e.g., coke or gum, being formed on the catalytic surface with the effect of deactivating the hydrotreating catalyst. Therefore, in the hy- droprocessing of feeds with metal content, a so-called guard bed is necessary upstream the hydrotreating step. Tar is one source of hydrocarbon mixtures with a high amount of metals presence. When the metals are bound in the structures found in tar, it has surprisingly been found that large amounts of the metals may be released by con- tacting the contaminated hydrocarbon mixtures with aqueous acid solutions. It has furthermore been identified that an integrated process plant may be configured, in which sulfuric acid is produced from by-products in gas cleaning process step(s), which may be used in an acid wash demetallization process. An acid wash does however consume a high amount of acid or water, and therefore it is desired to reduce the con- sumption of water related to an acid wash.

According to the present invention, it has been identified that when an acid wash of tar is carried out, a combination of a settling tank and two centrifuges provide the optimal separation of the polar acid phase and the non-polar hydrocarbon phase, and that the removal of metals from the spent acid from the acid wash is optimally done by evaporative precipitation.

Acid number is an indicator of the organic acidity of a stream. ASTM D664 defines acid number as the quantity of a specified base, expressed in milligrams of potassium hy- droxide per gram of sample, required to titrate a sample in a specified solvent to a specified endpoint using a specified detection system.

Where a concentration is stated as ppm_w this shall be construed as weight parts per million. In accordance with the use of the term in the field of refinery processes, "hydrocarbon mixture" or "contaminated hydrocarbon mixture" shall comprise any stream dominated by hydrocarbons, but comprising other elements than hydrogen and carbon, such as oxygen, sulfur, nitrogen, halides and metals.

As used herein gasification shall be understood as a process in which a carbonaceous feedstock, such as coal or biomass, is heated either in the absence of oxygen, or in the presence of sub-stoichiometric amounts of oxygen with respect to oxidation to CO2. Such processes may also be known by other terms such as pyrolysis or coke produc- tion. The products from gasification typically comprise a solid phase, a gas phase and a liquid phase, i.e. tar. For simplicity the term gasification will be used to cover all such processes, unless otherwise stated.

As used herein contaminated hydrocarbon or tar shall in accordance with the terminol- ogy of the art be understood as a hydrocarbonaceous liquid originating from such a gasification process, or a derivative of such a liquid, which may also be known under terms such as light oil, carbolic oil, naphthalene oil, wash oil, anthracene oil or pitch. Terms such as pyrolysis oil, bio-oil, coal tar and coke oven tar may be used to indicate the process providing the tar. For the purpose of the present application, tar is typically a product of pyrolysis, coke production or coal gasification, and the term is interchanged with the term contaminated hydrocarbon. Tar is characterized by a high presence of heteroatoms (especially nitrogen, sulfur and oxygen) as well as a high content of aromatics. Typical parameters of tar include the hydrocarbonaceous liquid being a hydrocarbon mixture comprising from 0.5%, or 1 % to 5%, 6% or 10% oxygen, and hav- ing a hydrogen content below 10% w/w. Often tars have an acid number above 2 or 4 and below 7 or 8 mgKOH/g, a density higher than 0,90 g/ml, higher than 0,96 g/ml or higher than 1 .05 g/ml and a ratio between nitrogen atoms and sulfur atoms (N:S) above 1 :1 , 2:1 , 5:1 or 10:1 . As used herein the term "means for evaporative concentration" shall be used to cover one or more pieces of equipment, in which an aqueous solution of dissolved material is heated and concentrated by evaporation of water from which a purified water stream is obtained by condensation of the evaporated water, and from which a liquid stream of brine having an increased concentration of the dissolved material is withdrawn. The process may or may not involve precipitation of dissolved material as well, and the term brine shall only be understood to imply an aqueous liquid having an increased concentration of dissolved material, and shall not imply any information on the nature of the dissolved material. The "means for evaporative concentration" may involve more than a single evaporator and a single condenser, such as two or three evaporator/condensers in series.

In a broad perspective, the present disclosure relates to a process plant for production of a demetallized hydrocarbon from a contaminated hydrocarbon comprising a means for mixing having one or more inlets in fluid communication with a contaminated hydrocarbon inlet and with an acid inlet and having an outlet, a settling tank having an inlet, an aqueous phase outlet, and a first hydrocarbon phase outlet, a means for evaporative concentration having an inlet, a water outlet and a brine outlet, wherein the outlet of said means for mixing is in fluid communication with the inlet of said settling tank and characterized in the inlet of said means for evaporative concentration being in fluid communication with the aqueous phase outlet of said settling tank and the water outlet of said means for evaporative concentration is in fluid communication with the acid inlet and said hydrocarbon phase outlet providing a demetallized hydrocarbon for withdrawal, with the associated benefit of such a process plant having a reduced water consumption, in that the acid feed may be a concentrated acid and be diluted by the water withdrawn from the means for evaporative concentration.

In a further embodiment the process plant further comprises a first centrifuge having an inlet, a hydrocarbon outlet, and an aqueous outlet, wherein the inlet of said first centri- fuge is in fluid communication with an outlet of said settling tank and said demetallized hydrocarbon is withdrawn from the hydrocarbon outlet of said first centrifuge and the inlet of said means for evaporative concentration is in fluid communication with the aqueous outlet of said first centrifuge instead of or in addition to the aqueous phase outlet of said settling tank, with the associated benefit of such a process plant providing either increased purity of at least one of the aqueous phase and the demetallized hydrocarbon or alternatively allowing a less complete separation in the settling tank. Reducing the amount of water in the hydrocarbon phase also reduces the amount of metal directed to the downstream hydroprocessing process, and thus increase catalyst life time. Reducing the amount of hydrocarbons in the aqueous phase reduces the process yield loss and reduces the potential release of hydrocarbons to the environment.

In a further embodiment said settling tank further has a second hydrocarbon outlet and wherein the process plant further comprises a second centrifuge having an inlet, a hydrocarbon outlet, and an aqueous outlet, wherein the inlet of said second centrifuge being in fluid communication with an outlet of said settling tank being different from the outlet in fluid communication with the inlet of said first centrifuge and wherein a second demetallized hydrocarbon is withdrawn from the hydrocarbon outlet of said second centrifuge and the inlet of said means for evaporative concentration is in fluid communication with the aqueous outlet of said second centrifuge instead of or in addition to the aqueous phase outlet of said settling tank, with the associated benefit of such a process plant being suitable for separation of complex tar mixtures having a fraction with a density below that of water in one centrifuge and a fraction with a density above that of water in another centrifuge. Said second demetallized hydrocarbon may either be treated separately or the two demetallized hydrocarbons may be combined for a combined treatment.

In a further embodiment one or both of said first centrifuge and said second centrifuge further comprises an intermediate stream outlet, in fluid communication with one of the inlets of said settlement tank or an inlet of said means for mixing with the associated benefit of maximizing the separation of phases, and thus minimizing the amount of contaminated water being directed to downstream processes. In a further embodiment at least one aqueous outlet of said first centrifuge or if present, said second centrifuge, is in fluid communication with said first hydrocarbon phase outlet, with the associated benefit of avoiding an extra process volume due to recycle to the settlement tank, if the amount of water directed to the downstream process is sufficiently low and the aqueous phase is sufficiently pure for the downstream process.

In a further embodiment one or both of said first centrifuge and said second centrifuge further comprises a slurry stream outlet with the associated benefit of enabling removal of particulate matter being precipitated or released from suspension from the tar feedstock. In a further embodiment the process plant further comprises a means for hydropro- cessing having an inlet, a hydrocarbon outlet and a gas outlet, wherein the inlet of said means for hydroprocessing is in fluid communication with a hydrogen source, said first centrifuge hydrocarbon outlet and optionally said second centrifuge hydrocarbon outlet, a hydroprocessed hydrocarbon is withdrawn from the hydrocarbon outlet of said means for hydroprocessing, a sour gas is withdrawn from said gas outlet and optionally purified and recycled as part of said hydrogen source with the associated benefit of such a process plant providing a hydroprocessed hydrocarbon with effective use of hydrogen and other process utilities.

In a further embodiment the process plant further comprises a means of gas separation having an inlet, a hydrogen outlet and a sulfide outlet, a sulfuric acid plant having a sulfide gas inlet and a sulfuric acid outlet wherein said sulfuric acid plants sulfide gas inlet is in fluid communication with the sulfide outlet of the means of gas separation and the acid inlet of said settling tank is in fluid communication with said sulfuric acid outlet, with the associated benefit of such a process plant providing at least an amount of the sulfuric acid used for the acid wash.

A further aspect of the present disclosure relates to a process for producing a hy- drotreated hydrocarbon from a contaminated hydrocarbon mixture obtained from a gasification process, , comprising the steps of

a. combining said contaminated hydrocarbon mixture with an aqueous acid and water forming a mixture,

b. mixing said mixture after a reaction time,

c. separating said mixture in a contaminated aqueous phase and a purified hydrocarbon phase by gravity separation,

d. purifying said contaminated aqueous phase by evaporation and condensing pure water for recycling it to step a,

e. optionally purifying at least one of said contaminated aqueous phase and said hydrocarbon phase by centrifugal separation,

f. and optionally combining said purified hydrocarbon phase with a gas rich in hydrogen forming a hydroprocessing stream and directing said hydroprocessing stream to a hydroprocessing step forming a hy- drotreated hydrocarbon. with the associated benefit of such a process being an effective demetallization and hydroprocessing process, with minimal requirements for addition of make-up water.

In a further embodiment the contaminated hydrocarbon mixture comprises from 0.5%, or 1 % to 5%, 6% or 10% oxygen with the associated benefit of such a process being an effective demetallization and hydroprocessing process, being able to to remove oxygen from the hydrocarbon mixture.

In a further embodiment the aqueous acid is taken from the group comprising strong mineral acids or organic acids preferably citric acid, oxalic acid, hydrochloric acid, phosphoric acid, phosphoric acid or sulfuric acid with the associated benefit of such acids being effective in demetallization.

In a further embodiment the process does not comprise addition of an aqueous liquid comprising elements other than C. H, O, N and S in a concentration above 0.1 %, with the associated benefit of such a process avoiding addition of constituents which must be removed prior to hydroprocessing.

In a further embodiment the concentration of the aqueous acid is from 1 % or 2% to 5%, 10% or 30%.

With the associated benefit of such an acid being effective in releasing metals from the hydrocarbons, while minimizing the requirements for materials.

In a further embodiment the ratio of contaminated hydrocarbon mixture to acid is from 50:1 , 20:1 or 10:1 to 2:1 , 1 :1 or 1 :2, with the associated benefit of such a ratio maximizing the release of metals while minimizing the volume of acid used.

In a further embodiment the temperature in step b is from 20°C to 1 10°C with the associated benefit of this temperature range being effective in demetallization while not re- quiring excessive material quality.

In a further embodiment the process further comprises the step upstream step (a) of gasifying a carbonaceous material, forming said hydrocarbon having an acid number above 1.5 mg KOH/g, with the associated benefit of such a process providing quality hydrocarbon from a carbonaceous material.

The removal of metals from contaminated hydrocarbon mixtures is an important pro- cess step, since the presence of metals may result in large problems in the refinery plant. Specifically, guard beds for capturing metals may be costly, and may have high pressure drops when metal has been captured on the materials. Therefore, a process which does not sequester metals in the process but which is able to withdraw them, is desired.

It is known to add acids for removal of metals from contaminated hydrocarbon mixtures, but typically the removal has been found to be most efficient at neutral or close to neutral conditions to avoid acidification of the product, since this will result in a risk of corrosion of equipment and in addition most refinery products have specifications limit- ing the acid number. However, tars typically have high content of carbolic, carboxylic and naphthenic acids, and thus these products are handled in equipment made from corrosion resistant materials. Therefore a pretreatment step by contact with aqueous acid solutions to remove metal contaminants will not change the processability of the product significantly or change the selection of construction material for the reactors, vessels and other equipment, as considerations of corrosiveness are made in the field of refineries for feeds with acid number above 0.5 mg KOH/g and that feeds with acid number above 1.0, 1 .5 or 2.0 mg KOH/g are considered corrosive, and require special and focused attention in process design and/or selection of materials. During hydrotreating, the acid number /acidity is reduced/eliminated as acidic compounds, e.g., naphthenic acids, phenols, naphthalenols, are converted to hydrocarbons and water, and the hydrotreatment processes also has a tolerance to the presence of moderate amounts of dissolved water. In coke oven tars and pyrolysis oil the amount of metals may typically be 200-500 ppm_w and in fats and oils of renewable origin the amounts may also be in the level of hundreds of ppm_w. Most of these metals are in the form of soluble compounds or bound as complexes with organic compounds, which cannot be removed by mechanical filtration, but some may also be present as or in particles, suspended in the tar. The addition of acid to the contaminated hydrocarbon mixture is, without being bound by theory, believed to release the metals present as complexes with phenol or other organic groups (e.g., naphthenic acids), followed by withdrawal of the metals by chelation with the acid.

An associated benefit of the acid wash demetallization process is that the content of total and basic nitrogen compounds in the contaminated hydrocarbon mixture is reduced, thereby reducing the NH3 and organic nitrogen inhibition to the hydrotreatment and par- ticularly to the hydrocracking catalysts. This implies a reduction of the required catalyses) volume and a lower hydrogen consumption.

The choice of acid for acid wash of tar depends on a number of aspects. An important aspect is of course the ability to scavenge metals, which is related to the chelation abil- ity of the acid and the strength of the acid. In addition the compatibility of the acid with downstream refining processes is important. From this aspect sulfuric acid has the benefit that any sulfuric acid remaining entrained in the hydrocarbon as well as bisulfate and sulfate anions will be easily removed in the downstream hydrodesulfurization processes together with the removal of organic sulfur and hydrogen sulfide. Similarly or- ganic acids will also be compatible with downstream processes, whereas phosphoric or hydrochloric acid may further aggravate the poisoning effect of phosphorus and chloride or even contaminate the downstream processes with elements which would otherwise not be present in the hydrocarbon feed. In the processing of tar, the viscosity of the tar is also important. Some tars are highly viscous and may benefit from being processed at elevated temperatures around from 50 to 100°C, whereas other tars may be less viscous, and therefore are processable at lower temperatures. The process must also be designed in consideration of the feed conditions. If tar is directly obtained from upstream pyrolysis or gasification, it is likely that the tar may have to be cooled in order to be processed with a liquid phase of aqueous acid, whereas in a process where tar is processed from storage the tar may have to be heated to be processable. When purifying a tar by acid wash, the acid comprising the metals of the tar may be separated from the hydrocarbon phase in a settling tank. Such a tank is inexpensive to operate, but the separation is not perfect.

Alternatively, the acid/hydrocarbon mixture may be separated by use of a centrifuge, but especially if a tar separating in a phase having a higher density than water and a phase having a lower density than water this may be a complex process. It has, however, been identified that combining a settling tank and a centrifuge is beneficial, since streams which are easily separated may be withdrawn directly from the settling tank, and streams which are less easily separated in the settling tank may be further separated in a centrifuge, thus limiting the number and/or size of centrifuges, e.g. by centrifuging a heavy hydrocarbon stream and an aqueous stream separately, but not centrifuging the light hydrocarbon stream. In addition, a fraction rich in particulate matter may also be withdrawn from one or both centrifuges, and an intermediate stream may be recycled to the settling tank for further separation.

The aqueous phase withdrawn from the settling tank, and also from the one or two cen- trifuges used, will be a weak acid, with a high amount of metals and possibly other impurities. For environmental and economic reasons, it is beneficial to reuse as much of this stream as possible, and therefore a method of metal salt withdrawal is desired. It is known that wash water or wash acid containing metal salts, may be recycled after alkaline precipitation of metal salts carried out by adjusting pH.. This is however not a feasi- ble approach for the present situation, since a pH adjustment would typically involve adding an alkaline solution, such as sodium hydroxide, which would result in an increased amount of sodium in the aqueous phase. Sodium is well known to be a catalyst poison, and even small amounts of sodium in the hydrocarbon directed to a downstream hydroprocessing plant would result in dramatic shortening of catalyst lifetime.

Instead it has been identified that precipitation or at least concentration by evaporation is beneficial. A process plant configured with a means for evaporative concentration such as a combined evaporator and condenser for withdrawal of water for recycle will therefore be beneficial. Such an evaporator may be one or more units in series, and the water condenser may be provided for each evaporator or be a single unit for all evaporators.

The purified hydrocarbon withdrawn from the one or two centrifuges may subsequently be hydrotreated, either separately or as two fractions of hydrocarbon respectively with a density below that of water and a fraction with a density above that of water in combination. The hydroprocessing may involve one or both of hydrocracking and hydrotreatment. From the hydrotreatment of the hydrocarbon, a stream rich in hydrogen sulfide may be withdrawn. This stream may be converted into concentrated sulfuric acid, for use in the acid wash process, e.g. by a wet sulfuric acid process.

Figures

Fig.1 shows a process layout corresponding to the present disclosure.

Fig.2 shows a process layout corresponding to the prior art.

In the figures the following elements are referred to:

102 Contaminated hydrocarbon mixture

104 Water

106 Concentrated acid

108 Aqueous acid solution

1 10 Means for mixing

1 12 Acid/hydrocarbon mixture

1 14 Settling tank

1 16 Intermediate phase

1 18 Light phase

120 Heavy phase

122 First centrifuge

124 Second centrifuge

126,130 Contaminated aqueous phase

128 Mixed light tar and aqueous phase

132 Mixed heavy tar and aqueous phase

134 Heavy purified hydrocarbon phase

136 Tar sludge 138 Combined evaporator and condenser

140 Concentrated brine

142 Water

144 Steam

146 Condensate

202 Hydrocarbon mixture

208 Aqueous acid solution

210 Mixing reactor

214 Settling tank

216 Contaminated aqueous phase

218 Light clean tar phase

220 Heavy purified tar phase

Fig.1 shows an embodiment of the process according the present disclosure. A con- taminated hydrocarbon mixture 102 comprising oxygenates and metals is optionally heated and is mixed with an aqueous acid solution 108 made from water 104,142 and concentrated acid 106 and directed to a means for mixing, such as a static mixer 1 10 or alternatively a stirred tank, in which mixing takes place. The acid/hydrocarbon mixture 1 12 is directed to a settling tank 1 14 in which the phase separation is effectuated by a simple gravitational settling. In the embodiment shown in Fig.1 , 3 phases are withdrawn from the settling tank; an intermediate phase 1 16, dominated by contaminated water, a light phase 1 18 being substantially only hydrocarbons and not in need of further phase separation and a heavy phase 120 dominated by hydrocarbons, but containing an amount of contaminated water. In alternative embodiments only a single hy- drocarbon phase may be withdrawn, which may have a density above that of water or below that of water. The intermediate phase 1 16 is directed to a first centrifuge 122 and the heavy phase 120 is directed to a second centrifuge 124. The first centrifuge 122 separates a stream of contaminated aqueous phase 126 from an amount of mixed light tar and aqueous phase 128. The mixed light tar and aqueous phase 128 is directed to be combined with the other streams at the inlet to the static mixer 1 10. The second centrifuge 124 separates a stream of contaminated aqueous phase 130 from a minor amount of mixed heavy tar and aqueous phase 132, optionally a clean heavy tar 134 and a tar sludge 136. The mixed light tar and aqueous phase 128 and the mixed heavy tar and aqueous phase 132 are directed to the inlet to the static mixer 106, but the two mixed streams could also be directed to the inlet of settling tank 1 14. The two contaminated aqueous phase streams 126 and 130 are both directed to a combined evaporator and condenser 138, in which a concentrated brine 140 is produced by evaporation. Pure water 142 is condensed and directed as feed to the static mixer 1 10. Energy for evaporator is provided from the condensation as well as other sources, typically process steam 144 e.g. from a hydroprocessing plant, which is returned to the hydropro- cessing plant as condensate 146, but other heat sources than process steam may be possible. The light purified hydrocarbon phase 1 18 and the heavy purified hydrocarbon phase 134 are directed separately or in combination to a hydroprocessing plant, which may be a hydrocracking plant, for conversion of the tar into lighter products or which may be a hydrotreatment plant for removal of non-metallic further heteroatoms such as sulfur and nitrogen as well as dearomatization and other hydrotreatment processes.

In a further embodiment one or both of the centrifuges may be omitted, since a moder- ate amount of water may be directed to the hydroprocessing without serious negative impact, but the residence time in the settling tank may have to be increased in this case, and the metal load on hydroprocessing catalyst must also be considered. For practical reasons multiple centrifuges may be operated in parallel to provide for the necessary flow of centrifuge feed.

In further embodiments moderate amounts of water to may be directed to hydroprocessing by adding one or both of streams 128 and 132 to stream 1 18 and directing the combined stream to hydroprocessing. A further embodiment also involves removal of an amount of water from the light hydrocarbon phase, by use of a further centrifuge. Such an embodiment may be required for specific feedstock or allow for reduced residence time in the settling tank.

In alternative embodiments, only a single hydrocarbon phase is withdrawn from the set- tling tank. This may either be a light hydrocarbon or a heavy hydrocarbon, depending on the nature of the contaminated hydrocarbon.

In Fig.2 a similar process according to the prior art is shown. The contaminated hydrocarbon mixture 202 comprising oxygenates and metals is together with an aqueous acid solution 208 directed to a mixer settler type device with a mixing tank 210, in which mixing takes place. The mixture is directed to a connected settling tank 214. A light clean tar phase 218, a contaminated aqueous phase 216 and a heavy purified tar phase 220 are withdrawn from the settler. The contaminated aqueous phase 216 cannot be recycled to the acid wash process due to a high concentration of metals. The metals may be withdrawn by precipitation with sodium hydroxide, but the aqueous solute phase would not be suitable for recycle to the acid wash, as an amount of the sodium would transfer to the hydrocarbon phase and poison a downstream hydropro- cessing catalyst.

Example

A process for demetallization of coke oven tar by an acid wash involving a settling tank is compared a similar acid wash involving a settling tank with further purification of the hydrocarbon product by centrifugation.

A process was designed in accordance with Fig.1 , receiving 162 ton/h tar. The tar is combined with 2.7 ton/h 93% sulfuric acid, 6.5 ton/h make up water and 44.9 ton/h recycled water. From the process 4.5 ton/h sludge, 4 ton/h brine, 53 ton/h light purified hydrocarbon and 106 ton/h heavy purified hydrocarbon is withdrawn. The evaporation process consumes 10 ton/h of low pressure steam.

If the contaminated aqueous phase was not concentrated by evaporation, an extra 44.9 ton/h water would have to be added to the process, since the contaminated aqueous phase would not be suitable for recycle.

Claims

Claims:

1 ) A process plant for production of a demetallized hydrocarbon from a contaminated hydrocarbon comprising

a means for mixing having one or more inlets in fluid communication with a contaminated hydrocarbon inlet and with an acid inlet and having an outlet

a settling tank having an inlet, an aqueous phase outlet, and a first hydrocarbon phase outlet,

a means for evaporative concentration having an inlet, a water outlet and a brine outlet,

wherein

the outlet of said means for mixing is in fluid communication with the inlet of said settling tank and

characterized in

the inlet of said means for evaporative concentration being in fluid communication with the aqueous phase outlet of said settling tank and the water outlet of said means for evaporative concentration is in fluid communication with the acid inlet and said first hydrocarbon phase outlet providing a demetallized hydrocarbon for withdrawal.

2) A process plant according to claim 1 further comprising

a first centrifuge having an inlet, a hydrocarbon outlet, and an aqueous outlet, wherein

the inlet of said first centrifuge is in fluid communication with an outlet of said settling tank and

said demetallized hydrocarbon is withdrawn from the hydrocarbon outlet of said first centrifuge and the inlet of said means for evaporative concentration is in fluid communication with the aqueous outlet of said first centrifuge instead of or in addition to the aqueous phase outlet of said settling tank. 3) A process plant according to claim 1 or 2 wherein said settling tank further has a second hydrocarbon outlet and wherein the process plant further comprises a second centrifuge having an inlet, a hydrocarbon outlet, and an aqueous outlet,

wherein

the inlet of said second centrifuge being in fluid communication with an outlet of said settling tank being different from the outlet in fluid communication with the inlet of said first centrifuge and wherein

a second demetallized hydrocarbon is withdrawn from the hydrocarbon outlet of said second centrifuge and the inlet of said means for evaporative concentration is in fluid communication with the aqueous outlet of said second centrifuge instead of or in addition to the aqueous phase outlet of said settling tank. 4) A process plant according to claim 1 , 2 or 3 wherein one or both of said first centrifuge and said second centrifuge further comprises an intermediate stream outlet, in fluid communication with one of the inlets of said settlement tank or an inlet of said means for mixing.

5) A process plant according to claim 2, 3 or 4 wherein at least one aqueous outlet of said first centrifuge or if present, said second centrifuge, is in fluid communication with said first hydrocarbon phase outlet.

6) A process plant according to claim 1 , 2, 3, 4 or 5 wherein one or both of said first centrifuge and said second centrifuge further comprises a slurry stream outlet.

7) A process plant according to claim 1 , 2, 3, 4, 5 or 6 further comprising

a means for hydroprocessing having an inlet, a hydrocarbon outlet and a gas outlet,

wherein

the inlet of said means for hydroprocessing is in fluid communication with a hydrogen source, and at least one of said first hydrocarbon phase outlet, said first centrifuge hydrocarbon outlet and optionally said second centrifuge hydrocarbon outlet,

a hydroprocessed hydrocarbon is withdrawn from the hydrocarbon outlet of said means for hydroprocessing,

a sour gas is withdrawn from said gas outlet and optionally purified and recycled as part of said hydrogen source.

A process plant according to claim 7 further comprising

a means of gas separation having an inlet, a hydrogen outlet and a sulfide outlet,

a sulfuric acid plant having a sulfide gas inlet and a sulfuric acid outlet wherein said sulfuric acid plants sulfide gas inlet is in fluid communication with the sulfide outlet of the means of gas separation and the acid inlet of said settling tank is in fluid communication with said sulfuric acid outlet.

A process for producing a hydrotreated hydrocarbon from a contaminated hydrocarbon mixture obtained from a gasification process comprising the steps of a. combining said contaminated hydrocarbon mixture with an aqueous acid and water forming a mixture,

b. mixing said mixture after a reaction time,

c. separating said mixture in a contaminated aqueous phase and a purified hydrocarbon phase by gravity separation,

d. purifying said contaminated aqueous phase by evaporation and condensing pure water for recycling it to step a,

e. optionally purifying at least one of said contaminated aqueous phase and said hydrocarbon phase by centrifugal separation,

f. and optionally combining said purified hydrocarbon phase with a gas rich in hydrogen forming a hydroprocessing stream and directing said hydroprocessing stream to a hydroprocessing step forming a hydrotreated hydrocarbon.

10) The process according to claim 9, in which the contaminated hydrocarbon mixture comprises from 0.5%, or 1 % to 5%, 6% or 10% oxygen. 1 1 ) The process according to claim 9 or 10 according to which the aqueous acid is taken from the group comprising strong mineral acids or organic acids preferably citric acid, oxalic acid, hydrochloric acid, phosphoric acid, phosphoric acid or sulfuric acid.

12) The process according to claim 9, 10 or 1 1 , in which the process does not comprise addition of an aqueous liquid comprising elements other than C. H, O, N and S in a concentration above 0.1 %.

13) The process according to claim 7, 8, 9, 10, 1 1 or 12 in which concentration of the aqueous acid is from 1 % or 2% to 5%, 10% or 30%.

14) The process according to claim 7, 8, 9, 10, 1 1 , 12 or 13 according to which the ratio of contaminated hydrocarbon mixture to acid is from 50:1 , 20:1 or 10:1 to 2:1 , 1 :1 or 1 :2

15) The process according to claim 7, 8, 9, 10, 1 1 , 12, 13 or 14 according to which the temperature in step b is from 20°C to 100°C.

16)A process according to claim 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 1 1 , 12, 13, 14 or 15, further comprising the step upstream step (a) of gasifying a carbonaceous material, forming said contaminated hydrocarbon mixture.