Gasification of high-ash feedstocks

Abstract

A residual stream comprising liquid hydrocarbons and metal-rich solid particles is reacted with an oxidant stream in a gasifier to produce a syngas stream, which is quenched in a water bath. The risk of plugging in the water line is reduced by removing solids from the recirculated water stream. Acid gases are stripped from at least a portion of the recirculated water to reduce the risk of dissolved acid gases reacting with metal ions to form precipitates.

Description

BACKGROUND

[0001] The following disclosure relates to a process for converting a liquid hydrocarbon feedstock including ash by partial oxidation to produce syngas. Ash is defined as non-combustible materials such as metals, metal oxides, and metal sulfides.

[0002] Heavy hydrocarbon liquid residue streams are produced as byproducts of oil refining, for example, slurry hydrocracking technology or ebullated bed technology. These processes produce a liquid hydrocarbon waste stream that contains a high concentration of solids derived from metal catalyst precursors, with solid carbon forming around the metals. Heavy hydrocarbon liquid residue streams containing ash can also be obtained from tar sands, also known as oil sands or bitumen sands. These low value streams can be upgraded by gasification to produce higher value hydrogen, fuel gas, and electricity for on-site use. Economic drivers are causing increasingly challenging streams to be identified for gasification, including streams with much higher weight percentages of metals, for example, from spent catalysts. These solids do not react with oxygen and cause high loading of ash in the gasifier.

[0003] Prior industrial experience in residue gasification has shown that residue feedstocks with ash content higher than 0.4 wt% cannot be processed using a syngas effluent cooler without damaging the equipment, resulting in an unacceptable short campaign life. The syngas effluent cooler (SEC) uses hot syngas to generate steam before entering the soot removal section. Soot is defined as solid particles including unburned carbon and metal ash. New feedstocks such as liquid residue streams can have ash in excess of 1.0 wt% and higher concentrations of fouling components. The higher ash content of these new feedstocks also increases the total suspended solids loading in the soot water treatment system.

[0004] Ash can include metal catalysts that tend to cause fouling and in extreme cases, plugging of the lines. Because the metal catalysts are valuable products to be recycled, it is desirable to operate the gasifier under a non-slagging regime to prevent the metal from forming molten slag that is uneconomical to separate. If the ash is coated with a sufficient level of carbon, the ash will not stick to itself and cause fouling problems. De Jong et al. (US 9,487,400) teaches using a bottom quench gasifier for liquid hydrocarbons containing ash that produces sufficient carbon at a temperature below the ash melting temperature to coat the metal ash so that the ash does not form molten slag.

[0005] For SEC technology, the preferred carbon to ash ratio is in the range of 4 to 6, where the carbon to ash ratio is defined as the ratio of the weight of carbon to the weight of metal in the soot. Below this range, the ash particles are not sufficiently coated with carbon, resulting in sticking to surfaces, cooling and solidification. Above this range, the carbon coating on the ash particles is too thick, such that the particles can agglomerate and foul the equipment, and even if the ash particles can exit the SEC, the required downstream solids removal system is too large to be practical. In the case of residual feedstocks with ash greater than 1.0 wt%, the high carbon to ash ratio results in an even larger downstream solids removal system.

[0006] Because ash is a mixture of substances, the phase change from solid ash to molten slag occurs over a range of temperatures. The lowest temperature at which ash begins to melt is the initial deformation temperature, at which point the ash begins to become sticky. As the temperature increases, the ash further melts, passing through the softening temperature, the hemispherical temperature, and finally the fluid temperature at which the ash is completely molten. The ash melting temperature is a function of the ash composition, and thus a function of the feedstock composition. ASTM 1857 method measures the phase transition temperatures of an ash sample, as described in Akar et al. (Asian J. of Chemistry (2009) 21(3):2105-2109). The ash melting temperature is defined herein as the fluid temperature.

[0007] One alternative to coating the ash with carbon is to operate above the ash melting temperature under a slagging regime, such that the ash forms a slag, which is defined as a predominantly liquid phase rich in oxides. In contrast, dry ash is defined as a predominantly solid oxide-rich particle that passes through a non-slagging gasifier entrained in syngas. Liu (WO 2017 / 102940) describes a gasifier for residual feedstocks that operates at a temperature under a slagging regime. Koseoglu et al. (US 9,056,771) teaches the use of a membrane wall gasifier to react heavy residuals with spent solid heterogeneous catalysts in a configuration that uses an SEC instead of a water bath. The membrane wall uses a buildup of solidified mineral ash slag to protect the refractory from the slag. Operating under a slagging regime has higher costs compared to dry ash, such as increased oxygen usage associated with higher operating temperatures, shortened refractory life, and increased risk of plugging.

[0008] Recovering metals from slag is expensive and inefficient, as it requires extraction of the slag from the system, followed by additional processing steps to recover the metals from the slag. Typically, operating under a slagging regime also requires the addition of fluxes to control the flow properties of the slag. Dry ash is preferred because it prevents the metal ash particles from combining and forming alloys, improving downstream metal recovery from non-alloyed solid metal particles.

[0009] However, dry ash handling presents significant challenges for feedstocks with high ash content. The bottom quench process is water intensive, and therefore requires a recycle process water stream. Without recycle, hundreds or even thousands of tons of water per day would be required for a typical scale gasification process. The high loading of carbon-coated metal ash particles increases the risk of plugging in the recycle of process water. Gilmer (US 4,705,542) teaches that solids must be removed in order to recycle water to the bottom quench process.

[0010] Solids present a clear risk of plugging, but the compounds present in a gasification with a high metal ash content residue stream present an additional risk of solids precipitating from downstream reactions. Salts and acid gases generated in the gasifier dissolve in the process water. Different process water streams will accumulate more salt or acid gas depending on the unit operations they undergo. The acid gas rich process water stream and the salt rich process water stream do not present a risk of plugging individually, but can precipitate as solids when mixed prior to recycle to the bottom quench. There is an industrial need to maximize the internal recycle of process water streams while minimizing the risk of plugging. SUMMARY

[0011] The present disclosure relates to a method that can gasify a residue stream comprising liquid hydrocarbons and metal rich solid particles, where the metal rich solid particles comprise one or more metal components such as vanadium, nickel, iron, magnesium, aluminum, molybdenum, zinc, lead, tin, sodium, potassium, and calcium; non-metal components such as phosphorous, silicon, and organic halides; and solid carbon formed in a refinery residue upgrading process. Catalyst particles can be present in the liquid hydrocarbon matrix and / or as solid particles. Some of the metal components that were catalysts in the upstream process are carbon-coated, such as coke particles, as a result of the gasification process.

[0012] To reduce the risk of plugging in the water lines, solids are removed from the recycled water by filtration or evaporation and condensation. In addition, acid gases are stripped from at least a portion of the recycled water in order to reduce the risk of precipitation by reaction of acid gases, such as carbon dioxide, with metal ions present in the process water streams, such as calcium, to produce solid calcium carbonate.

[0013] In at least some embodiments, the method allows the gasifier to operate at a lower carbon to ash ratio than the SEC technology, which both reduces the solids loading in the solids removal system and increases the conversion of hydrocarbons in the feedstock to syngas.

[0014] Aspect 1 : A method for gasifying a residue stream comprising liquid hydrocarbons and metal-rich solid particles, the method comprising reacting the residue stream with an oxidant stream in a gasifier to produce a hot synthesis gas stream comprising carbon monoxide, hydrogen, and soot; contacting the hot synthesis gas stream with a quench water stream to produce a quenched synthesis gas stream and a water bath in the gasifier; removing a soot-containing quenched water stream from the water bath; washing the quenched synthesis gas stream with a scrubber water stream to produce a raw synthesis gas stream and a soot water stream; separating the soot-containing quenched water stream and at least a portion of the soot water stream to produce one or more overhead vapor streams and a concentrated soot water stream; filtering the concentrated soot water stream to produce a solid filter cake and a liquid filtrate stream; separating at least a portion of the liquid filtrate stream to form a primary filtrate fraction; stripping a first acid gas stream from the primary filtrate fraction to produce a stripped water stream, wherein the quench water stream comprises at least one of at least a portion of the stripped water stream and at least a portion of the liquid filtrate stream.

[0015] Aspect 2: The method of aspect 1, further comprising the step of separating at least a portion of the quenched water stream to form the scrubber water stream.

[0016] Aspect 3: The method of aspect 1 or aspect 2, wherein the step of washing the quenched synthesis gas stream comprises separating the quenched synthesis gas stream to produce a soot water stream and an intermediate synthesis gas stream; washing the intermediate synthesis gas stream with a scrubber water stream to produce a raw synthesis gas stream and a recycled soot water stream; separating at least a portion of the recycled soot water stream to form a first recycled soot water fraction; and washing the quenched synthesis gas stream with the first recycled soot water fraction prior to separation into the intermediate synthesis gas stream and the soot water stream.

[0017] Aspect 4: The method of aspect 3, further comprising the steps of separating at least a portion of the recycled soot water stream to form a second recycled soot water fraction; and washing the intermediate synthesis gas stream with the second recycled soot water fraction.

[0018] Aspect 5: The method of any one of aspects 1 to 4, further comprising the steps of separating at least a portion of the liquid filtrate stream to form a wash filtrate fraction; and washing the quenched synthesis gas stream with the wash filtrate fraction prior to separation into the intermediate synthesis gas stream and the soot water stream.

[0019] Aspect 6: The method of any one of aspects 1 to 5, further comprising the steps of separating at least a portion of the filtrate stream to form a heat exchange filtrate fraction; transferring heat from one or more of the following streams to the heat exchange filtrate fraction: one or more of the overhead vapor streams and the concentrated soot water stream; and combining the heat exchange filtrate fraction with at least a portion of the stripped water stream.

[0020] Aspect 7: The method of aspect 6, further comprising partially condensing one or more overhead vapor streams to produce one or more partially condensed overhead streams; and stripping the second acid gas stream from one or more partially condensed overhead streams.

[0021] Aspect 8: The method of any one of aspects 1-7, further comprising the step of separating at least a portion of the soot water stream to form a second soot water fraction and feeding the second soot water fraction to the water bath.

[0022] Aspect 9: The method of any one of aspects 1-8, wherein the gasifier is operated under a non-slagging regime.

[0023] Aspect 10: The method of any one of aspects 1-9, further comprising the step of combining a boiler feed water stream with at least a portion of the stripped water stream.

[0024] Aspect 11 : The method of any one of aspects 1-10, wherein the solid filter cake comprises non-alloyed solid metal particles.

[0025] Aspect 12: The method of any one of aspects 1-11, wherein a residence time of the residue stream in the gasifier is between 10 seconds and 30 seconds.

[0026] Aspect 13: The method of any one of aspects 1-12, wherein the soot comprises a carbon fraction and a metal fraction, and a ratio of a weight of the carbon fraction divided by a weight of the metal fraction is between 1 and 2.

[0027] Aspect 14: A method for gasifying a residue stream comprising liquid hydrocarbons and metal-rich solid particles, the method comprising reacting the residue stream with an oxidant stream in a gasifier to produce a hot synthesis gas stream comprising carbon monoxide, hydrogen, and soot; contacting the hot synthesis gas stream with a quench water stream to produce a quenched synthesis gas stream and a soot-laden quench water stream; washing the quenched synthesis gas stream with a scrubber water stream to produce a raw synthesis gas stream and a soot water stream, wherein the quench water stream comprises at least a portion of one or more of: the soot-laden quench water stream, a stream derived from the soot-laden quench water stream, the soot water stream, and a stream derived from the soot water stream; and wherein the raw synthesis gas comprises 40-50% water by volume.

[0028] Aspect 15: The method of aspect 14, wherein the scrubber water stream comprises at least a portion of one or more of: the soot-laden quench water stream, a stream derived from the soot-laden quench water stream, the soot water stream, and a stream derived from the soot water stream.

[0029] Aspect 16: An apparatus for gasifying a residue stream comprising liquid hydrocarbons and metal-rich solid particles, the apparatus comprising a gasifier configured to receive the residue stream and an oxidant stream and produce a quenched syngas stream, the gasifier comprising a quench water inlet and a water bath in fluid communication with the quenched syngas stream; a soot removal system in fluid flow communication with the gasifier, the soot removal system configured to receive the quenched syngas stream from the gasifier and a scrubber water stream to produce a soot water stream and a raw syngas stream; a flash system comprising one or more liquid-vapor separators in fluid flow communication with the water bath and the soot removal system, the flash system configured to receive a soot-laden quenched water stream from the water bath and at least a portion of the soot water stream from the soot removal system to produce one or more partially condensed overhead streams and a concentrated soot stream; a wastewater stripping system in fluid flow communication with the flash system, the wastewater stripping system configured to receive one or more partially condensed overhead streams and produce an acid gas stream and a stripped water stream; and a filtration unit configured to receive the concentrated soot stream and produce a solid filter cake and a liquid filtrate stream, wherein the water bath is configured to receive at least a portion of the stripped water stream and / or at least a portion of the liquid filtrate stream from the wastewater stripping system.

[0030] Aspect 17: The apparatus of Aspect 16, further comprising a metal recovery system configured to receive the solid filter cake from the filter and produce a metal-rich fraction and a metal-lean fraction.

[0031] Aspect 18: The apparatus of Aspect 16 or Aspect 17, wherein the soot removal system comprises a soot separator in fluid flow communication with the gasifier and a soot scrubber in fluid flow communication with the soot separator; wherein the soot separator is configured to receive the quenched syngas stream to produce the soot water stream and an intermediate syngas stream; and wherein the soot scrubber is configured to receive the intermediate syngas stream and the scrubber water stream to produce the raw syngas stream.

[0032] Aspect 19: The apparatus of any one of Aspects 16-18, wherein the soot removal system further comprises a quench tube in fluid flow communication with the gasifier and the soot separator; and wherein the quench tube is configured to receive the quenched syngas stream and at least a portion of the liquid filtrate stream. BRIEF DESCRIPTION OF DRAWINGS

[0033] The present disclosure will be described below with reference to the accompanying drawings, in which like numerals indicate like elements:

[0034] Figure 1 is a diagram depicting an embodiment of a gasification process in which acid gases and solids are removed from soot water to allow recycling to the gasifier.

[0035] Figure 2is a drawing depicting an embodiment of a gasification process having a flash system including a single flash vessel. DETAILED DESCRIPTION

[0036] The following detailed description is provided to enable those in the art to make and use exemplary embodiments of the application. Various modifications, however, will be readily apparent to those skilled in the art, and the generic principles described herein can be applied to other embodiments without departing from the spirit or scope of the application as set forth in the appended claims.

[0037] The articles "a" and "an" as used in this application and the appended claims should not be construed as excluding the plural. Furthermore, to the extent that the terms "include", "has", "has" and "have", "including", and / or "comprising" are used in either the detailed description and / or the claims, such terms are intended to be inclusive in a manner similar to the term "comprising" as an open transition term without precluding any additional or

[0038] The term "and / or", placed between a first entity and a second entity, includes any of the following meanings: (1) the first entity alone, (2) the second entity alone, or (3) both the first entity and the second entity. The term "and / or" placed between the last two entities of a list of three or more entities means at least one of the entities in the list, including any specific combination of the entities in the list. For example, "A, B, and / or C" has the same meaning as "A and / or B and / or C" and includes the following combinations of A, B, and C: (1) A alone, (2) B alone, (3) C alone, (4) A and B but not C, (5) A and C but not B, (6) B and C but not A, and (7) A and B and C.

[0039] The adjective "any" means one, some, or all, without regard to number.

[0040] The phrase "at least a portion" means "a portion or all". "At least a portion of a stream" has the same composition as the stream from which it came, with the same concentration of each species.

[0041] As used herein, "first", "second", "third", etc. are used to distinguish steps and / or features, and do not indicate relative position or time and / or space, unless so explicitly stated.

[0042] All compositional values will be specified in mole percent for the gas phase and weight percent for the solid and liquid phases.

[0043] The term "depleted" or "depletion" means the indicated component is at a lower molar percent concentration than the original stream from which the indicated component was formed. Depleted and depletion do not mean that the stream is completely devoid of the indicated component.

[0044] The term "enriched" or "enrichment" means the indicated component is at a higher molar percent concentration than the original stream from which the indicated component was formed.

[0045] "Downstream" and "upstream" refer to the intended flow direction of the process fluid being conveyed. If the intended flow direction of the process fluid is from a first device to a second device, the second device is downstream of the first device. In the case of a recycle stream, downstream and upstream refer to the first pass of the process fluid.

[0046] The term "indirect heat exchange" refers to the process of transferring sensible and / or latent heat between two or more fluids without physical contact of the fluids in question with each other. The heat can be transferred through the walls of a heat exchanger or by the use of an intermediate heat transfer fluid. The term "hot stream" refers to any stream that leaves a heat exchanger at a lower temperature than it entered. Conversely, a "cold stream" refers to a stream that leaves a heat exchanger at a higher temperature than it entered.

[0047] Figure 1 An embodiment of a system 1 for reacting a residual stream 10 comprising liquid hydrocarbons and metal ash with an oxidant stream 15 in a gasifier G is shown. A feed oil surge vessel (not shown) can optionally be used to eliminate any surges in the line and to meet demand spikes. The feed oil surge vessel can be heated by a heating coil to maintain the temperature of the feed in the event of gasifier start-up and shut-down. A spare feed oil filter (not shown) can be installed in the low pressure distribution system to remove larger particles prior to the burners. The oxidant stream 15 can be a gas stream comprising pure oxygen, oxygen enriched air, or air. The oxidant stream 15 can also include steam to act as a moderator, which reduces the severity of the strongly exothermic oxidation reaction.

[0048] One of the main components of the gasifier G is the burner. One or more lift flame burners can be located at the top of each gasifier, burning downward (not shown). Each lift flame burner comprises a co-annular burner with an additional moderator lift channel. The assembled burner has an exit opening comprising the co-annular channel and is surrounded by a water-cooled burner cylinder. The burner must be cooled to prevent overheating and damage due to the severe gasification conditions. The burner cylinder is cooled with high pressure cooling water from a burner cooling water system. The cooling water can be maintained at a pressure higher than the operating pressure in the gasifier G to prevent leakage of syngas into the burner cooling water system in the event of burner cylinder failure and to prevent syngas from being undesirably blown out to the atmosphere. The temperature of the cooling water is typically maintained above the dew point of the raw syngas to prevent dew point corrosion of the burner cylinder.

[0049] The gasification process is typically a non-catalytic and auto-thermal process in which the feedstock is partially oxidized with oxygen and steam to produce hot synthesis gas (mainly comprising CO and H2). The pressure is typically in the range of 10-100 bar and the residence time is typically in the range of 10 to 30 seconds. In one embodiment, the process temperature (intermediate temperature in the reactor) is kept below the ash fusion temperature, which is sufficient to meet the required feedstock conversion. The ash fusion temperature is a complex function of the composition of the ash, but for most residue feedstocks, operation above 1500°C is in the slagging regime. A small amount of soot, including unconverted carbon and metallic ash, is produced in the gasifier G. The gasifier G operates in the non-slagging regime, where the metallic ash is in the form of dry ash, rather than liquid slag.

[0050] The gasifier G can comprise a top refractory lined reactor section in which the high temperature partial oxidation reaction takes place; and a lower bottom quench section containing a water bath in which the first step of synthesis gas cooling and bulk soot removal takes place. The partial soot is scrubbed from the hot synthesis gas in this bottom quench and is removed in a soot-laden quench water stream 30 through a liquid outlet at the bottom of the water bath.

[0051] The hot synthesis gas leaving the bottom of the top reactor section is directed downward through the bottom quench section, in which the hot synthesis gas is cooled by passing through a water bath. The water bath is fed by a quench water stream 20, which can include any of the following: preheated recirculated filtrate, recirculated water from a wastewater stripping system (WWS), process condensate from sources such as a sulfur recovery unit, acid gas removal unit or knock-out separator from a downstream sour shift unit, boiler feed water and make-up water. If steam is used to preheat the oxidant stream 15, the resulting condensate can also be fed to the water bath.

[0052] The quenched synthesis gas stream 25 exits the bottom quench section and enters the soot removal system SRS. In the SRS, the synthesis gas stream 25 is cooled further and the remaining soot is removed. Figure 1In this case, this is shown as a two-stage water wash. In the first stage, the syngas enters a quench tube Q, where the syngas is further scrubbed and cooled by a series of water sprays. The water can be supplied from two separate sources: a wash filtrate fraction 40 from the filtration unit F and a first recycled soot water fraction 45 from the soot scrubber S. A second quenched syngas stream 50 exits the quench tube Q and enters a soot separator V1, where the second quenched syngas stream 50 is separated into a soot water stream 60 and an intermediate syngas stream 55. The soot water stream 60 includes solid particles from the second quenched syngas stream 50. At least a portion of the soot water stream 60 is directed to the flash system FS as a first soot water fraction 62. At least a portion of the soot water stream 60 can be partially recycled back into the gasifier water bath as a second soot water fraction 65 by a recycle pump. The second soot water fraction can be fed to the gasifier water bath in such a way as to promote turbulent flow and prevent the settling of solids within the bath, which can cause fouling and / or plugging of the equipment.

[0053] Capturing and cooling the ash in the gasifier water bath eliminates the tortuous cooling path of the SEC technology, reducing the carbon-to-ash ratio required to prevent fouling. The carbon-to-ash ratio required to prevent fouling is between 1 and 2, as compared to values between 4 and 6 in the SEC technology.

[0054] The intermediate syngas stream 55 is conveyed to the soot scrubber S, where remaining solids are removed to meet syngas solids specifications, producing a raw syngas stream 85, which is directed to the boundary of the system 1. A scrubber water stream 70 is typically fed to the soot scrubber S countercurrent to the intermediate syngas stream 55. A recycled soot water stream 75 exits the bottom of the soot scrubber S and is pumped. At least a portion of the recycled soot water stream 75 can be fed to the quench tube Q as a first recycled soot water fraction 45. At least a portion of the recycled soot water stream 75 can be fed to the soot scrubber S as a second recycled soot water fraction 80 to remove fine particles.

[0055] When the degree of solids removal required is low, then Figure 1 The depicted quench tube Q can be removed, and the quenched syngas stream 25 can be fed directly to the soot separator V1.

[0056] The soot-laden quench water stream 30 exiting the water bath in the gasifier G and the first soot water fraction 62 are fed to the flash system FS. The flash system FS can include any number and type of liquid-vapor separators, including a flash vessel or a flash column. In Figure 1In this embodiment, the flash system FS includes two flash vessels, a high pressure flash vessel V2 and a low pressure flash vessel V3. The ash-laden quench water stream 30 exiting the water bath in the gasifier G and the first ash water fraction 62 are combined and fed to the high pressure flash vessel V2 and are separated into a first overhead stream 90 and a first liquid stream 95. The first liquid stream 95 is reduced in pressure and sent to the low pressure flash vessel V3 where it is separated into a second overhead stream 100 and a concentrated ash water stream 105. The concentrated ash water stream 105 is then sent to the filtration unit F where solids are removed, for example as a solid filter cake 150, leaving a liquid filtrate stream 155. The liquid filtrate stream 155 can then be split into a primary filtrate fraction 175, which can be sent to the wastewater stripping system WWS; a wash filtrate fraction 156, which can optionally be pumped prior to being fed to the quench tube Q; and a heat exchange filtrate fraction 160, which can be preheated and recycled to the water buffer vessel B. The use of the water buffer vessel B can allow for increased reaction time in the event of a disturbance. Make-up water 180 can optionally be added to the water buffer vessel B, and in at least some embodiments, can be controlled to balance any water fluctuations in the system, particularly in the event of equipment failure. The make-up water 180 can include boiler feed water. Improved recycling of water to the water buffer vessel B reduces the amount of make-up water 180 required.

[0057] Thermal integration is a key element of at least some embodiments of the present disclosure, as downstream processing of the synthesis gas is optimized when the temperature of the raw synthesis gas stream 85 is maximized. One potential downstream application that requires a high temperature raw synthesis gas is the sour shift unit, as this allows for a higher water content in the raw synthesis gas, which in turn reduces the steam demand in the sour shift unit. The water content of the raw synthesis gas stream 85 in the present disclosure is typically in the range of about 40-50% by volume, compared to 0-5% in prior art SEC technology. Thermal integration maximizes the temperature and water content of the raw synthesis gas product. Both of these characteristics improve the efficiency of the reforming process when the downstream use of the raw synthesis gas product is hydrogen production, for example by reducing the addition of superheated steam in the downstream water gas shift reaction. The temperature of the raw synthesis gas stream 85 can be increased by preheating the water stream used to quench the gasifier G and / or the ash removal system SRS. In the present disclosure, the first overhead stream 90 and the second overhead stream 100 contain a significant amount of heat that can be recovered through indirect heat exchange with the heat exchange filtrate fraction 160. The first overhead stream 90 and the second overhead stream 100 can be partially condensed to produce a first partially condensed overhead stream 110 and a second partially condensed overhead stream 115.

[0058] In at least some embodiments, acid gases must be removed from the process water stream to prevent gases such as carbon dioxide and hydrogen sulfide from reacting with metal ions such as calcium and nickel to form solid precipitates such as calcium carbonate or nickel sulfide, which can clog the system. The first portion condensed overhead stream 110 and the second portion condensed overhead stream 115 are fed to a wastewater stripping system WWS. The wastewater stripping system WWS can include any number of flash vessels and / or flash towers, the function of which is to produce a concentrated acid gas stream 132. In Figure 1 In the example embodiment shown, the wastewater stripping system WWS includes a flash gas separator V4 that receives the first portion condensed overhead stream 110 and the second portion condensed overhead stream 115, and a wastewater stripping tower W that receives the wastewater stream 125 from the bottom of the flash gas separator V4. The wastewater stripping tower W can be stripped with steam or any other suitable gas, for example in a countercurrent arrangement. The stripped water stream 135 can then be recycled to the water buffer vessel B. At least a portion of the stripped water stream 135 can be split into a purge water stream 137 and sent to a boundary zone for further processing to limit the accumulation of trace components in the water circuit. The heat introduced to the wastewater stripping tower W to remove acid gases can additionally preheat the stripped water stream 135. In at least some embodiments, preheating the stripped water stream 135 can be beneficial to maximize the temperature of the raw syngas stream 85. The primary filtrate fraction 175 can be fed to the wastewater stripping system WWS at any location configured to accept a liquid stream. In Figure 1 Two alternative embodiments are shown in which the primary filtrate fraction 175 is combined with the wastewater stream 125 and in which the primary filtrate fraction 175A is fed directly to the flash gas separator V4. The acid gas stream 120 exiting the flash gas separator V4 and the acid gas stream 130 exiting the wastewater stripping tower W can be disposed of separately or combined to form a concentrated acid gas stream 132.

[0059] The concentrated soot water stream 105 contains carbon and ash solids, which are removed in a filtration unit F. The filtration unit F can include any number of solid removal stages, for example membrane filter presses. The filtrate from the filtration step can be collected in a filtrate buffer vessel B. The filtrate buffer vessel B can be configured to accept a liquid stream from any location in the system. In Figure 1The produced solid filter cake 150 can then be fed to a metal recovery system MR, where a metal-rich fraction 185 (including, for example, but not limited to, molybdenum, vanadium, and / or nickel) is separated from a metal-lean fraction 190. Recovery of the metal-rich fraction is easier when the gasifier G is operated under non-slagging regime, as compared to a gasifier under a slagging regime, where the metal would be captured in a phase rich in glassy oxides. The metal recovery system MR can utilize any technology known in the art suitable for recovery of the metal of interest, for example, a multi-hearth furnace, where the carbon is burned off from the solid filter cake 150. In the case where the metal recovery system MR is a multi-hearth furnace, the metal-rich fraction 185 can be a metal-rich ash, and the metal-lean fraction 190 can be flue gas.

[0060] Figure 2 An embodiment of the gasification system 2 is shown, where the flash system FS includes a single high-pressure flash vessel V2. The first overhead stream 90 is sent directly to the wastewater stripping system. The concentrated sootwater stream 105 leaving the bottom of the high-pressure flash vessel V2 is preheated by indirect heat exchange against the hot exchange filtrate fraction 160. Similar to the concentrated sootwater stream 105 in Figure 1 The cooled concentrated sootwater stream 107 is sent to the filtration unit F, similar to the concentrated sootwater stream 105 in

[0061] While the principles of this application have been described above in connection with preferred embodiments, it is to be clearly understood that this description is made only by way of example and not as a limitation of the scope of the application.

Claims

1. A method for gasifying a residual stream, the residual stream comprising liquid hydrocarbons and metal-rich solid particles, the method comprising: The residual stream is reacted with the oxidant stream in a gasifier to produce a thermal synthesis gas stream comprising carbon monoxide, hydrogen, and soot. The hot synthesis gas stream is brought into contact with a quenched water stream from a water buffer container to generate a quenched synthesis gas stream and a water bath in the vaporizer. Remove the quenched water containing soot from the water bath; The quenched synthesis gas stream is washed with a scrubbing water stream to produce a coarse synthesis gas stream and a soot water stream; Separate the quenched water stream containing soot and at least a portion of the soot water stream to generate one or more overhead steam streams and concentrated soot water streams; The concentrated soot water stream is filtered to produce a solid filter cake and a liquid filtrate stream; At least a portion of the liquid filtrate stream is separated to form a primary filtrate fraction and a heat exchange filtrate fraction; The first acidic gas stream is stripped from the primary filtrate fraction to produce a stripped water stream, and at least a portion of the stripped water stream is recycled back to the water buffer container. The heat exchange filtrate is preheated and then recycled back to the water buffer container.

2. The method of claim 1, further comprising the step of separating at least a portion of the quenched water flow to form the washer water flow.

3. The method of claim 1, wherein the step of washing the quenched synthesis gas stream comprises the following steps: The quenched synthesis gas stream is separated to generate the soot water stream and the intermediate synthesis gas stream; The intermediate synthesis gas stream is washed with the scrubber water stream to produce a coarse synthesis gas stream and a recirculated soot water stream; At least a portion of the recirculated soot water stream is separated to form a first recirculated soot water fraction; and Before being separated into intermediate synthesis gas stream and soot water stream, the quenched synthesis gas stream is washed with the first recirculated soot water fraction.

4. The method according to claim 3, further comprising the following steps: At least a portion of the recirculated soot water stream is separated to form a second recirculated soot water fraction; and The intermediate synthesis gas stream is washed with the second recirculated soot water stage.

5. The method according to claim 1, further comprising the following step: At least a portion of the liquid filtrate stream is separated to form a washing filtrate fraction; and Before separating into intermediate synthesis gas stream and soot water stream, the quenched synthesis gas stream is washed in stages with the washing filtrate.

6. The method according to claim 1, further comprising the following step: Heat is transferred to the heat exchange filtrate fraction from one or more of the following streams: one or more overhead steam streams and the concentrated flue gas stream.

7. The method according to claim 6, further comprising: Partially condense one or more overhead vapor streams to produce one or more partially condensed overhead streams; and A second acidic gas stream is stripped from the overhead stream of one or more partially condensed components.

8. The method of claim 1, further comprising the steps of separating at least a portion of the flue water flow to form a second flue water fraction and feeding the second flue water fraction into the water bath.

9. The method according to claim 1, wherein the gasifier operates under a non-slagging regime.

10. The method of claim 1, further comprising the step of adding boiler feed water flow to the water buffer container.

11. The method of claim 1, wherein the solid filter cake comprises unalloyed solid metal particles.

12. The method of claim 1, wherein the residence time of the residual stream in the vaporizer is between 10 seconds and 30 seconds.

13. The method of claim 1, wherein the soot comprises carbon fractions and metal fractions, and the ratio of the weight of the carbon fractions to the weight of the metal fractions is between 1 and 2.

14. An apparatus for gasifying a residual stream, the residual stream comprising liquid hydrocarbons and metal-rich solid particles, the apparatus comprising: A vaporizer configured to receive a residual stream and an oxidant stream and generate a quenched synthesis stream, the vaporizer including a quenched water inlet and a water bath in fluid communication with the quenched synthesis stream; A soot removal system in fluid communication with the gasifier, the soot removal system being configured to receive the quenched synthesis gas stream and scrubber water stream from the gasifier to generate a soot water stream and a coarse synthesis gas stream; A flash evaporation system, comprising one or more liquid-vapor separators in fluid flow communication with the water bath and the soot removal system, the flash evaporation system being configured to receive a soot-containing quenched water stream from the water bath and at least a portion of the soot-water stream from the soot removal system to produce one or more partially condensed overhead streams and concentrated soot streams. A wastewater stripping system is in fluid communication with the flash evaporation system, the wastewater stripping system being configured to receive one or more partially condensed overhead streams and generate an acidic gas stream and a stripped water stream; A filtration unit configured to receive the concentrated soot stream and produce a solid filter cake and a liquid filtrate stream, wherein at least a portion of the liquid filtrate stream is separated to form a primary filtrate fraction and a heat exchange filtrate fraction, the primary filtrate fraction being sent to the wastewater stripping system; and A water buffer container is provided, in which at least a portion of the stripped water from the wastewater stripping system is recycled, and the heat exchange filtrate fraction is preheated and recycled back to the water buffer container. The water bath is configured to receive a quenched water flow from the water buffer container.

15. The apparatus of claim 14, further comprising a metal recovery system configured to receive the solid filter cake from the filter and produce a metal-rich fraction and a metal-poor fraction.

16. The apparatus of claim 14, wherein the soot removal system comprises a soot separator in fluid communication with the gasifier and a soot scrubber in fluid communication with the soot separator; The soot separator is configured to receive the quenched synthesis gas flow to generate the soot water flow and the intermediate synthesis gas flow; and The soot scrubber is configured to receive the intermediate synthetic gas flow and the scrubber water flow to generate the coarse synthetic gas flow.

17. The apparatus of claim 16, wherein the soot removal system further comprises a quenching pipe in fluid communication with the gasifier and the soot separator; and The quench tube is configured to receive the quenched synthetic gas stream and at least a portion of the liquid filtrate stream.

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