Methods for removing suspended solids from black liquor

Abstract

Systems, devices, and methods for the removal of suspended solids from pulp liquor prior to concentration via a black liquor concentration system comprising graphene oxide membranes are described herein. The systems, devices and methods disclosed herein enable removal of suspended solids from black liquor through flocculation followed by floc removal. Selected flocculants preferentially bind to cellulose fibers and can operate at high temperature (>90 °C), pH (>13) and amount of total suspended solids (TSS, 15-1000 ppm) leading to the selective flocculation of suspended solids in black liquor. The flocculation process can involve coagulation and the addition of multiple flocculants which optimize suspended solids removal and cost.

Description

Agent’s File Ref. VSLC-014 / 01WO 331287-2099SYSTEMS AND METHODS FOR REMOVING SUSPENDED SOLIDS FROM BLACK LIQUORCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 718,982, entitled “Systems and Methods for Removing Suspended Solids from Black Liquor,” filed November 11, 2024, the disclosure of which is incorporated by reference herein in its entirety.TECHNICAL FIELD

[0002] The present disclosure relates to systems and methods for concentrating black liquor solutions produced by pulp and paper mills, and more specifically to systems and methods for removing suspended solids from black liquor solutions using flocculation processes at elevated pH and temperatures.GOVERNMENT SUPPORT

[0003] This invention was made with U.S. government support under Grant No. DE- AR0001686 awarded by the Department of Energy. The U.S. government has certain rights in the invention.BACKGROUND

[0004] Black liquor is a byproduct of the pulping industry generated during digestion of pulpwood to produce cellulose fibers for pulp and paper products. Black liquor contains the residual pulping residues including fibers, lignin, hemicellulose, inorganic chemicals from the kraft process such as sodium hydroxide and / or sodium sulfate, as well as other extractives contained in the wood such as tall oil suspended and / or dissolved in water. Systems and methods for processing black liquor may include the use pressure driven filtration systems and / or devices (e.g., filtration membranes) designed to remove and / or separate water from the black liquor, increasing the solids content in the black liquor from 7-15% to 65-80%. The water removed from the black liquor can be recirculated to the plant, while the high solids content black liquor can be burned in a recovery boiler or similar style boiler to generate steam, providing energy to the pulp mill, and recovering the chemicals used in the cooking process. The use of filtration membranes to remove suspended solids such as fibers and high molecular1326750747Agent’s File Ref. VSLC-014 / 01WO 331287-2099 weight species (e.g., lignin and cellulose) from black liquor can cause membrane fouling resulting in reduced filtration performance and / or reduced lifetime. Suspended solids can be removed from black liquor by various techniques, including nanofiltration and ultrafiltration. However, nanofiltration and ultrafiltration membranes operate at elevated pressure, and require extensive cleaning, resulting in low efficiency and high cost. Consequently, there is a need in the art for new systems and methods for processing black liquor that address the shortcomings of current methods to remove suspended solids and provide a pathway to cost reduction and higher efficiency mill operation.SUMMARY

[0005] Systems and methods for concentrating black liquor solutions produced by pulp and paper mills via flocculation and floc removal are described herein. In some embodiments, a method comprises: receiving at a flocculation unit a black liquor feed. The black liquor feed being characterized by a first amount of total suspended solids (TSS), a first temperature, and a pH. The method further comprises flocculating suspended solids included in the black liquor feed to produce a flocculated black liquor feed; directing the flocculated black liquor feed to a floc removal unit disposed downstream of the flocculation unit; and separating, at the floc removal unit and from the flocculated black liquor feed, a floc containing at least a portion of the suspended solids, to produce a conditioned black liquor feed. The conditioned black liquor feed being characterized by a second amount of total suspended solids (TSS) of no more than about 5 ppm. Lastly, the method further comprises directing the conditioned black liquor feed to a Graphene Oxide (GO) membrane filtration system.BRIEF DESCRIPTION OF THE DRAWINGS

[0006] FIG. 1 illustrates a plot of a pressure gradient or differential pressure (DP) between the inlet and outlet of a filtration membrane caused by fouling due to exposure to suspended solids.

[0007] FIG. 2 schematically illustrates an example system for removing suspended solids from a black liquor feed via flocculation and floc removal, according to an embodiment.

[0008] FIGS. 3 A-3E illustrate the chemical structures of example flocculants employed for the removal of suspended solids from black liquor, according to embodiments of the present disclosure.2326750747Agent’s File Ref. VSLC-014 / 01WO 331287-2099

[0009] FIG. 4 is a schematic illustration of a flocculation unit that integrates a heat exchanger and a flocculation device for processing a black liquor feed, according to an embodiment.|0010[ FIG. 5 illustrates an example method for removing suspended solids from a black liquor feed by flocculation, according to an embodiment.DETAILED DESCRIPTION[0011 | Black liquor is a byproduct of the kraft pulping process, generated during conversion of wood into cellulose fibers for pulp and paper products. Black Liquor produced in pulp mills can contain sodium sulfate, sodium carbonate, sodium hydrosulfide, sodium thiosulfate, and / or sodium hydroxide, residual fibers from the pulping process, as well as larger size (e.g., high molecular weight) organic species including hemicellulose, cellulose, and lignin, among others. In some instances, black liquor streams can have a total concentration of solids in the range of approximately 7 to 20 wt.%. Existing methods and / or approaches for treatment of black liquor streams typically consists of feeding the black liquor into a series of thermal evaporators to remove water until the solids content in the black liquor is increased to about 65 to 80 wt.%. The black liquor with high solids content is then fed into a recovery boiler to generate steam and recover the pulping chemicals used during the kraft process. The evaporated water is condensed and recycled for future use within the mill. This method and / or approach to process black liquor is energy intensive, and accounts for approximately 30% of the overall kraft mill energy consumption. Alternative methods for treatment of black liquor include the use of pressure driven membrane filtration systems. In particular, filtration systems that incorporate graphene oxide (GO) membranes capable of operating with black liquor at elevated temperatures and pH. These systems can be up to 90% more energy efficient than thermal evaporators, since separation of species via a membrane eliminates the need for a liquid to vapor phase transition required in thermal evaporators. Consequently, the use of pressure driven membranes for processing black liquor provides an opportunity for costs savings to mills through reductions in energy usage and / or consumption.

[0012] Despite the increased energy efficiency of pressure driven membranes for the processing of black liquor, their widespread implementation may be limited due to membrane degradation and / or fouling caused by exposure of the membranes to high concentrations of solids suspended in the black liquor. Suspended solids present in black liquor streams can foul membranes, resulting in a loss of flux, a loss of rejection, and / or the development of a pressure3326750747Agent’s File Ref. VSLC-014 / 01WO 331287-2099 gradient between the inlet and the outlet of the membrane, which can severely reduce the membrane’s filtration performance and lifetime. For example, FIG. 1 presents a plot of a pressure gradient or differential pressure (DP) between the inlet and outlet of a module containing three filtration membranes in series as a function of time caused by fouling due to exposure to suspended solids. Exposure of filtration membranes to high aspect ratio solids, such as fibers included in the black liquor, can present a particularly high fouling risk due to their ability to entangle inside membrane module components. High aspect ratio materials are also difficult to remove due to their small diameter (down to 10 pm) and ability to reptate through the pores of many conventional filters. Suspended solids can get caught in the feed spacers of spiral wound modules, deposit on, foul, or scratch the surface of the filtration membrane, or clog / foul equipment and inlets to membrane modules.

[0013] Suspended solids can be removed from black liquor by various techniques, including the use of nanofiltration and ultrafiltration membranes. These membranes exist in various form factors, including tubular and hollow fiber modules. While nanofiltration and ultrafiltration membranes can be used to remove at least a portion and / or fraction of the suspended solids present in black liquor, their implementation introduces a considerably high upfront cost, requires elevated operating pressures and frequent / extensive cleaning, ultimately reducing the overall energy efficiency of the process. Consequently, the use of nanofiltration and ultrafiltration membranes to remove suspended solids and precondition black liquor for downstream concentration in pressure driven filtration systems remains limited. Alternative approaches to remove suspended solids from black liquor include subjecting the black liquor to a coagulation and / or a flocculation process. Coagulation and / or flocculation, followed by floc removal are processes designed to remove suspended solid particles from a liquid stream. One of the most common applications of coagulation and / or flocculation processes includes the treatment of groundwater and surface water for human consumption (e.g., drinking water).|0014] The suspended solids comprise solid particles characterized by a relatively small average particle size (which facilitates keeping the solid particles in suspension), and a negative charge that prevents the solid particles from coming together. During coagulation, one or more coagulant chemical(s) are added to neutralize the negative charge of the suspended particles, facilitating the formation of slightly larger particle (e.g., micro flocs) which are not visible to the naked eye. Flocculation is frequently used in tandem with coagulation to agglomerate the micro flocs produced during coagulation. During flocculation, one or more flocculants are4326750747Agent’s File Ref. VSLC-014 / 01WO 331287-2099 added to agglomerate the micro flocs and produce much larger size flocs that can then be removed and / or separated via sedimentation, centrifugation, and / or other suitable approach.

[0015] Current coagulation and flocculation methods for processing black liquor require operating at moderate temperatures (e.g., 25-35 °C) and low pH, in order to successfully separate and / or remove the suspended solids included in the black liquor. High temperatures (65-95 °C), high pH (pH > 10), high solids content (6-18%), lignin concentration, and salinity of black liquor can cause many flocculants to either fail forming flocs; or fail forming flocs that are large enough such that they can be effectively removed, or selectively flocculate the suspended solids. Some flocculants can flocculate the suspended solids, but only after reducing the black liquor temperature, or after chemically modifying the black liquor feed (e.g., pH reduction). The need for moderate processing temperatures and low pH in order to remove a high percentage of the suspended solids present in the black liquor leads to a considerable reduction in the overall energy efficiency of the process and an increased plant complexity. Consequently, the implementation of existing black liquor coagulation and flocculation processes at an industrial scale has been limited. The present disclosure provides systems and methods for the removal of suspended solids (including high aspect ratio materials such as fibers) present in black liquor via flocculation and removal of floc, addressing the limitations and / or shortcomings of the prior art, and producing preconditioned black liquor streams that can be further concentrated in pressure driven filtration systems that include graphene oxide membranes. In particular, the systems and methods disclosed herein facilitate processing black liquor feeds at high temperature (e.g., 65-95 °C), high pH values (e.g., pH > 13), and high percentage of suspended solids (6-18%), resulting in nearly complete removal of high aspect ratio solids such as fibers and other suspended solids, and producing preconditioned black liquor feeds suitable for downstream concentration using filtration systems comprising Graphene Oxide (GO) membranes.

[0016] Now referring to the drawings, FIG. 2 shows a schematic illustration of a system 1000 for removing suspended solids from a black liquor feed via a flocculation and floc removal approach, according to an embodiment. FIG. 2 shows the system 1000, which can also be referred to as the flocculation system 1000, includes a flocculation unit 110 fluidically coupled to a floc removal unit 120. The flocculation unit 110 can be configured to receive a black liquor (BL) feed 100 and conduct one or more physical and / or chemical processes to flocculate and / or agglomerate solids included in the BL feed 100, producing a flocculated BL feed 101. The flocculated BL feed 101 can flow from the flocculation unit 110 to the floc5326750747Agent’s File Ref. VSLC-014 / 01WO 331287-2099 removal unit 120 located downstream from the flocculation unit 110. The floc removal unit 120 can receive the flocculated BL feed 101, conduct one or more processing steps designed to separate flocs included in the flocculated BL feed 101, removing at least a portion of the suspended solids initially present in the BL feed 100 as flocculated solids (e.g., a floc), and producing a conditioned BL feed 102 with a reduced concentration and / or content of suspended solids. FIG. 2 shows the conditioned BL feed 102 can optionally be directed to a Graphene Oxide (GO) membrane filtration system 130 disposed downstream from the floc removal unit 120, where the black liquor can be concentrated. In some embodiments, the system 1000 can include and / or incorporate one or more optional components and / or steps (not shown in FIG. 2) for removing suspended solids which have not been removed in the floc removal unit 120. For example, in some embodiments the conditioned BL feed 102 can be directed to a filtering station disposed upstream of the GO membrane filtration system 130. The filtration station can include one or more multimedia filter(s) and / or a sand filter(s) configured to remove suspended solids which have not been removed at the floc removal unit 120. In some embodiments, the flocculated solids produced at the floc removal unit 120 can further processed. For example, in some embodiments at least a portion of the flocculated solids can be recycled to the flocculation unit 110 as shown schematically in FIG. 2, with the purpose of improving the performance (e.g., improving the yield of removed solids) of the flocculation process. In some embodiments, the flocculated solids (or at least a portion of the flocculated solids) can be pressed using a filter press or a rotary screen to remove more liquid and increase the yield of the floc removal unit 120.

[0017] The flocculation unit 110 can include any suitable vessel, container, receptacle, or the like, configured to receive and accommodate a black liquor feed and facilitate addition of one or more chemical reagent(s) used to coagulate and / or flocculate suspended solids present in the black liquor feed. The flocculation unit 110 may be sized and configured for flocculating black liquor according to a continuous process. Alternatively, in some embodiments the flocculation unit 110 may be sized and configured for flocculating black liquor according to a batch or semi-batch process. FIG. 2 shows the BL feed 100 can be received in the flocculation unit 110 to initiate coagulation and / or flocculation processes. The BL feed 100 can be a stream produced in a pulp mill which can be fed to the system 1000 for processing. In some embodiments the BL feed 100 can contain and / or include residual pulping residues, primarily lignin and hemicellulose, inorganic chemicals from the kraft or semi-chem process such as sodium hydroxide and sodium sulfate, as well as other extractives contained in the wood such6326750747Agent’s File Ref. VSLC-014 / 01WO 331287-2099 as tall oil. For example, in some embodiments the BL feed 100 can contain sodium sulfate, sodium carbonate, sodium hydrosulfide, sodium thiosulfate, and / or sodium hydroxide, residual fibers from the pulping process, as well as larger size (e.g., high molecular weight) organic species including hemicellulose, cellulose, and lignin, among others. In some embodiments, the BL feed 100 can include residual fibers produced during the pulping process. The residual fibers can be characterized by a diameter of about 1-25 pm and a length of about 100 pm to about 6 mm. In some embodiments, the BL feed 100 can include a total amount of solids (e.g., dissolved solids and suspended solids such as fibers) of at least about 6 wt.% to about 18 wt.%. In some embodiments, the BL feed 100 can be a weak black liquor (WBL) stream produced in a pulp mill and having a total amount of solids (including dissolved solids and suspended solids such as fibers) of at least about 15 wt.% to no more than about 18 wt.%. In some embodiments, the BL feed 100 can include an amount and / or load of total suspended solids (TSS, which includes suspended fibers) of at least about 15 parts per million (ppm), at least about 50 ppm, at least about 75 ppm, at least about 100 ppm, at least about 125 ppm, at least about 150 ppm, at least about 175 ppm, at least about 200 ppm, at least about 250 ppm, at least about 300 ppm, at least about 350 ppm, at least about 400 ppm, at least about 450 ppm, at least about 500 ppm, at least about 550 ppm, at least about 600 ppm, at least about 650 ppm, at least about 700 ppm, at least about 750 ppm, at least about 800 ppm, at least about 850 ppm, at least about 900 ppm, at least about 950 ppm, at least about 1000 ppm, at least about 2000 ppm, at least about 3000 ppm, at least about 4000 ppm, at least about 5000 ppm, at least about 6000 ppm, at least about 7000 ppm, at least about 8000 ppm, at least about 9000 ppm, or at least about 10,000 ppm, inclusive of all values and ranges therebetween. In some embodiments, the BL feed 100 can include an amount of total suspended solids (TSS) of no more than about 1000 ppm, no more than about 940 ppm, no more than about 880 ppm, no more than about 820 ppm, no more than about 760 ppm, no more than about 700 ppm, no more than about 640 ppm, no more than about 580 ppm, no more than about 520 ppm, no more than about 460 ppm, no more than about 400 ppm, no more than about 340 ppm, no more than about 280 ppm, no more than about 220 ppm, no more than about 160 ppm, no more than about 100 ppm, no more than about 90 ppm, no more than about 80 ppm, no more than about 70 ppm, no more than about 60 ppm, no more than about 50 ppm, no more than about 30 ppm, or no more than about 15 ppm, inclusive of all values and ranges therebetween.7326750747Agent’s File Ref. VSLC-014 / 01WO 331287-2099

[0018] Combinations of the above referenced ranges for the amount of total suspended solids (TSS) in the BL feed 100 are also possible (e.g., a TSS of at least about 50 ppm to less than about 1000 ppm, or at least about 300 ppm to less than about 600 ppm).100191 In some embodiments, the BL feed 100 can be received in the flocculation unit 110 at a temperature of at least about 50 °C, at least about 55 °C, at least about 60 °C, at least about 65 °C, at least about 70 °C, at least about 75 °C, at least about 80 °C, at least about 85 °C, at least about 90 °C, at least about 95 °C, at least about 100 °C, or at least about 105 °C, inclusive of all values and ranges therebetween. In some embodiments the BL feed 100 can be received in the flocculation unit 110 at a temperature of no more than about 105 °C, no more than about 100 °C, no more than about 90 °C, no more than about 80 °C, no more than about 70 °C, no more than about 60 °C, or no more than about 50 °C, inclusive of all values and ranges therebetween.

[0020] Combinations of the above referenced temperature of the BL feed 100 are also possible (e.g., at BL feed temperature of at least about 50 °C to less than about 95 °C, or at least about 80 °C to less than about 99 °C).

[0021] In some embodiments, the BL feed 100 can be received at the flocculation unit 110 at a pH of at least about 10, at least about 10.5, at least about 11, at least about 11.5, at least about 12, at least about 12.5, at least about 13, at least about 13.5, or at least 14, inclusive of all values and ranges therebetween. In some embodiments, the BL feed 100 can be received in the flocculation unit 110 at a pH of no more than about 14, no more than about 13.5, no more than about 12.9, no more than about 12.3, no more than about 11.7, no more than about 11.1, no more than about 10.6, or no more than about 10, inclusive of all values and ranges therebetween.

[0022] Combinations of the above referenced pH of the BL feed 100 are also possible (e.g., a BL feed having a pH of at least about 10.5 to less than about 13, or at least about 11 to less than about 14).

[0023] As described above, in some embodiments the flocculation unit 110 can be configured to initiate a coagulation process and / or reaction with the BL feed 100 at the temperature and / or pH at which the BL feed 100 is received in the flocculation unit 110. Alternatively, in some embodiments, the BL feed 100 can be received at a heat exchanger 112 included in the flocculation unit 110. The heat exchanger can cool the BL feed 100 to a preferred and / or predetermined temperature, as further described herein with reference to FIG.8326750747Agent’s File Ref. VSLC-014 / 01WO 331287-20994. In such embodiments, the flocculation unit 110 can be configured to initiate a coagulation process and / or reaction with the BL feed 100 at the preferred and / or predetermined temperature. One or more coagulant reagent(s) can be added and / or mixed to the BL feed 100 in the flocculation unit 110. The one or more coagulant reagent(s) can be selected to neutralize negative charges present in the particles forming the suspended solids and facilitate the formation of micro flocs. In some embodiments, the one or more coagulant reagent(s) can include species such as, aluminum chlorohydrate (ACH), aluminum sulfate (Alum), ferric chloride, ferric sulfate, polydiallyldimethylammonium chloride (PolyDADMAC), polyaluminum chloride (PAC), epichlorohydrindimethylamine (EPI-DMA) or combinations thereof. For example, in some embodiments the BL feed 100 can be received in the flocculation unit 110 at a temperature of at least about 90 °C and a pH of no more than 12, and then be mixed with one or more coagulant reagent(s) including ACH, Alum, ferric chloride, ferric sulfate, PolyDADMAC, or PAC. In some embodiments, the BL feed 100 can be received in the flocculation unit 110 at a temperature of at least about 90 °C and a pH of at least about 12, and then be mixed with an EPI-DMA coagulant reagent.

[0024] The one or more coagulant reagent(s) can be added according to predetermined amounts and / or dosages. In some embodiments, the dosage of coagulant reagent(s) added and / or mixed with the BL feed 100 can be at least about 0.5 parts per million (ppm), at least about 1 ppm, at least about 1.5 ppm, at least about 2 ppm, at least about 5 ppm, at least about 10 ppm, at least about 20 ppm, at least about 30 ppm, at least about 40 ppm, at least about 50 ppm, at least about 60 ppm, at least about 70 ppm, at least about 80 ppm, at least about 90 ppm, or at least about 100 ppm, inclusive of all values and ranges therebetween. In some embodiments, the dosage of coagulant reagent(s) added and / or mixed with the BL feed 100 can be no more than about 100 ppm, no more than about 95 ppm, no more than about 85 ppm, no more than about 75 ppm, no more than about 65 ppm, no more than about 55 ppm, no more than about 45 ppm, no more than about 35 ppm, no more than about 25 ppm, no more than about 15 ppm, no more than about 5 ppm, no more than about 1 ppm, or no more than about 0.5 ppm, inclusive of all values and ranges therebetween.

[0025] Combinations of the above referenced dosages of coagulant reagent(s) added and / or mixed with the BL feed 100 are also possible (e.g., a dosage of coagulant reagent(s) of at least about 0.5 ppm to less than about 100 ppm, or at least about 10 ppm to less than about 80 ppm).

[0026] As described above, the flocculation unit 110 can also be configured to initiate a flocculation process with the BL feed 100 at the temperature and / or pH at which the BL feed9326750747Agent’s File Ref. VSLC-014 / 01WO 331287-2099100 is received in the flocculation unit 110. In some implementations, the flocculation unit 110 can be configured to initiate a flocculation process after completing a coagulation process and / or reaction (e.g., conducting a coagulation step followed by a flocculation step). For example, in some embodiments the BL feed 100 can be received in the flocculation unit 110 and then be subjected to a coagulation process and / or reaction by adding and / or mixing coagulant reagent(s) to neutralize the negative charges of the suspended solid particles in the BL feed 100 and form micro flocs. A flocculant (or a mixture of flocculants) can then be added to the BL feed 100 to initiate a flocculation process. During the flocculation process, the flocculant can be dispersed within the BL feed 100 to facilitate the agglomeration of the micro flocs produced in the coagulation process and / or reaction, forming large size flocs that can then be separated and / or removed in a downstream process. In some embodiments, the flocculation unit 110 can be configured to initiate a flocculation process without conducting a coagulation process and / or reaction. That is to say, in some embodiments the BL feed 100 can be received in the flocculation unit 110 and be directly exposed to a flocculant (or a mixture of flocculants) without coagulating the BL feed 100 (e.g., without introducing coagulation reagent(s)). In such embodiments, the flocculation unit 110 can initiate the flocculation process at a pH and a temperature at which the BL feed 100 is received (or at a preferred and / or predetermined temperature when the flocculation unit 110 includes a heat exchanger, as further disclosed with reference to FIG. 4).

[0027] In some embodiments, the flocculant can include a polymer with a molecular weight (MW) between 100 and 20,000 kDa. In some embodiments, the flocculant can be a homopolymer with a 100% cationic charge (e.g., a cationic homopolymer). In some embodiments, the flocculant can be a copolymer including at least a first and a second comonomer. In such embodiment, the first comonomer can be a cationic comonomer, while the second comonomer can be a neutral comonomer. The first comonomer may contain a quaternary amine or a primary, secondary or tertiary amine which is partially or completely positively charged due to the pH of the BL feed 100. In some implementations, the first comonomer can account for about 0.5%, about 1%, about 5%, about 10%, about 15%, about 20%, about 25%, about 30%, about 35%, about 40%, about 45%, about 50%, about 55%, about 60%, about 65%, about 70%, about 75%, about 80%, about 85%, about 90%, or about 95% of the copolymer. The neutral comonomer can account for balance and / or remainer percentage of the copolymer. For example, in some embodiments the flocculant can include a copolymer having a cationic comonomer and a neutral comonomer with a distribution of cationic10326750747Agent’s File Ref. VSLC-014 / 01WO 331287-2099 comonomer to neutral comonomer of 95-0.5%. In some embodiments, the flocculant can include copolymers of polyacrylamide and other polymeric amines. For example, in some embodiments, the flocculant can include poly(acrylamide-co-[3-(acryloylamino)propyl]trimethylammonium X), poly(acrylamide-co-[3-(acryloylamino)ethyl]trimethylammonium X), poly(acrylamide-co-[2-(acryloyloxy)ethyl]trimethylammonium X), and / or a product of polymerization of trimethylamine with epichlorohydrin, with the main repeating unit of 2-hydroxypropyl-N,N- dimethylammonium X, where X represents any suitable anion such as chlorine, bromine, and the like. For example, in some embodiments, the flocculant can include the copolymers described above or a commercially available composition thereof, such as for example, DREWFLOC™ 411, DREWFLOC™ 410, DREWFLOC™ 433, ZALTA™ MF5710,ZALTA™ MF8615, SUPERFLOC® 4512, SUPERFLOC® C-1592 RSP, SUPERFLOC®SD-2081, SUPERFLOC® C-1555L, or the like. FIGS. 3A-3E show the chemical structures of example coagulants and flocculants, according to different embodiment on the present disclosure. FIGS. 3A shows the chemical structure of an example homopolymer flocculants with a 100% cationic charge. FIGS. 3C-3E shows the chemical structures of example copolymer flocculants with a partial cationic charge. R represents O or N; x=0-l; z=l-5; and n, q, j+k represent repeat units required to reach a MW of 100-20,000 kDa, and maintain a ratio of 0.1-20% cationic charge, and w = 50-5000. FIG 3B shows the chemical structure of a polydiallyldimethylammonium chloride (PolyDADMAC) coagulant.

[0028] In some embodiments, the flocculant (or a mixture of flocculants) can be added to the BL feed 100 in the flocculation unit 110 according to predetermined quantities and / or dosages. The selection of the specific flocculant and its respective dosage can be determined based on the characteristics of BL feed 100, such as for example, pH, TSS, lignin concentration, soap concentration, conductivity, average particle size of the suspended solids, suspended solids composition (e.g., percent cellulose, ash content, fiber count, etc.), salinity and temperature. In some embodiments, the dosage of flocculant (or mixture of flocculants) added and / or mixed with the BL feed 100 can be at least about 50 ppb, at least about 100 ppb, at least about 150 ppb, at least about 200 ppb, at least about 300 ppb, at least about 400 ppb, at least about 500 ppb, at least about 600 ppb, at least about 700 ppb, at least about 800 ppb, at least about 900 ppb, at least about 1 ppm, at least about 5 ppm, at least about 10 ppm, at least about 15 ppm, at least about 20 ppm, at least about 25 ppm, at least about 30 ppm, at least about 35 ppm, at least about 40 ppm, or at least about 50 ppm, inclusive of all values and ranges11326750747Agent’s File Ref. VSLC-014 / 01WO 331287-2099 therebetween. In some embodiments, the dosage of flocculant (or mixture of flocculants) added and / or mixed with the BL feed 100 can be no more than about 50 ppm, no more than about 40 ppm, no more than about 30 ppm, no more than about 20 ppm, no more than about 10 ppm, no more than about 5 ppm, no more than about 1 ppm, no more than about 950 ppb, no more than about 850 ppb, no more than about 750 ppm, no more than about 650 ppm, no more than about 150 ppm, or no more than about 50 ppm, inclusive of all values and ranges therebetween.

[0029] Combinations of the above referenced dosages of flocculant (or mixture of flocculants) added and / or mixed with the BL feed 100 in the flocculant unit 110 are also possible (e.g., a dosage of flocculant (or mixture of coagulants) of between about 1 ppb to less than about 25 ppb, or between at least about 11 to less than about 14)

[0030] In some embodiments, the flocculant (or mixture of flocculants) can be added to the BL feed 100 in the flocculant unit 110 under rapid mixing conditions. For example, in some embodiments the flocculant (or mixture of flocculants) can be added the BL feed 100 by providing agitation with a suitable agitation equipment disposed in the flocculation unit 110 (e.g., a mechanical agitator, propeller, turbine agitator, impeller, or the like) operating at a predetermined and / or preferred rotational speed. In some embodiments the predetermined and / or preferred rotational speed of the agitator can be at least about 50 revolutions per minute (rpm), at least about 60 rpm, at least about 80 rpm, at least about 100 rpm, at least about 120 rpm, at least about 140 rpm, at least about 160 rpm, at least about 180 rpm, at least about 200 rpm, at least about 220 rpm, at least about 240 rpm, at least about 280 rpm, at least about 300 rpm, at least about 350 rpm, at least about 400 rpm, or at least about 500 rpm, inclusive of all values and ranges therebetween. In some embodiments, predetermined and / or preferred rotational speed of the agitator can be no more than about 500 rpm, no more than about 440 rpm, no more than about 380 rpm, no more than about 320 rpm, no more than about 260 rpm, no more than about 200 rpm, no more than about 140 rpm, no more than about 80 rpm, or no more than about 50 rpm, inclusive of all values and ranges therebetween. In some embodiments, the flocculants (or mixture of flocculants) can be added the BL feed 100 in the flocculation unit 110 while providing different levels of agitation for suitable periods of time. For example, in some embodiments the flocculant (or mixture of flocculants) can be added the BL feed 100 in the flocculation unit 110 at a first rotational speed for a first period of time. The flocculant can then be allowed to continue mixing with the BL feed 100 at a second rotational speed, different from the first rotational speed, for a second period of time. In some12326750747Agent’s File Ref. VSLC-014 / 01WO 331287-2099 embodiments, the first rotational speed can be higher than the second rotational speed. For example, in some embodiments the BL feed 100 is first mixed with the flocculant in the flocculation unit 110 at a first rotational speed of about 300 rpm for a first period of time, and then allowed to continue mixing with flocculant at a second rotational speed of about 50 rpm for a second period of time (e.g., rapid initial mixing followed by slower mixing). In some embodiments, the first period of time can be about 0.5 min, about 1 min, about 1.5 min, about 2 min, about 2.5 min, about 3 min, about 4 min, about 5 min, about 6 min, or about 7.5 min, inclusive of all values and ranges therebetween. In some embodiments, the second period of time can be about 2 min, about 2.5 min, about 3 min, about 3.5 min, about 4 min, about 4.5 min, about 5 min, about 6 min, about 8 min, about 10 min, about 12 min, about 14 min, about 16 min, about 18 min, about 20 min, about 22 min, about 24 min, about 26 min, about 28 min, or about 30 min, inclusive of all values and ranges therebetween.

[0031] The coagulant reagent(s) and / or flocculants can be added to the BL feed 100 in the flocculation unit 110 according to the procedures and / or conditions described above, to produce a flocculated BL feed 101 and a floc which can remain stable for a period of time in excess of 1 hour. As shown in FIG. 2, the flocculated BL feed 101 and the floc produced in the flocculation unit 110 can be directed and / or flown from the flocculation unit 110 to the floc removal unit 120. The floc can be composed of water and suspended solids initially present in the BL feed 100 including fibers. For example, in some embodiments the floc can be characterized by a content of solids of at least about 8 wt.% to about 65 wt.%. These solids present in the floc can constitute a percentage and / or fraction of the amount of total suspended solids (TSS) that were initially present in the BL feed 100. For example, in some embodiments the floc can contain and / or include at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 99%, or at least 99.99% of the total suspended solids (TSS) that were initially present in the BL feed 100. In some embodiments, the floc can contain at least about50% of the fiber, at least about 55% of the fiber, at least about 60% of the fiber, at least about65% of the fiber, at least about 70% of the fiber, at least about 75% of the fiber, at least about80% of the fiber, at least about 85% of the fiber, at least about 90% of the fiber, at least about95% of the fiber, or at least 99% of the fiber initially included in the BL feed 100.

[0032] The successful removal of suspended solid present in the BL feed 100, and particularly high aspect ratio materials such as cellulose fibers stemming from the kraft and / or semi-chem pulp process requires providing an accurate dosage and / or amount of coagulant13326750747Agent’s File Ref. VSLC-014 / 01WO 331287-2099 reagent(s) and / or flocculants in order to ensure adequate charge neutralization, leading to formation of a floc with high content of solids removed from the BL feed 100. Failure to formulate an accurate dosage of the coagulant reagent(s) and / or flocculants may result in fouling of a filtration system disposed downstream of the floc removal unit 120. Suitable dosages of coagulant reagent(s) and / or flocculants can be determined by taking measurements of the composition of the BL feed 100 flowing to the flocculation unit 110 as a function of time (e.g., in-line measurement of BL feed 100 composition). For example, in some embodiments, the flocculation unit 110 can be equipped with a fiber measurement device designed to measure the content of fiber in the BL feed 100 prior to initiating the coagulation and / or flocculation processes (e.g., upstream fiber measurement). The measurements obtained with the fiber measurement device can then be used to control and / or monitor the dosage of coagulant reagent(s) and flocculants via a feed forward control loop. In some embodiments, the flocculation unit 110 can be equipped with a fiber measurement device designed to measure the content of fiber in the BL feed 100 after the coagulation and / or flocculation processes have been conducted in the flocculation unit 110. Said in other words, in some embodiments the flocculation unit 110 can be equipped with a fiber measurement device designed to measure the content of fiber in the flocculated BL feed 101. The measurements obtained with the fiber measurement device from the flocculated BL feed 101 can be used to evaluate the performance of the flocculation unit 110 and adjust the dosage of coagulant reagent(s) and flocculants, as well as other parameters of the flocculation unit 110 such as operating temperature, pH, and agitation conditions (e.g., rotational speed, and / or duration) via a feedback back control. In some embodiments, the fiber measurement device can include an in-line screen or filter (e.g., a screen disposed on the path of the BL feed 100) sized and shaped to allow passage of suspended solids included in the BL feed 100 having a small particle size, while retaining suspended solids or fibers having a large particle size. In some embodiments, the screen or filter can have a nominal opening of about 1-100 microns. In some embodiments, the screen or filter can be and / or have a shape selected to provide predictable flow coefficient change at a constant fiber concentration to allow correlation to actual fiber concentration. In some embodiments, the fiber measurement device can include multiple screens and / or filters (e.g., duplex screens). In some embodiments, the fiber measurement device can have one or more mechanisms to remove material (e.g., suspended solids including fibers) retained by the screen(s) or filter(s). For example, in some embodiments, the fiber measurement device can include backwashing capabilities, allow regular changeouts, self-cleaning, or include clean-in place systems to ensure the continuous operation of the flocculation unit 110. In some14326750747Agent’s File Ref. VSLC-014 / 01WO 331287-2099 embodiments, the clean-in place systems included in the fiber measurement device can be mechanical, thermal, or chemical in nature. The clean-in place systems can be designed to target the removal or degradation of suspended solids or fibers collected in the fiber measurement device.

[0033] In some embodiments, the flocculation unit 110 can be designed to adjust the temperature of the BL feed 100 prior to initiating the coagulation and / or flocculation processes. In such embodiments, the operating temperature for the BL feed 100 during the coagulation and / or flocculation process may be lower than the “as-received” BL feed 100 (e.g., the BL feed 100 initially received in the flocculation unit 110). Said in other words, the BL feed can be pre-cooled prior to initiating the coagulation and / or flocculation processes. The flocculation unit 110 can include a heat exchanger configured to exchange heat between the BL feed 100 and the flocculated BL feed 101. Alternatively, in some embodiments, the heat exchanger can be configured to exchange heat with a suitable process stream such as a permeate or a concentrate produced in the optional GO membrane filtration system 130.

[0034] FIG. 4 shows an example embodiment in which a flocculation unit 110 includes a heat exchanger 112 and a flocculation device 114. The flocculation device 114, which can also be referred as the “flocculation reactor 114” herein, can be a vessel, container, receptacle, or the like, defining an interior volume in which the BL feed 100 can be received and mixed with coagulant reagent(s) and flocculants. The flocculation device 114 can include an agitation equipment (e.g., a mechanical agitator, propeller, turbine agitator, impeller, or the like, not show in FIG. 4) disposed within the interior volume of the flocculation device 114. The agitation equipment can be used to facilitate mixing the coagulant reagent(s) and flocculants as described above. In some embodiments the flocculation device 114 can also include a cooling system. For example, in some embodiments the flocculation device 114 can include a passive cooling system (not shown in FIG. 4). The passive cooling system may include uninsulated piping, a portion of the vessel comprising thermally conductive material such as aluminum, aluminum nitride ceramics, copper, iron, nickel, or the like. In some embodiments, the passive cooling system may include suitable heatsinks configured to conduct heat away from one or more subcomponent of the flocculation device 114 such as one or more lateral wall defining the interior volume of the flocculation device 114, a screen and / or a filter included and / or coupled to the flocculation device 114, an impeller, a baffle, etc. The heatsinks may be formed from any suitable metal (e.g., copper, aluminum, steel, and the like) coated with a corrosion resistant thin coating. In some implementations, the heatsinks may include fins15326750747Agent’s File Ref. VSLC-014 / 01WO 331287-2099 configured to dissipate heat into surrounding ambient air. Additionally, or alternatively, in some embodiments the flocculation device 114 can include an active cooling system. The active cooling system may include fans for improving heat dissipation from the fins of one or more heat sinks. In some embodiments, the active cooling system can also include a water sprayer for spraying water over parts and / or subcomponents of the flocculation device 114.

[0035] FIG. 4 shows the heat exchanger 112 is in fluid communication with the flocculation device 114 and disposed upstream of the flocculation device 114, such that a BL feed 100 (shown in FIG. 4 as a BL feed 100 (hot)) enters the heat exchanger 112 to be cooled prior to entering the flocculation device 114. The heat exchanger 112 may be any suitable heat exchanger configured to cool the BL feed 100 (hot), producing a BL feed 100 (cold). Herein, the terms “hot” and “cold” indicate the relative temperature of the BL feed 100. Said in other words, the BL feed 100 (hot) entering the heat exchanger 112 has a temperature that is higher than the temperature of the BL feed 100 (cold) leaving the heat exchange. The BL feed 100 (cold) can then be directed and / or flown from the heat exchanger 112 to the flocculation device 114 where the agglomeration and / or flocculation processes can take place, as described above. In some embodiments, the active and / or passive cooling systems of the flocculation device 114 can be used to dissipate heat from the BL feed 100 (cold) while the agglomeration and / or flocculation processes take place in the flocculation device 114. As a result, the flocculation device 114 can dissipate heat and produce a flocculated BL feed 101 (cold).

[0036] In the example embodiment shown in FIG. 4, the flocculated BL feed 101 (cold) produced at the flocculation device 114 is directed and / or flows to the heat exchanger 112 where it is heated while the BL feed 100 (hot) is cooled by dissipating heat towards the flocculated BL feed 101 (cold). In an example implementation, the heat exchanger 112 is a convection / conduction heat exchanger (e.g., the heat exchanger 112 utilizes the transmission of thermal energy from a surface by way of the motion of the flocculated BL feed 101 (cold) relative to the surface of an enclosure containing a BL feed 100 (hot). During the heat exchange, the flocculated BL feed 101 may be heated by about a few tens of degrees. Said in other words, the difference in temperature between the flocculated BL feed 101 (cold) entering the heat exchanger and the temperature of the flocculated BL feed 101 (hot) leaving the heat exchanger can increase at least about 5 °C and by no more than about 40 °C. Further, the BL feed 100 may be cooled by about a few degrees to a few tens of degrees. For example, the BL feed 100 (hot) entering the heat exchanger 112 may be cooled by at least about 5 °C and by no more than about 40 °C with respect to the BL feed (cold) leaving the heat exchanger 112.16326750747Agent’s File Ref. VSLC-014 / 01WO 331287-2099

[0037] In some implementations, in addition to using the flocculated BL feed 101 (cold), or alternatively to using a flocculated BL feed 101 (cold) to cool the BL feed 100 (hot), a different liquid may be utilized. For example, a chilled fluid (e.g., chilled water or antifreeze) may be utilized additionally (or alternatively) to cool the BL feed 100 (hot). In some cases, a first piping system of the heat exchanger 112 may be used to cool the BL feed 100 (hot) using the flocculated BL feed 101 (cold), and a second piping system of the heat exchanger 112 may be used to cool the BL feed 100 (hot) using a chilled fluid. Additionally, besides using the flocculated BL feed 101 (cold) or the chilled fluid as cooling agents, the heat exchanger 112 may also use other approaches for cooling the BL feed 100 (hot) (e.g., thermoelectric cooling, refrigeration system, or the like).

[0038] In some implementations, the heat exchanger 112 may include passive cooling elements in addition to active cooling elements that utilize Flocculated BL feed 101 (cold) (or other streams produced in the GO membrane system 130) and chilled fluids. For example, the heat exchanger 112 may include suitable heatsinks, and the like. In some implementations, the heat exchanger 112 includes heat pipes, fans, or any other devices for promoting the removal of heat from the feed. In various implementations, the heat exchanger 112 may be exposed to an ambient environment (e.g., to outside air) and operate at about atmospheric pressure. Further details of the integration of a heat exchanger with a flocculation and / or a GO membrane filtration system are disclosed in U.S. Patent No. 11,913,692, titled “Heat Exchanger Integration with Membrane System for Evaporator Pre-Concentration,” issued February 27, 2024 (the ’692 patent), the disclosure of which is incorporated herein by reference in its entirety.

[0039] In some embodiments, the heat exchanger 112 can be a single heat exchanger. In some embodiments, the heat exchanger can be multiple heat exchangers or a single heat exchanger utilizing multiple shells. The heat exchanger 112 can be used to regulate the temperature at which the flocculation takes place by adjusting the temperature of the BL feed 100 as described above. That is to say, the heat exchanger 112 can be used to adjust the BL feed 100 temperature in the flocculation device 114 such that the coagulation and / or flocculation processes take place at that adjusted BL feed 100 temperature. For example, in some embodiments, the heat exchanger 112 can be used to adjust the BL feed 100 temperature to at least about 90 °C, such that the agglomeration and / or flocculation processes take place in the flocculation device 114 at a temperature of at least about 90 °C. In some embodiments, the heat exchanger 112 can be used to adjust the BL feed 100 temperature to no higher than about17326750747Agent’s File Ref. VSLC-014 / 01WO 331287-209990 °C, such that the agglomeration and / or flocculation processes take place in the flocculation device 114 at a temperature no higher than 90 °C. Operation of the flocculation unit 110 at lower temperature can increase the yield of the agglomeration and / or flocculation processes (e.g., increase the amount and / or fraction of suspended solids removed from the BL feed 100 in the flocculation unit 110).

[0040] In some embodiments, the heat exchanger 112 can be used to regulate the temperature of the downstream processes taking place after the coagulation and / or flocculation. Said in other words, in some embodiments the heat exchanger 112 can be used to regulate and / or adjust the temperature of flocculated BL feed 101 and / or the conditioned BL feed 102. In some embodiments, the heat exchanger 112 can be used to adjust both: the temperature at which the flocculation takes place in the flocculation unit 110, and the temperature of the flocculated BL feed 101 and / or the conditioned BL feed 102. For example, in some embodiments, particularly when a filtration system disposed downstream to the floc removal unit 120 includes a graphene oxide (GO) membrane, the heat exchanger 112 can be used to adjust the temperature of the conditioned BL feed 102 to at least about 60 °C and no more than about 80 °C. In some embodiments, particularly when a filtration system disposed downstream to the floc removal unit 120 does not includes a graphene oxide (GO) membrane, the heat exchanger 112 can be used to adjust the temperature of the conditioned BL feed 102 to at least about 25 °C to no more than about 40 °C.10041] Referring back to FIG. 2, the flocculated BL feed 101 can flow from the flocculation unit 110 to the floc removal unit 120. The floc removal unit 120 can be configured to receive the flocculated BL feed 101 and conduct one or more processes to remove a floc containing at least a portion the suspended solids, including fibers and other high aspect ratio species included in the BL feed 100. In some embodiments, the floc removal unit 120 can also be configured to remove residual suspended solids that have not been incorporated into a floc. The floc removal unit 120 can be configured to remove suspended solids and produce a conditioned BL feed 102. In some embodiments, the floc removal unit 120 can be integrated with the flocculation unit 110. For example, in some embodiments the process 1000 can include a single device comprising a flocculation unit 110 and a floc removal unit 120. The flocculation unit 110 can define a first vessel, container, receptacle, or the like, configured to receive and accommodate the BL feed 100 and facilitate addition of one or more chemical reagent(s) used to coagulate and / or flocculate suspended solids present in the BL feed 100 and produce the flocculated BL feed 101. The floc removal unit 120 can define a separate second18326750747Agent’s File Ref. VSLC-014 / 01WO 331287-2099 vessel, container, receptacle, or the like within he device, configured to receive the flocculated BL feed 101 and conduct one or more processes to remove a floc containing at least a portion the suspended solids, including fibers and other high aspect ratio species included in the BL feed 100. In some embodiments the floc can be removed by sedimentation. In some embodiments the floc can be removed by clarification. For example, in some embodiments the floc removal unit 120 can include a lamellar plate clarifier (or any other suitable clarifier) with a sludge bed (e.g., a volume disposed within the clarifier) sized and configured to accommodate floc and / or debris removed from the flocculated BL feed 101 at the bottom of the clarifier. In use, the clarifier can include one or more inlet ports configured to receive the flocculated BL feed 101. The clarifier can be used to remove the suspended solids, depositing them as a floc and / or sludge in the sludge bed, and producing a clarified stream (e.g., the conditioned BL feed 102). The clarifier can also include one or more outlet ports that can be used to direct the conditioned BL feed 102 to the optional GO membrane filtration system 130 or other downstream processing unit. In some embodiments, the clarifier can be configured to (1) receive, via the inlet port(s), the flocculated BL feed 101 at a first temperature, (2) separate the flocs and / or sludge from the flocculated BL feed 101, (3) accumulate the flocs and / or sludge in the sludge bed, and (4) direct the resulting conditioned BL feed 102 via the outlet port(s) at a second temperature to the optional GO membrane filtration system 130 or other downstream processing unit. In some embodiments, a difference between the first and the second temperature in the clarifier is no more than 20 °C, no more than 10 °C, no more than 5° C, or no more than 2 °C, inclusive of all values and ranges therebetween. Furthermore, in some embodiments, a temperature difference across the sludge bed (e.g., horizontally across the clarifier from a first end of the clarifier to a second end of the clarifier, the second end opposite to the first end), is less than about 5° C, less than about 4° C, less than about 3° C, less than about 1° C , or less than about 1 °C, inclusive of all values and ranges therebetween. In some embodiments, the floc can be removed by centrifugation. In some embodiments, the floc can be removed by filtration (e.g., sand filters, multi-media filtration (MMF), drum filtration). In some embodiments the floc can be removed by air injection flotation methods (e.g., Suspended Air Flotation (SAF), Dissolved Air Flotation (DAF), or Induced Gas Flotation (IGF)). In particular, when DAF methods are used to remove the floc and produce the conditioned BL feed 102, the gas of choice can include carbon dioxide (CO2). The use of CO2 can facilitate removing the floc and simultaneously adjusting the pH of the conditioned BL feed 102, owing to the acidic character of gaseous CO2. Said in other words, in some embodiments the floc19326750747Agent’s File Ref. VSLC-014 / 01WO 331287-2099 removal unit 120 can include a DAF device designed to separate a floc containing at least a portion of the suspended solids in the BL feed 100 and produce a conditioned BL feed 102. In such embodiments, the DAF device can operate using a CO2 gas, or a gas mixture including CO2, to facilitate the removal of the floc and simultaneously adjusting (e.g., reducing) the pH of the conditioned BL feed 102 to a suitable pH that can be used to concentrate the black liquor in a filtration system such as the optional graphene oxide (GO) membrane filtration system 130 shown in FIG. 2. Further details on the GO membrane filtration system 130 are disclosed in International Patent Publication No. WO 2024 / 151542, titled “Systems and Methods for Processing Black Liquor Solutions,” filed January 8, 2024 (the ’542 publication), the disclosure of which is herein incorporated by reference in its entirety.

[0042] As described above, the floc removal unit 120 can be configured to receive the flocculated BL feed 101, separate flocculated solids which are removed in the floc, and produce a conditioned BL feed 102. In some embodiments, the amount of total suspended solids (TSS) removed by the system 1000 from the BL feed 100 can be at least about 50%, at least about 55%, at least about 60%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, or at least about 90%, or up to 100%, inclusive of all values and ranges therebetween. In some embodiments, the system 1000 can be configured to remove 100% of the TSS initially present in the BL feed 100. In some embodiments, the amount of total suspended solids (TSS) present in the BL conditioned feed 102 can be no greater than about 5 ppm. In some embodiments, the difference and / or change in the amount total suspended solids (ATSS) between the BL feed 100 received at the flocculation unit 110 and the conditioned BL feed 102 produced at the floc removal unit 120 can be at least about 45 ppm, at least about 50 ppm, at least about 60 ppm, at least about 80 ppm, at least about 100 ppm, at least about 150 ppm, at least about 200 ppm, at least about 300 ppm, at least about 400 ppm, at least about 500 ppm, at least about 600 ppm, at least about 700 ppm, at least about 800 ppm, at least about 900 ppm, or at least about 1000 ppm, inclusive of all values and ranges therebetween.100431 In some embodiments, the conditioned BL feed 102 can be produced in the floc removal unit 120 without reducing the temperature and / or pH with respect to the BL feed 100 received in the flocculation unit 110. Said in other words, in some embodiments the system 1000 can be configured to produce a conditioned BL feed 102 at a temperature and pH substantially similar and / or the same as the temperature and pH of the BL feed 100 received in the flocculation unit 110. Alternatively, in some implementations the conditioned BL feed 10220326750747Agent’s File Ref. VSLC-014 / 01WO 331287-2099 can be further processed prior to being directed to the GO membrane filtration system 130. For example, in some implementations the floc removal unit 120 can be integrated with a heat exchanger to adjust the temperature of the conditioned BL feed 102. In some embodiments, the floc removal unit 120 can include a Dissolved Air Flotation (DAF) system configured to separate the floc from the flocculated BL feed 102. In some implementations, the DAF system can use CO2, or a gas mixture containing CO2 to separate the floc and simultaneously reducing the pH of the conditioned BL feed 102, as described above.

[0044] In some embodiments, the floc produced in the floc removal unit 120 can be disposed of by either (1) recirculating the solids included in the floc back to the mill, (2) combusting the floc to generate heat, (3) producing a waste stream, or (4) producing a higher value product

[0045] In some embodiments, recirculating the solids included in the floc can be done by mixing the floc with a brown stock processing stream with the purpose of recovering the separated fibers in pulp washing. In some implementations, the floc can be integrated with the brown stock processing stream along one or more primary locations and / or integration points in the mill. For example, the floc can be directed to a blow tank, a fiber screening, or an upstream point of the refiners. In some implementations, the floc can be integrated with the brown stock processing stream along one or more secondary locations and / or integration points in the mill. For example, the floc can be directed to an inlet of a washer. In some embodiments, combusting the floc can be done by breaking apart the floc (e.g., thermally and / or mechanically degrading the flocculants used in the system 1000 to produce the floc) and then then mixing the separated solids included in the floc (e.g., the broken-up floc) with a concentrated black liquor produced in the GO membrane filtration system 130. In some embodiments, the flocculants can be mechanically degraded by mixing the floc with a black liquor stream (e.g., a WBL stream, including for example, a portion of the BL feed 100) with the aid of a high shear mixer. The high shear mixer can provide the mechanical energy to break apart the flocculants and cause a disintegration of the floc. In some embodiments, the flocculants can be chemically degraded by exposing the floc to specific conditions and / or reagents. Chemical degradation of the flocculants (e.g., deflocculation) can occur when chemical bonds in the flocculant are broken due to exposure of the flocculant to specific conditions and / or chemical species. This may result in a loss of electrostatic attraction between the flocculant and the suspended solids, and development of electrostatic repulsion between the flocculant and suspended solids. In some embodiments, the flocculants can have a chemical structure that21326750747Agent’s File Ref. VSLC-014 / 01WO 331287-2099 includes specific chemical bonds that can trigger chemical degradation of the flocculent when exposed to specific conditions such as temperature, pressure, or pH, and / when placed in contact with specific chemical reagents such as a strong base, a strong acid, or a catalytic material (e.g., a catalyst). In some embodiments the flocculants can include ester bonds which can be degraded when the floc is exposed to specific temperatures and / or heat for an extended period of time. For example, in some embodiments, the flocculants can include methacrylates, acrylates, and or similar chemical species containing ester bonds that can be degraded when the flocculant is exposed to a pH of at least about 12 to about 13 and / or a temperature of at least about 50 °C to about 90 °C for at least 6 to 24 hours. In some embodiments, the flocculants can include amide bonds which can be degraded at specific temperatures and / or heat for extended period of time that are higher and / or more extreme than those required for degrading flocculants including ester bonds. For example, in some embodiments the flocculants can include methacrylamides, acrylamides, or similar chemical species containing amide chemical bonds, which can be degraded at a pH of at least about 13 to about 14, and / or a temperature of at least about 95 °C to about 100 °C, for a period of time of about 1 hour. In some embodiments, the flocculant can be selected to include a combination of amides, amines, and / or other suitable chemical bonds which are likely to degrade under exposure to specific chemical reagents, temperature, pressure, and / or heat for a period of time. The deflocculated material (e.g., the broken-up floc), which includes the degraded flocculants, the coagulants, and the suspended solids can then be sent to a train of evaporators where the broken-up floc is eventually combusted with other organic matter. In some implementations, the broken-up floc can also be mixed with strong black liquor after a train of evaporators (~50 wt.% total amount of solids) or before feeding a recovery boiler (60 to 80 wt.% total amount of solids) so that the fibers and / or separated solids cannot cause any evaporator fouling.

[0046] FIG 5 shows a method 10 for processing a black liquor (BL) feed for removing at least a portion of suspended solids present in the BL feed and producing a conditioned BL feed that can be concentrated in a downstream graphene oxide membrane filtration system. At 11, the method 10 includes receiving, at a flocculation unit, a BL feed characterized by a first total amount of suspended solids (TSS), a first temperature, and pH. In some embodiments, the flocculation unit can be similar to and / or the same as the flocculation unit 110 and the BL feed can be similar to and / or the same as BL feed 100 described above with reference to FIG. 2. In some embodiments, the flocculation unit can be configured to receive the BL feed operating according to a continuous manner and / or mode. In some embodiments, the flocculation unit22326750747Agent’s File Ref. VSLC-014 / 01WO 331287-2099 can be configured to receive the BL feed and operate according to a semi continuous manner and / or mode. In some embodiments, the flocculation unit can be configured to receive the BL feed operating according to a batch manner and / or mode. The BL feed can include sodium sulfate, sodium carbonate, sodium hydrosulfide, sodium thiosulfate, and / or sodium hydroxide, residual fibers from the pulping process, as well as larger size (e.g., high molecular weight) organic species including hemicellulose, cellulose, and lignin, among others. In some embodiments, the BL feed can be characterized by TSS of at least about 15 ppm to no more than about 1000 ppm, inclusive of all values and ranges therein. In some embodiments, the BL feed can be characterized by a first temperature, with the first temperature being at least about 50 °C to no more than about 10 °C, inclusive of all values and ranges therebetween. In some embodiments, the BL feed can be characterized by a pH, with the pH being at least about 10 to no more than about 14, inclusive of all values and ranges therebetween. The ranges for the TSS, the first temperature, and the pH of the BL feed have been disclosed above in greater detail with reference to the system 1000 shown in FIG. 2.

[0047] At 12, the method 10 can optionally include pre-cooling the BL feed from an initial temperature to the first temperature. In some embodiments, the flocculation unit can include a heat exchanger and a flocculation device. In some embodiments, the heat exchanger and the flocculation device can be similar to and / or the same as the heat exchanger 112 and the flocculation device 114 described above with reference to FIG. 4. The BL feed can be received at the heat exchanger at the initial temperature. In some embodiments the heat exchanger can be fluidically coupled to the flocculation device and disposed upstream to the flocculation device. The heat exchanger can be configured to pre-cool the BL feed from the initial temperature to the first temperature (e.g., decrease and / or reduce the first temperature) with the first temperature being between at least 5 °C to no more than about 30 °C lower than the initial temperature. In some embodiments, the heat exchanger can be a convection / conduction heat exchanger (e.g., a heat exchanger configured to utilize the transmission of thermal energy from a surface by way of the motion of a suitable process stream relative to the surface of an enclosure containing the BL feed). In some implementations, the suitable process stream can be a flocculated BL feed as described in greater detail above with reference to the system 1000 shown in FIG.2. In some embodiments, the suitable process stream heat can be a permeate or a concentrate produced in a graphene oxide (GO) membrane filtration system, as described in greater detail above with reference to the system 1000 shown in FIG. 2. In some embodiments,23326750747Agent’s File Ref. VSLC-014 / 01WO 331287-2099 the suitable stream can be a chilled fluid (e.g., chilled water or antifreeze). In some embodiments, the suitable stream can be a combination of some or all of the above.

[0048] At 13, the method 10 includes flocculating, at the flocculation unit, suspended solids in the BL feed to produce a flocculated BL feed. In some embodiments, the flocculation unit can be configured to initiate (and conduct) a coagulation process and / or reaction with the BL feed at the first temperature and pH. In some embodiments, the one or more coagulant reagent(s) can be added and / or mixed to the BL feed in the flocculation unit. The one or more coagulant reagent(s) can be selected to neutralize negative charges present in the particles forming the suspended solids in the BL feed and facilitate the formation of micro flocs. The one or more coagulant reagent(s) can include species including, but not limited to aluminum chlorohydrate (ACH), aluminum sulfate (Alum), ferric chloride, ferric sulfate, polydiallyldimethylammonium chloride (PolyDADMAC), polyaluminum chloride (PAC), or combinations thereof. In some embodiments, the one or more coagulant reagent(s) can be added to the BL feed according to predetermined amounts and / or dosages, with the dosages being at least about 1 ppb to no more than about 25 ppm. The ranges for the dosage of the one or more coagulant reagent(s) have been disclosed above in greater detail with reference to the system 1000 shown in FIG. 2.

[0049] In some embodiments, the flocculation unit can be configured to initiate a flocculation process with the BL feed at the first temperature and pH. In some implementations, the flocculation unit can be configured to initiate a flocculation process after completing a coagulation process and / or reaction (e.g., conducting a coagulation step followed by a flocculation step). For example, in some embodiments the BL feed can be received in the flocculation unit and then be subjected to a coagulation process and / or reaction by adding and / or mixing coagulant reagent(s) to neutralize the negative charges of the suspended solid particles in the BL feed and form micro flocs. A flocculant (or a mixture of flocculants) can then be added to the BL feed to initiate a flocculation process. During the flocculation process, the flocculant can be dispersed within the BL feed to facilitate the agglomeration of the micro flocs produced in the coagulation process and / or reaction, forming large size flocs that can then be separated and / or removed in a downstream process. In some embodiments, the flocculation unit can be configured to initiate a flocculation process without conducting a coagulation process and / or reaction. That is to say, in some embodiments the BL feed can be received in the flocculation unit and be directly exposed to a flocculant (or a mixture of flocculants) without coagulating the BL feed (e.g., without introducing coagulation reagent(s)).24326750747Agent’s File Ref. VSLC-014 / 01WO 331287-2099

[0050] In some embodiments, the flocculant can be composed of a polymer with a molecular weight (MW) between 70 and 20,000 kDa. For example, in some embodiments, the flocculant can be a homopolymer with at least some cationic charge. In some embodiments, the flocculant (or a mixture of flocculants) can be added to the BL feed in the flocculation unit according to predetermined quantities and / or dosages. The selection of the specific flocculant and its respective dosage can be determined based on the characteristics of BL feed, such as for example, the pH, the TSS, lignin concentration, soap concentration, conductivity, average particle size of the suspended solids, suspended solids composition (e.g., % cellulose, ash content, fiber count, etc.), salinity and / or the first (or the second) temperature. In some embodiments, the dosage of flocculant (or mixture of flocculants) added and / or mixed with the BL feed 100 can be at least about 50 ppb to no more than about 50 ppm.

[0051] In some embodiments, the flocculant (or mixture of flocculants) can be added to the BL feed in the flocculant unit under rapid mixing conditions. In some embodiments, the flocculants (or mixture of flocculants) can be added to the BL feed in the flocculation unit while providing different levels of agitation for suitable periods of time. For example, in some embodiments the flocculant (or mixture of flocculants) can be added the BL feed in the flocculation unit at a first rotational speed for a first period of time. The flocculant can then be allowed to continue mixing with the BL feed at a second rotational speed, different from the first rotational speed, for a second period of time. In some embodiments, the first rotational speed can be higher than the second rotational speed. In some embodiments, the first and / or the second rotational speed can be at least about 50 rpm, to no more than about 500 rpm, inclusive of all values and ranges therebetween. In some embodiments, the first and / or the second period of time can be at least about 0.5 min to no more than about 30 min, inclusive of all values and ranges therebetween. The ranges for the dosage of the flocculant (or a mixture of flocculants), the rotational speeds, and the periods of time (e.g., time intervals) for mixing the flocculant (or mixture of flocculants) have been disclosed above in greater detail with reference to the system 1000 shown in FIG. 2. At 14, the method 10 further includes directing the flocculated BL feed to a floc removal unit disposed downstream of the flocculation unit. In some embodiments, the floc removal unit can be similar to and / or the same as the floc removal unit 120 disclosed with reference to the system 1000 shown in FIG. 2.[0052 [ At 15, the method 10 includes separating, at the floc removal unit and from the flocculated BL feed, a floc containing at least a portion of the suspended solids, to produce a conditioned BL feed characterized by a second amount of total suspended solids (TSS). In25326750747Agent’s File Ref. VSLC-014 / 01WO 331287-2099 some embodiments, the floc separated from the flocculated BL feed can contain a percentage and / or fraction of the suspended solids that were initially present in the BL feed. For example, in some embodiments the floc can contain and / or include at least about 8% of the TSS that were initially present in the BL feed. In some embodiments, the floc can contain at least about 50% of the fiber initially included in the BL feed. The ranges for the % of solids in the floc have been disclosed above in greater detail with reference to the system 1000 shown in FIG. 2. In some embodiments, the floc removal unit can include one or more systems configured to separate the floc from the flocculated BL feed via various methods. For example, in some embodiments the flocculation unit can include one or more systems configured to separate the floc via sedimentation, clarification, centrifugation, filtration, and / or air injection methods. In some embodiments, the TSS present in the conditioned BL feed 102 can be no more than about 5 ppm. Finally, At 16, the method 10 can optionally include directing the conditioned BL feed to a Graphene Oxide (GO) membrane filtration system. In some embodiments, the conditioned BL feed can be produced in the floc removal unit without reducing the temperature and / or pH with respect to the BL feed 100 described above with reference to the method 10 at 11. Said in other words, in some embodiments the conditioned BL feed can be produced in the floc removal unit at the pH and the first temperature.

[0053] While the present teachings have been described in conjunction with various embodiments and examples, it is not intended that the present teachings be limited to such embodiments or examples. On the contrary, the present teachings encompass various alternatives, modifications, and equivalents, as will be appreciated by those of skill in the art.

[0054] While various inventive embodiments have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and / or structures for performing the function and / or obtaining the results and / or one or more of the advantages described herein, and each of such variations and / or modifications is deemed to be within the scope of the inventive embodiments described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and / or configurations will depend upon the specific application or applications for which the inventive teachings is / are used. Those skilled in the art will recognize many equivalents to the specific inventive embodiments described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, inventive embodiments may be practiced otherwise than as26326750747Agent’s File Ref. VSLC-014 / 01WO 331287-2099 specifically described and claimed. Inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and / or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and / or methods, if such features, systems, articles, materials, kits, and / or methods are not mutually inconsistent, is included within the inventive scope of the present disclosure.

[0055] All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and / or ordinary meanings of the defined terms.10056] The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.” Any ranges cited herein are inclusive.

[0057] The terms “substantially,” “approximately,” and “about” used throughout this Specification and the claims generally mean plus or minus 10% of the value stated, e.g., about 100 would include 90 to 110.10058 [ The phrase “and / or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Multiple elements listed with “and / or” should be construed in the same fashion, i.e., “one or more” of the elements so conjoined. Other elements may optionally be present other than the elements specifically identified by the “and / or” clause, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, a reference to “A and / or B”, when used in conjunction with open-ended language such as “comprising” may refer, in one embodiment, to A only (optionally including elements other than B); in another embodiment, to B only (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.

[0059] As used herein in the specification and in the claims, “or” should be understood to have the same meaning as “and / or” as defined above. For example, when separating items in a list, “or” or “and / or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of’ or “exactly one of,” or, when used in the claims, “consisting of,” will refer to the inclusion of exactly one element of a number or list of elements. In general, the term “or” as used herein shall only be27326750747Agent’s File Ref. VSLC-014 / 01WO 331287-2099 interpreted as indicating exclusive alternatives (i.e., “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of,” “only one of,” or “exactly one of.” “Consisting essentially of,” when used in the claims, shall have its ordinary meaning as used in the field of patent law.

[0060] As used herein in the specification and in the claims, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, “at least one of A and B” (or, equivalently, “at least one of A or B,” or, equivalently “at least one of A and / or B”) may refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc.|0061 ] As used herein, “wt.%” refers to weight percent.|0062] In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” “composed of,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of’ and “consisting essentially of’ shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03.

[0063] As used herein, the term “room temperature” can refer to a temperature of about 15 °C, about 16 °C, about 17 °C, about 18 °C, about 19°C, about 20 °C, about 21 °C, about 22 °C, about 23 °C, about 24 °C, or about 25 °C. In some embodiments, the room temperature is about 20 °C.

[0064] As used herein, the term “substantially the same” refers to a first value that is within 10% of a second value. For example, if A is substantially the same as B, and B is 100, A can28326750747Agent’s File Ref. VSLC-014 / 01WO 331287-2099 have a value ranging from 90 to 110. If A is substantially the same as B, and B is 200, A can have a value ranging from 180 to 220.

[0065] As used herein, the term “about” and “approximately” generally mean plus or minus 10% of the value slated, e.g., about 250 pm would include 225 pm to 275 pm, about 1,000 pm would include 900 pm to 1,100 pm. As used herein in the specification and in the claims, the term “aspect ratio” can be defined as a ratio of an in-plane lateral dimension to the thickness of the final product. For example, if a graphene oxide sheet has an average lateral dimension of 300 pm and a thickness of 200 nm, the sheet size to thickness ratio, or “aspect ratio” can be defined as 300,000 / 200, or 1,500.

[0066] The claims should not be read as limited to the described order or elements unless stated to that effect. It should be understood that various changes in form and detail may be made by one of ordinary skill in the art without departing from the spirit and scope of the appended claims. All embodiments that come within the spirit and scope of the following claims and equivalents thereto are claimed.ExamplesExample 1.

[0067] A black liquor (BL) feed including an amount of total suspended solids (TSS) of 50 ppm is received at a temperature of 95 °C and a pH 12.9 on a flocculation unit similar to and / or the same as the flocculation unit 110 described above with reference to FIG.2. The BL feed is stirred via an agitation system (e.g., a mechanical agitator, propeller, or the like) to ensure the suspended solids are well dispersed. A polyacrylamide flocculant cationic copolymer (DREWFLOC™ 410 or 443) with a partial cationic charge dissolved in water at a concentration of 0.5 wt.% is added to the BL feed at a dosage of 10 ppm (mass of dry flocculant copolymer / mass of black liquor). The flocculant is allowed to mix with the BL feed while agitating under rapid mixing conditions operating the agitation system at a rotational speed of 300 rpm for 30 seconds. The BL feed is subsequently allowed to continue mixing under slow conditions with the agitation system operating at a rotational speed of 50 rpm for 5 min, to produce a flocculated BL feed. The resulting flocculated BL feed is then clarified on a floc removal unit similar to and / or the same as the floc removal unit disclosed with reference to FIG. 2, to separate a floc from the flocculated BL feed and produce a conditioned BL feed having an amount of total suspended solids (TSS) of about 5 ppm.29326750747Agent’s File Ref. VSLC-014 / 01WO 331287-2099Example 2

[0068] A black liquor (BL) feed including an amount of total suspended solids (TSS) of 800 ppm is received at a temperature of 80 °C at a flocculation unit. The BL feed is stirred via an agitation system (e.g., a mechanical agitator, propeller, or the like) to ensure the suspended solids are well dispersed. A polyacrylamide flocculant cationic copolymer (SUPERFLOC® C-1592RSP, or 4512) with a partial cationic charge dissolved in water at a concentration of 0.5 wt.% is added to the BL feed at a dosage of 13 ppm (mass of dry of flocculant copolymer / mass of black liquor). The flocculant is allowed to mix with the BL feed while agitating under rapid mixing conditions operating the agitation system at a rotational speed of 300 rpm for 90 seconds. The BL feed is subsequently allowed to continue mixing under slow conditions with the agitation system operating at a rotational speed of 50 rpm for 20 min, to produce a flocculated BL feed. The resulting flocculated BL feed is then clarified in a floc removal unit to separate a floc from the flocculated BL feed and produce a conditioned BL feed having an amount of total suspended solids (TSS) of about 3 ppm.Example 3 f0069| A black liquor (BL) feed including an amount of total suspended solids (TSS) of 250 ppm is received at a temperature of 80 °C in a flocculation unit. The BL feed is stirred via an agitation system (e.g., a mechanical agitator, propeller, or the like) to ensure the suspended solids are well dispersed. A polydiallyldimethylammonium chloride (PolyDADMAC) coagulant dissolved in water at a concentration of 0.5 wt.% is added to the BL feed with a dosage of 5-15 ppm of coagulant to BL feed. A polyacrylamide flocculant copolymer (SUPERFLOC® C1592RSP or 4512) with a partial cationic charge dissolved in water at a concentration of 0.5 wt.% is also added to the BL feed at a dosage of 7 ppm (mass of dry flocculant copolymer / mass of black liquor). The coagulant and the flocculant are allowed to mix with the BL feed under rapid mixing conditions by operating the agitation system at a rotational speed of 300 rpm for 90 seconds. The BL feed is subsequently allowed to continue mixing under slow conditions with the agitation system operating at a rotational speed of 50 rpm for 20 min, to produce a flocculated BL feed. The resulting flocculated BL feed is then clarified in a floc removal unit to separate a floc from the flocculated BL feed and produce a conditioned BL feed having an amount of total suspended solids (TSS) of about 5 ppm.30326750747Agent’s File Ref. VSLC-014 / 01WO 331287-2099Example 4

[0070] A kraft black liquor (BL) feed including an amount of total suspended solids (TSS) of 150ppm is received at a temperature of 95°C and a flow rate of 20 GPM into a lamellar plate clarifier. A poly(diallyldimethylammonium chloride) (PolyDADMAC) coagulant dissolved in water at a concentration of 0.5 wt.% is added to the BL feed with a dosage of 2-7 ppm of coagulant to BL feed. A polyacrylamide flocculant copolymer (DREWFLOC© 411 or 410) with a partial cationic charge dissolved in water at a concentration of 0.5 wt.% is also added to the BL feed at a dosage of 3-7ppm (mass of dry flocculant copolymer / mass of black liquor). The coagulant and flocculant are allowed to mix with the BL feed in a rapid mixing chamber via an agitation system (e.g., a mechanical agitator, propeller, or the like) by operating the agitation system at a rapid mixing speed (i.e. a high rpm setting) for 2 min. The BL feed is subsequently allowed to continue mixing under slow conditions by operating the agitation system at a second slower speed for 3 min to produce a flocculated BL feed. The resulting flocculated BL feed then passes through a plate region of a clarifier to separate a floc from a set of bottom plates of the clarifier and a weak black liquor (WBL) feed from a set of top plates of the clarifier, the WBL feed having an amount of total suspended solids (TSS) of about 3 ppm. The WBL feed then passes through a MMF polishing step to produce a final BL feed having an amount of total suspended solids (TSS) of about Oppm.Example 5[00711 A semi-chem black liquor (BL) feed including an amount of total suspended solids (TSS) of 2000ppm is received at a temperature of 75°C and a flow rate of 10 GPM into a lamellar plate clarifier. A coagulant dissolved in water at a concentration of 0.5 wt.% is added to the BL feed at a predetermined dosage. A polyacrylamide flocculant copolymer (DREWFLOC© 411 or 410) with a partial cationic charge dissolved in water at a concentration of 0.5 wt.% is added to the BL feed at a dosage of 10 ppm (mass of dry flocculant / mass of black liquor). The coagulant and the flocculant are allowed to mix with the BL feed in a rapid mixing chamber via an agitation system (e.g., a mechanical agitator, propeller, or the like) by operating the agitation system at a rapid mixing speed (i.e. a high rpm setting) for 4 min. The BL feed is then mixed under slower mixing conditions at a second slower mixing rate for 6 min resulting in a flocculated BL feed. The flocculated BL feed then passes through a plate region of a clarifier to separate a floc from a set of bottom plates of the clarifier and a weak black liquor (WBL) feed from a set of top plates of the clarifier, the WBL feed having an31326750747Agent’s File Ref. VSLC-014 / 01WO 331287-2099 amount of total suspended solids (TSS) of about 5 ppm. The WBL feed then passes through a MMF polishing step to produce a final BL feed having an amount of total suspended solids (TSS) of about Oppm.32326750747

Claims

Agent’s File Ref. VSLC-014 / 01WO 331287-2099CLAIMS1. A method, comprising: receiving, at a flocculation unit, a black liquor feed characterized by a first amount of total suspended solids (TSS), a temperature, and a pH; flocculating, at the flocculation unit, suspended solids included in the black liquor feed to produce a flocculated black liquor feed; directing the flocculated black liquor feed to a floc removal unit disposed downstream of the flocculation unit; separating, at the floc removal unit and from the flocculated black liquor feed, a floc containing at least a portion of the suspended solids, to produce a conditioned black liquid feed, the conditioned black liquor feed characterized by a second amount of total suspended solids (TSS) of no more than about 5 ppm; and directing the conditioned black liquor feed to a Graphene Oxide (GO) membrane filtration system.

2. The method of claim 1, wherein the black liquor feed includes at least one of sodium sulfate, sodium carbonate, sodium hydrosulfide, sodium thiosulfate, sodium hydroxide, residual fibers from the pulping process, hemicellulose, cellulose, or lignin.

3. The method of claims 1 or 2, wherein the first amount of total suspended solids (TSS) is at least about 50 ppm and no more than about 8000ppm.

4. The method of any one of claims 1-3, wherein the temperature is at least about 70 °C.

5. The method of any one of claims 1-4, wherein flocculating suspended solids included in the black liquor feed includes mixing a coagulant reagent.

6. The method of claim 5, wherein the coagulant reagent is at least one of aluminum chlorohydrate (ACH), aluminum sulfate (Alum), ferric chloride, ferric sulfate, polydiallyldimethylammonium chloride (PolyDADMAC), polyaluminum chloride(PAC), epichlorohydrindimethylamine (EPI-DMA) or a combinations thereof.33326750747Agent’s File Ref. VSLC-014 / 01WO 331287-20997. The method of claim 5 or 6, wherein the coagulant reagent is mixed at a dosage of at least about 0.5 ppm to less than about lOOppm.

8. The method of any one of claims 1-7, wherein flocculating suspended solids included in the black liquor feed includes mixing a flocculant.

9. The method of claim 8, wherein the flocculant is copolymer including at least a first and a second comonomer, the first comonomer being a cationic comonomer.

10. The method of claim 9, wherein the first comonomer accounts for at least about 10% to no more than about 70% of the copolymer.

11. The method of any one of claims 1-10, wherein the temperature is a first temperature, the method further comprising: cooling the black liquor feed from an initial temperature to the first temperature.

12. The method of claim 11, wherein the first temperature is between at least about 5 °C to no more than about 30 °C lower than the initial temperature.

13. The method of claim 11 or 12, wherein the flocculation unit includes a heat exchanger and a flocculation device, the heat exchanger fluidically coupled to the flocculation device and disposed upstream to the flocculation device, and cooling the black liquor feed includes: receiving, at the heat exchanger, the black liquor feed at the initial temperature; transferring, via a surface of the heat exchanger, heat from the black liquor feed to a cooling stream flowing through the heat exchanger such that the black liquor feed is cooled from the initial temperature to the first temperature; and directing the black liquor at the first temperature to the flocculation device, the flocculation device configured to flocculate the black liquor feed.

14. The method of claim 13, wherein the cooling stream is the flocculated black liquor feed.

15. The method of any one of claims 1-14, wherein the temperature of the conditioned black liquor feed is at least about 60 °C.34326750747Agent’s File Ref. VSLC-014 / 01WO 331287-209916. The method of any one of claims 1-15, wherein: the floc removal unit includes a clarifier, the clarifier having an inlet, an outlet, and a sludge bed configured to accommodate the floc therein; a temperature difference between the inlet and the outlet of the clarifier is no more than about 10 ° C; and a temperature difference horizontally across a length of the sludge bed is no more than about 30C.

17. A method, comprising: receiving, at a flocculation unit, a black liquor feed characterized by a first amount of total suspended solids (TSS), a temperature, and a pH; measuring, with a fiber measurement device coupled to the flocculation unit, a content of fibers included in the first amount of total suspended solids (TSS); mixing, at the flocculation unit, a dosage of a coagulant reagent with the black liquor feed to produce a flocculated black liquor feed, the dosage of the coagulant determined based on the measured content of fibers; directing the flocculated black liquor feed to a floc removal unit disposed downstream of the flocculation unit; separating, at the floc removal unit and from the flocculated black liquor feed, a floc containing at least a portion of the suspended solids, to produce a conditioned black liquid feed, the conditioned black liquor feed characterized by a second amount of total suspended solids (TSS) of no more than about 5 ppm; and directing the conditioned black liquor feed to a Graphene Oxide (GO) membrane filtration system.

18. The method of claim 17, wherein the black liquor feed includes at least one of sodium sulfate, sodium carbonate, sodium hydrosulfide, sodium thiosulfate, sodium hydroxide, residual fibers from the pulping process, hemicellulose, cellulose, or lignin.

19. The method of claims 17 or 18, wherein the first amount of total suspended solids (TSS) is at least about 50 ppm and no more than about 8000ppm.

20. The method of any one of claims 17-19, wherein the temperature is at least about 7035326750747Agent’s File Ref. VSLC-014 / 01WO 331287-209921. The method of any one of claims 17-20, wherein coagulant reagent is at least one of aluminum chlorohydrate (ACH), aluminum sulfate (Alum), ferric chloride, ferric sulfate, polydiallyldimethylammonium chloride (PolyDADMAC), polyaluminum chloride(PAC), epichlorohydrindimethylamine (EPI-DMA) or a combinations thereof.

22. The method of any one of claims 17-21, further comprising: mixing, at the flocculation unit, a dosage of a flocculant with the black liquor feed to produce the flocculated black liquor feed, the dosage of the flocculant determined based on the measured content of fibers.

23. The method of claim 22, wherein the flocculant is copolymer including at least a first and a second comonomer, the first comonomer being a cationic comonomer.

24. The method of claim 23, wherein the first comonomer accounts for at least about 10% to no more than about 70% of the copolymer.

25. The method of any one of claims 17-24, wherein the temperature is a first temperature, the method further comprising: cooling the black liquor feed from an initial temperature to the first temperature.

26. The method of claim 25, wherein the first temperature is between at least about 5 °C to no more than about 30 °C lower than the initial temperature.

27. The method of claim 25 or 26, wherein the flocculation unit includes a heat exchanger and a flocculation device, the heat exchanger fluidically coupled to the flocculation device and disposed upstream to the flocculation device, and cooling the black liquor feed includes: receiving, at the heat exchanger, the black liquor feed at the initial temperature; transferring, via a surface of the heat exchanger, heat from the black liquor feed to a cooling stream flowing through the heat exchanger such that the black liquor feed is cooled from the initial temperature to the first temperature; and directing the black liquor at the first temperature to the flocculation device, the flocculation device configured to flocculate the black liquor feed.

28. The method of claim 27, wherein the cooling stream is the flocculated black liquor feed.36326750747Agent’s File Ref. VSLC-014 / 01WO 331287-209929. The method of any one of claims 17-28, wherein the temperature of the conditioned black liquor feed is at least about 60 °C.

30. The method of any one of claims 1-29, wherein: the floc removal unit includes a clarifier, the clarifier having an inlet, an outlet, and a sludge bed configured to accommodate the floc therein; a temperature difference between the inlet and the outlet of the clarifier is no more than about 10 ° C; and a temperature difference horizontally across a length of the sludge bed is no more than about 30C.326750747

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