Method for treating methanolic alkaline liquid

Abstract

This technology relates to a method for treating an alkaline liquid comprising methanol and one or more components selected from: sulfur-containing organic compounds, hydrogen sulfide (H2S), ammonia, acetone, alcohols such as ethanol, extracts such as turpentine, and mixtures thereof. The method comprises the following steps performed sequentially: contacting the liquid with an oxidizing agent, whereby at least a portion of the sulfur compounds in the liquid are oxidized to their oxidized forms, thereby providing an oxidized liquid; and contacting the oxidized liquid with an acidifying agent, whereby the ammonia present in the oxidized liquid reacts to form ammonium sulfate, providing an acidified liquid substantially free of polymeric terpenes.

Description

Technical Field

[0001] This invention relates to a method for treating an alkaline liquid containing methanol. This invention also relates to a system for treating an alkaline liquid containing methanol. Background Technology

[0002] In pulp mills, methanol is primarily formed during the sulfate pulping process by removing methanol from 4-O-methylglucuronic acid residues in hemicellulose via alkaline catalysis. Methanol is also formed during O2 delignification, through the oxidation of phenolic lignin. The methanol yield is approximately 6-15 kg / ADT, depending on the wood type and pulping process. Pulping also produces organosulfur compounds, as sulfides and hydrogen sulfide ions react with lignin. The methanol and other volatile compounds formed during pulping ultimately enter black liquor, a byproduct of the pulping process containing an aqueous solution of lignin residues, hemicellulose, and inorganic chemicals, as well as organic and inorganic solids. Due to its high volatility, methanol evaporates along with water and other volatile substances and condenses in the foul liquor of the evaporation equipment.

[0003] The pulp mill generates sludge from black liquor evaporation. This sludge is stripped to produce a higher-quality stripper liquor with a total reduced sulfur (TRS) content ≤5 mg / L. As a result of the stripping, methanol from the sludge ultimately enters the stripper tail gas, which is then sent to a methanol liquefaction unit. In the methanol liquefaction unit, the methanol concentration is increased to 60-80%.

[0004] In addition to methanol, the sludge contains volatile sulfur compounds such as hydrogen sulfide (H₂S), methanethiol (MM), dimethyl sulfide (DMS), and dimethyl disulfide (DMDS). After stripping, some of these volatile sulfur compounds remain in the methanol, referred to as crude methanol, while a larger portion remains in the concentrated non-condensable gases after stripping. The sludge also contains less volatile sulfur compounds, which remain with the methanol after processing in the stripper. The amount of less volatile sulfur compounds in the sludge is a fraction of the total volatile sulfur compounds. The recovered methanol concentration is quite high (>74% by weight, based on crude methanol weight), but as previously mentioned, it typically contains more than 5% by weight of sulfur compounds (based on crude methanol weight). Water, ethanol, acetone, ammonia (NH₃), and turpentine compounds are other major impurities. Several methods have been developed to remove nitrogen and sulfur and provide purified methanol. However, existing techniques involving acidifying and then oxidizing a liquid can lead to the formation of polymeric terpene compounds (sticky substances) that can clog, for example, distillation columns, causing equipment downtime for periodic cleaning. Summary of the Invention

[0005] This invention is defined by the features of the independent claims. Some specific embodiments are defined in the dependent claims.

[0006] According to a first aspect of the invention, a method for treating a methanol-containing alkaline liquid is provided. In addition to methanol, the alkaline liquid also contains one or more components selected from: sulfur-containing organic compounds, hydrogen sulfide (H2S), ammonia, acetone, alcohols such as ethanol, extracts such as turpentine, and mixtures thereof. The method comprises the following steps performed sequentially: contacting the liquid with an oxidizing agent, whereby at least a portion of the sulfur compounds in the liquid are oxidized to their oxidized forms, thereby providing an oxidized liquid; and contacting the oxidized liquid with an acidifying agent, whereby the ammonia present in the oxidized liquid reacts to form ammonium sulfate, providing an acidified liquid substantially free of polymeric terpenes.

[0007] According to another aspect of the invention, a system for processing a methanol-containing alkaline liquid is provided. In addition to methanol, the alkaline liquid also contains one or more components selected from: sulfur-containing organic compounds, hydrogen sulfide (H2S), ammonia, acetone, alcohols such as ethanol, extracts such as turpentine, and mixtures thereof. The system includes an oxidation unit and an acidification unit. The oxidation unit has an inlet configured to receive the alkaline liquid and a second inlet configured to receive an oxidizing agent. The oxidation unit is suitable for an oxidation reaction. The oxidation unit has an outlet for feeding the contents of the oxidation unit to the inlet of the acidification unit, the acidification unit inlet being configured to receive the oxidized alkaline liquid feed from the oxidation unit. The acidification unit has a second inlet configured to receive an acidifying agent. The acidification unit has an outlet configured to feed an acidified stream substantially free of polymerized terpenes to further processing.

[0008] Significant benefits have been gained from this invention. A simple, easy-to-apply, low-cost, and industrially applicable treatment method under mild conditions provides a treated methanol liquid that is substantially free of polymeric terpenes that can clog plant equipment such as distillation columns.

[0009] Other features and advantages will become apparent from the following description. Attached Figure Description

[0010] Figure 1 This is a flowchart illustrating a method for treating an alkaline liquid containing methanol according to at least some embodiments.

[0011] Figure 2 This is a flowchart illustrating a method for treating an alkaline liquid containing methanol according to at least some embodiments.

[0012] Figure 3 This is a flowchart illustrating a method for treating an alkaline liquid containing methanol according to at least some embodiments.

[0013] Figure 4 This is a flowchart illustrating a method for treating an alkaline liquid containing methanol according to at least some embodiments. Detailed Implementation

[0014] For the purposes of this invention, the liquid to be treated can refer to any methanol-containing alkaline liquid from a pulp mill, such as liquefied stripper tail gas (gas stripped from sludge), liquefied methanol, crude methanol from a methanol plant, sludge, or any type of liquid or condensate, such as sludge condensate or condensate formed from stripper tail gas, etc. In practice, the implementation of this method is not limited to liquids from pulp mills, but includes any alkaline liquid containing methanol and one or more components selected from: sulfur-containing organic compounds, ammonia, acetone, alcohols such as ethanol, extracts such as turpentine, and other non-structural components of lignocellulose materials, which have not yet been treated in the acidification step.

[0015] Detailed description

[0016] This invention relates to a method for treating an alkaline liquid comprising methanol and one or more components selected from: sulfur-containing organic compounds, hydrogen sulfide (H2S), ammonia, acetone, alcohols such as ethanol, extracts such as turpentine, and mixtures thereof. The method comprises the following steps performed sequentially: contacting the liquid with an oxidizing agent, whereby at least a portion of the sulfur compounds in the liquid are oxidized to their oxidized forms, thereby providing an oxidized liquid; and contacting the oxidized liquid with an acidifying agent, whereby the ammonia present in the oxidized liquid reacts to form ammonium sulfate, providing an acidified liquid substantially free of polymeric terpenes.

[0017] Figure 1 This is a flowchart illustrating a method for processing alkaline liquids according to at least some embodiments of the present invention.

[0018] An alkaline liquid 10 containing methanol and one or more components selected from the following, along with water 20, is fed into a decantation unit 100: sulfur-containing organic compounds, hydrogen sulfide (H2S), ammonia, acetone, alcohols such as ethanol, extracts such as turpentine, and mixtures thereof. Turpentine 30 is decanted from the decantation unit and sent to further processing. The decanted methanol stream 300 is then fed from the decantation unit 100 to an oxidation unit 101, where it is contacted with an oxidant 40 to provide an oxidized stream 310, which is then sent to a further decantation unit 102, to which water 50 is added. Further turpentine 60 is decanted from the oxidized stream 310 in the further decantation unit 102, and the decanted oxidized stream 320 is fed from the further decantation unit 102 to an acidification unit 103. The decanted oxidized feed stream 320 is then contacted with acidifier 70, and the acidified feed stream 80 is sent from acidification unit 103 to further processing. The acidified feed stream 80 is substantially free of polymeric terpenes.

[0019] Figure 2 This is a flowchart illustrating a method for processing alkaline liquids according to at least some embodiments of the present invention.

[0020] An alkaline liquid 10 containing methanol and one or more components selected from the group consisting of sulfur-containing organic compounds, hydrogen sulfide (H2S), ammonia, acetone, alcohols such as ethanol, extracts such as turpentine, and mixtures thereof is fed into a decantation unit 100 along with water 20. Turpentine 30 is decanted from the decantation unit 100 to provide a decanted methanol stream 300. The decanted methanol stream 300 is fed from the decantation unit 100 into an oxidation unit 101, where it is contacted with an oxidant 40. A stream 90 of the oxidation product is sent to further processing, and an oxidized stream 330 is sent to a further decantation unit 102. Water 50 is added to the further decantation unit 102, and further turpentine 60 is decanted to provide a decanted oxidized stream 340 free of oxidation product 90. This stream 340 is fed from the further decantation unit 102 to an acidification unit 103, where it is contacted with an acidifier 70. The acidified feed stream 110, which mainly contains alcohols and acetone, is sent to further processing, and ammonium sulfate 120 is recovered and sent to further processing. The acidified feed stream 110 is essentially free of polymeric terpene compounds.

[0021] Figure 3 This is a flowchart illustrating a method for processing alkaline liquids according to at least some embodiments of the present invention.

[0022] An alkaline liquid 10 containing methanol and one or more components selected from the following are fed together with water 20 into a decantation unit 100: sulfur-containing organic compounds, hydrogen sulfide (H2S), ammonia, acetone, alcohols such as ethanol, extracts such as turpentine oil, and mixtures thereof. Turpentine oil 30 is decanted from the decantation unit 100 to provide a decanted methanol stream 300. The decanted methanol stream 300 is then fed from the decantation unit 100 into an oxidation and acidification unit 104. The decanted methanol stream 300 is then first contacted with an oxidant 40, followed by an acidifier 70, thereby forming an acidified stream 80, which is then sent for further processing. The acidified stream 80 is substantially free of polymeric terpenes.

[0023] Figure 4 This is a flowchart illustrating a method for processing alkaline liquids according to at least some embodiments of the present invention.

[0024] An alkaline liquid 10 containing methanol and one or more components selected from the following: sulfur-containing organic compounds, hydrogen sulfide (H2S), ammonia, acetone, alcohols such as ethanol, extracts such as turpentine, and mixtures thereof, is fed into an oxidation unit 101, where the alkaline liquid 10 is contacted with an oxidizing agent 40. An oxidizing stream 310 is then fed from the oxidation unit 101 to an acidification unit 103, where it is contacted with an acidifying agent 70, thereby forming an acidified stream 80, which is then sent for further processing. The acidified stream 80 is substantially free of polymeric terpenes.

[0025] As described above, this technology relates to a method for treating an alkaline liquid comprising methanol and one or more components selected from: sulfur-containing organic compounds, hydrogen sulfide (H2S), ammonia, acetone, alcohols such as ethanol, extracts such as turpentine, and mixtures thereof. The method comprises the following steps performed sequentially: contacting the liquid with an oxidizing agent, whereby at least a portion of the sulfur compounds in the liquid are oxidized to their oxidized forms, thereby providing an oxidized liquid; and contacting the oxidized liquid with an acidifying agent, whereby the ammonia present in the oxidized liquid reacts to form ammonium sulfate, providing an acidified liquid substantially free of polymeric terpenes. It has been surprisingly found that by performing the oxidation step prior to the acidification step, the likelihood of residual terpenes in the liquid to be treated polymerizing to form a viscous substance containing polymeric terpenes is significantly reduced. It has been found that in liquids where the acidification step is performed prior to the oxidation step, the amount of polymeric terpenes reaches levels that cause blockages in plant equipment (e.g., distillation columns), requiring regular and periodic cleaning.

[0026] As described above, methanol-containing alkaline liquids may contain hydrogen sulfide and sulfur-containing organic compounds. These compounds include methanethiol and dimethyl sulfide. In the oxidation phase, methanethiol (MM) is oxidized to dimethyl sulfide (DMDS), which is then oxidized to dimethyl sulfoxide; hydrogen sulfide is oxidized to sulfur dioxide; dimethyl disulfide is oxidized to dimethyl sulfoxide, which is then oxidized to dimethyl sulfone. Another possible oxidation product of MM and DMDS is methanesulfonic acid. It is presumed that the formation of sulfate ions in the oxidation phase reduces the amount of acidifying agent required to protonate ammonia (NH3) in the acidification phase. In the acidification phase, ammonia reacts to form ammonium sulfate. Optionally, water is added to maintain the concentration of ammonium sulfate below the concentration at which precipitation occurs.

[0027] In one embodiment, the alkaline liquid comprises methanol, ammonia, sulfur-containing organic compounds, hydrogen sulfide, and one or more components selected from acetone, alcohols such as ethanol, extracts such as turpentine, and mixtures thereof.

[0028] In one embodiment, the acidified liquid is sent for further processing. In another embodiment, ammonium sulfate is removed from the acidified liquid, thereby recovering the ammonium sulfate and the methanol-containing liquid. The recovered ammonium sulfate has numerous uses; for example, it can be used as a fertilizer, food additive, flame retardant, vaccine ingredient, cleaning additive, pH buffer, adhesive in wall panels, and dough conditioner in bread products. Ammonium sulfate has many other uses, and the recovered ammonium sulfate is suitable for these uses. The recovered methanol-containing liquid can be used in a variety of applications. In pulp mills, the recovered methanol-containing liquid can be used as fuel in lime kilns, as auxiliary fuel in burners, or as auxiliary fuel in recovery boilers. Using the recovered methanol-containing liquid as fuel in recovery boilers helps reduce sulfur and NOx emissions from recovery boilers, which is becoming an increasingly desirable goal as environmental regulations become more stringent. The recovered methanol-containing liquid is also suitable for use outside of pulp mills, for example, as fuel. Optionally, the recovered methanol-containing liquid can be further processed, such as by distillation, to remove alcohols (e.g., ethanol) and acetone from the methanol and provide a purified methanol stream suitable for conversion into a variety of industrially useful chemicals, as well as as an ideal fuel.

[0029] In one embodiment, the liquid is diluted with water before being brought into contact with the oxidant. This further step of diluting the liquid with water before bringing it into contact with the oxidant reduces the exothermic effect of the step of bringing the liquid into contact with the oxidant.

[0030] In another embodiment, turpentine oil is decanted from the liquid before contacting it with the oxidant. This further step of decanting turpentine oil from the liquid before contacting it with the oxidant provides the additional benefit of removing at least a portion of the terpenes from the liquid. Naturally, the reaction between the terpenes and the oxidant is reduced, thereby reducing the amount of oxidant added to the liquid for oxidizing sulfur-containing compounds. In one embodiment, the step of diluting the liquid with water before contacting it with the oxidant promotes and improves the decanting of turpentine oil.

[0031] In one embodiment, the method includes the further steps of adding water to the oxidizing liquid before contacting it with an acidifying agent and optionally decanting turpentine oil from the oxidizing liquid. Upon adding water to the oxidizing liquid, a portion of the turpentine oil remaining in the liquid separates from the liquid and is suitable for decanting, thereby reducing the amount of terpenes in the liquid that could adversely react in the subsequent acidification step (in which polymerized terpenes are formed). Due to the reduced amount of adversely reacting terpenes, the amount of acidifying agent required to produce ammonium sulfate is also reduced, which further improves the efficiency of the method. As described above, the addition of water promotes and improves the decanting of turpentine oil from the oxidizing liquid. Furthermore, the addition of water reduces the heat release during the addition of the acidifying agent, thereby ensuring that ammonium sulfate does not precipitate.

[0032] Acidification of the oxidizing liquid lowers the pH of the liquid. In one embodiment, the pH of the oxidizing liquid is adjusted to a pH in the range of 2.0–6.5, preferably 2.0–3.0, and suitably to pH 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, or 2.9. Lowering the pH to a pH in the acidification step, preferably 2.0–6.5, preferably 2.0–3.0, and suitably to pH 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, or 2.9, increases the yield of ammonium sulfate, thereby reducing the amount of free sulfate ions in the liquid.

[0033] In one embodiment, the oxidant is selected from: peroxides (typically hydrogen peroxide), oxygen, ozone, sodium hypochlorite, and mixtures thereof. In a preferred embodiment, the oxidant is in liquid form, particularly suitable as liquid hydrogen peroxide. Liquid oxidants, such as liquid hydrogen peroxide, are easier to handle than gaseous oxidants. In one embodiment, the dosage of the oxidant added ranges from 2% to 12% by weight of crude methanol, typically 3% to 11%, suitably 4% to 10%, for example 5%, 6%, 7%, 8%, or 9%.

[0034] In another embodiment, the acidifying agent is selected from: sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, acetic acid, formic acid, carbon dioxide, sulfur dioxide, waste liquid from carbon dioxide production, waste liquid from acid bleaching equipment, sodium sulfate bleaching filtrate such as A-stage bleaching filtrate and chlorine bleaching filtrate, and mixtures thereof. In one embodiment, sulfuric acid is preferred because it is widely available in pulp mills and can be produced from concentrated non-condensable gases (CNCG). The readily available sulfuric acid, or sulfuric acid that can be produced from CNCG, has the further advantage of having fewer impurities than some of the other acidifying agents (i.e., filtrates) mentioned.

[0035] In another embodiment, the method is carried out at a temperature in the range of 35°C – 60°C, preferably 40°C to 55°C, suitably at temperatures of 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, or 54°C. The boiling point of methanol, which constitutes the most valuable component of the liquid, is 64°C. Preferably, methanol remains in liquid form during the treatment of the liquid, and no methanol is lost in gaseous form.

[0036] In one implementation, the method is carried out under ambient pressure, which means that in one implementation, the pressure is not regulated, in other words, no pressure regulation step is performed.

[0037] The implementation can be carried out in one or more containers. In one implementation, the oxidation and acidification steps are carried out in the same container. Carrying both oxidation and acidification in the same container improves the economics of the method, both in terms of equipment costs and energy; for example, the heat / steam generated in the exothermic oxidation and acidification steps can be used to strip methanol in the same container. In another implementation, the oxidation and acidification steps are carried out in different containers. Carrying the oxidation and acidification steps in different containers provides greater control over the process because both steps are exothermic.

[0038] In embodiments where the oxidation and acidification steps are performed in different containers, it is necessary to transfer the oxidizing liquid from the first container to the second container. Therefore, in one embodiment, the oxidizing liquid is transferred from the first container to the second container.

[0039] In addition to the method, this technology also relates to a system for processing alkaline liquids comprising methanol and one or more components selected from: sulfur-containing organic compounds, hydrogen sulfide (H2S), ammonia, acetone, alcohols such as ethanol, extracts such as turpentine, and mixtures thereof. Specifically, this technology also relates to a system for processing alkaline liquids comprising methanol, ammonia, sulfur-containing organic compounds, hydrogen sulfide, and one or more components selected from: acetone, alcohols such as ethanol, extracts such as turpentine, and mixtures thereof.

[0040] In one embodiment, the system includes an oxidation unit 101 and an acidification unit 103. The oxidation unit 101 has a first inlet configured to receive an alkaline liquid 10 comprising methanol and one or more components selected from sulfur-containing organic compounds, hydrogen sulfide (H2S), ammonia, acetone, alcohols such as ethanol, extracts such as turpentine, and mixtures thereof; and a second inlet configured to receive an oxidant 40 for conveying the contents 310 of the oxidation unit 101 to the outlet of the acidification unit 103. The acidification unit 103 has an inlet configured to receive a feed of the oxidizing alkaline liquid 310 from the outlet of the oxidation unit 101; a second inlet configured to receive an acidifier 70; and an outlet configured to convey an acidified feed stream 80, substantially free of polymerized terpenes, to further processing.

[0041] In another embodiment, the system further includes a first decanting unit 100 configured to receive an alkaline liquid 10 comprising methanol and one or more components selected from sulfur-containing organic compounds, hydrogen sulfide (H2S), ammonia, acetone, alcohols such as ethanol, extracts such as turpentine, and mixtures thereof, and having an inlet for water 20 for decanting turpentine 30 from the alkaline liquid 10 before the liquid is fed from the outlet of the decanting unit 100 to the first inlet of the oxidation unit 101.

[0042] In one embodiment, the system further includes a second decanting unit 102 configured to receive an oxidizing alkaline liquid from an oxidation unit 101 and having an inlet for water 50 for decanting further turpentine 60 from the oxidizing alkaline liquid before sending it from the outlet of the decanting unit to an acidification unit 103.

[0043] In one embodiment, the oxidation unit 101 includes a second outlet configured to remove oxidation product 90 from the oxidation unit 101. Typically, the oxidation product 90 is removed from the oxidation unit 101 before proceeding to further steps.

[0044] In one embodiment, the acidification unit 103 includes a second outlet configured to remove ammonium sulfate 120 from the acidification unit. Typically, ammonium sulfate is removed from the acidification liquid 80 before the acidified feed stream is sent to further processing.

[0045] A system for oxidation and acidification in a single container is described according to further embodiments of the present invention. Thus, in one embodiment, the system for processing an alkaline liquid 10 includes a decanter 100 and an oxidation and acidification unit 104, the alkaline liquid 10 comprising methanol and one or more components selected from: sulfur-containing organic compounds, hydrogen sulfide (H2S), ammonia, acetone, alcohols such as ethanol, extracts such as turpentine oil, and mixtures thereof. The decanter 100 has a first inlet configured to receive the liquid 10, a second inlet for water 20, a first outlet for decanting turpentine oil 30, and a second outlet configured to deliver the decanted liquid to the oxidation and acidification unit 104. The oxidation and acidification unit 104 has a first inlet for receiving the decanted liquid 300 feed from the decanter 100, a second inlet for receiving an oxidant 40, a third inlet for receiving an acidifier 70, and an outlet for delivering the acidified stream 80 to further processing.

[0046] In one embodiment, the oxidation and acidification unit 104 is configured to receive the oxidant 40 via the second inlet before receiving the acidifying agent 70 through the third inlet. In another embodiment, the oxidation and acidification unit 104 is configured such that the third inlet is closed when the second inlet is open to receive the oxidant. In yet another embodiment, the oxidation and acidification unit is configured such that the second inlet is closed when the third inlet is open to receive the acidifying agent 70.

[0047] The following examples illustrate at least some implementations of this technology.

[0048] Example

[0049] Example 1

[0050] The acidification process of crude methanol was simulated in laboratory experiments. Water was added to crude methanol at a ratio of 1.3 (1.3 parts water: 1 part crude methanol, by weight), and the resulting turpentine oil layer was decanted from the top of the aqueous phase. The pH was adjusted to approximately 2 using sulfuric acid. The acidified methanol solution was evaporated until a temperature of 95°C was reached. The liquid remaining in the evaporation flask was filtered. A sticky solid remained on the wall of the evaporation flask, and a solid residue filter cake remained on the filter funnel. The solid residue was collected from the evaporation flask and the filter funnel. Increasing the crude methanol / water ratio further increased solid formation, and it was confirmed that solids would form even when acidified to pH 6.

[0051] Experiments show that no mechanical means or process adjustments can eliminate the tendency for solid formation during acidification. Solid formation was observed even at room temperature without heating, and filtration and secondary decantation after acidification did not significantly reduce solid formation.

[0052] Example 2

[0053] Laboratory tests confirmed that oxidation prior to acidification eliminated solid formation. The aforementioned steps were repeated, but with an additional oxidation step after decantation and before acidification. Oxidation was carried out at 50°C for 1 hour, with an H₂O₂ dosage of 3.9 w / w% based on crude methanol weight. H₂SO₄ consumption was reduced due to oxidation. No particle formation was observed after evaporation. Table 1 shows a comparison of experiments with and without oxidation.

[0054]

[0055] Table 1. Comparison of acidification with and without oxidation.

[0056] Industrial applicability

[0057] This method has various industrial applications, such as in pulp mills, where it can be applied to sludge condensate, crude methanol, or SOG to oxidize sulfur-containing compounds, turpentine, and ammonia, forming ammonium sulfate from unreacted ammonia. The oxidized compounds and ammonium sulfate are readily removed from the treated liquid for further processing, thereby providing a methanol stream containing other alcohols and acetone.

Claims

1. A method for treating an alkaline liquid (10), said alkaline liquid (10) comprising methanol, ammonia, a sulfur-containing organic compound, hydrogen sulfide, and one or more components selected from: acetone, alcohols such as ethanol, extracts such as turpentine oil, and mixtures thereof, said method comprising the following steps performed in chronological order: The liquid is brought into contact with the oxidant (40), thereby oxidizing at least a portion of the sulfur compounds in the liquid to their oxidized form, thus providing an oxidizing liquid (310); and The oxidizing liquid (310) is brought into contact with an acidifying agent (70), whereby the ammonia present in the oxidizing liquid reacts to form ammonium sulfate and provides an acidified liquid (80) that is substantially free of polymeric terpenes.

2. The method according to claim 1, the method comprising the further step of sending the acidified liquid (80) to further processing.

3. The method according to claim 1 or 2, the method comprising the further step of diluting the liquid (10) with water before contacting the liquid (10) with the oxidant (40).

4. The method according to claims 1 to 3, the method comprising the further step of decanting turpentine oil (30) from the liquid before contacting the liquid (10) with the oxidant (40).

5. The method according to any one of the preceding claims, the method comprising the further steps of adding water (50) to the oxidizing liquid (310) before contacting the oxidizing liquid (70) with the acidifying agent (70) and optionally decanting turpentine oil (60) from the oxidizing liquid.

6. The method according to any one of the preceding claims, the method comprising adjusting the pH of the oxidizing liquid (310) to a pH in the range of 2.0–6.5, preferably 2.0–3.0, and suitably to a pH of 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8 or 2.

9.

7. The method according to any one of the preceding claims, wherein the oxidant (40) is selected from: hydrogen peroxide, peroxide, oxygen, ozone, sodium hypochlorite and mixtures thereof.

8. The method according to any one of the preceding claims, wherein the acidifying agent (70) is selected from: sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, acetic acid, formic acid, carbon dioxide, sulfur dioxide, waste liquid from carbon dioxide production, waste liquid from acidic bleaching equipment, sodium sulfate bleaching filtrate such as A-stage bleaching filtrate and chlorine bleaching filtrate, and mixtures thereof.

9. The method according to any one of the preceding claims, wherein the method is carried out at a temperature in the range of 35°C – 60°C, preferably 40°C to 55°C, suitably at a temperature of 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53 or 54°C.

10. The method according to any one of the preceding claims, wherein the method is performed under environmental pressure.

11. The method according to any one of the preceding claims, wherein the oxidation step and the acidification step are carried out in the same container (104).

12. The method according to any one of claims 1 to 9, wherein the oxidation step and the acidification step are carried out in different containers (101, 103).

13. The method of claim 11, the method comprising the step of transferring the oxidizing liquid from a first container to a second container.

14. A system for processing an alkaline liquid, said alkaline liquid comprising methanol, ammonia, a sulfur-containing organic compound, hydrogen sulfide, and one or more components selected from: acetone, alcohols such as ethanol, extracts such as turpentine oil, and mixtures thereof, characterized in that... The system includes: Oxidation unit (101) and acidification unit (103), wherein The oxidation unit (101) has The first inlet is configured to receive an alkaline liquid (10) comprising methanol, sulfur-containing organic compounds, hydrogen sulfide, ammonia, and turpentine. The second inlet is configured to receive the oxidant (40). Used to deliver the contents (310) of the oxidation unit (101) to the outlet of the acidification unit (103), The acidification unit (103) has The inlet is configured to receive an oxidizing alkaline liquid (310) feed from the outlet of the oxidation unit (101). The second inlet is configured to receive the acidifying agent (70), and It is configured to deliver an acidified stream (80) that is substantially free of polymerized terpenes to an outlet for further processing.

15. The system of claim 14, further comprising a first decanting unit (100) configured to receive an alkaline liquid and having an inlet for water (20) for decanting turpentine oil (30) from the alkaline liquid before the liquid is fed from the outlet of the decanting unit (100) to the first inlet of the oxidation unit (101).

16. The system according to claim 14 or 15, further comprising a second decanting unit (102) configured to receive an oxidizing alkaline liquid from the oxidation unit (101) and having an inlet for water (50) for decanting further turpentine oil (60) from the oxidizing alkaline liquid before sending the oxidizing alkaline liquid from the outlet of the decanting unit to the acidification unit (103).

17. The system according to any one of claims 14 to 16, characterized in that... The oxidation unit (101) includes a second outlet configured to remove oxidation products (90) from the oxidation unit (101).

18. The system according to any one of claims 14 to 17, characterized in that... The acidification unit (103) includes a second outlet configured to remove ammonium sulfate (120) from the acidification unit.

19. A system for processing an alkaline liquid, said alkaline liquid comprising methanol and one or more components selected from: sulfur-containing organic compounds, hydrogen sulfide (H2S), ammonia, acetone, alcohols such as ethanol, extracts such as turpentine oil, and mixtures thereof, characterized in that... The system include: The decanter (100) and the oxidation and acidification unit (104), wherein The decanter (100) has The first inlet is configured to receive the liquid. The second inlet for water (20), The first outlet for decanting turpentine (30), and It is configured to deliver the decanted liquid to the second outlet of the oxidation and acidification unit (104). The oxidation and acidification unit (104) has The first inlet is used to receive the decanted liquid feed from the decanter (100). A second inlet for receiving oxidants. A third inlet for receiving the acidifying agent, and an outlet for delivering the acidified material stream to further processing.

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