Process and apparatus for producing methanol

Abstract

A process for oxidizing lignin present in a filtrate to methanol by supplying an oxidizing agent to the lignin-containing feedstock in a reactor, and a system configured to carry out the process, are provided.

Description

[Technical field]

[0001] The present disclosure relates generally to the production of methanol. The present disclosure relates particularly, but not exclusively, to a process and apparatus for producing methanol from fiber line filtrate containing lignin. [Background technology]

[0002] This section provides useful background information without acknowledgement that any of the technology described herein represents the state of the art.

[0003] Pulp mill fiber line filtrate contains varying amounts of lignin. Previously, lignin has been used in pulp mills to generate heat and steam. However, there is a need to develop processes that use lignin to produce products with higher value. Summary of the Invention

[0004] The appended claims define the scope of protection. Any examples and / or technical descriptions of the devices, systems, products and / or processes in the description and / or drawings that are not covered by the claims are presented herein as background or examples useful for understanding the present invention, and not as embodiments of the present invention.

[0005] It is an object of the present disclosure to provide a process for producing methanol from lignin present in waste streams and / or side streams originating from industrial processes, such as from fiber line filtrate streams. Another object is to provide an alternative solution to existing technologies in methanol production and / or lignin processing.

[0006] According to a first aspect, there is provided a process for producing methanol, comprising: providing a feedstock comprising lignin in an aqueous medium in a reactor; and A process is provided that includes providing at least one oxidizing agent to a feedstock to produce a reaction mixture in which methoxyl groups of lignin are oxidized to methanol.

[0007] When an oxidizing agent is provided to the feedstock, a reaction mixture is formed in which the at least one oxidizing agent converts methoxyl groups present in the lignin to methanol in an oxidation reaction, in one embodiment, both phenolic and non-phenolic lignin are oxidized by the process.

[0008] In one embodiment, the reactor is fluidly connected to a fiber line filtrate pipeline of the pulp mill, such that the reactor, as well as other portions of the system disclosed herein, can be installed as an integrated unit of the pulp mill, and the fiber line filtrate can be directed to the reactor.

[0009] In one embodiment, the oxidizing agent includes or is selected from oxygen, ozone, air, or any combination thereof.

[0010] In one embodiment, the oxidant is supplied to the reactor and / or feedstock through a nozzle or inlet port.

[0011] In one embodiment, the pH of the reaction mixture is adjusted to a value selected from the range of 5 to 14, preferably the range of 7 to 13, more preferably the range of 10 to 12, or to a pH of about 11.

[0012] In one embodiment, the reactor is operated at a temperature in the range of 50-100°C, preferably in the range of 80-95°C, more preferably in the range of 85-95°C, and most preferably at about 90°C.

[0013] In one embodiment, the reactor is operated at a pressure selected from the range of 0.5 to 10 bar(g), preferably from 1 to 7 bar(g), most preferably from 2 to 5 bar(g), or the pressure is about 4 bar(g).

[0014] In one embodiment, the feedstock is or includes filtrate from a fiber line of a pulp mill.

[0015] In one embodiment, the feedstock comprises any filtrate containing lignin, hi another embodiment, the feedstock comprises a filtrate selected from brown stock wash filtrate, oxygen delignification filtrate, clarified oxygen delignification filtrate, Ep stage filtrate, D0 stage filtrate, Z stage filtrate, or any combination thereof.

[0016] In one embodiment, the oxidized feedstock produced in the reactor is returned to the fiber line of the pulp mill after the oxidation process is completed. The oxidized filtrate can then be processed in the same way that the filtrate is processed in the pulp mill.

[0017] In one embodiment, the oxidized feedstock is transferred to a stripping column, and the stripping gas produced in the stripping column is directed to a condensation unit where methanol is recovered. The recovered methanol can be optionally purified.

[0018] In one embodiment, the reactor is operated under conditions where the methanol is at least partially in vapor form and the reactor is directly fluidly connected to a liquefaction unit or a stripper off-gas (SOG) line. In one embodiment, the SOG line collects vapors from the stripper from the shell side of any stripping system. The SOG is primarily methanol and TRS components. The SOG can then be condensed to produce liquid methanol. The SOG is derived from different stripper units. These methanol collection units can therefore be used to at least partially recover the methanol produced by the process as well as methanol that may be present in the feedstock led to the reactor.

[0019] According to a second aspect, there is provided a system comprising means for carrying out the process of the first aspect or any of its embodiments.

[0020] Several illustrative embodiments will now be described with reference to the accompanying drawings. [Brief description of the drawings]

[0021] [Figure 1] Certain parts of a system configured to carry out the process are shown generally as an exemplary embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] In this specification, like reference numbers refer to like elements or steps.

[0023] In this disclosure, Adt refers to air dry tonnes.

[0024] In this disclosure, COD refers to chemical oxygen demand expressed as mg / l. COD can be determined according to ISO 6060:1989 Water quality - Determination of chemical oxygen demand.

[0025] As used herein, the term "comprising" includes the broader meanings of "including," "containing," and "comprehending," as well as the narrower terms "consisting of" and "consisting only of."

[0026] In one embodiment, the process steps are carried out in the order specified in any aspect, embodiment or claim. In another embodiment, any process step specified to be performed on a product or intermediate obtained in a previous process step is performed directly on said product or intermediate, i.e. without additional, optional or auxiliary processing steps that may chemically and / or physically change the product or intermediate between said two successive steps.

[0027] In one embodiment, the process is an industrial process. In another embodiment, an industrial process may exclude small scale processes, such as laboratory scale processes that are not scaled up to amounts used in industry.

[0028] In one embodiment, the process is carried out without the addition of a catalyst to the reactor.

[0029] In one embodiment, the lignin present in the aqueous medium is at least partially dissolved or solubilized in the aqueous medium.

[0030] Lignin contains methoxyl groups that can be converted to methanol by this process.

[0031] Lignin is either non-phenolic or phenolic, with approximately 40% of lignin being phenolic and 60% being non-phenolic. Phenolic lignin is reactive to mild oxidizing conditions, while non-phenolic lignin requires more oxidizing conditions and stronger environments to produce methanol. Using the operating conditions and oxidizing agents disclosed herein, the phenolic and non-phenolic lignin methoxyl groups available in the lignin structure can be converted to methanol.

[0032] In the process, an oxidation reaction can be carried out in at least one oxidation reactor to convert phenolic or non-phenolic methoxyl groups of lignin to methanol, in another embodiment, multiple, e.g., two, three or four, reactors in series are used.

[0033] In another embodiment, the pressure and temperature in the reactor are selected so that the methanol remains in the liquid phase. The methanol may be dissolved in the feedstock.

[0034] In one embodiment, the pH of the reaction mixture is adjusted to a value selected from the range of 5 to 14, preferably the range of 7 to 13, more preferably the range of 10 to 12, or to about 11. The adjustment can be made with any alkali or acid. In one embodiment, the pH adjustment is made with an alkali selected from sodium hydroxide, white liquor and oxidized white liquor. The pH adjustment can be made initially at the start of the oxidation process and / or during the oxidation reaction to maintain the pH at or near the selected pH value.

[0035] In one embodiment, the reactor is operated at a temperature in the range of 50-100°C, preferably in the range of 80-95°C, more preferably in the range of 85-95°C, and most preferably at about 90°C.

[0036] In one embodiment, the reactor is operated such that the oxidation reaction occurs for up to 500 minutes, e.g., from 10 to 500 minutes, from 50 to 500 minutes, from 100 to 500 minutes, from 200 to 500 minutes. In one embodiment, when multiple reactors are used, the time refers to the total time that the oxidation reaction conditions are maintained.

[0037] In another embodiment, the reactor is operated such that the oxidation reaction is carried out for up to 250 minutes, e.g., 50-200 minutes, 110-210 minutes, 100-200 minutes, or 90-190 minutes. In another embodiment, the reaction is carried out for about 80 minutes, 100 minutes, 120 minutes, 180 minutes, or 200 minutes. In one embodiment, when multiple reactors are used, the time refers to the total time that the oxidation reaction conditions are maintained.

[0038] In one embodiment, the non-condensable gas is removed by a non-condensable gas handling system.

[0039] In an exemplary embodiment, the filtrate comprises filtrate from a hardwood pulp mill. In one embodiment, the filtrate has at least one component present in the amount shown in Table 1 of the analytical results, or within a 15% error range of any amount shown in Table 1.

[0040] [Table 1]

[0041] In one embodiment, the reactor is operated using oxygen as the oxidant for up to 200 minutes at conditions including a temperature of 90° C., a pH in the range of 8-14, and a pressure of 8 bar. In a preferred embodiment, the pH is about 11.

[0042] In one embodiment, the reactor is operated using air as the oxidant for up to 200 minutes at conditions including a temperature of 90° C. and a pH in the range of 8 to 14. In a preferred embodiment, the pH is about 11.

[0043] In one embodiment, the reactor is operated using ozone as the oxidant for up to 30 minutes at conditions including a temperature of 90° C. and a pH in the range of 8 to 14. In a preferred embodiment, the pH is about 11.

[0044] The process can produce about 2.5-5 kg ​​of methanol per Adt when oxygen delignification filtrate is used as the feedstock. In the case of brown stock wash filtrate, methanol production can be up to 8 kg / Adt due to the high concentration of lignin in the filtrate. Using ozone as the oxidant further increases the methanol yield, which can be as high as 5 kg / Adt. In a preferred embodiment using brown stock filtrate, an additional 8 kg / Adt of methanol can be produced. Ozone also allows for the use of shorter reaction times, as it is more reactive than air or oxygen.

[0045] In one embodiment, the oxidant is a gas.

[0046] In some amounts, the amount of oxidizing agent used in the oxidation reaction is 12% or less by weight of the dry solids, hi other embodiments, the oxidizing agent is used in an amount of 1-12, 1-10, 3-12, 3-10, 5-12, 5-10, 7-12, or 7-10% by weight of the dry solids.

[0047] In one embodiment, the oxidant is supplied to the reactor and / or feedstock through a nozzle or inlet port, which may be located inside the reactor or on the wall, bottom, and / or top of the reactor.

[0048] In one embodiment, the reactor is a stirred tank reactor. In another embodiment, the reactor is a continuous stirred tank reactor, a plug flow reactor, or a batch reactor.

[0049] In one embodiment, the reactor pressure is selected from the range of 0.5 to 10 bar(g), preferably from 1 to 7 bar(g), most preferably from 2 to 5 bar, or the pressure is about 4 bar.

[0050] In one embodiment, the oxidized feedstock, e.g., the oxidized filtrate, is returned to the fiber line of the pulp mill after oxidative treatment by the process. The fiber line may be followed by an evaporation plant equipped with a stripping column. The stripped gas may be conveyed to a liquefaction unit and further purification of the liquefied compounds. Since the oxidized feedstock fed to the fiber line contains an increased amount of methanol, the process enhances the production of methanol from a lignin-containing stream obtained from a pulp mill.

[0051] In one embodiment, the oxidized feedstock is transferred to a stripping column, and the stripping gas produced in the stripping column is directed to a condensation unit where methanol is condensed for recovery and, optionally, subsequent methanol purification, which can be performed, for example, by distillation.

[0052] Another advantage of the present process is that existing methanol recovery means used in pulp mills, such as methanol evaporation, condensation and purification units, can be utilized to recover the methanol produced in the present process.

[0053] Alternatively or additionally, the methanol produced in the process is recovered near the oxidation reactor. In this embodiment, the reactor is operated such that at least a portion of the methanol is in vapor form and thus can be recovered in a liquefaction unit in direct fluid connection with the reactor. In one embodiment, the oxidation reaction and removal of methanol occur simultaneously. When the liquefaction unit is in direct fluid connection with the reactor, at least a portion of the methanol present in and formed in the oxidized feedstock is recovered before the oxidized feedstock is returned to the fiber line.

[0054] In a further alternative or additional embodiment, the methanol is recovered from a stripper off-gas that is in fluid communication with the reactor. In one embodiment, the off-gas stripper is in direct fluid communication with the reactor.

[0055] Alternatively or additionally, gas from the reactor is directed to a stripper off-gas that is fluidly connected to at least one additional source of gas produced in the pulp mill. In this configuration, the methanol-containing gas produced in the reactor can be processed in equipment present in the pulp mill.

[0056] The oxidation of lignin in this process partially decomposes the lignin and reduces the COD, which can be used as an indicator of the methanol produced from the lignin present in the feedstock.

[0057] The oxidized filtrate can be returned to the fiber line for mixing with the fiber line filtrate and for use in the pulp mill washing process. The oxidized filtrate can be returned to the fiber line without further treatment or purification.

[0058] Due to the low sulfur content of the fiber line filtrate, the oxidation process can be carried out with a minimum number of reactors in series, for example one or two reactors in series. Due to the low amount of sulfur compounds in the fiber line filtrate, the oxidizing agent is not significantly consumed by the oxidation of the sulfur compounds. Any reaction products resulting from the sulfur oxidation remain in the oxidized filtrate.

[0059] Since methanol boils at a low temperature, most of the methanol can be extracted by using simple stripping and / or distillation to separate the volatile components / vapors from the liquid oxidation filtrate.

[0060] In one embodiment, the process is a continuous process, such as a process carried out in a continuous stirred tank reactor or a plug flow reactor.

[0061] In one embodiment, the process is a batch process.

[0062] An exemplary embodiment disclosing certain portions of a system configured to carry out the process is shown in FIG. 1, where a reactor 200 can be connected to a pulp mill fiber line 100 via reactor inlet line 110 and configured to feed fiber line filtrate to the reactor 200. A reactor outlet line 290 is connected to the fiber line 100 at a location downstream of where the reactor inlet line 110 connects to the fiber line 100. Connected to the reactor 200 is an oxidant feed inlet line 211, which can be configured to feed an oxidant to the reactor in the direction indicated by arrow 210. Alkali can be fed to the reactor via alkali feed inlet line 221 in the direction indicated by arrow 220. If an acid or other chemical is fed to the reactor to adjust the pH, said agent can be fed to the reactor through inlet 221 or other reactor inlets not shown in FIG. 1.

[0063] Methanol produced in the oxidation process will be dissolved in the oxidized filtrate in the reactor if the reactor is operated under conditions that do not allow the methanol to significantly evaporate. In such cases, methanol can be recovered from the oxidized feedstock and fed to the fiber line 100 by using equipment present in the pulp mill and used to remove methanol from fiber line filtrate or other methanol-containing feedstocks.

[0064] In an alternative or additional embodiment, Figure 1 shows a liquefaction unit 235 and SOG line 245 that can be used to directly extract methanol from the gas formed inside the reactor 200. In this configuration, the vapor is connected to a stripper off-gas line where other vapors are also collected to the pulp mill, and the off-gas is then liquefied to produce liquid methanol, which can then be further processed.

[0065] 1, these units are connected directly to the reactor 200. The reactor gas outlet 230 is fluidly connected to a liquefaction unit 235 and directs gases and vapors, including methanol vapor, from within the reactor to the liquefaction unit 235. Methanol condensed from the vapor is directed from the liquefaction unit 235 through a liquefaction unit outlet 239 to a methanol storage tank 310. The methanol storage tank 310 or the liquefaction unit 235 can also be configured to receive methanol from other methanol recovery units in the pulp mill, such as a unit that recovers methanol from the fiber line filtrate 100.

[0066] 1 illustrates a stripper off-gas line 245 to which reactor gas outlet 240 is fluidly connected to direct gases and vapors, including methanol vapor, from within reactor 200 to SOG line 245. Methanol condensed from the vapor is directed from SOG line 245 through outlet 249 to methanol storage tank 410. Methanol storage tank 410 can be configured to receive methanol from other methanol recovery units in the pulp mill, such as a unit that recovers methanol from fiber line filtrate 100.

[0067] The SOG line preferably collects all the stripper off-gas together and the methanol produced by the process can be combined into an existing line / collection as shown by inlet line 241.

[0068] The inlet and outlet lines, configured to transport materials and shown in Figure 1, can be equipped with one or more valves and one or more pumps to allow better control of the process and ensure efficient transport of the gas and liquid phases in different parts of the system. Sampling points can be placed in the pipes or vessels of the system to allow analysis of materials and process parameters in the process.

[0069] Heating and / or cooling means may be disposed within the reactor to control the operating temperature of the reactor.

[0070] example The hardwood brown stock wash filtrate was treated in a 2 liter reactor (1 liter of filtrate was used). The filtrate was oxidized with oxygen at 2 bar and 90°C for 3 hours. The reaction was run as a batch process and no further oxygen was fed to the reactor. The filtrate and oxygen were allowed to react for 3 hours, with samples taken every 30 minutes. No catalyst was used as the pH was high initially and did not decrease significantly.

[0071] The methanol concentration increased from 500 mg / l to 800 mg / l, which means an additional production of 3.8 kg / Adt of methanol. The pH decreased from 13.1 to 12.9.

[0072] The results show that the present process was successful in producing methanol from lignin-containing feedstocks under mild process conditions.

[0073] The above description has provided a complete and informative description of the best mode currently contemplated by the inventors for carrying out the present invention as non-limiting examples of specific implementations and embodiments. However, it will be apparent to those skilled in the art that the present invention is not limited to the details of the embodiments presented above, and that it can be implemented in other embodiments using equivalent means, or in different combinations of embodiments, without departing from the characteristics of the present invention.

[0074] Moreover, some of the features of the exemplary embodiments disclosed above can be used to advantage without the corresponding use of other features. Accordingly, the foregoing description should be considered as merely illustrative of the principles of the invention and not in limitation thereof. The scope of the invention is therefore limited only by the appended claims.

Claims

1. 1. A process for producing methanol, comprising: providing a feedstock comprising lignin in an aqueous medium in a reactor; providing at least one oxidizing agent to the feedstock to produce a reaction mixture in which methoxyl groups of the lignin are oxidized to methanol; adjusting the pH of the reaction mixture to a value selected from the range of 5 to 14; and operating the reactor at a temperature in the range of 50 to 100°C. The process includes:

2. 10. The process of claim 1, wherein the reactor is fluidly connected to a fiber line filtrate pipeline.

3. 3. The process of claim 1 or 2, wherein the oxidizing agent is selected from oxygen, ozone, air, or any combination thereof.

4. 3. The process of claim 1 or 2, wherein the oxidant is supplied to the feedstock through a nozzle or inlet port.

5. 3. The process according to claim 1 or 2, wherein the pH of the reaction mixture is adjusted to a value selected from the range of 7 to 13, preferably from the range of 10 to 12, or to a pH of about 11.

6. 3. The process of claim 1 or 2, wherein the reactor is operated at a temperature in the range of 80 to 95°C, preferably in the range of 85 to 95°C, most preferably at about 90°C.

7. 3. The process of claim 1 or 2, wherein the reactor is operated at a pressure selected from the range of 0.5 to 10 barg, preferably from 1 to 7 barg, most preferably from 2 to 5 barg, or the pressure is about 4 barg.

8. 3. The process of claim 1 or 2, wherein the feedstock is filtrate from a fiber line of a pulp mill.

9. 3. The process of claim 1 or 2, wherein the feedstock comprises a filtrate selected from brown stock wash filtrate, oxygen delignification filtrate, clarified oxygen delignification filtrate, or any combination thereof.

10. 3. The process of claim 1 or 2, wherein the oxidized feedstock is returned to the fiber line of the pulp mill.

11. 3. The process according to claim 1 or 2, wherein the oxidized feedstock is transferred to a stripping column and the stripping gas produced in the stripping column is led to a condensation unit where methanol is recovered and optionally followed by methanol purification.

12. 3. The process of claim 1 or 2, wherein the reactor is operated under conditions in which methanol is at least partially in vapor form and the reactor is in direct fluid connection to a liquefaction unit or a stripper off-gas line.

13. A system comprising means for carrying out the process of claim 1 or 2.

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