Method and apparatus for controlling enzymatic hydrolysis by FTIR spectroscopy.

Abstract

A method for controlling enzymatic hydrolysis in a bio-based chemical production process is provided, comprising performing at least one FTIR measurement on at least one process fluid and controlling the value of at least one process parameter based on the results obtained, the results being indicative of the content of one or more carbohydrates in the respective process fluid, the control of the value of the process parameter being performed to affect at least one of the conversion of cellulose and hemicellulose to monomeric carbohydrates in the enzymatic hydrolysis and the relative content of soluble lignin to monomeric carbohydrates in the enzymatic hydrolysis.

Description

[Technical Field]

[0001] This disclosure relates generally to the control of industrial-scale manufacturing processes for bio-based chemicals. In particular, this disclosure relates to the application of specific measurement methods in various parts of the process and the control decisions that can be made based on such measurements. [Background technology]

[0002] The production of biomass-based chemicals can use, for example, wood particles as a primary feedstock. In biomass-to-sugar processes, wood particles or other biomass may undergo various types of pretreatments, such as washing and impregnation with water, acid catalysts, and / or other liquids, and exposure to high temperatures and pressures, to prepare the material for subsequent steps in the process. These subsequent steps may include, for example, enzymatic hydrolysis, from which sugars (carbohydrates) can be fed to further processes. These other processes may include, for example, the production of glycols. The enzymatic hydrolysis step may also produce lignin as one of its outputs.

[0003] In known forms, the control of enzymatic hydrolysis processes involves many uncertainties. The process can be designed for specific nominal enzyme dosages and activities, but how accurately they achieve the target level of glucose content within a given time may depend, for example, on the success of preceding pretreatment steps in preparing the material flow. It would be advantageous to be able to react in real time (or at least as quickly as possible) when deviations from the expected progress of the process are detected. However, it is difficult to accurately determine the current status of each step of the process in real time. Any measurement methods applied must be suitable for long-term operation under the harsh conditions of an industrial environment, which usually makes it difficult or impossible to utilize equipment built for use in laboratory conditions. Summary of the Invention [Means for solving the problem]

[0004] According to a first aspect, there is provided a method for controlling enzymatic hydrolysis in a bio-based chemical production process, the method comprising: performing at least one Fourier transform infrared (FTIR) measurement on at least one process fluid of the production process; and controlling the value of at least one process parameter based on results obtained from the at least one FTIR measurement, the results being indicative of the content of one or more carbohydrates in each process fluid. The control of the value of the process parameter is performed to affect at least one of the conversion of cellulose and hemicellulose to monomeric carbohydrates in the enzymatic hydrolysis and the relative content of soluble lignin to monomeric carbohydrates in the enzymatic hydrolysis.

[0005] In the present context, cellulose is understood to mean at least one or all of fiber, fiber particle, cellulose, glucan, and oligomeric glucose. In the present context, hemicellulose is understood to mean at least one or all of xylan (such as glucuronoxylan and arabinoxylan), xylo-oligomers, and other hemicellulosic oligomeric sugars.

[0006] According to one embodiment, the method comprises performing FTIR measurements on the contents of the enzymatic hydrolysis reactor in which said enzymatic hydrolysis is currently taking place, which offers the advantage of being able to follow the progress of the enzymatic hydrolysis reaction essentially in real time.

[0007] According to one embodiment, the method comprises taking a sample of the contents of the enzymatic hydrolysis reactor and transporting the sample to an FTIR measurement point for performing the FTIR measurement, which has the advantage that the FTIR measurement function does not need to be directly integrated into the enzymatic hydrolysis reactor, which simplifies the structural design and facilitates the maintenance of the FTIR measurement device.

[0008] According to one embodiment, the method includes performing FTIR measurements on the contents of the process stream immediately downstream of said enzymatic hydrolysis reactor, which has the advantage of providing an accurate indication of how successful the enzymatic hydrolysis reaction has been.

[0009] According to one embodiment, the production process comprises a separation step downstream of said enzymatic hydrolysis reactor for separating solids from liquids, and the method comprises carrying out FTIR measurements on the liquid output of said separation step, which has the advantage that the FTIR results can be used not only to draw conclusions about the enzymatic hydrolysis reaction, but also to monitor how successful the collection of the monomeric carbohydrates produced is.

[0010] According to one embodiment, the method includes controllably transporting samples taken from a plurality of sampling locations along the manufacturing process to a common FTIR measurement location in a time-multiplexed manner, and sequentially performing FTIR measurements on the plurality of samples at the FTIR measurement location, thereby providing the advantage that a single FTIR measurement device can be used to perform FTIR measurements to monitor multiple steps in the process.

[0011] According to one embodiment, controlling the value of a process parameter comprises controlling the dosage of at least one enzyme in said enzymatic hydrolysis, which has the advantage of optimizing the utilization of relatively expensive process chemicals.

[0012] According to one embodiment, controlling the value of the process parameter comprises controlling the residence time of the treated product in said enzymatic hydrolysis reactor, which has the advantage that the operation of the process can be controlled by relatively simple means.

[0013] According to one embodiment, the enzymatic hydrolysis is carried out on successive product batches in the process, whereby controlling the values ​​of the process parameters may also comprise controlling the efficiency of intermediate washings in preparation for subsequent product batches in said production process, with the advantage that adverse effects of contamination can be mitigated in time by taking measures that are appropriately sized according to the individual circumstances.

[0014] According to one embodiment, the results of the FTIR measurement are obtained by calculating a weighted linear combination of each of the FTIR measured absorbance values ​​at selected wavenumbers for a plurality of instants in time and using the calculated weighted linear combination as an indication of the measured concentration of monomeric carbohydrate at each such instant in time, which has the advantage of taking into account many aspects that affect the FTIR measurement.

[0015] According to one embodiment, the selected wavenumbers include at least one compensation wavenumber selected for temperature compensation, wherein the absorbance at the compensation wavenumber is less sensitive to the concentration of the monomeric carbohydrate than the absorbance at other wavenumbers of the selected wavenumbers, which has the advantage that temperature does not need to be measured with an additional instrument, thereby reducing temperature-induced inaccuracies in the measurement.

[0016] According to a second aspect, there is provided an apparatus for controlling enzymatic hydrolysis in a process for producing bio-based chemicals. The apparatus includes at least one reactor for performing enzymatic hydrolysis on a process stream of the production process, and additional processing equipment upstream and downstream of the reactor in the process. The apparatus includes at least one Fourier transform infrared (FTIR) measurement station configured to measure the content of one or more carbohydrates in a process stream contained in either the reactor or the additional processing equipment. The apparatus also includes a process controller connected to receive measurement results from the at least one FTIR measurement station. The process controller is configured to control the value of at least one process parameter of the production process based at least in part on the received measurement results to affect the conversion of cellulose and hemicellulose to monomeric carbohydrates during the enzymatic hydrolysis and / or the relative content of soluble lignin to monomeric carbohydrates during the enzymatic hydrolysis.

[0017] According to one embodiment, the apparatus comprises a plurality of FTIR measurement stations, each configured to measure the content of a respective carbohydrate(s) in a respective process fluid, which provides the advantage of being able to obtain real-time FTIR measurement data from different steps in the process at any given time.

[0018] According to one embodiment, the apparatus comprises a common FTIR measurement station, whereby the fluid handling means is configured to controllably transport samples taken from a plurality of sampling points along the manufacturing process to the common FTIR measurement point in a time-multiplexed manner, which has the advantage that a single FTIR measurement device can be used to perform FTIR measurements to monitor a plurality of steps in a process.

[0019] According to a third aspect, there is provided a use of Fourier transform infrared (FTIR) measurements performed on at least one process fluid of a process for producing a bio-based chemical product for controlling the value of a process parameter based on results obtained from the FTIR measurements, the results being indicative of the content of one or more carbohydrates in the respective process fluid, and the control of the value of the process parameter is performed to affect the conversion of cellulose and hemicellulose to monomeric carbohydrates in the enzymatic hydrolysis and / or the relative content of soluble lignin to monomeric carbohydrates in the enzymatic hydrolysis. [Brief explanation of the drawings]

[0020] The accompanying drawings, which are included to provide a further understanding of the invention and constitute a part of this specification, illustrate embodiments of the invention and together with this description serve to explain the principles of the invention. [Figure 1] FIG. 1 is a high-level block diagram of a bio-based chemical manufacturing process. [Figure 2] 1 illustrates the process steps of an exemplary enzymatic hydrolysis process. [Figure 3] Possible ways of applying FTIR measurements are shown. [Figure 4] 1 shows the possible multiplexing of samples for FTIR measurements. [Figure 5] The effect of enzyme addition or activity is shown. [Figure 6] Show the effects of pollution. [Figure 7] The effect of contamination on the subsequent hydrolysis step is shown. [Figure 8] An example of batch-to-batch yield variation is shown. [Figure 9] An example of the yield loss over a series of batches is shown. [Figure 10] An example of FTIR measurement is shown below. [Figure 11] An example of FTIR measurement is shown below. [Figure 12] An example of FTIR measurement is shown below. [Figure 13]A comparison of FTIR-based analysis and laboratory measurements is shown. DETAILED DESCRIPTION OF THE INVENTION

[0021] FIG. 1 shows a schematic diagram of a manufacturing process for producing bio-based chemicals from wood. The process can be broadly divided into a wood handling stage 101, a wood-to-sugars stage 102, and a sugars-to-chemicals stage 103. The wood may be selected from the group consisting of hardwoods, softwoods, and combinations thereof. The wood can be obtained, for example, from pine, poplar, beech, aspen, spruce, or birch. The wood can also be any combination or mixture of these. The wood is preferably hardwood due to its relatively high inherent sugar content, although the use of other types of wood is not excluded.

[0022] The wood handling stage 101 mainly involves mechanical treatments such as debarking 111 and chipping 112 .

[0023] The wood-to-sugar stage 102, also known as the wood-to-sugar process, includes a pretreatment section in which wood chips from the wood handling stage 101 are subjected to impregnation 121, semi-hydrolysis 122, and steam explosion 123 processes to disrupt the wood structure and remove C5 sugars. Impregnation is typically part of an acid-catalyzed process and may be omitted in processes relying on autohydrolysis. The main process stream continues to enzymatic hydrolysis 124, where the goal is to convert polysaccharides to C6 monomers, essentially converting glucans to glucose. Lignin and other residual solids are removed after enzymatic hydrolysis, and the resulting C6 sugars are further fed to the sugars-to-chemicals stage 103. The removed lignin may be used in further processes.

[0024] Subsequent utilization of the sugars in the sugars-to-chemicals stage 103 may include steps such as purification of the sugars (C5 and / or C6 carbohydrates) 131 and one or more sugar conversion processes 132. The sugar conversion processes 132 may include processes such as fermentation to produce alcohol or catalytic hydrotreating to produce glycols.

[0025] FIG. 2 shows in more detail an example of what may be included in the portion of the process simply designated as enzymatic hydrolysis step 124 in FIG. 1. The process stream coming from the pretreatment section has the form of a water-based slurry. The process stream contains primarily cellulose, but also small amounts of hemicellulose. One of the goals of the preceding pretreatment section was to remove hemicellulose and C5 sugars, but some always remains. The enzymatic hydrolysis step is designed to primarily convert cellulose to monomeric carbohydrates (C6 carbohydrates), but also serves to convert a small fraction of the remaining hemicellulose to its respective monomeric carbohydrates (C5 carbohydrates).

[0026] The slurry may be subjected to some degree of pH control, after which it undergoes a short pre-hydrolysis 201 in which selected enzymes are added. The subsequent first hydrolysis step 202 is preferably carried out in batches so that the conditions and progress of the hydrolysis reaction can be monitored and controlled.

[0027] The filtrate from the first solid-liquid separation step 203 has already removed some of the soluble C6 carbohydrates, while the solid fraction is sent to reslurry 204 and then to an additional (second) hydrolysis step 205.

[0028] As used herein, reslurrying refers to a process step (and corresponding processing equipment) in which the processed product is made more fluid, usually by adding water or a water-based solution. In processes such as those described herein, reslurrying is often used after solid-liquid separation to make the separated solid fraction easier to handle and to further wash the solid fraction from remaining soluble compounds in subsequent, additional solid-liquid separation steps.

[0029] The output from the second enzymatic hydrolysis step 205 is sent to a second solid-liquid separation step 206, where the liquid fraction containing C6 carbohydrates is separated from the solid fraction. The solid-liquid separation and reslurrying may be performed in succession, and the number of such sequences can vary. Separated lignin emerges from the final separation step.

[0030] Critical to the efficient production of C6 carbohydrates is the successful conversion of glucan during prehydrolysis 201 and hydrolysis steps 202 and 205. Factors that affect the efficiency of hydrolysis include, but are not limited to, the extent to which the preceding pretreatment and semihydrolysis steps achieved the desired results; enzyme selection and dosage; the pH and temperature of the slurry in which hydrolysis occurs; the efficiency of mixing the slurry during the reaction period; the presence and composition of chemical inhibitors such as organic acids and furans; the potential and nature of microbial contamination; and even the species and other characteristics of the original source of the raw material. While the effects of many of these factors can be predicted and addressed, at least to some extent, it would be highly advantageous to be able to monitor how the conversion is progressing in real time (or at least with as short a delay as possible). What is discussed here regarding the conversion of cellulose to C6 carbohydrates also applies to the conversion of hemicellulose to C5 carbohydrates. That is, the conversion reactions behave in a similar manner, so measures taken to optimize the conversion of cellulose to C6 carbohydrates will also have a beneficial effect on the conversion of (small amounts of) hemicellulose to C5 carbohydrates.

[0031] In order to better control the successful obtaining of desired end products from bio-based chemical manufacturing processes such as those described above, new methods for controlling enzymatic hydrolysis have been developed.

[0032] One element of the method involves performing at least one FTIR measurement on at least one process fluid in the manufacturing process. The acronym FTIR stands for Fourier Transform InfraRed and refers to a spectroscopic measurement method in which a sample is irradiated with a beam of radiation covering a broad band of infrared wavelengths. A series of high-resolution spectral data is collected to determine how much of the incident infrared radiation is absorbed by the sample material. The collected data, also known as an interferogram, is then subjected to a mathematical process characterized by a Fourier transform. The result is a spectrum that shows the relative absorption of various wavelengths of infrared radiation within the sample. Because different chemicals cause different types of absorption, the calculated spectrum serves as a kind of spectral fingerprint of the actual chemical composition of the measured sample.

[0033] In the infrared region, there are other types of spectroscopic measurements known in the chemical wood processing industry, such as NIR (for near-infrared). However, unlike NIR, which generally requires a solid sample and provides measurements that primarily indicate the solid components within the sample, FTIR can be applied to direct measurements of fluid samples, providing results that indicate the chemical composition of the liquid phase. Known FTIR measurement methods, on the other hand, have a relatively short penetration depth into fluid samples. In slurries, such as those encountered in enzymatic hydrolysis, the penetration depth approaches zero. This is because the measurable interaction between the incident radiation and the measured sample occurs at (or at least very close to) the outer surface of the outermost optical element, usually a diamond crystal, through which the radiation is transmitted toward the sample.

[0034] The method for controlling enzymatic hydrolysis described herein includes controlling the value of at least one process parameter based on results obtained from at least FTIR measurements. The measurements are performed on at least one process fluid, and the results indicate the content of one or more carbohydrates in the respective process fluid. In one embodiment, such carbohydrates can be described as sugars of interest, where the term sugar is used to mean any monosaccharide or polysaccharide whose relative amount in the measured process fluid allows for inferences about the progress or success of the enzymatic hydrolysis. For example, the carbohydrate or sugar of interest in the FTIR measurements can be any of glucan and its conversion product glucose; xylan and its conversion product xylose; mannan and its conversion product mannose; arabinoxylan and its conversion product arabinose; or lactam and its conversion product lactose. Controlling the value of the process parameter is performed to affect the conversion of cellulose and hemicellulose to monomeric carbohydrates during enzymatic hydrolysis (e.g., glucan to glucose and / or xylan to xylose) and / or the relative content of soluble lignin to monomeric carbohydrates during enzymatic hydrolysis.

[0035] If additional method steps are necessary to obtain an accurate measurement of soluble lignin, such additional method steps may include, for example, spectrophotometric absorbance measurements at a wavelength of 205 nanometers. In a detailed example of such a method, a 10 ml sample is taken from the solution after enzymatic hydrolysis. If the sample is cloudy or opaque, it is diluted with high-purity (distilled or deionized) water and filtered. The absorbance is measured at a wavelength of 205 nm using a UV spectrophotometer, using a 1 cm cuvette. If the absorbance exceeds 0.7 AU, the sample is diluted with high-purity water until the absorbance is in the range of 0.2 to 0.7 AU. A zero value is determined by placing high-purity water in a cuvette and measuring a water sample as a blank sample or reference. To verify the results, two parallel measurements of the sample are performed. This measurement method is based on the difference in absorbance between soluble lignin in aqueous solution and the blank solution (which is water). The absorbance difference is obtained by subtracting the spectrum derived from the blank solution from the spectrum of the lignin solution. The amount of soluble lignin can be calculated using the following formula: The calculation takes into account any dilution that may have occurred. The result is reported as a whole number and is in mg / L.

[0036] Calculation of the amount of soluble lignin (mg / l): x=(A / a)×D where: A=absorbance a = absorption coefficient 0.110 (l / mgcm) D = dilution factor

[0037] The absorption coefficient 110 (l / gcm) (note the units) is used as an average for samples containing different wood species.

[0038] If enzymatic hydrolysis proceeds as intended, the absolute amount of lignin in the slurry remains constant, but the relative amount of monosaccharides, such as glucose, increases as the conversion proceeds. As long as the pH of the slurry remains below approximately 5.5, only a very small amount of lignin can dissolve. Dissolving lignin in the liquid phase reduces the quality of the desired end product, sugars, and is generally avoided. Using enzymes known at the time of this writing, the desirable pH range for the slurry in enzymatic hydrolysis is approximately 4 to 5.5. A lower pH, such as pH 3, would be even more desirable, as it may help prevent microbial contamination. However, it is difficult to find enzymes that function adequately in the described process when the slurry pH is below 4.

[0039] An advantageous range of infrared wave numbers for use in FTIR measurements is 648-4000 (1 / cm). By performing calibration measurements in the laboratory, it is possible to identify "signature features" in the FTIR spectrum that indicate the relative concentration of one or more monosaccharides, such as glucose, in the measured sample. Additionally or alternatively, it is possible to calculate the relative (residual) concentration of one or more polysaccharides, such as glucans. Additionally or alternatively, it is possible to identify features in the FTIR spectrum that indicate only the relative content of (soluble) lignin relative to the monomeric carbohydrates in the measured sample. Because the relative amount of soluble lignin is small but still present, its fingerprint in the FTIR spectrum can be utilized.

[0040] Even features of the FTIR spectrum that cannot be clearly associated with a particular component in the measured process fluid may be significant. That is, there may be a "standard" or "normal" type of FTIR spectrum that is typically observed when enzymatic hydrolysis is proceeding as intended. If "mystery" features appear, such as unexpected absorption in a subrange of wavelengths, and / or if a previously unencountered trend change is observed in the FTIR spectrum or part thereof, this can usually be taken as a warning that the enzymatic hydrolysis is not currently proceeding as expected and that, for example, the amount of contamination should be measured or other observations or corrective measures should be taken.

[0041] FIG. 3 shows several locations in the process where process fluids suitable for FTIR measurement may appear and, as a result, useful information may be obtained from FTIR measurements.

[0042] As a process step, enzymatic hydrolysis 301 can be carried out in batches or as a continuous process. Assuming the former, a method for controlling the enzymatic hydrolysis may include performing FTIR measurements 302 on the contents of the enzymatic hydrolysis reactor in which the enzymatic hydrolysis 301 is currently taking place.

[0043] Several alternatives exist for performing such FTIR measurements 302. It is possible to construct an enzymatic hydrolysis reactor to include a built-in measurement head for FTIR measurements. To obtain reliable results that are representative of the reactor's current contents, it is appropriate to position such a built-in measurement head so that there is sufficient turbulence in the slurry contained in the reactor at the measurement head's location. For example, such a measurement head may protrude into the reactor from the reactor's inner wall by a distance of 0 to 20 cm, preferably 1 to 5 cm. If the reactor contains a mixing device, such as a picket fence agitator, an advantageous location for the built-in measurement head may be where the agitator blade edge repeatedly sweeps adjacent to the measurement head. It is not appropriate to position the measurement head in a recess or depression, because such features in the enzymatic hydrolysis reactor tend to significantly slow down the mixing of the portion of the slurry contained in those features with the main portion of the slurry. It has been found that if the mixing of the slurry in the enzymatic hydrolysis reactor is inefficient, it can take as long as 30 minutes for changes made, for example by adding more enzyme or pH stabilizer, to have a real effect throughout the reactor.

[0044] Another alternative method of performing FTIR measurements 302 on the contents of the enzymatic hydrolysis reactor involves taking a sample of the contents of the enzymatic hydrolysis reactor and transporting the sample to an FTIR measurement station for performing the FTIR measurement. This alternative is particularly advantageous when there is a centralized FTIR measurement station to which samples taken from various parts of the process can be transported for measurement.

[0045] Performing FTIR measurements on the contents of the enzymatic hydrolysis reactor has the advantage of being able to continuously, or at least repeatedly, follow the progress of the hydrolysis reaction while the batch of slurry is in the reactor.

[0046] It should be noted that a bio-based chemical production process can include two or more pre-hydrolysis and enzymatic hydrolysis steps (see, e.g., steps 201, 202, and 205 in Figure 2), and therefore step 301 shown in Figure 3 can be any of these, most preferably either or both of enzymatic hydrolysis steps 202 or 205. In other words, performing an FTIR measurement on the contents of an enzymatic hydrolysis reactor can mean performing the measurement on the contents of any of the enzymatic hydrolysis reactors in the process, or any combination thereof.

[0047] Reference numeral 303 in Figure 3 shows how the method can include performing an FTIR measurement on the contents of the process stream immediately downstream of the enzymatic hydrolysis reactor, in addition to or as an alternative to FTIR measurement 302. Such a measurement has the advantage of providing an immediate result indicative of the success of the hydrolysis process once it is complete. As above, performing an FTIR measurement on the contents of the enzymatic hydrolysis reactor can mean performing the measurement on the contents of the process stream immediately downstream of any of the enzymatic hydrolysis reactors in the process, or any combination of these reactors.

[0048] Reference numeral 305 in Figure 3 shows how the method can include performing FTIR measurements on the liquid output of a separation step 304 downstream of the enzymatic hydrolysis reactor, in addition to or as an alternative to FTIR measurements 302 and 303. Separation step 304 has the purpose of separating solids from liquids.

[0049] If the process has the general configuration of FIG. 2, there are first and second solid-liquid separation steps 203 and 206, from which C6 carbohydrates are collected as the process output. In addition, there may be further solid-liquid separation steps, from which the liquid fraction may be recycled back to an earlier step in the process (e.g., step 201 or step 204). FTIR measurements, such as those referenced 305, have slightly different purposes depending on where in the overall process separation step 304 is located and what its purpose is. When measuring the results of either the first or second step 203 or 206 of FIG. 2, the purpose is to ensure that as much C6 carbohydrate as possible is obtained. On the other hand, when measuring the results of any subsequent separation step, the purpose is to ensure that as little C6 carbohydrate as possible is left in the liquid fraction. Otherwise, the previous step would have failed, or at least not been optimal in directing the desired C6 carbohydrates to the process output.

[0050] Any of the FTIR measurements described above may be performed using dedicated FTIR measurement devices installed at corresponding points in the process. Such a distributed measurement strategy offers the advantage that FTIR measurements can be performed continuously, or at least at freely configurable times, at any point in the process and / or that several FTIR measurements can be performed in parallel at different steps in the process. Figure 4 shows an alternative approach, in which the method comprises controllably transporting samples taken from multiple sampling points along the manufacturing process to a common FTIR measurement point 401 in a time-shared manner. FTIR measurements 402 of such multiple samples can be performed sequentially at the FTIR measurement point 401.

[0051] There is a controllable fluid connection from each sampling point to the FTIR measurement point 401, as shown schematically with conduits and valves in Figure 4. Flushing connections 403 and 404 are provided to ensure that the FTIR measurement point 401 is cleared of any remnants of the previous sample before the next sample enters. The controllable fluid connections can be operated manually and / or there may be an automatic control system that can control the sampling and measurement sequence.

[0052] The approach of Figure 4, i.e., controllably transporting the sample to a common measurement point, has the advantage that only one FTIR measurement device (or at least a few FTIR measurement devices) is required, which has the advantages of reducing the cost of acquiring and installing the measurement system and simplifying maintenance and calibration.

[0053] As outlined above, controlling a bio-based chemical production process includes controlling the value of at least one process parameter based at least in part on results obtained from at least one FTIR measurement. According to one embodiment, such control includes controlling the dosage of at least one enzyme to one or more enzymatic hydrolysis steps in the process.

[0054] Figure 5 shows an example of how the addition or activity of an enzyme (or enzyme combination) can affect the progress of a hydrolysis reaction. The horizontal axis represents the residence time of a batch of slurry in an enzymatic hydrolysis reactor, and the vertical axis represents the glucose content of the slurry. In a hydrolysis reaction, the glucose content typically begins to increase relatively quickly, but the increase slows or levels off as the reaction approaches equilibrium. Both the rate of increase in glucose content and the final level achievable can depend on the addition or activity of the enzyme (or enzyme combination). Because enzymes are relatively expensive, using too much is not advisable. On the other hand, adding too little can result in suboptimal glucose yields. If FTIR measurements are available to monitor changes in the glucose content within a batch of slurry, this can help determine whether more enzyme needs to be added or whether the exact composition of the enzyme combination needs to be adjusted for the batch currently being processed.

[0055] However, it is not necessary to perform FTIR measurements on the actual contents of the enzymatic hydrolysis reactor to make decisions about enzyme addition or activity. In other words, enzyme dosage control does not need to be based on FTIR measurements 302 shown in Figure 3. Similar decisions can be made for subsequent batches based on results obtained from previous batches using FTIR measurements such as 303 or 305 in Figure 3.

[0056] Additionally or alternatively, controlling the value of the process parameter may include controlling the residence time of the treated product in the enzymatic hydrolysis. As with controlling the addition or activity of enzymes, decisions regarding residence time may relate to the current batch if an FTIR measurement (such as measurement 302) is made within the reactor, and / or to a subsequent batch if one or more FTIR measurements (such as measurements 303 and 305) are made downstream of the reactor.

[0057] Figures 6 and 7 show examples of how microbial contamination in a slurry can affect the progression of glucose content. Figure 6 shows how FTIR measurements, which provide an indication of glucose content, can indicate contamination in an individual enzymatic hydrolysis step. Figure 7 shows how a corresponding measurement can indicate contamination in a second enzymatic hydrolysis step downstream of the first enzymatic hydrolysis step in the process. Microbial contamination typically has the effect of undesirable microorganisms beginning to consume the glucose already obtained by hydrolysis. This can mean that the glucose content increases more slowly than it should, as shown in the middle graph in Figure 6 and the middle of the branching graphs in Figure 7. If the microbial contamination is severe, the glucose content may even begin to decline, as shown in the bottom graphs in Figures 6 and 7.

[0058] If FTIR measurements provide an indication of microbial (or chemical) contamination, the resulting control of the value of the process parameter may include controlling the efficiency of intermediate cleaning in preparation for subsequent product batches in the manufacturing process. The term cleaning in place or the corresponding acronym CIP is often used to refer to such intermediate cleaning of processing equipment.

[0059] Chemical components in the slurry that may be undesirable but still occur include at least furfural, carboxylic acids, lactic acid, acetic acid, and ethanol. Additionally, there may be chemical components whose occurrence is difficult to predict but that become detectable as anomalous spectral features in one or more FTIR measurements. Controlling the values ​​of process parameters may include, for example, rejecting a batch or at least curtailing further processing if such undesirable chemical components are found to be present in excess.

[0060] 8 and 9 show examples of how the decision-making process can utilize FTIR measurements (such as FTIR measurements 303 or 305 in FIG. 3 ) that are available only after enzymatic hydrolysis of a batch is complete. While FIG. 8 shows random variation in the resulting glucose content from batch to batch, FIG. 9 shows an alarming downward trend toward increasingly lower resulting glucose contents. In the case of FIG. 8 , if there were no changes in process parameter values, the root cause of the variation could be, for example, variation in raw materials and / or the degree of success of previous steps in the bio-based chemical production process. Information about the variation can be fed back to earlier steps in the production process, where it can be correlated with known information about aspects that may vary and potentially lead to corrective action. In the case of FIG. 9 , one obvious reason behind the alarming trend is again microbial contamination, since microbial populations typically continue to grow and cause increasingly adverse consequences, at least if adequate cleaning is not performed between batches. Obtaining results like those in FIG. 9 could lead to a decision to, for example, perform more thorough cleaning of the reactor before accepting the next batch.

[0061] The method may include utilizing artificial intelligence in making decisions regarding process parameter values ​​based on the FTIR measurements. A process decision-making controller may collect data regarding previously used process parameter values ​​and corresponding FTIR measurement results and make decisions regarding trends and correlations that are difficult or impossible to recognize using human intelligence alone. Such decision-making controllers configured to utilize artificial intelligence may further develop and extrapolate from the initial basic control algorithm to make decisions regarding process parameters that optimally satisfy each available FTIR measurement result for future batches to be processed.

[0062] The above has been described primarily from the perspective of a method. From the perspective of an apparatus, an apparatus for controlling enzymatic hydrolysis in a bio-based chemical production process is provided. The apparatus includes at least one reactor for performing enzymatic hydrolysis on a process stream of the production process. The reactor may have the general appearance of a vessel or large pipe through which the process stream passes. In a batch process, successive batches of the processed product are each held in a reactor vessel for a certain reaction time, while in a continuous process, the processed product can flow slowly through a pipe-like reactor, with enzymatic hydrolysis occurring along the reactor.

[0063] The present apparatus includes additional processing equipment upstream and downstream of the reactor, where "upstream" and "downstream" are defined by the general flow direction of the processed product in the process. Such additional processing equipment can include, for example, channels, pipes, pumps, conveyors, further reactors, decanters and filtering equipment, mixing equipment, etc. The location of some of the additional processing equipment upstream and downstream of the reactor does not mean that it is immediately before or after the reactor, as other equipment may be present in between.

[0064] The apparatus comprises at least one FTIR measurement station configured to measure the content of one or more carbohydrates in a process fluid contained in either the reactor or additional processing equipment. Such an FTIR measurement station typically comprises a probe or measurement head, optics for directing infrared radiation to and from the probe, and electronic processing means capable of generating and detecting the infrared radiation and converting the raw measurement data into a format capable of constituting spectral information usable and understandable by a process controller connected to receive the measurement results from the (at least one) FTIR measurement station.

[0065] The process controller is configured to control the value of at least one process parameter of the production process based at least in part on the received measurements, with the purpose of controlling the value of such parameter being to affect the conversion of cellulose and hemicellulose to monomeric carbohydrates and / or the relative content of soluble lignin to monomeric carbohydrates during enzymatic hydrolysis.

[0066] One possibility for configuring the hardware for FTIR measurements is for the apparatus to comprise multiple FTIR measurement stations, each configured to measure the content of a respective carbohydrate(s) in a respective process fluid. Another possibility is for the apparatus to comprise a common FTIR measurement station, with fluid handling means configured to controllably transport samples taken from multiple sampling points along the production process to the common FTIR measurement point in a time-shared manner. The use of these two possibilities has been described in detail above in terms of the method.

[0067] Figures 10-13 illustrate the applicability of FTIR measurements to determine the glucose content of slurries during enzymatic hydrolysis. To generate these graphs, five measurement series, A-E, were performed. Each of these series involved subjecting a batch of pretreated process material (the result of a pretreatment process of the type described above with respect to the pretreatment portion of Figure 1) to enzymatic hydrolysis. Measurement series A, B, and C were generated from batches that underwent a single enzymatic hydrolysis step, while measurement series D-E were generated from batches that underwent two consecutive enzymatic hydrolysis steps. Of the latter, measurement series D shows the results during the first step, and measurement series E shows the results during the second step. While the measurement series are shown graphically as following each other on the time axis, this is merely a way to graphically display the results. Except for the two-step nature of measurement series D-E, the individual measurement series are independent of each other.

[0068] Each FTIR measurement provides an absorbance value for each wavenumber within the relevant wavenumber range. Plotting these absorbance values ​​on a wavenumber (or wavelength) axis provides an instantaneous FTIR spectrum. By performing repeated FTIR measurements as the hydrolysis reaction progresses, a time series of absorbance values ​​at each wavenumber can be accumulated.

[0069] Figure 10 shows the time series of absorbance values ​​at 1040 wavenumber (1 / cm) for each of measurement series A through E measured by the FTIR measurement device. The absorbance at 1040 wavenumber was found to correlate relatively well with glucose content. Figure 10 supports this finding by showing a general trend of increasing absorbance at 1040 wavenumber toward the end of each measurement series.

[0070] Figure 11 shows the time series of absorbance values ​​at wavenumber 1052 (1 / cm) for each of measurement series A through E measured by the FTIR measurement device. Similar to the absorbance at wavenumber 1040, the absorbance at wavenumber 1052 was found to correlate relatively well with glucose content. Figure 11 supports this finding by showing a general trend of increasing absorbance at wavenumber 1052 toward the end of each measurement series.

[0071] It has been found that there are several wavenumbers within the range of 648–4000 (1 / cm) that can be used for temperature compensation in FTIR measurements. For example, the absorbance at 3224 (1 / cm) measured by FTIR is relatively unaffected by changes in chemical composition that occur during enzymatic hydrolysis. Instead, it has been found that the absorbance at 3224 (1 / cm) changes as a function of the slurry temperature. Figure 12 shows the time series of absorbance values ​​at 3224 (1 / cm) for each measurement series A–E measured by the FTIR measurement device.

[0072] Similarly, temperature-dependent changes can be expected to appear at wavenumbers indicative of chemical composition, and therefore, to mitigate inaccuracies caused by temperature, the absorbance measured at 3224 (1 / cm) (and / or other wavenumbers found suitable for this purpose) can be used. The basic principle of such mitigation involves calculating a correction factor for each individual FTIR spectrum based on the absorbance values ​​at wavenumbers indicative of temperature, and adding that correction factor to the absorbance values ​​measured at wavenumbers indicative of chemical composition.

[0073] Discoveries of the type described above allow for the construction of computational models that can use the absorbance values ​​of FTIR measurements for selected wavenumbers to generate an indication of the glucose content in the slurry. An example of the general form of such a computational model is as follows:

[0074]

number

[0075] In other words, the above formula assigns a weight α to all wavenumbers used to examine the glucose content. i and assign weights β to all wavenumbers used to compensate for temperature changes. jThe first term on the right hand side of the equation represents the sum of the weighted contributions of all N wavenumbers representing glucose content. The second term on the right hand side of the equation represents temperature compensation, taking into account the weighted contributions of all M wavenumbers representing temperature.

[0076] Figure 13 shows a comparison of batches of slurry subjected to enzymatic hydrolysis. The progress was monitored by repeated FTIR measurements in the wavenumber range 648–4000 (1 / cm). The glucose content was calculated as a function of time using the above equation with parameter values ​​N = 2, M = 1, Γ = 49779, α1 = 11120653, α2 = -9320009, and β1 = 162864. The two wavenumbers contributing to the first summation were 1040 (1 / cm) (i = 1) and 1052 (1 / cm) (i = 2), and the only wavenumber contributing to the second summation was 3224 (1 / cm) (j = 1). For each instant of time t, the values ​​obtained from the equation are plotted as black dots. Simultaneously with the FTIR measurements, samples of the slurry were taken, and their glucose content was measured by the laboratory method. The gray curve represents the best mathematical fit of a smooth curve to the laboratory measurements.

[0077] Figure 13 shows that the "cloud" of black dots and the gray curve match relatively well. This proves that even a relatively crude calculation model can determine the glucose content of a slurry relatively accurately from FTIR measurements. The calculation model can be improved by increasing the values ​​of N and M. That is, find the wavenumbers where the absorbance measured by FTIR indicates either the chemical composition or the temperature, and then apply the appropriate weight α. i and β j The last mentioned method can be carried out by statistical or chemometric methods, i.e. by comparing the calculation results with laboratory measurements and selecting the weight values ​​that best match, for example in the least sum of squares sense.

[0078] The interesting parts of Figure 13 are seen near the transition between measurement series A and B (see point 1301) and at the next point 1302, approximately one-third of the way through the duration of measurement series B. In Figures 10 and 11, between the vertical dashed and dot-dash lines indicating the corresponding time points, the absorbance measured at 1040 (1 / cm) and 1052 (1 / cm) continues to increase after a short drop, as if the initial measurement series A is still continuing. However, Figure 12 shows how there is a significant, transient increase in the measured absorbance at 3224 (1 / cm) at point 1301, followed by a decrease between the vertical dashed and dot-dash lines. In other words, the process temperature changes abruptly at the transition point 1301 between measurement series A and B, and then changes continuously thereafter. As the temperature decreases, the absorbance at 1040 (1 / cm) and 1052 (1 / cm) increases, but the absorbance at 3224 (1 / cm) decreases. As can be seen in Figure 13, correcting for temperature-based inaccuracies using absorbance at 3224 (1 / cm) (and / or other wavenumbers that are good indicators of temperature independent of chemical composition) results in significant improvements when using FTIR measurements to determine glucose content during enzymatic hydrolysis.

[0079] It is obvious to those skilled in the art that with the advancement of technology, the basic idea of ​​the present invention can be realized in various ways. Therefore, the present invention and its embodiments are not limited to the above examples, but can be modified within the scope of the claims.

Claims

1. 1. A method for controlling enzymatic hydrolysis in a bio-based chemical production process, comprising: - performing at least one Fourier Transform Infrared (hereinafter FTIR) measurement on at least one process fluid of said manufacturing process; and controlling the value of at least one process parameter based on the results obtained from said at least one FTIR measurement, the results indicate the content of one or more carbohydrates in each process stream, and the control of process parameter values ​​is performed to affect at least one of the conversion of cellulose and hemicellulose to monomeric carbohydrates in the enzymatic hydrolysis and the relative content of soluble lignin to monomeric carbohydrates in the enzymatic hydrolysis; The results of the FTIR measurements are obtained by calculating a weighted linear combination of each of the FTIR measured absorbance values ​​at selected wavenumbers for a plurality of instants, and using the calculated weighted linear combination as an indicator of the measured concentration of monomeric carbohydrate at each instant.

2. - carrying out FTIR measurements on the contents of the enzymatic hydrolysis reactor in which said enzymatic hydrolysis is currently taking place; The method of claim 1 , comprising:

3. - taking a sample of the contents of the enzymatic hydrolysis reactor; and - transporting said sample to an FTIR measurement point to perform said FTIR measurement; The method of claim 2 , comprising:

4. - carrying out FTIR measurements on the contents of the process stream immediately downstream of said enzymatic hydrolysis reactor; The method of claim 2 or 3, comprising:

5. the production process comprises a separation step downstream of said enzymatic hydrolysis reactor for separating solids from liquids, the method comprises carrying out FTIR measurements on the liquid output of the separation step; The method according to any one of claims 2 to 4.

6. - controllably transporting samples taken from multiple sampling locations along the manufacturing process to a common FTIR measurement location in a time-shared manner; and - sequentially performing FTIR measurements of the samples at the FTIR measurement locations; The method according to any one of claims 1 to 5, comprising:

7. 7. The method according to any one of claims 1 to 6, wherein said controlling the value of a process parameter comprises controlling the dosage of at least one enzyme to said enzymatic hydrolysis.

8. 6. The method of any one of claims 2 to 5, wherein said controlling the value of a process parameter comprises controlling the residence time of the treated product in the enzymatic hydrolysis reactor.

9. - the enzymatic hydrolysis is carried out on successive product batches in the process, - said controlling the value of a process parameter comprises controlling the efficiency of intermediate washes in preparation for a subsequent product batch in said manufacturing process; The method according to any one of claims 1 to 8.

10. 10. The method of any one of claims 1 to 9, wherein the selected wavenumbers include at least one compensation wavenumber selected for temperature compensation, and the absorbance at the compensation wavenumber is less sensitive to the concentration of the monomeric carbohydrate than the absorbance at other wavenumbers of the selected wavenumbers.

11. 1. An apparatus for controlling enzymatic hydrolysis in a bio-based chemical production process, comprising: at least one reactor for carrying out enzymatic hydrolysis of a process stream of said production process; - additional processing equipment upstream and downstream of said reactor in the process; at least one Fourier Transform Infrared (hereinafter FTIR) measurement station configured to measure the content of one or more carbohydrates in a process fluid contained in either said reactor or said additional processing device; a process controller connected to receive measurement results from said at least one FTIR measurement station; Including, the process controller is configured to control, at least in part based on the received measurements, a value of at least one process parameter of the manufacturing process to affect at least one of the conversion of cellulose and hemicellulose to monomeric carbohydrates in the enzymatic hydrolysis and the relative content of soluble lignin to monomeric carbohydrates in the enzymatic hydrolysis; The apparatus obtains the FTIR measurement results by calculating a weighted linear combination of each of the FTIR measurement absorbance values ​​at selected wavenumbers for a plurality of instants in time, and using the calculated weighted linear combination as an indicator of the measured concentration of monomeric carbohydrate at each instant in time.

12. 12. The apparatus of claim 11, comprising a plurality of FTIR measurement stations, each FTIR measurement station configured to measure the content of a respective carbohydrate in a respective process fluid.

13. 12. The apparatus of claim 11, comprising a common FTIR measurement station, wherein fluid handling means is configured to controllably transport samples taken from a plurality of sampling locations along the manufacturing process to the common FTIR measurement location in a time-shared manner.

14. 1. Use of Fourier transform infrared (hereinafter referred to as FTIR) measurements performed on at least one process fluid in a process for producing a bio-based chemical product in order to control the value of a process parameter based on the results obtained from the FTIR measurements, the results indicate the content of one or more carbohydrates in each process stream, and the control of the values ​​of the process parameters is performed to affect at least one of the conversion of cellulose and hemicellulose to monomeric carbohydrates in the enzymatic hydrolysis and / or the relative content of soluble lignin to monomeric carbohydrates in the enzymatic hydrolysis; The results of the FTIR measurements are obtained by calculating a weighted linear combination of each of the FTIR measured absorbance values ​​at selected wavenumbers for multiple instants, and using the calculated weighted linear combination as an indicator of the measured concentration of monomeric carbohydrate at each instant.

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