Field

The invention relates to a heteroazeotropic extractive distillation method and apparatus. Background

In a heteroazeotropic extractive distillation process that is used to separate water, at least one organic acid, and furfural, furfural being capable of acting both as a former of azeotrope and as an extractant.

Furfural polymerizes easily particularly in acid process conditions. The polymerized furfural, in turn, contaminates a column and/or a reboiler of the heteroazeotropic extractive distillation process and forms blockages on surfaces of the thermal exchange of the process. The contamination and the blockages may disturb a mechanical operation of the process and lower a quality of an end product. For example, dynamics of the process and a heat transfer coefficient of the structures and materials may change. To clean the process system requires the process operation to be stopped for a substantially long time and/or undesirably often, which shortens the process operational and causes economical losses. There have been attempts to reduce these problems by lowering a process temperature and/or pressure. However, the attempts have not proved effective or at least effective enough. Hence, there is a need to improve the process.

Brief description

The present invention seeks to provide an improvement.

The invention is defined by the independent claims. Embodiments are defined in the dependent claims.

List of drawings

Example embodiments of the present invention are described below, by way of example only, with reference to the accompanying drawings, in which Figure 1 illustrates an example of heteroazeotropic extractive distillation process apparatus;

Figure 2 illustrates an example of a data processing apparatus; and

Figure 3 illustrates of an example of a flow chart of a heteroazeotropic extractive distillation method.

Description of embodiments

The following embodiments are only examples. Although the specification may refer to "an" embodiment in several locations, this does not necessarily mean that each such reference is to the same embodiment(s), or that the feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments. Furthermore, words "comprising" and "including" should be understood as not limiting the described embodiments to consist of only those features that have been mentioned and such embodiments may also contain features/structures that have not been specifically mentioned. All combinations of the embodiments are considered possible if their combination does not lead to structural or logical contradiction.

It should be noted that while Figures illustrate various embodiments, they are simplified diagrams that only show some structures and/or functional entities. The connections shown in the Figures may refer to logical or physical connections. It is apparent to a person skilled in the art that the described apparatus may also comprise other functions and structures than those described in Figures and text. It should be appreciated that details of some functions, structures, and the signalling used for measurement and/or controlling are irrelevant to the actual invention. Therefore, they need not be discussed in more detail here.

The expression "azeotrope" refers to a mixture of substances wherein vapour and liquid compositions are identical in a phase equilibrium. The azeotrope corresponds to an extreme point (minimum, maximum or saddle point) in a boiling temperature isobar or in a vapour pressure isotherm. The expression "azeotropic distillation" refers to either distillation of azeotropic mixtures or distillation wherein an azeotrope forming component ("entrainer") is added to a process.

The expression "extractive distillation" refers to distillation wherein a fully soluble, azeotrope forming component ("entrainer") boiling at a relatively high temperature is added to a distillation column above the actual feed flow. Entrainer increases the relative volatility of the components and enhances separation of components, which is the main target of distillation.

Extraction, per se, refers to a process wherein a desired substance in a mixture dissolves in a solvent while the rest of the substances are insoluble in said solvent. In the mixture, the substances are completely mixed up with one another and the mixture, perse, may contain end products of chemical reactions.

The expression "heteroazeotrope" refers to an azeotrope having, in addition to the vapour phase, two liquid phases present.

The expression "heteroazeotropic distillation" refers to either distillation of heteroazeotropic mixtures or distillation wherein a heteroazeotrope forming component ("entrainer") is added to a process.

The expression "heteroazeotropic extractive distillation" refers to a combination of heteroazeotropic distillation and extractive distillation. The component to be added, boiling at a relatively high temperature, changes relative volatilies of components to be separated and boiling at a lower temperature, and it forms a low boiling azeotrope with any one of the remaining components. The heteroazeotropic extractive distillation may be a part of a bio-refining process where bio-mass fractions are vaporized and/or dried. Such a process provides a flow of bio-mass component, organic acid(s) and furfural, which is vaporzed and/or dried. A person skilled in the art is familiar with these terms and definitions, per se.

A column is a tubular, upright construction wherein substances fed thereto become completely mixed up together. Such a column may be used for separating different fluids from each other based on the properties of the substances in various conditions. A typical field of application is chemical industry. The column, perse, is known to those skilled in the art.

Figure 1 shows an apparatus for a heteroazeotropic extractive distillation process. The heteroazeotropic extractive distillation process apparatus system comprises at minimum a reboilerrereboiler 102 and a distillation column 100. The distillation column 100 processes its contents in at least one distillation condition. The distillation column 100 receives or has a mixture 104 including water, at least acetic acid and formic acid, and at least one extractant, which are included in the contents of the distillation column 100. The distillation column 100 may also include at least one other organic acid. The reboiler 102 receives contents of the distillation column 100. The reboiler 102 may receive a reboiler portion of the contents of the column 100, the reboiler portion being a percentage lower than 100 % and/or a fraction of a plurality of fractions of the contents of the distillation column 100. The distillation column 100 may operate for instance in a pressure range from about 0.2 bar to about 2.5 bar. In an embodiment, the pressure is about 1 bar. In an embodiment, the distillation column 100 has a vacuum. In the distillation column 100, the processing temperature may be from about 40°C to about 200°C, for example. However, the conditions of the column 100 are not restricted to these examples.

In an embodiment, the one or more organic acids may include acetic acid and formic acid.

The extractant may include one extractant or more than one extractant mixed together. One of the at least one extractant is furfural (C4H3OCHO). Said furfural is allowed to react with one or more organic acids to produce reaction products in the column 100 and/or in the reboiler 102. The distillation process in the column 100 also generates polymerized furfural, the polymerization of furfural being irreversible or unlikely reversible in the distillation process. Hence, polymerized furfural is a thermosetting polymer, which hardens on surfaces causing contamination and blockages, for example. Polymerization of furfural is a chemical process where a plurality of monomers of furfural are combined by a chemical bond, and thus formed combination is a polymer of furfural.

The vaporizing process in the reboiler 102 may also generate polymerized furfural. Namely, distilling water and the at least one organic acid using furfural in a heteroazeotropic extractive distillation process, polymerization of furfural takes place. Distilling lignocellulosic biomass of plants or using furfural in a heteroazeotropic extractive distillation process may also cause polymerization of furfural.

The polymerization of furfural may increase viscosity of the mixture 104 in the distillation column 100 when the mixture 104 is kept in a constant condition. The polymerization of furfural may increase a boiling point of the mixture 104 the mixture 104 is kept in a constant condition. The polymerized furfural may also be sticky, which results in contamination and blockages in the process system. The viscosity of the mixture 104 may increase as a monotonically increasing function of a degree of the polymerization of furfural when the mixture 104 is kept in a constant condition. Correspondingly, the boiling point of the mixture 104 may increase as a monotonically increasing function of the degree of the polymerization of furfural when the mixture 104 is kept in a constant condition.

To avoid or alleviate the problem(s) caused by polymerization of furfural, a portion including polymerized furfural that is formed in a process of the apparatus is removed from the contents of the distillation column 100 at a rate that is equal to or higher than a threshold removal rate of the column 100. That allows dynamics of the process, heat transfer coefficient of the structures and materials remain unchanged or at least within an acceptable range for a long time. That is, the distillation column 100 may be configured to remove the portion. In an embodiment, the process may be set to maintain the removal rate at a desirable level. Such a removal may be performed mechanically using at least one suitable valve, for example.

In an embodiment, the removal may be controlled by a processing unit 200, which may also control the heteroazeotropic extractive distillation process otherwise. The threshold removal rate of the column 100, in turn, keeps viscosity of the mixture 104 below a predetermined threshold viscosity value and/or a boiling point of the mixture 104 below a predetermined threshold boiling value. The portion that flows out of the column 100 at a removal rate may comprise solid matter and/or dry matter. The removal of the polymerized furfural is performed in order to reduce harmful effects of the polymerized furfural to the heteroazeotropic extractive distillation process. On the other hand, the removal rate may be determined based on at least one of the following: a boiling point, viscosity, a percentage of solid matter and dry matter in the column 100. The boiling point, viscosity, the percentage of solid matter and/or dry matter may be measured using at least one sensor and/or by sampling, for example. A person skilled in the art is familiar with the at least one sensor and sampling which are used to measure parameters for determining the boiling point, viscosity, the percentage of solid matter and/or dry matter.

In an embodiment, the data processing unit 200 may receive data from at least one sensor (not shown in Figures) of the apparatus or the system for the heteroazeotropic extractive distillation process. The data processing unit 200 may additionally or alternatively receive data from a user through a user interface 202, the data including information necessary for determining the threshold removal rate. The data processing unit 200 may further receive data on estimated state of the process or data that allows the data processing unit 200 determine estimated state of the process, the estimated state including information for determining the threshold removal rate.

In an embodiment, a lower section 106 of the column 100 may remove the portion. The lower section 106 is below a center of the column 100. In an embodiment, the portion is removed from a bottom of the column 100. The lower section 106, which also includes the bottom, may have a valve for controlling the removal rate. In an embodiment, the valve may be opened and closed repeatedly such that when the valve is open the removal of the portion is possible. In an embodiment, the valve is open continuously, a cross section of the valve limiting the rate of removal at or above the threshold removal rate. In an embodiment, although the valve is continuously open a flow through it may be adaptively varied. In an embodiment, any control of the valve may be performed by the data processing unit 200.

The portion removed from the lower section 106 may be fed to the reboiler 102, a separator 108 or be destroyed, for instance.

In an embodiment, heavy fractions including polymerized furfural may be removed from a lower section 106 or the bottom of the distillation column 100, namely polymerized furfural can be considered to belong to the heavy fractions. The heavy fractions including polymerized furfural removed from the lower section 106 may be fed to the reboiler 102, a separator 108 or be destroyed, for instance.

In a corresponding manner, a portion, which corresponds or relates to the portion of the column 100 and has the same chemicals including polymerized furfural, can be removed from contents of the reboiler 102 at a rate that is equal to or higher than a threshold removal rate of the reboiler 102. The reboiler 102 is configured to receive contents of the distillation column 100. The threshold removal rate keeps viscosity of the mixture 104 below a predetermined threshold viscosity value and/or a boiling point of the mixture 104 below a predetermined threshold boiling value. Although the mixture 104 within the distillation column 100 and the mixture 104 within the reboiler 102 may be different somehow, they can be considered the same mixture 104 because the mixture of the reboiler 102 originates from the mixture 104 of the distillation column 100.

In general, the column 100 and/or the reboiler 102 are/is configured to remove said portion in order to reduce harmful effects of the polymerized furfural to the heteroazeotropic extractive distillation process. The heteroazeotropic extractive distillation process comprises the column 100 and the reboiler 102.

The reboiler 102 may be configured to remove the portion. In an embodiment, the process may be set to maintain the removal rate at a desirable level. Such a removal may be performed mechanically using at least one suitable valve, for example. In an embodiment, the removal of the portion may be controlled by a processing unit 200.

The threshold removal rate of the reboiler 102, in turn, keeps viscosity of the mixture 104 below a predetermined threshold viscosity value and/or a boiling point of the mixture 104 below a predetermined threshold boiling value. The removal of the polymerized furfural is performed in order to reduce harmful effects of the polymerized furfural to the heteroazeotropic extractive distillation process.

The threshold removal rate, i.e. the threshold removal rate from the column 100 and/or the threshold removal rate of the reboiler 102, may be determined by testing or calibration measurements, experience of previous processes, simulation, or by theoretical analysis or estimation.

In an embodiment, the heavy fractions including polymerized furfural may be removed from a lower section 110 or a bottom of the reboiler 102 in a corresponding manner to the column 100. The heavy fractions including polymerized furfural removed from the lower section 110 may be fed to the separator 108 or be destroyed, for instance.

In an embodiment, the distillation column 100 is configured to remove the portion as a continuous or intermittent flow that is equal to or higher than a flow corresponding to the threshold removal rate of the column 100 from the distillation column 100. On the other hand, the removal rate may be determined based on at least one of the following: a boiling point, viscosity, a percentage of solid matter and dry matter in the column 100. The boiling point, viscosity, the percentage of solid matter and/or dry matter may be measured using a sensor and/or by sampling, for example.

In an embodiment, the reboiler 102 is configured to remove the portion as a continuous or intermittent flow that is equal to or higher than a flow corresponding to the threshold removal rate of the reboiler 102 from the reboiler 102. The flow out of the column 100 and the reboiler 102 may be equal to or higher than either of the threshold removal rate of the column 100 and the reboiler 102. A heightened rate of removal results in improvement in at least either of the column 100 or the reboiler 102 or both.

In an embodiment, the portion may be removed from both the column 100 and the reboiler 102 as a continuous or intermittent flow that is equal to or higher than a flow corresponding to the threshold removal rate. Here the flow out of the column 100 and the reboiler 102 may be equal to or higher than a combined threshold removal rate of the column 100 and the reboiler. Or the flow out of the column 100 and the reboiler 102 may be equal to or higher than either of the threshold removal rate of the column 100 and the reboiler 102. Namely, a heightened rate of removal results in improvement in at least either of the column 100 or the reboiler 102 or both.

In an embodiment, the distillation column 100 is configured to remove the portion including heavy fractions, which include the polymerized furfural.

In an embodiment, the reboiler 102 is configured to remove the portion including heavy fractions, which include the polymerized furfural.

In an embodiment, the distillation column 100 is configured to remove the portion at the rate that is equal to or higher than the threshold removal rate of the column 100. The portion may include solid matter and/or dry matter. The threshold removal rate may keep viscosity of the mixture 104 within a predetermined range from a viscosity value at a beginning of the process. The threshold removal rate may keep a boiling point of the mixture 104 within a predetermined range from a boiling point at a beginning of the process.

In an embodiment, the reboiler 102 is configured to remove the portion at the rate that is equal to or higher than the threshold removal rate. The threshold removal rate may keep viscosity of the mixture 104 within a predetermined range from a viscosity value at a beginning of the process. The portion may include solid matter and/or dry matter. The threshold removal rate may keep a boiling point of the mixture 104 within a predetermined range from a boiling point at a beginning of the process. On the other hand, the removal rate may be determined based on at least one of the following: a boiling point, viscosity, a percentage of solid matter and dry matter in the reboiler 102. The boiling point, viscosity, the percentage of solid matter and/or dry matter may be measured using a sensor and/or by sampling, for example.

In an embodiment, the threshold removal rate may be the same in the column 100 and the reboiler 102. In an embodiment, the threshold removal rate may be different in the column 100 and the reboiler 102.

In an embodiment, the removal rate may be the same in the column 100 and the reboiler 102. In an embodiment, the removal rate may be different in the column 100 and the reboiler 102.

In an embodiment, the distillation column 100 is configured to remove the portion including heavy fractions with the polymerized furfural at a rate that is larger than about 0.5 w-%/h of a liquid hold-up of the column 100. The column liquid hold-up refers to a liquid volume inside a column 100 at that moment. That may correspond to a degree of filling.

In an embodiment, the reboiler 102 is configured to remove the portion including heavy fractions with the polymerized furfural at a rate that is larger than about 0.5 w-%/h of a degree of filling of the reboiler 102. In an embodiment, the degree of filling may be determined based on a mass of the mixture 104 in the distillation column 100. The degree of filling may be determined as a ratio between a mass of the mixture 104 at a certain moment and a mass of the mixture 104 when the reboiler 102 is full of the mixture 104. In an embodiment, the degree of filling may be determined based on a volume of the mixture 104 in the reboiler 102. The degree of filling may be determined as a ratio between a volume of the mixture 104 at a certain moment and a total volume of the reboiler 102.

In general in this embodiment, the distillation column 100 and/or the reboiler 102 are/is configured to remove the portion including heavy fractions with the polymerized furfural at a rate that is larger than about 0.5 w-%/h of a degree of filling of the column 100 and/or a degree of filling of the reboiler 102.

In an embodiment an example of which is illustrated in Figure 1, a vaporized chemicals of the portion may be fed back to the distillation column 100 from the reboiler 102. In an embodiment, a separator 108 may receive the portion that is removed from the distilling column 100. The separator 108 may perform a vaporizing, filtering or drying process to the portion. A sub-portion of the portion may be fed back to the distillation column 100 or the reboiler 102, the sub-portion being a part that is vaporized from the portion during vaporizing or drying process.

In an embodiment, a separator 108 may receive the portion that is removed from the reboiler 102. In an embodiment, the separator 108 may return the sub-portion back to the reboiler 102 in response to receiving the portion from the reboiler 102, the sub-portion being a part that is vaporized from the portion during vaporizing or drying process.

In an embodiment, the separator 108 may return the sub-portion back to the distilling column 100 in response to receiving the portion from the distilling column 100. Alternatively, the separator 108 may return the sub-portion back to the reboiler 102 in response to receiving the portion from the reboiler 102. In an embodiment, the portion may be vaporized using mechanical vapor recompression (MVR) method in the separator 108. The MVR vaporization is an advantageous method to vaporize the portion received from the distillation column 100, the reboiler 102 or a process arrangement 112. The process arrangement 112 may be a separate process or the bio-refining process, which comprises the column 100 and the reboiler 102, may include the process arrangement 112.

In an embodiment, vaporizing or drying the portion of at least one of the column 100 and the reboiler 102 with fractions from a process arrangement 112 of a bio-refining process. The process arrangement 112 excludes the column 100 and the reboiler 102.

Figure 2 illustrates an example of the data processing unit 200 that the heteroazeotropic extractive distillation apparatus may comprise. The data processing unit 200 may comprise one or more processors 204, and one or more memories 206. The one or more memories 206 may include a suitable computer program code for receiving measurement data from the heteroazeotropic extractive distillation process. The one or more memories 206 and the computer program code may, with the one or more processors 204 cause data processing unit 200 to output process control data for controlling the heteroazeotropic extractive distillation process based on the measurement data. The measurement data may comprise data on viscosity and/or a boiling point of the mixture 104. A person skilled in the art is familiar with a measurement or observation of the viscosity and/or temperature of the mixture 104 in the distillation column 100 and/or in the reboiler 102. The process control data may adapt, vary and/or differentiate the rate at which the portion is removed from the distillation column 100 and/or from the reboiler 102. The solution presented in this document may slow down the production speed of furfural polymer.

Figure 3 is a flow chart of the heteroazeotropic extractive distillation method. In step 300, a mixture 104 of water, at least one organic acid and furfural, the furfural being used as a former of azeotrope and an extractant in the mixture 104, is distilled in a distillation column 100.

In step 302, a portion including polymerized furfural that is formed in the method is removed at a rate that is equal to or higher than a threshold removal rate from the distillation column 100 and/or from a reboiler 102, which receives contents of the distillation column 100, the threshold removal rate keeping viscosity of the mixture 104 below a predetermined threshold viscosity value and/or a boiling point of the mixture 104 below a predetermined threshold boiling value.

The method shown in Figure 3 may be controlled and/or monitored using a logic circuit solution or at least one computer program of the data processing unit 200. The computer program may be placed on a computer program distribution means for the distribution thereof. The computer program distribution means is readable by a data processing device, and it encodes the computer program commands, carries out the measurements and optionally controls the processes on the basis of the measurements. The computer program may be distributed using a distribution medium which may be any medium readable by the controller. The medium may be a program storage medium, a memory, a software distribution package, or a compressed software package. In some cases, the distribution may be performed using at least one of the following: a near field communication signal, a short distance signal, and a telecommunications signal. It will be obvious to a person skilled in the art that, as technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the example embodiments described above but may vary within the scope of the claims.