JPS6032482B2 - Control method of pseudo moving floor - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for controlling a simulated moving bed.

More specifically, the present invention relates to a method of controlling the flow rate of fluid introduced into or withdrawn from a simulated moving bed such that the maximum pressure within the simulated moving bed is the lowest. A packed bed consisting of four or more unit packed beds filled with a solid sorbent and arranged in series, the front end and the rear end of which are connected by a fluid passage and are inorganic. The fluid is circulated in one direction, the feed fluid and the desorbent fluid are introduced into the circulating fluid, and at the same time the non-sorbate-rich fluid and the sorbate-rich fluid (introduced into or about to be introduced into the bed) are introduced into the circulating fluid. The four types of fluids to be extracted are referred to as side streams in the following explanation, and the inlets and outlets of the side streams are arranged alternately along the flow direction of the circulating fluid, and these are circulated. It is known to carry out the separation of substances using so-called simulated moving beds whose position is moved intermittently in the direction of flow of a fluid.

In the simulated moving bed, a fluid transport means (hereinafter referred to as a circulation pump) is installed in the circulation channel to compensate for pressure loss that occurs when fluid circulates within the bed.

As mentioned above, two types of side flows are introduced into the pseudo moving bed,
Two types of side streams are extracted at the same time.

The flow rate of these four types of side streams is usually controlled by any one of the three types.
Regarding the type, the flow rate is controlled to a set value using a flow rate controller or the like, and the remaining type is carried out by a so-called pressure control method in which a flow valve is controlled to maintain the pressure in the bed constant. When there is only one circulation pump installed in the circulation flow path as in the well-known pseudo moving bed, the pressure on the suction side of the circulation pump, that is, the back pressure is the lowest pressure in the bed,
Normally, the remaining type of side flow control described above is performed so that this back pressure remains constant. By the way, the role of the circulation pump is
As mentioned above, the purpose is to compensate for pressure loss within the floor, so if only one circulation pump is installed,
The discharge pressure of the circulation pump is equal to the back pressure plus the pressure loss in the bed. The simulated moving bed needs to be a pressure vessel that can handle this discharge pressure, and if the pressure loss is large, the equipment will be expensive. To reduce the pressure resistance required for a simulated moving bed, install multiple circulation pumps.
It is necessary to compensate for the pressure loss in the bed by equally sharing it with each circulation pump. When a circulation pump is installed between each unit packed bed to equally share and compensate for the pressure loss within the bed, the pressure resistance required for the pseudo-moving bed will be the lowest. Even in such a simulated moving bed having a plurality of circulation pumps, it is preferable to perform the above-described pressure control on one of the side streams. This can be easily done by controlling the back pressure of a particular one of the plurality of circulation pumps to be constant. However, in a simulated moving bed, the physical properties and flow rate of the fluid flowing through each unit packed bed at the same time are not uniform.

Furthermore, when focusing on a specific unit packed bed, the physical properties and flow rate of the fluid flowing through this unit packed bed change periodically. Therefore, the pressure loss in each unit packed bed is not the same, and moreover changes periodically. Therefore, even if multiple circulation pumps are installed to share the pressure loss equally, if the back pressure of a particular circulation pump is controlled to be constant, the back pressure of the remaining circulation pumps will be cyclic. changed to,
Therefore, the discharge pressure also changes periodically. For example, it consists of four unit packed beds 101 to 104 as shown in FIG.
In a simulated moving bed with two circulation pumps A and B,
When the back pressure of A is constant, the relationship between the type of side stream introduced into or extracted from each unit packed bed, the pressure loss in each unit packed bed, and the back pressure and discharge pressure of B is as follows. As shown in the table (however, the pressure loss of each unit packed bed 101 to 104 in the state shown in FIG. 1 is assumed to be P and -P4).

Table 1 a: Feed fluid (introduced at the top of the unit packed bed) b: Non-sorbent fluid (extracted from the end of the unit packed bed) c: Desorbent fluid (
(introduced at the top of the unit packed bed) d: Sorptive fluid (extracted from the end of the unit packed bed) o: Back pressure of A The back pressure of the circulation pump is:
In order to prevent cavitation from occurring, it cannot be lowered below a certain value, so depending on the values of P and ~P4, circulation pump A may be used to maintain the back pressure of circulation pump B above a certain value. It is necessary to certify that the back pressure (Q) is large.

This causes an increase in the discharge pressure of the circulation pump B, and therefore an increase in the withstand pressure of the pseudo moving bed. For example, when the viscosity of the raw material fluid and the viscosity of the desorbent fluid are significantly different, such as when high-concentration high-fructose sugar solution is used as the raw material and water is used as the desorbent to separate the isomerized sugar into fructose and glucose, Depending on the flow rate of each side stream, P and P4 are large, and P2
and P3 become smaller. Therefore, in such a case, in Table 1, the back pressure of circulation pump B is highest at phase (1) and lowest at phase '3'. It is necessary to determine the back pressure (Q) of circulation pump A to As a result of considering a method to maintain the back pressure of a specific circulation pump at a constant value, we found that, instead of maintaining the back pressure of a specific circulation pump at a constant value, we decided to maintain the back pressure or discharge pressure of each circulation pump in the system in each phase by setting the highest value or the largest value. The present invention was completed based on the knowledge that the object can be achieved by controlling the side flow to maintain a constant back pressure or discharge pressure.

That is, it is an object of the present invention to provide a method for controlling a pseudo moving bed that does not require a large pressure resistance, and this purpose is to provide a method for controlling a pseudo moving bed that does not require a large pressure resistance. The fluid is circulated in one direction in the packed bed, which is made up of four or more unit packed beds, the front end and the rear end of which are connected by a fluid passage and are endless,
A raw material fluid and a desorbent fluid are introduced into this circulating fluid, and at the same time, a non-sorbent-rich fluid and a sorbent-rich fluid are extracted from the circulating fluid, and the raw material fluid inlet is connected to the fluid rich in non-sorbent fluid. The outlet, the desorbent fluid inlet, and the sorbate-rich fluid outlet are arranged sequentially along the flow direction of the circulating fluid, and their positions are intermittently arranged in the flow direction of the circulating fluid. In the simulated moving bed, a circulation pump is installed between two or more unit packed beds, and a pressure detector is installed in each circulation pump to detect the above two types of fluids introduced into the bed and extracted from the bed. The flow rates of three of the above two types of fluids to be discharged are controlled to the set value, and the flow rate of the remaining one is determined by selecting the pressure detector showing the lowest or highest pressure among the above pressure detectors. This can be easily achieved by controlling so that it is always constant.

To explain the present invention in more detail, the present invention relates to a method of controlling the side flow of a simulated moving bed so that the pressure resistance required of the simulated moving bed is reduced.

In the present invention, a circulation pump is installed between two or more unit packed beds.

In particular, it is preferable to install a circulation pump between each unit packed bed, and in this way, the withstand pressure required of the simulated moving bed can be minimized. These multiple circulation pumps equally share and compensate for the total pressure loss in the bed. A pressure detector is provided on the suction side or the discharge side of each circulation pump to detect the pressure of the fluid circulating in the bed. Each of these pressure sensors is in communication with a sidestream pressure control valve via a selection device. The selection device selects the one showing the lowest pressure or the highest pressure among the pressure detectors and communicates this with the side flow pressure control valve, so that this detector maintains a predetermined constant pressure. Open and close the pressure control valve to maintain the pressure. The selection of the detector exhibiting the lowest or highest pressure is based on the pressure indicated by each pressure detector using a common triad method.
This can be done, for example, by comparing pressures with each other. In addition, if the pressure loss of each unit packed bed can be accurately predicted by the position of the side stream, that is, the phase, by reducing the range of fluctuation in the operation of the pseudo moving bed, a pressure detector that indicates the lowest or highest pressure can be used. Since this can be predicted, it is also possible to select a pressure detector that indicates the lowest or highest pressure depending on the position of the side stream. In this case, a program for selecting a pressure detector depending on the position of the side stream may be created, and the pressure detector may be selected based on this program. In a simulated moving bed, the pressure loss of each unit packed bed is approximately constant while the side stream introduction or withdrawal position is constant, so the pressure detector need only be selected when the side stream position is changed. .

In the method of the present invention, the pressure detector showing the lowest pressure may be selected from among the pressure detectors and the side flow may be controlled so that the pressure remains constant, or the pressure detector with the highest pressure may be selected. The side flow may be controlled so that the pressure is constant.

When controlling the minimum pressure to be constant, the maximum pressure within the pseudo moving bed changes periodically within a certain range. On the other hand, when controlling the maximum pressure to be constant, the minimum pressure within the pseudo moving bed changes periodically within a certain range. In either case, it is preferable to keep the minimum pressure as low as possible without causing cavitation in the circulation pump. If the minimum pressure allowed in the bed is the same, the maximum pressure in the bed will be the same even if the above-mentioned deviation control method is used. However, if changes in pressure loss within the bed due to changes in operating conditions are taken into account, it is safer to control the side flow so that the minimum pressure remains constant. To explain the present invention with numerical values regarding a typical simulated moving bed, Fig. 2 shows a simulated moving bed consisting of eight unit packed beds, and shows the position where a side stream is introduced or extracted and the pressure loss of each unit packed bed. There is a relationship as shown in Table 2. This is the case when an aqueous high-fructose sugar solution is separated into fructose and glucose using water as a desorbent. This is a model of the pressure loss distribution that appears when the viscosity is between these two.
Table 2 a: Feed fluid (introduced at the top of the unit packed bed) b: Non-astringent fluid (extracted from the end of the unit packed bed) c: Desorbent fluid (
(Introduced at the top of the unit packed bed) d: Accommodating fluid (extracted from the end of the unit packed bed) In the pseudo moving bed shown in Figure 2, if the minimum pressure in the bed is 0.5, the number of operating circulation pumps The relationship between this and the maximum discharge pressure is shown in Table 3.

Table 3 (*1) The back pressure of A was constant (*2) The back pressure of A was 3.8 (*3) A,, A5 was operated (*4) A,, A3, A5, Operation of A7 As is clear from Table 3, in the method of detecting the pressure at a specific point in the simulated moving bed and controlling the side flow so that this value is maintained constant, the circulation pump does not cause cavitation. It is necessary to maintain the minimum pressure in the bed above a certain level to prevent this from occurring, and even if the control pressure of the side stream is increased and the number of circulation pumps is increased, the maximum discharge pressure of the circulation pump, and therefore the withstand pressure of the equipment, will be It doesn't decrease much.

However, when the method of the present invention detects the circulation pump with the lowest back pressure or the circulation pump with the highest discharge pressure and controls the side flow so as to maintain the back pressure or discharge pressure constant, By increasing the number of circulation pumps, it is possible to significantly reduce the withstand pressure of the device.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of a pseudo moving bed consisting of four unit packed beds and two circulation pumps, and the phase {1} in Table 1 is
Indicates the status of 101-104: Unit packed bed, A, B: Circulation pump, a
: raw material fluid, b: non-sorbate fluid, c: deconcentration fluid, d:
Sorption Cost Fluid: FIG. 2 is a schematic diagram of a pseudo-moving bed consisting of eight unit packed beds, and shows the state of phase '1} in Table 2. 201 to 208: unit packed bed, A, to A8: circulation pump, cv: circulation flow rate control valve, a: raw material fluid, b: non-sorbate fluid, c: desorbent fluid, d: sorbate fluid. O/Figure O2

Claims (1)

[Claims] 1. Consisting of four or more unit packed beds filled with a solid sorbent and arranged in series, the front end and the rear end are connected by a fluid passage, and the bed is endless. A fluid is unidirectionally circulated through a packed bed, and a feed fluid and a desorbent fluid are introduced into the circulating fluid, and a non-sorbate-rich fluid and a sorbate-rich fluid are simultaneously introduced into the circulating fluid. A raw material fluid inlet, a non-sorbent-rich fluid outlet, a desorbent fluid inlet, and a sorbent-rich fluid outlet are sequentially arranged along the flow direction of the circulating fluid, and In a pseudo moving bed that moves these intermittently in the flow direction of the circulating fluid, a fluid transport means is installed between two or more unit packed beds, and a pressure detector is installed on each fluid transport means. Then, the flow rates of three of the two types of fluid introduced into the bed and the two types of fluid extracted from the bed are controlled to set values, and the flow rate of the remaining one is controlled to the set value. 1. A method for controlling a pseudo moving bed, which comprises selecting a pressure detector showing the lowest or highest pressure among the pressure detectors and controlling the pressure so that the pressure is always constant. 2. A method for controlling a simulated moving bed according to claim 1, characterized in that a fluid transport means is installed between each unit packed bed. 3. The method for controlling a simulated moving bed according to claim 1 or 2, characterized in that the selection of the pressure detector indicating the lowest or highest pressure is performed based on the pressure indicated by the pressure detector. How to do it. 4. In the method for controlling a pseudo moving bed according to claim 1 or 2, the selection of the pressure detector that indicates the lowest or highest pressure is determined by the position of the fluid inlet into the bed and the pressure from the bed. A method characterized in that the method is carried out based on the position of a fluid outlet. 5. A method for controlling a simulated moving bed according to any one of claims 1 to 4, characterized in that the simulated moving bed is composed of eight unit packed beds. 6. A method for controlling a simulated moving bed according to any one of claims 1 to 5, characterized in that the raw material fluid is an isomerized saccharification aqueous solution, and the desorbent fluid is water.