JPH0129553B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solid-liquid packed bed reactor that generates gas as a reaction product.

A packed bed reactor has conventionally been used as an apparatus for carrying out a solid-liquid contact reaction in which one of the reactants is a solid substance that does not dissolve in a liquid, such as a solid catalyst. In order to maximize the solid-liquid contact area per reactor volume, this type of reactor molds the solid substance into particles of a certain size and fills the interior of the reactor with the particles most densely. is advantageous,
Usually carried out.

By the way, microorganisms immobilized using any gelling agent are not strictly solid, but in practice,
Can be handled in the same way as solid catalysts. Therefore, a packed bed reactor in which immobilized microorganism gel is molded into particles and packed in a column is also used as a reaction device for carrying out a solid-liquid reaction using immobilized microorganisms. In this case, when a reaction such as alcohol fermentation in which an equimolar amount of carbon dioxide gas is produced simultaneously with the production of alcohol, the following drawbacks occur.

Since the volume occupied by the reaction liquid is reduced by the space (gas hold-up) occupied by the carbon dioxide gas that has grown into bubbles in the reactor, the residence time of the reaction liquid is reduced, and as a result, the reaction rate is reduced.

Bubbles often stagnate between gel particles, and therefore the vicinity of the bubbles tends to become so-called dead space, which reduces the solid-liquid contact area and lowers the reaction rate.

These drawbacks are not limited to alcoholic fermentation.
It also occurs when immobilized microorganisms are used to perform anaerobic fermentation such as methane fermentation and denitrification.

Bubbles existing in the reactor become a problem because the volume occupied by an equimolar amount of gas is approximately 10 ³ times the volume of the liquid, and the higher the reaction rate, the more this problem becomes impossible to ignore. It's coming. One of the causes of such drawbacks is due to the structure of the packed bed reactor. In other words, in a conventional packed bed reactor as shown in Figure 1, there are no open parts other than the supply port and outlet for the reaction liquid, so the bubbles generated as a result of the reaction have no choice but to flow toward the outlet together with the reaction liquid. I don't get it. That is, due to the pressure of the bubbles generated in the packed bed, the bubbles move toward the outlet so as to push apart the filled gel and the reaction liquid, and the extruded reaction liquid also moves toward the outlet together with the bubbles. On the other hand, air bubbles that do not have enough force to pass through the gel particles remain between the gel particles until the reaction progresses and new gas is generated, increasing the pressure. In particular, air bubbles generated near the reactor inlet remain stagnant among the gel particles until they reach the reactor outlet and gradually move toward the outlet, which causes an increase in gas holdup in the packed bed. Another reason is due to the physical properties of the immobilized microbial gel. Gelling agents that immobilize microorganisms include polysaccharides, protein-based polymeric substances, polymeric substances with added crosslinking agents, etc., but since the interior of the gel enclosed by these gelling agents is mostly water, It is an elastic body with high adhesiveness. For this reason, when pressure is applied to the filled gel, the gel may be destroyed or the gels may stick together, blocking the liquid flow path and causing uneven flow. In the reactor shown in Figure 1, it was found that when the gas generated in the packed bed forms bubbles and expands, pressure is applied to the gel particles, causing them to stick together.

Therefore, when carrying out a reaction that generates gas in a packed bed reactor filled with immobilized microorganism gel formed into particles, (1) the gas generated as a result of the reaction must be immediately discharged outside the packed bed; The important issues are to lower the gas holdup in the packed bed, and (2) to prevent gel particles from sticking together to eliminate uneven flow of liquid in the packed bed.

The present inventors have solved these problems by using a reactor with a structure that satisfies the conditions shown below.
It has been found that the above-mentioned drawbacks can be overcome. That is, (1) the flow direction of the reaction liquid and the flow direction of bubbles are different in the entire area or part of the packed bed, and (2) the bubbles that escape from the packed bed are collected and removed from the reactor. It shall have a space with an exhaust hole for discharging the air.

Examples of reactors that satisfy these conditions are shown in
It is shown in Figure 6. These reactors are characterized by the fact that the outlet for the reaction liquid is different from the outlet for the generated gas, and that the surface of the packed bed is a free surface. The height of the packed bed is usually set to 1 to prevent the gel particles from collapsing under their own weight and blocking the flow path of the reaction solution, or from making it difficult for air bubbles to escape from the gel layer.
It is desirable to make it less than m.

With such a structure, as soon as the gas generated in the packed bed forms bubbles, it rises due to buoyancy and moves from the top surface of the packed bed, which is a free surface, to the space, as shown in Figure 1. Compared to a reactor in which air bubbles remain in the packed bed up to the outlet of the reaction liquid, the gas hold-up in the packed bed is significantly reduced, and stable continuous reaction can be achieved at a high reaction rate.

Next, the structure of the reactor will be explained. 1st~
In Figure 6, 1 is a packed layer. 6 is a gel in which microorganisms are immobilized and made into particles with a diameter of 2 to 10 mm. A reactant that serves as a nutrient source for microorganisms is supplied from 2, and reacts with the microorganisms on the surface of the gel particles while traveling inside the packed bed toward the exit 3. 4 indicates the flow direction after the reaction. 5 shows the flow direction of the gas produced as a result of the reaction. In Figures 2 to 6, 7 is a space for collecting air bubbles coming out of the packed bed, and a gas outlet 8 is provided here to make it easier for the air bubbles to escape from the packed bed and to reduce the pressure inside the reactor. Prevent rise. The basic structure of the present invention is shown in FIG.
Figures 3 to 5 are examples of improvements in which the reaction liquid flows easily within the packed bed. In FIG. 3, 9 is a baffle plate. The flow direction of the reaction liquid flowing through the packed bed is meandered up and down by vertically partitioning plates with gaps at the top and bottom alternately. In Figure 4, the entire reactor is angled at an angle of less than 30° so that the reaction liquid flows by gravity. Figure 5 shows the reaction solution outlet.
It is intended to be provided at a position 11 higher than the filling surface when the gel is most densely packed, so that the buoyancy of the bubbles causes the gel particles to float, making it easier for the bubbles to escape, and also to help mix the liquid. 2 to 5 are all horizontally elongated, but FIG. 6 is an application of this to a vertically elongated image. Reference numeral 10 denotes a perforated plate having a large number of holes with a diameter smaller than the gel particle diameter. The reaction solution flowing down from the top to the gel layer reacts in the gel layer and falls through the holes in the porous plate to the gel layer at the lower stage. The generated gas is discharged to the outside of the reactor through the side spaces of each stage.

Since the device of the present invention has the above-mentioned structure, the gas generated as a result of the reaction is quickly discharged outside the packed bed, reducing gas hold-up inside the packed bed, and preventing gel particles from sticking together, making it industrially suitable. advantageous to

Next, examples will be described.

Viable cells of Satucharomyces cerevisiae yeast 7.2
Add 4.0 g of carrageenan to 120 c.c. of physiological saline containing g (wet cell) and immobilize at 10°C.
The molded product was packed into the apparatus shown in FIG. 2 and the reactor shown in FIG. 1 for comparison. As a nutrient source, waste molasses with a sugar concentration of 15% adjusted to pH 5.0 was used, and alcoholic fermentation was performed at 30°C. With the production of alcohol, equimolar CO ₂ is generated. The performance of the reactors was compared by measuring the alcohol concentration at the outlet of the reactor and the alcohol production rate while varying the amount of reaction liquid supplied to each reactor at three levels. The experimental results are shown in Figure 7. Areas where a lot of _CO2 gas is generated,
That is, it can be seen that the reaction progresses 1.2 times faster in the reactor shown in FIG. 2 than in the reactor shown in FIG. 1 where the amount of reaction liquid supplied is large.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a conventional packed bed reactor;
Figures 2 to 5 are cross-sectional views of examples of the reactor of the present invention.
The figure shows a horizontal reactor, and Figure 6 shows a vertical reactor. FIG. 7 is a graph showing the relationship between the reaction liquid supply amount and the outlet alcohol concentration or alcohol production rate for the reactor of the present invention and a comparative example. 1... Gel packed layer, 2... Reaction liquid inlet, 3...
Reaction liquid outlet, 4... Reaction liquid flow direction, 5... Gas flow direction, 6... Gel particles, 7... Space,
8... Gas discharge port, 9... Baffle plate, 10... Perforated plate, 11... Distance between the surface of the gel closest packed layer and the liquid level.

Claims (1)

[Scope of Claims] 1. In a packed bed reactor in which a solid-liquid reaction is carried out using immobilized microbial gel formed into particles as a catalyst and gas is generated during the reaction, the upper surface of the packed bed inside the reactor A reaction device filled with immobilized microbial gel, characterized in that it has a space provided with an outlet for discharging gas released from the packed bed to the outside of the reactor. 2. The reaction device according to claim 1, wherein one or more baffle plates are provided in the packed bed to meander the flow of the liquid. 3. The reactor according to claim 1, wherein the packed bed is inclined at an angle of 30° or less from the horizontal plane. 4. The reaction according to claim 1, wherein the outlet of the reaction solution is positioned 10 to 30% higher than the surface of the packed bed when the granular immobilized microbial gel is most densely packed. Device. 5. The reactor according to claim 1, wherein at least one packed bed having a perforated plate on the bottom is stacked in a substantially vertical direction in a reaction device, and has a space provided with an outlet for discharging gas. Reactor.