JPH087031B2 - Cooling method for high viscosity liquid - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plate heat exchanger, and more particularly to a plate cooling device that handles cooling of a highly viscous liquid, including various resins, oils and fats, and varnishes. It can be applied to the cooling of ultra-high viscosity liquid, which has been considered to be quite difficult with the conventional plate type, such as spinning solutions such as viscose, sugar solutions, food fluids and dairy products.

2. Description of the Related Art As is well known, plate type heat exchangers supply fluids to adjacent passages via heat transfer plates to indirectly generate heat between these fluids. It is designed to be exchanged.

However, generally, regarding the heat transfer performance, especially the cooling capacity, it is common general knowledge that the cooling effect is higher as the cooling water temperature is lower and the cooling water amount is higher. However, it has been found that this is not always the case, as far as cooling viscous liquids is concerned. That is, according to an experiment using normal industrial water (water temperature of about 25 ° C to 30 ° C) as cooling water, heat transfer and flow performance on the treatment liquid side are largely controlled by the temperature on the cooling water side, and It was confirmed that the property became extremely poor and the pressure loss increased significantly, causing almost no flow.

To examine the relationship between the cooling water temperature and the heat transfer and fluidity in each of the passages that are adjacent to each other across the heat transfer plate, lower the cooling water temperature as t → t ′ → t ″ as shown in FIG. , And the temperature of the wall surface in contact with the high-viscosity liquid is also Tw → Tw ′ → Tw ″
And goes down. As a result, the viscosity of the high-viscosity liquid rapidly increases near the wall surface of the heat transfer plate, the velocity distribution in the passage changes almost in the same way as the temperature distribution shown in the figure, and the flow performance and heat transfer performance are significantly impaired. You can see what is going on.

Means for Solving the Problems In view of the above-mentioned problems, the present invention aims to provide an effective cooling method for a highly viscous liquid and a practical plate-type cooling device suitable for the method. When exchanging heat with water, the cooling water temperature is adjusted to an appropriate value corresponding to the viscosity of the treatment liquid so that the viscosity of the treatment liquid does not become excessively high and heat transfer performance and fluidity are improved. The basic idea is to recirculate at least a part of the cooling water heated by heat exchange. That is, a circulation passage for guiding the cooling water from the outlet side to the inlet side of the cooling water passage is provided, and a device for controlling the circulation amount is provided.

Action As a result of heat exchange between the treatment liquid and the cooling water via the heat transfer plate, the cooling water takes heat from the treatment liquid and rises in temperature, and conversely the treatment liquid is deprived of heat and cooled. It The cooling water whose temperature has risen in this way merges with the newly supplied cooling water and recirculates in the system. The cooling water may be entirely recirculated or only a desired part thereof may be recirculated. In any case, depending on the physical properties of the treatment liquid to be handled, the circulation amount is such that the viscosity does not increase to the extent that it interferes with internal system flow and heat transfer, and also secures the desired cooling performance. Control to maintain the proper cooling water temperature.

EXAMPLE An example of the present invention shown in FIG. 1 will be described.
The cooling device of this embodiment includes a plate heat exchanger (8) having a treatment liquid passage (4) and a cooling water passage (6) which are adjacent to each other via a heat transfer plate (2). The heat transfer plate (2) is laminated to form a plurality of alternating passages (4) and (6) according to the capacity required for the heat exchanger. The heat exchanger (8) in the figure is formed. Of the plate group, the left half shows a cross section along the through holes (6a) (6a) that connect the cooling water passages (6) to each other, and the right half shows the through holes that connect the processing liquid passages (4) to each other. (4a) shows a cross section along (4a).
The cooling water is once stored in the replenishment tank (10), and then the cooling water passage (6) is pumped through the inlet pipe (12) by the pump (14).
Supplied to When the cooling water flows through the cooling water passage (6), the cooling water draws heat from the processing liquid in the adjacent processing liquid passage (4), that is, the high-viscosity liquid, through the heat transfer plate (2) to raise the temperature. And head for the outlet pipe (16). The outlet pipe (16) guides the cooling water to the outside of the system, and the circulation passage (18)
Branch into the tank (10). In other words, the circulation passage (18) connects the outlet side and the inlet side of the cooling water passage (6). A flow rate control valve (20) is attached to the circulation passage (18), and the opening degree of the flow control valve (20) depends on the temperature of the cooling water to be supplied to the cooling water passage (6), that is, the temperature of the cooling water in the tank (10) in the illustrated example. A thermo controller (22) is provided for controlling the temperature.

Then, in the plate heat exchanger (8), the cooling water, which has taken up heat from the treatment liquid to rise in temperature, is introduced into the tank (10) through the circulation passage (18) and merged with the new cooling water, whereby the cooling water passage is formed. The temperature of the cooling water supplied to (6) increases. Further, the degree of the temperature rise is determined by the flow control valve (2
It is appropriately adjusted by controlling the circulation amount of cooling water in 0). For example, the treatment liquid is maintained at a suitable temperature at which the viscosity can be cooled to a temperature at which the viscosity does not interfere with heat transfer and flow. The means for performing such temperature control can be arbitrarily selected from those known in the field of automatic control, so here, in response to the signal from the thermo controller (22), the flow control valve (2
(0) is shown below as an example of opening and closing.

The following table shows the performance comparison between the case of the conventional cooling device and the case of the present invention with specific numerical values. The viscosity of the processing liquid is 90 cp at 100 ° C and 30 ° C.
That's 65,000 cp.

Conventionally, this industrial water, tap water, etc. are used as they are as cooling water (27
(° C) and used. As a result, in the conventional apparatus, the outlet temperature of the processing liquid was excessively cooled to 29 ° C., the viscosity suddenly increased and the pressure loss increased, resulting in the inability to flow the processing flow rate. . In the present invention, however, the cooling water that has been heated (50 ° C.) by heat exchange is recirculated and “heated” to 48 ° C. before being supplied. As a result, the fluidity was improved, the pressure loss was reduced, a predetermined flow rate was stably flowed, and the heat transfer coefficient for supply was also approximately doubled.

EFFECTS OF THE INVENTION According to the present invention, it is possible to obtain a plate-type cooling device that exhibits excellent heat transfer performance without impairing fluidity even for highly viscous liquids, and is used for cooling highly viscous or ultra-highly viscous liquids. It is important to contribute to the practical application of a plate heat exchanger that can be used for Moreover, since the temperature of the cooling water is raised without relying on a separate heat source, it is extremely advantageous from the viewpoint of cost and energy saving.

[Brief description of drawings]

FIG. 1 is a flow sheet of a plate-type cooling device for carrying out the present invention, and FIG. 2 is a temperature distribution diagram of treatment liquid and cooling water in passages adjacent to each other via a heat transfer plate. 2: Heat transfer plate 4: Treatment liquid passage 6: Cooling water passage 8: Plate heat exchanger 18: Circulation passage 20: Flow control valve 22: Thermo controller

Claims (1)

[Claims] 1. When supplying fluid to adjacent passages via a heat transfer plate to cause heat exchange between the fluids, a treatment liquid is supplied to one passage and a cooling water is supplied to the other passage. It is characterized in that the temperature of the cooling water in the passage is adjusted to an appropriate value corresponding to the viscosity of the processing liquid by supplying and recirculating at least a part of the cooling water heated by heat exchange. Cooling method for high viscosity liquid.