JPS5929076A - Crystallizing vessel for desalting seawater by refrigeration - Google Patents

Abstract

PURPOSE:To obtain a crystallizing vessel for desalting the seawater by direct contact between a liquefied gas and the sewater capable of forming superior crystals, by installing an injection pipe of a recycling brine at a specified position of said vessel, and giving agitation effect by the injection to prevent local supercooling. CONSTITUTION:A liquefied gas evaporator 2 is set in the crystallizing vessel 1, and the liquefied gas is fed through a pipe 3 and the seawater through a pipe 4 into the vessel 1, respectively. The gas is brought into direct contact with the seawater in the evaporator 2, and after the heat exchange, the gas is drawn out from a gas pipe 5, and used mainly for fuel. Ice crystals 7 are produced in the seawater by cooling it through the heat exchange with the gas at that time. In order to stir the seawater surrounding the evaporator 2 sufficiently, the recycling brine is jetted near the side of the lower end of the evaporator 2 from its recycling pump 28 through a pipe 29, thus resulting in preventing supercooling near the evaporator 2, and operating satisfactory crystallization.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a refrigerated seawater desalination crystallization tank, and in particular, a jet pipe of a recirculation line is provided at a specific position within the crystallization tank, and the stirring effect of the jet can provide localized appropriate cooling. The present invention relates to a refrigerated crystallization tank for seawater desalination that allows direct contact between liquefied gas and seawater, which can prevent the above and perform good crystallization.

When operating a cold, wire-type seawater desalination equipment, when liquefied gas such as LNG is blown into the seawater in the crystallization tank from the blowing nozzle of the vaporizer, the liquefied gas will not flow into the seawater if blown under atmospheric pressure. It exchanges heat with and expands approximately 600 times. Therefore, the seawater around the blowing nozzle of the vaporizer is sufficiently agitated by the vaporized gas, and no localized cooling occurs around the nozzle.

However, as the crystallization pressure is increased, the degree of expansion due to vaporization of the liquefied gas decreases, for example, the crystallization pressure is 30 kg/c.
When carried out with n12, 1 during crystallization under atmospheric pressure
/30. This reduces the agitation around the blow nozzle of the vaporizer, leading to localized cooling around the nozzle.

One possible way to stir the seawater around the vaporizer nozzle is to install a stirrer,
Installation of an agitator requires installation costs and power costs.

An object of the present invention is to solve the above problems and provide a refrigerated seawater desalination crystallization tank using an agitation method that is easy to install and does not require power costs.

To summarize the present invention, the 11 tanks of refrigerated seawater desalination products of the present invention are installed at the lower end of a liquefied gas vaporizer provided in a crystallization tank in a refrigerated seawater desalination apparatus that uses direct contact between liquefied gas and seawater. It is characterized by the provision of one or more recirculation brine ejection pipes near the side.

In the present invention, ice crystals generated by contact between liquefied gas and seawater in a crystallization tank of a refrigerated seawater desalination apparatus,
When condensed seawater (hereinafter referred to as brine), which has a high salt concentration due to the formation of ice crystals, is led to a separation tower and separated into ice crystals and brine, the separated brine is recirculated to the crystallization tank. At this time, this is ejected from the side of the crystallization tank through a single or multi-convergent jet pipe that reaches near the side of the lower end of a liquefied gas vaporizer installed in the crystallization tank, and the gas is ejected from the side of the vaporizer around the blowing nozzle of the vaporizer. By stirring the seawater, it is possible to prevent the area around the lower part of the vaporizer from being properly cooled, and to perform a good crystallization operation. or,
The crystallization tank of the present invention is applicable not only to low-pressure crystallization (no hydrate is produced and no decomposition tank is required), but also to high-pressure crystallization (hydrate is produced and a decomposition tank is provided). can be effective.

Next, the present invention will be specifically explained with reference to the drawings. That is, FIG. 1 shows a system showing a specific example of a crystallization operation using the refrigerated seawater desalination crystallization tank of the present invention within a pressure range in which no hydrate is produced and only ice crystals are precipitated. 1 is a crystallization tank, 2 is a liquefied gas vaporizer, 3 is a liquefied gas pipe, 4 is a seawater pipe, 5 is a vaporized gas pipe, 6 is a pressure regulating valve, and 7
is an ice crystal, 8 is a seawater liquid level, 9 is a liquid level sensor, 10 is a flow rate adjustment valve, 11 is an ice crystal and brine pipe, 12 is a separation/washing tower, 13 is a separation section, and 14 is an ice crystal layer , 15 is a cleaning water nozzle, 16 is a cleaning water, 17 is a scraper, 18 is a melting section, 1
9 is a heat exchanger, 20 freshwater pipes, 21 are freshwater flow rate control valves, 22.24 are some freshwater pipes, 23 are freshwater pumps, 2
5 is a separated brine, 26 is a separated brine pipe,
27 is a separate brine circulation pipe, 28 is a brine circulation pump, 29 is a circulating brine inflow pipe, 30 is a brine discharge pipe, and 31 is a ventilation pipe.

As shown in FIG. 1, a liquefied gas vaporizer 2 is installed in a crystallization tank 1, and a liquefied gas pipe 3 supplies liquefied gas, and a seawater pipe 4 supplies seawater to the vaporizer. Take. The liquefied gas vaporizer 2 in the crystallization tank 1 directly contacts seawater, exchanges heat, and vaporizes the gas, which passes through the vaporized gas pipe 5 and is mainly used as fuel.

Moreover, the seawater is cooled by heat exchange with the liquefied gas, and ice crystals 7 are generated in the irrigation water. Note that the seawater level is indicated by 8. The ice crystals and brine in the crystallization tank 1 are removed by the flow control valve 1゛0.
, passes through the ice crystal and brine pipe 11, and passes through the separation/washing tower 12.
to go into. The flow rate adjustment valve 10 detects the seawater level 8 by a liquid level sensor 9 provided in the crystallization tank 1, and is operated by a command from the liquid level sensor 9 to maintain the seawater level at a constant level. There is. The ice crystals and brine that flow into the separation/washing tower 7 are separated into ice crystals and brine in the separation section 13 provided in the tower 11, and the ice crystals form an ice crystal layer 14 and rise inside the tower. [7. At the height of the ice crystal layer 14 where liquid removal is sufficiently performed, it is washed by the washing water 16 sprayed from the washing water nozzle 15, scraped off by the scraper 17, and enters the melting section 18. A heat exchanger using seawater or the like as a heat source is installed in the melting section 18, and the ice crystals melt to become fresh water. This fresh water is discharged through the fresh water pipe 20 and the fresh water flow rate regulating valve 21, and is used as drinking water or industrial water. Further, the freshwater flow rate regulating valve 21 is operated depending on the liquid level in the melting section 18. A portion of the fresh water flowing through the pipe 20 passes through some fresh water pipes 22, 24 and the fresh water pump 23, and is sprayed onto the upper part of the ice crystal layer 14 from the cleaning water nozzle 15.

On the other hand, the brine 25 separated from the ice crystals in the separation section 13 passes through the separated brine pipe 26, the separated brine circulation pipe 27, the brine circulation pump 28, and the circulating brine inflow pipe 29 to the crystallization tank 1. to go into. Here, a portion of the brine is also discharged to the outside through the brine/discharge line 30.

Further, the vent pipe line 31 is provided to connect the space of the separation section 13 and the space at the top of the column, and to balance the pressure in the compartment.

Further, the downstream end of the circulating brine inflow pipe 29 may be a single ejection pipe or a plurality of ejection pipes, and its structure is not particularly limited.

In the seawater desalination apparatus using direct contact between liquefied gas and seawater configured as described below, the present invention includes a brine circulation valve 28 in order to properly stir the seawater around the liquefied gas vaporizer 2. The circulating brine from the pipe 29
The liquefied gas is ejected near the side of the lower end of the vaporizer 2,
This prevents the surrounding area from being properly cooled and ensures a good crystallization operation.

Next, FIG. 2 is a system diagram showing a specific example of performing a crystallization operation in a pressure range in which . -30 have the same meaning as in FIG. 1, -32 indicates a no-hydrate decomposition tank, and 33 indicates an ice crystal slurry pump. In this case, an idrate decomposition tank (usually multi-stage type) 2 is installed between the crystal phase tank 1 and the separation/cleaning tower, and after converting the idrate into ice crystal nuclei, the ice crystal slurry bong 33 is The ice crystal slurry is sent to the separation/cleaning tower 12 through the
The separation and washing operations in the washing tower 12 are carried out downstream of the atmosphere, and the rest can be carried out using the same system as shown in FIG.

As described above, according to the present invention, it is possible to provide a crystallization tank that is easy to install and can efficiently desalinate seawater using a stirring method that does not require power costs.

[Brief explanation of drawings]

Figure 1 is a system diagram showing a specific example in which the crystal phase operation is performed within a pressure range in which no hydrate is produced and only ice crystals are precipitated using the 41i tank for desalination of frozen water of the present invention. FIG. 2 is a system diagram showing a specific example of performing a crystallization operation in the lower range where idlate is precipitated using the frozen seawater desalination crystallization tank of the present invention.

Claims (1)

[Claims] 1. In a refrigerated seawater desalination system that uses direct contact between liquefied gas and seawater, one or more recirculation brine ejection pipes are installed near the bottom side of the liquefied gas vaporizer provided in the crystallization tank. A frozen seawater desalination crystallization tank characterized by the following.