JP7597141B2 - Batch type concentrator - Google Patents

Description

The present invention relates to a batch-type concentration device that uses a reverse osmosis membrane device (RO device).

As a batch-type concentration device that batch-type concentrates water to be treated, Patent Document 1 describes a filtration treatment device in which multiple reverse osmosis membrane modules are connected in series, contaminated water in a contaminated water tank is passed through the reverse osmosis membrane modules in sequence, concentrated water from the final reverse osmosis membrane module is returned to the contaminated water tank, and permeated water from each reverse osmosis membrane module is taken out.

JP 2019-126767 A

When water is passed through membrane modules arranged in series at a high linear flow rate, the module differential pressure increases, and the effective pressure of the downstream module decreases. In other words, the water pressure of the water to be treated is higher in the upstream reverse osmosis module and lower in the downstream reverse osmosis membrane module. As a result, the membrane surface of the downstream reverse osmosis membrane module is more likely to become clogged with dirt, and the reduction in effective pressure leads to a decrease in the removal rate. In particular, when wastewater is concentrated in batches, the osmotic pressure of the wastewater increases as it is concentrated, so the effective pressure on the membrane when it reaches the concentration level is smaller than at the beginning of operation, and the reduction in effective pressure further reduces the removal rate. As a result, the quality of the permeate water deteriorates as it is concentrated.

In addition, when circulating wastewater containing high concentrations of suspended solids (SS), it is desirable to have a structure that prevents SS from remaining in the piping and valves (e.g., back pressure control valves).

The objective of the present invention is to provide a batch concentration device that can prevent clogging of the back pressure control valve for applying back pressure to the concentrated water line.

The gist of the present invention is as follows:

[1] A batch type concentration apparatus having a raw water tank, a reverse osmosis membrane device through which water in the raw water tank is passed, a concentrated water line that returns concentrated water from the reverse osmosis membrane device to the raw water tank, and a back pressure control valve provided on the concentrated water line,
a control valve for controlling the concentration of the concentrated water from the batchwise concentration of the water;

[2] A batch concentrator according to [1], having 2 to 5 stages of the orifices.

[3] A batch-type concentrator according to [1] or [2], in which the reverse osmosis membrane devices are arranged in series in 2 to 5 stages.

The batch type concentration apparatus of the present invention is provided with an orifice upstream of the valve installed in the concentrated water line, so that sufficient back pressure can be applied to the RO apparatus without excessively reducing the valve lift of the back pressure control valve. In this way, there is no need to excessively reduce the valve lift of the back pressure control valve, so clogging of the back pressure control valve is prevented. Although there is a method of suppressing excessively small valve lift by using multiple valves rather than providing a single stage valve, using an orifice can be considered as a valve with a 100% opening, so providing an orifice is preferable to providing multiple valves.

FIG. 2 is a flow diagram showing the configuration of a batch-type concentrating apparatus according to an embodiment.

The following describes the embodiment with reference to the drawings.

Raw water (water to be treated) is introduced into raw water tank 2 through pipe 1, and a predetermined amount of raw water is stored in raw water tank 2.

The water in the raw water tank 2 is pumped by pump 5 through piping 3 at the bottom, valve 4, and supplied to the first reverse osmosis membrane device (hereinafter sometimes referred to as RO device) 11 via valve 6 and piping 7.

The concentrated water from the first RO device is supplied to the second RO device 12 via pipe 11a, the concentrated water from the second RO device 12 is supplied to the third RO device 13 via pipe 12a, and the concentrated water from the third RO device 13 is supplied to the fourth RO device 14 via pipe 13a. The concentrated water from the fourth RO device 14 is sent to the raw water tank 2 via pipe 15, orifice 16, back pressure control valve 17, and pipe 18.

Various types of back pressure control valves, such as a piston type or a diaphragm type, can be used as the back pressure control valve 17. Although not shown in Fig. 1, pressure gauges can be installed between the concentrated water in the last stage of the RO device (the fourth RO device 14 in Fig. 1) and the orifice 16, and between the orifice 16 and the back pressure control valve 17, to manage the pressure or identify the location of blockage (either the orifice or the back pressure control valve).

In this embodiment, the orifices 16 are installed in two stages, but they may be installed in one stage or three stages or more (up to about five stages). If there are five stages or more, it becomes complicated to manage the pressure between the orifices, as read from the pressure gauge installed at the end of the reverse osmosis membrane and between the orifice and the control valve, so one to three stages are preferable. As the orifice, a commercially available orifice can be used, but it is not particularly limited as long as it has the function of narrowing the flow path. If the concentrated water contains suspended solids with a particle size exceeding 10 mm, an inflow prevention member such as punched metal may be provided.

The permeated water that has permeated the RO membranes of each of the RO devices 11 to 14 is introduced into the permeated water tank 21 via the permeated water pipes 11b, 12b, 13b, and 14b and the merging permeated water pipe 20. The permeated water in the permeated water tank 21 is removed via the valve 22 and pipe 23.

Pipe 8 branches off from pipe 3, and valve 9 is provided on pipe 8. Valve 9 is opened only when water (e.g., concentrated liquid) is discharged from raw water tank 2, and is otherwise closed.

Reverse osmosis membranes can be made of any of the following materials: cellulose acetate, aromatic polyamide, polyacrylonitrile, and composite membranes. However, when the raw water contains oil or surfactants, cellulose acetate is preferable. Reverse osmosis membrane modules can be of any type: tubular, disk, flat membrane, hollow fiber, and spiral. Examples of reverse osmosis membranes that can be set to a high membrane linear flow rate include tubular and disk types.

In this batch type concentration apparatus, after a predetermined amount of raw water is stored in the raw water tank 2, valves 4 and 6 are opened and pump 5 is operated. The water in the raw water tank 2 is passed through pipes 3 and 7 in order to the first to fourth RO devices 11 to 14, and concentrated water from the fourth RO device 14 is returned to the raw water tank 2 through pipe 15, orifice 16, back pressure control valve 17, and pipe 18. The permeated water is taken out to the permeated water pipes 11b to 14b, 20 and the permeated water tank 21.

In this embodiment, since the orifice 16 is provided, sufficient back pressure can be applied to each of the RO devices 11 to 14, including the RO device 14, without excessively reducing the valve lift of the back pressure control valve 17. This makes it possible to prevent the back pressure control valve 17 from becoming clogged.

In the present invention, there is no particular limitation on the raw water to be treated. The present invention can also treat wastewater that was difficult to treat using conventional batch-type concentrators, such as CMP slurry wastewater and oil-containing wastewater.

In the present invention, RO concentrated water can be sufficiently treated even when the surfactant concentration is 1500 mg/L or more, the SS concentration is 14000 mg/L or more, and the CODmn concentration is 10000 mg/L or more.

2 raw water tank 11-14 reverse osmosis membrane device 16 orifice 17 back pressure control valve 21 permeated water tank

Claims (3)

A batch type concentration apparatus having a raw water tank into which raw water is introduced , a reverse osmosis membrane device through which water in the raw water tank is passed, a concentrated water line for returning concentrated water from the reverse osmosis membrane device to the raw water tank, and a back pressure control valve provided on the concentrated water line,
The raw water is a CMP slurry wastewater or an oil-containing wastewater,
A batch type concentration apparatus having an orifice installed on the concentrated water line upstream of the back pressure control valve,
a pressure gauge disposed in the concentrated water line for returning concentrated water from the reverse osmosis membrane device to the raw water tank, between the reverse osmosis membrane device and the orifice, and between the orifice and the back pressure control valve . The batch concentrator of claim 1, in which the orifices are provided in 2 to 5 stages. The batch concentrator of claim 1 or 2, in which the reverse osmosis membrane devices are installed in series in 2 to 5 stages.

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