JPH0615102A - Falling film type concentrator - Google Patents

Abstract

PURPOSE:To allow liquid to flow down with centrifugal turning while making the optimum liquid quantity matched with the quality of the liquid tight adhesive to the inner surface of a heat transfer tube by providing vertical slits on a distribution tube connected to the heat transfer tube and providing feeding liquid introducing parts over the total length of the slits along a tangential direction. CONSTITUTION:A distribution tube 1 is connected to a heat transfer tube 5 by inserting an insert part 2 into the heat transfer tube 5 extending in the extending direction of the distribution tube 1. Plural vertical slits A are provided on the wall surface of the distribution tube 1 and the lower end B of each slit A is provided on the level or above of a lower end C of the distribution tube 1, that is, the inlet of the heat transfer tube and the lower end B and an upper end T of each slit are at the substantially the same levels, respectively. Also feeding liquid introducing parts 3 opened over the total length of the slit A and along the tangential direction of the distribution tube 1 are provided. Feeding liquid is introduced into the heat transfer tube 5, with centrifugal turning force given by the feeding liquid introducing parts 3 and flows down under a cylindrical turning while bringing the liquid into tight adhesion to the inner wall surface of each heat transfer tube.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self vapor compression falling film type concentrator equipped with a special feed liquid distribution pipe.

[0002]

2. Description of the Related Art Thermal power plants in Japan and the wet flue gas desulfurization equipment attached to them are usually located at seaside, and the wastewater is discharged to the public sea area while devising and improving the efficient removal method of each target component in the wastewater. ing. On the other hand, the fuel coal in the power plant depends on overseas coal, and the quality of the coal is deteriorating, so the amount of wastewater per amount of exhaust gas tends to increase, and the amount of wastewater also increases from the perspective of scaling up the capacity of the single unit power plant. There is.

Further, in the treated flue gas after cleaning and desulfurization, water corresponding to the partial pressure of the absorbing liquid at that temperature is discharged out of the system as one component of the treated flue gas, and a huge amount for replenishing this moisture. Make-up water is required. And, the rational water saving of the entire power plant including drainage water and makeup water has been achieved.

[0004]

The problem to be solved by the present invention is to further thoroughly implement rational water saving of the entire thermal power plant and to evaporate the waste water to dryness (recover the evaporated water). An object of the present invention is to provide a concentrating device for evaporating and concentrating the waste water as a waste.

[0005]

A falling film type concentrator according to the present invention is provided with a distribution pipe standing in a supply liquid tank, and a plurality of vertical slits are formed in the distribution pipe, and each lower end of the slit is formed. And the upper end are at substantially the same horizontal level,
A supply liquid introducing portion opened along the tangential direction of the distribution pipe over the entire length of the slit is provided, and a lower end of the distribution pipe is connected to a heat transfer tube extending in an extension direction of the distribution pipe. An embodiment of the falling film type concentrating device of the present invention will be described below with reference to the drawings.

[0006]

EXAMPLES First, the reason why a falling film type apparatus is used as the apparatus of the present invention will be described. The liquid to be concentrated in the device of the present invention, that is, the liquid supplied to the device of the present invention is, for example, a contact cleaning liquid for flue gas in a wet flue gas desulfurization device.

Therefore, the feed liquid contains solid fine particles mainly composed of gypsum, and also contains salts that crystallize from the feed liquid upon concentration, and has a high scaling tendency, and seed crystals of the precipitate prevent scaling. Is added in advance. On the other hand, it is also highly corrosive and abrasive. As a model of the evaporative concentrating device for the liquid having such a property, an external heat type concentrating device, of which a self-vapor compression type falling film type is naturally suitable from the viewpoint of using a corrosion resistant material. The rationale is as follows.

(A) In the self-vapor compression type, the increase in temperature on the heated side due to the liquid deep pressure and the increase in boiling point increases the compression power, so that energy saving is not achieved. Therefore, a falling film type having a small liquid pressure is preferable. (B) The equipment is compact, and there are few wetted parts that use corrosion-resistant (corrosion, corrosion) materials.

(C) The temperature difference between the inside and the outside of the heat transfer element is too high, and salt precipitation due to the concentration rate causes seed crystal concentration in the feed liquid,
There is a suspicion that scale will be generated if it is in balance with the amount of the supplied liquid and the falling liquid is not mixed well. (D) If the supply of the supply liquid is stopped, the inside of the pipe will be empty, eliminating scale troubles and other good maintainability.

In FIG. 1, the heat transfer tube 5 of the falling film type concentrating device usually has an inner diameter of about 50 mm, and the distribution pipe 1 has a heat transfer tube 5 extending in the extension direction of the distribution pipe 1 at its insertion portion 2. For example, although it is inserted and connected to the inner pipe of the indirect heat exchanger, the insertion depth of this insertion portion 2 is determined so that the verticality of the distribution pipe 1 can be maintained and fixed. As is apparent from FIG. 1, the distribution pipe 1 in the insertion portion 2
Is smaller than the diameter of the heat transfer tube 5.

Next, according to the present invention, the liquid supplied to the heat transfer tube 5 is smoothly flown down while centrifugally rotating.
That is, a plurality of vertical slits A are provided on the wall surface of the distribution pipe 1, and the lower end B of each slit A is at the lower end C of the distribution pipe 1, that is, at the inlet level of the heat transfer pipe 5 or higher, and The lower end and the upper end of the slit A are substantially at the same horizontal level, and in the case of FIG. 1, the lower end B of the slit A is almost at the same level as the surface of the tube sheet 4, so that the solid particles in the supply liquid are It is adapted to be introduced into the heat transfer tube 5 through the slit A.

The height of the slit A shown by the lower end B and the upper end T in FIG. 1 is usually 50 mm to 150 mm, preferably about 100 mm, and the width of the slit A is set to 3.0 mm to 5.0 mm. Further, as shown in FIGS. 1 and 2, each slit A is provided with a supply liquid introducing portion 3 which is opened along the entire length of the slit A and along the tangential direction of the heat transfer tube 1. A centrifugal swirling force is applied and introduced into the heat transfer tubes 5, and they are brought into close contact with the inner wall surface of each heat transfer tube to cause the swirling flow of the supply liquid in a cylindrical shape.

Although the number of slits A is four in this embodiment as shown in FIG. 2, it is not limited to this and may be five or more. Although the top of the distribution pipe 1 can be used both in the case of being closed and in the case of being opened, in the case of a feed liquid having a scaling property, it is closed, and the distribution pipe 1 is immersed in the feed liquid and the slit A It is desirable to design the liquid load per heat transfer tube 5 to be optimal by a combination of the height and the normal operating immersion liquid depth.

As the heat transfer tube 5, a high-grade metal of Ti, Ni-Cr system, glass tube, glass lining tube or the like is usually used, so that the distribution pipe 1 is also the same or similar material, ceramic material, It can be made of silicon carbide casting, and FRP containing wear resistant material and rubber made of wear resistant material can also be applied. Further, in this example, the supply liquid is mainly intended for the wastewater of the wet flue gas desulfurization device, but the wastewater discharged from various places such as A / H, wet EP, GGH, etc. as the supply liquid may also be the target. it can.

Furthermore, when the mixed liquid containing the waste water from the wet flue gas desulfurization apparatus is used as the supply liquid, either the ash separation system or the ash mixing system may be used, and the object is not particularly limited. is not. In the present invention, when the liquid to be concentrated is the above-mentioned waste water, the total dissolved salt amount is usually 30,000 to 80,000 ppmw.
In the case of the ash separation method, the pH is approximately 1 to 2; in the case of the ash mixing method, the pH is 4 to 5 and in both cases, 100 to 500 pp
It contains mw of suspension and the mainstream flue gas desulfurization equipment is limestone-
Since it is a gypsum method, most of the dissolved salts are calcium chloride, sulfate, magnesium sulfate, etc., and there are some saturated concentrations of calcium sulfate. To cause scaling, and cause deterioration of the overall heat transfer coefficient of the heat transfer tube 5. Therefore, in order to prevent this deterioration, seed crystals of salts that precipitate as scaling are added to the feed solution, and after the start, seed crystals that have precipitation surfaces of various growth rates or higher that are precipitated in proportion to the heating concentration are kept in the feed solution. , The salt that is deposited by concentration is deposited on the seed crystal surface to prevent deposition on the heating surface. The seed crystal concentration is usually 30 to 60 μm (average) × 3 to 10 WT%. The working temperature is 100-110 ℃, TDS of the concentrate is 30,
Since it reaches 000 to 40,000 and contains a lot of chlorides, fluorides, and nitrates, the distribution pipe 1 needs to be a material having sufficient wear resistance and corrosion resistance even under the above conditions.

Next, the operation of the falling film type concentrating device of the present invention will be described. In the concentrating device of the present invention, a plurality of vertical slits are formed in the distribution pipe as described above, and the supply liquid introducing portion opened along the tangential direction of the distribution pipe is provided over the entire length of the slit.
Therefore, the supply liquid (concentrated liquid) supplied from each slit
The centrifugal force is applied to the inner wall surface of the heat transfer tube, and the material flows in a cylindrical shape while swirling, so that the inner wall of the heat transfer tube has a fast downflow speed and a large overall heat transfer coefficient.

On the other hand, the liquid depth of the supply liquid on the inner wall of the heat transfer tube
The temperature rise due to (thickness) is small because the feed liquid is in the form of a relatively thin film, and the crystal amount of soluble salts in the feed liquid that precipitates with this small evaporative concentration rate is less than the amount of seed crystal precipitation in the feed liquid Become. The temperature difference between the inner and outer tubes of the heat transfer tube is
It is controlled by adjusting the self-evaporating compression pressure and the feed liquid flow rate. The supply liquid flow rate is from the circulating liquid tank 55 (Fig. 4) to the circulating pump.
This can be performed by adjusting the supply liquid depth in the liquid supply tank 52 according to the flow rate of the liquid supplied to the liquid supply tank 52. As a result, stable and efficient concentration without scaling becomes possible.

Next, FIG. 3 is a system diagram showing an example of flue gas desulfurization wastewater concentration equipment using the falling film type concentration equipment of the present invention. This equipment compresses vapor generated by concentration and A vapor-compressor-type vapor-liquid co-current double-effect can 21 that co-flows with the liquid to be concentrated is used, and the distribution pipe 1 in the device of the present invention is attached to the inlet of the heat transfer pipe 5 of the concentrating can 21.

In FIG. 3, desulfurization drainage 11 is a slaked lime aqueous solution.
After being mixed and stirred in the 12 and the neutralization tank 24 to be neutralized, it is sent to the plate heat exchanger 26 by the neutralization liquid supply pump 25 and heated, and the heated neutralization wastewater 13 is degassed by the vacuum generator 28. Is introduced into the degassing tank 27. The degassing drainage 14 is a circulating fluid pump.
As a supply liquid to be concentrated by 23, via a pipe 15,
It is supplied to the supply liquid tank 19 provided at the top of the.

On the other hand, the vapor generated by the concentration of the supply liquid is supplied by the vapor compression pump 22 to the outer tube side of the concentrating can 21 via the pipe line 16 and indirectly with the supply liquid swirling down the heat transfer tube 5. While heat exchange, they flow down together, the feed liquid and its evaporation vapor flow downward, and flow down into the circulating liquid tank 32. The separated vapor is removed by a eliminator 33 provided at the top of the circulating liquid tank 32 to remove mist and then pressurized by a compressor 22 to be guided to the outer side of the concentrating tube 21 to be used as a heat source for the inner tube 5. The condensed water is taken out from the lower part of the concentrating pipe 21, and is used as condensed recovered water 18 from the condensed water receiving tank 29 by the condensed water transfer pump 30 to exchange heat with the plate heat exchanger 26.

Next, FIG. 4 is a schematic cross-sectional side view of the layout of the test equipment which was tested by the inventors of the present invention.
0ppmw, MgSO ₄ concentration 3wt%, calcium salt concentration CaC
Fig. 4 shows a liquid 41 to which about 5% by weight (40 µm average) of gypsum seed crystals was added after adjusting the pH of the slaked lime slurry to a drainage slurry of l ₂ , CaSO ₄・ 2H ₂ O 2 wt% to 5 = 7 in advance. In the inner tube of the indirect heat exchanger consisting of the inner tube 53 made of titanium with a diameter of 50 mm and the jacket pipe 54 of 1.5 m, through the vertical slit A, the peripheral length of the inner tube is 1000 L to 2000 L per 1 m.
It was supplied at a flow rate of / hour, and concentrated by circulation.

The jacket pipe 54 side is heated by steam, and the pressure difference between the inner pipe 53 and the jacket pipe 54 is 0.15 kg.
Although the concentration was controlled by controlling to / cm ² , SU was added to the distribution pipe 51.
The test was performed by mounting the S317L product in the top liquid tank 52. As a result, it was confirmed visually through the observation window 52A at the top that the distribution pipe 51 flows down while the centrifugal swirling downward flow of the supply liquid is formed in the inner pipe 53 while forming a cylindrical shape.
It was confirmed that the supply liquid was brought into close contact with the inner surface of the inner tube 53 and was centrifugally swirled down without being separated by appropriately adjusting the immersion depth of the slit.

Also, the boiling point of the concentrated liquid as a result of the test is 3
It was confirmed that the total heat transfer coefficient was about 2400 kcal / m ² .H ℃, and the concentration was good. In addition, in FIG.
Is a circulating liquid tank, 56 is a circulation pump, 57 is a magnetic flow rate indicating controller, 58 is a steam pressure indicating controller, 59 is a steam discharge pipe, 42 is steam, 43 is evaporative vapor, 44 is condensed water, 45
Indicates water, and 46 indicates a steam trap.

[0024]

According to the falling film type concentrating device of the present invention described above, a vertical slit is formed in the distribution pipe, and the feed liquid introducing portion is provided along the tangential direction of the distribution pipe over the entire length of this slit. Since it is provided, regardless of the nature of the concentrated feed liquid, for example, the type of desulfurization equipment,
Dispersion of different amounts of calcium, calcium, and salt that precipitates with composition, solid concentration, and concentration depending on the type of fuel charcoal, calcium char powder, and makeup water is evenly distributed, and the optimum amount of liquid that matches the liquid quality is closely attached to the inner surface of the heat transfer tube and centrifuged. It can be swirled down. Furthermore, the flow velocity of the liquid is faster than a mere vertical flow, and there is no separation of the liquid from the wall surface of the heat transfer tube.Precipitation of calcium salt on the heat transfer surface due to heat transfer / concentration is prevented by the addition of seed crystals of the supply liquid. Therefore, the desulfurization effluent can be concentrated without causing scaling trouble.

On the other hand, it is economically desirable that the total dissolved salt concentration in the liquid after concentration of the desulfurization effluent by the apparatus of the present invention is up to 30.0 to 40.0% by weight, but the total dissolved salt concentration in the desulfurization effluent is usually 50,00%.
Since it is 0 to 60,000 ppmw, it can be concentrated about 6 times as much as before, and the device of the present invention is extremely effective as a pretreatment for desulfurization wastewater without drainage, and condensed water is used as makeup water for the desulfurization device. It also has the advantage that it can be reused.

The apparatus of the present invention is not limited to the treatment of the desulfurization wastewater, but is effectively applied to the concentration of a solution of a general chemical product for removing the solvent, particularly the concentration of a solution having a small heat resistance. can do.

[Brief description of drawings]

FIG. 1 is a side sectional view of an essential part showing an embodiment of a supply pipe in a falling film type concentrating device of the present invention.

FIG. 2 is a plan sectional view taken along line XX of FIG.

FIG. 3 is a system diagram showing an example of desulfurization wastewater concentration equipment using the concentration device of the present invention.

FIG. 4 is a schematic cross-sectional side view of the arrangement of test equipment that was tested by the present inventors.

[Explanation of symbols]

 1 minute piping 2 liquid supply inlet 5 heat transfer tube A slit B slit lower end T slit upper end

Claims (1)

[Claims] 1. A distribution pipe is provided upright in a supply liquid tank, a plurality of vertical slits are formed in the distribution pipe, and each lower end and upper end of the slit are set to substantially the same horizontal level, A falling film type concentrating device characterized in that a supply liquid introducing portion opened along the tangential direction of the distribution pipe is provided over the entire length, and the lower end of the distribution pipe is connected to a heat transfer tube extending in the extension direction of the distribution pipe. .