JP2007275821A - Evaporation concentrator for aqueous solution - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the crystallization or freezing of an aqueous solution in the bottom of the evaporation can on stopping of boiling or evaporation in an evaporation concentrator which has a heating mechanism 2 for evaporation heating an aqueous solution crystallizing or freezing on a decrease of the temperature, an evaporation can 1 boiling or evaporating, within the can, the aqueous solution having been heated by the heating mechanism, a condenser 10 condensing the steam generated in the can, and a circulating conduit 6 circulating the aqueous solution accumulated in the bottom of the evaporation can after the evaporation so as to return to the evaporation can through the heating mechanism. <P>SOLUTION: A heater 15 which raises the temperature of the aqueous solution accumulated in the bottom of the evaporation can 1 at least on a stop of the boiling or evaporation in the evaporation can is arranged in the part 4 of the bottom of the evaporation can where aqueous solution is accumulated. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is, for example, an aqueous solution having a property that crystals are precipitated when the temperature is lowered, such as semiconductor factory waste water containing ammonium sulfate (ammonium sulfate), or TMAH (tetramethylammonium hydroxide containing a pigment and a resist). This relates to an apparatus for concentrating by evaporation an aqueous solution having the property of solidifying as the temperature drops, such as waste water.

Conventionally, when evaporating and concentrating an aqueous solution having a property of crystallizing or solidifying at a low temperature as described above, for example, as described in Patent Document 1 and the like, a heating means for heating the aqueous solution, An evaporator that boils and evaporates the heated aqueous solution inside, and a condenser that condenses the water vapor generated in the evaporator, and further, the evaporated aqueous solution at the bottom of the evaporator is evaporated through the heating means. An evaporating and concentrating device having a circulation line that circulates back to the top of the can is used.
JP 2005-270902 A

  However, in the evaporative concentrator having this configuration, when boiling / evaporation in the evaporator is stopped, the concentrated aqueous solution is concentrated at the bottom of the evaporator, and this high concentration is accumulated. Since the aqueous solution is cooled and crystallizes or solidifies, it will not only seriously hinder the next operation of boiling / evaporation, but may cause damage to the equipment. Next, when boiling / evaporation is started, there is a problem that it takes a long time to heat the aqueous solution up to a predetermined boiling / evaporating temperature.

  Moreover, as described above, when the aqueous solution is a TMAH waste water containing a pigment or the like, since the aqueous solution has a foaming property due to high viscosity at the same time, as in the conventional apparatus described above, From the beginning of boiling / evaporation, the aqueous solution at the bottom of the evaporator is supplied to the heating means for boiling evaporation, heated to a temperature at which the boiling / evaporation is performed in the heating means, and then heated in the evaporator. When it is configured to circulate between the evaporator and the heating means, such as boiling and evaporating, foaming of the aqueous solution occurs in the evaporator and not only significantly hinders boiling and evaporation of the aqueous solution, In some cases, there was a problem of making the concentration operation impossible.

  This invention makes it a technical subject to provide the evaporative concentration apparatus which eliminated these problems.

In order to achieve this technical problem, claim 1 of the present invention provides:
“Evaporation heating means for heating an aqueous solution that has the property that crystals precipitate or solidify when the temperature drops, an evaporator that boils and evaporates the aqueous solution heated by this evaporation heating means, A condenser for condensing the generated water vapor, and further comprising a circulation line for circulating the evaporated aqueous solution accumulated at the bottom of the evaporator to return it to the evaporator through the heating means for evaporation. In evaporative concentration equipment,
A heater is provided in a portion where the aqueous solution is stored at the bottom of the evaporator, so that the temperature of the aqueous solution stored in the portion is increased at least when boiling and evaporation in the evaporator is stopped. "
It is characterized by that.

Claim 2 of the present invention includes:
“In the description of claim 1, the heater is an indirect heat exchange type heater.”
It is characterized by that.

Claim 3 of the present invention provides:
“In the method of claim 1 or 2, when the aqueous solution is circulated through the circulation line, when the boiling / evaporation in the evaporator is stopped, the heating means is provided from the portion where the aqueous solution is accumulated at the bottom of the evaporator. Then, the circulation is switched from the return to the evaporator for evaporation to the circulation to return directly to the evaporator without passing through the evaporation heating means from the portion where the aqueous solution is accumulated at the bottom of the evaporator.
It is characterized by that.

Claim 3 of the present invention provides:
“In the description of any one of claims 1 to 3, the boiling and evaporation in the evaporator is related to the water surface in the receiving tank provided in the aqueous solution supply pipe to the evaporation concentrator. It was configured to stop when the value was low. "
It is characterized by that.

  As described above, a heater is provided at the bottom of the evaporator where the aqueous solution is stored so that the temperature of the aqueous solution stored in the part is raised at least when boiling and evaporation in the evaporator are stopped. With this configuration, when boiling / evaporation in the evaporator is stopped, a high-concentration aqueous solution that accumulates at the bottom of the evaporator can be heated to the temperature at the boiling / evaporation by heating with the heater. Since it can be maintained at a temperature close to the bottom of the evaporator, it is possible to reliably prevent the high-concentration aqueous solution from crystallizing or solidifying due to a decrease in temperature, and boiling in the evaporator. At the start of evaporation, the time required for heating the aqueous solution up to the boiling / evaporating temperature can be greatly reduced.

  In addition, a heater is provided at the bottom of the evaporator where the aqueous solution is stored so that the temperature of the aqueous solution stored in the part is increased at least when the boiling / evaporation in the evaporator is stopped. Thus, prior to the start of boiling / evaporation in the evaporator, the aqueous solution in the evaporator is not sent to the heating means for boiling / evaporating, and the temperature at the time of boiling / evaporation is measured by the heater. Or since it can be heated up to a temperature close to this, it is possible to reliably suppress the foaming of the aqueous solution in the evaporator.

  Furthermore, the heating of the aqueous solution by the heater at the bottom of the evaporator is performed at least when the boiling / evaporation in the evaporator is stopped. By performing even in the performed state, boiling / evaporation in the evaporator can be further promoted, so that the evaporation ability can be improved.

  In this case, the heater at the bottom of the evaporator is an indirect heat exchange type heater as described in claim 2, so that the aqueous solution can be heated directly by blowing steam as a heating source. Compared to the case where it is performed, there is an advantage that the concentration in the aqueous solution does not change so as to decrease.

  In particular, according to the configuration described in claim 3, the aqueous solution heated by the heater is switched to a circulation in which the aqueous solution is directly returned to the evaporator from the bottom of the evaporator without passing through the heating means for evaporation. Because it can be heated uniformly in each place and the heating can be greatly accelerated, the crystallization or solidification can be more reliably prevented under the condition that the occurrence of foaming is suppressed. In addition, there is an advantage that the time required for raising the aqueous solution to the boiling / evaporation temperature at the start of the boiling / evaporation can be further shortened.

  Moreover, according to the structure described in Claim 4, there exists an advantage which can stop and start the boiling and evaporation in an evaporator according to the quantity of the aqueous solution stored in a receiving tank.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows a first embodiment.

  This first embodiment shows an evaporation apparatus in which an ammonium sulfate (ammonium sulfate) aqueous solution having a concentration of 0.116 wt% is concentrated to a high concentration of 30.0 wt%.

  In FIG. 1, reference numeral 1 denotes a hermetically sealed evaporator, and at the upper part in the evaporator 1 is provided a heating means 2 for evaporation formed by bundling a plurality of heat transfer tubes 2a extending in the horizontal direction. On the other hand, a reservoir 4 is provided at the bottom of the evaporator 1 so as to store an appropriate amount of the aqueous solution supplied into the evaporator 1 from the aqueous solution supply line 3.

  The aqueous solution in the reservoir 4 is pumped out by a circulation pump 5 and supplied to a nozzle 7 provided at the top of the evaporator 1 through a circulation pipe 6, and the evaporation heating means 2 is supplied from the nozzle 7. After being sprayed on the outer surface of each heat transfer tube 2a in the above, the circulation is performed so as to return to the reservoir 4 at the bottom of the evaporator 1.

  The steam generated in the evaporator 1 is once introduced into a sealed mist separation tank 9, and then driven by high-pressure steam supplied from a steam supply line 8 with a control valve 8a from a boiler or the like. Each of the heat transfer tubes is sucked and compressed by the steam ejector 10 and the steam compressed by the steam ejector 10 is introduced into each heat transfer tube 2a of the heating means 2 for evaporation as a heating source. The aqueous solution on the outer surface of 2a is heated to boil and evaporate.

  A part of the water vapor in each heat transfer tube 2a of the evaporating heating means 2 is sent to the water-cooled or air-cooled condenser 11 together with the non-condensable gas, where it is condensed and at the bottom thereof. In the condensate water storage chamber 12, the condensate water in the heat transfer tubes 2 a of the evaporating heating means 2 is stored together and then discharged by the pump 13, while the condenser 11 contains noncondensable gas. A vacuum generating source such as a vacuum pump 14 is connected to keep the inside of the evaporator 1 at a pressure lower than atmospheric pressure by extraction.

  The reservoir 4 at the bottom of the evaporator 1 is provided with an indirect heat exchange type heater 15 for heating the aqueous solution in the reservoir 4, and the steam supply pipe is connected to the heater 15. The high-pressure steam in 8 is supplied as a heating source through the steam line 16 with the control valve 16a, whereby the aqueous solution in the reservoir 4 is indirectly heated.

  In this configuration, the aqueous solution sprayed from the nozzle 7 in the upper part of the evaporator 1 is heated and brought to the boil / evaporation while in contact with the outer surface of each heat transfer tube 2a in the heating means 2 for evaporation in the middle of its flow. Then, the concentration increases and collects in the reservoir 4 at the bottom, and is sprayed from the nozzle 7 at the upper portion of the evaporator 1 from the reservoir 4 while being boiled / evaporated in the evaporator 1. After the aqueous mist is separated in the mist separation tank 9, the water vapor generated in is sucked and compressed by the steam ejector 9, and in each heat transfer tube 2a in the heating means 2 for evaporation, the heat transfer tubes 2a It is introduced as a heat source for the aqueous solution on the outer surface, and is further led from each heat transfer tube 2a to the condenser 10 where it is condensed.

  The aqueous solution from which the vapor is separated in the mist separation tank 9 is returned to the evaporator 1 via the U-shaped tube 17.

  Then, the boiling / evaporation in the evaporator 1 is stopped, the supply of the aqueous solution from the aqueous solution supply line 3 into the evaporator 1 is stopped, and the high pressure from the vapor supply line 8 to the vapor ejector 9 is stopped. When the supply of steam is stopped by closing the control valve 8a and stopping the circulation of the aqueous solution by the circulation pump 5, the concentration in the reservoir 4 at the bottom of the evaporator 1 is increased by boiling and evaporation. The aqueous solution having a high concentration accumulates. By heating the aqueous solution having a high concentration by the heater 15 provided in the reservoir portion 4, the aqueous solution having the high concentration is heated to the temperature at the time of boiling or evaporation, or Since it can be maintained at a temperature close to this, at the bottom of the evaporator 1, it is possible to reliably prevent the aqueous solution having a high concentration from crystallizing so that ammonium sulfate crystals are precipitated. Can together, at the start of boiling and evaporation in the evaporator within 1, aqueous solution, can greatly reduce the time required for heating increased to a temperature of the boiling and evaporation.

  Further, the aqueous solution at the bottom of the evaporator 1 can be heated up to the boiling / evaporation temperature by indirect heating of the heater 15 without supplying it to the heating means 2 for evaporation. Generation | occurrence | production of foaming of aqueous solution in the evaporator 1 can be suppressed.

  Incidentally, the heating by the heater 15 may be performed at least when the boiling / evaporation in the evaporator 1 is stopped, but the heating by the heater 15 is performed during the boiling / evaporation described above. By configuring so as to also perform the above, the evaporation capacity can be improved.

  Next, FIG. 2 shows a second embodiment.

  In the second embodiment, when the TMAH waste water is concentrated 10 times, the aqueous solution in the reservoir 4 at the bottom of the evaporator 1 is heated as in the first embodiment. This is a case where a direct heating type heater is used instead of using the heat exchange type heater 15.

  That is, a steam injection nozzle 15 ′ for direct heating is provided in the pool portion 4, and high pressure steam in the steam supply pipe 8 is ejected from the steam spray nozzle 15 ′, so that the interior of the pool portion 4 is obtained. The aqueous solution is configured to be directly heated, and the other configurations are the same as those in the first embodiment.

  When the aqueous solution in the reservoir 4 is indirectly heated as in the first embodiment, there is an advantage that the concentration of the aqueous solution does not change. On the other hand, when the aqueous solution in the reservoir 4 is directly heated as in the second embodiment, the concentration in the aqueous solution changes, but indirectly the heat exchange as in the former. There is an advantage that no scale adheres to the heat transfer surface.

  By the way, the above-mentioned TMAH waste water is a waste water containing about 1.4 wt% of TMAH and about 0.9 wt% of pigment and resist, and the rest is water, and at a temperature of about 20 ° C. before concentration. It was dark green, the viscosity measured with a rotational viscometer was 1.80 cp, and no adhesion to the glass surface was observed.

  However, the wastewater obtained by concentrating this 10 times is separated into two layers of dark green and dark brown in a stationary state, the viscosity measured by a rotational viscometer at about 60 ° C. is 0.80 cp, and the glass surface. Adhesion to was observed.

  That is, when the TMAH wastewater is concentrated 10 times, the temperature of the aqueous solution in the reservoir 4 at the bottom of the evaporator 1 is set to about 60 ° C., so that the viscosity is hindered from evaporating operation. In addition, since direct heating is performed by ejecting high-pressure steam from the steam injection nozzle 15 ', no heat transfer surface is provided, and therefore, scale adhesion can be reliably avoided. be able to.

  Next, in order to increase the temperature from 20 ° C. to 65 ° C. by setting the aqueous solution in the reservoir 4 at the bottom of the evaporator 1 to 1200 kg, if the specific heat is 1, 1200 × (65-20) × A heat quantity of 1 = 54000 kcal is required. On the other hand, if the total weight of the evaporator 1 including the heating means 2 and the reservoir 4 is 10000 kg, and the specific heat of the constituent material is 0.1, to raise the temperature from 20 ° C. to 65 ° C., 10000 X (65-20) * 0.1 = 45000 kcal of heat is required.

  In order to perform the above-described temperature rise exclusively by ejecting high-pressure steam from the steam injection nozzle 15 ', if the latent heat in the high-pressure steam is 560 kcal / kg, the amount of use of the high-pressure steam is ( 54000 + 45000) ÷ 560 = 177 kg. That is, a predetermined evaporation operation can be started by ejecting 177 kg of high-pressure steam from the steam injection nozzle 15 '.

  Next, FIG. 2 shows a third embodiment.

  In the third embodiment, in addition to the configuration of the first or second embodiment, a receiving tank 18 having a water level gauge 18 a is provided in the middle of the aqueous solution supply pipe 3 to the evaporator 1. When the amount of the aqueous solution accumulated in the receiving tank 18 is higher than a predetermined value, the controller 19 automatically opens the valve 3a in the aqueous solution supply line 3 to evaporate. The supply of the aqueous solution to the can 1 is started, the circulation pump 5 is automatically started to perform a predetermined circulation, and the control valve 8a in the steam supply line 8 is automatically opened. By starting the supply of high-pressure steam to the steam ejector 10, the above-described operation of boiling / evaporating the aqueous solution is performed.

  When the water level in the receiving tank 18 is lowered due to the progress of the evaporation operation and the amount of the accumulated aqueous solution is less than a predetermined value, the controller 19 causes the valve 3a in the aqueous solution supply line 3 and the In addition to automatically closing the control valve 8a in the steam supply line 8 to stop the boiling / evaporation of the aqueous solution, the circulation line 6 is further operated under the state where the circulation pump 5 is driven. The valve 6a is automatically closed while the valve 20a in the bypass circulation line 20 that directly connects the circulation line 6 and the evaporator 1 is automatically opened. A configuration in which the aqueous solution in the reservoir 4 is automatically switched from circulation returning to the evaporator 1 via the heating means 2 to circulation returning directly to the evaporator 1 without passing through the heating means 2. In addition, Vessel 15 or by opening the control valve 16a in the steam line 16 to the steam injection nozzle 15 'for heating, in which so as to heat the aqueous solution at reservoir 4 at the bottom of the evaporator 1.

  Note that the control valve 16a in the steam line 16 may be opened during both operation and stoppage.

  In the third embodiment, the boiling / evaporation of the aqueous solution in the evaporator 1 can be automated according to the amount of the aqueous solution stored in the receiving tank 18 because the boiling / evaporation can be stopped and started. In addition, when boiling / evaporation in the evaporator 1 is stopped, the aqueous solution heated by the heater 15 or the heating steam injection nozzle 15 ′ is exchanged from the bottom of the evaporator 1 through the heat exchange. Since the agitation can be carried out by circulation of returning directly to the evaporator 1 without passing through the vessel 2, the solidification can be more reliably prevented under the state where foaming is suppressed.

  In each of the above embodiments, the aqueous solution to be concentrated is a crystalline aqueous solution in which crystals are precipitated when the temperature is lowered, such as an ammonium sulfate (ammonium sulfate) aqueous solution. However, the present invention is not limited to this. Needless to say, the present invention can be similarly applied to an aqueous solution having a property of solidifying when the temperature is lowered.

It is a figure which shows 1st Embodiment in this invention. It is a figure which shows 2nd Embodiment in this invention. It is a figure which shows the 3rd Embodiment in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Evaporator 2 Evaporating heating means 2a Heat transfer tube in evaporating heating means 3 Aqueous solution supply line 4 Portion where aqueous solution accumulates 5 Circulating pump 6 Circulating line 7 Nozzle 8 Steam supply line 10 Steam ejector 11 Condenser 15 Indirect heat exchange Type heater 15 'Steam jet nozzle for heating 18 Receiving tank 18a Water level gauge

Claims (4)

Evaporation heating means for heating an aqueous solution that has the property of causing crystals to precipitate or solidify when the temperature falls, an evaporator that boils and evaporates the aqueous solution heated by this evaporation heating means, and generated in this evaporator An evaporator comprising a condenser for condensing the water vapor, and a circulation line for circulating the aqueous solution accumulated at the bottom of the evaporator to return it to the evaporator through the heating means for evaporation. In the concentrator,
A portion of the bottom of the evaporator where the aqueous solution is stored is provided with a heater that raises the temperature of the aqueous solution stored in the portion at least when boiling / evaporation in the evaporator is stopped. An evaporative concentration apparatus for an aqueous solution.   2. The aqueous solution evaporative concentration apparatus according to claim 1, wherein the heater is an indirect heat exchange type heater.   3. The evaporating heating means according to claim 1, wherein when the aqueous solution is circulated through the circulation line, when the boiling / evaporation is stopped in the evaporator, the aqueous solution accumulates at a bottom of the evaporator. It is configured to switch from the circulation of returning to the evaporator through the evaporator to the circulation of returning directly to the evaporator without passing through the heating means for evaporation from the portion where the aqueous solution accumulates at the bottom of the evaporator. Evaporative concentration device for aqueous solution.   In any one of the said Claims 1-3, the said water surface is related with the water surface in the receiving tank provided in the aqueous solution supply pipe line to the evaporation concentrator, and the said water surface is boiling and evaporation in the said evaporator. An apparatus for evaporating and concentrating an aqueous solution, which is configured to stop when it is lowered.

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