JP2006021119A - Fluid treatment method and fluid treatment system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluid treatment method capable of eliminating the problem of sludge, a malodor, or the like, caused by microorganisms in a fluid to be treated and the clogging of a separation membrane due to the sludge, and a fluid treatment system. <P>SOLUTION: High salt type wastewater the pollution degree, of which is less than that of desulfurization wastewater discharged from the absorbing column (1) of a coal steam power plant, is added to the desulfurization wastewater to dilute the same so that an index value showing the pollution degree of the desulfurization wastewater becomes a value for suppressing the growth of microorganisms. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fluid processing method and a fluid processing system for processing fluid for reuse or discharge.

  Coal and petroleum used as fuels in thermal power plants contain sulfur and nitrogen, so if these contents are high, there is a large amount of sulfur oxides and nitrogen oxides in the flue gas emitted during combustion. Will be included. Therefore, thermal power plants require equipment design that fully considers equipment corrosion and environmental protection. For example, flue gas generated during coal combustion is discharged from a chimney after removing nitrogen oxide, soot and sulfur oxide by a flue gas denitration device, an electric dust collector and a flue gas desulfurization device, respectively.

  As a desulfurization method for removing sulfur oxides, a method called wet lime gypsum method is widely used. This method removes soot and dust from the flue gas and then reacts the sulfur oxide in the flue gas with the limestone mixture. It is classified into two types: a suit separation type in which sulfur oxide is extracted as gypsum in the absorption tower and a suit mixing type in which dust removal and desulfurization are performed simultaneously in the absorption tower. In any desulfurization method, after the sulfur oxide in the flue gas and the limestone mixed liquid are reacted in the absorption tower, it is necessary to treat the desulfurized effluent, which is the waste liquid of the limestone mixed liquid, to a state in which it can be discharged. . Components to be treated in desulfurization effluent include suspended substances, heavy metals, fluorine, silica, calcium, magnesium, oxidizing substances, and reducing substances that are subject to water quality index values called chemical oxygen demand (COD) (for example, Sulfite ion or manganese ion). COD is represented by the amount of oxygen consumed when the organic matter in the desulfurization waste water is oxidized by an oxidizing agent.

  In conventional desulfurization wastewater treatment, treatment is performed in the flow of coagulation sedimentation, filtration, and adsorption of COD target substances. In the process of coagulation sedimentation and filtration, solid particles dispersed in the desulfurization wastewater are treated with a flocculant. After collecting and forming a larger aggregate (floc), it was allowed to stand still, allowed to settle naturally, and filtered through sand spread on the bottom, which required a very large facility space. .

  Accordingly, in recent years, treatment systems using solid-liquid separation membranes that can save space, save equipment, improve the quality of treated water, and significantly reduce the amount of chemicals used have become widespread. As this separation membrane, a microfiltration membrane (MF membrane) capable of capturing particles of several microns or more, suspended substances, and the like is widely used. Moreover, in a treatment system using a separation membrane, a flocculant or neutralizing agent is added to the desulfurization effluent and allowed to react sufficiently, and then this can be directly filtered through the separation membrane, so the treatment time required for solid-liquid separation The amount of chemicals used such as a flocculant and a neutralizing agent can be reduced to about 30% of the conventional amount.

  However, a processing system using a separation membrane has a problem that the membrane of the separation membrane becomes clogged as the operation time elapses. The clogging of the separation membrane reduces the capacity of the desulfurization wastewater, which may lead to a situation where the desulfurization wastewater that cannot be treated has to be temporarily stored in a multipurpose tank, etc. It is a serious problem.

  Conventionally, in order to eliminate clogging of separation membranes, so-called backwashing has been performed in which desulfurization waste water or industrial water is periodically flowed back to wash the sludge adhering to the separation membranes causing clogging. . If clogging is not resolved even by backwashing, backwashing using chemicals (hereinafter referred to as “medicine washing”) is performed. In general chemical washing, an alkaline solution or an acid solution may be used as a chemical, or these solutions may be used in combination. Specifically, when polyaluminum chloride (PAC), sulfated clay (band), magnesium hydroxide, ferric chloride, or slaked lime is used as a flocculant or neutralizer, it is generated when desulfurization wastewater is concentrated Since the suspended substance to be dissolved can be dissolved by an alkali or an acid, it is often washed with an alkali such as sodium hydroxide or an acid such as hydrochloric acid. In addition, sodium hydroxide is heated to a temperature necessary for dissolving silica (for example, 40 to 60 ° C.), and an acid is used at room temperature or appropriately heated to dissolve other metals. It is done. The washing waste liquid generated after the chemical washing is discharged after being treated separately. However, since chemicals may be mixed into the discharged water, it is necessary to keep the chemical washing frequency as low as possible in consideration of environmental conservation.

  Moreover, since the chemical washing of the separation membrane in a power plant requires a large cost, it is desired to reduce the frequency of chemical washing from the viewpoint of cost reduction. In one power plant, the cost required for chemical washing is a cleaning work fee, a chemical fee, and an industrial water fee used for flowing chemicals. Furthermore, the equipment cost and the chemical cost for processing the washing waste liquid after the chemical washing also have a large cost.

  As described above, there are various problems with chemical washing of the separation membrane. However, since there has been no method other than chemical washing that can eliminate clogging of the separation membrane, the separation membrane is clogged, and the reverse If the problem cannot be solved by washing, it is necessary to carry out chemical washing.

  Non-Patent Document 1 below describes a technique that can extend the life of a separation membrane by periodic backwashing and chemical washing once a month. FIG. 5 is a cross-sectional view of a tubular microfiltration membrane (MF membrane) used as a separation membrane in this technology. (A) is a state when filtering desulfurization wastewater, and (b) is during backwashing. Shows the state.

  In this technique, as shown in FIG. 5 (a), the desulfurization waste water flows through the tube-like MF membrane 51 at a constant flow rate, and a part of the desulfurization waste water flowing in the MF membrane 51 is filtered to remove the outside of the membrane. As a result, the sludge 52 is captured on the inner surface of the MF membrane, and the remaining waste water circulates in the system and flows into the MF membrane 51 again. This tubular MF membrane 51 has an advantage that the progress of sludge accumulation can be suppressed by flushing the sludge 52 accumulated on the inner surface of the membrane with desulfurization drainage with the passage of time.

  In this technique, backwashing of the MF membrane 51 is performed at intervals of 15 to 60 minutes. Specifically, as shown in FIG. 5B, desulfurization waste water or industrial water is supplied from the outside to the inside of the membrane. Then, the sludge 52 accumulated on the inner surface of the membrane is peeled off. On the other hand, if clogging is not resolved by backwashing, as a rule, chemical washing is performed once a month.

  In addition, in this document, in order to delay the progress of the clogging of the MF membrane 51, the suspended solids concentration for optimizing the particle size of the gypsum produced by adding slaked lime to the desulfurization wastewater and preventing the generation of sludge. In addition to stating that management is important, the life of the MF film 51 is extended by repeating regular backwashing and chemical washing.

Published by The Thermal Nuclear Power Technology Association, Journal “Thermal Nuclear Power Generation, December 1998”, Extending membrane life in wastewater treatment facilities (Hiroyuki Fujita, Yu Sasaki, Kiyohito Chikazawa, Moriyuki Hirota, Tadashi Takai, Takeshi Sato )

  However, according to the above technology, in order to extend the life of the MF membrane, it is essential to repeat the chemical washing at a frequency of about once a month. Considering the aspects of environmental conservation and cost, It is not a preferred method.

  On the other hand, as a result of various experiments and analyzes to clarify the cause of clogging of separation membranes, clogging of separation membranes occurs when desulfurization wastewater generated when burning low sulfur coal with low sulfur content It turns out to progress rapidly. As a result of further analysis based on this result, total organic carbon (TOC) and biochemical oxygen demand (BOD) representing the degree of pollution of desulfurization effluent generated when high sulfur coal with a high sulfur content is burned. ), Chemical oxygen demand (COD), total carbon content (TC), total nitrogen content (TN), and ammonia nitrogen are index values that inhibit the growth of microorganisms (for example, 10 ppm for TOC, BOD 20ppm for COD, 21ppm for COD, 38mgN / L for TN, and 38mgN / L for ammonia nitrogen), these values in the desulfurization effluent during low-sulfur coal combustion are values sufficient for the growth of microorganisms. (For example, TOC = 20 ppm).

TOC is the amount of carbon in the organic matter contained in the sample,
BOD is the oxygen consumption by microorganisms when the sample is kept at 20 ° C. and left in a sealed state for 5 days,
TC is the sum of total organic carbon content (TOC) and inorganic carbon content (IC) contained in the sample,
TN is the total amount of organic and inorganic (for example, ammonia, nitrite, and nitrate) nitrogen compounds contained in the sample,
And ammonia nitrogen is represented by the quantity of the said inorganic nitrogen compound of an ammonia state.

The amount low sulfur coal and high sulfur coal is defined is different for each plant, for example, equivalent to 0.4% of the sulfur content is SO ₂ concentration in the flue gas exiting during combustion contained in coal to be 300ppm Can be classified on the basis of.

Since the above results were obtained, chemical analysis of the desulfurization effluent during high-sulfur coal combustion and low-sulfur coal combustion showed almost no microorganisms in the desulfurization effluent during high-sulfur coal combustion. However, explosive growth of microorganisms (for example, 30,000 cells / mm ³ for sulfur-oxidizing bacteria) was observed in the desulfurization effluent during low-sulfur coal combustion, for example (approximately 50 Cells / mm ³ for sulfur-oxidizing bacteria). It was. “Cells” represents the number of cells. The types of microorganisms contained in the desulfurization effluent were sulfur-oxidizing bacteria, nitrite-oxidizing bacteria and other general bacteria. Furthermore, when the desulfurization effluent during low-sulfur coal combustion was observed with a microscope, the above sulfur-oxidizing bacteria (including dead bodies) produced polysaccharides, and sludge-like substances similar to sludge accumulated in the membranes of the separation membrane were found. It was found that it was formed.

  From the above, since it was highly possible that clogging of the separation membrane was caused by microorganisms growing in the desulfurization effluent, the growth of microorganisms in the desulfurization effluent was suppressed, that is, the TOC of the desulfurization effluent. If other index values can be maintained at values that suppress the growth of microorganisms, it is considered that clogging of the separation membrane can be prevented. Furthermore, this makes it possible to solve problems related to the suspension of processing operations due to backwashing, costs related to chemical washing, and environmental conservation.

  Furthermore, the solid-liquid separation membrane as described above is used for wastewater treatment in various fields such as chemistry, medicine, food, etc., and clogging problems occur as in the case of the separation membrane in the desulfurization wastewater treatment system. Yes.

  In addition to these, when microorganisms grow in the fluid to be treated, there is also a problem that a bad odor is caused.

  The present invention has been made in view of the above circumstances, and can solve problems such as sludge and bad odor caused by microorganisms in the fluid to be treated, as well as clogging of the separation membrane caused by the sludge. An object is to provide a fluid treatment method and a fluid treatment system.

  In the fluid treatment method of the present invention, another fluid having a lower pollution level than the fluid to be treated is added to the fluid to be treated containing a component for growing the microorganism, and the index value indicating the degree of contamination of the fluid to be treated is used to increase the growth of the microorganism. It dilutes so that it may become the value which suppresses, It is characterized by the above-mentioned.

  In a specific aspect of the present invention, the process target fluid is diluted and then filtered through a solid-liquid separation membrane.

  Specific examples of the index values include total organic carbon (TOC), chemical oxygen demand (COD), total oxygen demand (TOD), total carbon (TC), and biochemical oxygen demand (BOD). , Total nitrogen (TN), or ammoniacal nitrogen.

  Moreover, the specific example of the said process target fluid is desulfurization waste_water | drain.

  Furthermore, a specific example of the another fluid is waste water from a plant such as a thermal power plant.

  The fluid treatment system of the present invention includes a water quality index value measuring means for measuring an index value representing the degree of contamination of a treatment target fluid containing a component for growing microorganisms, the index value measured by the water quality index value measuring means, and the treatment And a flow rate control means for supplying another fluid to the processing target fluid so that the index value becomes a value that suppresses the growth of microorganisms based on the flow rate of the target fluid.

  In a specific aspect of the present invention, a solid-liquid separation membrane for filtering the processing target fluid diluted with the other fluid is provided.

  Specific examples of the index values include total organic carbon (TOC), chemical oxygen demand (COD), total oxygen demand (TOD), total carbon (TC), and biochemical oxygen demand (BOD). , Total nitrogen (TN), or ammoniacal nitrogen.

  Moreover, the specific example of the said process target fluid is desulfurization waste_water | drain.

  Furthermore, a specific example of the another fluid is waste water from a plant such as a thermal power plant.

  According to the fluid processing method of the present invention, the degree of contamination is reduced by diluting the processing target fluid, and the growth and proliferation of microorganisms in the processing target fluid can be suppressed. Thereby, generation | occurrence | production of the sludge and malodor resulting from microorganisms can be prevented.

  Alternatively, it is possible to prevent clogging of the separation membrane easily and at low cost because it is possible to prevent sludge caused by microorganisms from accumulating in the membrane of the separation membrane by filtering after diluting the fluid to be treated. be able to. Furthermore, in a conventional fluid treatment method using a solid-liquid separation membrane (for example, a desulfurization wastewater treatment method), since the treatment must be temporarily stopped during backwashing, it is desirable that the amount of treated water is as small as possible. Since the clogging of the separation membrane was not clarified due to the microorganisms in the fluid to be treated, as described above, the method of adding another fluid to the fluid to be treated and diluting it is completely imagined. However, by applying this method, it is no longer necessary to perform backwashing, so clogging of the separation membrane can be prevented only by performing a simple process of adding another fluid to the fluid to be treated. It becomes possible.

  In addition, as index values indicating the degree of contamination of the fluid to be treated, total organic carbon (TOC), chemical oxygen demand (COD), total oxygen demand (TOD), total carbon quantity (TC), biological Chemical oxygen demand (BOD), total nitrogen content (TN), or ammonia nitrogen can be used, and by managing the index values related to the growth of such microorganisms, Breeding and proliferation can be reliably suppressed.

  In addition, desulfurization effluent discharged from flue gas desulfurization equipment, etc. can be used as a treatment target fluid, which makes it possible for plants such as thermal power plants equipped with desulfurization equipment to be stable for a long time without maintenance such as backwashing. Thus, it becomes possible to use a separation membrane.

  Furthermore, by adopting wastewater from a plant such as a thermal power plant as another fluid to be added to the fluid to be treated, the equipment space and cost required for daily large-scale wastewater treatment in the plant can be greatly reduced, Since it is not necessary to purchase industrial water separately as a separate fluid, fluid treatment can be performed at a lower cost.

  According to the fluid processing system of the present invention, the degree of contamination is reduced by diluting the processing target fluid, and the growth and proliferation of microorganisms in the processing target fluid can be suppressed. Thereby, generation | occurrence | production of the sludge and malodor resulting from microorganisms can be prevented.

  In addition, by providing a solid-liquid separation membrane that filters the fluid to be treated diluted with another fluid, sludge caused by microorganisms is prevented from accumulating on the membrane of the separation membrane, and clogging of the separation membrane is prevented. It can be solved easily and at low cost.

  Furthermore, the index values indicating the degree of contamination of the fluid to be treated include total organic carbon (TOC), chemical oxygen demand (COD), total oxygen demand (TOD), total carbon quantity (TC), biological Chemical oxygen demand (BOD), total nitrogen content (TN), or ammonia nitrogen can be used, and by managing the index values related to the growth of such microorganisms, Breeding and proliferation can be reliably suppressed.

  Moreover, the desulfurization drainage discharged | emitted from a flue gas desulfurization apparatus etc. can be made into a process target fluid.

  Furthermore, by adopting wastewater from a plant such as a thermal power plant equipped with flue gas desulfurization equipment as another fluid to be added to the fluid to be treated, the facility space and cost required for daily large-scale wastewater treatment in the above plant In addition, it is not necessary to separately purchase industrial water or the like as a separate fluid, so that fluid treatment can be performed at a lower cost.

  FIG. 1 shows a desulfurization wastewater treatment system for carrying out the desulfurization wastewater treatment method of the embodiment.

  This desulfurization waste water treatment system is an example of a system provided in a thermal power plant using coal as fuel, and is configured as follows in order to treat the desulfurization waste water into a state in which it can be discharged.

This system
After removing the dust from the flue gas, the absorption tower 1 for reacting the sulfur oxide in the flue gas with the limestone mixture,
A dehydrator 2 for dehydrating desulfurization waste water, which is a waste liquid from the absorption tower 1, and taking out sulfur oxide as gypsum;
An oxidation tank 3 that oxidizes manganese ions contained in the desulfurization effluent to form insoluble manganese dioxide;
A storage tank 4 for storing desulfurization effluent after the oxidation step;
Add flocculants, pH adjusters, etc. to desulfurization wastewater sent from storage tanks, suspended substances in desulfurization wastewater, heavy metals, fluorine, silica, calcium, magnesium, oxidizing substances, reducing substances subject to COD, etc. A reaction vessel 5 for agglomerating a part of
A part of the substance aggregated in the reaction tank 5 is drawn out and sent to a concentration tank (not shown) for removing sludge, and desulfurization effluent filtered by a solid-liquid separation membrane described later is received and again on the solid-liquid separation membrane side A circulation tank 6 to be sent to,
A plurality of (for example, four) separation membrane units 8 including a tubular MF membrane as a solid-liquid separation membrane for filtering desulfurization waste water;
An adsorption tower 9 for performing an activated carbon adsorption treatment of a reducing substance to be subjected to COD;
A pH adjusting tank 10 for adjusting the pH of the desulfurized waste water after the activated carbon adsorption treatment to a dischargeable pH;
And a monitoring tank 11 for controlling the desulfurization drainage discharge. In this system, the desulfurization effluent discharged from the absorption tower 1 sequentially proceeds through the treatment process in the direction of the arrow in the figure, is treated in a dischargeable state, and is then discharged into a river or the sea.

  The separation membrane unit 8 is a tubular body having, for example, 178 tubular MF membranes (for example, those having an inner diameter of 5 to 9 mm) per unit, and the inlet and outlet of the processing target fluid are The diameter is smaller than the central portion (for example, the inner diameter of the central portion is 90 mm with respect to about 200 mm). And the fluid which passed MF membrane is discharged | emitted from the discharge port (not shown) provided in the surrounding surface of each separation membrane unit 8, and is sent to the adsorption tower 9 side.

In addition, this system is a specific means for diluting by adding another fluid to the desulfurization effluent flowing in the system,
A TOC measuring device 13 that measures TOC as an index value indicating the degree of contamination of desulfurization waste water;
A drainage tank 14 for storing high-salt drainage from any process of the power plant as another fluid to be added to the desulfurization drainage;
A TOC measuring device 15 that measures TOC as an index value indicating the degree of contamination of drainage in the drainage tank 14;
Based on the measured values by the TOC measuring devices 13 and 15 and the flow rate of the desulfurization drainage flowing into the storage tank 4, the drainage tank so that the TOC of the desulfurization drainage becomes a value that suppresses the growth of microorganisms (for example, TOC = 10 ppm). 14 is provided with a flow rate control device 17 for adding the high-salt drainage in 14 to the desulfurization wastewater.

  Specifically, the TOC measuring device 13 for measuring the TOC of the desulfurized waste water can be provided between the circulation tank 6 and the separation membrane unit 8, and the flow rate control device 17 is a high salt waste water in the drain tank 14. Can be configured to be sent to the storage tank 4. In addition, as high-salt drainage, steady-state drainage such as pure water drainage (high salt), condensate desalination drainage (high salt), and laboratory drainage, and various devices (for example, air preheaters, Unsteady drainage such as cleaning drainage of clinker hopper, gas gas heater, and chimney) and chemical cleaning drain of boiler can be used.

  FIG. 2 shows the configuration of the automatic measurement type TOC measuring devices 13 and 15.

First, the measurement principle of TOC will be described. The TOC burns a sample (here, desulfurized effluent or high-salt effluent) together with a carrier gas with a constant oxygen concentration in the presence of a catalyst at a high temperature, and the carbon dioxide (CO ₂ ) concentration in the combustion gas is non-dispersed infrared It can be obtained by measuring with an analyzer (NDIR) and determining the organic carbon concentration in the sample. The combustion of organic matter is expressed by the following formula.

  In addition, the inorganic carbon (IC) contained in the dissolved carbon dioxide, carbonate, bicarbonate, etc. in the sample is pyrolyzed as shown below to generate carbon dioxide, which hinders TOC measurement. The measuring devices 13 and 15 are preferably configured in consideration of the influence. The thermal decomposition of carbonate is expressed by the following formula.

  The thermal decomposition of bicarbonate is represented by the following formula.

Next, a specific configuration of the TOC measuring device 13 will be described. The TOC measuring device 13 is a specific means for automatically monitoring the TOC of the desulfurization effluent as a sample.
A carrier gas purification unit 21 for removing impurities in the carrier gas;
A purge gas purification unit 22 for removing impurities in the purge gas;
A flow rate controller 23 for setting the carrier gas to a predetermined pressure and flow rate;
A flow rate control unit 24 for setting the purge gas to a predetermined pressure and flow rate;
An IC removal unit 25 for adding an acid solution such as hydrochloric acid or nitric acid to the desulfurization waste water to adjust to pH 2 to 3 and venting purge gas to remove inorganic carbon (IC);
An acid solution storage unit 26 for storing an acid solution such as hydrochloric acid or nitric acid used for removing inorganic carbon (IC);
An electromagnetic valve 27 provided in the system of the desulfurization waste water treatment system (FIG. 1), and sends an appropriate amount (for example, 30 ml / min) of the desulfurization waste water flowing in the system to the IC removal unit;
A sample injection unit 28 that collects a certain amount of desulfurization effluent from which inorganic carbon (IC) has been removed by the IC removal unit 25 and drops it to the combustion unit 29 described later
A combustion unit 29 that burns the dropped desulfurized wastewater and oxidizes organic carbon to generate CO ₂ ;
A dehumidifying and dust removing unit 30 for removing moisture and dust in the combustion gas;
A CO ₂ detector (NDIR) 31 for measuring the CO ₂ concentration in the combustion gas;
Based on the CO ₂ concentration measured by the CO ₂ detection unit 31, a TOC calculation unit 32 for obtaining the organic carbon concentration in the desulfurization waste water;
And a communication unit 33 that sends a signal representing the TOC obtained by the TOC calculation unit 32 to the flow control device 17 (FIG. 1).

  The combustion unit 29 is composed of an electric furnace, a temperature regulator, and a catalyst filling tube installed in the electric furnace.

  The electromagnetic valve 27 is controlled by a control unit (not shown), and opens and closes at a predetermined time interval (for example, 1 hour interval) in response to a request from an operator, and the desulfurized wastewater is sent to the IC removing unit 25. Can be configured to send. Thereby, the TOC of desulfurization waste water can be measured automatically. The configuration of the TOC measuring device 15 that measures the TOC of the high-salt drainage in the drainage tank 14 is also the same as described above.

  FIG. 3 shows a configuration of a flow rate control device 17 that controls the flow rate of high-salt wastewater added to the desulfurization waste water so that the TOC of the desulfurization waste water becomes a value that suppresses the growth of microorganisms (for example, TOC = 10 ppm).

The flow rate control device 17 is a specific means for realizing the above function,
A communication unit 41 for receiving signals from the two TOC measuring devices 13 and 15 provided in the desulfurization waste water treatment system (FIG. 1);
An input unit (for example, a keyboard, a touch panel, etc.) 42 for inputting various data necessary for obtaining the supply amount of high-salt drainage, such as the flow rate (for example, pump capacity) of the desulfurization wastewater flowing into the storage tank 4;
A memory 43 as a storage unit for storing signals from the TOC measuring devices 13 and 15 and data input from the input unit;
Based on the signals from the respective TOC measuring devices 13 and 15 and the flow rate of the desulfurization wastewater flowing into the storage tank 4, the desulfurization wastewater is set to a value that suppresses the growth of microorganisms (for example, TOC = 10 ppm). A control unit 44 for determining the flow rate of high-salt drainage to be added to
A motor-driven pump 45 for supplying high-salt drainage in the drainage tank 14 to the storage tank 4;
A motor driver 46 that controls the number of revolutions of the motor that drives the pump 45 is provided in order to supply the high-salt drainage at the flow rate to the storage tank 4 based on the flow rate obtained by the control unit 44.

  Further, the TOC value necessary for the growth of microorganisms can be input in advance by the input unit 42. If a monitor is connected to the control unit 44 or the memory 43, the calculation result by the control unit 44, that is, the storage tank 4 It is also possible to monitor the flow rate of high-salt wastewater being supplied to

  FIG. 4 shows a supply control flow of high-salt drainage by the flow rate control device 17.

  First, the TOC of the high-salt drainage in the drainage tank 14 is measured by the TOC measuring device 15 (step [hereinafter referred to as ST] 1).

  Next, the TOC of the desulfurization wastewater sent from the circulation tank 6 is measured by the TOC measuring device 13 (ST2). The TOC measurement by the TOC measuring device 13 can be performed at a predetermined operation (for example, pressing of a control start button) by an operator or at a predetermined time interval.

  Thereafter, each TOC measuring device 13, 15 transmits a signal representing the measured TOC value to the flow control device 17. In response to this, in the flow control device 17 (FIG. 3), the control unit 44 determines whether or not the TOC of the desulfurized waste water is 10 or less (ST3).

  If the determination in ST3 is “YES”, that is, if the TOC of the desulfurized wastewater is already 10 or less, it is not necessary to dilute the desulfurized wastewater, so the process proceeds to ST1 and the above steps are repeated.

  On the other hand, when the determination of ST3 is “NO”, that is, when the TOC of the desulfurization wastewater is greater than 10, the high salt-based wastewater is added to the desulfurization wastewater, so that the TOC of the desulfurization wastewater is 10 or less. The value is adjusted (ST4). Specifically, the target value (TOC ≦ 10 value) of desulfurized wastewater is determined by an operator or the like, and based on this, the flow control device 17 achieves the target value and maintains it. Control to add high-salt drainage at the flow rate required to do this. The flow rate of the high-salt wastewater to be added to the desulfurization wastewater can be obtained by the following equation, for example.

In this formula (1), k is the TOC value (ppm) of high-salt drainage.
m is the TOC value of desulfurized wastewater (ppm)
W ₁ is the flow rate of high salt wastewater to be added (m ³ / h)
Q is the flow rate of desulfurization wastewater flowing into the storage tank 4 (m ³ / h)
TOC _set is the target value of TOC of desulfurized wastewater after mixing with high salt wastewater (ppm, 10 or less)
From the above formula (1), the flow rate W ₁ of the high-salt drainage to be added to the desulfurization drainage is expressed by the following formula.

So, for example,
(1) The TOC value of high-salt drainage is “k = 1 (ppm)”,
(2) The TOC value of desulfurized waste water is “m = 20 (ppm)”,
(3) The flow rate of the desulfurization waste water flowing into the storage tank 4 is “Q = 300 (m ³ / h)”,
(4) The target value of TOC of desulfurized wastewater is “TOC _set ≦ 10 (ppm)”
Then, the flow rate W ₁ (m ³ / h) of the high-salt drainage to be added to the desulfurization waste water becomes “W ₁ ≈333 (m ³ / h) or more” from the above formula (2). In this case, the desulfurization effluent is diluted by the flow control device 17 continuing to supply the high-salt drainage having a flow rate equal to or higher than the flow rate to the storage tank 4, and the growth and proliferation of microorganisms in the desulfurization effluent is suppressed.

Alternatively, the calculation result of the control unit 44 (W ₁ ≧ 333 m ³ / h in the above example) is obtained as the flow rate of the high-salt drainage to be actually supplied from the input unit 42 of the flow rate control means 17 (FIG. 3). A flow rate obtained by multiplying 1 by a coefficient “n” or more can be designated. For example, if the coefficient “n = 1.3”, the flow rate W ₂ of the high-salt drainage that is actually supplied is
“W ₂ = 333 × 1.3 = 432.9 (m ³ / h)”. The flow rate control device 17 can reliably reduce the TOC of the desulfurized waste water to a value of 10 or less by supplying the high salt waste water to the storage tank 4 based on this flow rate.

  In this way, the TOC and other water quality index values of the desulfurization wastewater filtered by the separation membrane unit 8 (FIG. 1) used in the desulfurization wastewater treatment system in the power plant are adjusted and maintained at a value that suppresses the growth of microorganisms. By doing so, the membrane of the MF membrane constituting the separation membrane unit 8 can be used while maintaining the original performance without causing clogging.

  Returning to the supply control flow (FIG. 4) again, the control unit 44 of the flow rate control device 17 obtains the flow rate of the high-salt drainage to be added to the desulfurization wastewater, and then returns to ST1 and repeats the above ST1 to ST4. Alternatively, the TOC of desulfurization wastewater and other water quality index values during operation of the power plant generally do not fluctuate rapidly, so even if the high-salt drainage at the flow rate obtained in ST4 is continuously supplied, the TOC of the desulfurization wastewater It is considered that other water quality index values can maintain the level of values that suppress the growth of microorganisms. That is, the processing of ST1 to ST4 can be performed continuously. For example, the flow rate of the high-salt drainage by ST4 is obtained only once a day, and the separation is continued by maintaining this supply amount. It is also possible to keep the membrane unit 8 in a suitable state.

  As described above, the desulfurization wastewater treatment method of the example and the desulfurization wastewater treatment system for realizing the same have been described. In the above example, the high salt-based wastewater is used as another fluid to be added to the desulfurization wastewater. It is also possible to add a fluid that is not subject to so-called wastewater treatment, such as low-salt wastewater or industrial water that is low and can be reused in a boiler or the like. In the case where such a liquid is used, when it is clear that the liquid does not contain the wastewater treatment target component, the TOC measuring device 15 for measuring the TOC of the fluid in the drainage tank 14 in the embodiment is not provided, The flow rate of another fluid to be added to the desulfurization waste water can be controlled based on the TOC and the flow rate of the desulfurization waste water.

  Further, in the examples, each TOC is measured as an index value representing the degree of sludge of desulfurization wastewater and high salt wastewater added thereto, and the TOC of desulfurization wastewater is maintained at a value that suppresses the growth of microorganisms. Although the control is performed, an index value serving as a reference for control may be a water quality index value such as COD, TOD, TC, BOD, TN, or ammonia nitrogen, in addition to the TOC. In this case, it is preferable to use a device that can measure the reference water quality index value in as short a time as possible. In addition, when an index value other than the TOC is used as a control reference, the index value measuring device can be provided at a location where the TOC measuring device 13 is provided in the desulfurization waste water treatment system (FIG. 1) of the embodiment. The method for controlling the flow rate of another fluid to be added to the drainage can be performed in the same way as in the embodiment.

  Alternatively, in the embodiment, the TOC measuring device 13 for measuring the TOC of the desulfurization wastewater is provided on the path between the circulation tank 6 and the separation membrane unit 8, but is not limited to this position. Any upstream side of the separation membrane unit 8 can be provided.

Furthermore, in the examples, the TOC of desulfurization wastewater and high-salt wastewater was measured and dilution of the desulfurization wastewater was strictly performed. However, in a system not equipped with such means, low sulfur coal combustion was observed from various experimental results. Sometimes, if desulfurization wastewater is diluted by adding high salt-based wastewater at a flow rate equal to or higher than 75% of the flow rate of the desulfurization wastewater, TOC and other water quality index values are set to values that inhibit the growth of microorganisms (for example, TOC It is also possible to maintain ≦ 10). The low sulfur coal here is an amount corresponding to 0.4% based on an amount corresponding to 0.4% of sulfur contained in coal with an SO ₂ concentration of flue gas emitted during combustion of 300 ppm. Coal with less sulfur content.

  Moreover, although the Example demonstrated the desulfurization waste water treatment method and system, the fluid filtration method and fluid filtration system of this invention are not restricted to this, The solid-liquid separation membrane in various fields, such as a chemistry, a medical treatment, and a foodstuff, was used. It can be applied to fluid processing.

The figure which shows the desulfurization waste water treatment system for enforcing the desulfurization waste water treatment method of the Example of this invention. The figure which shows the structure of the automatic measurement type TOC measuring apparatus. The figure which shows the structure of the flow control apparatus which controls the flow volume of the high salt system wastewater added to desulfurization wastewater. Supply control flow of high-salt drainage by flow control device. (A) is a figure which shows a state when filtering desulfurization waste_water | drain with a tubular microfiltration membrane (MF membrane), and (b) is a figure which shows the state at the time of backwashing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Absorption tower, 2 ... Dehydrator, 3 ... Oxidation tank, 4 ... Storage tank, 5 ... Reaction tank, 6 ... Circulation tank, 8 ... Separation membrane unit, 9 ... Adsorption tower, 10 ... pH adjustment tank, 11 ... Monitoring tank , 13, 15 ... TOC measuring device, 14 ... drainage tank, 17 ... flow rate control device, 21 ... carrier gas purification unit, 22 ... purge gas purification unit, 23 ... flow rate control unit, 24 ... flow rate control unit, 25 ... IC removal unit , 26 ... acid solution storage part, 27 ... electromagnetic valve, 28 ... sample injection unit, 29 ... combustion unit, 30 ... dehumidifying dust portion, 31 ... CO ₂ detector, 32 ... TOC calculation unit, 33 ... communication unit, 41 ... Communication unit 42 ... input unit 43 ... memory 44 ... control unit 45 ... pump 46 ... motor driver 51 ... MF membrane 52 ... sludge.

Claims (10)

  Add another fluid having a lower contamination level to the fluid to be treated containing the component for growing microorganisms, and dilute the index value indicating the degree of contamination of the fluid to be treated to a value that suppresses the growth of microorganisms. And a fluid processing method.   The fluid processing method according to claim 1, wherein the fluid to be processed is diluted and then filtered through a solid-liquid separation membrane.   The fluid treatment method according to claim 1 or 2, wherein the index value includes total organic carbon (TOC), chemical oxygen demand (COD), total oxygen demand (TOD), total carbon quantity (TC), A fluid treatment method characterized in that it is biochemical oxygen demand (BOD), total nitrogen (TN), or ammoniacal nitrogen.   4. The fluid processing method according to claim 1, wherein the processing target fluid is desulfurization waste water.   5. The fluid filtration method according to claim 1, wherein the another fluid is drainage discharged from a plant such as a thermal power plant. A water quality index value measuring means for measuring an index value indicating the degree of contamination of a fluid to be treated containing a component for growing microorganisms;
Based on the index value measured by the water quality index value measuring means and the flow rate of the treatment target fluid, the flow rate of supplying another fluid to the treatment target fluid so that the index value becomes a value that suppresses the growth of microorganisms And a fluid processing system.   The fluid processing system according to claim 6, further comprising a solid-liquid separation membrane that filters the fluid to be processed diluted with the other fluid.   The fluid treatment system according to claim 6 or 7, wherein the index value includes total organic carbon content (TOC), chemical oxygen demand (COD), total oxygen demand (TOD), total carbon content (TC), A fluid treatment system characterized in that it is biochemical oxygen demand (BOD), total nitrogen (TN), or ammoniacal nitrogen.   9. The fluid processing system according to claim 6, wherein the processing target fluid is desulfurization waste water. The fluid treatment system according to any one of claims 6 to 9, wherein the another fluid is drainage discharged from a plant such as a thermal power plant.

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