JP2008180492A - Preparation method for boiler supply water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a carryover in a steam boiler while reducing a blow of boiler water. <P>SOLUTION: Makeup water treated with filtering by a crossflow filter unit 55 having a nano filtering film is supplied to a water storage tank 40 to be stored as boiler supply water to be fed to the steam boiler 20. In this process, electrical conductivity of the makeup water fed to the crossflow filter unit 55 is measured, and when the electrical conductivity exceeds a predetermined value, a blow rate in the crossflow filter unit 55 is increased. In this way, various ionic components are effectively removed from the boiler supply water stored in the water storage tank 40 during preparation of the boiler supply water, so that increase in the electrical conductivity causing a carryover is suppressed even if condensation proceeds in the steam boiler 20. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for preparing boiler feed water, and in particular, to a steam boiler device that supplies boiler water stored in a water storage tank capable of receiving make-up water to a steam boiler and heats it, and uses the generated steam in a load device. And a method for preparing the boiler feed water from the makeup water.

  The steam boiler stores the supplied boiler feed water as boiler water, and heats the boiler water to generate steam, but as the steam is generated, the boiler water is concentrated, and chloride ions contained in the boiler water The concentration of various ion components such as sulfate ions increases. Since boiler water has an increased electrical conductivity due to an increase in the concentration of ionic components, it causes a carry-over in which a part of the generated steam is mixed, thereby reducing the quality of the steam. Therefore, in the operation of a steam boiler, a carry-over preventing agent is added to boiler feed water or boiler water in order to suppress the occurrence of carry-over (for example, Patent Document 1).

JP 2001-47087 A

  However, the boiler water to which the carry-over preventing agent is added increases the concentration of the carry-over preventing agent as the concentration progresses, and as a result, the ionic component concentration increases and the electrical conductivity increases. Due to the necessity of controlling the electrical conductivity by suppressing the increase in concentration, it is often necessary to drain (blow) a part from the steam boiler, replenish new boiler feed water, and dilute. Here, since the blown boiler water may cause environmental pollution due to the carry-over preventing agent, it is necessary to perform an appropriate drainage treatment such as decomposition and separation of the carry-over preventing agent. Also, if boiler water is blown frequently and diluted with boiler feed water, the boiler water consumption will increase during steam boiler operation, and frequent heating of boiler water whose temperature has dropped due to boiler water supply will be necessary. As a result, energy consumption increases.

  An object of the present invention is to suppress carryover in a steam boiler while suppressing blow of boiler water.

  In the boiler boiler water supply method according to the present invention, the boiler feed water stored in the water storage tank capable of receiving makeup water is supplied to the steam boiler and heated, and the steam generated thereby is used in the load device. A method for preparing boiler feed water from make-up water, supplying make-up water to a cross-flow filtration device using one of a nanofiltration membrane and a reverse osmosis membrane, and blowing from the cross-flow filtration device Step A for filtering the make-up water with the amount set to a predetermined blow amount, Step B for supplying the make-up water filtered in Step A to the water storage tank, and electricity for the make-up water to be supplied to the cross-flow filter And C for measuring conductivity. Here, when the electrical conductivity measured in the process C exceeds a predetermined value, the blow amount from the crossflow filtration device is set to be larger than the predetermined blow amount in the process A.

  In such a boiler feed water preparation method, makeup water is supplied to a water storage tank and stored in Step B after the ionic component is removed by one of the nanofiltration membrane and reverse osmosis membrane in Step A. . In this process, make-up water is measured for electrical conductivity in step C.

  Here, when the electrical conductivity measured in the step C exceeds a predetermined value, for example, replenishment that is filtered in the cross-flow type filtration device due to water quality fluctuation (abnormal increase in ion component concentration) used as makeup water. When it is predicted that the ionic component concentration of water will increase and it will be difficult to remove the ionic component from the makeup water by the nanofiltration membrane or reverse osmosis membrane, the amount of blow from the cross-flow type filtration device will be larger than the predetermined blow amount. Set and execute step A. As a result, the cross flow type filtration device has a reduced concentration on the membrane surface, an increased ability to remove ionic components, and can effectively reduce the ionic component concentration in the makeup water after treatment.

  Therefore, according to this preparation method, it is possible to prepare boiler feed water from which an ionic component that causes an increase in the electrical conductivity of boiler water in a steam boiler is stably removed. The steam boiler that is operated by supplying this boiler feed water suppresses the increase in the electrical conductivity of the boiler water even if the boiler water concentration accompanying the generation of steam proceeds. Over can be suppressed.

  The boiler feed water preparation method according to the present invention further includes, for example, a step D of supplying condensate obtained by condensing steam used in the load device to a water storage tank and mixing it with makeup water stored in the water storage tank. Including. In the process D, for example, condensate is stored in a condensate tank, and the condensate stored in the condensate tank is supplied to the storage tank at a constant rate. Alternatively, in step D, the condensate is stored in the condensate tank and the electrical conductivity of the makeup water stored in the storage tank is measured, and the electrical conductivity of the makeup water stored in the storage tank exceeds a predetermined value. Sometimes the condensate stored in the condensate tank is supplied to the water storage tank.

  According to the preparation method of the present invention including such a step D, the makeup water stored in the water storage tank is stably mixed with the condensate and diluted. Therefore, in the water storage tank, boiler feed water having a lower ionic component concentration is stably prepared, and the steam boiler to which this boiler feed water is supplied suppresses carryover while suppressing blow more effectively. Can do.

  The boiler feed water preparation method according to the present invention includes a process E for removing hardness from the makeup water supplied to the cross-flow filter by ion exchange with a sodium ion exchange resin, and a process A and a process B. And a step F of removing the dissolved oxygen contained in the makeup water by passing the makeup water filtered in the cross-flow type filtration device through the deoxygenation device. In this case, the process E is performed by one resin unit selected from a resin unit group including at least two resin units having a sodium type cation exchange resin, and makeup water is passed through the deaerator at a predetermined flow rate. Execute step F, measure the makeup water hardness and water temperature together in step C, and if the measured hardness exceeds a predetermined value, select another resin unit in the resin unit group and execute step E. When the measured water temperature is lower than the predetermined temperature, it is preferable that the makeup water is passed through the deoxygenation device at a flow rate lower than the predetermined flow rate in Step F.

  In the preparation method of the present invention including these steps, the makeup water from which the hardness and the dissolved oxygen that cause scale generation and corrosion in the steam boiler apparatus are removed is stored in the water storage tank as boiler feed water. . Therefore, the steam boiler apparatus using this boiler feed water can suppress the generation of scale and the occurrence of corrosion at the same time as the suppression of carryover.

  Since the boiler feed water preparation method according to the present invention includes the steps as described above, the steam boiler apparatus using the boiler feed water prepared by this preparation method is a steam boiler while suppressing the blow of boiler water. Carry over can be suppressed.

  With reference to FIG. 1, the steam boiler apparatus which can implement the preparation method of the boiler feed water which concerns on one Embodiment of this invention is demonstrated. In FIG. 1, a steam boiler device 1 is for supplying steam to a load device 2 that is a steam using facility such as a heat exchanger, a steam kettle, a reboiler, or an autoclave, and includes a water supply device 10 and a steam boiler 20. And a condensate path 30 is mainly provided.

  The water supply device 10 is for supplying boiler feed water to the steam boiler 20, a storage tank 40 for storing boiler feed water, a supply path 50 for supplying makeup water used as boiler supply water to the storage tank 40, and A control device 70 is mainly provided. The water storage tank 40 has a water supply path 41 extending from the bottom to the steam boiler 20. The water supply path 41 communicates with the steam boiler 20, and has a water supply pump 42 for sending the boiler water stored in the water storage tank 40 to the steam boiler 20.

  The supply path 50 has a water injection path 51. The water supply channel 51 supplies makeup water to a storage tank 40 from a raw water tank (not shown) in which raw water supplied from a water source such as tap water, industrial water, or groundwater, preferably raw water containing silica is stored. For this purpose, a pretreatment device 52, a water softening device 53, a preliminary filtration device 54, a cross-flow filtration device 55, and a deoxygenation device 56 are provided in this order toward the water storage tank 40. In the water injection channel 51, a hardness sensor 57, a first electrical conductivity sensor 58, and a water temperature sensor 59 are disposed between the preliminary filtration device 54 and the cross flow filtration device 55. Further, the water injection channel 51 has a flow rate control valve 60 between the crossflow filtration device 55 and the deoxygenation device 56.

  The pretreatment device 52 is a filtration device filled with activated carbon capable of adsorbing an oxidizing agent such as sodium hypochlorite that may be dissolved in the makeup water from the raw water tank. It is for removing oxidizing agents such as sodium.

  As shown in FIG. 2, the water softening device 53 includes a resin unit group 61 including two resin units, a first resin unit 61a and a second resin unit 61b. In the water softening device 53, the water injection path 51 is branched into two paths, a first path 51a and a second path 51b, by the switching valve 62, and the first path 51a communicates with the first resin unit 61a. The second path 51b communicates with the second resin unit 61b. The first path 51 a and the second path 51 b merge together at the downstream side of the resin units 61 a and 61 b and extend to the preliminary filtration device 54.

  Here, each resin unit 61a, 61b is filled with sodium-type cation exchange resin. The sodium-type cation exchange resin is for replacing the hardness component contained in the makeup water treated in the pretreatment device 52, that is, calcium ions and magnesium ions with sodium ions, and converting the makeup water into softened water. is there. The switching valve 62 is an electromagnetic valve and is used to select the water injection path 51 as either the first path 51a or the second path 51b.

  In the water softening device 53, the first resin unit 61a and the second resin unit 61b are detachable, and the sodium-type cation exchange resin can be exchanged.

  The preliminary filtration device 54 is for removing solid substances such as suspended solids and dust that may be mixed in the makeup water softened by the water softening device 53, and filters the solid matter. A filter medium (not shown) such as a wind filter, a pleated filter or a mesh filter for separation is provided.

  The cross-flow filtration device 55 filters and separates various dissolved components contained in the makeup water treated in the preliminary filtration device 54, that is, various ion components such as chloride ions and sulfate ions, and low molecular weight substances. As shown in FIG. 3, the pressure pump 80 and a filtration membrane module 81 disposed on the downstream side of the pressure pump 80 are mainly provided. The treatment liquid path 82, the water inlet path 83, and the concentrated liquid path 84 are connected.

  In the filtration membrane module 81, when the makeup water from the preliminary filtration device 54 is introduced through the inlet channel 83, the makeup water filtered out from the treatment liquid channel 82 flows out and the makeup water concentrated from the concentrate channel 84. Is configured to flow out. Further, the concentrated liquid path 84 is branched into a drainage path 85 and a reflux path 86, and the reflux path 86 is connected to a water inlet path 83 on the upstream side of the pressurizing pump 80. The drainage channel 85 has a blow control valve 87 for controlling the drainage amount of makeup water, that is, the blow amount.

  The filtration membrane module 81 includes a filtration membrane element (not shown) for filtering dissolved components contained in the makeup water. The filtration membrane used in this filtration membrane element is a nanofiltration membrane. The nanofiltration membrane is formed using a synthetic polymer such as a polyamide-based or polyether-based material that is generally referred to as an NF (Nanofiltration) membrane, and is an AMST (Association of Membrane Separation Technology) standard AMST- 002, “The molecular weight range of the separation target substance used at an operating pressure of 1.5 MPa and showing a removal rate of 90% or more shows 200 to 1,000, and the sodium chloride concentration of the test solution is 500 to 2,000 mg / liter. , A membrane having a sodium chloride removal rate of 5% or more and less than 93% under an evaluation condition of an operating pressure of 0.3 to 1.5 MPa ”. Incidentally, nanofiltration membranes are commercially available from various companies and can be easily obtained.

In the filtration membrane element, the nanofiltration membrane is used in various shapes. That is, the nanofiltration membrane is used in various shapes such as a flat membrane type, a hollow fiber membrane type, a tubular type, and a Nomoris type.
The treatment liquid path 82 extends from the filtration membrane module 81 and is for supplying makeup water filtered in the filtration membrane module 81 to the deoxygenation device 56.

  The deoxygenation device 56 is for removing dissolved oxygen in the make-up water filtered in the cross-flow type filter device 55, and the deoxygenation capability increases as the residence time of the make-up water passing through increases. For example, a type in which make-up water is passed through a gas separation membrane to remove dissolved oxygen (for example, a form in which make-up water is passed through the inside of the hollow fiber-like gas separation membrane while depressurizing the outside to remove dissolved oxygen. In a variety of types, such as a type that removes dissolved oxygen by passing make-up water under reduced pressure, or a type that removes dissolved oxygen by passing make-up water while heating Is used.

  The hardness sensor 57 is for measuring the hardness of makeup water from the preliminary filtration device 54, and is, for example, a colorimetric sensor, an electrode sensor, or a titration sensor. The first electrical conductivity sensor 58 is for measuring the electrical conductivity of the makeup water from the preliminary filtration device 54, and is, for example, an electrode type sensor. The water temperature sensor 59 is for measuring the temperature of the makeup water supplied from the preliminary filtration device 54, and is, for example, a sensor such as a thermistor, a thermocouple, or a resistance temperature detector.

  The flow rate adjustment valve 60 is an electromagnetic valve, and can arbitrarily adjust the flow rate of makeup water flowing from the crossflow filtration device 55 to the deoxygenation device 56.

  Based on the hardness information, the electrical conductivity information, and the water temperature information measured by the hardness sensor 57, the first electrical conductivity sensor 58, and the water temperature sensor 59, the control device 70 switches the switching valve 62, the blow control valve 87, and the flow rate control valve. 60 for controlling.

  The steam boiler 20 is a once-through boiler, and as shown in FIG. 4, an annular storage portion 21 capable of storing boiler feed water supplied from a water supply path 41, and a large number of heat transfer tubes 22 rising from the storage portion 21 (FIG. 4). Only two are shown), and mainly includes an annular header 23 provided at the upper end of the heat transfer tube 22, a steam supply passage 24 extending from the header 23 to the load device 2, and a combustion device 25 such as a burner. The combustion device 25 can radiate combustion gas from the header 23 side toward the storage portion 21 to heat the heat transfer tube 22.

  The heat transfer tube 22 is for generating steam from boiler feed water, and is formed using a non-passivated metal. A non-passivated metal refers to a metal that does not passivate naturally in a neutral aqueous solution, and is usually a metal other than stainless steel, titanium, aluminum, chromium, nickel, zirconium, and the like. Specifically, carbon steel, cast iron, copper, copper alloy, and the like. Carbon steel may be passivated in the presence of a high concentration of chromate ions even in a neutral aqueous solution. This passivation is due to the influence of chromate ions, and the neutral aqueous solution. It's hard to say that it's a natural passivation inside. Therefore, carbon steel belongs to the category of non-passivated metals here. In addition, copper and copper alloys are considered to be metals that are unlikely to corrode due to the influence of moisture due to their noble position in the electrochemical column (emf series), but they are naturally passive in neutral aqueous solutions. Since it does not become a non-passivated metal, it belongs to the category of non-passivated metals.

  The condensate path 30 is for sending condensate to the water storage tank 40, and includes a first conduit 31, a condensate tank 32 for storing condensate, and a second conduit 33. The first pipeline 31 extends from the load device 2 to the spare tank 32 and has a steam trap 34. The steam trap 34 is for separating steam and water. The front end of the first conduit 31 is normally disposed near the bottom of the condensate tank 32 so as not to entrain air into the condensate stored in the reserve tank 32. The second conduit 33 extends from the condensate tank 32 to the water storage tank 40, and supplies the condensate stored in the condensate tank 32 to the water storage tank 40. The second conduit 33 has a control valve 35 for controlling the amount of condensate supplied from the condensate tank 32 to the water storage tank 40, and air is supplied to the boiler feedwater stored in the water storage tank 40. In order to prevent the water from being caught, the tip portion is usually disposed near the bottom of the water storage tank 40. The first pipe line 31 and the second pipe line 33 are formed using a non-passivated metal like the heat transfer pipe 22.

  Next, the operation method of the above-mentioned steam boiler apparatus 1 is demonstrated, touching the preparation method of boiler feed water. Here, in the initial state, the control device 70 switches the switching valve 62 to the first path 51a side, and the blow control valve 87 so that the blow amount from the crossflow filtration device 55 becomes the predetermined blow amount P. Further, the flow rate adjustment valve 60 is set so that the flow rate of the makeup water flowing from the crossflow filtration device 55 to the deoxygenation device 56 becomes the predetermined flow rate Q. The control valve 35 is set so that the condensate stored in the condensate tank 32 can be gradually supplied to the water storage tank 40 at a constant rate, that is, at a constant amount per unit time.

  During operation of the steam boiler device 1, makeup water is supplied from the raw water tank to the water storage tank 40 through the water injection channel 51, and this makeup water is stored in the water storage tank 40 as boiler feed water.

  At this time, the makeup water from the raw water tank is first supplied to the pretreatment device 52 through the water injection channel 51, where the oxidant is adsorbed and removed by the activated carbon. Subsequently, makeup water from the pretreatment device 52 flows to the water softening device 53. The makeup water that has flowed to the water softening device 53 flows to the first path 51a via the switching valve 62 and passes through the first resin unit 61a. Thereby, the hardness component contained in the makeup water is ion-exchanged with sodium ions by the sodium-type cation exchange resin, and becomes softened water from which the hardness component has been removed.

  Incidentally, the sodium-type cation exchange resin used in the water softening device 53 is easily deteriorated due to the influence of the oxidizing agent, and the ion exchange capacity tends to be lowered. In this embodiment, the makeup water supplied to the water softening device 53 is Since the oxidizing agent is removed in the pretreatment device 52, the sodium-type cation exchange resin is hardly deteriorated. Therefore, the water softening device 53 can soften the makeup water stably over a long period of time.

  The make-up water that has become softened in the water softening device 53 is then filtered in the pre-filtering device 54 to remove suspended solids and solids such as dust, and then further filtered in the cross-flow filter 55. It is processed. In the cross-flow filtration device 55, makeup water from the preliminary filtration device 54 is continuously supplied to the filtration membrane module 81 through the water inlet 83 by the pressurizing pump 80. Part of the supplied makeup water passes through the filtration membrane and flows out to the treatment liquid path 82, and the remainder flows out to the concentrated liquid path 84 without passing through the filtration membrane. Further, part of the makeup water that has flowed out to the concentrate channel 84 is blown out of the system through the drainage channel 85, and the remainder is returned to the inlet channel 83 through the reflux channel 86. For this reason, the replenishing water supplied to the filtration membrane module 81 circulates in the apparatus while being partially concentrated.

  The makeup water that permeates the filtration membrane is filtered by the filtration membrane. As a result, the makeup water removes various ion components that cause the electrical conductivity to increase. On the other hand, most (usually 40% or more) of silica derived from raw water contained in the makeup water passes through the filtration membrane.

  Incidentally, since the oxidant is removed from the replenishing water from the preliminary filtration device 54 by the pretreatment device 52 and the solid matter is removed by the preliminary filtration device 54, the filtration membrane of the crossflow filtration device 55 is Deterioration due to oxidation hardly occurs, and clogging hardly occurs. Therefore, the cross-flow filtration device 55 can stably remove the ionic components as described above from the makeup water over a long period of time.

  The makeup water filtered by the crossflow filtration device 55 flows out of the crossflow filtration device 55 through the treatment liquid path 82, and subsequently deoxygenated by the deoxygenation device 56. As a result, the makeup water removes dissolved oxygen that promotes corrosion (particularly pitting corrosion) of the heat transfer tubes 22 and the like of the steam boiler 20 and corrosion of the condensate passage 30.

  As a result, in the replenishment path 50, replenishment water made of softened water that has been deoxygenated and from which ionic components have been removed is prepared, and this replenishment water is stored in the water storage tank 40 as boiler feed water. This boiler feed water contains silica that has passed through the filtration membrane of the cross-flow filtration device 55.

  When the water supply pump 42 is operated in a state where makeup water is stored in the water storage tank 40, the makeup water stored in the water storage tank 40, that is, boiler water supply, is supplied to the steam boiler 20 through the water supply path 41. Boiler feed water supplied to the steam boiler 20 is stored as boiler water in the storage unit 21. The boiler water rises in the heat transfer tubes 22 while being heated by the combustion device 25 through the heat transfer tubes 22 and gradually becomes steam. Then, the steam generated in each heat transfer tube 22 is collected in the header 23 and supplied to the load device 2 through the steam supply path 24.

  Here, since various ionic components that cause an increase in electrical conductivity are removed from the boiler water and no chemicals are added, the electrical conductivity is hardly increased even when the concentration proceeds. For this reason, the carry-over of the steam boiler 20 can be suppressed, high-quality steam can be stably supplied to the load device 2, and the blow amount for diluting boiler water can be suppressed. Therefore, the steam boiler device 1 can reduce the amount of supply of boiler feed water and heat loss due to the blow of boiler water, thereby reducing the consumption of boiler feed water and the energy consumption for heating the boiler water. be able to.

  The steam supplied to the load device 2 passes through the load device 2 and flows to the first pipe 31 where it loses latent heat and partly changes to condensed water, and the steam and water are separated in the steam trap 34. It becomes hot condensate. The condensate thus generated is supplied from the first conduit 31 to the condensate tank 32 and stored in the reserve tank 32. The condensate stored in the condensate tank 32 is adjusted in flow rate by the control valve 35 and gradually flows through the second conduit 33, and is supplied to the water storage tank 40 and mixed with makeup water.

  Here, the makeup water stored in the water storage tank 40 is heated by mixing high temperature condensate. Therefore, since the boiler feed water prepared in the water storage tank 40 has a higher temperature than the makeup water, the heating burden on the steam boiler 20 is reduced, and the steam boiler apparatus 1 uses the energy consumption for operating the steam boiler 20. Can be suppressed and can be operated economically. In addition, since the boiler feed water prepared by mixing the condensate with the makeup water in the water storage tank 40 is obtained by diluting the makeup water with the condensate, the ionic component concentration further decreases. For this reason, the steam boiler 20 to which the boiler feed water is supplied is less likely to increase the electrical conductivity even when the boiler water is concentrated, so that carry-over is further effectively suppressed, and the boiler water is diluted. It is possible to further suppress the amount of blow to be performed.

  The steam boiler device 1 has a low recovery amount of condensate when the amount of steam used in the load device 2 is small (referred to as “low load operation”) and a large amount of steam used in the load device 2 (“high load operation”). )), The amount of recovered condensate is large. For this reason, if condensate is supplied directly to the water storage tank 40 without being stored in the condensate tank 32, the makeup water stored in the water storage tank 40 is difficult to be diluted by the condensate during low load operation, and during high load operation. Since the makeup water is easily diluted by condensate, the makeup water dilution by condensate becomes unstable. Therefore, in order to effectively suppress carryover in the steam boiler 20, the blow amount in the steam boiler 20 is normally increased with reference to the dilution rate of makeup water by the amount of condensate recovered during low-load operation. Must be set to However, if the blow amount is set based on such a standard, the boiler water will be excessively blown on the basis of the low load operation even during the high load operation where the dilution rate of the makeup water is higher than that during the low load operation. As a result, boiler water consumption increases and heat loss occurs.

  Therefore, in this embodiment, the condensate recovered in the condensate tank 32 is supplied to the water storage tank 40 at a constant rate, that is, at a constant amount per unit time by adjusting the control valve 35. Thereby, since the dilution rate of the makeup water by the condensate can be stabilized in the water storage tank 40 regardless of the low load operation and the high load operation, the steam boiler 20 is less than the blow amount in the low load operation. It can be operated with a blow amount. That is, in the steam boiler 20, it is possible to more effectively suppress the blow amount while suppressing carryover, and it is possible to more effectively reduce the consumption of boiler feed water and the energy consumption due to heat loss.

  During the operation of the steam boiler apparatus 1 as described above, boiler water by boiler feed water stored in the steam boiler 20 contacts the inner surface of the heat transfer tube 22 and the like. In general, the heat transfer tube 22 or the like made of non-passivated metal is easily corroded under the influence of boiler water, but in this embodiment, the dissolved boiler is removed from the boiler feed water, so the steam boiler 20 Is less likely to cause corrosion of the heat transfer tube 22 or the like, particularly pitting corrosion, which is local corrosion. Moreover, since the silica contained in boiler feed water forms a film | membrane in the storage part 21 of the steam boiler 20, and the internal surface of the heat exchanger tube 22, the corrosion inhibitory effect with respect to the steam boiler 20 can be heightened. Furthermore, since the dissolved oxygen is removed from the boiler water, steam generated by the heating is unlikely to corrode the condensate passage 30.

  Moreover, in this steam boiler apparatus 1, since the boiler feed water supplied to the steam boiler 20 is softened water from which the hardness has been removed, the heat transfer tube 22 is also restrained from adhering to the scale.

  During the operation of the steam boiler device 1, the hardness sensor 57, the first electrical conductivity sensor 58, and the water temperature sensor 59 are always in contact with the hardness, electrical conductivity, and makeup water flowing from the preliminary filtration device 54 to the crossflow filtration device 55. Each water temperature is measured. The purpose of measuring the hardness of the make-up water with the hardness sensor 57 is to check the treatment status of the make-up water in the water softening device 53, that is, the water softening status. The purpose of measuring the electrical conductivity of the makeup water with the first electrical conductivity sensor 58 is to determine the amount of the ion component contained in the makeup water. Furthermore, the purpose of measuring the temperature of the makeup water with the water temperature sensor 59 is to predict the amount of dissolved oxygen contained in the makeup water. In the makeup water, the lower the water temperature, the higher the solubility of dissolved oxygen and the more dissolved oxygen amount. Therefore, the tendency of the dissolved oxygen amount can be predicted by the water temperature.

  When the hardness of the makeup water measured by the hardness sensor 57 exceeds a predetermined value X set in advance, the sodium-type cation exchange resin breaks through the first resin unit 61a of the water softening device 53 (decrease in ion exchange capacity). Therefore, the control device 70 operates the switching valve 62 to switch the water injection path 51 from the first path 51a to the second path 51b. Thereby, the makeup water from the pretreatment device 52 flows to the second path 51b and is supplied to the second resin unit 61b, and is subjected to ion exchange treatment with the sodium-type cation exchange resin. As a result, supply water having a low hardness is continuously supplied to the water storage tank 40, so that the steam boiler 20 can effectively suppress scale generation without adding chemicals to the boiler feed water. The

Here, the predetermined value X is normally arbitrarily set within a range of less than the hardness of the boiler feed water that can set the hardness of the boiler water below the upper limit value of the hardness allowed in the boiler water concentrated in the steam boiler 20. Value. For example, when the upper limit value of hardness allowed in boiler water is 10 milligrams / liter (CaCO ₃ equivalent) and the boiler water concentration ratio in the steam boiler 20 is 10 times, the predetermined value X is 1 milligram / liter ( Set to an arbitrary value less than (CaCO ₃ conversion).

  While the water injection channel 51 is switched to the second channel 51b, the first resin unit 61a is removed from the water softening device 53, and the sodium-type cation exchange resin is replaced with a new one. In this way, when the hardness of the makeup water measured by the hardness sensor 57 exceeds the predetermined value X set in advance when the second resin unit 61b is used, the controller 70 causes the water injection channel 51 to pass through the second channel. By switching from 51b to the first path 51a, the first resin unit 61a in which the sodium-type ion exchange resin has been exchanged can be used for ion exchange treatment of makeup water. As described above, if the sodium-type cation exchange resin filled in the resin unit other than the resin unit selected in the resin unit group 61 (that is, the resin unit in use) is replaced while it is not in use, makeup water is supplied. When the hardness exceeds the predetermined value X set in advance, the resin unit can be quickly changed to the other one by switching the switching valve 62. Therefore, the hardness of the makeup water is more reliably removed by the water softening device 53.

  Further, when the electrical conductivity of the makeup water measured by the first electrical conductivity sensor 58 exceeds a predetermined value Y, the amount of the ionic component of the makeup water increases due to water quality fluctuation (abnormal increase in ion component concentration), etc. Can be determined. Therefore, the control device 70 controls the blow control valve 87 to set the blow amount of makeup water circulating in the cross flow filtration device 55 to be larger than the predetermined blow amount P. Thereby, in the filtration membrane module 81, since the makeup water concentrated by circulation is diluted with the newly-supplied makeup water, the concentration on the membrane surface decreases, and the ionic components in the makeup water that permeate the filtration membrane Increase in volume is suppressed. Therefore, the filtration membrane reduces the load for removing the ionic component and can maintain the ionic component removal capability. Therefore, make-up water having a low electrical conductivity is supplied from the cross-flow filtration device 55 to the treatment liquid. It will continue to be stably supplied to the deoxygenation device 56 through the path 82. As a result, the carry-over of the steam boiler 20 is stably suppressed without increasing the blow amount of boiler water.

  Here, the predetermined value Y is usually arbitrarily set between the average value and the minimum value of the electrical conductivity of the raw water throughout the year. In addition, the predetermined blow amount P is usually 50 to 90 in the cross flow type filtration device 55 with a water recovery rate (permeated water amount of the cross flow type filtration device 55 / replenishment water amount supplied to the cross flow type filtration device 55 × 100). It is arbitrarily set to be in the range of%.

  When the electrical conductivity of the makeup water measured by the first electrical conductivity sensor 58 returns to the predetermined value Y or less, the control device 70 controls the blow control valve 87 and the amount of blow from the crossflow filtration device 55. Is returned to the predetermined blow amount P. For this reason, the steam boiler apparatus 1 can suppress the waste of make-up water to the minimum, and economical operation becomes possible.

  Further, when the water temperature of the make-up water measured by the water temperature sensor 59 becomes lower than the predetermined water temperature T, the amount of dissolved oxygen in the make-up water is increased, and it is expected that the deoxygenation process in the deoxygenator 56 is insufficient. Therefore, the control device 70 controls the flow rate adjustment valve 60 to reduce the flow rate of the makeup water flowing from the crossflow filtration device 55 to the deoxygenation device 56 to be less than the predetermined flow rate Q. As a result, the deoxygenation device 56 has a reduced supply flow rate of the make-up water and a longer stay time of the make-up water, thereby increasing the ability to remove dissolved oxygen from the make-up water. Therefore, even if the water temperature of the makeup water is lowered, the water storage tank 40 continues to be supplied with the makeup water with a small amount of dissolved oxygen.

  Here, the predetermined water temperature T is normally arbitrarily set in a temperature range equal to or higher than the minimum value of the water temperature at which dissolved water having a dissolved oxygen concentration of 0.5 mg / liter or less can be stably obtained. Further, the predetermined flow rate Q is normally arbitrarily set in a flow rate range equal to or higher than the flow rate of boiler feed water that can achieve the maximum steam generation amount per hour of the steam boiler 20.

  When the water temperature of the make-up water measured by the water temperature sensor 59 returns to the predetermined water temperature T or higher, the control device 70 controls the flow rate control valve 60 and supplies the make-up water flowing from the crossflow filtration device 55 to the deoxygenation device 56. The flow rate is returned to the predetermined flow rate Q.

  As a result, in the water storage tank 40, the makeup water from which dissolved oxygen is more reliably removed is stored as boiler feed water, and the steam boiler device 1 does not need to add chemicals to the boiler feed water. Progress of corrosion (particularly pitting corrosion) of the steam boiler 20 is effectively suppressed, and corrosion of the condensate passage 30 is also effectively suppressed.

Modification (1) In the above-described embodiment, the nanofiltration membrane is used as the filtration membrane of the cross-flow filtration device 55. However, this nanofiltration can be changed to a reverse osmosis membrane. The reverse osmosis membrane is formed using a synthetic polymer such as polyamide, generally called RO (Reverse Osmosis) membrane. In AMST-002 of AMST (Association of Membrane Separation Technology) standard, “ It is defined as a membrane having a sodium chloride removal rate of 93% or more under the evaluation conditions of a sodium chloride concentration of 500 to 2,000 mg / liter and an operating pressure of 0.5 to 3.0 MPa. Therefore, reverse osmosis membranes are distinguished from nanofiltration membranes in the AMST standard. Incidentally, reverse osmosis membranes are commercially available from various companies and can be easily obtained.

  Reverse osmosis membranes are used in various shapes, similar to nanofiltration membranes. That is, the reverse osmosis membrane is used in various shapes such as a flat membrane type, a hollow fiber membrane type, a tubular type, and a Nomoris type.

  When the reverse osmosis membrane and the nanofiltration membrane are compared in terms of the ability to remove ionic components contained in the makeup water, the former is superior to the latter. Can be set smaller, whereby the blow-up and carry-over of boiler water in the steam boiler 20 can be more effectively suppressed. However, when a reverse osmosis membrane is used, the predetermined blow amount is set to be larger in order to reduce the burden of the filtration membrane in the cross-flow filtration device 55 and increase the ability to remove ion components, compared to the case of using a nanofiltration membrane. Since it is necessary to do so, it is easy to waste makeup water. Therefore, it is preferable to select the reverse osmosis membrane and the nanofiltration membrane based on the general water quality of raw water that can be supplied as make-up water to the steam boiler device 1, that is, the ionic component concentration. Specifically, reverse osmosis membranes are selected for raw water with a generally high ionic component concentration (this tendency is strong in North America and China), and nanofiltration for raw water with a generally low ionic component concentration. It is preferred to select a membrane.

(2) In the above embodiment, the condensate stored in the condensate tank 32 is supplied to the water storage tank 40 at a constant rate by the flow rate control by the control valve 35, but the condensate is supplied from the condensate tank 32 to the water storage tank 40. The method of supplying can be changed. For example, as shown by a dotted line in FIG. 1, a second electrical conductivity sensor 43 for measuring the electrical conductivity of makeup water stored in the water storage tank 40 is arranged, and the second electrical conductivity sensor 43 It is set so that the control valve 35 operates in conjunction with the measured value. Specifically, when the electrical conductivity of the makeup water in the water storage tank 40 measured by the second electrical conductivity sensor 43 exceeds a predetermined value, the control valve 35 is opened, and the electrical conductivity reaches the predetermined value. It is set so that the control valve 35 is closed when recovered. According to this, the makeup water stored in the water storage tank 40 is diluted by the condensate from the condensate tank 32 so that the electric conductivity is constant, and the dilution rate is further stabilized. Carryover can be suppressed while further reducing the blow amount.

(3) In the above embodiment, the water softening device 53 replaces the sodium-type cation exchange resin of the unused resin unit, but the sodium-type cation exchange resin of the resin unit is not used. During use, it can be regenerated while attached to the water softening device 53.

  In this case, a sodium chloride aqueous solution preparation device is provided in the water softening device 53, and the sodium chloride aqueous solution is supplied from this preparation device into an unused resin unit. Thereby, the hardness component adhering to the sodium-type cation exchange resin is again exchanged with sodium ions, and the sodium-type cation exchange resin has an increased ion exchange capacity with the hardness component.

(4) In the above embodiment, the water softening device 53 uses the resin unit group 61 having the two resin units 61a and 61b. However, the resin unit group 61 has three or more resin units. May be.

(5) In the above-described embodiment, the hardness sensor 57, the first electrical conductivity sensor 58, and the water temperature sensor 59 are disposed between the preliminary filtration device 54 and the crossflow filtration device 55, so The conductivity and the water temperature are measured, but the hardness of the makeup water, the electrical conductivity, and the water temperature can also be measured between the water softening device 53 and the preliminary filtration device 54. However, in order to further enhance the deoxygenation capacity of the deoxygenation device 56, the temperature of the makeup water is preferably measured immediately before the crossflow filtration device 55 as in the above-described embodiment.

(6) In the above-described embodiments, a case where a once-through boiler is used as the steam boiler 20 is taken as an example, but the present invention can be similarly implemented even when another type is used as the steam boiler 20. it can.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic of the steam boiler apparatus which can implement the preparation method of the boiler feed water which concerns on one Embodiment of this invention. Schematic of the water softening device used in the steam boiler device. Schematic of the crossflow type filtration apparatus used in the said steam boiler apparatus. The partial cross section schematic of the steam boiler used in the said steam boiler apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steam boiler apparatus 2 Load apparatus 20 Steam boiler 30 Condensate path 32 Condensate tank 40 Reservoir tank 43 Second electrical conductivity sensor 50 Replenishment path 53 Water softening apparatus 55 Cross flow type filtration apparatus 56 Deoxygenation apparatus 57 Hardness sensor 58 First One electrical conductivity sensor 59 Water temperature sensor 60 Flow rate adjusting valve 61 Resin unit group 61a First resin unit 61b Second resin unit 87 Blow control valve

Claims (6)

In order to prepare the boiler feed water from the make-up water in the steam boiler device that supplies and heats the boiler feed water stored in the water storage tank capable of receiving make-up water to the steam boiler and uses the steam generated thereby in the load device The method of
Supplying the makeup water to a crossflow type filtration device using one of a nanofiltration membrane and a reverse osmosis membrane, setting a blow amount from the crossflow filtration device to a predetermined blow amount, and supplying the makeup water Step A for filtration treatment;
Step B for supplying the makeup water filtered in Step A to the water storage tank;
Measuring the electrical conductivity of the makeup water to be supplied to the cross-flow filtration device,
When the electrical conductivity measured in step C exceeds a predetermined value, the amount of blow from the crossflow filtration device in step A is set larger than the predetermined amount of blow.
Preparation method of boiler feed water.   2. The method according to claim 1, further comprising a step D of supplying condensate obtained by condensing the steam used in the load device to the water storage tank and mixing the condensate with the makeup water stored in the water storage tank. Preparation method of boiler feed water.   The process D is a boiler feedwater preparation method according to claim 2, wherein the condensate is stored in a condensate tank, and the condensate stored in the condensate tank is supplied to the water storage tank at a constant rate.   Step D stores the condensate in a condensate tank and measures the electrical conductivity of the makeup water stored in the reservoir tank, and the electrical conductivity of the makeup water stored in the reservoir tank is predetermined. The boiler feed water preparation method according to claim 2, wherein the condensate stored in the condensate tank is supplied to the water storage tank when the value is exceeded.   Filtration treatment in the crossflow filtration device between the step E and the step B in which the hardness component is removed from the makeup water supplied to the crossflow filtration device by ion exchange with a sodium ion exchange resin The boiler feedwater preparation method according to any one of claims 1 to 4, further comprising: a step F of passing the supplied makeup water through a deoxygenation device and removing dissolved oxygen contained in the makeup water. The step E is performed by one resin unit selected from a resin unit group including at least two resin units having the sodium-type cation exchange resin, and the makeup water is passed through the deaerator at a predetermined flow rate. Step F is performed
In step C, the hardness and temperature of the makeup water were measured together, and when the measured hardness exceeded a predetermined value, another resin unit was selected in the resin unit group, and step E was executed and measured. The boiler feed water preparation method according to claim 5, wherein when the water temperature is lower than a predetermined temperature, the makeup water is passed through the deoxygenator at a flow rate lower than the predetermined flow rate in Step F.

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