JPS6036828B2 - Condensate treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a condensate treatment method for removing impurities present in condensate in order to prevent scale formation and corrosion in boilers and turbines.

Generally, in a condensate desalination device, a mixture of H type of strongly acidic ion exchange resin and OH type of strongly basic anion exchange resin is used, and when the cation exchange resin is saturated with ammonia in the condensate, The other is the NH3 cycle treatment method, in which the treatment continues using the resin that has been replaced with ammonia even after the cationic exchange resin has been overcome by the ammonia in the condensate. There is a way.

Recently, many companies have adopted condensate treatment using the NH3 cycle, which requires less frequency of regeneration, in order to save regeneration chemicals for condensate desalination equipment and to improve operational management. However, the operation of the NH3 cycle is subject to various limitations different from those of the H cycle, and there are drawbacks such as the equipment being complicated and regeneration taking a long time, so it cannot necessarily be said that it is a perfected technology. The current situation is that there is no such thing. Conventionally done NH3
In the cycle, ammonia in the demineralization tower inflow is not adsorbed and removed in the demineralization tower and is contained in the outflow water as it is, so if impurities remain in the resin packed in the demineralization tower after regeneration, These impurities react with ammonia in the condensate, causing the impurities to separate from the resin, which is then transferred to the treated water.
This will deteriorate the quality of treated water.

For example, when regenerating an anion exchange resin with caustic soda, some of the intestinal ion exchange resin comes into contact with the caustic soda and becomes Na.
An example of this is when Na reacts with ammonia in the condensate during the water flow process, causing Na to leak into the treated water. Methods to reduce this sodium leakage include passing slaked lime solution and using ammonia water, but both use special chemicals and require a long time for regeneration. There was a drawback. The present invention aims to eliminate the drawbacks of these conventional condensate desalination methods and provide an effective treatment method for stably obtaining treated water of extremely high purity not only in H cycle but also in NH3 cycle operation. There is.

Another object of the present invention is to provide an effective treatment method and device that can significantly reduce the amount of regenerant in a condensate desalination device and facilitate maintenance.

The present invention treats high-pressure boiler condensate using a condensate treatment device consisting of a pre-coat furnace filter and a hot bed type ion exchange resin tower,
In the method for removing dissolved solids and suspended solids in condensate, when treating condensate containing a large amount of suspended solids such as when starting a boiler, the condensate may be treated with powdered cellulose, powdered synthetic fibers, or powdered synthetic fibers. One type of non-ion-exchange powder furnace auxiliary material such as powdered activated carbon, or a mixture of several types of these furnace auxiliary materials, or water can be passed through a pre-coated furnace filtration machine pre-coated in multiple layers to remove suspended water in condensate. After removing most of the turbid substances, granular H-type strongly acidic cation exchange resin and OH
The water is treated by being passed in series to a hot bed type desalination tower filled with a mixture of strongly basic anion exchange resins.

The main component of suspended solids contained in condensate at the time of boiler startup is iron oxide, and more than 50% of them are precoated with one type of non-ion exchange furnace additive. More preferably, it is removed by filtration.
The removal rate of suspended solids is improved by a precoat layer that combines several types of furnace auxiliary materials. The type of precoat filter is not particularly limited, and any type consisting of a commonly used tubular element or a leaf-shaped precoat support can be used. Powdered ion exchange resin can also be used as the pre-coating furnace filter aid, but when treating condensate containing a large amount of suspended solids, the increase in differential pressure in the furnace filter frequently causes The pre-coat furnace overlayer must be renewed, and it is difficult to say that it is economical to re-pre-coat with expensive powdered ion exchange resin each time, so the present invention takes this point into account when starting up the boiler. The pre-coat filtration method uses a non-ion-exchange powder auxiliary as the auxiliary material for the pre-coat filtration machine, and when there are few suspended solids in the condensate as in normal times, a pre-coat filtration method in which powdered ion-exchange resin is pre-coated is used. This makes it possible to obtain high-quality treated water economically.

After the boiler is started, the purity of the condensate flowing into the desalination equipment gradually increases as time passes, and while both suspended solids and dissolved solids decrease, the operation returns to normal operation. In normal times, the precoat layer of the precoat furnace is composed of a mixture of powdered cationic and anionic exchange resins at the bottom of the layer, and the upper layer is the non-ion exchange furnace. Condensate is treated through the precoat layer as a multilayer precoat layer precoated with a filtering agent, and when the precoat furnace filtration effluent satisfies the boiler feed water standard water quality,
Water flow to the hotbed desalination tower filled with granular ion exchange resin is stopped. In this case, by configuring the pre-coating filter in a multi-layer structure during normal operation, the amount of pre-coating of powdered ionized resin can be reduced to 0.2 to 0.5 k9/force, which is less than the conventional 1'2. . It is sufficient that the pre-coat amount of non-ion exchange furnace retirement aid is 0.5 to 1.0 kg/
If the pressure drop increases significantly due to water flow time and turbidity replenishment,
A method is adopted in which the differential pressure is kept low by body-feeding a non-ion-exchange furnace additive to the precoat layer intermittently at appropriate times. By using the ion form of the powdered ion exchange resin, the cation exchange resin is in the H form or the N ratio form, and the anion exchange resin is in the OH form.
Even in 3 cycles, good treated water can be obtained. If a condenser leakage accident is detected by detecting an increase in the cation conductivity or sodium concentration of the inflow water to the desalination tower, for example, the boiler condensate, the outflow water from the pre-coat furnace filtration machine should be immediately transferred to the hotbed desalination tower. The granular ion-exchange resin layer removes impurities that cannot be adsorbed and removed by the pre-coat furnace layer alone by passing water through it. On the other hand, the resin in the hot bed demineralization tower is always in H type and OH type.
Since it is on standby in the ionized form, even in the event of a major condenser accident, condensate treatment can be continued with sufficient margin. One embodiment of the present invention will be described with reference to the drawings. A precoating furnace 1 and a hotbed desalination tower 3
In the condensate treatment equipment, a precoat filter 1 having a precoat layer 2 and a hotbed desalination tower 3 having a hotbed resin layer 4 are connected through a piping route with an on-off valve. Precoat material dissolving tanks 5 and 6 are provided in at least one of the piping routes in association with the precoat filter 1, and the inflow and outflow routes between the precoat filter 1 and the hotbed desalination tower 3 are provided. Desalination equipment inflow condensate water quality monitoring meter Mi, precoating furnace filtration machine outflow water quality monitoring meter Mc
, is equipped with a water quality monitoring meter Me for the effluent water of the hotbed type desalination tower.

7 is a pre-coat material circulation pump, 21 is a pre-coat material slurry hawk machine, 8, 9, 10, 11, 12, 13, 14, 1
5, 16, 17, 18, 19, and 20 each indicate a valve.

Generally, in a condensate desalination apparatus, it is common to divide the water to be treated into a plurality of treatment apparatuses and pass the water through the treatment apparatuses. Similarly, the method of the present invention has a plurality of processing sequences, but only one sequence is illustrated here, and the other sequences are omitted. When the boiler is started, condensate passes through the desalination equipment inflow condensate water quality monitor Mi, passes through the inflow water valve 8, and is introduced into the precoating furnace filtration machine 1.The condensate passes through the non-ion exchange furnace filter aid layer 2 After the suspended solids are removed by the overaction of the adsorption furnace, the water quality is continuously checked by a water quality monitor Mc, and the water is introduced into the hotbed desalination tower 3 through valves 9 and 10. After final polishing in the hot bed type resin layer 4 inside the desalination tower, the conductivity, sodium concentration, etc. of the water effluent from the desalination tower are checked by a water quality monitor Me, and then the water is led out of the system via a valve 11.

When the boiler is started, the suspended solids concentration can be as low as several tens of hours per night, and as high as several thousand hours per hour. If condensate containing such a large amount of turbidity is introduced directly into the hotbed tower, the resin in the tower will be contaminated with turbidity, and the hotbed resin layer must be frequently regenerated. , a large amount of washing water and chemicals are required, and regeneration takes a long time, so in order to deal with this, the water flows into the condensate treatment equipment through a pre-coating furnace process before the hotbed desalination tower 3. Most of the suspended solids are separated and removed in the precoating furnace filtration process, and the load on the hotbed desalination tower 3 is significantly reduced. When the differential pressure of the precoat filter 1 exceeds a set value during the boiler startup period, valves 8 and 9 are closed, valve 13 is opened, and the inflow condensate is passed directly to the hotbed desalination tower for treatment.
During this time, valves 14 and 15 are opened, and the precoat cake is peeled off by pressurized water introduced from valve 14 and discharged to the outside of the tank via valve 15, and then valves 14 and 15 are closed. Then,
Open the valves 17, 20, and 16, and operate the circulation pump 7 to circulate the slurry-like precoat furnace auxiliary material suspended in the precoat material dissolving tank 5 to the precoat layer support. to form a precoat layer. 2 pre-coat layers
In the case of a multilayer furnace material consisting of more than one type of furnace material, the precoat layer can be similarly formed using the precoat material dissolving tank 6. When the pre-coating process is finished, valve 1
7, 20, 16 are closed, pump 7 is stopped, valves 8, 9 are opened, and at the same time valve 13 is closed, and condensate is introduced into precoat filter 1 again. During the precoating operation, the condensate is directly passed to the hot bed type demineralization tower 3, so that the condensate treatment can be carried out continuously without interruption. Moreover, since the amount of suspended solids brought into the hot bed type demineralization tower 3 during this period is relatively small, the extent to which the resin in the demineralization tower 3 is contaminated by the suspended solids is negligibly small. Note that when the water quality of the demineralization tower inflow water and the furnace filtrate reaches the set value by the inflow condensate water quality monitor Mi and the furnace filtration machine effluent water quality monitor Mc, the precoat layer 2 of the precoat furnace filtration machine 1 is turned off. Changed from a pre-coat layer with only ion exchange properties to an Enoki-type furnace layer made of powdered ion exchange resin and non-ion exchange furnace additive.

The operation can be carried out in the same manner as the pre-coating operation described above. First, when powdering, a slurry in which an anionic phase resin is mixed and suspended in water is pre-coated on a pre-coated support, and then the upper layer is coated on the pre-coated support. Pre-coat with non-ion exchange furnace additive. After the precoating is completed, the condensate is passed through the precoating furnace filtration machine 1, and after confirming that the furnace filtrate satisfies the boiler water supply standard value using the furnace filtration machine effluent water quality monitor Mc, the valve 12 is opened, and the valve 12 is opened. 10 and 11 are closed to bypass the hotbed demineralization tower and proceed to normal operation.
During normal operation, when the differential pressure in the pre-coating furnace 1 increases, the non-ion exchange furnace auxiliary material suspended and stored in the pre-coating material dissolving tank 5 is intermittently added to the condensate. Perform precoat filtration while adding. It is considered that the so-called body feed method is adopted to alleviate the increase in pressure drop in the pre-coat filtration machine 1, to extend the operating time of the pre-coat filtration machine as long as possible, and to reduce the consumption of powder ion exchange ≠ sword resin. ing. In addition, when an increase in dissolved solids is detected in the inflow condensate by the desalination equipment inflow condensate water quality monitor Mi, the valve 12 is immediately closed and the valves 10 and 11 are opened to remove the pre-coating furnace filtration machine outflow water from hot bed demineralization. Water is passed in series to the salt tower 3 for treatment.

According to the method of the present invention, the hotbed desalination tower is used only in abnormal situations such as when the condenser leaks or when the boiler is started, so the frequency of regeneration is low, and furthermore, the H-type and OH-type mixed resin is on standby. As the treated water becomes pure water, it is possible to deal with large-scale condenser leakage accidents.Moreover, hotbed resin regeneration can be done using an in-column method or an external regeneration device. Thus, it can be carried out in the same manner as in the conventional H cycle condensate desalination apparatus.

Moreover, it can be operated without any special chemicals required for the NH3 cycle. As described above, according to the method of the present invention, when there are many impurities in the condensate, such as at the time of starting a boiler or when a condenser leaks, the fat layer is By serial treatment, and by treatment with a multilayer pre-coat layer of powdered ion exchange resin and non-ion exchange furnace additive, which is mainly composed of iron oxide, which contains condensate impurities. The amount of regenerating chemicals in the water desalination equipment can be drastically reduced, making operation and maintenance easier, and eliminating the shortcomings of conventional condensate desalination methods, resulting in extremely high purity treatment not only in H cycle but also in NQ cycle operation. It is a stable source of water.

[Brief explanation of the drawing]

The drawing is a system explanatory diagram showing one embodiment of the present invention. 1... Precoat filter, 2... Precoat layer, 3... Hotbed desalination tower, 4... Hotbed resin layer, 5, 6...・Precoat material dissolution tank, 7・
...Precoat material circulation pump, 8, 9, 10, 1
1, 12, 13, 14, 15, 16, 17, 18, 19
, 20... Valve, 21... Fly Azusa machine, Mi...
...Inflow condensate water quality monitoring meter, Mc... Precoat furnace filtration machine effluent water quality monitoring meter, Me...Hotbed type desalination tower effluent water quality monitoring meter.

Claims (1)

[Scope of Claims] 1. In a condensate treatment process in which boiler condensate is passed through a precoat filter and a hot bed desalination tower to remove impurities in the condensate, when the boiler is started, the condensate is mixed with powdered natural fibers, synthetic fibers, etc. The water is passed through a pre-coated filter machine pre-coated with one or more of non-ion exchange powder filter aids such as fibers and powdered activated carbon, and is then passed through a pre-coat filtration process to form a granular H-type filter. The water is passed in series to a hotbed demineralization tower filled with a mixture of ion exchange resin particles of ion exchange resin and OH type anion exchange resin, and the inflow condensate has a low concentration of dissolved solids. Sometimes condensate is treated by a precoat filter alone, which consists of a multilayer precoat layer in which the non-ion exchange filter aid is precoated on top of a precoat layer precoated with powdered cation exchange resin and powdered anion exchange resin. A condensate treatment method characterized in that by detecting an increase in dissolved solids in the condensate flowing into the condensate to be treated, the effluent from the precoat filter is passed through a hotbed desalination tower to desalinate the condensate. . 2. The condensate treatment method according to claim 1, wherein the pre-coat filtration step intermittently body-feeds the non-ion exchange filter aid by increasing the differential pressure of the pre-coat filter.