JP6628046B2 - Cleaning method of plate heat exchanger - Google Patents

Description

  The present invention requires a plate-type heat exchanger used for cooling high-temperature water containing pollutants, for example, when supplying low-temperature water generated in a coke oven to an activated sludge treatment facility as a purification facility. The present invention relates to a method for cleaning a plate heat exchanger suitable for cooling to a suitable temperature.

  Since the low-temperature water generated from the coke oven contains organic substances and nitrogen compounds such as tar generated when carbonizing the coal, in order to discharge the low-water, the organic substances and nitrogen compounds such as tar are preliminarily removed. It is necessary to purify and remove it, and for that purpose, a purification treatment by activated sludge treatment is performed.

  Since such activated sludge treatment is biological treatment, it is necessary to perform the treatment at a predetermined temperature with high treatment efficiency. However, since the low-temperature water generated from the coke oven has a temperature of about 70 ° C., it is cooled. Therefore, it is necessary to lower the temperature to about 40 ° C.

  Generally, a plate-type heat exchanger is used for cooling the low-temperature water. In this plate heat exchanger, a plurality of corrugated plates are stacked to form a two-system flow path therebetween, and a high-temperature medium (high heat medium) and a low-temperature medium (low heat medium) are formed in the flow paths, respectively. Heat is exchanged from the high-temperature medium to the low-temperature medium through the plate by alternately flowing the high-temperature medium and the low-temperature medium is industrial water to cool the low-temperature water. ing.

  By the way, the low-water content contains a small amount of high-viscosity tar and coke powder, and as the plate-type heat exchanger continues to be used, the tar and coke powder are deposited on the surface of the heat transfer plate. In some cases, the flow path is narrowed due to accumulation and the pressure loss increases before and after the plate heat exchanger (outlet side, inlet side).

  If this pressure loss is left large, not only does the load of the pump, which is an ancillary facility of the plate heat exchanger, increase, but also the cooling treatment amount of the water decreases, which is not preferable. When the pressure loss increases, it is necessary to clean the inside of the plate heat exchanger.

  Usually, in order to clean the plate heat exchanger, stop supplying the low-temperature water, remove the plate from the heat exchanger, open it, perform jet cleaning (in some cases, take the plate out of the system for cleaning), and clean the packing. Since the procedure of replacement and assembly of the plate is performed, the cost involved is high and the construction period requires one week or more.

  And when the reserve base of the plate heat exchanger is not possessed, the operation during this period is performed because the high-temperature low-temperature water is supplied to the activated sludge treatment facility. Temperature rise occurs.

  Normally, the washing operation is performed in winter, when there is almost no effect even if the temperature of the treated water rises. If the washing operation must be performed in summer, the temperature of the treated water should rise for about two weeks. Therefore, there is a possibility that the processing capacity of the entire facility is reduced.

  In addition, a decrease in the processing capacity of the equipment not only causes a stoppage of the coke oven operation, but also inevitably adversely affects the sea area where the treated water is discharged if the quality of the treated water deteriorates.

  As a prior art relating to this point, for example, in Patent Document 1, a cleaning liquid is injected into a liquid flow path (high-temperature chamber) of a plate heat exchanger, and compressed air is blown while holding the cleaning liquid. A cleaning method has been proposed in which the cleaning liquid is air-bubbled and the level of the cleaning liquid is changed.

  Patent Document 2 proposes a cleaning method in which high-temperature water is supplied in a pulsated manner, or a plate-type heat exchanger itself is vibrated to vibrate a plate to perform cleaning.

JP-A-9-264698 JP 2005-221109 A

  However, the technique disclosed in Patent Document 1 requires an additional facility for injecting the cleaning liquid and blowing compressed air, and also has an adverse effect on the low-water treatment of the cleaning liquid and the sea area from which it is discharged. Is concerned.

  In addition, when the technique proposed in Patent Document 2 is applied to an existing plate heat exchanger, it is necessary to add equipment for causing pulsation and equipment for mechanically applying vibration, Further, there is a problem that the vibration may cause a crack of the plate, a leakage of the packing part, and the like.

  An object of the present invention is to provide a cleaning method that can remove deposits deposited in a flow path for flowing a high-temperature medium in a short time, and easily and inexpensively. In use, a method for cleaning a plate heat exchanger that can minimize the effect on activated sludge treatment is proposed.

  According to the present invention, by stacking a plurality of heat transfer plates, forming two flow paths between the stacked heat transfer plates, and alternately flowing a high-temperature medium and a low-temperature medium through the respective flow paths. For a plate heat exchanger that performs heat exchange, in the method for cleaning the flow path of the high-temperature medium, the flow of the high-temperature medium is stopped after the flow of the low-temperature medium is stopped and the pressure of the flow path is released. A method for cleaning a plate-type heat exchanger, characterized in that it is increased to at least 1.2 times that of a normal operation and held for 15 minutes or more.

  In the present invention having the above-described configuration, the upper limit of the flow rate of the high-temperature medium is preferably 1.7 times the steady-state operation, and the holding time thereof is preferably 20 minutes or less.

In addition, the inlet pressure of the high-temperature medium flow path and / or the differential pressure of the outlet side of the high-temperature medium flow path are managed, and cleaning is started when the inlet pressure and the differential pressure exceed the control values. thing,
Further, after the washing of the flow path of the high-temperature medium is completed, the flow rate of the high-temperature medium is returned to the flow rate in the normal operation, and the flow of the low-temperature medium is restarted to reduce the flow rate of the low-temperature medium in the normal operation. Is preferable as a specific means for solving the problem.

  According to the present invention, it is possible to remove deposits that have accumulated in the circulation path while the high-temperature medium is kept flowing, that is, without removing the heat transfer plate, so that the time required for cleaning can be reduced. It becomes. Further, since the inside of the distribution channel is washed using a high-temperature medium which is normally distributed, it is not necessary to perform a special discharge process or the like.

It is an external appearance perspective view of a plate type heat exchanger. FIG. 2 is an external perspective view illustrating a disassembled state of the plate heat exchanger illustrated in FIG. 1. It is the figure which showed typically the flow which processes the low water generated from a coke oven using activated sludge processing equipment.

Hereinafter, the present invention will be described more specifically with reference to the drawings.
FIG. 1 is a diagram schematically showing an external perspective view of a plate-type heat exchanger suitable for use in carrying out the purification method of the present invention, and FIG. 2 is a diagram showing the plate-type heat exchanger shown in FIG. It is the external appearance perspective view which showed typically in the disassembled state. As shown in FIG. 3, for example, such a plate-type heat exchanger is installed on the inlet side of an activated sludge facility (comprising a warming tank, a sedimentation tank, a coagulation sedimentation tank, a sand filtration tank, an activated carbon adsorption tank, etc.). Then, prior to feeding the low-temperature water generated in the coke oven to the activated sludge facility for treatment, the low-temperature water is used for cooling to a desired temperature (about 40 ° C.) in advance.

  First, the specific structure of the plate heat exchanger used in the embodiment of the present invention will be described. 1 and 2, reference numeral 1 denotes a fixed frame, 2 denotes a moving frame, and 3 denotes a heat exchanger body disposed between the fixed frame 1 and the moving frame 2. The heat exchanger body 3 is formed by laminating a plurality of heat transfer plates 3a, 3b,... 3n, for example, having a plurality of corrugations formed on the surface thereof in a side-by-side state, and has two flow paths (high-temperature medium) therebetween. The distribution path for distribution is indicated by the symbol M, and the distribution path for low-temperature medium distribution is indicated by the symbol N (liquid tightness between the heat transfer plates 3a, 3b... 3n). A seal member such as a packing for holding the liquid is arranged to maintain a liquid-tight state, but a detailed structure is not shown in the drawings). Are exchanged with each other for heat exchange.

  Here, that the two systems of the flow paths M and N are alternately formed means that the flow path M of the high-temperature medium is formed at one overlapping position at an arbitrary position of the heat transfer plates 3a, 3b,. 3n, a flow path N of the low-temperature medium is formed in the overlapping portion of the heat transfer plates 3a, 3b... 3n, and this arrangement pattern is formed from the beginning of the stacked portion of the heat transfer plates 3a, 3b. It means that it is repeated to the end.

  The heat transfer plates 3a, 3b,..., 3n are actually suspended and held by a pair of upper and lower guide bars extending between the fixed frame 1 and the moving frame 2 (the guide bars are not shown). 1 and the moving frame 2 so as to be integrated. In order to hold the heat transfer plates 3a, 3b... 3n between the fixed frame 1 and the moving frame 2, a plurality of fastening means (fastening bolts) provided at predetermined intervals around the fixed frame 1 and the moving frame 2 are used. Nuts) are used.

  Reference numeral 4 denotes a supply pipe for supplying a high-temperature medium to the heat exchanger main body 3, 5 denotes a discharge pipe for discharging the high-temperature medium from the heat exchanger main body 3, and 6 denotes a low-temperature medium to the heat exchanger main body 3. A supply pipe, 7 is a discharge pipe for discharging the low-temperature medium from the heat exchanger main body 3, 8 is a valve provided in the supply pipe 6 for discharging the low-temperature medium in the flow path N from the heat exchanger main body 3, and 9 a is a supply pipe A pressure gauge 9b provided in the pipe 4 is a pressure gauge provided in the discharge pipe 5, and a valve 10 provided in the discharge pipe 7 to release the pressure of the circulation path N.

  In the plate-type heat exchanger having such a configuration, the high-temperature medium supplied from the supply pipe 4 is discharged from the discharge pipe 5 through the flow path M of the heat exchanger body 3 while the high-temperature medium is discharged from the discharge pipe 5. The supplied low-temperature medium, such as industrial water, is discharged from the discharge pipe 7 through the flow path N of the heat exchanger body 3, and at this time, via the heat transfer plates 3a, 3b,. Heat exchange takes place.

  As a premise for carrying out the present invention, the plate heat exchanger performs an operation (steady (normal) operation) with a processing amount of about 60 to 80% of its maximum processing capacity (expected temperature fluctuation on the high temperature medium side, etc. Generally, operation with such a margin is performed.)

  Then, in the operation of the plate heat exchanger, the cleaning of the plate heat exchanger is started when the pressure by the pressure gauge 9a, that is, the pressure on the inlet side of the flow path of the high-temperature medium exceeds the control value.

  In order to wash the plate heat exchanger, first, the flow of the low-temperature medium is stopped, and the valve 10 is opened to open the pressure in the flow path N of the low-temperature medium.

  Here, the open state refers to a state in which the supply of the low-temperature medium is stopped (stationary state) and the pressure in the circulation path N is reduced. At this time, if the low temperature medium can be extracted from the heat exchanger body 3 through the valve 8, the inside of the circulation path N may be emptied.

  Thereafter, the flow rate of the high-temperature medium is increased to at least 1.2 times that of the normal operation and maintained for 15 minutes or more.

  The heat transfer plates 3a, 3b... 3n are pressed from the high-temperature medium side to the low-temperature medium side, and are slightly slightly increased by increasing the flow rate of the high-temperature medium at least 1.2 times the steady-state operation and holding it for 15 minutes or more. Movement, the space (gap) of the distribution channel M expands. As a result, the deposits adhering to the heat transfer plates 3a, 3b... 3n float. At the same time, since the flow velocity of the high-temperature medium is also increased, the sediment that has floated is flushed toward the discharge pipe 5.

  In the present invention, it is desirable that the upper limit of the flow rate of the high-temperature medium is 1.7 times the normal operation in consideration of the strength of the heat transfer plates 3a, 3b... 3n and the prevention of breakage of the sealing member. It is desirable that the holding time of the time be within 20 minutes. In the present invention, the upper limit of the holding time during washing is desirably within 20 minutes, because the effect reaches a saturated state even if washing is performed even if it exceeds 20 minutes.

  After the washing of the flow path M of the high-temperature medium is completed, the flow rate of the high-temperature medium is returned to the flow rate in the normal operation, and the flow of the low-temperature medium is resumed to reduce the flow rate of the low-temperature medium to the flow rate in the normal operation. I just need to put it back.

  The cleaning of the plate heat exchanger can be started when the value of the pressure gauge 9a exceeds the control value. However, the pressure difference between the inlet and outlet of the flow path M of the high-temperature medium is measured by the pressure gauge 9a. , 9b, and the pressure difference may exceed the control value, or may be controlled by both the inlet pressure of the high-temperature medium and the differential pressure, and this point is not particularly limited.

Heat transfer area: 28.8 m ² , heat exchange capacity: 1,628 kw, maximum treatment capacity: 50 t / h (speed: 0. 0 m) in order to feed the low-temperature water (temperature 70 ° C) generated in the coke oven to the activated sludge treatment. The operation of cooling to 40 ° C. using a plate heat exchanger as shown in FIGS. 1 and 2 at 28 m / sec) was carried out at 60% of the maximum processing capacity (using industrial water as a cooling medium). When the inlet pressure of the supply pipe supplying the low-pressure water is 250 kPa or more and the pressure difference between the inlet pressure of the supply pipe and the output pressure of the discharge pipe becomes 150 kPa or more, the plate-type heat exchanger is washed. Started.

  The washing of the plate heat exchanger was performed after the circulation of the cooling medium was stopped and the inside of the circulation path was emptied to confirm that the inlet pressure was zero. When the operation was resumed after the washing was completed, the cooling water was cooled under the same conditions as before the washing.

  The results are shown in Table 1 together with the washing conditions (flow rate, flow rate, and washing time of the low-temperature water during washing). Whether or not the cleaning was effectively performed was determined based on whether or not the differential pressure between the inlet pressure and the outlet pressure of the supply pipe of the high-temperature medium became 50 kPa or less.

  As is clear from Table 1, when washing the plate heat exchanger, the flow rate of the low-temperature water is set to 1.2 to 1.7 times (36 to 50 t / h) 30 t / h of the normal operation (applicable example). In 1-4), it was found that the differential pressure after cleaning was 50 kPa or less.

  On the other hand, when the cleaning was performed with the flow rate of the low-temperature water being the same as that during the steady operation (Comparative Example 1), the differential pressure after the cleaning was extremely high at 105 kPa, and sufficient cleaning was performed. However, in the case where the flow rate of the low-temperature water was further reduced to 20 t / h (Comparative Example 2), almost no cleaning was performed even if the cleaning time was extended to 20 minutes.

  From these results, it was found that the low pressure medium flow path / pressure was released, and that the low-temperature medium was used in an amount of 36 to 50 t / h, which is 1.2 to 1.7 times higher than that of 30 t / h during steady operation (flow rate 0.20 to 0 .28 m / sec), it was confirmed that the sediment (blockage) can be removed without stopping the low-temperature water, which is the high-temperature medium of the plate heat exchanger.

  ADVANTAGE OF THE INVENTION According to this invention, the washing | cleaning method of the plate-type heat exchanger which can remove the deposit which accumulate | stored in the distribution channel which distribute | circulates a high-temperature medium in a short time, easily and inexpensively can be provided.

DESCRIPTION OF SYMBOLS 1 Fixed frame 2 Moving frame 3 Heat exchanger main body 3a ... 3n Heat transfer plate 4 High temperature medium supply pipe 5 High temperature medium discharge pipe 6 Low temperature medium supply pipe 7 Low temperature medium discharge pipe 8 Valve 9a, 9b Pressure gauge 10 Valve

Claims (4)

Heat exchange is performed by stacking a plurality of heat transfer plates, forming two systems of flow paths between the stacked heat transfer plates, and alternately flowing a high-temperature medium and a low-temperature medium through the flow paths. For a plate heat exchanger, in the method of cleaning the flow path of the high-temperature medium,
After the flow of the low-temperature medium is stopped and the pressure of the flow path is released, the flow rate of the high-temperature medium is increased to at least 1.2 times that in the normal operation and maintained for 15 minutes or more. Cleaning method for plate heat exchanger.   2. The method for cleaning a plate-type heat exchanger according to claim 1, wherein the flow rate of the high-temperature medium is increased up to 1.7 times the normal operation time, and the holding time is set within 20 minutes.   Managing the inlet-side pressure of the high-temperature medium flow path and / or the inlet-outlet pressure difference of the high-temperature medium flow path, and starting the cleaning when the inlet pressure exceeds the control value. The method for cleaning a plate heat exchanger according to claim 1 or 2, wherein:   After the washing of the flow path of the high-temperature medium is completed, the flow rate of the high-temperature medium is returned to the flow rate in the normal operation, and the flow of the low-temperature medium is restarted to reduce the flow rate of the low-temperature medium in the normal operation. The method for cleaning a plate-type heat exchanger according to any one of claims 1 to 3, wherein

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