DK180120B1

DK180120B1 - Centrifuge and operating method therefor

Info

Publication number: DK180120B1
Application number: DKPA201800050A
Authority: DK
Inventors: Sano Yuji; Watanabe Yuusuke; Okeya Hisashi
Original assignee: Mitsubishi Heavy Ind Ltd; Japan Engine Corp
Priority date: 2015-07-31
Filing date: 2018-02-01
Publication date: 2020-07-08
Also published as: CN107921446B; DK201800050A1; CN107921446A; KR20180021189A; JP5829352B1; WO2017022529A1; KR102110055B1; JP2017029919A

Abstract

Provided is a centrifuge that, while using a simple configuration, is capable of stabilizing, at a high level, the density of a solid component in waste discharged from a separation chamber of the centrifuge , is capable of reducing the discharge amount of the waste, and is capable of reducing the storage space for the waste. The centrifuge of a separation plate type is provided with a system controller 17 that includes : a memory 17A storing therein a discharge trigger table generated from initial turbidity levels organized into a plurality of groups and a plurality of change in ∆NTU values respectively corresponding to the plurality of groups of initial turbidity levels; and a central processing unit 17B that calculates a discharge reference value at which the solid component S in the separation chamber 15 is to be discharged, on the basis of an initial turbidity level and the change of ∆NTU value corresponding to the initial turbidity level in the discharge trigger table.

Description

DESCRIPTION CENTRIFUGE AND OPERATING METHOD THEREFOR Field

[0001] The present invention relates to a centrifuge used with a flue gas scrubber and an operating method therefor and specifically relates to the centrifuge and the operating method therefor applied to a flue gas scrubber used in a flue gas scrubbing process for diesel engines of marine vessels or the like.

Background

[0002] There are strict environmental regulations about flue gas from diesel engines of marine vessels, among others, so as to strictly regulate discharging SOx and NOx contained in the flue gas. To cope with the regulations, flue gas scrubbing processes have conventionally been performed by using flue gas scrubbers. Scrubbing-purpose water (hereinafter, scrubber water) that circulates in flue gas scrubbers contain particulate matters such as unburned carbons and the like. Accordingly, the particulate matters are separated and removed from the scrubber water, by using a centrifugal separation procedure, for example. When a centrifugal force of a centrifuge is applied thereto, the particulate matters accumulate as a solid component in a part of a separation chamber having the largest diameter (hereinafter, maximum diameter part). Accordingly, the solid component is intermittently discharged to the outside, together with the scrubber water, through a discharge port formed in the maximum diameter part of the separation chamber. Because it is not permitted to directly discard the scrubber water containing the solid component into the ocean, the scrubber water containing the solid component is stored in the marine vessel as waste.

[0003] However, because keeping space for luggage and passengers in marine vessels has a higher priority, there is not much room for sufficiently reserving the space for storing such waste. Accordingly, methods for keeping such waste as little as possible have conventionally been sought for. For example, Japanese National Publication of

International Patent Application No. 2013-527788 describes a technique for keeping waste output from a centrifuge as little as possible. According to this technique, for the purpose of keeping the discharge amount of waste output from the centrifuge as little as possible, the turbidity level of post-processing scrubber water scrubbed by the centrifuge is measured by using a turbidity meter so that, when the measured value exceeds a predetermined threshold value, the accumulated solid component is discharged as waste, from the separation chamber of the centrifuge. In this manner, an endeavor is made to reduce the waste occurring from the centrifuge. In other words, by monitoring the turbidity level of the post-processing scrubber water processed by the centrifuge, the density or the amount of the solid component accumulating in the separation chamber of the centrifuge is monitored. In addition, Japanese National Publication of International

Patent Application No. 2013-527788 also indicates that it is important to keep the amount of waste to a minimum.

[0004] US 6,358,191 B1, US 2010-081552 A1,

DE 10 2013 111 576 A1 and WO 2007/135481 A2 describe centrifuges comprising turbidity sensors for measuring threshold initiating a solid discharge operation. Summary Technical Problem

[0005] However, the content ratio of particulate matters such as unburned carbons in flue gas fluctuates depending on the state of a load on the diesel engines of the marine vessel. Accordingly, the turbidity level of the scrubber water also fluctuates. In other words, because the processing capability of the centrifuge is at a constant level, when the density of the solid component in the scrubber water flowing into the centrifuge is higher, separation efficiency of the centrifuge becomes higher. By contrast, when the density of the solid component in the scrubber water flowing into the centrifuge is lower, separation efficiency of the centrifuge becomes lower. Consequently, the turbidity level of the post-processing scrubber water processed by the centrifuge fluctuates.

Thus, the turbidity levels do not necessarily correspond to the density or the amount of the solid component in the separation chamber. In addition, because the turbidity level of the scrubber water flowing into the centrifuge fluctuates, the time period it takes before the solid component needs to be discharged from the inside of the separation chamber also fluctuates. When the density of the solid component in the separation chamber is high, it will become difficult to discharge the solid component unless the solid component is discharged at an early stage. By contrast, when the density of the solid component in the separation chamber is low, it is necessary to wait until the density becomes high enough.

[0006] According to the method described in Japanese

National Publication of International Patent Application No.

2013-527788 by which the accumulating solid component is discharged from the separation chamber as the waste when the turbidity level of the post-processing scrubber water processed by the centrifuge exceeds the predetermined threshold value, because the density of the solid component in the waste is not stable, problems remain where, when the density of the solid component in the waste is lower, the amount of waste becomes larger, which will require larger storage space. By contrast, when the density of the solid component in the waste is higher, it becomes more difficult to discharge the solid component as waste through the discharge port.

[0007] To solve the problems described above, it is an object of the present invention to provide a centrifuge and an operating method therefor that, by using a simple configuration, are capable of stabilizing, at a high level, the density of the solid component in the waste discharged from the separation chamber of the centrifuge, are capable of reducing the discharge amount of the waste, and are capable of reducing the storage space for the waste.

Solution to Problem

[0008] A centrifuge according to the present invention, under control of a system controller, performs a separating process to separate a solid component from scrubber water by applying a centrifugal force to the scrubber water containing the solid component and being supplied from a flue gas scrubber to an inside of a rotating separation chamber, further measures a turbidity level of the postprocessing scrubber water by using a turbidity meter, and intermittently discharges the solid component as waste from the separation chamber by opening a valve on a basis of a measured value of the turbidity meter. By using the turbidity meter, a first turbidity level is measured as an initial turbidity level with respect to each of a plurality of bodies of scrubber water that are arranged to have mutually-different turbidity levels in advance, immediately after the processing is started on each of the bodies of scrubber water, and when a density of the solid component in the waste discharged from the separation chamber has reached a predetermined density level during follow-up processing performed after the initial turbidity level is measured, a second turbidity level of each of the bodies of scrubber water discharged from the separation chamber is measured, on a basis of the measured values, the system controller calculates a difference ANTU between the second turbidity level and the initial turbidity level with respect to each of the plurality of bodies of scrubber water having the mutually-different initial turbidity levels, also classifies the initial turbidity levels of the plurality of bodies of scrubber water having the mutuallydifferent initial turbidity levels into a plurality of groups according to magnitudes thereof, and generates a discharge trigger table on a basis of the initial turbidity levels organized in the plurality of groups and the ANTU values respectively corresponding to the initial turbidity levels, and the system controller includes a memory storing therein the discharge trigger table, and a central processing unit that calculates, as a discharge reference value, a turbidity level at which the solid component is to be discharged, on a basis of an initial turbidity level of the scrubber water measured by the turbidity meter and the

ANTU value corresponding to the initial turbidity level in the discharge trigger table.

[0009] Further, the discharge reference value is a value obtained by adding together the initial turbidity level and the ANTU value.

[0010] Further, the solid component in the separation chamber is discharged by opening the valve when the turbidity level of the scrubber water discharged from the separation chamber has reached the discharge reference value.

[0011] Further, a centrifuge operating method for operating a centrifuge according to the present invention, under control of a system controller, performs a separating process to separate a solid component from scrubber water by applying a centrifugal force to the scrubber water containing the solid component and being supplied from a flue gas scrubber to an inside of a rotating separation chamber, further measures a turbidity level of the postprocessing scrubber water by using a turbidity meter, and intermittently discharges the solid component as waste from the separation chamber by opening a valve on a basis of a measured value of the turbidity meter. The centrifuge operating method includes an operation preparing step performed on the centrifuge and an operation executing step performed on the centrifuge. The operation preparing step includes steps of measuring a first turbidity level as an initial turbidity level, with respect to each of a plurality of bodies of scrubber water arranged to have mutually-different turbidity levels in advance, immediately after the processing is started on each of the plurality of bodies of scrubber water having the mutually-different turbidity levels, measuring a second turbidity level of each of the plurality of bodies of scrubber water having the mutually-different initial turbidity levels and being discharged from the separation chamber, when a density of the solid component in the waste discharged from the separation chamber has reached a predetermined density level during follow-up processing performed after the initial turbidity level is measured, calculating a difference ÄNTU between the second turbidity level and the initial turbidity level with respect to each of the plurality of bodies of scrubber water having the mutuallydifferent initial turbidity levels, classifying the initial turbidity levels of the plurality of bodies of scrubber water having the mutually-different initial turbidity levels into a plurality of groups according to magnitudes thereof, and generating a discharge trigger table on a basis of the initial turbidity levels organized in the plurality of groups and the ANTU values respectively corresponding to the initial turbidity levels, and configuring the discharge trigger table into the system controller, and the operation executing step includes steps of measuring an initial turbidity level of the scrubber water observed immediately after the separating process is performed thereon, calculating a discharge reference value used for discharging the solid component, on a basis of the initial turbidity level of the scrubber water and the ANTU value corresponding to the initial turbidity level, measuring a later turbidity level of the scrubber water, subsequent to the measuring of the initial turbidity level, and opening the valve when the turbidity level has reached the discharge reference value.

[0012] Further, at the operation preparing step, the

ANTU value is set to a larger value when the initial turbidity level is lower, whereas the ANTU value is set to a smaller value when the initial turbidity level is higher.

[0013] Further, at the operation executing step, a value obtained by adding together the initial turbidity level and the ANTU value corresponding to the initial turbidity level is used as the discharge reference value.

Advantageous Effects of Invention

[0014] According to the present invention, it is possible to provide the centrifuge and the operating method therefor that, by using a simple configuration, are capable of stabilizing, at a high level, the density of the solid component in the waste discharged from the separation chamber of the centrifuge, are capable of reducing the discharge amount of the waste, and are capable of reducing the storage space for the waste.

Brief Description of Drawings [0015] FIG. 1 is a configuration diagram illustrating an embodiment of a centrifuge of the present invention applied to a scrubber.

FIG. 2 is a schematic drawing illustrating a relevant part of the centrifuge illustrated in FIG. 1. Description of Embodiments [0016] The present invention will be explained below, on the basis of an embodiment illustrated in FIGS. 1 and 2.

For example, as illustrated in FIG. 1, a centrifuge 10 according to the embodiment is connected to a flue gas scrubber 30 via a first circulation pipe 40. While scrubber water resulting from a scrubbing process performed by the flue gas scrubber 30 is circulating through the first circulation pipe 40 as pre-processing scrubber water W, a separating process is performed on particulate matters by the centrifuge 10, so that post-processing scrubber water W' is returned to the flue gas scrubber 30 via the first circulation pipe 40. As illustrated in FIG. 1, the first circulation pipe 40 includes a first pipe 41 and a second pipe 42 connected to the first pipe 41. In the present embodiment, a centrifuge of a separation plate type is used as the centrifuge 10. Further, the flue gas scrubber 30 is connected to a diesel engine 50 via a second circulation pipe 60. The flue gas scrubber 30 performs a scrubbing process on flue gas output from the diesel engine 50. The diesel engine 50 is configured to reduce NOx and the like in combustion gas, as a result of sucking in, again, the flue gas made cleaner by the scrubbing process.

[0017] As illustrated in FIG. 1, the centrifuge 10 is provided for second pipe 42 and is configured to apply a centrifugal force to the pre-processing scrubber water W supplied thereto from the first pipe 41, so as to perform the separating process to separate particulate matters derived from the flue gas and contained in the scrubber water W as a solid component and to further return the clean post-processing scrubber water W' to the flue gas scrubber 30. The flue gas scrubber 30 is configured to remove the particulate matters from the flue gas output from the diesel engine 50 via the scrubber water W. In this situation, in FIG. 1, forwarding means such as a pump to circulate the scrubber water W and the flue gas is omitted from the drawing. Further, in the following sections, the scrubber water supplied from the flue gas scrubber 30 to the centrifuge 10 will be referred to as pre-processing scrubber water W. The clean scrubber water

W' resulting from the processing performed by the centrifuge 10 will be referred to as post-processing scrubber water W'.

[0018] As the flue gas scrubber, it is possible to use any of various types of scrubbers that are conventionally and publicly known. For example, as for the flue gas scrubber 30 illustrated in FIG. 1, the pre-processing scrubber water W circulating in the first pipe 41 and the post-processing scrubber water W' output from the centrifuge 10 join each other in the first pipe 41, so that the joined water is sprayed into the flue gas scrubber 30 via a spray nozzle 31 connected to the first pipe 41, so as to catch and remove the particulate matters floating in the flue gas therein. As the flue gas scrubber 30, a scrubber configured to inject the scrubber water W onto a filler and to remove particulate matters by using a liquid film formed on the surface of the filler, or the like, may be used. [0019] Next, the centrifuge 10 according to the present embodiment will further be explained with reference to FIGS.

and 2. To the second pipe 42 of the first circulation pipe 40 for the centrifuge 10, a sampling-purpose pipe 70 that samples the post-processing scrubber water W' is connected. The sampling-purpose pipe 70 is provided with an air separator 71 that performs a bubble removing process on the post-processing scrubber water W'. Further, on the downstream side of the air separator 71 for the samplingpurpose pipe 70, a turbidity meter 72 is provided.

Accordingly, after the air separator 71 has removed bubbles from the post-processing scrubber water W', the turbidity meter 72 is able to measure the turbidity level of the post-processing scrubber water W' with a high level of precision. The turbidity meter 72 detects the turbidity level as an analog signal, so that the analog signal is converted into a digital signal by a system controller 17.

When the turbidity level reaches a certain value (e.g., the discharge reference value explained later), the system controller 17 transmits a signal to a valve opening and closing mechanism, so as to open a discharge port of the centrifuge 10, to discharge a solid component as waste together with the scrubber water, and to have the waste accumulated in a collection tank 80. When the waste stored in the collection tank 80 has reached a predetermined amount, the waste is transferred to another storage location via a pump 81.

[0020] Further, as illustrated in FIG. 2, for example, the centrifuge 10 includes: an inflow pipe 11 into which the flow of the pre-processing scrubber water W output from the flue gas scrubber 30 enters; a rotating drum (not illustrated) of which the upper end is open; a rotating member lid 12 that forms a rotating member as being fitted to the upper-end opening of the rotating drum; a partition plate 13 arranged to have a gap with respect to the inner surface of the rotating member lid 12; a main valve 14 that opens and closes the discharge port (not illustrated) formed in a lateral part of the rotating drum by moving in up-and-down directions as indicated by the arrow while being inserted in the rotating drum; a separation chamber formed between the main valve 14 and the partition plate

13; and a plurality of separation plates 16 that are arranged in the separation chamber 15 so as to be layered on top of one another while having predetermined intervals therebetween in the up-and-down direction. Under control of the system controller 17, the pre-processing scrubber water W is supplied from the inflow pipe 11 to the inside of the separation chamber 15 via a guiding tube 18.

Because the particulate matters have a larger specific gravity than that of the scrubber water, when a centrifugal force is applied within the separation chamber 15, the particulate matters are separated from the scrubber water as a solid component S, by the separation plates 16 as a result of centrifugation. The post-processing scrubber water W' in the separation chamber 15 is discharged to the outside via a centripetal pump 19 and an outflow pipe 20.

In FIG. 2, the post-processing scrubber water W' is in the regions indicated with lighter hatching, whereas the solid component S is in the regions indicated with darker hatching.

[0021] Further, in the separation chamber 15, when the particulate matters are separated from the post-processing scrubber water W' as the solid component S as a result of the centrifugation, the solid component S accumulates in a recessed part including the discharge port (not illustrated) formed in the maximum diameter part of the separation chamber 15. An interface I is formed between the post-processing scrubber water W' and the solid component S. Further, a very small part of the solid component S positioned at the interface I moves in the direction of the arrow, along with the flow of the postprocessing scrubber water W', so as to be discharged to the outside through the outflow pipe 20, while being in a turbid state as being mixed in the post-processing scrubber water W'. It is possible to measure the turbidity level of the post-processing scrubber water W' by using a turbidity meter.

[0022] The centripetal pump 19 is disposed so as to face the interior of a chamber 23 formed at an upper end of the partition plate 13. The centripetal pump 19 is configured to discharge the post-processing scrubber water W' that has overflowed from the separation chamber 15 and is accumulating in the chamber 23. Because the interface I between the solid component S and the post-processing scrubber water W' advances toward the center of the separation chamber 15 over the course of time, it becomes necessary to discharge the solid component S from the separation chamber 15. As a result of opening the discharge port formed in the lateral part of the rotating drum, the solid component S is discharged, as waste, together with a part of the post-processing scrubber water

W' held in the separation chamber 15. When the density of the solid component S in the waste is low, the amount of waste increases. By contrast, when the density of the solid component S is high, it is difficult to discharge the solid component S through the discharge port. Accordingly, when operating the centrifuge 10, it is important to discharge the solid component S without fail by stabilizing the density of the solid component S at a predetermined density level. To cope with this situation, in the present embodiment, a trigger (hereinafter, a discharge trigger) by which the discharge port of the separation chamber 15 is opened is set in advance as appropriate, in accordance with fluctuation of the turbidity level of the pre-processing scrubber water W. With this arrangement, it is possible to discharge a minimum amount of waste without fail, by stabilizing the density of the solid component in the waste.

[0023] An operating method of the centrifuge according to the present embodiment includes: an operation preparing step of preparing various types of data necessary for the operation, such as initial turbidity levels; and an operation executing step of executing the operation by using the data obtained at the operation preparing step. At the operation preparing step, the discharge trigger is set by performing the following procedure: To set the discharge trigger, a plurality of bodies of scrubber water having mutually-different turbidity levels are prepared, each as pre-processing scrubber water W. One of the bodies of pre-processing scrubber water W prepared in advance and having a certain turbidity level is brought subject toa separating process to separate the solid component therefrom by using the centrifuge 10. The turbidity level of the body of post-processing scrubber water W' is measured immediately after the processing is started.In the present invention, the turbidity level measured immediately after the processing is started is definedas an initial turbidity level. During the operation of the centrifuge 10, the initial turbidity level of the body of post-processing scrubber water W' having the certain turbidity level is measured by using the turbidity meter 72. Further, at an appropriate time during follow-up processing performed subsequently, the turbidity level of the postprocessing scrubber water W' is measured as appropriate, and immediately after that, the solid component S is discharged, as waste, from the separation chamber 15 together with the post-processing scrubber water W', and also, the density of the solid component in the waste is measured. The timing with which the turbidity level of the post-processing scrubber water W' is measured is varied as appropriate, so that the measured density value (an analysis value) of the solid component in the waste at a certain time reaches a predetermined density level (e.g., 7 wt%). The turbidity level of the post-processing scrubber water W' at the certain time is measured by using the turbidity meter 72 and is recorded. The difference between the turbidity level of the post-processing scrubber water W' and the initial turbidity level corresponding to the time when the density of the solid component in the waste reaches the predetermined density level (7 wt%) is defined as a turbidity difference (ANTU).

[0024] The initial turbidity level varies among the bodies of pre-processing scrubber water W flowing into the centrifuge 10. Accordingly, with respect to each of the plurality of bodies of pre-processing scrubber water W that are arranged to have the mutually-different turbidity levels in advance, a ANTU value is calculated and recorded from the difference between the initial density thereof and the later turbidity level of the body of post-processing scrubber water W' corresponding to the time when the density of the solid component in the waste reaches the predetermined density level (7 wt%). The abovementioned predetermined density level of the solid component in the waste can be changed as appropriate depending on operation conditions. In this manner, for example, a discharge trigger table illustrated in Table 1 is generated by calculating the initial turbidity levels of the plurality of bodies of pre-processing scrubber water W having the mutually-different turbidity levels and the respective bodies of post-processing scrubber water W', and corresponding ÄNTU values thereof.

[0025] As illustrated in Table 1, the initial turbidity levels of the plurality of bodies of pre-processing scrubber water W that are arranged in advance to be mutually different are measured in the range of 0 to 3,000, for example. Within this range, the initial turbidity levels are divided into sections by increments of 200, for example, so that the range of the initial turbidity levels is divided into a plurality of groups such as 0 to 200, 201 to 400, . . . and 2,801 to 3,000. The total range of the initial turbidity levels and the number of groups thereof can be set as appropriate, on the basis of the operation environment such as an expected turbidity level of the preprocessing scrubber water W, specifications (a measurable range, errors) of the turbidity meter 72, and the like. As illustrated in Table 1, in the present embodiment, the plurality of groups obtained by dividing the range of initial turbidity levels by increments of 200 are written in the top section of the table, whereas ÄNTU values corresponding to the groups of initial turbidity levels are written in the bottom section of the table. In the present embodiment, Table 1 generated in this manner is defined as the discharge trigger table. The discharge trigger table is prepared in advance at the operation preparing step on the basis of measured data such as the turbidity levels and is configured into the system controller 17.

[0026]

Table 1

Initial Turbidity Level	0 to 200 H01	201 to -400 H02	... ...	2,801 to 3,000 H15
ÄNTU	H01T	H02T	...	H15T

[0027] The discharge trigger table generated as illustrated in Table 1 is stored into a memory 17A of the system controller 17 in advance and is used at the operation executing step of the operating method for operating the centrifuge 10 according to the present embodiment. An operator refers to the discharge trigger table illustrated as Table 1. For example, when an initial turbidity level is lower, the operator determines that the amount of the solid component S accumulating at the recessed part in the separation chamber 15 is smaller and arranges a larger ÄNTU value to be assigned in the system controller 17. By contrast, when the initial turbidity level is higher, the operator determines that the amount of the solid component S at the recessed part in the separation chamber 15 is larger and arranges a smaller ÄNTU value to be assigned in the system controller 17.

[0028] When implementing the operating method on the centrifuge, the operator measures the initial turbidity level of the post-processing scrubber water W', either immediately after the operation of the centrifuge 10 is started or immediately after the solid component S is discharged from the centrifuge 10. Subsequently, the operator selects a turbidity difference value ÄNTU corresponding to the measured initial turbidity level from the discharge trigger table stored in the memory 17A of the system controller 17. The operator calculates a discharge reference value (= the initial turbidity level + turbidity difference value ÄNTU) for the solid component S, by using the initial turbidity level and the turbidity difference value ÄNTU, more specifically by adding the ANTU value to the initial turbidity level via a central processing unit

17B of the system controller 17. After that, the operator configures the discharge reference value into the system controller 17. During the operation of the centrifuge 10, the system controller 17 automatically controls the timing with which a valve opening and closing mechanism 25 opens and closes, on the basis of results of comparing the discharge reference value with measured values of the turbidity meter 72. When the measured value of the turbidity meter 72 has reached the discharge reference value, the system controller 17 outputs an open signal to the valve opening and closing mechanism 25. Upon receipt of the open signal, the valve opening and closing mechanism opens a predetermined valve (not illustrated), so as to supply open-valve operation water, to move the main valve 14 downward to open the discharge port of the separation chamber 15, and to discharge the accumulated solid component S toward the collection tank 80. After that, the valve is closed to stop the open-valve operation water.

Subsequently, the valve (not illustrated) operates according to a close signal to supply close-valve operation water, and the main valve 14 is closed to stop the closevalve operation water.

[0029] Next, the operating method for operating the centrifuge 10 according to the present embodiment will be explained.

[0030] First, when flue gas of the diesel engine 50 flows into the flue gas scrubber 30 via an outbound pipe 61 of the second circulation pipe 60, the scrubber water in the flue gas scrubber 30 becomes turbid due to unburned particulate matters in the flue gas mixing into the scrubber water. While the pre-processing scrubber water W output from the flue gas scrubber 30 circulates through the first pipe 41 of the first circulation pipe 40, a part of the scrubber water W is supplied to the centrifuge device 10 via the second pipe 42. In the centrifuge 10, the preprocessing scrubber water W is introduced to the inside of the separation chamber 15 via the inflow pipe 11 and the guiding tube 18 of the centrifuge 10. At this time, because the rotating drum of the centrifuge 10 is rotating at a high speed, a centrifugal force is applied to the preprocessing scrubber water W flowing into the separation chamber 15, so that the particulate matters are separated and accumulate in the recessed part at the maximum diameter part in the separation chamber 15, as the solid component S (see FIG. 2). The post-processing scrubber water W' from which the particulate matters have been separated increases gradually, flows toward the center of the separation chamber 15, and reaches a chamber 23. The post-processing scrubber water W' in the chamber 23 flows to the outside through the outflow pipe 20 due to the operation of the centripetal pump 19. The post-processing scrubber water W' output from the outflow pipe 20 goes through the second pipe 42 and joins, in the first pipe 41, the pre-processing scrubber water W output from the flue gas scrubber 30 and thus returns to the flue gas scrubber 30.

[0031] The post-processing scrubber water W' output from the centrifuge 10 is sampled at a flow rate of 3 L/min, for example, via the sampling-purpose pipe 70 provided for the second pipe 42. The sampled water goes through the air separator 71, where bubbles are removed therefrom. An initial turbidity level of the sampled water from which the bubbles have been removed is measured by the turbidity meter 72. The sampled water of which the initial turbidity level has been measured is discharged into a predetermined tank (not illustrated). The water accumulating in the tank returns to the flue gas scrubber 30 via the first pipe 41.

[0032] As the centrifugation on the pre-processing scrubber water W progresses, the interface I between the solid component S and the post-processing scrubber water W' in the separation chamber 15 gradually advances toward the center of the separation chamber 15. During this time period also, a small portion of the solid component S positioned at the interface I floats off as particulate matters and is discharged to the outside, accompanying the flow of the post-processing scrubber water W'.

[0033] In a while, as the accumulated amount of solid component S increases, the turbidity level of the postprocessing scrubber water W' increases to reach the discharge reference value. At this time, the valve opening and closing mechanism 25 is driven by an open signal output from the system controller 17, so as to open the valve and forwards the open-valve operation water to the main valve

14, and the main valve 14 is thus opened. As a result, the discharge port of the separation chamber 15 is opened, so that the accumulating solid component S is discharged together with the post-processing scrubber water W' and is collected in the collection tank 80. Subsequently, the supply of the open-valve operation water is stopped. After that, the valve is opened due to a close signal from the system controller 17, and the close operation water is forwarded so as to close the main valve 14, and the valve is closed so as to stop the supply of the close-valve operation water.

[0034] The discharge reference value is set by adding together the initial turbidity level and the turbidity difference ÄNTU, as explained above. When the initial turbidity level is higher, a smaller turbidity difference ÄNTU is set. By contrast, when the initial turbidity level is lower, a larger turbidity difference ANTU is set.In other words, by setting the turbidity difference ANTU toan appropriate value varied in accordance with the initial turbidity level of the post-processing scrubber waterW', it is possible to stabilize the density of thesolid component S in the waste discharged from the centrifuge 10 at the predetermined density level (7 wt% in the present embodiment). Accordingly, it is possible to reduce the storage space for the waste.

[0035] As explained above, the present embodiment provides the centrifuge 10 that, under the control of the system controller 17, performs the separating process on the solid component S in the scrubber water W by applying the centrifugal force, in the separation chamber 15, to the pre-processing scrubber water W supplied from the flue gas scrubber 30 to the inside of the centrifuge 10, further measures the turbidity level of the post-processing scrubber water W' by using the turbidity meter 72 while the post-processing scrubber water W' is returning from the separation chamber 15 to the flue gas scrubber 30, and intermittently discharges the solid component S from the inside of the separation chamber 15 by bringing the valve opening and closing mechanism 25 into operation on the basis of the measured value. By using the turbidity meter 72, the first turbidity level is measured as the initial turbidity level with respect to each of the plurality of bodies of pre-processing scrubber water that are arranged to have the mutually-different turbidity levels in advance, immediately after the processing is started on each of the bodies of pre-processing scrubber water W. Also, when the density of the solid component S in the waste discharged from the separation chamber 15 has reached the predetermined density level during the follow-up processing performed after the initial turbidity level is measured, the second turbidity level of each of the bodies of postprocessing scrubber water W' is measured. Further, the system controller 17 calculates the difference ÄNTU between the second turbidity level of each of the bodies of postprocessing scrubber water W' and the initial turbidity level, with respect to each of the plurality of bodies of scrubber water W having the mutually-different turbidity levels. Also, the system controller 17 classifies the initial turbidity levels of the plurality of bodies of scrubber water W having the mutually-different turbidity levels into the plurality of groups in the order of the magnitudes thereof, and generates the discharge trigger table on the basis of the initial turbidity levels organized in the plurality of groups and the ÄNTU values respectively corresponding to the initial turbidity levels. In addition, the system controller 17 includes: the memory

17A storing therein the discharge trigger table; and the central processing unit 17B that calculates the discharge reference value used for discharging the solid component S from the inside of the separation chamber 15, on the basis of the initial turbidity level and the ÄNTU value corresponding to the initial turbidity level in the discharge trigger table. Accordingly, at the operation preparing step, the discharge trigger table is generated, and the discharge reference value based on the discharge trigger table is calculated. Further, at the operation executing step, the turbidity levels of the post-processing scrubber water W' output from the centrifuge 10 are sequentially measured, so as to discharge the solid component S accumulating in the separation chamber 15 at the time when the turbidity level has reached the discharge reference value. With these arrangements, by using the simple configuration, it is possible to stabilize the density of the solid component S in the waste discharged from the centrifuge 10 at the predetermined density level (7 wt% in the present embodiment). Consequently, it is possible to reduce the discharge amount of the waste and to also reduce the storage space for the waste.

[0036] Further, because the system controller 17 has the discharge trigger table, by simply measuring the initial turbidity level of the post-processing scrubber water W' while using the turbidity meter 72, it is possible to set the discharge reference value by selecting an appropriate ANTU value corresponding to the measured initial turbidity level, from within the discharge trigger table.

Consequently, it is possible to stably control the density of the solid component S in the waste at the predetermined density level. Further, it is economical because the centrifuge 10 is sufficiently structured with the simple system configuration.

[0037] The present invention is not, by any means, limited to the embodiments described above. It is possible to apply design changes thereto as appropriate, within the scope of the claims.

Claims

patent claims

A centrifuge which performs a separation process for separating a solid component from scrubbing water by exposing the scrubbing water to a centrifugal force, which scrubbing water contains the solid component and is supplied from a flue gas scrubber to the interior of a rotating separation chamber, and which intermittently discharges the solid component as waste from the separation chamber, which centrifuge comprises:

a turbidity meter which measures a turbidity level of the scrubber water after treatment, and a system controller which opens and closes a valve based on a measured value from the turbidity meter, the turbidity meter measuring a first turbidity level as an initial turbidity level for each of a number of samples of scrubbing water, which is arranged to have different turbidity levels in advance, immediately after the start of the treatment, on each of the samples of scrubbing water and when the density of the solid component in the waste discharged from the separation chamber has reached a predetermined density level during follow-up treatment performed after the initial turbidity level is measured, the turbidity meter measures a different turbidity level for each of the scrubber samples discharged from the separation chamber, the system control on the basis of the measured values calculates a difference ANTU between the second turbidity level and the initial turbidity level,for each of the number of samples of scrubber water having the mutually different initial turbidity levels and also classifying the initial turbidity levels for the number of samples of scrubber water having the mutually different initial turbidity levels into a number of groups according to their orders of magnitude and generating an emission trigger table based on the initial turbidity levels, which are organized into a number of groups, and the respective ANTU values corresponding to the initial turbidity levels, and the system control includes:

a memory which stores the discharge trigger table therein and a central calculation unit which, as a discharge reference value, calculates a turbidity level at which the solid component is to be discharged, based on an initial turbidity level of the scrubber water measured by the turbidity meter and the ANTU value corresponding to the initial turbidity level in the discharge trigger table.

The centrifuge of claim 1, wherein the emission reference value is a value obtained by adding the initial turbidity level and the ANTU value.

A centrifuge according to claim 1 or 2, wherein the solid component in the separation chamber is discharged by opening the valve when the turbidity level of the scrubber water discharged from the separation chamber has reached the discharge reference value.

A method of centrifugal operation for operating a centrifuge which, under the control of a system controller, performs a separation process for separating a solid component from scrubbing water by subjecting the scrubbing water to a centrifugal force, which scrubbing water contains the solid component and is supplied from a flue gas scrubber to the interior of a rotary separation chamber, further measures a turbidity level of the scrubber water after treatment using a turbidity meter and intermittently discharges the solid component as waste from the separation chamber by opening and closing a valve based on a measured value from the turbidity meter, the method of centrifugal operation comprising:

an operational preparatory step performed on the centrifuge and an operational performing step performed on the centrifuge, the operational preparatory step including steps for:

measuring a first level of turbidity as an initial level of turbidity in respect of each of a number of samples of scrubbing water arranged to have mutually different levels of turbidity in advance, immediately after the start of treatment, on each of the number of samples of scrubbing water having the different turbidity levels, measuring a different turbidity level for each of the number of scrubber water samples having the different initial turbidity levels and discharging from the separation chamber when the density of the solid component in the waste discharged from the separation chamber has reached a predetermined density level; during follow-up treatment, which is carried out after the initial turbidity level has been measured, calculation of a difference ANTU between the second turbidity level and the initial turbidity level, for each of the number of samples of scrubber water having the different initial turbidity levels, classification ng the initial turbidity levels for the number of scrubber water samples having the different initial turbidity levels in a number of groups according to their magnitudes and generating an emission trigger table based on the initial turbidity levels organized in the number of groups, and the respective ANTU values corresponding to the initial turbidity levels, and configuring the discharge trigger table in the system control, and the operating step includes steps for:

measuring an initial turbidity level of the scrubber water observed immediately after the separation process is performed thereon, calculating a discharge reference value used to discharge the solid component, based on the initial turbidity level of the scrubber water and the ANTU value corresponding to the initial turbidity level, measuring later turbidity level of the scrubber water, after the measurement of the initial turbidity level, and opening of the valve when the turbidity level has reached the discharge reference value.

The centrifugal operation method according to claim 4, wherein the ANTU value during the preparatory step is set to a larger value when the initial turbidity level is lower, while the ANTU value is set to a smaller value when the initial turbidity level is higher.

A centrifugal operation method according to claim 4 or 5, wherein a value obtained by adding the initial turbidity level and the ANTU value corresponding to the initial turbidity level during the operating step is used as the emission reference value.