JP4873676B2 - Sludge recycling equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technique for reusing sludge drowned from, for example, a river or a marsh lake (in this specification, used as a term including not only sludge but also soil).
[0002]
[Prior art]
For example, sludge dredged from rivers, marshes and underground sewage can be transported and disposed of in a state of high moisture content in order to prevent costs associated with transporting and discarding water and preventing leakage of sewage onto the road. The problem was great.
In addition, a large amount of organic matter contained in the sludge contains various germs, which can cause spoilage odors and other bad odors. Was big.
[0003]
If such a sludge treatment is performed at a dedicated treatment facility, not only the construction cost of the facility but also the costs of the sludge transportation, treatment, waste soil transportation after treatment, etc. become enormous.
[0004]
[Problems to be solved by the invention]
The present invention has been proposed in view of the above-described problems of the prior art, and an object thereof is to provide a technique capable of treating sludge without spending enormous treatment costs.
[0005]
[Means for Solving the Problems]
The sludge recycling apparatus of the present invention is diluted with purified water from a sludge recovery mechanism (A) having a movable dredging vehicle that recovers sludge from rivers and the like, and a fresh water tank (F) that describes the concentration of recovered sludge. The sludge charging tank (B) to be diluted sludge (Y1), the primary dewatering drum screen (C) for primary dewatering of the diluted sludge (Y1), and the flocculant added to the liquid separated by the primary dewatering A chemical liquid agitation line mixer (D), a coagulation sedimentation tank (E) for coagulating and precipitating sludge components in the liquid, a secondary dehydration vacuum dehydrator (G) for secondary dehydration of the precipitated aggregate, and 1 The drum screen type continuous drying furnace (K) for heating and drying the secondary dehydrated sludge and the secondary dehydrated agglomerate and the purified water from the filtrate tank (H) described later are added to the heated and dried sludge for kneading improvement. It is communicated with the kneading conveyor (M) and the coagulation sedimentation tank (E). A fresh water tank (F), a filtrate tank (H) communicated with a secondary dewatering vacuum dehydrator (G) by a line (p8) provided with a vacuum pump (Vp) for extracting filtered water in the sludge, and a drum Cyclone (KC) that drops dust in steam from the screen-type continuous drying furnace (K) and sends purified gas, and an exhaust cleaning tank that cleans the purified gas sent from the cyclone (KC) and exhausts it outside (L), and the primary dewatering drum screen (C), the secondary dewatering vacuum dehydrator (G), the drum screen type continuous drying furnace (K), the kneading conveyor (M), the cyclone (KC), In addition, each tank (B, E, F, H, L) is characterized in that it is movable.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
[0012]
In FIG. 1, a sludge recovery mechanism A composed of a movable sludge recovery line A1 and a dredged vehicle A2 for recovering sludge Y0 precipitated in a sludge source U such as a river is disposed. Dredging vehicle A2 is constituted by dredging device A4 for dripping and storing sludge Y0 and moving vehicle A3 on which dredging device A4 is mounted.
[0013]
The sludge input tank B that stores the sludge Y0 that is input from the sludge recovery mechanism A at any time (for example, various values are shown in an example in which sludge having an average water content of 30% is input in a batch system) is an appropriate place. Are arranged.
[0014]
The sludge charging tank B is equipped with a screen (for example, removing about 5% of dust, glass and rubble with an opening of 20 mm) for removing dust, debris, debris, etc., and the concentration of the introduced sludge from the fresh water tank F described later. The diluted sludge Y1 is diluted with purified water (approximately 5%) to form diluted sludge Y1, and the diluted sludge Y1 is pumped to the primary dewatering means C through the raw water pump and the line p1.
[0015]
The primary dewatering means C includes a drum screen C1 that is rotated by a motor C2 and has little vibration (for example, about 10% of dust and debris are removed with an opening of 0.4 mm), and diluted sludge Y1 from the line p1 in the drum screen C1 It is comprised by the supply body C3 to supply and the container C4 which stores the mud which is the liquid isolate | separated from the drum screen C1 by the primary dehydration.
[0016]
A level detection device m1 for detecting the amount of mud is attached to the container C4.
Sand, debris, etc. are removed to a predetermined size by the drum screen C1, and the low-water-containing sludge Y2 (water content of about 30 to 40%) subjected to primary dehydration is conveyed to a hopper J described later by the belt conveyor Q1. It is configured.
The container C4 is connected to the chemical liquid stirring line mixer D by a line p2 through the flow rate detection device m2.
[0017]
The chemical liquid stirring line mixer D includes an adding device a1 for adding a flocculant such as PAC (polyaluminum chloride: 500 to 1000 PPM), and an adding device a2 for adding a flocculant such as a polymer flocculant solution (2000 to 4000 PPM). It has a function of mixing lines.
Further, the chemical liquid stirring line mixer D is communicated so as to send the mud liquid y0 mixed with the flocculant chemical liquid to a pipe E2 provided at the upper part of the coagulation sedimentation tank (thickener) E through the line p3.
[0018]
Referring also to FIG. 3, the coagulation sedimentation tank E is composed of a pipe E2, a portion E1 for accumulating the supernatant of the mud y0, and a bottom E3 for sedimenting the aggregate y1 from which the mud y0 has settled, and settles on the bottom E3. Concentration detectors m3 and m4 for detecting the amount of liquid are mounted vertically.
The concentration detectors m3 and m4 have a light emitting and receiving device, and are configured to be ON when the concentration of the aqueous solution is higher than a predetermined value by light detection, and OFF when the concentration is lower than the predetermined value. 10 is communicated. Note that the concentration detection device can be applied to, for example, a fish detector using ultrasonic waves.
[0019]
The pipe line of the pipe E2 is opened in the muddy water supernatant of the part E1, and a check valve is provided in the vicinity of the opened part to prevent backflow.
A line p4 for discharging the supernatant liquid (20 to 30 PPM) is attached to the portion E1 and communicated with the fresh water tank F.
[0020]
A line p6 including a slurry pump Pe for pumping the aggregated precipitate y1 is communicated with the bottom of the vacuum dehydrator G at the bottom of the bottom E3.
[0021]
The control device 10 is configured to have an instruction function for turning the pump Pe ON, OFF, forward rotation, or reverse rotation based on signals from the detection devices m3 and m4 and a level detection device m5 described later.
[0022]
The vacuum dehydrator G is a device that performs secondary forced dehydration. The tank body G1 stores the aggregated precipitate y1, and the drum G2 with filter medium with rotation control by an inverter partially immersed in the tank body G1. It consists of The tank body G1 is equipped with a level detection device m5 for detecting the storage depth in order to prevent overflow of the aggregated precipitate y1, and is communicated with the control device 10 by a signal line 15.
The line p6 communicated with the bottom of the tank body G1 is opened in the aggregate in the tank body G1, and a check valve is provided in the vicinity of the opened position to prevent backflow.
[0023]
The drum G2 is porous of about 5 to 10 μm, and the holes are randomly arranged and covered with a filter medium having an opening ratio of about 70%. The inside of the drum G2 is evacuated to adsorb aggregate sludge on the outer periphery. The upper part is connected to the upper part of the filtrate tank H by a line p8 provided with a vacuum pump Vp for extracting the filtered water. In addition, the sludge Y3 of aggregates adsorbed on the outer periphery of the drum is transported to the hopper J via the conveyor Q2 with the moisture content adjusted (about 40 to 60%).
[0024]
The moisture content of the mud Y3 is adjusted by a sensor (not shown) such as a two-color infrared moisture meter and adjusted by adjusting the rotational speed of the drum G2.
The dehydrating device may be a known press type, centrifugal type or the like.
[0025]
Returning to FIG. 1, the filtrate tank H is provided with a line p <b> 9 at the lower part, one branch of the line p <b> 9 communicates with a kneading conveyor M to be described later, and the other branch is piped for cleaning.
[0026]
The hopper J receives the sludge Y2 from the primary dewatering means C and the sludge Y3 from the secondary dewatering means G, and based on the results obtained by the control unit (not shown) for the amount of feed to the continuous drying furnace K in the next process. Then, it is conveyed by the conveyor Q3 so that a certain amount is supplied.
[0027]
The continuous drying furnace K is a rotary furnace in which a drum screen rotates, and has a burner K2. The dried sludge Y5 heated by this burner K2 (300 ° C. to 800 ° C.) and heat-sterilized miscellaneous bacteria, miscellaneous seeds and the like is configured to drop fine particles and coarse particles onto the kneading conveyor M at a high temperature.
The vapor evaporated in the continuous drying furnace K is configured to be sent to the cyclone KC via the line p11. The drying furnace is not limited to a rotary furnace in which the drum screen rotates, and any type may be used as long as the function is guaranteed.
[0028]
The cyclone KC is configured to drop the dust contained in the steam and send the purified gas to the exhaust cleaning tank L via the line p12.
[0029]
The exhaust cleaning tank L is configured to clean the purified gas from the line p12 by adding water sprayed by the slurry pump Pl in the tank and exhaust it to the outside.
[0030]
The kneading conveyor M kneaded and mixed the granulated dry sludge Y5 from the continuous drying furnace K by adding 20% of the filtrate from the line p10 to a strength index CBR value of about 20, and treated soil having moisture adsorption properties. Yf is configured to be accumulated in a predetermined place where it is easy to use.
The treated soil Yf is used for each application by the reuse means R described later.
[0031]
Each of the above devices and means is configured as a movable unit, and can be installed at a convenient place for using the treated soil treated with sludge.
[0032]
FIG. 2 is a flowchart for schematically explaining the operation of the sludge recycling apparatus having the configuration shown in FIG. 1, and FIG. 6 shows the contents to be investigated in advance for the implementation of FIG. For convenience of explanation, the preliminary survey items are first shown by the flowchart of FIG.
[0033]
In step S41, a preliminary survey of soil quality, construction environment, and heavy metals is performed. Step S42 is a design start, and step S43 establishes a construction order, a processing capability, a reuse method, a construction management standard, and a process plan as a construction plan.
[0034]
In step S44, the construction of the preliminary survey is started. Preparatory work, mud collection work, dewatering work. In step S45, the moisture content of the mud is measured by a predetermined method. In step S46, a dry sterilization process for the mud is performed.
[0035]
In step S47, a solute test analysis is performed. If the analysis result indicates that the mud can be reused, it is recycled (step S48). If the result of the analysis indicates that recycling is not possible, the process goes to the final disposal site in step S49, and in step S50, the investigation and selection of the outflow location and the disposal cost design are changed based on the administrative guidance.
After the above preliminary survey, the work shown in the process diagram of FIG. 2 is performed.
[0036]
Configuration of Sludge Recycling Device Referring to FIG. 1, in FIG. 2, in step S1, dredging work is performed from a mud source U such as a river or a marsh lake. In step S2, mud collection work is performed. In step S3, a mud discharge operation is performed by the recovery line A1. Steps S1, 2, and 3 are steps for collecting sludge.
[0037]
In step S6, dust, waste, and debris are removed with a screen in the sludge charging tank B. Of these, non-reusable garbage and waste are disposed of in step S7. The debris is reused in step S16.
[0038]
In step S4, the mud and sludge from which foreign matter has been removed in step S6 is accumulated.
In step S5, a dehydration process is performed by the primary dehydration means C (primary dehydration step).
[0039]
In step S8, a flocculant such as PAC (500 to 1000 PPM) and a polymer flocculant solution (2000 to 4000 PPM) are added from the adding devices a1 and a2 to the liquid y0 separated in the primary dehydration step by the chemical liquid stirring line mixer D. Supply. Then, the mixture is agitated and mixed by the chemical solution agitating line mixer D and fed to the coagulation sedimentation tank E.
In step S10, the stirring mixture is coagulated and precipitated in the coagulation sedimentation tank E.
[0040]
Steps S8, S9, and S10 are steps of adding a flocculant and aggregating and precipitating.
[0041]
In step S11, the coagulated / precipitated supernatant water is extracted. And it discharges to fresh water tank F at Step S14.
In step S12, secondary dehydration is performed by the vacuum dehydrator G (secondary dehydration step).
[0042]
In step S13, the secondary dehydrated filtrate is fed through the line p8, and discharged to the fresh water tank F in step S14.
[0043]
In step S15, a constant amount of the sludge precipitates Y2 and Y3 dehydrated in step S5 and step S12 is supplied using a hopper J, and a dry sterilization process or a heat sterilization process is performed in a continuous drying furnace K. . And it conveys with the kneading conveyor M, and recycle | reuses by step S16.
[0044]
The above steps S1 to S16 are general descriptions of the configuration of FIG. 1, and the functions according to the detailed configuration diagram of the coagulation sedimentation tank E and the vacuum dehydrator G shown in FIG. 5.
[0045]
FIG. 4 shows a method for controlling the operation of the pressure pump Pe and the secondary dehydration vacuum dehydrator G according to the amount of sludge y1 precipitated in the coagulation settling tank E.
In step S21, it is confirmed whether the densitometer m3 is “ON”, that is, whether the sediment determined by the concentration has reached the upper predetermined position of the bottom E3. If not reached (NO), wait until the amount of precipitation increases. If it has reached (YES), the process proceeds to step S22 and the pump Pe and the dehydrator G are operated.
[0046]
In step S23, it is confirmed whether or not the densitometer m4 is in the “OFF” state, that is, whether or not the precipitate is not at the lower predetermined position of the bottom E3. If the precipitate is not in the lower predetermined position (NO), the precipitate still remains at the bottom E3, so step S22 is continued and the operation of the pump Pe and the vacuum dehydrator G is continued. If the deposit is at the lower predetermined position (YES), the operation of the pump Pe is stopped in step S24.
[0047]
In step S25, it is confirmed by time that the elapsed time after the operation of the pump Pe is stopped for a predetermined time or more and the precipitate sent to the vacuum dehydrator G is dehydrated. If the predetermined time has not elapsed (NO), it waits until the predetermined time elapses. If the predetermined time has elapsed (YES), the vacuum dehydrator G is stopped in step S26.
In this way, the vacuum dehydrator G is always operated effectively in a loaded state without idling.
[0048]
FIG. 5 shows a method of performing a more precise operation in order to avoid a state in which sludge is left in the dehydrator G. In particular, when the vacuum dehydrator G is stopped, a method is shown in which the dewatered untreated sludge in the line P6 is returned to the coagulation sedimentation tank E and stored.
In step S31, it is checked whether the densitometer m3 is “ON”, that is, whether the precipitate determined by the concentration has reached the upper predetermined position of the bottom E3. If not reached (NO), wait until the amount of precipitation increases. If it has reached (YES), the process proceeds to step S32 and the pump Pe and the vacuum dehydrator G are operated.
[0049]
In step S33, it is confirmed whether the densitometer m4 is in the “OFF” state, that is, whether the precipitate is not in the lower predetermined position of the bottom E3. If the deposit is not in the lower predetermined position (NO), the precipitate still remains at the bottom E3, so step S32 is continued and the operation of the pump Pe and the vacuum dehydrator G is continued. If the deposit is at the lower predetermined position (YES), the operation of the dehydrator G is stopped in step S34.
[0050]
In step S35, the pump Pe is reversed.
In step S36, it is confirmed whether untreated sludge in the line P6 has flowed back to the sedimentation tank E. If the backflow is not completed (NO), the backflow is continued. If the reverse flow is completed (YES), the pump Pe is stopped in step S37.
[0051]
In this way, the sludge in the line p6 is returned and stored in the coagulation sedimentation tank E so that it is not left untreated.
[0052]
FIG. 7 shows a second embodiment in which the first embodiment is simplified. With reference to the first embodiment, mainly the parts different from the first embodiment, the sludge treatment amount, the chemical solution addition amount, etc. will be described by omitting the numerical display on the premise of the same amount as the first embodiment. .
[0053]
In FIG. 7, a sludge recovery mechanism A0 is disposed by a movable sludge recovery line A1 interposed with a pump Pa that recovers sludge Y0 settled in a sludge source U such as a river.
[0054]
The sludge Y0 introduced from the sludge recovery mechanism A0 as needed is arranged to be pumped to the primary dewatering means C.
[0055]
The primary dewatering means C includes a drum screen C1 that is rotated by a motor C2, a supply body C3 that supplies sludge Y0 through the line A1 into the drum screen C1, and a container C4 that stores mud dropped from the drum screen C1. It consists of
[0056]
Sand, debris, etc. are removed to a predetermined size by the drum screen C1, and the dehydrated low water sludge Y2 is configured to be conveyed to a continuous drying furnace K described later by a belt conveyor Q1.
The container C4 is communicated with the chemical liquid stirring line mixer D by the line p21.
[0057]
The chemical liquid agitation line mixer D includes an addition device a1 for adding a flocculant, for example, PAC, and an addition device a2 for adding a flocculant, for example, a polymer flocculant solution, and has a function of performing line mixing. Yes.
Further, the chemical liquid stirring line mixer D is communicated so as to send the muddy water y0 mixed with the flocculant chemical liquid to the pipe E2 provided in the upper part of the coagulation sedimentation tank E through the line p3.
[0058]
The coagulation sedimentation tank E is composed of a pipe E2, a part E1 for storing the supernatant of the muddy water y0, and a bottom E3 for sedimenting the muddy water y0.
The pipe line of the pipe E2 is opened in the muddy water supernatant of the part E1, and a check valve is provided in the vicinity of the opened part to prevent backflow.
[0059]
A line p4 for discharging the supernatant liquid is attached to the part E1, and is configured to be discharged into a river or the like.
A line p6 having a slurry pump Pe for pumping the precipitate y1 is communicated with the bottom of the vacuum dehydrator G at the bottom of the bottom E3.
[0060]
The vacuum dehydrator G is a device that performs the second forced dehydration, and includes a tank body G1 that stores the precipitate y1 and a drum G3 with a filter medium that is partially immersed in the tank body G1. The line p6 communicated with the bottom of the tank body G1 is opened to the sludge in the tank body G1, that is, the sediment y1, and a check valve is provided in the vicinity of the opened position to prevent backflow.
[0061]
The drum G3 is porous of about 5 to 10 μm, and the holes are randomly arranged and the inside of the drum G3 covered with a filter medium having an opening ratio of about 70% is evacuated to adsorb sludge to the outer periphery, and filter the sludge. It is configured to be discharged to an external river or the like by a line p8 provided with a vacuum pump Vp for extracting moisture. Further, the sludge Y3 adsorbed on the outer periphery is transported to the continuous drying furnace K via the conveyor Q2 with the moisture content adjusted.
[0062]
The moisture content is adjusted by determining the moisture content with a sensor (not shown) such as a two-color infrared moisture meter and adjusting the rotational speed of the drum G7.
The dehydration method may be a known press method, centrifugal method, or the like.
[0063]
The continuous drying furnace K is a rotary furnace in which a drum screen rotates, and has a burner K2. The dried sludge Y5 heated by the burner K2 and subjected to heat sterilization treatment of germs, seeds and the like is configured to drop fine particles and coarse particles onto the kneading conveyor M at a high temperature. The steam is configured to be supplied to the cyclone KC through the line p11. The drying furnace K is not limited to a rotary furnace in which the drum screen rotates, and any type may be used as long as the function is guaranteed.
[0064]
The cyclone KC is configured to drop dust contained in the steam and release the purified gas to the atmosphere.
[0065]
The conveyor Ma is configured such that the granulated dry sludge Y5 from the continuous drying furnace K is kneaded and mixed by watering to form treated soil Yfd, which is collected at a predetermined place where it can be used easily.
The treated soil Yfd is used for each application by the reuse means R described later.
[0066]
Each of the above devices and means is configured as a movable unit, and can be installed in a convenient place for using the treated soil treated with sludge.
[0067]
The operation of the sludge recycling apparatus according to the configuration of the second embodiment is obtained by simplifying the work steps in the first embodiment, and is almost the same work as an outline. Further, the contents to be investigated in advance for the implementation of this work are the same as the prior investigation items in the flowchart of FIG. 6 in the first embodiment.
[0068]
8 to 10 show examples related to the reuse of the treated soil Yf or Yfd.
FIG. 8 shows an example in which the treated soil Yf or Yfd is applied to the greening method. The reuse device R includes a tire excavator R1, a hopper R2, a conveyor R3, a weighing hopper R4, a conveyor R5, and a spraying machine. The processing soil Yf or Yfd is put into the hopper R2 by the tire shovel R1 and conveyed to the weighing hopper R4 by the conveyor R3.
Next, an appropriate amount of the greening seed Rs is mixed on the conveyor R5 and sprayed onto the slope N of the river Rv by the sprayer R6 and the universal pipe R7. The treated soil Yf or Yfd can be used while dredging.
As a result, the plant can be sterilized and planted by a specific plant that does not generate pests, has no odor, and does not contain other seeds.
[0069]
FIG. 9 shows an example in which the treated soil Yf or Yfd is applied to the backfilling of a structure (for example, a pipe Pk). The reusable device RA includes a shovel R11 and a pipe Pk newly or refilled again. Between the sheet piles Rp, the processing soils Yf and Yfd are loaded with the shovel R11. The treated soils Yf and Yfd have a high CBR value, have appropriate water absorption and water retention, have little shrinkage and expansion, and avoid breakage of the pipe Pk due to volume change.
[0070]
FIG. 10 shows an example in which the treated soil Yf or Yfd is applied as an embankment for residential land / road creation. The reuse device RB includes an excavator R11, and the treated soil Yf and Yfd are used for the embankment Ry1 for the slope. The land and road can be constructed while dredging using the treated soils Yf and Yfd for the topsoil Ry2.
[0071]
【Effect of the invention】
The effects of the present invention are listed below.
(1) According to the present invention, the sludge recovery mechanism, the primary dewatering means, the coagulation / sedimentation means, the aggregate heating means, the kneading means, the reuse device, etc. are all configured to be movable. Work can be performed in parallel with the construction, and the cost including transportation of treated soil can be reduced.
(2) The treated soil has strength and water retention due to sterilization, heating, and kneading, so it can be used freely for embankment, banking for bank revetment work, building land and roads, and backfilling structures.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a first embodiment of the present invention.
FIG. 2 is a (process) flowchart showing the operation of FIG. 1;
FIG. 3 is a configuration diagram showing details of the coagulation sedimentation tank and vacuum dehydrator of FIG. 1;
FIG. 4 is a flowchart showing the operation of FIG. 3;
FIG. 5 is a flowchart showing another operation of FIG. 3;
FIG. 6 is a flowchart showing a preparatory work prior to implementing the first and second embodiments.
FIG. 7 is a configuration diagram showing a second embodiment of the present invention.
FIG. 8 is a diagram showing an example in which treated soil is used for a dam greening method.
FIG. 9 is a diagram showing an example in which treated soil is used for backfilling a structure.
FIG. 10 is a diagram showing an example in which treated soil is used for residential land / road creation.
[Explanation of symbols]
A ... Sludge recovery mechanism B ... Sludge input tank C ... Primary dehydration means D ... Chemical liquid stirring line mixer E ... Coagulation sedimentation tank F ... Fresh water tank G ... (secondary Dehydration means) Vacuum dehydrator H ... Filtrate tank J ... Constant feed hopper K ... Continuous drying furnace M ... Kneading conveyor R ... Reuse device

Claims (1)

  Diluted sludge recovery mechanism (A) with a movable dredging vehicle that collects sludge in rivers, etc., and purified water from a fresh water tank (F) that will be described later to make diluted sludge (Y1) A mud charging tank (B), a primary dewatering drum screen (C) for primary dewatering of the diluted sludge (Y1), and a chemical liquid stirring line mixer (D) for adding a flocculant to the liquid separated by the primary dewatering A coagulation sedimentation tank (E) for coagulating and precipitating the sludge components in the liquid, a secondary dehydration vacuum dehydrator (G) for secondary dehydration of the precipitated aggregate, and the primary dewatered sludge and secondary dehydration A drum screen type continuous drying furnace (K) for heating and drying the agglomerated material, a kneading conveyor (M) for improving kneading by adding purified water from a filtrate tank (H) described later to the heat-dried sludge, and coagulation precipitation Fresh water tank (F) communicated with tank (E) and secondary dehydration A filtrate tank (H) communicated by a line (p8) with a vacuum pump (Vp) for extracting filtered water in the sludge to an empty dehydrator (G), and a drum screen type continuous drying furnace (K) A cyclone (KC) that drops dust in the vapor and sends purified gas; and an exhaust cleaning tank (L) that cleans the purified gas sent from the cyclone (KC) and exhausts it to the outside. Primary dewatering drum screen (C), secondary dewatering vacuum dehydrator (G), drum screen type continuous drying furnace (K), kneading conveyor (M), cyclone (KC), and each tank (B, E, F, A sludge recycling apparatus characterized in that all of H, L) are movable.

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