Device and drying method for preventing columnar lignite specimen from drying out

Abstract

The present invention discloses a device and a drying method for preventing columnar lignite specimens from drying out and cracking, and belongs to the technical field of coal quality analysis. The device includes a cement casting mold, which is used to encapsulate the periphery of the columnar lignite specimen to limit the cement casting area; a demolding device, which is connected to the outer surface of the columnar lignite specimen before casting, and is used to destroy the hardened cement shell encapsulating the outside of the coal specimen after drying; a bottom plate, which is used to support other components of the device; and a cement pad, which is used to block the bottom of the cement casting mold. Drying the columnar lignite specimen using the device disclosed in the present application can maintain the original structure of the columnar lignite specimen to the greatest extent. The coal specimen will not produce large cracks during the drying process, and will not directly break into coal particles, which is convenient for subsequent observation; and the molding process is simple, and the demolding process can also ensure the integrity of the sample. There is no technical difficulty in operation, and it is worthy of popularization and application.

Description

Technical Field

[0001] The invention belongs to the technical field of coal quality analysis, and in particular relates to a device and a drying method for preventing a columnar lignite specimen from drying out and cracking. Background Art

[0002] In the process of developing coalbed methane in lignite reservoirs, quantitative characterization of sample microscopic components and microstructural characteristics is an essential part of the research process. However, to ensure the accuracy of the characterization experimental results, it is necessary to ensure that the columnar coal samples obtained are as consistent with the in-situ characteristics as possible. For example: the columnar lignite samples obtained by water drilling or wire cutting can first obtain grayscale value images through industrial CT scanning. However, when performing threshold segmentation, it is necessary to calibrate the grayscale image through several sections of the original columnar coal sample. Therefore, it is necessary to obtain the original section at a special position of the columnar lignite and observe it under a microscope. For another example: after the permeability test of the columnar lignite sample, it is necessary to perform spatial characteristic analysis on the microscopic components of the columnar lignite. At this time, it is also necessary to obtain the original sections at different positions of the columnar lignite and observe them under a microscope.

[0003] The prerequisite for microscopic observation of lump coal samples is to cast the samples, and the prerequisite for casting is to ensure that the samples are in a dry state. However, for lignite, if the columnar lignite is directly placed in the air for drying or dried using a vacuum drying oven and a blower, a large number of cracks will often be generated in the sample during the dehydration and drying process ( Figure 1 ), even when dried completely, most of the columnar lignite samples will break into small pieces ( Figure 2 ), the broken samples cannot support the subsequent observation of the in-situ coal samples. Even if the samples are not broken into small pieces, the presence of a large number of cracks on the samples makes the observation of the original coal samples meaningless. Therefore, it is necessary to design a device for drying columnar lignite specimens to ensure that the lignite samples can maintain their structural integrity after drying and that no obvious cracks will be produced on the coal specimens. Summary of the invention

[0004] In view of the above-mentioned problems, the present invention aims to provide a device and drying method for preventing columnar lignite specimens from drying out and cracking. Cement is first encapsulated on the outside of the columnar lignite specimen and then the coal specimen is dried. During the slow drying process of the coal specimen, no obvious cracking will occur and the coal specimen will not break into small pieces, thereby maintaining the original structure of the columnar lignite to the greatest extent, which is convenient for subsequent observation.

[0005] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is as follows: a device for preventing columnar lignite specimens from drying out and cracking, comprising: a cement casting mold, used to encapsulate the periphery of the columnar lignite specimen to limit the cement casting area; a demolding device, connected to the outer annular surface of the columnar lignite specimen before casting, used to destroy the hardened cement shell encapsulating the outside of the coal specimen after drying is completed; a base plate, used to support other components of the device; a cement pad, arranged on the base plate, used to seal the bottom of the cement casting mold.

[0006] Furthermore, the cement casting mold includes two semi-annular cement casting rings, namely a first casting ring and a second casting ring connected by a fastening connector, and a compression strip is provided between the matching surfaces of the first / second casting rings.

[0007] Furthermore, as a preference, two groups of demolding devices are provided, each group of demolding devices is assembled from a first demolding member and a second demolding member in a detachable form, the main structures of the first / second demolding members are the same, both comprising a coal sample fixing semi-ring in the middle and demolding lever arms symmetrically located at the free ends on both sides thereof, and threaded grooves are provided on the inner wall surfaces of the demolding lever arms for threaded connection with conical bolts; after the demolding devices are assembled on the outside of the coal specimen, the inner ends of the two demolding lever arms on the corresponding sides of the first / second demolding members are close to each other, and the outer ends are gradually opened back to back to form an open activity area between the two demolding lever arms, and at the same time, the conical bolts connected in the open activity areas on both sides are screwed inwards to change the two relatively arranged demolding members from a connected state to a non-connected state.

[0008] Furthermore, before assembling the demoulding device on the outside of the columnar lignite specimen, a water-permeable insulating material layer needs to be coated on the outside of the coal specimen.

[0009] Furthermore, after the columnar lignite test piece with a demoulder mounted on the outside is placed in the cement casting mold, the outer end of the demoulding arm of the demoulder contacts the inner wall of the cement casting mold.

[0010] Furthermore, a group of fastening connectors are respectively provided at the upper and lower parts of the left open end and the right open end of the first / second casting ring; the fastening connectors include correspondingly arranged first connecting pieces and second connecting pieces, and the correspondingly arranged first / second connecting pieces are provided with threaded holes that pass through the two sides of the connecting pieces. The fastening connectors are assembled and fixed by threading the threaded holes on the correspondingly arranged first / second connecting pieces with connecting screws.

[0011] The method for drying the columnar lignite specimen using the above device is as follows:

[0012] 1) Completely wrap the outer surface of the water-containing columnar lignite specimen (including the annular side, top and bottom surfaces of the columnar lignite specimen) with a permeable isolation material layer;

[0013] 2) The coal sample fixing half rings of the first demoulding member and the second demoulding member are placed on the annular side of the coal sample and fixed detachably; preferably, one set of the two demoulding devices is arranged at the upper third of the height of the columnar lignite sample, and the other set is arranged at the lower third of the height of the coal sample;

[0014] 3) Fill the strippable paste filler in the open active areas on both sides of the demoulder;

[0015] 4) Mix waterproof cement and ordinary cement, add water to prepare cement slurry for pouring. As a preferred method, the mass ratio of waterproof cement to ordinary cement is 1:0.8~1.2, and the water addition ratio is 250 mL of water per kilogram of cement;

[0016] 5) Soak the cement pad in water, fill the compression strip between the matching surfaces of the first / second casting ring, and use the fastening connector to complete the connection of the first / second casting ring;

[0017] 6) Apply a circle of sealing paste on the joint between the bottom of the assembled cement casting mold and the cement pad, and apply a layer of isolation paste on the inner wall of the cement casting mold;

[0018] 7) Place the assembled columnar lignite specimen together with the demoulding device into the cement casting mold;

[0019] 8) Slowly pour the cement slurry mixed in step 4) into the cement casting mold. When pouring, avoid directly impacting the demoulding arm and the open activity area surrounded by it. After pouring, the cement slurry should cover the top of the columnar lignite specimen by 2-3 cm. Place the cast coal specimen in a cool place for 18-24 hours to set.

[0020] 9) Remove the cement casting mold on the outside of the initially finalized cement casting specimen, place the columnar lignite specimen with cement cast on the outside in a cool and dry environment for 40 to 45 days, and then place it in a vacuum drying oven at 60°C for 18 to 30 hours;

[0021] 10) After drying, remove the peelable paste filler in the opening movable area and screw the conical bolts to the thread grooves on both sides of the opening movable area. Screw the conical bolts inward to separate the two corresponding demoulding parts in reverse. The two demoulding parts open in two opposite directions to destroy the cement shell at the height of the demoulding device after being stressed, and then peel off the remaining cast cement;

[0022] 11) The dried columnar lignite specimens were processed using methods including casting and polishing for subsequent observation experiments.

[0023] Furthermore, in step 7), after the columnar lignite specimen is placed into the cement casting mold together with the demoulding device, if there is still a gap between the outer end of the open movable area filled with the peelable paste filler and the inner wall of the cement casting mold, the gap should be filled with the peelable paste filler.

[0024] Furthermore, in step 9), during the drying process in the vacuum drying oven, starting from the 18th hour of drying, the columnar lignite specimens cast with cement are taken out of the drying oven and weighed once every 3 hours. If the difference between the two weights is less than 0.2 g, it is considered that the drying is complete, and the drying process is terminated directly. Otherwise, it is continued to be placed in the vacuum drying oven for drying.

[0025] Furthermore, the peelable paste filler is butter, and the sealing paste and the isolation paste are butter or vaseline.

[0026] The beneficial effects of the present invention are:

[0027] 1. Drying the columnar lignite specimen using the device disclosed in the present application can maintain the original structure of the columnar lignite specimen to the greatest extent. Compared with the treatment method of directly placing the specimen in the air for drying or using a vacuum drying oven, a blower and other equipment for drying, the columnar lignite specimen dried using the device disclosed in the present application will not produce large cracks during the drying process, and will not directly break into coal particles, which is convenient for subsequent observation;

[0028] 2. The present application fixes the demoulding device on the outside of the lignite specimen. When demolding, the conical bolt is inserted into the opening active area and threadedly connected to the thread grooves on both sides, and then continued to be screwed inward to push the two demolding parts outward, so that the two demolding parts change from a connected state to a separated state. The demolding parts are pushed outward, and force is continuously applied to the inside of the cement shell at a corresponding height to achieve the destruction of the encapsulated cement. In the process of demolding by the demolding parts being pushed outward, the stress is only concentrated on the cement poured on the outside of the columnar lignite specimen. Compared with violent demolding methods such as knocking and hammering the externally poured cement, demolding according to this method can avoid the coal specimen from being broken during the demolding process to the greatest extent, and ensure the integrity of the sample during the demolding process.

[0029] 3. In the present application, an insulating material layer is provided between the columnar lignite specimen and the demoulder when the columnar lignite specimen and the demoulder are assembled. The water-permeable insulating material layer not only does not affect the normal drying of the lignite specimen, but also facilitates the demoulding in the later stage, and also prevents the mud from penetrating into the specimen during the cement pouring process and affecting the subsequent test;

[0030] 4. The device for preventing columnar lignite specimens from drying out and cracking disclosed in the present application has a simple structure, low preparation cost, and no technical difficulty in the operation process. The device can be used to quickly encapsulate cement on the outside of the lignite specimen and quickly and efficiently complete the demolding process. It has strong operability and is worthy of promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The diagram is a diagram showing the effect of placing a columnar lignite specimen directly in the air for preliminary drying, wherein the small figure a is a top view of the lignite specimen, and the small figure b is a front view of the lignite specimen;

[0032] Figure 2 This is the effect picture after the columnar lignite specimen is placed directly in the air and completely dried;

[0033] Figure 3 is a top view schematic diagram of a device for preventing a columnar lignite specimen from drying out and cracking in an assembled state;

[0034] Figure 4 It is an axonometric view of the device for preventing the columnar lignite specimen from drying out in the assembled state;

[0035] Figure 5 is an axonometric view of the first demoulding member;

[0036] Figure 6 It is an axonometric view of the demoulder in the assembled state;

[0037] Figure 7 This is a picture showing the effect of using the device disclosed in Example 1 to dry the columnar lignite specimen after it is completely dried;

[0038] Among them, 1-cement casting mold, 2-demolder, 3-base plate, 4-columnar lignite specimen;

[0039] 11-first pouring ring, 12-second pouring ring, 13-fastening connector, 14-pressing rubber strip;

[0040] 131-first connecting piece, 132-second connecting piece, 133-connecting screw;

[0041] 21-upper demoulder, 22-lower demoulder;

[0042] 211-first demoulding member, 212-second demoulding member;

[0043] 2111-coal sample fixing half ring, 2112-demolding arm, 2113-opening movable area, 2114-thread groove, 2115-conical bolt, 2116-plug-in groove. DETAILED DESCRIPTION

[0044] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0045] Example 1

[0046] In order to solve the problem that the conventional drying method causes the columnar lignite specimen to dry out and crack, thereby affecting the subsequent observation of the in-situ coal sample, a device for preventing the columnar lignite specimen from drying out and cracking is disclosed in this embodiment. Figure 3-6 The device includes a cement casting mold 1, a demoulding device 2 and a base plate 3.

[0047] The cement casting mold 1 is used to limit the casting area when casting the sealing cement outside the coal specimen, helping the cement to be better shaped so as to completely encapsulate the columnar lignite specimen inside. It includes two semi-annular and symmetrically arranged cement casting rings, namely the first casting ring 11 and the second casting ring 12, and the first and second casting rings 11 / 12 are spliced ​​and fixed by fastening connectors 13. An array of fastening connectors 13 are correspondingly provided at the open ends on both sides of the first and second casting rings 11 / 12 to achieve the fastening connection of the two casting rings. Preferably, in this embodiment, a group of fastening connectors 13 are respectively provided at the upper and lower parts of the left open end and the right open end of the first and second casting rings 11 / 12 to improve the stability of the first and second casting rings 11 / 12 in the connected state, that is, a total of four groups of fastening connectors 13 are provided on the cement casting mold 1.

[0048] Taking the composition of a fastening connector 13 as an example, its structure is described in detail. The fastening connector 13 includes a first connecting piece 131 and a second connecting piece 132 that are correspondingly arranged. The first connecting piece 131 is fixed to the open end of the first casting ring 11 and is located on its outer side surface. The second connecting piece 132 is fixed to the open end of the second casting ring 12 and is located on its outer side surface. The first and second connecting pieces 131 / 132 are arranged in parallel. The corresponding first and second connecting pieces 131 / 132 are provided with threaded holes that pass through the two sides of the connecting pieces. After the threaded holes on the corresponding first and second connecting pieces 131 / 132 are threadedly connected by connecting screws 133, the assembly and fixation of a fastening connector 13 can be achieved. After assembling four fastening connectors 13, a stable connection between two cement casting rings can be achieved.

[0049] At the connection position of the two cement pouring rings, that is, between the matching surfaces of the first and second pouring rings 11 / 12, a compression strip 14 extending along the height direction of the pouring rings is provided to improve the sealing of the cement pouring ring connection and avoid cement leakage from the connection during cement pouring.

[0050] In order to achieve a better demoulding effect, two sets of demoulding devices are provided in this embodiment, and the demoulding devices are mainly used to destroy the dry cement encapsulated outside the columnar lignite specimen, including an upper demoulding device 21 and a lower demoulding device 22, and each set of demoulding devices is composed of two demoulding parts with the same structure, namely a first demoulding part 211 and a second demoulding part 212.

[0051] The demoulding part includes a coal sample fixing half ring 2111 in the middle and demoulding force arms 2112 symmetrically located at the free ends on both sides thereof. Since the columnar lignite specimen is a standard part, the diameter of the coal sample fixing half ring 2111 can also be directly determined. The first demoulding part 211 and the second demoulding part 212 arranged relatively can be detachably connected together. The detachable connection form is not limited to conventional forms such as plug-in connection and snap-on connection, as long as the connection and fixation of the first and second demoulding parts 211 / 212 and easy disassembly can be achieved. After the correspondingly arranged first and second demoulding parts 211 / 212 are connected and fixed, the two relatively arranged coal sample fixing half rings 2111 are combined into a complete annular fixing ring. When the drying operation is performed, the columnar lignite specimen 4 is placed in the fixing ring, and an isolation material layer is coated on the outside of the coal specimen. The isolation material is wrapped on the outside of the coal specimen mainly to prevent cement from sticking to the coal specimen to facilitate later demoulding, and to prevent cement from invading the inside of the coal specimen and affecting subsequent normal experiments. However, in order not to affect the drying effect, the isolation material layer needs to be water permeable.

[0052] In this embodiment, the first and second demolding members 211 / 212 which are arranged opposite to each other are connected in the form of plug-in connection. Specifically, a plug-in groove 2116 is respectively provided on the two end opening sides of the first demolding member 211, and a plug-in block (not shown in the figure) which is adapted to the plug-in groove 2116 is correspondingly provided on the two end opening sides of the second demolding member 212. After the first and second demolding members 211 / 212 are plug-in spliced ​​through the plug-in groove 2116 and the plug-in block, the inner ends of the two demolding force arms 2112 on the corresponding side of the two demolding members are close to each other, and the outer ends are close to each other. It gradually opens backwards to form an open active area 2113 between the two demoulding lever arms 2112. A threaded groove 2114 is provided on the inner wall surface of the demoulding lever arm 2112. After a conical bolt 2115 with a reduced threaded portion is threadedly connected to the open active areas 2113 on both sides of the demoulding device, the conical bolts 2115 connected in the open active areas 2113 on both sides are screwed inwards at the same time, the two relatively arranged demoulding lever arms 2112 can be separated backwards, that is, the two relatively arranged demoulding parts are changed from a connected state to a non-connected state.

[0053] The main parts of the first and second demolding members 211 / 212 constituting the upper demolding device 21 are symmetrically arranged. Similarly, the main parts of the first and second demolding members 211 / 212 constituting the lower demolding device 22 are also axially symmetrical. Preferably, the symmetry axes of the two demolding members constituting the upper demolding device 21 and the symmetry axes of the two demolding members constituting the lower demolding device 22 are perpendicular to each other (see Figure 1 ), this setting makes it easier to remove the mold later.

[0054] In order to better demould, the assembled and fixed columnar lignite test piece 4 together with the demoulder are placed into the assembled cement casting mold 1 , and then the outer end of the demoulding arm of the demoulder contacts the inner wall of the cement casting mold 1 .

[0055] A cement pad (not shown) is provided on the bottom plate 3. When pouring cement, the cement casting mold 1 is placed on the cement pad. The diameter of the cement pad is larger than the diameter of the cement casting mold 1 to ensure that cement does not leak from the bottom of the mold.

[0056] The process of drying the columnar lignite specimen using the above-mentioned device for preventing the columnar lignite specimen from drying out and cracking is as follows:

[0057] 1) After completing the preliminary experiments, wrap the outer surface of the water-containing columnar lignite specimen with permeable paper to form an isolation material layer (common A4 paper or newspaper used for printing in the laboratory can be used as long as it is permeable) and fasten it with tools such as fine wire to achieve a good isolation effect, which is convenient for later demoulding and ensures that cement will not penetrate into the coal specimen during cement pouring.

[0058] 2) The upper demolding device 21 and the lower demolding device 22 are respectively fixed at the upper third and the lower third of the height of the columnar lignite specimen, that is, the coal sample fixing half rings 2111 of the corresponding first demolding member 211 and the second demolding member 212 are relatively encircled on the annular side of the coal specimen and the demolding devices are fixedly connected by means of a plug-in structure.

[0059] 3) Filling the open movable areas 2113 on both sides of the upper and lower demolders 21 / 22 with peelable paste fillers is intended to prevent cement from seeping into the open movable areas 2113 and solidifying during the later cement pouring, thereby affecting the later demolding. In this embodiment, butter is selected as the filler to fill the open movable areas 2113; preferably, after filling the peelable paste filler, a layer of isolation paper may be covered on the top of the open movable areas 2113 to further prevent cement from falling and collapsing the butter in the open movable areas 2113 or seeping into the area during the cement pouring. In order to minimize the impact on the demolding process, the isolation paper may be selected to be simply adhered to the upper surfaces of the two correspondingly arranged demolding force arms and cover the open movable areas 2113 by the adhesion effect of water after being wetted, instead of being fixed by gluing or the like. This can avoid excessive surface tension of the paper, which may tightly connect the two demolding force arms 2112 and affect the demolding.

[0060] 4) Evenly mix waterproof cement and ordinary cement in a mass ratio of 1:0.8~1.2 (preferably 1:1), add water to the mixed cement at a ratio of 250 mL of water per kilogram of cement to prepare cement slurry.

[0061] 5) The cement pad is soaked in water in advance, and the compression strip 14 is filled between the matching surfaces of the first and second casting rings 11 / 12. The first and second casting rings 11 / 12 are connected by the fastening connector 13, that is, the threaded holes on the corresponding first and second connecting pieces 131 / 132 are threadedly connected by the connecting screws 133 to realize the assembly of the cement casting mold 1.

[0062] 6) Apply a circle of sealing paste (it can be a layer of butter or vaseline) on the joint between the bottom of the assembled cement casting mold 1 and the cement pad, mainly to prevent cement from leaking from the bottom of the mold during pouring; and apply a layer of isolation paste (preferably butter or vaseline) on the inner wall of the cement casting mold 1, mainly to facilitate later demoulding.

[0063] 7) Place the assembled columnar lignite specimen 4 and demoulder 2 into the cement casting mold 1. After placement, the outer end of the demoulding arm 2112 of the demoulder 2 contacts the inner wall of the cement casting mold 1. At this time, if there is still a gap between the outer end of the opening movable area filled with butter and the inner wall of the cement casting mold 1, a certain amount of butter should be filled in the gap to ensure that the entire opening movable area 2113 will not be covered with cement during pouring. After the cement casting mold 1 is dismantled later, the opening movable area 2113 can be completely exposed to facilitate the insertion of the tapered bolt 2115 to complete the demoulding work.

[0064] 8) Slowly pour the cement slurry mixed in step 4) into the cement casting mold 1. When pouring, try to avoid the demoulding arm 2112 and the open activity area 2113 enclosed by it to prevent the cement slurry falling from a high place from washing away the butter in the open activity area 2113. When pouring the cement slurry, try to ensure that the cement slurry in the mold gradually rises in a step-by-step manner, especially wait until the bottom of the open activity area 2113 is flat and filled with cement slurry to provide a certain support for the butter in the open activity area before filling the top of the open activity area with the slurry. This will ensure that the butter filled in the open activity area will not be damaged during the cement pouring process to the greatest extent. Finally, the cement slurry needs to cover the top of the columnar lignite specimen by 2~3 cm, and the cast coal specimen is placed in a cool place for 24 hours to set.

[0065] 9) Repeat the above steps to complete the cement pouring process of multiple columnar lignite specimens 4.

[0066] 10) The cement casting specimens that have been initially shaped are subjected to preliminary demoulding treatment, that is, the four connecting screws 133 are removed, the cement casting mold 1 is removed, and then the columnar lignite specimens 4 with cement cast on the outside are placed in a cool and dry environment for drying for 40 to 45 days, and then placed in a vacuum drying oven at 60°C for drying for 18 to 30 hours (starting from 18 hours, the columnar lignite specimens cast with cement are taken out of the drying oven and weighed once every 3 hours. If the difference between the two weights is less than 0.2 g, it is considered to be completely dried and the drying process can be terminated. Otherwise, it is continued to be placed in the vacuum drying oven for drying. According to tests, the drying time generally does not exceed 30 hours).

[0067] 11) After drying, screw the conical bolts 2115 onto the threaded grooves 2114 on both sides of the opening movable area 2113 (the butter originally applied to the opening movable area 2113 has melted during the heating and drying process, so it only needs to be slightly cleaned when screwing the bolts). Screw the conical bolts 2115 inward to separate the two correspondingly arranged demoulding parts back to back. During the process of the two demoulding parts being separated back to back, force will be continuously applied to the inside of the cement shell at the corresponding height, thereby destroying the encapsulating cement. Since the cement shell cast at the height of the demoulder is impacted and destroyed first, two obvious faults will appear first on the cement shell completely encapsulated on the surface of the coal specimen, and then the cement shell cast and dried in other parts can be easily removed.

[0068] 12) The dried columnar lignite specimen 4 can be used for subsequent observation experiments after being processed by casting glue, polishing, etc.

[0069] Figure 7 This is a diagram showing the effect of completely drying three columnar lignite specimens using the method disclosed in this embodiment. From the diagram, it can be seen that the specimens are not only intact without deformation or breaking into small pieces, but also without obvious cracking, which can support subsequent related observations of in-situ coal samples.

[0070] The above shows and describes the basic principles, main features and advantages of the present invention. However, the above is only a specific embodiment of the present invention, and the technical features of the present invention are not limited thereto. Any other implementation methods derived by any technician in the field without departing from the technical solution of the present invention should be included in the scope of the present invention.

Claims

1. A device for preventing a columnar lignite specimen from drying out and cracking, characterized in that: include: A cement pouring mold, used to enclose the outer periphery of the columnar lignite specimen to define a cement pouring area; A demoulder, connected to the outer annular surface of the columnar lignite specimen before pouring, used to destroy the hardened cement shell encapsulating the outer surface of the coal specimen after drying; The demoulder is assembled from a first demoulder component and a second demoulder component in a detachable form. The main structures of the first and second demoulder components are the same, and both include a coal sample fixing half ring in the middle and demoulder lever arms symmetrically located at the free ends on both sides thereof. A threaded groove is provided on the inner wall surface of the demoulder lever arm for threaded connection with a conical bolt. After the demoulder is assembled on the outside of the coal sample, the inner ends of the two demoulder lever arms on the corresponding side of the first and second demoulder components are close to each other, and the outer ends are gradually opened back to back to form an open activity area between the two demoulder lever arms. At the same time, the conical bolts connected in the open activity areas on both sides are screwed inwards, so that the two relatively arranged demoulder components can be changed from a connected state to a non-connected state. A base plate, used to support other components of the device; The cement pad is placed on the base plate and is used to seal the bottom of the cement pouring mold.

2. A device for preventing a columnar lignite specimen from drying out as claimed in claim 1, characterized in that: The cement casting mold comprises two semi-annular cement casting rings, namely a first casting ring and a second casting ring connected by a fastening connector, and a compression rubber strip is provided between the matching surfaces of the first / second casting rings.

3. A device for preventing a columnar lignite specimen from drying out and cracking as claimed in claim 1, characterized in that: Before assembling the demoulding device on the outside of the columnar lignite specimen, a layer of water-permeable insulating material needs to be coated on the outside of the coal specimen.

4. A device for preventing a columnar lignite specimen from drying out as claimed in claim 1, characterized in that: After the columnar lignite test piece with a demoulding device externally mounted thereon is placed in a cement casting mold, the outer end of the demoulding force arm of the demoulding device contacts the inner wall of the cement casting mold.

5. A device for preventing a columnar lignite specimen from drying out as claimed in claim 2, characterized in that: A group of fastening connectors are respectively provided at the upper and lower parts of the left open end and the right open end of the first and second casting rings; the fastening connectors include correspondingly arranged first connecting pieces and second connecting pieces, and threaded holes penetrating the two sides of the connecting pieces are provided on the correspondingly arranged first / second connecting pieces. The fastening connectors are assembled and fixed by threading the threaded holes on the correspondingly arranged first / second connecting pieces with connecting screws.

6. A drying method for preventing a columnar lignite specimen from drying out and cracking, characterized in that: It is carried out based on the device described in any one of claims 1 to 5, and the specific steps are as follows: A layer of water-permeable isolation material is completely wrapped around the outer surface of the water-containing columnar lignite specimen; The coal sample fixing half rings of the first demoulding member and the second demoulding member which are respectively arranged are put on the annular side surface of the coal test piece and are detachably fixed; Filling the strippable paste-like filler in the open active areas on both sides of the demoulder; Mix waterproof cement and ordinary cement, add water to prepare cement slurry for pouring; Soak the cement pad in water, fill the compression strip between the matching surfaces of the first and second casting rings, and use the fastening connector to complete the connection between the first and second casting rings; Apply a circle of sealing paste on the joint between the bottom of the assembled cement casting mold and the cement pad, and apply a layer of isolation paste on the inner wall of the cement casting mold; Put the assembled columnar lignite specimen together with the demoulding device into the cement casting mold; Slowly pour the cement slurry mixed in step 4) into the cement casting mold, and avoid directly impacting the demoulding arm and the opening activity area surrounded by it when pouring; After pouring, the cement slurry should cover the top of the columnar lignite specimen by 2-3 cm, and the poured coal specimen should be placed in a cool place to set for 18-24 hours; Remove the cement casting mold on the outside of the initially finalized cement casting specimen, place the columnar lignite specimen with cement cast on the outside in a cool and dry environment for 40 to 45 days, and then place it in a vacuum drying oven at 60°C for 18 to 30 hours; After drying, remove the peelable paste filler in the opening active area, screw the conical bolts onto the thread grooves on both sides of the opening active area, screw the conical bolts inward to separate the two corresponding demoulding parts, and open the two demoulding parts in two opposite directions to destroy the cement shell cast at the height of the demoulding device, and then peel off the remaining cast cement; The dried columnar lignite specimens were processed using methods including casting and polishing for subsequent observation experiments.

7. A drying method for preventing a columnar lignite specimen from drying out and cracking as claimed in claim 6, characterized in that: In step 7), after the columnar lignite specimen is placed into the cement casting mold together with the demoulder, if there is still a gap between the outer end of the open movable area filled with the peelable paste filler and the inner wall of the cement casting mold, the gap should be filled with the peelable paste filler.

8. A drying method for preventing a columnar lignite specimen from drying out and cracking as claimed in claim 6, characterized in that: In step 9), during the drying process in the vacuum drying oven, the columnar lignite specimens poured with cement are taken out of the drying oven and weighed once every 3 hours starting from the 18th hour of drying. If the difference between the two weights is less than 0.2 g, it is considered to be completely dried and the drying process is terminated directly. Otherwise, it is continued to be placed in the vacuum drying oven for drying.

9. A drying method for preventing a columnar lignite specimen from drying out and cracking as claimed in claim 6, characterized in that: The peelable paste filler is butter, and the sealing paste and the isolation paste are butter or vaseline.

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