A low rank coal hot solvent extraction upgrading process

Abstract

A low-rank coal hot extraction upgrading process, organic solvent and low-rank coal are mixed with a mass ratio of 12:1 to prepare pulp and preheat, then are sent into a continuous extractor to carry out extraction; extraction steam is separated from extraction mixed liquid, after flash evaporation of the extraction mixed liquid, extraction agent mixed liquid A and extract mixed liquid A are obtained; after hot centrifugation and filtration of the extract mixed liquid A, solid upgraded coal and extract mixed liquid B are obtained; after rectification of the extract mixed liquid B, ash-free coal and extraction agent mixed liquid B are obtained; after decantation of the extraction agent mixed liquid A and the extraction agent mixed liquid B, extraction agent mixed liquid C and water are obtained; the extraction agent mixed liquid C is mixed with organic solvent to obtain mixed solvent; the mixed solvent and low-rank coal repeat the above process to carry out hot extraction upgrading. The present application does not need to separate the extract and the solvent by precipitating the extract at a low temperature, avoids repeated temperature rising and falling of the solvent in the recycling process, and causes energy waste.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of low-rank coal upgrading process, in particular to a low-rank coal hot solvent extraction upgrading process. BACKGROUND

[0002] Coal occupies an important position in the energy structure of our country, among which the reserves of low-rank coal (including lignite, long flame coal, weakly caking coal and non-caking coal) are abundant, accounting for about 45.7% of China's proven coal reserves. With the rapid consumption of high-quality coal (such as bituminous coal), low-rank coal will become one of the main energy forms in China for a long time, but at present its utilization mode is low in efficiency, large in pollutant and carbon dioxide emissions. Because there are many difficulties in the utilization of low-rank coal: such as high moisture content (25%-70%), high oxygen content (15%-30%) and low carbon content (60%-75%), these shortcomings lead to low transportation efficiency, low calorific value and it is difficult to be directly applied to traditional processes. Therefore, it is of great significance to realize the upgrading of low-rank coal and develop a reasonable utilization mode of low-rank coal.

[0003] Patent document CN201710769336.8 discloses a low-rank coal hot solvent extraction upgrading method, which extracts and upgrades low-rank coal with hot solvent to obtain high molecular weight extract solution and low molecular weight extract solution; then takes the low molecular weight extract solution as the organic solvent for the next extraction experiment to carry out cyclic extraction experiment, and takes the obtained high molecular weight extract as the target product, so that the above steps are repeated to carry out multiple cyclic extraction experiments. This method mainly uses low molecular weight extract solution as organic solvent for cyclic extraction to reduce the consumption of organic solvent, but this method is an intermittent hot solvent extraction method, which needs to heat the extraction solvent from room temperature to 330-360℃ and then cool it to room temperature, and this process is continuously cycled. The energy consumption is high and the efficiency is low during the cyclic process. Moreover, this patent only introduces the core method of hot solvent extraction, and does not propose a complete process, for example, it does not mention residue recovery, solvent and water separation, etc. In addition, this method adopts hot filtration separation, which has the problems of blockage and low efficiency.

[0004] Patent document CN201480054927.1 discloses a method for manufacturing ash-free coal, which discloses a solvent mainly composed of a liquid bicyclic aromatic compound at room temperature, added with a coal extraction promoter having 2 benzene rings and having at least one cyclic structure without double bond, and containing no nitrogen. The invention also discloses a method for manufacturing ash-free coal using the above solvent, but this method uses a gravity settling tank for solid-liquid separation, which has low separation efficiency.

[0005] In addition, in the existing low-rank coal hot solvent extraction process, the separation of the extract and the extractant, and the purification of the extract are usually treated by three steps of adsorption alkali removal, hot filtration macromolecule removal and flash evaporation, which is complex, high in energy consumption and low in efficiency. Due to the high water content of the low-rank coal, the water in the coal enters the circulating solvent in the process of the low-rank coal hot solvent extraction, resulting in the decrease of the quality of the circulating solvent. SUMMARY

[0006] To solve the defects of the low efficiency, high energy consumption and the decrease of the quality of the circulating solvent in the separation of the residue and the extract, the separation of the extract and the extractant and the purification of the extract in the existing low-rank coal hot solvent extraction upgrading process, the present application provides a low-rank coal hot solvent extraction upgrading process, which aims to realize the separation of the residue and the extract by flash evaporation and hot centrifugal separation, realize the separation of the extract and the solvent and the purification of the extract by rectification process, and realize the separation of the circulating solvent and water by decantation process, so as to reduce the energy consumption of the low-rank coal hot solvent extraction upgrading process and improve the process efficiency.

[0007] To achieve the above-mentioned purpose, the present application provides a low-rank coal hot solvent extraction upgrading process, which comprises the following steps:

[0008] The organic solvent and the low-rank coal are mixed at a mass ratio of 12:1, preheated and then sent into a continuous extractor for extraction;

[0009] The extraction steam is separated from the extraction mixed liquid, and the extraction mixed liquid is flash evaporated to obtain an extractant mixed liquid A and an extract mixed liquid A;

[0010] The extract mixed liquid A is obtained by hot centrifugal separation and filtration of the extract mixed liquid A;

[0011] The extract mixed liquid B is obtained by rectification of the extract mixed liquid B;

[0012] The extractant mixed liquid C and water are obtained by decantation of the extractant mixed liquid A and the extractant mixed liquid B;

[0013] The mixed solvent is obtained by mixing the extractant mixed liquid C and the organic solvent;

[0014] The mixed solvent and the low-rank coal are repeatedly subjected to the above process for hot solvent extraction upgrading.

[0015] Preferably, the preheating temperature is 340 DEG C.

[0016] Preferably, the extraction temperature is 335 DEG C-350 DEG C.

[0017] Preferably, the extraction steam is subjected to combustion treatment.

[0018] Overall, compared with the prior art, the above technical scheme conceived by the present application can achieve the following beneficial effects.

[0019] 1. The low-rank coal hot-solvent extraction upgrading process realizes the separation of the extract and the solvent by using a rectification process, without the need to separate the extract and the solvent by precipitating the extract by reducing the temperature, thereby avoiding repeated temperature rising and falling of the solvent in the recycling process, and causing energy waste.

[0020] 2. The low-rank coal hot-solvent extraction upgrading process relates to low-rank coal with a moisture content of 25%-70%, and the present application realizes the separation of the circulating solvent and the moisture by using a decantation process, avoids the moisture in the coal from entering the solvent to reduce the solvent concentration, reduces the solvent extraction effect, and at the same time, more solvent must be put in to achieve the extraction effect, thereby increasing the system power consumption.

[0021] 3. The low-rank coal hot-solvent extraction upgrading process realizes the rapid separation of the residue and the extract by using flash evaporation and thermal centrifugal separation, and the separation efficiency is higher than that of the sedimentation method. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present application will be described below in a clear and complete manner. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0023] In the description of the present application, it should be noted that the terms "top", "bottom", "one side", "the other side", "front", "back", "middle part", "inside", "top end", "bottom end" and the like indicate the orientation or positional relationship, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application; the terms "first", "second", "third" are only for the purpose of description, and cannot be understood as indicating or implying relative importance; in addition, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting" should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be the communication between two elements inside. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0024] Example 1

[0025] The organic solvent (1-methylnaphthalene) is mixed with the coal of Dannaohu in a mass ratio of 12:1 to prepare a coal slurry, the coal slurry is preheated to 340°C and then fed into a continuous extractor to perform extraction, the temperature of the extractor is kept between 335°C and 350°C, and the extraction is performed for 50-60 minutes; after the extraction is completed, the extraction steam is separated from the extraction mixture, the extraction steam is combusted, the extraction mixture is flashed to obtain an extraction solvent mixture A and an extract mixture A; the extract mixture A is subjected to hot centrifugation and filtration to obtain solid upgraded coal and an extract mixture B; the extract mixture B is subjected to rectification to obtain ash-free coal and an extraction solvent mixture B; the extraction solvent mixture A and the extraction solvent mixture B are subjected to decantation to obtain an extraction solvent mixture C and water; the extraction solvent mixture C is mixed with the organic solvent to obtain a mixed solvent; the mixed solvent and the low-rank coal are subjected to the above process to perform hot solvent extraction and upgrading, and the temperature of the mixed solvent is 95-98°C. After the above process is repeated twice, the ash-free coal is taken as a target product, the extraction yield of the ash-free coal is 12.6%, the carbon content is 78.91%, the nitrogen content is 1.45%, and the oxygen content is 14.12%.

[0026] Example 2

[0027] The organic solvent (1-methylnaphthalene) is mixed with the coal of Dannaohu in a mass ratio of 12:1 to prepare a coal slurry, the coal slurry is preheated to 340°C and then fed into a continuous extractor to perform extraction, the temperature of the extractor is kept between 335°C and 350°C, and the extraction is performed for 50-60 minutes; after the extraction is completed, the extraction steam is separated from the extraction mixture, the extraction steam is combusted, the extraction mixture is flashed to obtain an extraction solvent mixture A and an extract mixture A; the extract mixture A is subjected to hot centrifugation and filtration to obtain solid upgraded coal and an extract mixture B; the extract mixture B is subjected to rectification to obtain ash-free coal and an extraction solvent mixture B; the extraction solvent mixture A and the extraction solvent mixture B are subjected to decantation to obtain an extraction solvent mixture C and water; the extraction solvent mixture C is mixed with the organic solvent to obtain a mixed solvent; the mixed solvent and the low-rank coal are subjected to the above process to perform hot solvent extraction and upgrading, and the temperature of the mixed solvent is 95-98°C. After the above process is repeated twice, the ash-free coal is taken as a target product, the extraction yield of the ash-free coal is 12.6%, the carbon content is 78.91%, the nitrogen content is 1.45%, and the oxygen content is 14.12%.

[0028] Example 3

[0029] The organic solvent (tetrahydro naphthalene) is mixed with the Danelu coal at a mass ratio of 12:1 to prepare a coal slurry, the coal slurry is preheated to 340℃ and then sent into a continuous extractor to perform extraction, the temperature of the extractor is kept between 335℃-350℃, and the extraction is performed for 50-60 minutes; after the extraction is completed, the extraction steam is separated from the extraction mixture, the extraction steam is introduced into a combustion device for combustion treatment, the extraction mixture is flashed to obtain an extraction agent mixture A and an extract mixture A; the extract mixture A is subjected to heat centrifugation and filtration to obtain solid upgraded coal and an extract mixture B; the extract mixture B is subjected to rectification to obtain ash-free coal and an extraction agent mixture B; the extraction agent mixture A and the extraction agent mixture B are subjected to decantation to obtain an extraction agent mixture C and water; the extraction agent mixture C is mixed with the organic solvent to obtain a mixed solvent; the mixed solvent is subjected to the above process to perform hot solvent extraction and upgrading of the low-rank coal, and the temperature of the mixed solvent is 95-98℃. After the above process is repeated twice, the ash-free coal is used as a target product, the extraction yield of the ash-free coal is 13.8%, the carbon content is 80.01%, the nitrogen content is 1.15%, and the oxygen content is 13.92%.

[0030] It will be obvious to a person skilled in the art that, without departing from the spirit or essential characteristics of the application, the present application can be implemented in other specific forms. The present examples are therefore to be considered in all respects as illustrative and not restrictive, the scope of the application being indicated by the appended claims rather than by the specification as a whole, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

[0031] Furthermore, it should be understood that, although the present specification is described in terms of embodiments, not every implementation embodies an independent technical solution, and the description of the specification is only for the sake of clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that those skilled in the art can understand.

Claims

1. A process for upgrading low rank coal by hot solvent extraction, characterized in that, It comprises the following steps: Mixing the organic solvent with the low-rank coal at a mass ratio of 12:1, preparing slurry, preheating, and then feeding into a continuous extractor for extraction; Separating the extraction steam from the extraction mixture, and then flashing the extraction mixture to obtain extraction mixture A and extract mixture A; Passing the extract mixture A through heat centrifugation and filtration to obtain solid upgraded coal and extract mixture B; Passing the extract mixture B through rectification to obtain ash-free coal and extraction solvent mixture B; Passing the extraction solvent mixture A and the extraction solvent mixture B through decantation to obtain extraction solvent mixture C and water; Mixing the extraction solvent mixture C with the organic solvent to obtain mixed solvent; Repeating the above process to perform hot-solvent extraction upgrading of the low-rank coal.

2. The process of claim 1, wherein, The preheating temperature is 340℃.

3. The process for upgrading low-rank coal by thermal extraction according to claim 1, characterized in that, The extraction temperature is 335℃-350℃.

4. The process of claim 1, wherein the low-rank coal is heated to a temperature of about 300°C to about 400°C. The extraction steam is subjected to combustion treatment.