WO2016000204A1

WO2016000204A1 - Method for increasing concentration of coarse coal water slurry

Info

Publication number: WO2016000204A1
Application number: PCT/CN2014/081351
Authority: WO
Inventors: 李春启; 梅长松; 康善娇; 刘卫兵; 刘鑫; 杨明顺; 齐永丽
Original assignee: 大唐国际化工技术研究院有限公司
Priority date: 2014-07-01
Filing date: 2014-07-01
Publication date: 2016-01-07
Also published as: AU2014399747B2; AU2014399747A2; AU2014399747A1

Abstract

A method for increasing the concentration of a coarse coal water slurry, comprising the following steps: (1) pre-heating the coarse coal water slurry, the temperature for the pre-heating being 160°C-280°C and the pressure being 0.6-6.4 MPa; (2) heating the pre-heated coarse coal water slurry to a heat preservation temperature so as to perform a heat preservation treatment, the temperature for the heat preservation treatment being 200°C-320°C and the pressure being 1.5-11.3 MPa; (3) leaving the coarse coal water slurry which has been subjected to the heat preservation treatment to stand, the standing time being 10-90 minutes, and preferably the standing time being 20-60 minutes; (4) performing a flash evaporation treatment on the coarse coal water slurry which has been left to stand; and (5) obtaining the coal water slurry with an increased concentration by filtering the coarse coal water slurry which has been subjected to the flash evaporation treatment, adding an additive and stirring the mixture successively.

Description

Method for improving concentration of coarse coal water slurry

The invention belongs to the technical field of coal treatment, and particularly relates to a method for increasing the concentration of coarse coal water slurry. Background technique

Although China's energy resources are relatively rich, but the structure is unbalanced, and the distribution is uneven, showing the characteristics of "rich coal, poor oil, and less gas." Coal accounts for about 70% of China's primary energy production, accounting for 63% of total primary energy consumption, far above the world average, while oil-based gasoline and diesel resources are tight, and oil is heavily imported. The problem has become a bottleneck restricting China's economic and social development for a long time. Therefore, for a long period of time in the future, coal energy utilization will still be the most important way to use energy in China. In terms of proportion and quantity, China's coal-based primary energy production and consumption structure are difficult to change.

At present, China is implementing a clean coal program. Therefore, clean coal technology is an important means to improve coal utilization efficiency and reduce environmental pollution, and is receiving more and more attention from all walks of life. The coal water slurry (CWM) is a raw coal with a particle size distribution of about 65wt.%~70wt.°/c^, 30wt.%~35wt.% of water and about 1wt.% of additives, which are cleaned by a certain processing process. Coal based fluid fuel. This technology transforms solid coal fuel into fluid coal fuel, which has the characteristics of liquid combustion application similar to heavy oil. This has important practical significance for promoting the clean utilization of coal, and the development of coal-water slurry technology benefits. _P , , , , , _P , ^P , , Although China's coal resources are relatively complete, including coal from different stages of lignite to anthracite, but the quality resources are less, and the quantity distribution is uneven. Lignite and low-metamorphic bituminous coal are large, accounting for about 55% of the identified resource reserves; medium-grade metamorphic coking bituminous coal is small, accounting for 28% of the identified resource reserves, and most of them are gas coal; high-denatured lean coal It has a smaller number of anthracite coals, accounting for only 17% of the identified resource reserves. The low metamorphic coal with large reserves is mainly distributed in eastern Inner Mongolia and Yunnan. Because of its low calorific value and high moisture content, it is not suitable for long-distance transportation, which restricts the development and utilization of coal resources in these areas to some extent.

At present, low-rank coal with abundant reserves is mainly used as coal for power coal and gasification. Its own characteristics lead to its slurry concentration can only reach 30wt.%~50wt.%, which belongs to low concentration coal water slurry, and it is difficult to prepare into high concentration coal water slurry, or need to use complicated preparation process and pay Higher cost to make high Concentration of coal water slurry. The concentration of coal water slurry affects the oxygen consumption and coal consumption during the gasification process of coal water slurry. High-concentration coal-water slurry has many advantages such as low water content, high effective solid content, high calorific value and good pumping performance. Therefore, from the perspective of gasification and combustion efficiency, the concentration of coal water slurry

"At present, the country mainly draws particle size grading and selects suitable additives to increase the concentration of coal water slurry, but the concentration increase is very limited, generally only the crude coal slurry concentration can be increased by 3wt.%~5wt.%. It is imperative to develop a new process that can significantly increase the concentration of low-concentration coal water slurry.

Accordingly, it is an object of the present invention to provide a method for improving the concentration of coarse coal water slurry by solving the drawbacks of the prior art technique for increasing the concentration of coarse coal water slurry.

The object of the present invention is achieved by providing the following technical solutions:

A method for increasing the concentration of coarse coal water slurry, the method comprising the steps of:

(1) preheating the coarse coal water slurry, the preheating temperature is 160~280 °C: and the pressure is 0.6~6.4MPa;

(2) heating the coarse coal slurry after preheating to a holding temperature for heat treatment, the temperature of the heat treatment is 200~320 ° C, and the pressure is 1.5~ 11.3 MPa;

(3) The coarse water coal slurry after the heat treatment is subjected to a residence treatment, and the residence time is 10 to 90 mm, and the preferred residence time is 20 to 60 minutes;

(4) flashing the crude coal slurry after the treatment;

(5) filtering the crude coal slurry after the flash treatment to obtain a coal water slurry having an increased concentration.

The inventors have found that in the above method of the present invention, the internal water content in the coarse coal water slurry can be significantly reduced by preheating, for example, the internal water content of the raw coal can be reduced to 3 to 5%. The residence treatment is to hydrothermally treat the coarse coal water slurry to achieve the purpose of further increasing its concentration and improving its pulping performance.

According to the method of the present invention, the method preferably further comprises the step (6): recovering the heat obtained by the flash treatment described in the step (4) for the preheat treatment described in the step (2).

In a preferred embodiment of the method of the present invention, the step (5) of the method further comprises: adding an additive to the filtered coarse coal water slurry, followed by stirring to obtain an increased concentration of the coal water slurry. Preferably, the additive is one or more of a dispersant, a stabilizer, an antifoaming agent, a pH adjuster, or a bactericide. More preferably, the agitation is carried out in a pulp tank with a stirring device The present inventors have found that in the above method of the present invention, in order to enable the coarse coal water slurry to have both a lower viscosity and a better fluidity in normal use, a relatively high concentration can be achieved and precipitation is less likely to occur. The addition of a small amount of additives in the pulping process has a certain effect. Its role mainly occurs at the interface between coal and water. The effect is inseparable from the properties of the raw coal itself and the nature of the water. Suitable dispersants can be improved. The surface of the coal is hydrophilic, enhancing the electrostatic repulsion between the coal particles and the spatial isolation steric effect. For example, dispersants such as naphthalenesulfonate, sulfonated humate and sulfonated lignosulfonate can be used in the present invention. The stabilizer can crosslink the dispersed solid particles to form a space structure, effectively prevent the precipitation of the particles, and prevent the separation between the solid and the liquid. For example, stabilizers such as inorganic electrolytes and polymer compounds can be used in the present invention. Defoamer is when the dispersant has strong foaming performance, it needs to add certain defoaming agent to defoam to promote the smooth production. For example, an antifoaming agent such as an alcohol, a phosphate, or a naphthalenesulfonic acid formaldehyde condensate can be used in the present invention. The pH adjuster can adjust the pH value of the coal water slurry system, and adjust the coal water slurry to a weakly alkaline solution, which is beneficial to obtain good pulping effects. For example, pH adjusters such as ammonia water, calcium hydroxide and sodium hydroxide are available. In the present invention. Fungicides are also known as anti-fungal agents because they are generally organic substances. Some are prone to decomposition by bacteria during long-term storage. At this time, the addition of fungicides can ensure the performance of the coal slurry. The fungicide selected is isothiazolinone.

According to the method of the present invention, the additive is preferably used in an amount of from 0.1 to 1% by weight based on the dry coal, more preferably from 0.2 to 0.7%, most preferably 0.5%.

It is not necessary to add all of the above types of additives at the time of production. Those skilled in the art can selectively add appropriate additives depending on the type of coal used, the origin of the raw coal, and the chemical nature of the crude coal slurry. For example, when the dispersibility of the coarse coal water slurry is poor and other chemical properties are better, only the dispersant may be added; when the dispersibility and stability of the coarse coal water slurry are poor, the dispersant and the stabilizer may be simultaneously added. When the coarse coal water slurry needs to be stored or transported for a long time, a fungicide may also be added.

According to the method of the present invention, the preheat treatment described in the step (1) is preferably carried out in a casing heat exchanger, and more preferably, the casing heat exchanger inlet temperature is 20 to 70 ° C :.

In the above method, the coarse water coal slurry may be conveyed to the casing heat exchanger by a coal slurry pump, and the initial pressure of the coarse water coal slurry is supplied by the coal slurry pump. The invention is not limited by the number of stages of the casing heat exchanger, and the temperature set by the person skilled in the art according to the specific working conditions can select different stages of the casing heat exchanger to achieve the optimal improvement of the coarse water coal slurry. The effect of concentration. For example, when the preheating temperature is 260 °C, a casing heat exchanger with a three-stage number can be selected.

According to the method of the present invention, the heating in step (2) is preferably by direct heating or between Heat it up. Further preferably, the direct heating is preferably direct steam heating, and still more preferably, the indirect heating is preferably molten salt heat exchange, fire tube heating, oil bath heat exchange or steam heat exchange.

According to the method of the present invention, the residence treatment described in the step (3) is preferably carried out in a heat retention tank, more preferably in a series insulation retention tank. Further preferably, the bottom of the insulated stay tank is filled with a gas, and still more preferably, the gas is nitrogen, air or water vapor.

In the above method, the present invention is not limited by the number of insulation retention tanks, and those skilled in the art can select different stages of insulation retention tanks according to the residence time required by specific working conditions, so as to optimally improve the coarse water coal. The effect of pulp concentration. For example, when the temperature of the heat treatment is 300 ° C: and the residence time is 30 mm, the temperature retention tank of the tenth grade can be selected.

In the above method, the inflowing gas is used for timing purge to prevent sedimentation of the coarse water coal slurry.

According to the method of the present invention, the flashing treatment described in the step (4) is preferably carried out in a flash tank, and more preferably, the outlet temperature of the flash tank is 100 to 120 °C:.

In the above method, the present invention is not limited by the number of flash tank stages. In general, the number of stages of the flash tank is the same as that of the above-mentioned casing heat exchanger.

In the above method, the flash steam in each stage of the flash tank enters the casing preheater, preheating the coarse coal water slurry to achieve heat recovery, and the recovered heat is used in the step (2). Preheating as described.

According to the method provided by the present invention, the filtration in the step (5) is preferably carried out by means of a filter press or a vacuum filter.

According to the method provided by the present invention, the concentration of the coal water slurry having an increased concentration as described in the step (5) is preferably 52 to 65 wt.%.

Unless otherwise stated, in the present invention, the unit symbol "wt.%" means a percentage by weight.

Unless otherwise stated, the "coarse water slurry" as used in the present invention refers to a low concentration coal water slurry having a concentration of generally 30 to 50 wt.%, and the low concentration coal water slurry may be directly mixed with coal and water. The coal water slurry obtained by any treatment may also be a coal water slurry prepared by a conventional coal water slurry pulping process or a granular grade slurry. Among them, the traditional pulping process refers to the preparation of coal water slurry by adding the appropriate additives after grinding, and the process of preparing the coal water slurry by mixing the raw coal with different particle sizes, mainly The raw coal is ground into pulverized coal with high packing efficiency, so that the accumulation pores are the smallest, the pores between the large particles are filled by the smaller particles, and the pores between the small particles are filled by the smaller particles, thereby reducing the pores. The water content increases the pulping concentration and improves the fluidity and slurry properties of the coal water slurry. That is to say, the present invention can further increase the concentration of the excessively concentrated coal water slurry by using the prior art on the basis of the prior art. For specific preparation, for example, the original coal gangue can be broken. The crusher is subjected to preliminary pulverization, and then an appropriate amount of water is added, and sent to a coal mill for preliminary wet grinding to obtain the above coarse coal slurry.

Unless otherwise stated, the invention does not limit the coal type and origin of the raw coal used in the coarse coal water slurry. It should be understood that the present invention is applicable to coarse coal water slurry prepared by various coal types, such as lignite or bituminous coal having a lower slurry concentration; the present invention is also applicable to crude coal produced from raw coal produced from different places of origin. Pulp, such as raw coal produced in Henan Hebi, Shandong Yinzhou, Shanxi Binxian or Inner Mongolia Xilinhot.

The invention has the advantages of simple process flow, low cost and energy saving, and the concentration of the coarse coal water slurry can be significantly increased to 52 ~ 65 wt.%. In industrial applications, a significant economic benefit is achieved for every one hundredth increase in the concentration of coarse coal water slurry, and thus the present invention can also produce significant economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, in which:

Figure 1 is a flow chart of the present invention using a fire tube heating to increase the concentration of coarse coal water slurry;

2 is a flow chart of the present invention for directly increasing the concentration of coarse coal water slurry by steam, and FIG. 3 is a flow chart of the present invention for increasing the concentration of low concentration coal water slurry by steam heat exchange.

In the drawing, 1, pulverizer, 2, coal mill, 3, coal slurry pump, 4, casing heat exchanger, 5, fire tube heater, 6, series insulation retention tank, 7, flash tank, 8 , coal slurry tank, 9, coal slurry pump, 10, filter press, 11, pulp tank, 12, steam heater, 13, vacuum filter, 14, steam heat exchanger. The best way to implement the invention

The present invention will be further described in detail with reference to the preferred embodiments of the present invention, and the present invention is not intended to limit the scope of the invention.

The raw coals used in the following examples of the present invention are all from the Xilinhot East Shengli lignite in Inner Mongolia, and the additives used in the present invention are all the same naphthalenesulfonates obtained through formal channels. Example 1

As shown in Fig. 1, when the fire tube heater 5 is used to increase the concentration of the coarse coal slurry, the specific process steps are as follows:

(1) The lignite is pulverized by the pulverizer 1 to a particle size of <6 mm, and water is sent to the coal mill 2 for preliminary wet grinding to prepare coarse coal water slurry, and the crude coal water slurry without any treatment directly mixed with coal and water is obtained. The weight ratio of water to coal in the coarse coal water slurry is about 3:1;

(2) Send the coarse coal slurry to the casing heat exchanger 4 for preheating at room temperature at a normal temperature The preheating temperature is 160 ° C: the pressure is 0.6 MPa, the inlet temperature of the casing heat exchanger D is 20 ° C; when preheating, the coarse water coal slurry flows through the tube of the casing heat exchanger 4 The layer and the water vapor preheat the coarse coal water slurry through the shell layer of the casing heat exchanger 4;

(3) The pre-heat treated coarse water coal slurry is heated to the holding temperature by the fire tube heater 5 to maintain the temperature, the temperature of the heat treatment is 200 ° C: and the pressure is maintained at 1.5 MPa;

(4) The coarse water coal slurry after the heat treatment is sent into the series heat preservation staying tank 6 to stay 90 mm, and the bottom of the series heat preservation stay tank 6 is filled with nitrogen gas for timing purging to prevent the coarse coal slurry from settling;

(5) The crude water coal slurry is sent to the flash tank 7 for flashing treatment, and the outlet temperature of the flash tank 7 is 100 ° C, and the heat is recovered for preheating of the casing heat exchanger 4;

(6) The coarse water coal slurry after the flash cooling and pressure reduction is sent to the coal slurry tank 8, sent to the filter press 10 by the coal slurry pump 9, and then added with 0.5% of the weight of the dry base coal and then fed. The pulping tank 11 of the stirring device was stirred and pulped to obtain a coal water slurry having a concentration increased to 52 wt.%.

As shown in Fig. 2, when the steam heater 12 is used for direct heating to increase the concentration of the coarse coal slurry, the specific process steps are as follows:

(1) The lignite is pulverized by a pulverizer 1 to a particle size of <6 mm, and water and an additive of 0.5% by weight of the dry coal are added, and sent to a coal mill 2 for preliminary wet grinding to prepare a coarse water coal slurry, and the crude water is measured. The concentration of coal slurry is about 43 wt.%;

(2) The coarse coal water slurry is sent to the casing heat exchanger 4 for preheating at a normal temperature by a coal slurry pump 3, and the temperature of the preheat treatment is 280 ° C, the pressure is 6.4 MPa, and the casing heat exchanger The inlet temperature of 4 is 30 ° C; during preheating, the coarse water coal slurry flows through the tube layer of the casing heat exchanger 4, and the water vapor passes through the shell layer of the casing heat exchanger 4 to preheat the coarse coal water slurry;

(3) The new steam is introduced into the steam heater 12, and the preheated coarse coal slurry is heated to the holding temperature for heat treatment. The temperature of the heat treatment is 320 ° C: the pressure is maintained at

11.3MPa;

(4) The coarse water coal slurry after the heat treatment is sent to the series heat preservation staying tank 6 to stay 10 mm, and the bottom of the series heat preservation stay tank 6 is filled with air for timing purging to prevent the coarse coal slurry from settling;

(5) The crude water coal slurry is sent to the flash tank 7 for flashing treatment, and the outlet temperature of the flash tank 7 is 120 ° C, and the heat is recovered for preheating of the casing heat exchanger 4;

(6) The coarse water coal slurry after the flash cooling and pressure reduction is sent to the coal slurry tank 8, sent to the vacuum filter 13 by the coal slurry pump 9, and then added with 0.5% of the weight of the dry coal, and then fed. Stirring device The pulping tank 11 was stirred and pulped to obtain a coal water slurry having a concentration increased to 60 wt.%. Example 3

As shown in Fig. 3, when the steam heat exchanger 14 is used to increase the concentration of the coarse water coal slurry, the specific process steps of the present invention are as follows:

(1) The lignite is pulverized by a pulverizer 1 to obtain a pulverized coal having a particle size of <6 mm and a particle size of about 6% of a total weight of about 6 mm, which is about 70% of the total weight, and the pulverized coal of the two sizes is mixed and added to the water. The coal mill 2 is subjected to preliminary wet grinding to prepare coarse coal water slurry, and the concentration of the coarse coal water slurry is measured to be about 41 wt.%;

(2) The crude water coal slurry is sent to the casing heat exchanger 4 for preheating at a normal temperature by a coal slurry pump 3, and the preheating temperature is 260 ° C: the pressure is 4.7 MPa, the casing heat exchange The inlet temperature of the device 4 is 70 ° C; during preheating, the coarse water coal slurry flows through the tube layer of the casing heat exchanger 4, and the water vapor passes through the shell layer of the casing heat exchanger 4 to preheat the coarse coal water slurry. ;

(3) The pre-heat treated coarse water coal slurry is heated to a holding temperature by a steam heat exchanger for heat treatment, the temperature of the heat treatment is 300 ° C, and the pressure is maintained at 8.7 MPa;

(4) The heated coarse coal slurry is sent to the series insulation retention tank 6 for 60 minutes, and the bottom of the insulation retention tank 6 is connected with water vapor for timing purge to prevent the coarse coal slurry from settling;

(5) The crude water coal slurry is sent to the flash tank 7 for flashing, and the outlet temperature of the flash tank 7 is 110 ° C, and the heat is recovered for preheating of the casing heat exchanger 4;

(6) The coarse water coal slurry after flashing and cooling down is sent to the coal slurry tank 8, sent to the filter press machine 10 by the coal slurry pump 9, and then added with 0.5% of the weight of the dry base coal and then fed. The pulping tank 11 of the stirring device was stirred and pulped to obtain a coal water slurry having a concentration increased to 62 wt.%. Example 4

When the steam heat exchanger shown in Figure 3 is changed to a molten salt heat exchanger or an oil bath heat exchanger to increase the concentration of coarse water coal slurry, the specific process steps are as follows:

(1) The lignite is pulverized by a pulverizer 1 to obtain a coal powder having a particle size of <6 mm and a particle size of about 6% by weight of about 6% by weight of about 6% of the total weight, and mixing the two sizes of pulverized coal, adding water and occupying The additive of 0.5% by weight of dry coal is sent to the coal mill 2 for preliminary wet grinding to prepare coarse coal water slurry, and the concentration of the crude coal water slurry is determined to be about 48 wt.%;

(2) The crude water coal slurry is sent to the casing heat exchanger 4 for preheating at a normal temperature by a coal slurry pump 3, and the preheating temperature is 260 ° C: the pressure is 4.7 MPa, the casing heat exchange The inlet temperature of the device 4 is 70 °C; When preheating, the coarse water coal slurry flows through the tube layer of the casing heat exchanger 4, and the water vapor is preheated through the shell layer of the casing heat exchanger 4;

(3) The pre-heat treated coarse water coal slurry is heated by the molten salt heat exchange or oil bath heat exchanger to the holding temperature for heat preservation treatment, the temperature of the heat preservation treatment is 300 ° C: and the pressure is maintained at 8.7 MPa; (4) The heated coarse water coal slurry is sent into the series heat preservation staying tank 6 to stay 60 mm, and the bottom of the series heat preservation staying tank 6 is filled with water steam for timing purging to prevent the coarse coal slurry from settling;

(6) The coarse water coal slurry after flashing and cooling is sent to the coal slurry tank 8, sent to the filter press 10 by the coal slurry pump 9, and then added with 0.5% of the weight of the dry coal, and then fed. The pulping tank 11 of the stirring device was stirred and pulped, and the concentration of the obtained coal water slurry was 65 wt.%. In the above embodiments, although the heating modes of the respective embodiments are different, the heating method employed is not limited to the specific embodiment, and it should be understood that each heating mode can be applied to other embodiments, and Produce the same or similar results.

Although the present invention has been described in some detail, it should be understood that the foregoing description is not intended to be construed as limiting the invention, any modifications, equivalents, improvements, etc., should be made without departing from the spirit and scope of the invention. It is included in the scope of protection of the present invention.

Claims

Rights request

(1) preheating the coarse coal water slurry, the preheating temperature is 160~280 °C: and the pressure is 0.6 ~ 6.4 MPa;

(4) flashing the crude coal slurry after the treatment;

2. The method according to claim 1, wherein the method further comprises the step (6): recovering the heat obtained by the flash treatment described in the step (4) for use in the step (2) Preheat treatment as described.

The method according to claim 1 or 2, wherein the step (5) of the method further comprises: adding an additive to the filtered coarse coal water slurry, and then stirring to obtain an increased concentration. a coal water slurry; preferably, the additive is one or more of a dispersing agent, a stabilizer, an antifoaming agent, a pH adjusting agent or a sterilizing agent; more preferably, the stirring is performed by a stirring device Performed in a slurry tank.

4. Process according to claim 3, characterized in that the additive is used in an amount of from 0.1 to 1%, preferably from 0.2 to 0.7%, more preferably 0.5% by weight of the dry coal.

The method according to any one of claims 1 to 4, characterized in that the preheating treatment in the step (1) is carried out in a casing heat exchanger, preferably the casing Heat exchanger inlet temperature is 20~70°C _o

The method according to any one of claims 1 to 5, wherein the heating in the step (2) is performed by direct heating or indirect heating; preferably, the direct heating is direct heating of steam More preferably, the indirect heating is molten salt heat exchange, fire tube heating, oil bath heat exchange or steam heat exchange.

The method according to any one of claims 1 to 6, wherein the staying treatment in the step (3) is carried out in a heat-insulating residence tank, preferably in a series insulation holding tank. Preferably, the bottom of the insulated stay tank is filled with gas, more preferably, the gas is nitrogen,

The method according to any one of claims 1 to 7, wherein the flashing treatment in the step (4) is carried out in a flash tank, preferably, the flash tank The outlet temperature is 100~120°C:.

The method according to any one of claims 1 to 8, characterized in that the filtration in the step (5) is carried out by means of a filter press or a vacuum filter.

The method according to any one of claims 1 to 9, characterized in that the concentration of the increased concentration of the coal water slurry prepared in the step (5) is 52 to 65 wt.%.