Experimental method for coal desulfurization and deashing using permeation and solvating power of a supercritical fluid

Abstract

An experimental method for coal desulfurization and deashing using permeation and solvating power of a supercritical fluid includes the following steps. The coal sample is ground and loaded into an extraction kettle with a cover. An inlet valve and an outlet valve of the extraction kettle are opened to circulate the supercritical CO.sub.2 fluid in the extraction kettle. The extraction kettle is sealed. By adjusting a temperature and a pressure in the extraction kettle, the supercritical CO.sub.2 fluid is kept at its critical point and permeates the coal sample to dissolve organic sulfur, inorganic sulfur and ash in the coal sample. The extraction kettle is depressurized, and the temperature in the extraction kettle is adjusted to gasify the supercritical CO.sub.2 fluid. The organic sulfur, the inorganic sulfur and part of the ash are separated from the supercritical CO.sub.2 fluid and precipitated at a bottom of the extraction kettle.

Claims

1. An experimental method for coal desulfurization and deashing using permeation and solvating power of a supercritical fluid, comprising: 1) grinding a coal sample; 2) preparing an extraction kettle with a cover; opening an inlet valve and an outlet valve of the extraction kettle, so that the extraction kettle is connected to a container in which a supercritical CO.sub.2 fluid is stored; circulating the supercritical CO.sub.2 fluid in a closed system of the extraction kettle; introducing ethanol into a pipeline of the closed system by a pump to clean the pipeline; and closing the outlet valve of the extraction kettle to ensure an air tightness of the extraction kettle; 3) loading the coal sample obtained in step 1) into the extraction kettle; and screwing the cover of the extraction kettle to seal the extraction kettle; 4) adjusting a density of the supercritical CO.sub.2 fluid by adjusting a temperature and a pressure in the extraction kettle, so that the supercritical CO.sub.2 fluid is kept at its critical point; re-adjusting the temperature and the pressure in the extraction kettle to allow the supercritical CO.sub.2 fluid to permeate the coal sample and then dissolve organic sulfur, inorganic sulfur and ash in the coal sample, thereby separating the organic sulfur, the inorganic sulfur and the ash from the coal sample; 5) depressurizing the extraction kettle, and adjusting the temperature in the extraction kettle by a heat exchanger, such that the supercritical CO.sub.2 fluid is gasified, and the organic sulfur, the inorganic sulfur and part of the ash are separated from the supercritical CO.sub.2 fluid and precipitated at a bottom of the extraction kettle, thereby completing coal desulfurization and deashing; and 6) closing the inlet valve of the extraction kettle and opening the outlet valve of the extraction kettle to discharge gaseous CO.sub.2 or recycle the gaseous CO.sub.2 by a cooling system; disconnecting a gas piping; stopping heating to allow the coal sample to cool down; opening the extraction kettle to take out the coal sample; soaking the obtained coal sample in acetone for extraction; and washing the coal sample using deionized water and then drying the coal sample.

2. The experimental method of claim 1, wherein in step 1), a particle size of the coal sample is 1-3 mm or 3-6 mm.

3. The experimental method of claim 1, wherein in step 4), the temperature in the extraction kettle is raised to 35-40° C., and the pressure in the extraction kettle is raised to 7-10 MPa, to make CO.sub.2 in a supercritical state.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a flowchart of an experimental method for coal desulfurization and deashing using permeation and solvating power of a supercritical fluid according to the present application.

(2) FIG. 2 is a schematic diagram of a device using the experimental method of the present application.

DETAILED DESCRIPTION OF EMBODIMENTS

(3) The present application will be further described below with reference to the embodiments.

(4) An experimental method for coal desulfurization and deashing using permeation and solvating power of a supercritical fluid, as shown in FIGS. 1-2, includes the following steps.

(5) 1) Sample Pretreatment

(6) A coal sample is ground until it has a particle size of 1-3 mm or 3-6 mm.

(7) 2) Removal of Air and Impurities in an Extraction Kettle with a Cover

(8) An inlet valve and an outlet valve of the extraction kettle are opened to connect the extraction kettle and a container in which a supercritical CO.sub.2 fluid is stored. The supercritical CO.sub.2 fluid is circulated in a closed system of the extraction kettle. Ethanol is introduced into a pipeline of the closed system by a pump to clean the pipeline. The outlet valve of the extraction kettle is closed to ensure an air tightness of the extraction kettle.

(9) 3) Sample Loading

(10) The coal sample obtained in step 1) is loaded into the extraction kettle. The cover of the extraction kettle is screwed to seal the extraction kettle.

(11) 4) Desulfurization Experiment

(12) 4.1) Adjustment of Temperature and Pressure

(13) A density of the supercritical CO.sub.2 fluid is adjusted by adjusting a temperature and a pressure in the extraction kettle, so that the supercritical CO.sub.2 fluid is kept at its critical point. The temperature and the pressure in the extraction kettle are re-adjusted such that the supercritical CO.sub.2 fluid permeates the coal sample and then dissolve organic sulfur, inorganic sulfur and ash in the coal sample, thereby separating the organic sulfur, the inorganic sulfur and the ash from the coal sample.

(14) 4.2) Separation of the Organic Sulfur, the Inorganic Sulfur and the Ash from the Supercritical CO.sub.2 Fluid

(15) The extraction kettle is depressurized, and the temperature in the extraction kettle is adjusted by a heat exchanger, such that the supercritical CO.sub.2 fluid is gasified, and the organic sulfur, the inorganic sulfur and part of the ash are separated from the supercritical CO.sub.2 fluid and precipitated at a bottom of the extraction kettle, thereby completing coal desulfurization and deashing.

(16) 5) Sample Collection and Subsequent Processing

(17) After the experiment, the inlet valve of the extraction kettle is closed and the outlet valve of the extraction kettle is opened to discharge gaseous CO.sub.2 or recycle the gaseous CO.sub.2 by a cooling system; disconnecting a gas piping. A gas piping is disconnected. Heating stops and the coal sample gradually cools down. The extraction kettle is opened to take out the coal sample. The obtained coal sample is soaked in acetone for extraction and washed using deionized water followed by drying the coal sample for testing the coal sample.

(18) A raw coal from Gaoyang, Baoding City, Hebei province, China was used in an embodiment as follows. Organic sulfur was removed from the raw coal using a SC—CO.sub.2 method.

(19) 1) Sample Pretreatment

(20) A coal sample was ground until it had a particle size of 1-3 mm or 3-6 mm.

(21) 2) Removal of Air and Impurities in an Extraction Kettle with a Cover

(22) An inlet valve and an outlet valve of the extraction kettle were opened to connect the extraction kettle and a CO.sub.2 cylinder, where a pressure of the CO.sub.2 cylinder at an outlet thereof was kept within 5-6 MPa. The supercritical CO.sub.2 fluid was circulated in a closed system of the extraction kettle, and at the same time, the closed system was kept at a required pressure. Ethanol was introduced into a pipeline of the closed system by a pump to clean the pipeline. The outlet valve of the extraction kettle was closed to ensure an air tightness of the extraction kettle.

(23) 3) Sample Loading

(24) The coal sample obtained in step 1) was weighted and loaded into a sample container, and then a filter, a gasket, a porous plate and a threaded ring were placed into the sample container in sequence. A special handle was used to place the sample container into a sample cavity of the extraction kettle. Specifically, the coal sample in the sample container was about 2-3 cm away from the filter arranged above the coal sample to ensure that the sample container was not completely filled with the coal sample. Preferably, the gasket was O-shaped, and the porous plate was made of steel. The threaded ring was screwed into the sample container for the compressing purpose. A volume of the sample cavity was 1 L.

(25) Subsequently, the cover of the extraction kettle was screwed to seal the extraction kettle.

(26) 4) Desulfurization Experiment

(27) A device using the experimental method of the present application was provided with a plurality of circulating water tanks. Before the operation of the device, the circulating water tanks were filled with water, and then the water was heated by an electric heating tube. The heated water was transferred by a circulating pump for heating the extraction kettle and keeping it at a required temperature. The device was also provided with a cool box, and a 30% by weight of aqueous glycol solution was stored in the cool box. The cooling water source was kept unblocked relative to a water-cooled unit.

(28) 4.1) Adjustment of Temperature and Pressure

(29) In the SC—CO.sub.2 process, a density of the supercritical CO.sub.2 fluid was adjusted by adjusting a temperature and a pressure in the extraction kettle, so that the supercritical CO.sub.2 fluid was kept at its critical point. The temperature and the pressure in the extraction kettle were re-adjusted such that the supercritical CO.sub.2 fluid dissolved and separated substances to be removed. During which, the pressure in the extraction kettle and the extraction kettle were always kept at a required value, until the coal sample was taken out of the device.

(30) 4.2) Separation of a Solute from the Supercritical CO.sub.2 Fluid

(31) The supercritical CO.sub.2 fluid permeated the coal sample within a set time to dissolve organic sulfur and inorganic sulfur in the coal sample. The removal of the inorganic sulfur was accompanied by a decrease in an ash content. After decompression, the supercritical CO.sub.2 fluid was separated from the organic sulfur, thereby completing the coal desulfurization and deashing.

(32) 4.3) Depressurization and Heat Exchange

(33) The extraction kettle was depressurized and a temperature in the extraction kettle was adjusted via a heat exchanger, so as to gasify the supercritical CO.sub.2 fluid and precipitate the separated liquid organic sulfur at a bottom of the extraction kettle. Gaseous CO.sub.2 was discharged or recycled by a cooling system.

(34) 5) Sample Collection and Subsequent Processing

(35) After the experiment, a refrigerator pump stopped working, and a CO.sub.2 plunger pump also stopped working. Preferably, the CO.sub.2 plunger pump was a high pressure pump. In addition, the heating and circulation of circulating water were stopped. The inlet valve of the extraction kettle was closed and the outlet valve of the extraction kettle was opened to release gaseous CO.sub.2 in the extraction kettle. A gas piping was disconnected. Heating stopped and the coal sample gradually cooled down. The extraction kettle was opened to take out the coal sample. The obtained coal sample was soaked in acetone for extraction and washed using deionized water followed by drying the coal sample for next testing.

(36) According to the comparison between test data after the reaction and test data before the reaction, the content of the sulfur and the ash in the coal is significantly reduced, and the cohesiveness and calorific value are basically unchanged, which indicates that the organic sulfur is effectively separated, and at the same time, the method of the present application does not affect the quality of the coal.

(37) Comparative experiments are made by changing various variables, such as the temperature, the pressure, the treatment time. The results are shown in Table 1 as follows.

(38) TABLE-US-00001 TABLE 1 Sulfur Ash Volatile Coke Slag Heat Temperature Pressure Time Content Content Content Characteristic Cohesiveness value Raw 2.26 10.57 18.62 5 68.03 31.54 sample Sample 1 35 10 2 2.04 7.22 19.38 4 60.89 30.74 Sample 2 35 10 5 1.80 7.14 18.83 5 58.01 32.05 Sample 3 35 10 14 1.69 6.56 19.19 5 65.93 31.74 Sample 4 35 10 24 1.85 6.48 16.87 5 63.09 31.70 Sample 5 37 8 8 1.78 6.84 19.02 5 69.17 31.93 Sample 6 37 9 14 1.75 6.83 19.03 5 63.48 32.00 Sample 7 37 8 24 1.80 6.30 18.92 5 66.75 32.31

(39) The above-mentioned is only some preferred embodiments. It should be noted that any improvements and modifications may be made by those skilled in the art without departing from the principle of the disclosure, and shall fall within the scope of the present disclosure.