Method and device for building underground storehouse by dissolving limestone with carbon dioxide

Abstract

A method for building an underground storehouse by dissolving limestone with carbon dioxide, the method comprising the following steps: a.) drilling two wells extending from the ground surface (1) to a limestone layer (2), building a channel (5) allowing the two wells to communicate, and installing casing pipes (3, 4) respectively in the two wells; b.) introducing CO.sub.2 gas having at least 1 MPa of pressure into a CO.sub.2 absorbing solution having the same pressure to form a CO.sub.2 solution, flowing the CO.sub.2 solution into underground via the casing pipe (3) to react with the limestone to form a calcium bicarbonate solution, forming a cavern in the meanwhile, and discharging the calcium bicarbonate solution via the other casing pipe (4); c.) decompressing the discharged calcium bicarbonate solution to decompose the calcium bicarbonate contained in the solution into CO.sub.2, water and calcium carbonate, and recycling the separated CO.sub.2 absorption solution and the CO.sub.2; repeating steps b.) and c.) until a cavern meeting design requirements is formed, and discharging the solution from the cavern to form the underground storehouse (6). Also disclosed is a device for building an underground storehouse by dissolving limestone with carbon dioxide, the device comprising a CO.sub.2 storage tank (7), an absorption tower (8), a crystallizer (11), a pressure relief valve (9), a gas-liquid separator (10), a vacuum pump (13), a buffer (14) and booster pumps (12, 15, 16).

Claims

1. A method for construction of an underground reservoir, the method comprising the steps of: a) drilling a first well and a second well extending from a ground surface to a limestone layer, disposing at least one channel in the limestone layer to connect the first well and the second well, and inserting a first sleeve and a second sleeve in the first well and the second well, respectively; b) introducing carbon dioxide having a gas pressure of at least 1 MPa from a carbon dioxide storage tank into a first carbon dioxide absorption solution in an absorption tower to yield a carbon dioxide solution, injecting the carbon dioxide solution into the first sleeve and allowing the carbon dioxide solution to flow to the limestone layer through the first sleeve and react with limestone to yield a solution of calcium bicarbonate, thereby forming a cavern with the solution of calcium bicarbonate being contained in the cavern, and discharging the solution of calcium bicarbonate out of the second sleeve; c) collecting the solution of calcium bicarbonate; decompressing the solution of calcium bicarbonate; decomposing calcium bicarbonate in the solution of calcium bicarbonate to carbon dioxide, water, calcium carbonate, and a second carbon dioxide absorption solution; separating carbon dioxide from the second carbon dioxide absorption solution by using a vacuum pump; crystallizing, precipitating, and discharging calcium carbonate by using a crystallizer; then transporting the second carbon dioxide absorption solution to the absorption tower; transporting carbon dioxide to the carbon dioxide storage tank; and storing calcium carbonate; and d) repeating steps b) and c) until the cavern reaches a desired size, discharging solutions from the cavern to yield the underground reservoir.

2. The method of claim 1, wherein the gas pressure of the carbon dioxide introduced from the carbon dioxide storage tank is between 1 and 15 MPa.

3. The method of claim 2, wherein the gas pressure of the carbon dioxide introduced from the carbon dioxide storage tank is between 2 and 6 MPa.

4. The method of any one of claims 1-3, wherein the first carbon dioxide absorption solution is selected from the group consisting of water, between 0.001 and 10 mol/L of sodium chloride solution, between 0.001 and 5 mol/L of sodium oxalate solution, between 0.001 and 5 mol/L of sodium acetate solution, or a mixture thereof.

5. The method of any one of claims 1-3, wherein the solution of calcium bicarbonate is decompressed at a temperature of between 20 and 80° C. to have a pressure of between 5×10.sup.5 Pa and 1×10.sup.2 Pa.

6. The method of claim 5, wherein the solution of calcium bicarbonate is decompressed at a temperature of between 20 and 80° C. to have a pressure of between 1.01×10.sup.5 Pa and 1×10.sup.3 Pa.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is described hereinbelow with reference to accompanying drawings, in which:

(2) FIG. 1 is an assembly diagram of a first well, a second well, a channel connecting the first well and the second well, a first sleeve, and a second sleeve according to a method for construction of an underground reservoir by dissolving limestone using carbon dioxide according to one embodiment of the invention;

(3) FIG. 2 is a schematic diagram of an underground reservoir constructed according to a method of the invention;

(4) FIG. 3 is a schematic diagram of a device for construction of an underground reservoir by dissolving limestone using carbon dioxide according to one embodiment of the invention; and

(5) FIG. 4 is a schematic diagram of a crystallizer of a device for construction of an underground reservoir by dissolving limestone using carbon dioxide according to one embodiment of the invention.

(6) In the drawings, the following reference numbers are used: 1. Ground; 2. Limestone layer; 3. First sleeve; 4. Second sleeve; 5. Channel; 6. Underground reservoir; 7. CO.sub.2 storage tank; 8. Absorption tower; 9. Decompression valve; 10. Gas-liquid separator; 11. Crystallizer; 12. First booster pump; 13. Vacuum pump; 14. Buffer tank; 15. Second booster pump; 16. Third booster pump; 17. Settling chamber; 18. Stripping chamber; 19. Nozzle; 20. CaCO.sub.3 slurry outlet; 21. CO.sub.2 absorption solution outlet; 22. CO.sub.2 gas outlet; 23. Feeding pump; 24. Heat exchanger.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(7) For further illustrating the invention, experiments detailing a method and device for construction of an underground reservoir by dissolving limestone using carbon dioxide are described below. It should be noted that the following examples are intended to describe and not to limit the invention.

EXAMPLE 1

(8) As shown in FIG. 3, a device for construction of an underground reservoir by dissolving limestone using carbon dioxide comprises a CO.sub.2 storage tank 7; an absorption tower 8; a decompression valve 9; a gas-liquid separator 10; a crystallizer 11; a vacuum pump 13; a buffer tank 14; a first booster pump 12; a second booster pump 15; and a third booster pump 16, all of which employ conventional equipment manufactured in accordance with the design specifications or purchased from chemical markets. As shown in FIG. 4, the crystallizer 11 comprises a settling chamber 17, a stripping chamber 18, a nozzle 19, a feeding pump 23, and a heat exchanger 24. The settling chamber 17 comprises a CaCO.sub.3 slurry outlet 20 at the bottom and a CO.sub.2 absorption solution outlet 21 at the top. The stripping chamber 18 is disposed above and communicates with the settling chamber 17. The CO.sub.2 gas outlet 22 is disposed at the top of the stripping chamber 18. The nozzle 19 is disposed in the stripping chamber 18. A liquid inlet pipe of the nozzle 19 is connected to a liquid outlet of the heat exchanger 24, and a liquid inlet of the heat exchanger 24 is connected to a liquid outlet of the feeding pump 23.

(9) The CO.sub.2 storage tank 7, the absorption tower 8, the decompression valve 9, the gas-liquid separator 10, the crystallizer 11, the vacuum pump 13, the buffer tank 14, the first booster pump 12, the second booster pump 15, and the third booster pump 16 are connected as follows.

(10) The absorption tower 8 comprises a CO.sub.2 gas inlet, a CO.sub.2 gas outlet, a CO.sub.2 absorption solution inlet, and a CO.sub.2 solution outlet. The CO.sub.2 gas inlet of the absorption tower 8 is connected to a gas outlet of the CO.sub.2 storage tank 7 via a first pipe. The CO.sub.2 absorption solution inlet of the absorption tower 8 is connected to a liquid outlet of the first booster pump 12 via a second pipe. The CO.sub.2 gas outlet of the absorption tower 8 is connected to a gas inlet of the third booster pump 16 via a third pipe; a gas inlet of the CO.sub.2 storage tank 7 is connected to gas outlets of the second booster pump 15 and the third booster pump 16 via pipes. The gas-liquid separator 10 comprises a CaHCO.sub.3 solution inlet, a CO.sub.2 gas outlet, and a solution outlet. The CaHCO.sub.3 solution inlet is connected to a liquid outlet of the decompression valve 9 via a fourth pipe. The solution outlet of the gas-liquid separator 10 is connected to a solution inlet of the crystallizer 11 via a fifth pipe. The crystallizer 11 comprises the solution inlet, a CO.sub.2 gas outlet, a CO.sub.2 absorption solution outlet, and a CaCO.sub.3 slurry outlet. The CO.sub.2 gas outlet is connected to an inlet of the vacuum pump 13 via a sixth pipe. The CO.sub.2 absorption solution outlet is connected to a liquid inlet of the first booster pump 12 via a seventh pipe. The seventh pipe connecting the first booster pump 12 and the crystallizer 11 is provided with a connector for supplementing the CO.sub.2 absorption solution; and a gas inlet of the buffer tank 14 is connected to the CO.sub.2 gas outlet of the gas-liquid separator 10 and an outlet of the vacuum pump 13; and a gas outlet of the buffer tank 14 is connected to a gas inlet of the second booster pump 15.

EXAMPLE 2

(11) A method for construction of an underground reservoir by dissolving limestone using carbon dioxide by the device in Example 1 is described as follows.

(12) a) A first well and a second well extending from a ground to a limestone layer are drilled. At least one channel 5 is disposed in the limestone layer to connect the first well and the second well. The first sleeve 3 and the second sleeve 4 (as shown in FIG. 1) are disposed in the first well and the second well, respectively. The first sleeve 3 is connected to the CO.sub.2 solution outlet of the absorption tower 8 of the device in Example 1, and the second sleeve 4 is connected to the liquid inlet of the decompression valve 9.

(13) b) Carbon dioxide having a gas pressure of 3 MPa in the CO.sub.2 storage tank 7 is introduced to the absorption tower where carbon dioxide is absorbed by 2 mol/L of NaCl solution having a pressure of 3 MPa to yield a carbon dioxide solution. Unabsorbed carbon dioxide is discharged from the CO.sub.2 gas outlet disposed at the top of the absorption tower 8, pressurized to 3 MPa by the third booster pump 16 and finally returns to the CO.sub.2 storage tank 7. The carbon dioxide solution is injected into the first sleeve 3 and flows to the limestone layer through the first sleeve 3 to react with limestone to yield a calcium bicarbonate containing solution. Thus, a cavern comprising solutions is formed. The calcium bicarbonate containing solution is discharged out of the second sleeve 4.

(14) c) The discharged calcium bicarbonate containing solution is collected, decompressed to normal pressure by the decompression valve 9, and then is transported to the gas-liquid separator 10. Thereafter, the carbon dioxide dissolved in the calcium bicarbonate containing solution is discharged from the CO.sub.2 gas outlet of the gas-liquid separator 10, transported to the buffer tank 14, and then to the second booster pump 15 via pipes. In the second booster pump 15, the carbon dioxide is pressurized to have a gas pressure of 3 MPa and then transported to the CO.sub.2 storage tank 7. The solution is discharged from the solution outlet of the gas-liquid separator 10, and transported to the heat exchanger 24 via the feeding pump 23 of the crystallizer. In the heat exchanger 24, the solution is heated to 40° C.±5° C. and transported to the nozzle 19 disposed in the stripping chamber. The vacuum degree of the stripping chamber 18 and the settling chamber 17 of the crystallizer is controlled at a pressure of between 100 and 500 Pa. The temperature is controlled at 35° C.±5° C. Thereafter, the calcium bicarbonate containing solution is decomposed to yield carbon dioxide, water, and calcium carbonate. By the pumping of the vacuum pump 13, carbon dioxide is discharged from the CO.sub.2 gas outlet 22 disposed at the top of the stripping chamber 18, transported to the buffer tank 14 and the second booster pump 15 where the pressure of carbon dioxide is enhanced to 3 MPa, and finally returns to the CO.sub.2 storage tank 7. The liquid material enters the settling chamber 17 of the crystallizer and calcium carbonate crystallizes, precipitates, and is discharged from the CaCO.sub.3 slurry outlet 20. The NaCl solution is discharged from the CO.sub.2 absorption solution outlet 21 disposed at the top of the settling chamber, mixed with a NaCl replenisher, pressurized by the first booster pump 12 to have a pressure of 3 MPa, and transported once again to the absorption tower 8.

(15) Steps b) and c) are repeated until a desired cavern comprising solutions is produced. Stop injecting the carbon dioxide solution to the first sleeve 3. Compressed air is pumped into the first sleeve 3 so as to expel the solutions in the cavern to yield the underground reservoir 6 (as shown in FIG. 2).

EXAMPLE 3

(16) A method for construction of an underground reservoir by dissolving limestone using carbon dioxide by the device in Example 1 is described as follows.

(17) a) The step is the same as that in Example 2.

(18) b) Carbon dioxide having a gas pressure of 5 MPa in the CO.sub.2 storage tank 7 is introduced to the absorption tower where carbon dioxide is absorbed by 0.05 mol/L of sodium acetate solution having a pressure of 5 MPa to yield a carbon dioxide solution. Unabsorbed carbon dioxide is discharged from the CO.sub.2 gas outlet disposed at the top of the absorption tower 8, pressurized to 5 MPa by the third booster pump 16 and finally returns to the CO.sub.2 storage tank 7. The carbon dioxide solution is injected into the first sleeve 3 and flows to the limestone layer through the first sleeve 3 to react with limestone to yield a calcium bicarbonate containing solution. Thus, a cavern comprising solutions is formed. The calcium bicarbonate containing solution is discharged out of the second sleeve 4.

(19) c) The discharged calcium bicarbonate containing solution is collected, decompressed to normal pressure by the decompression valve 9, and then is transported to the gas-liquid separator 10. Thereafter, the carbon dioxide dissolved in the calcium bicarbonate containing solution is discharged from the CO.sub.2 gas outlet of the gas-liquid separator 10, transported to the buffer tank 14, and then to the second booster pump 15 via pipes. In the second booster pump 15, the carbon dioxide is pressurized to have a gas pressure of 5 MPa and then transported to the CO.sub.2 storage tank 7. The solution is discharged from the solution outlet of the gas-liquid separator 10, and transported to the heat exchanger 24 via the feeding pump 23 of the crystallizer. In the heat exchanger 24, the solution is heated to 45° C.±5° C. and transported to the nozzle 19 disposed in the stripping chamber. The stripping chamber 18 and the settling chamber 17 work in the normal pressure (the vacuum pump in the example is in nonuse). The temperature is controlled at 40° C.±5° C. Thereafter, the calcium bicarbonate containing solution is decomposed to yield carbon dioxide, water, and calcium carbonate. By the pumping of the vacuum pump 13, carbon dioxide is discharged from the CO.sub.2 gas outlet 22 disposed at the top of the stripping chamber 18, transported to the buffer tank 14 and the second booster pump 15 where the pressure of carbon dioxide is enhanced to 5 MPa, and finally returns to the CO.sub.2 storage tank 7. The liquid material enters the settling chamber 17 of the crystallizer and calcium carbonate crystallizes, precipitates, and is discharged from the CaCO.sub.3 slurry outlet 20. The NaCl solution is discharged from the CO.sub.2 absorption solution outlet 21 disposed at the top of the settling chamber, mixed with a NaCl replenisher, pressurized by the first booster pump 12 to have a pressure of 5 MPa, and transported once again to the absorption tower 8.

(20) Steps b) and c) are repeated until a desired cavern comprising solutions is produced. Stop injecting the carbon dioxide solution to the first sleeve 3. Compressed methane is pumped into the first sleeve 3 so as to expel the solutions in the cavern to yield the underground reservoir 6 (as shown in FIG. 2).

(21) The invention is not limited to above examples. For example, the gas pressure of carbon dioxide to be introduced to the CO.sub.2 absorption solution can be any pressure between 1 and 15 MPa, the pressure of the CO.sub.2 absorption solution can be any pressure between 1 and 15 MPa. The carbon dioxide absorption solution is selected from the group consisting of sodium chloride solution, sodium oxalate solution, sodium acetate solution, or a mixture thereof.

(22) While particular embodiments of the invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.