EFFICIENT AND LOW-ENERGY SHIP CO2 CAPTURE-MEMBRANE DESORPTION-MINERALIZATION FIXATION SYSTEM AND METHOD

Abstract

An efficient and low-energy ship CO.sub.2 capture-membrane desorption-mineralization fixation system, comprising a cooler, a fan, an absorption tower, a CO.sub.2-rich solution pump, a plurality of hollow fiber membrane contactors, and a CO.sub.2-lean solution pump, which are connected one by one to form a queue. The beginning of the queue is connected to a marine diesel engine, and the end of the queue is connected to the absorption power again. The hollow fiber membrane contactors are arranged in parallel. The present invention uses a CO.sub.2 mineralization fixation by seawater as the driving force for the regeneration of CO.sub.2 from the CO.sub.2-rich solution. This system and method can solve the problems existing in the existing ship CCUS technology with zero CO.sub.2 regeneration energy consumption, and easier and safer CO.sub.2 storage in the ocean.

Claims

1. An efficient and low-energy ship CO.sub.2 capture-membrane desorption-mineralization fixation system, comprising a cooler, a fan, an absorption tower, a CO.sub.2-rich solution pump and a plurality of hollow fiber membrane contactors, wherein the cooler, the fan, the absorption tower, the CO.sub.2-rich solution pump and the plurality of hollow fiber membrane contactors are connected to a marine diesel engine, the plurality of hollow fiber membrane contactors are set in parallel, the plurality of hollow fiber membrane contactors are connected to the CO.sub.2-lean solution pump, an outlet end of the CO.sub.2-lean solution pump is connected to an inlet end of the absorption tower, and an outlet end of the absorption tower is connected to an inlet end of the CO.sub.2-rich solution pump, an outlet end of the CO.sub.2-rich solution pump is connected to inlet ends of the plurality of hollow fiber membrane contactors, an outlet end of the cooler is connected to an inlet end of the fan, and an outlet end of the fan is connected to the inlet end of the absorption tower; a total CO.sub.2-rich solution valve is arranged between the CO.sub.2-rich solution pump and the plurality of hollow fiber membrane contactors, a total CO.sub.2-lean solution valve is arranged between the plurality of hollow fiber membrane contactors and the COQ-lean solution pump, a CO.sub.2-rich solution flows into tube sides of the plurality of hollow fiber membrane contactors at a same time through the total CO.sub.2-rich solution valve, and a CO.sub.2-lean solution from the tube sides flows through the total CO.sub.2-lean solution valve; each of the plurality of hollow fiber membrane contactors comprises membrane elements and shell heads, wherein the shell heads are arranged at both ends of the membrane elements, and both ends of the membrane elements are open structures; and the membrane elements are immersed in seawater, and the shell heads are arranged above the seawater level.

2. The efficient and low-energy ship CO.sub.2 capture-membrane desorption-mineralization fixation system according to claim 1, wherein an inlet is set on a top of the absorption tower, an exhaust port is set on a top side of the absorption tower, and a liquid outlet is set on a bottom of the absorption tower, wherein the liquid outlet is connected to the CO.sub.2-rich solution pump.

3. The efficient and low-energy ship CO.sub.2 capture-membrane desorption-mineralization fixation system according to claim 1, wherein a gas inlet is set on a bottom side of the absorption tower, wherein the gas inlet is connected to the fan.

4. The efficient and low-energy ship CO.sub.2 capture-membrane desorption-mineralization fixation system according to claim 1, wherein a membrane material of each of the membrane elements is hydrophobic material, and each of the membrane elements has an inner diameter of 320-350 m, an outer diameter of 0.4-2 mm and a wall thickness of 0.02-0.08 mm; and a size of a pore of each of the membranes is 0.02-0.2 m, and a porosity is >40%.

5. An efficient and low-energy ship CO.sub.2 capture-membrane desorption-mineralization fixation method, using the efficient and low-energy ship CO.sub.2 capture-membrane desorption-mineralization fixation system according to claim 1, comprising the following steps: S1: collecting an exhaust gas in an exhaust pipe of the marine diesel engine and cooling the exhaust gas to obtain a cooled exhaust gas; S2: introducing the cooled exhaust gas into the absorption tower, and using an efficient CO.sub.2 absorbent to capture a ship CO.sub.2 in the absorption tower with countercurrent contact, wherein the treated exhaust gas is discharged from a top of the absorption tower, and a solution obtained on a bottom of the absorption tower is the CO.sub.2-rich solution after CO.sub.2 absorption process; S3: pumping the CO.sub.2-rich solution into the tube sides of the membrane elements of the plurality of hollow fiber membrane contactors with fixed liquid flow rate, wherein the CO.sub.2-rich solution flowing through the membrane tubes becomes the CO.sub.2-lean solution, wherein the CO.sub.2-lean solution is pumped into the absorption tower through the CO.sub.2-lean solution pump for secondary absorption; and S4: during a flow process of the CO.sub.2-rich solution in the tube sides of the membrane elements, allowing the dissolved CO.sub.2 in the CO.sub.2-rich solution to diffuse into seawater through the membrane elements, wherein regeneration of CO.sub.2 from the CO.sub.2-rich solution in the tube sides and mineralization of the regenerated CO.sub.2 in the seawater are completed simultaneously.

6. The efficient and low-energy ship CO.sub.2 capture-membrane desorption-mineralization fixation method according to claim 5, wherein a liquid flow rate in step S3 is fixed ranging from 0.2 m/s-0.5 m/s.

7. The efficient and low-energy ship CO.sub.2 capture-membrane desorption-mineralization fixation method according to claim 5, wherein a rate of CO.sub.2 diffusion from the COQ-rich solution to the seawater through the membrane elements in step S4 is determined by a CO.sub.2 concentration difference between the CO.sub.2-rich solution and the seawater, and a driving force of a diffusion process is provided by a process of CO.sub.2 mineralization fixation by the seawater.

8. The efficient and low-energy ship CO.sub.2 capture-membrane desorption-mineralization fixation method according to claim 5, wherein in the efficient and low-energy ship CO.sub.2 capture-membrane desorption-mineralization fixation system, an inlet is set on a top of the absorption tower, an exhaust port is set on a top side of the absorption tower, and a liquid outlet is set on a bottom of the absorption tower, wherein the liquid outlet is connected to the CO.sub.2-rich solution pump.

9. The efficient and low-energy ship CO.sub.2 capture-membrane desorption-mineralization fixation method according to claim 5, wherein in the efficient and low-energy ship CO.sub.2 capture-membrane desorption-mineralization fixation system, a gas inlet is set on a bottom side of the absorption tower, wherein the gas inlet is connected to the fan.

10. The efficient and low-energy ship CO.sub.2 capture-membrane desorption-mineralization fixation method according to claim 5, wherein in the efficient and low-energy ship CO.sub.2 capture-membrane desorption-mineralization fixation system, a membrane material of each of the membrane elements is hydrophobic material, and each of the membrane elements has an inner diameter of 320-350 m, an outer diameter of 0.4-2 mm and a wall thickness of 0.02-0.08 mm; and a size of a pore of each of the membranes is 0.02-0.2 m, and a porosity is >40%.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG. 1 is a system device diagram of the implementation example of an efficient and low-energy ship CO.sub.2 capture-membrane desorption-mineralization fixation system and method;

[0037] FIG. 2 is a traditional hollow fiber membrane contactor;

[0038] FIG. 3 is a laboratory-level device diagram of the present invention;

[0039] FIG. 4 shows a variation of CO.sub.2 regeneration efficiency with time;

[0040] FIG. 5 shows a variation of CO.sub.2 regeneration flux with time;

[0041] FIG. 6 is a comparison of CO.sub.2 absorption performance between the regenerated solution and the fresh solution;

[0042] FIG. 7 shows variation curves of pH of seawater and CO.sub.2-rich solution with time during regeneration.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0043] The present invention provides an efficient and low-energy ship CO.sub.2 capture-membrane desorption-mineralization fixation system, comprising a cooler 1, a fan 2, an absorption tower 3, a CO.sub.2-rich solution pump 4 and a plurality of hollow fiber membrane contactors, wherein the cooler, the fan, the absorption tower, the CO.sub.2-rich solution pump and the plurality of hollow fiber membrane contactors are connected to a marine diesel engine, the plurality of hollow fiber membrane contactors are set in parallel, the plurality of hollow fiber membrane contactors are connected to the CO.sub.2-lean solution pump 5, an outlet end of the CO.sub.2-lean solution pump 5 is connected to an inlet end of the absorption tower 3, and an outlet end of the absorption tower 3 is connected to an inlet end of the CO.sub.2-rich solution pump 4, an outlet end of the CO.sub.2-rich solution pump 4 is connected to inlet ends of the plurality of hollow fiber membrane contactors, an outlet end of the cooler 1 is connected to an inlet end of the fan 2, and an outlet end of the fan 2 is connected to the inlet end of the absorption tower 3. An inlet 6 is set on a top of the absorption tower 3, an exhaust port is set on a top side of the absorption tower. A gas inlet 8 is set on a bottom side of the absorption tower 3, wherein the gas inlet 8 is connected to the fan 2, and a liquid outlet 14 is set on a bottom of the absorption tower 3, wherein the liquid outlet 14 is connected to the CO.sub.2-rich solution pump 4.

[0044] A total CO.sub.2-rich solution valve 9 is arranged between the CO.sub.2-rich solution pump 4 and the plurality of hollow fiber membrane contactors, a total CO.sub.2-lean solution valve 10 is arranged between the plurality of hollow fiber membrane contactors and the CO.sub.2-lean solution pump 5, a CO.sub.2-rich solution flows into tube sides of the plurality of hollow fiber membrane contactors at a same time through the total CO.sub.2-rich solution valve, and a CO.sub.2-lean solution from the tube sides flows through the total CO.sub.2-lean solution valve. Each of the plurality of hollow fiber membrane contactors comprises membrane elements 11 and shell heads 12, wherein the shell heads 12 are arranged at both ends of the membrane elements 11, and both ends of the membrane elements 11 are open structures. the membrane elements 11 are immersed in seawater 13, and the shell heads are arranged above the seawater level. A membrane material of each of the membrane elements 11 is hydrophobic material, and each of the membrane elements 11 has an inner diameter of 320-350 m, an outer diameter of 0.4-2 mm and a wall thickness of 0.02-0.08 mm; and a size of a pore of each of the membranes is 0.02-0.2 m, and a porosity is >40%.

[0045] A flue gas cooler, a blower, a first flue gas analyzer and a second flue gas analyzer are arranged between the marine diesel engine and the absorption tower. The access end of the flue gas cooler is connected to the exhaust pipe of the marine diesel engine, the outlet end of the flue gas cooler is connected to the access end of the blower, and the outlet end of the blower is connected to the input end of the first flue gas analyzer; the flue gas cooler, blower, the first flue gas analyzer and the absorption tower are connected through the pipeline; where the first flue gas analyzer is located on the side of the inlet of the absorption tower, and the second flue gas analyzer is located on the side of the exhaust port on the top of the absorption tower.

[0046] In one implementation, the absorption tower includes a demister, at least one spray pipe, and at least one spray pipe, the demister is located above at least one spray pipe and at least one spray pipe. At least one spray pipe is located at the upper part of at least one spray pipe.

[0047] An efficient and low-energy ship CO.sub.2 capture-membrane desorption-mineralization fixation method, including the following steps: [0048] S1: collecting an exhaust gas in an exhaust pipe of the marine diesel engine and cooling the exhaust gas to obtain a cooled exhaust gas; [0049] S2: introducing the cooled exhaust gas into the absorption tower, and using an efficient CO.sub.2 absorbent to capture a ship CO.sub.2 in the absorption tower with countercurrent contact, wherein the treated exhaust gas is discharged from a top of the absorption tower, and a solution obtained on a bottom of the absorption tower is the CO.sub.2-rich solution after CO.sub.2 absorption process; [0050] S3: pumping the CO.sub.2-rich solution into the tube sides of the membrane elements of the plurality of hollow fiber membrane contactors with fixed liquid flow rate, wherein the CO.sub.2-rich solution flowing through the membrane tubes becomes the CO.sub.2-lean solution, wherein the CO.sub.2-lean solution is pumped into the absorption tower through the CO.sub.2-lean solution pump for secondary absorption; and [0051] S4: during a flow process of the CO.sub.2-rich solution in the tube sides of the membrane elements, allowing the dissolved CO.sub.2 in the CO.sub.2-rich solution to diffuse into seawater through the membrane elements, wherein regeneration of CO.sub.2 from the CO.sub.2-rich solution in the tube sides and mineralization of the regenerated CO.sub.2 in the seawater are completed simultaneously.

[0052] The CO.sub.2 absorbent used in this method is any physical solution and chemical solution that can absorb CO.sub.2, including but not limited to alkanolamine solution, inorganic base solution, amino acid salt, etc.

[0053] Ship flue gas CO.sub.2 refers to the CO.sub.2 emitted during the combustion of fuel, including but not limited to coal, oil, natural gas, etc.

[0054] CO.sub.2-rich solution is collected at the bottom of the absorption tower after the countercurrent contact of CO.sub.2 with the absorbents, the CO.sub.2-rich solution can be saturated or unsaturated CO.sub.2 loaded solutions.

[0055] Seawater is any artificial seawater and natural seawater, and the pH range is between 7 and 10.

[0056] The technical scheme of the present invention is further explained by the following drawings and examples.

Example

[0057] The artificial seawater composition used in the following embodiments of the invention is determined according to ASTM D 1141-98 Standard Practice for the Preparation of Substitute Ocean Water, and its composition is shown in Table 1.

TABLE-US-00001 TABLE 1 Component Concentration(g .Math. L.sup.1) NaCl 24.530 Na.sub.2SO.sub.4 4.090 MgCl.sub.2 5.200 CaCl.sub.2 1.160 SrCl.sub.2 0.025 KCl 0.695 NaHCO.sub.3 0.201 KBr 0.101 H.sub.3BO.sub.3 0.027 NaF 0.003

[0058] CO.sub.2 capture-membrane desorption-mineralization fixation method: [0059] (1) FIG. 1 is the system device diagram of CO.sub.2 capture, desorption, mineralization of ship CO.sub.2. As shown in the diagram, the CO.sub.2 emitted by the ship enters the cooler, and then enters the absorption tower from the inlet under the action of the fan, and the CO.sub.2-rich solution is obtained at the bottom of the tower. The 2M potassium glycine solution is used as the CO.sub.2 absorbent to absorb CO.sub.2 to saturation at room temperature and atmospheric pressure. The CO.sub.2 absorption capacity is 1.43 mol/L, and 100 ml of CO.sub.2-rich solution is taken for regeneration. After absorption process, the solution became CO.sub.2-rich solution, which is pumped from the bottom outlet of the absorption tower, and the remaining flue gas is discharged from the top outlet of the absorption tower. Opening the total rich solution valve and the total lean solution valve, so that the CO.sub.2-rich solution enters the tube sides of the membrane elements at a constant speed to realize the regeneration of CO.sub.2-rich solution and the mineralization of the regenerated CO.sub.2 simultaneously. The CO.sub.2-lean solution after the membrane flowing process is pumped into the absorption tower through the inlet of the lean solution pump to absorb the ship CO.sub.2 again, and the whole process is repeated. [0060] (2) The traditional hollow fiber membrane contactor (FIG. 2) is modified. FIG. 2 is the traditional hollow fiber membrane contactor. As shown in the figure, 21 is the outlet for gas, 22 is the inlet for solution, 23 is the outlet for solution, 24 is the inlet for gas, 25 is the tube of the hollow fiber membrane, 26 is the shell of the hollow fiber membrane, 27 is the membrane shell, 28 is the membrane shell head. Removing the membrane shell, retain both ends of the shell heads and the membrane elements, the shell heads and the membrane elements are poured and connected, and the two ends of the membrane elements are not sealed. The hollow fiber membrane material is hydrophobic PP material. The inner diameter of the hollow fiber membrane is 320-350 m, the outer diameter is 400-450 m, the wall thickness is 40-45 m, the pore size of the membrane is 0.02-0.2 m, and the porosity is 40%-50%. The membrane element is immersed in artificial seawater, and the shell heads are above the seawater level. [0061] (3) FIG. 3 is a laboratory-level CO.sub.2 membrane desorption-mineralization fixation device diagram. As shown in the diagram, pumping 100 ml of rich solution 37 from one end of the conical flask 32 to one end of the membrane elements 33 at a flow rate of 0.5 ml/s by using a peristaltic pump 31 and enters the tube pass. Pump out at the other end of the tube pass, pump back to the conical flask 32 again, and cycle operation for 60 h. The hollow fiber membrane of the membrane element 33 was immersed in 800 ml artificial seawater 34. The ends of the membrane elements 33 were on the surface of the artificial seawater 34, and the artificial seawater 34 in the three-port flask 36 is stirred by the magnetic stirrer 35. The regeneration time is 60 h, and the artificial seawater was not replaced during the regeneration process. The pH changes of CO.sub.2-rich solution and seawater were monitored in real time (as shown in FIG. 7). The CO.sub.2 loading in CO.sub.2-rich solution is titrated every 12 h to determine the CO.sub.2 regeneration efficiency .sub.CO.sub.2 (as shown in FIG. 4) and CO.sub.2 regeneration rate N.sub.CO.sub.2, (as shown in FIG. 5), the calculation formula is as follows:

[00001]$N_{{\mathrm{CO}}_2}=\left(C_{L,i}-C_{L,o}\right)Q_L$$\left(\%\right)=\left(1-\frac{C_{L,o}}{C_{L,i}}\right)$

[0062] where A.sub.i is the inner surface area of hollow fiber membrane; C.sub.L,i and C.sub.L,o are the concentration of CO.sub.2 in the solution at the inlet and outlet of the assembly, respectively; Q.sub.L is the liquid flow rate controlled by the peristaltic pump.

[0063] FIG. 4 shows the variation of CO.sub.2 regeneration efficiency with time. As shown in the figure, the CO.sub.2 regeneration efficiency increases rapidly in the first 24 hours of the regeneration process, and the regeneration efficiency increases slowly with time from 24 hours to 60 hours. The regeneration efficiency is about 57% at 60 hours.

[0064] FIG. 5 shows the variation of CO.sub.2 regeneration rate with time. As shown in the figure, the regeneration rate is represented by the CO.sub.2 flux during the regeneration process. The CO.sub.2 regeneration flux increases rapidly in the first 24 hours of the regeneration process, and the regeneration flux increases slowly with time from 24 hours to 60 hours, in units of mol.Math.L.sup.1.Math.m.sup.2.

[0065] FIG. 6 shows the comparison between the secondary CO.sub.2 absorption performance of the regenerated solution and the initial CO.sub.2 absorption performance of the fresh solution. As shown in the figure, the original solution reached saturation after the first absorption of CO.sub.2 65 minutes, and the absorption amount was 1.43 mol/L. After regeneration, the solution absorbs CO.sub.2 again and reaches saturation after 250 minutes, and the absorption amount is 0.943 mol/L.

[0066] FIG. 7 shows the variation of pH of seawater and CO.sub.2-rich solution with time during regeneration. As shown in the figure, the pH of seawater began to decrease from 8.35, and decreased to the lowest value of 7.16 at the fourth hour, then began to rise slowly, and rose to 8.10 after 50 hours and tended to be stable. The pH of CO.sub.2-rich solution gradually increased from 8.14 to 9.10 and tended to be stable. It shows that the CO.sub.2 in the CO.sub.2-rich solution is continuously reduced and diffuses into the seawater through the hollow fiber membrane. [0067] (4) After the regeneration, the regenerated absorption solution is pumped into the absorption tower for secondary absorption to determine the cycle stability of the technology (as shown in FIG. 1).

[0068] Therefore, the present invention adopts an efficient and low-energy ship CO.sub.2 capture-membrane desorption-mineralization fixation system and method with the above structure to solve the problems existing in the existing ship CCUS technology. CO.sub.2 is stored in the ocean in the form of carbonate, which makes storage easier and safer, and saves space.

[0069] Finally, it should be noted that the above implementation examples are only used to explain the technical scheme of the invention rather than to restrict it. Although the invention is described in detail with reference to the better implementation examples, ordinary technicians in this field should understand that they can still modify or replace the technical scheme of the invention, and these modifications or equivalent replacements cannot make the modified technical scheme out of the spirit and scope of the technical scheme of the invention.