System and method for treating trimethylaluminum residual liquid

Abstract

The present invention discloses a system and method for treating trimethylaluminum residual liquid, wherein the system comprises an inert gas supply device, a heptane storage tank, a trimethylaluminum source tank, a vermiculite holding device, a push branch, a ventilation branch, a heptane flow pipeline, an exhaust pipeline, and a drainage pipeline. The inert gas supply device is connected to the heptane storage tank and the trimethylaluminum source tank via a push branch. Through the operation of the system, it is ensured that the heptane and residual liquid are mixed under air isolation and then slowly discharged to the vermiculite holding device through the drainage pipeline, and then all the mixed liquid is pressed out into the vermiculite, and the operation is repeated until the residual liquid accounts for less than 10%, and then poured out from the pouring port into the vermiculite holding device, and then ignited and slowly burned. The entire treatment system is safe for personnel and the environment, easy to operate, and does not generate other pollutants. The cost of the entire system is low.

Description

Technical Field

[0001] The present invention relates to the technical field of back passivation of crystalline silicon solar cells, in particular to a system and method for treating trimethylaluminum residual liquid. Background Art

[0002] In the photovoltaic industry, crystalline silicon cells typically have a conversion efficiency of no more than 19.5%. However, cells using an Al2O3 back passivation process can achieve conversion efficiencies exceeding 20.5%, considered high-efficiency cells in the industry. Trimethylaluminum (TMA) is the most important liquid source used in the back passivation process for crystalline silicon cells.

[0003] Since TMA liquid source supply systems have only been used in small quantities in China in the past one or two years, the problem of removing the buffer tank to clean the residual liquid inside has not yet been encountered, and there is no mature technical solution for safely handling the residual liquid in the buffer tank. With the large-scale launch of PERC back passivation technology in the photovoltaic industry, more and more TMA supply systems will be put into operation. After the system has been in operation for a long time, the problem of contamination of the inner surface of the buffer tank will be encountered, and there is an urgent need to develop a solution for safely handling the residual liquid in the liquid source buffer tank. Summary of the Invention

[0004] In view of this, the technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a system for safely treating residual liquid in a liquid source buffer tank of trimethylaluminum, and a method for safely treating residual liquid in a liquid source buffer tank using the system.

[0005] The present invention solves the above problems through the following technical means:

[0006] The present invention provides a trimethylaluminum residual liquid treatment system, comprising an inert gas supply device, a heptane storage tank, a trimethylaluminum source tank, a vermiculite holding device, a push branch, a ventilation branch, a heptane flow pipeline, an exhaust pipeline, and a liquid discharge pipeline;

[0007] The gas outlet of the inert gas supply device is provided with a pressure reducing valve;

[0008] The heptane storage tank is provided with a first valve at the top air inlet, a second valve at the top exhaust port, a third valve at the bottom liquid discharge port, and a first sealing flange at the top liquid filling port;

[0009] The trimethylaluminum source tank has a top liquid inlet with valve 4, a top exhaust port with valve 5, a top liquid outlet with valve 6, and a bottom portion connected to a liquid outlet pipe leading to the bottom of the tank, and a top liquid pouring port with sealing flange 2;

[0010] The push branch also includes a push main pipe and a first push branch pipe and a second push branch pipe respectively provided at one end. The push main pipe is connected to the pressure reducing valve. One end of the first push branch pipe is connected to valve 1, and one end of the second push branch pipe is provided with valve 7.

[0011] The ventilation branch further includes a ventilation main pipe and a first ventilation branch pipe and a second ventilation branch pipe respectively provided at one end. The ventilation main pipe is connected to the valve five. One end of the first ventilation branch pipe is connected to the valve seven. One end of the second ventilation branch pipe is provided with a valve eight. The other end of the valve eight is connected to the exhaust pipe. The other end of the exhaust pipe extends into the vermiculite holding device.

[0012] One end of the heptane flow pipeline is connected to valve three, and the other end is connected to valve four;

[0013] One end of the drainage pipeline is connected to valve 6, and the other end extends into the vermiculite containing device.

[0014] Furthermore, the inert gas supply device is a nitrogen cylinder.

[0015] Furthermore, the push branch, ventilation branch, drain pipeline, and exhaust pipeline are 1 / 4″ stainless steel pipes.

[0016] Furthermore, the heptane flow line is a 1 / 4″ plastic transparent hose.

[0017] Furthermore, valves one to eight are manual valves.

[0018] The present invention provides a method for treating trimethylaluminum residual liquid, comprising the following steps:

[0019] Step a: removing the trimethylaluminum source tank from the trimethylaluminum supply system through an inert gas displacement and pushing operation;

[0020] Step b: Under the premise of completely isolating from air, slowly add the heptane organic solvent into the trimethylaluminum source tank and fully mix it with the trimethylaluminum residual liquid;

[0021] Step c: Slowly and continuously pressing the mixed liquid in the trimethylaluminum source tank into the vermiculite pile by inert gas pressure until the mixed liquid is fully pressurized;

[0022] Step d, repeating steps b and c until the ratio of trimethylaluminum residual liquid to heptane is less than 10%, and pouring the residual liquid into the vermiculite pile from the top pouring port;

[0023] Step e, igniting and burning the mixed liquid in the vermiculite;

[0024] Step f, using an inert gas to blow dry the inner wall of the trimethylaluminum source tank.

[0025] The trimethylaluminum residual liquid treatment system of the present invention is operated according to a trimethylaluminum residual liquid treatment method, ensuring that heptane and residual liquid are mixed in an air-tight state and then slowly discharged into a vermiculite holding device through a liquid discharge pipeline. The mixed liquid is then completely extruded into the vermiculite. This operation is repeated until the residual liquid accounts for less than 10%. The liquid is then poured out from a liquid pouring port into the vermiculite holding device and then ignited and slowly burned. The entire system is safe for personnel and the environment, easy to operate, and does not generate other pollutants. The entire system is low-cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention will be further described below with reference to the accompanying drawings and examples.

[0027] Figure 1 Schematic diagram of the structure of an embodiment of the present invention;

[0028] Figure numerals: 1-nitrogen bottle, 11-pressure reducing valve, 2-heptane storage tank, 201-valve one, 202-valve two, 203-valve three, 21-sealing flange one, 3-buffer tank containing TMA residual liquid, 304-valve four, 305-valve five, 306-valve six, 31-liquid outlet pipe, 32-sealing flange two, 4-vermiculite holding device, 5-push branch, 51-push main pipe, 52-first push branch, 53-second push branch, 507-valve seven, 6-ventilation branch, 61-ventilation main pipe, 62-first ventilation branch, 63-second ventilation branch, 608-valve eight, 7-plastic transparent hose, 8-exhaust pipe, 9-drainage pipe. DETAILED DESCRIPTION

[0029] The following will be combined Figure 1 The present invention is described in detail. The trimethylaluminum residual liquid treatment system described in this embodiment specifically includes a nitrogen cylinder 1, a heptane storage tank 2, a buffer tank containing TMA residual liquid 3, a vermiculite holding device 4, a push branch 5, a ventilation branch 6, a plastic transparent hose 7, an exhaust pipe 8, and a drainage pipe 9;

[0030] The nitrogen cylinder 1 is provided with a pressure reducing valve 11 at its gas outlet;

[0031] The heptane storage tank 2 is provided with a valve 1 201 at the top air inlet, a valve 202 at the top exhaust port, a valve 3 203 at the bottom liquid discharge port, and a sealing flange 1 21 at the top liquid filling port;

[0032] The top liquid inlet of the buffer tank 3 containing the residual TMA liquid is provided with a valve 4 304, the top exhaust port is provided with a valve 5 305, the top liquid outlet is provided with a valve 6 306 and the lower part is connected to the liquid outlet pipe 31 leading to the bottom of the tank, and the top liquid pouring port is provided with a sealing flange 2 32;

[0033] The push branch 5 also includes a push main pipe 51 and a first push branch pipe 52 and a second push branch pipe 53 respectively provided at one end. The push main pipe 51 is connected to the pressure reducing valve 11. One end of the first push branch pipe 52 is connected to valve 1 201. One end of the second push branch pipe 53 is provided with valve 7 507.

[0034] The ventilation branch 6 also includes a ventilation main pipe 61 and a first ventilation branch pipe 62 and a second ventilation branch pipe 63 provided at one end. The ventilation main pipe 61 is connected to the valve 5 305. One end of the first ventilation branch pipe 62 is connected to the valve 7 507. One end of the second ventilation branch pipe 63 is provided with a valve 8 608. The other end of the valve 8 608 is connected to the exhaust pipe 8. The other end of the exhaust pipe 8 extends into the vermiculite holding device 4.

[0035] One end of the plastic transparent hose 7 is connected to valve three 203, and the other end is connected to valve four 304;

[0036] One end of the drainage pipe 9 is connected to the valve 6 306, and the other end extends into the vermiculite containing device 4.

[0037] Nitrogen cylinders are currently the most commonly used inert gas supply devices with low cost and mature operation methods.

[0038] As a further improvement of the above technical solution, the push branch 5, the ventilation branch 6, the drain pipe 8, and the exhaust pipe 9 are 1 / 4" stainless steel pipes. 1 / 4" stainless steel pipes are widely used, reduce the production cost of the equipment, and facilitate maintenance.

[0039] The heptane flow pipeline is a 1 / 4″ plastic transparent hose 7. The use of the plastic transparent hose 7 allows the inflow of heptane to be observed, making it convenient to operate and control the inflow of heptane.

[0040] As a further improvement of the above technical solution, the valve one 201 to valve eight 608 are manual valves. Manual valves are the most common valves, which are simple to produce and easy to maintain, reducing the equipment production cost and are simple and convenient to operate.

[0041] The method for treating trimethylaluminum residual liquid using the above system comprises the following steps:

[0042] Step a: removing the buffer tank 3 containing the TMA residual liquid from the trimethylaluminum supply system through a nitrogen replacement purge operation;

[0043] Step b: Under the premise of complete isolation from air, slowly add the heptane organic solvent into the buffer tank 3 containing the TMA residual liquid and fully mix it with the trimethylaluminum residual liquid;

[0044] Step c: Using nitrogen pressure, the mixed liquid in the buffer tank 3 containing the residual TMA liquid is continuously and slowly pressed out to the vermiculite pile until the mixed liquid is fully pressurized;

[0045] Step d, repeating steps b and c until the ratio of trimethylaluminum residual liquid to heptane is less than 10%, and pouring the residual liquid into the vermiculite pile from the top pouring port;

[0046] Step e, igniting and burning the mixed liquid in the vermiculite;

[0047] Step f, using nitrogen to dry the inner wall of the buffer tank 3 containing the TMA residual liquid.

[0048] The specific operations of the embodiment are as follows:

[0049] First, do the preparatory work. Through the nitrogen replacement purge operation, safely remove the buffer tank 3 containing TMA residual liquid in the centralized supply system, select a 10L empty tank as a heptane storage tank 2, a metal container >50L is used to place vermiculite, and the vermiculite is filled to 50% as a vermiculite holding device 4, 15L of industrial pure heptane, the appropriate amount required for a single buffer tank to handle, a mobile nitrogen bottle 1 purge cart, and several pipelines.

[0050] Steps for treating TMA residual liquid in the buffer tank:

[0051] Step 1: Connect the following pipes as shown in the figure: push branch 5, ventilation branch 6, drain pipe 9 and exhaust pipe 8 of TMA liquid source buffer tank 3. Ensure that the distance between vermiculite holding device 4 and buffer tank 3 is greater than 5 meters, and ensure that all valves on buffer tank 3 are always closed.

[0052] Step 2: Adjust the pressure reducing valve 11 at the outlet of the nitrogen cylinder 1 to an outlet pressure of 0.5 bar, and operate the valve 1 201 and valve 3 203 on the heptane storage tank 2 to open and close them respectively, and circulate and purge the heptane storage tank 2 10 times to replace the air in the heptane storage tank 2, and then close the valve 1 201 and valve 3 203;

[0053] Step 3: Connect the plastic transparent hose 7 between the two storage tanks as shown in the figure. First, connect one end of the plastic transparent hose 7 to the outlet of valve 3 203 of heptane storage tank 2, then open valve 1 201 and valve 3 203. Under continuous nitrogen purge, connect the other end of the transparent hose 7 to the inlet of valve 4 304 of buffer tank 3, and close valve 1 201 and valve 3 203.

[0054] Step 4: Open the top flange 21 of the 10L heptane storage tank 2, pour in about 10L (~6.5kg) of industrial pure heptane, and re-seal the flange 21;

[0055] Step 5: Open and close valve 1 201 and valve 2 202 respectively to circulate and purify the air above the heptane storage tank 2 10 times to replace the air above the liquid in the heptane storage tank 2, and then close valve 1 201 and valve 2 202;

[0056] Step 6: Open valve five 305 and valve eight 608 on the buffer tank 3 to release the gas pressure inside the buffer tank 3. After 1 minute, open valve four 304, then open valve one 201 and valve three 203 in sequence, and slowly press heptane into the TMA buffer tank 3 until all the heptane is squeezed out. The presence of liquid can be determined by observing the transparent hose 7. At the same time, the TMA buffer tank 3 can be gently shaken during the heptane feeding stage. Then, close valve one 201 and valve five 305 in sequence and let it stand for 10 minutes.

[0057] Step 7: Slowly open valve six 306 on the buffer tank, observe the small amount of heptane and TMA mixed liquid squeezed out by the residual pressure in the buffer tank 3, then slowly open valve one 201, and continue to slowly squeeze the mixed liquid in the buffer tank into the vermiculite pile by nitrogen pressure until the mixed liquid is completely squeezed out;

[0058] Step 8: Close all manual valves;

[0059] Step 9: Disassemble the top flange 21 of the 10L heptane storage tank 2, pour in approximately 5L (~3.5kg) of industrial-pure heptane for the second time, and re-seal the flange 21; repeat steps 5, 6, 7, and 8; continue to dilute and dissolve the TMA mixture to remove its harmfulness.

[0060] Step 10: Remove the TMA buffer tank 3, and disassemble the top flange 2 31 of the TMA buffer tank 3, and pour all the heptane residue into the vermiculite holding device 4;

[0061] Step 11: Ignite and burn the mixed liquid in the vermiculite;

[0062] Step 12: Open valve six 306, valve five 305, and valve seven 507 in sequence, and use nitrogen to perform necessary pre-drying treatment on the inner wall of the TMA buffer tank 3.

[0063] After observing the contamination of the inner surface of the TMA buffer tank 3, it was decided to adopt subsequent treatment methods such as alkaline solution and pure water cleaning or electrolytic polishing.

[0064] The gap between the bottom of the buffer tank 3 containing the residual TMA and the outlet pipe is typically 5-10 mm. The approximate volume of the residual liquid can be directly calculated based on the tank body, thereby inferring the amount of heptane used and the number of dilutions. Furthermore, this system can also be applied to the treatment of residual liquids from liquid sources such as SiHCl3, SiCl4, and Zn(C2H5)2. Depending on the type of residual liquid, an appropriate organic solvent can be selected for dissolution and dilution. The system and method used are similar to those of the present invention.

[0065] The trimethylaluminum residual liquid treatment system and method provided by the present invention has low cost for the entire system, is safe for personnel and the environment, is easy to operate, and does not generate other pollutants.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A trimethylaluminum residual liquid treatment system, characterized in that: It includes an inert gas supply device, a heptane storage tank, a trimethyl aluminum source tank, a vermiculite holding device, a push branch, a ventilation branch, a heptane flow pipeline, an exhaust pipeline, and a drainage pipeline, wherein the push branch, the ventilation branch, the drainage pipeline, and the exhaust pipeline are 1 / 4" stainless steel pipes; The gas outlet of the inert gas supply device is provided with a pressure reducing valve, and the inert gas supply device is a nitrogen cylinder; The heptane storage tank is provided with a first valve at the top air inlet, a second valve at the top exhaust port, a third valve at the bottom liquid discharge port, and a first sealing flange at the top liquid filling port; The trimethylaluminum source tank has a top liquid inlet with valve 4, a top exhaust port with valve 5, a top liquid outlet with valve 6, and a bottom portion connected to a liquid outlet pipe leading to the bottom of the tank, and a top liquid pouring port with sealing flange 2; The push branch also includes a push main pipe and a first push branch pipe and a second push branch pipe respectively provided at one end. The push main pipe is connected to the pressure reducing valve. One end of the first push branch pipe is connected to valve 1, and one end of the second push branch pipe is provided with valve 7. The ventilation branch further includes a ventilation main pipe and a first ventilation branch pipe and a second ventilation branch pipe respectively provided at one end. The ventilation main pipe is connected to the valve five. One end of the first ventilation branch pipe is connected to the valve seven. One end of the second ventilation branch pipe is provided with a valve eight. The other end of the valve eight is connected to the exhaust pipe. The other end of the exhaust pipe extends into the vermiculite holding device. One end of the heptane flow line is connected to valve three, and the other end is connected to valve four. The heptane flow line is a 1 / 4" plastic transparent hose; One end of the drainage pipeline is connected to valve 6, and the other end extends into the vermiculite containing device.

2. A trimethylaluminum residual liquid treatment system as claimed in claim 1, characterized in that: The valves 1 to 8 are manual valves.

3. A method for treating trimethylaluminum residual liquid, using the trimethylaluminum residual liquid treatment system according to any one of claims 1 to 2, characterized in that: The following steps are included: Step a: removing the trimethylaluminum source tank from the trimethylaluminum supply system through an inert gas replacement purge operation; Step b: Under the premise of completely isolating from air, slowly add the heptane organic solvent into the trimethylaluminum source tank and fully mix it with the trimethylaluminum residual liquid; Step c: Slowly and continuously pressing the mixed liquid in the trimethylaluminum source tank into the vermiculite pile by inert gas pressure until the mixed liquid is fully pressurized; Step d, repeating steps b and c until the ratio of trimethylaluminum residual liquid to heptane is less than 10%, and pouring the residual liquid into the vermiculite pile from the top pouring port; Step e, igniting and burning the mixed liquid in the vermiculite; Step f, using an inert gas to blow dry the inner wall of the trimethylaluminum source tank.

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