A combined vacuum system for a single crystal furnace

Abstract

A combined vacuum system for a single crystal furnace includes a vacuum pipeline, at least two sets of vacuum pump groups, and multiple multi-stage Roots vacuum pumps. A vacuum buffer chamber is provided on the vacuum pipeline. The exhaust ports of the multiple multi-stage Roots vacuum pumps are connected in parallel on the vacuum pipeline, located upstream of the vacuum buffer chamber. The inlet of each multi-stage Roots vacuum pump is connected to its corresponding single crystal furnace. Each vacuum pump group consists of a Roots pump and a backing pump connected in series, with the Roots pump located upstream of the backing pump. The inlets of at least two sets of vacuum pump groups are connected in parallel on the vacuum pipeline, located downstream of the vacuum buffer chamber. A first shut-off valve is provided between each vacuum pump group and the vacuum pipeline. This invention has low operating costs, high reliability, and can effectively prevent material waste within the single crystal furnace.

Description

Technical Field

[0001] This invention relates to the field of vacuum pumping, and in particular to a combined vacuum pumping system for a single crystal furnace. Background Technology

[0002] The single crystal furnace is an important piece of equipment in the photovoltaic industry for the single crystal silicon pulling process. In an inert gas environment, polycrystalline materials such as polycrystalline silicon are melted using a graphite heater, and dislocation-free single crystals are grown using the Czochralski method.

[0003] Currently, the photovoltaic industry configures one vacuum pump set (dry screw vacuum pump + Roots pump) for each monocrystalline furnace. A filter tank is installed between the vacuum pump set and the monocrystalline furnace. The configured vacuum pump set needs to operate under two conditions: 1. Quickly extract air from the monocrystalline furnace to achieve a pressure of 20 mTorr; 2. Maintain a pressure of 7-9 Torr when 70-90 SLM of inert gas is introduced into the monocrystalline furnace.

[0004] However, this type of vacuum pump assembly has the following drawbacks:

[0005] 1. If the vacuum pump fails, the expensive materials inside the single crystal furnace will be scrapped in a very short time.

[0006] 2. The vacuum pump set required for a single single crystal furnace is relatively small. The gap between the rotor and the casing of the dry pump and Roots pump in the pump set is extremely small. When the filter tank is damaged, the particles entering the pump can easily cause pump damage.

[0007] Therefore, how to design a high-efficiency and safe vacuum system for single crystal furnaces is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing technologies by providing a combined vacuum system for single crystal furnaces, which is low in cost, highly efficient in vacuuming, and can effectively prevent the scrapping of materials inside the single crystal furnace.

[0009] The technical solution of the present invention is: a combined vacuum pumping system for a single crystal furnace, comprising a vacuum pumping pipeline, at least two sets of vacuum pump sets, and multiple multi-stage Roots vacuum pumps. A vacuum buffer chamber is provided on the vacuum pumping pipeline. The exhaust ports of the multiple multi-stage Roots vacuum pumps are connected in parallel on the vacuum pumping pipeline and located upstream of the vacuum buffer chamber. The air inlet of each multi-stage Roots vacuum pump is used to connect to the corresponding single crystal furnace. The vacuum pump set is composed of a Roots pump and a backing pump connected in series, and the Roots pump is located upstream of the backing pump. The air inlets of at least two sets of vacuum pump sets are connected in parallel on the vacuum pumping pipeline and located downstream of the vacuum buffer chamber. A first shut-off valve is provided between each vacuum pump set and the vacuum pumping pipeline.

[0010] Furthermore, a buffer tank is connected to the vacuum pipeline to form a vacuum buffer chamber.

[0011] Furthermore, the vacuum pumping pipeline is expanded to form a vacuum buffer cavity.

[0012] Preferably, the inlet of the multi-stage Roots vacuum pump is equipped with a first filter canister.

[0013] Preferably, a second shut-off valve is provided at the exhaust port of the multi-stage Roots vacuum pump.

[0014] Preferably, the air inlet of the vacuum pump unit is provided with a second filter canister.

[0015] Furthermore, it also includes a bypass pipe, the upstream end of which is connected to the corresponding crystal pulling furnace, and the downstream end of which is connected to the vacuum pumping pipeline. It is located upstream of the vacuum buffer chamber, and a third shut-off valve is installed on the bypass pipe.

[0016] Preferably, the first shut-off valve, the second shut-off valve, and the third shut-off valve are all automatic shut-off valves.

[0017] The exhaust pressure of the multi-stage Roots vacuum pump is 7-9 Torr.

[0018] The above technical solution has the following beneficial effects:

[0019] 1. The combined vacuum system for single crystal furnaces includes a vacuum pipeline, at least two sets of vacuum pump groups, and multiple multi-stage Roots vacuum pumps. The multi-stage Roots vacuum pumps provide a high vacuum (20 mTorr) for a single single crystal furnace, with low power consumption, high rotor-shell assembly precision, and low particulate material throughput. The vacuum pump groups maintain a low vacuum (7-9 Torr) for multiple single crystal furnaces, with high power consumption, large rotor-shell assembly clearance, and high particulate material throughput. A vacuum buffer chamber is provided on the vacuum pipeline. The exhaust ports of the multiple multi-stage Roots vacuum pumps are connected in parallel on the vacuum pipeline, located upstream of the vacuum buffer chamber. The inlet of each multi-stage Roots vacuum pump is connected to its corresponding single crystal furnace. The multi-stage Roots vacuum pumps rapidly extract air from the corresponding single crystal furnace, bringing the pressure to 20 mTorr. In this state, the single crystal furnace is not fed material. Therefore, even if the multi-stage Roots vacuum pumps fail, there will be no material loss or particulate material extraction, and the service life of the multi-stage Roots vacuum pumps can be significantly extended. The vacuum pump set consists of a Roots pump and a backing pump connected in series, with the Roots pump located upstream of the backing pump. The air inlets of at least two vacuum pump sets are connected in parallel to the vacuum pumping pipeline, located downstream of the vacuum buffer chamber. Each vacuum pump set and the vacuum pumping pipeline is equipped with a first shut-off valve. The vacuum pump sets create negative pressure in the vacuum buffer chamber, thereby creating a centralized vacuum (7-9 Torr) for multiple parallel single crystal furnaces. In this state, the single crystal furnaces are fed, while the multi-stage Roots vacuum pumps stop operating. The vacuum pump sets are not sensitive to the extracted particulate matter, and at least two vacuum pump sets serve as backups for each other. Even if a working vacuum pump set fails, the vacuum buffer tank can maintain a short-term vacuum (7-9 Torr) for the connected single crystal furnaces, allowing the backup vacuum pump sets to restart and maintain the vacuum (7-9 Torr). This effectively prevents the waste of materials in the single crystal furnaces and greatly improves the safety and stability of the vacuum pumping system. By combining multiple sets of vacuum pumps and multiple multi-stage Roots vacuum pumps to provide centralized vacuum, the efficiency is higher and the cost is lower compared to configuring a single vacuum pump set for a single crystal furnace.

[0020] 2. The inlet of the multi-stage Roots vacuum pump is equipped with a first filter canister as a safeguard to further improve the service life of the multi-stage Roots vacuum pump.

[0021] 3. The exhaust port of the multi-stage Roots vacuum pump is equipped with a second shut-off valve, which can be automatically opened or closed according to actual needs to meet the actual needs of enterprises.

[0022] 4. A second filter canister is installed at the air inlet of the vacuum pump unit as a safeguard to further improve the service life of the vacuum pump unit.

[0023] 5. It also includes a bypass pipe, the upstream end of which is connected to the corresponding crystal pulling furnace, and the downstream end of which is connected to the vacuum pumping pipeline. It is located upstream of the vacuum buffer chamber. A third shut-off valve is installed on the bypass pipe. When the multi-stage Roots vacuum pump is working, the third shut-off valve is in the closed state, allowing the multi-stage Roots vacuum pump to normally pump a high vacuum degree to the connected single crystal furnace. When the multi-stage Roots vacuum pump stops working and the vacuum pump group maintains a low vacuum degree to the connected single crystal furnace, the third shut-off valve opens, allowing the connected single crystal furnace to be directly connected to the vacuum pump group through the bypass pipe. This further reduces the risk of dust accumulation on the multi-stage Roots vacuum pump, reduces the vacuum pumping resistance of the vacuum pump group, and also improves the vacuum pumping efficiency of the vacuum pump group.

[0024] The following description, in conjunction with the accompanying drawings and specific embodiments, provides further details. Attached Figure Description

[0025] Figure 1 This is a connection diagram of the present invention.

[0026] In the attached diagram, 1 is the vacuum pumping line, 2 is the vacuum pump set, 3 is the multi-stage Roots vacuum pump, 4 is the Roots pump, 5 is the backing pump, 6 is the vacuum buffer chamber, 7 is the bypass pipe, 8 is the first filter tank, 9 is the second filter tank, a is the first shut-off valve, b is the second shut-off valve, and c is the third shut-off valve. Detailed Implementation

[0027] Example 1

[0028] See Figure 1This is a specific embodiment of a combined vacuum system for a single crystal furnace. The combined vacuum system for a single crystal furnace includes a vacuum pipeline 1, three sets of vacuum pump groups 2, and twelve multi-stage Roots vacuum pumps 3. Typically, two sets of vacuum pump groups operate and one set is on standby. Alternatively, four sets of vacuum pump groups can be designed according to actual needs, also with two sets operating and two sets on standby. Vacuum pump group 2 consists of a Roots pump 4 and a backing pump 5 connected in series, with the Roots pump 4 positioned upstream of the backing pump 5. The backing pump can be a dry pump or other types of vacuum pumps. The Roots pump and backing pump in the vacuum pump group have relatively high power, while the multi-stage Roots vacuum pump has relatively low power. Compared to low-power pumps, the high-power backing pump and high-power Roots pump have a larger gap between the rotor and the housing, resulting in higher particulate matter throughput. A vacuum buffer chamber 6 is provided on the vacuum pumping pipeline 1. In this embodiment, a buffer tank is connected to the vacuum pumping pipeline 1 to form the vacuum buffer chamber 6. Of course, the vacuum pumping pipeline 1 can also be expanded to form the vacuum buffer chamber 6. The volume of the vacuum buffer chamber is selected according to the actual situation. Generally, if there are more corresponding single crystal furnaces, the volume of the vacuum buffer chamber is designed to be larger; if there are fewer corresponding single crystal furnaces, the volume of the vacuum buffer chamber is designed to be smaller. Twelve multi-stage Roots vacuum pumps 3 are distributed on both sides of the vacuum pumping pipeline 1. That is, six multi-stage Roots vacuum pumps are set on one side of the vacuum pumping pipeline, and the exhaust ports of these multi-stage Roots vacuum pumps are connected in parallel on the vacuum pumping pipeline 1, located upstream of the vacuum buffer chamber 6. The air inlet of each multi-stage Roots vacuum pump 3 is used to connect to the corresponding single crystal furnace. In this embodiment, the exhaust pressure of the multi-stage Roots vacuum pump 3 is 7-9 Torr. The air inlets of the three sets of vacuum pump sets 2 are connected in parallel on the vacuum pumping line 1, located downstream of the vacuum buffer chamber 6. Each vacuum pump set 2 and the vacuum pumping line 1 is provided with a first shut-off valve a, and the first shut-off valve is an automatic shut-off valve.

[0029] To further improve the service life of the multistage Roots vacuum pumps, a first filter tank 8 is installed at the upstream end of each multistage Roots vacuum pump 3.

[0030] To meet the actual needs of enterprises, a second shut-off valve b is installed at the exhaust port of the multi-stage Roots vacuum pump 3. The second shut-off valve is also an automatic shut-off valve.

[0031] To further improve the service life of the vacuum pump unit, a second filter tank 9 is installed at the air inlet of the vacuum pump unit 2.

[0032] To further reduce the risk of dust accumulation in the multi-stage Roots vacuum pump, and to reduce the vacuum pumping resistance and improve the vacuum pumping efficiency, a bypass pipe 7 is also included. Typically, the number of bypass pipes is adapted to the number of multi-stage Roots vacuum pumps. The upstream end of the bypass pipe 7 is connected to the corresponding crystal pulling furnace, and the downstream end of the bypass pipe is connected to the vacuum pumping pipeline 1, located upstream of the vacuum buffer chamber 6. A third shut-off valve c is installed on the bypass pipe, and the third shut-off valve is also an automatic shut-off valve.

[0033] The working principle of this invention is as follows:

[0034] Start the multi-stage Roots vacuum pump to evacuate the corresponding single crystal furnace to a pressure of 20 mTorr; introduce 70-90 SLM of argon gas into the single crystal furnace, turn on the vacuum pump group, turn off the multi-stage Roots vacuum pump, maintain the pressure at 7-9 Torr, and add materials to grow misaligned single crystals.

[0035] According to the applicant's tests, the combined vacuum system of this invention has a total power consumption of 45kW for twelve single crystal furnaces and a single crystal scrap rate of 0.1%. In contrast, the traditional method of configuring one vacuum pump unit per single crystal furnace results in a total power consumption of 54kW for twelve single crystal furnaces and a single crystal scrap rate of 1%.

Claims

1. A combined vacuum system for a single crystal furnace, characterized in that: It includes a vacuum pumping pipeline (1), at least two sets of vacuum pump sets (2), and multiple multi-stage Roots vacuum pumps (3). A vacuum buffer chamber (6) is provided on the vacuum pipeline (1). The inlet of the multi-stage Roots vacuum pump (3) is equipped with a first filter tank (8). The exhaust ports of multiple multi-stage Roots vacuum pumps (3) are connected in parallel on the vacuum pumping pipeline (1), located upstream of the vacuum buffer chamber (6). The inlet of each multi-stage Roots vacuum pump (3) is used to connect to the corresponding single crystal furnace. The vacuum pump assembly (2) consists of a Roots pump (4) and a backing pump (5) connected in series, with the Roots pump (4) positioned upstream of the backing pump (5). The air inlets of at least two sets of vacuum pump sets (2) are connected in parallel on the vacuum pumping pipeline (1) and located downstream of the vacuum buffer chamber (6). Each vacuum pump set (2) and the vacuum pumping pipeline (1) is provided with a first shut-off valve (a). It also includes a bypass pipe (7), the upstream end of which is connected to the corresponding single crystal furnace, and the downstream end of which is connected to the vacuum pumping pipeline (1), located upstream of the vacuum buffer chamber (6), and a third shut-off valve (c) is provided on the bypass pipe.

2. The combined vacuum system for a single crystal furnace according to claim 1, characterized in that: A buffer tank is connected to the vacuum pipeline (1) to form a vacuum buffer chamber (6).

3. The combined vacuum system for a single crystal furnace according to claim 1, characterized in that: The vacuum pumping pipeline (1) is expanded to form a vacuum buffer cavity (6).

4. The combined vacuum system for a single crystal furnace according to claim 1, characterized in that: The exhaust port of the multistage Roots vacuum pump (3) is equipped with a second shut-off valve (b).

5. The combined vacuum system for a single crystal furnace according to claim 1, characterized in that: The vacuum pump unit (2) is equipped with a second filter tank (9) at its air inlet.

6. The combined vacuum system for a single crystal furnace according to claim 4, characterized in that: The first shut-off valve (a), the second shut-off valve (b), and the third shut-off valve (c) are all automatic shut-off valves.

7. The combined vacuum system for a single crystal furnace according to claim 1, characterized in that: The exhaust pressure of the multi-stage Roots vacuum pump (3) is 7-9 Torr.

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