Polycrystalline silicon by-product high-boiling conversion recovery system

Abstract

The utility model discloses a polycrystalline silicon by-product high-boiling conversion recovery system which comprises a concentration tower, a conversion kettle, a heavy component removal tower, a tail gas deep freezer, a first return tank and a second return tank, a top gas-phase outlet of the concentration tower is connected with a gas inlet of the first reflux tank through a concentration cooler, a bottom liquid-phase outlet of the concentration tower is connected with the conversion kettle, and a top gas-phase outlet of the conversion kettle is connected with the gas inlet of the first reflux tank through a conversion cooler; a liquid outlet of the first reflux tank is connected with an inlet of a first reflux pump; a third path of an outlet of the first reflux pump enters the middle of the de-heavy tower; and a top gas phase outlet of the heavy component removal tower is connected with a gas inlet of the second reflux tank through a cooler. The investment is small, the energy consumption is low, the supercooling sensible heat of the tail gas deep cooler is used for cooling the de-heavy tower, and the cooling capacity of the non-condensable gas of the tail gas can be well recovered; the concentration tower and the conversion kettle share the reflux tank and the reflux pump, so that the one-time investment cost of the device is reduced and the equipment space is reduced.

Description

Technical Field

[0001] The utility model belongs to the technical field of chemical silicon-based materials, and particularly relates to a high-boiling conversion and recovery system for polysilicon by-products. Background Art

[0002] Polysilicon, as the basic raw material in the photovoltaic industry, will produce high-boiling substances as by-products during the preparation process. These high-boiling substances are mainly composed of chlorosilanes containing structures such as Si-Si bonds and Si-O-Si bonds and cannot be directly utilized. Therefore, the cracking and recovery of high-boiling substances have become the focus of attention.

[0003] The scale of the device for the high-boiling cracking process is relatively small compared to the main device. Therefore, while realizing the cracking and recovery of high-boiling substances, it is necessary to simplify the process equipment as much as possible, reduce the initial investment, and reduce the continuous consumption of energy. Summary of the Invention

[0004] The purpose of the utility model is to solve the above technical problems and provide a high-boiling conversion and recovery system for polysilicon by-products with a simple system, which can effectively recover the process gas cooling capacity and reduce the refrigerant consumption.

[0005] To achieve the above purpose, the utility model provides a high-boiling conversion and recovery system for polysilicon by-products, including a concentration tower, a conversion kettle, a deweighting tower, a tail gas deep cooler, a first reflux tank and a second reflux tank; the gas outlet at the top of the concentration tower is connected to the gas inlet of the first reflux tank through a concentration cooler, the liquid outlet at the bottom of the concentration tower is connected to the conversion kettle, and the gas outlet at the top of the conversion kettle is connected to the gas inlet of the first reflux tank through a conversion cooler; the liquid outlet of the first reflux tank is connected to the inlet of the first reflux pump, and the third path of the first reflux pump enters the middle of the deweighting tower; the gas outlet at the top of the deweighting tower is connected to the gas inlet of the second reflux tank through a cooler, and the liquid outlet of the second reflux tank is refluxed to the upper part of the deweighting tower through a second reflux pump; the gas outlets of the first reflux tank and the second reflux tank are both connected to the tube-side inlet of the tail gas deep cooler.

[0006] Further, the liquid outlet at the bottom of the concentration tower enters the conversion kettle through a height difference.

[0007] Further, the first path of the outlet of the first reflux pump is refluxed to the upper part of the concentration tower, and the second path of the outlet of the first reflux pump is refluxed to the upper part of the conversion kettle.

[0008] Further, the gas outlet at the top of the deweighting tower is communicated with the tube-side inlet of the first cooler, the tube-side outlet of the first cooler is connected to the shell-side inlet of the second cooler, and the shell-side outlet of the second cooler is connected to the gas inlet of the second reflux tank.

[0009] Further, the tube-side outlet of the tail gas deep cooler is connected to the shell-side inlet of the first cooler.

[0010] Compared with the prior art, the beneficial effects of the present utility model are as follows:

[0011] 1) The recovery system device of the present utility model has a small investment and low energy consumption: using the subcooled sensible heat of the tail gas deep cooler to supply cooling to the gas phase at the top of the deweighting tower can well recover the cold energy of the non-condensable gas in the tail gas; at the same time, due to reheating, the temperature after reheating is higher than -20°C, and the pipelines and downstream equipment for waste gas flushing can be changed from low-temperature steel / stainless steel to ordinary carbon steel, greatly reducing the initial investment in equipment and pipelines;

[0012] 2) The concentration tower and the conversion kettle share a reflux tank and a reflux pump, reducing the initial investment cost of the device and the equipment space;

[0013] 3) The heavy components in the concentration tower are transported to the conversion kettle through the pressure difference provided by high pressure, reducing the equipment and cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic flow diagram of the high-boiling conversion recovery system for polysilicon by-products of the present utility model. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0015] The present utility model will be further described below in conjunction with the drawings and specific embodiments.

[0016] As Figure 1 shown, the high-boiling conversion recovery system for polysilicon by-products includes a concentration tower 1, a conversion kettle 2, a deweighting tower 4, a tail gas deep cooler 5, a first reflux tank 8, and a second reflux tank 11; the gas outlet at the top of the concentration tower 1 is connected to the gas inlet of the first reflux tank 8 through a concentration cooler 6, and the liquid outlet of the first reflux tank 8 is connected to the inlet of the first reflux pump 9; the liquid outlet at the bottom of the concentration tower 1 enters the conversion kettle 2 through a height difference, and the gas outlet at the top of the conversion kettle 2 is connected to the gas inlet of the first reflux tank 8 through a conversion cooler 7; the first way of the outlet of the first reflux pump 9 returns to the upper part of the concentration tower 1, the second way of the outlet of the first reflux pump 9 returns to the upper part of the conversion kettle 2, and the third way of the outlet of the first reflux pump 9 enters the middle part of the deweighting tower 4; the gas outlet at the top of the deweighting tower 4 is connected to the inlet of the tube side of the first cooler 3, the outlet of the tube side of the first cooler 3 is connected to the inlet of the shell side of the second cooler 10, the outlet of the shell side of the second cooler 10 is connected to the gas inlet of the second reflux tank 11, and the liquid outlet of the second reflux tank 11 returns to the upper part of the deweighting tower 4 through a second reflux pump 12; the gas outlets of the first reflux tank 8 and the second reflux tank 11 are both connected to the inlet of the tube side of the tail gas deep cooler 5, and the outlet of the tube side of the tail gas deep cooler 5 is connected to the inlet of the shell side of the first cooler 3.

[0017] 1.25 t / h of high-boiling substances (temperature ~65 °C, pressure 0.6 MPa (G)) from slurry treatment enter the concentrator 1. The light-component chlorosilanes (about 40 - 45 °C) separated by concentration in the concentrator 1 are sent to the first reflux drum 8 after passing through the concentration cooler 6. The heavy components in the concentrator 1 enter the conversion kettle 2 through the height difference. After the main heavy component Si2Cl6 is cracked by the catalyst to obtain chlorosilanes, the cracked chlorosilanes and other heavy components that cannot participate in the reaction (such as Si2OCl6) are separated by the boiling point difference (i.e., the chlorosilanes are separated from other heavy components that cannot participate in the reaction). The cracked chlorosilanes, as light components, enter the first reflux drum 8 through the conversion cooler 7; the liquid in the first reflux drum 8 (condensed chlorosilanes + non-condensable gas) is pressurized by the first reflux pump 9 and divided into three paths. Among them, two paths are respectively refluxed to the concentrator 1 and the conversion kettle 2, and the third path is sent to the heavy component removal tower 4 for further separation (chlorosilanes + non-condensable gas); the gas in the first reflux drum 8 (non-condensable gas containing trichlorosilane) is sent to the tail gas cryogenic cooler 5 for cryogenic treatment to further recover chlorosilanes. The chlorosilanes separated by the heavy component removal tower 4 are condensed by passing through the first cooler 3 and the second cooler 10 in sequence and then sent to the second reflux drum 11. A part of the liquid in the second reflux drum 11 (condensed chlorosilanes + non-condensable gas) is refluxed to the heavy component removal tower 4 by the second reflux pump 12 for further purification, and a part is sent out of the boundary for further separation; the gas in the second reflux drum 11 (non-condensable gas containing trichlorosilane) is sent to the tail gas cryogenic cooler 5 for cryogenic treatment to further recover chlorosilanes, and at the same time, it provides cooling capacity for the first cooler 3 and then is sent out of the outside world.

[0018] The energy-saving effect is shown in the following table

[0019]

Claims

1. A high-boiling conversion and recovery system for polysilicon by-products, characterized in that: It includes a concentration tower (1), a conversion kettle (2), a deweighting tower (4), a tail gas deep cooler (5), a first reflux drum (8) and a second reflux drum (11); the top gas phase outlet of the concentration tower (1) is connected to the gas inlet of the first reflux drum (8) through a concentration cooler (6), the bottom liquid phase outlet of the concentration tower (1) is connected to the conversion kettle (2), and the top gas phase outlet of the conversion kettle (2) is connected to the gas inlet of the first reflux drum (8) through a conversion cooler (7); the liquid outlet of the first reflux drum (8) is connected to the inlet of the first reflux pump (9), and the third path of the outlet of the first reflux pump (9) enters the middle of the deweighting tower (4); the top gas phase outlet of the deweighting tower (4) is connected to the gas inlet of the second reflux drum (11) through a cooler, and the liquid outlet of the second reflux drum (11) is refluxed to the upper part of the deweighting tower (4) through a second reflux pump (12); the gas outlets of the first reflux drum (8) and the second reflux drum (11) are both connected to the tube side inlet of the tail gas deep cooler (5).

2. The high-boiling conversion and recovery system for polysilicon by-products according to claim 1, wherein: The bottom liquid phase outlet of the concentration tower (1) enters the conversion kettle (2) through a height difference.

3. The polysilicon by-product high-boiling conversion and recovery system according to claim 1, wherein: The first path of the outlet of the first reflux pump (9) is refluxed to the upper part of the concentration tower (1), and the second path of the outlet of the first reflux pump (9) is refluxed to the upper part of the conversion kettle (2).

4. The high-boiling conversion and recovery system for polysilicon by-products according to claim 1, wherein: The top gas phase outlet of the deweighting tower (4) is communicated with the tube side inlet of the first cooler (3), the tube side outlet of the first cooler (3) is connected to the shell side inlet of the second cooler (10), and the shell side outlet of the second cooler (10) is connected to the gas inlet of the second reflux drum (11).

5. The polysilicon by-product high-boiling conversion and recovery system according to claim 4, wherein: The tube side outlet of the tail gas deep cooler (5) is connected to the shell side inlet of the first cooler (3).

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