Silane rectification column with reduced steam consumption

Abstract

The utility model relates to a kind of silane rectifying column of steam consumption reduction, for separating the product generated by DCS disproportionation reactor, the top of the silane rectifying column is provided with condenser, the kettle of the silane rectifying column is provided with reboiler, the middle part of the silane rectifying column is provided with intermediate reboiler. By increasing intermediate reboiler, low-grade cheap heating medium can be used to gasify the descending liquid, thereby reducing the heat load of the kettle reboiler, reducing the amount of high-temperature heating medium, and further reducing energy costs and operating costs.

Description

Technical Field

[0001] This utility model relates to a distillation and purification apparatus for silane, and in particular to a silane distillation column with reduced steam consumption. Background Technology

[0002] Because silane has a very low boiling point, most impurities in the system are easily discharged from the bottom of the silane tower as heavy components. This is one of the significant advantages of using the silane method to produce high-purity polycrystalline silicon over the Siemens method.

[0003] However, a crucial impurity to consider in the above system is borane (B₂H₆), which has a boiling point of -93°C at normal pressure, very close to the boiling point of silane (-112°C). Borane is primarily produced by the reaction of boron chloride (BCl₃) with silane in disproportionation reactors, TCS columns, and DCS columns. Figure 1 The image shows the temperature distribution data of a silane distillation column, which has 57 trays. The product from the DCS disproportionation reactor enters from the 48th tray. From the 42nd tray to the top, the temperature distribution is essentially linear. This indicates that the bottom of the silane distillation column mainly contains chlorosilanes from the reaction products, with a bottom temperature of 137℃ and a top temperature of -29.1℃, resulting in a total temperature difference of 166.1℃. In the silane distillation column, chlorosilanes (monochlorotrihydrosilane / MCS) are easily separated from silanes, with separation essentially completed by the sixth tray above the feed tray. From the 42nd tray to the top, the temperature change is -28.3℃ to -29.1℃, a difference of only 0.8℃. This suggests that the amount of borane removed from the silane is very low, and the removal of boranes is quite difficult, requiring 42 trays.

[0004] The essence of removing borane from a silane distillation column is to wash away trace amounts of borane from the silane gas by using a liquid with a large reflux ratio. However, a large reflux ratio means a large evaporation and condensation rate, which leads to a large consumption of heat and cold. Therefore, the above-mentioned silane distillation column can be further improved. Utility Model Content

[0005] The technical problem to be solved by this utility model is to provide a silane distillation column with reduced steam consumption, in light of the current state of the technology.

[0006] The technical solution adopted by this utility model to solve the above-mentioned technical problems is as follows: a silane distillation column with reduced steam consumption, used to separate the products generated by the DCS disproportionation reactor, wherein a condenser is provided at the top of the silane distillation column, a reboiler is provided at the bottom of the silane distillation column, and an intermediate reboiler is provided in the middle of the silane distillation column.

[0007] Preferably, the silane distillation column is provided with a feed inlet, and the tray corresponding to the intermediate reboiler is higher than the tray corresponding to the feed inlet.

[0008] Preferably, the tray corresponding to the intermediate reboiler is at least six trays higher than the tray corresponding to the feed inlet. Chlorosilanes and silanes are easily separated, and the separation is essentially completed at the sixth tray above the tray corresponding to the feed inlet. Using this scheme, the intermediate reboiler can reduce the heat load on the reboiler in the column bottom during the separation of silanes and boranes.

[0009] Preferably, the silane distillation column has 57 trays.

[0010] Preferably, the feed inlet corresponds to the 48th tray; the intermediate reboiler corresponds to the 39th tray.

[0011] Preferably, the heat source for the intermediate reboiler includes hot water or steam condensate.

[0012] Compared with the prior art, the advantages of this utility model are: by adding an intermediate reboiler, a low-grade and inexpensive heating medium can be used to vaporize the descending liquid, thereby reducing the heat load of the reboiler and the amount of high-temperature heating medium used, thus reducing energy costs and operating costs. Attached Figure Description

[0013] Figure 1 This is a temperature distribution diagram inside a silane distillation column in the background art;

[0014] Figure 2 This is a partial structural schematic diagram of the silane distillation column with reduced steam consumption in an embodiment of this utility model. Detailed Implementation

[0015] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0016] like Figure 2 The diagram shows a preferred embodiment of the silane distillation column with reduced steam consumption according to this invention. This silane distillation column 1 has 57 trays. The silane distillation column 1 is used to separate the products generated by the DCS disproportionation reactor, where the reaction is 2SiH₂Cl₂==SiH₄+SiHCl₃. A condenser 11 is installed at the top of the silane distillation column 1, and the temperature at the top of the column is -29 to -30°C. A reboiler 12 is installed at the bottom of the silane distillation column 1, and the temperature at the bottom of the column is 82 to 85°C. A feed inlet 13 is provided on the silane distillation column 1, through which the products from the DCS disproportionation reactor enter the silane distillation column 1. The feed inlet 13 corresponds to the 48th tray. An intermediate reboiler 14 is installed in the middle of the silane distillation column 1, corresponding to the 39th tray.

[0017] The products of the DCS disproportionation reactor include chlorosilanes, silanes, and a small amount of boranes. The silane distillation column 1 has a large temperature difference between the top and bottom, and can be divided into two sections. The first section is the distillation separation and purification of chlorosilanes and silanes. Chlorosilanes and silanes are easily separated, and the separation is basically completed at the 42nd tray (sixth tray above the tray corresponding to feed inlet 13). The second section is the rinsing and absorption of boranes by silanes at a high reflux ratio. In this section, the concentration of chlorosilanes at the 39th tray has decreased to the PPM level, and the liquid phase is extracted at the 48th tray. At this point, the liquid phase temperature is below -28°C. Adding the aforementioned intermediate reboiler 14 utilizes a low-grade heat source from the plant (such as hot water or steam condensate) to vaporize the descending liquid, thereby reducing the consumption of high-grade primary steam in the bottom of the column and achieving the goal of reducing energy costs.

[0018] Compared with the prior art, the advantages of this utility model are: by adding an intermediate reboiler 14, a low-grade and inexpensive heating medium can be used to vaporize the descending liquid, thereby reducing the heat load of the reboiler 12 in the tower bottom, reducing the amount of high-temperature heating medium used, and thus reducing energy costs and operating costs.

Claims

1. A silane distillation column with reduced steam consumption for separating products from a DCS disproportionation reactor, wherein a condenser (11) is provided at the top of the silane distillation column (1) and a reboiler (12) is provided at the bottom of the silane distillation column (1), characterized in that: An intermediate reboiler (14) is provided in the middle of the silane distillation column (1).

2. The silane distillation column according to claim 1, characterized in that: The silane distillation column (1) is provided with a feed inlet (13), and the tray corresponding to the intermediate reboiler (14) is higher than the tray corresponding to the feed inlet (13).

3. The silane distillation column according to claim 2, characterized in that: The tray corresponding to the intermediate reboiler (14) is at least 6 trays higher than the tray corresponding to the feed inlet (13).

4. The silane distillation column according to claim 1, characterized in that: The silane distillation column (1) has a total of 57 trays.

5. The silane distillation column according to claim 3, characterized in that: The feed inlet (13) corresponds to the 48th tray; the intermediate reboiler (14) corresponds to the 39th tray.

6. The silane distillation column according to claim 1, characterized in that: The heat source for the intermediate reboiler (14) includes hot water or steam condensate.

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