Gas phase washing system of slurry dryer

Abstract

The utility model discloses a gas phase washing system of a slurry dryer, which belongs to the technical field of polycrystalline silicon production and comprises the slurry dryer and a dryer condenser, and a dryer sieve-plate tower is arranged between the slurry dryer and the dryer condenser. A heat source and spraying liquid are connected into the dryer sieve-plate tower so as to wash a gas-phase substance output by the slurry dryer; the gas-phase substance washed by the drying machine sieve-plate tower enters a drying machine condenser to be condensed, and the drying machine condenser outputs part of condensate to the drying machine sieve-plate tower to serve as spraying liquid to implement washing. According to the utility model, the dryer sieve-plate tower is arranged in front of the pipeline through which the gas-phase material of the slurry dryer enters the dryer condenser, and most impurities in the gas-phase material output by the slurry dryer are separated by utilizing the boiling point, so that the condition that the condenser is frequently blocked can be effectively relieved.

Description

Technical Field

[0001] The utility model relates to a gas-phase washing system, in particular to a gas-phase washing system for a slurry dryer. Background Art

[0002] During the production of polysilicon by cold hydrogenation, a large amount of slurry is discharged. These slurries are collected in a slurry settling tank and then added to a rake dryer in multiple batches or once. The amount added each time is about half of the effective volume of the equipment. Then, the liquid chlorosilane in the slurry is evaporated by indirect heating with steam, and the solid slag and high-boiling substances are concentrated as impurities and discharged intermittently for hydrolysis; the chlorosilane vapor is recovered after being condensed by circulating water, thereby improving the recovery rate of slurry treatment. In the prior art, Patent CN115106045A discloses a slurry high-boiling treatment system, including a vacuum filter, an evaporation dryer, a neutralization tank, a rectification column, and a cracking reaction kettle; after the slurry material comes from cold hydrogenation, it is separated by filtration to obtain solid materials and clear liquid respectively; the solid materials are dried by evaporation to form solid filter residues, and the filter residues are sent to a sewage treatment station after hydrolysis and alkali neutralization; the gas-phase materials generated during the evaporation and drying process are condensed into clear liquid, combined with the clear liquid obtained in the previous step for treatment, purified by a rectification column, and chlorosilane and hydrogen chloride are taken out from the top of the column for further separation; the high-boiling substances are taken out from the bottom of the column and catalytically cracked to obtain chlorosilane. The chlorosilane enters the rectification column in a gas phase for separation and purification, and the unreacted high-boiling substances are repeatedly rectified and catalytically cracked until all are converted into chlorosilane.

[0003] However, during the operation of the dryer, the components of the gas-phase output after evaporation not only include chlorosilane, but also high-boiling substances and metal chlorides at the same time. These two substances enter the subsequent condensation channel together with chlorosilane and become solid impurities, which easily cause blockage of the condenser pipeline, thus affecting the recovery of chlorosilane. Therefore, a gas-phase washing system for a slurry dryer is specifically proposed in this solution. Summary of the Utility Model

[0004] The utility model aims to solve the problem that the mixed impurities in the gas phase evaporated by the slurry dryer in the prior art enter the condenser pipeline, resulting in frequent blockage of the condenser, and proposes a gas-phase washing system for a slurry dryer. By adding a sieve tray tower to wash the gas phase output by the dryer to reduce impurities, the blockage of the condenser is effectively alleviated.

[0005] In order to achieve the above-mentioned utility model purpose, the technical solution of the utility model is as follows:

[0006] A gas-phase washing system for a slurry dryer, comprising a slurry dryer and a dryer condenser. A dryer sieve plate column is arranged between the slurry dryer and the dryer condenser. The dryer sieve plate column accesses a heat source and a spraying liquid to wash the gas-phase substances output by the slurry dryer. The gas-phase substances washed by the dryer sieve plate column enter the dryer condenser for condensation. The dryer condenser outputs part of the condensate to the dryer sieve plate column as the spraying liquid for washing.

[0007] Further, the slurry dryer is provided with a solid-phase substance outlet. The solid filter residue obtained after drying by the slurry dryer enters the hydrolysis tank through the solid-phase substance outlet for hydrolysis.

[0008] Further, the bottom of the dryer sieve plate column is provided with a solid-phase substance outlet. The impurities and a small amount of chlorosilane mixture washed by the dryer sieve plate column enter the slurry dryer again through the solid-phase substance outlet for evaporation and drying.

[0009] Further, a material inlet is arranged on the side wall of the dryer sieve plate column near the bottom, and the material inlet is connected to the gas-phase substance outlet of the slurry dryer.

[0010] Further, the dryer condenser is connected to a condensate collection tank, and a filter is arranged on the pipeline where the dryer condenser accesses the condensate collection tank.

[0011] Further, the dryer sieve plate column uses steam as the heat source, and a heat preservation jacket is also arranged at the bottom of the dryer sieve plate column.

[0012] Further, a branch pipeline is also connected to the output pipeline of the condensate collection tank for transporting the product liquid, and the branch pipeline accesses the de-high-boiling tower.

[0013] The working principle of the present utility model is as follows:

[0014] The solid residue and high-boiling substances evaporated at 125°C by the slurry dryer are taken as impurities, concentrated, intermittently discharged and then hydrolyzed. The gas-phase substances (chlorosilane + high-boiling substances + metal chlorides) generated by evaporation and drying enter the dryer sieve plate column. Under the temperature condition of about 120°C, most of the high-boiling substances and metal chlorides in the gas-phase substances are separated by spraying and washing with the condensate, and enter the slurry dryer again through the solid-phase substance outlet together with a small amount of chlorosilane for evaporation and separation. Most of the chlorosilane and a small amount of impurities enter the condenser through the gas-phase substance outlet at the top of the sieve plate column for condensation. The condensate enters the condensate collection tank after being filtered by the filter. Part of it is sent to the de-high-boiling tower as the product liquid through the condensate transfer pump, and the other part is input into the sieve plate column as the spraying liquid to wash the gas-phase substances, and so on in a cycle.

[0015] In summary, the present utility model has the following advantages:

[0016] 1. The utility model effectively alleviates the frequent blockage of the condenser by setting a dryer sieve tray tower before the pipeline where the gas phase substances of the slurry dryer enter the dryer condenser, and separating most of the impurities in the gas phase substances output by the slurry dryer by using the boiling point.

[0017] 2. In the utility model, part of the product liquid is used as the spray liquid in the dryer sieve tray tower to wash the gas phase substances entering the sieve tray tower. The washed materials contain most of the impurities and a small amount of chlorosilane. This part of the materials enters the slurry dryer again through the solid phase material outlet of the dryer sieve tray tower for evaporation and separation, achieving the effect of cyclic washing.

[0018] 3. In the utility model, a filter is arranged on the pipeline where the dryer condenser is connected to the condensate collection tank. The filter can filter out impurities such as solid metal chlorides in the condensate (product liquid), and can control the metal impurities in the product liquid to below 1000 ppb. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic structural diagram of the gas phase washing system of the utility model.

[0020] In the figure:

[0021] D01 - dryer

[0022] T01 - high boiling point removal tower

[0023] T04 - dryer sieve tray tower

[0024] E03 - dryer condenser

[0025] P06 - condensate transfer pump

[0026] V10 - condensate collection tank

[0027] V05 - hydrolysis tank

[0028] F01 - filter DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] In order to more clearly illustrate the utility model, the following further describes the utility model in conjunction with the preferred embodiments and the drawings. Those skilled in the art should understand that the following specifically described content is illustrative rather than restrictive, and should not be used to limit the protection scope of the utility model.

[0030] The slurry dryer is a device for treating the slurry discharged from the cold hydrogenation production process of polysilicon. By indirectly heating with steam, the liquid chlorosilane in the slurry is evaporated, and the solid slag and high-boiling substances are concentrated as impurities and discharged intermittently for hydrolysis; the chlorosilane vapor is recovered after being condensed by circulating water, thereby improving the recovery rate of slurry treatment. During the actual operation of the slurry dryer, the components output as gas phase not only include chlorosilane, but also high-boiling substances and metal chlorides. These two substances enter the subsequent condensation recovery channel with chlorosilane and become solid impurities, which easily cause blockage of the condenser, thus affecting the recovery of chlorosilane.

[0031] Therefore, aiming at the problem that high-boiling substances and metal chlorides and other impurities exist in the gas phase generated by the evaporation of the slurry dryer and are deposited in the condenser pipeline to cause blockage, the present utility model specifically proposes a gas phase washing system for the slurry dryer.

[0032] As Figure 1 shown, the gas phase washing system of the present utility model includes a slurry dryer D01, a dryer sieve plate tower T04, a dryer condenser E03, a condensate collection tank V10, and a condensate transfer pump P06. Among them, the slurry dryer D01, the dryer sieve plate tower T04, the dryer condenser E03, and the condensate collection tank V10 are connected in sequence, the condensate collection tank V10 is connected to the dryer sieve plate tower T04, and the condensate transfer pump P06 is connected to the pipeline where the condensate collection tank V10 accesses the dryer sieve plate tower T04.

[0033] The slurry dryer D01 is used to evaporate and dry the incoming slurry. The solid phase outlet of the dryer is connected to the hydrolysis tank V05, and the gas phase outlet is connected to the dryer sieve plate tower T04. The solid filter residue obtained by evaporation and drying enters the hydrolysis tank V05 from the solid phase outlet, and the gas phase during the evaporation and drying process enters the dryer sieve plate tower T04 for washing.

[0034] In this embodiment, the dryer sieve plate tower T04 uses steam as the heat source. Preferably, a heat preservation jacket is also provided on the outer wall of the bottom of the sieve plate tower to ensure a constant heat source temperature.

[0035] A material inlet is provided on the side wall near the bottom of the dryer sieve plate tower T04. This material inlet is connected to the gas phase outlet of the slurry dryer D01. The gas phase output by the evaporation of the slurry dryer D01 enters the dryer sieve plate tower T04 through the material inlet, and the impurities and chlorosilane in the gas phase are separated by boiling point.

[0036] A gas phase outlet is provided in the tower part of the dryer sieve plate tower T04. This gas phase outlet is connected to the inlet of the dryer condenser E03. The high-temperature gas phase chlorosilane and a small amount of impurities separated by the dryer sieve plate tower T04 enter the dryer condenser E03 and become low-temperature liquid chlorosilane.

[0037] The condensate collection tank V10 is connected to the outlet of the dryer condenser E03 to collect the condensed low-temperature liquid chlorosilane.

[0038] Furthermore, a filter is provided on the pipeline connecting the dryer condenser E03 to the condensate collection tank V10 to filter out the solid metal chlorides in the condensate.

[0039] In this embodiment, a spray inlet is provided on the side wall of the dryer sieve plate column T04 near the top of the tower. The outlet of the condensate collection tank V10 is connected to the spray inlet on the dryer sieve plate column T04. A part of the condensate in the condensate collection tank V10 is pumped into the dryer sieve plate column T04 as spray liquid to wash the gas phase substances.

[0040] The utility model can relieve the frequent blockage of the condenser by setting the dryer sieve plate column T04 and separating most of the impurities in the gas phase substances output by the dryer using the boiling point.

[0041] Furthermore, a branch pipeline is also connected to the output pipeline of the condensate collection tank V10. This branch pipeline is connected to the de-high-boiling tower T01 to further remove the high-boiling substances in the condensate for purification.

[0042] Furthermore, a solid phase material outlet is provided at the bottom of the dryer sieve plate column T04, and this solid phase material outlet is connected to the slurry dryer D01. After the gas phase substances entering the sieve plate column are washed, the washing liquid contains most of the impurities and a small amount of chlorosilane. This part of the material enters the slurry dryer D01 through the solid phase material outlet for evaporation and separation again to achieve the effect of cyclic washing.

[0043] The working principle of the utility model is as follows:

[0044] The solid residues and high-boiling substances evaporated at 125°C by the slurry dryer D01 are taken as impurities, concentrated, intermittently discharged and then hydrolyzed. The gas phase substances (chlorosilane + high-boiling substances + metal chlorides) generated by evaporation and drying enter the dryer sieve plate column T04. Under the temperature condition of about 120°C, most of the high-boiling substances and metal chlorides in the gas phase substances are separated out by the spray washing of the condensate, and together with a small amount of chlorosilane, they enter the slurry dryer D01 again through the solid phase material outlet for evaporation and separation. Most of the chlorosilane and a small amount of impurities (high-boiling substances + metal chlorides) enter the condenser through the gas phase material outlet at the top of the sieve plate column for condensation. The condensate enters the condensate collection tank V10 after being filtered by the filter F01. Part of it is sent into the de-high-boiling tower T01 as product liquid by the condensate transfer pump P06, and the other part is input into the sieve plate column as spray liquid to wash the gas phase substances, and so on in a cycle.

[0045] The gas-phase washing system proposed by the present utility model can control the metal impurities in the product liquid (to T01) to below 1000 ppb, control the chlorosilane in the evaporation residual liquid (slurry dryer) to below 3%, and increase the overall slurry yield to over 94%. After the implementation of this project, 424 tons of chlorosilane can be recycled monthly (reported statistics), and the annual economic benefit can reach 50.88 million yuan. If the high-boiling components are further cracked, zero slurry discharge can be basically achieved.

[0046] The above are only the preferred embodiments of the present utility model, and do not impose any form of limitation on the present utility model. Any simple modification or equivalent change made to the above embodiments based on the technical essence of the present utility model shall fall within the protection scope of the present utility model.

Claims

1. A gas-phase washing system for a slurry dryer, comprising a slurry dryer (D01) and a dryer condenser (E03), characterized in that, A dryer sieve plate column (T04) is provided between the slurry dryer (D01) and the dryer condenser (E03). The dryer sieve plate column (T04) is connected to a heat source and a spraying liquid to wash the gaseous substances output by the slurry dryer (D01). The gaseous substances washed by the dryer sieve plate column (T04) enter the dryer condenser (E03) for condensation. The dryer condenser (E03) outputs part of the condensate to the dryer sieve plate column (T04) as the spraying liquid for washing.

2. The gas-phase washing system of a slurry dryer according to claim 1, characterized in that The slurry dryer (D01) is provided with a solid-phase substance outlet. The solid filter residue obtained after drying by the slurry dryer (D01) enters the hydrolysis tank (V05) through the solid-phase substance outlet for hydrolysis.

3. The gas-phase washing system of a slurry dryer according to claim 1, wherein The bottom of the dryer sieve plate column (T04) is provided with a solid-phase substance outlet. The impurities and a small amount of chlorosilane mixture washed by the dryer sieve plate column (T04) enter the slurry dryer (D01) again through the solid-phase substance outlet for evaporation and drying.

4. The gas-phase washing system of a slurry dryer according to claim 1, characterized in that, A material inlet is provided on the side wall near the bottom of the dryer sieve plate column (T04), and the material inlet is connected to the gaseous substance outlet of the slurry dryer (D01).

5. The gas-phase washing system of a slurry dryer according to claim 1, characterized in that, The dryer condenser (E03) is connected to the condensate collection tank (V10), and a filter (F01) is provided on the pipeline where the dryer condenser (E03) is connected to the condensate collection tank (V10).

6. The gas-phase washing system of a slurry dryer according to claim 1, characterized in that The dryer sieve plate column (T04) uses steam as the heat source, and a heat preservation jacket is further provided on the outer wall of the dryer sieve plate column (T04).

7. A gas-phase washing system for a slag slurry dryer according to claim 5, characterized in that, A branch pipeline is further connected to the output pipeline of the condensate collection tank (V10) for transporting the product liquid, and the branch pipeline is connected to the high-boiling tower (T01).

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