Treatment system for mixed tail gas of chlorosilane and silane

Abstract

A chlorosilane and silane mixed tail gas treatment system comprises a condensing device, the condensing device is used for cooling silane and chlorosilane mixed tail gas, the condensing device is connected with an inlet of a first-stage washing tower through a pipeline, and the top of the first-stage washing tower is connected with an inlet of a second-stage washing tower through a pipeline; the bottom of the first-stage washing tower is connected with an inlet of the first-stage circulating tank through a pipeline; the bottom of the second-stage washing tower is connected with an inlet of the second-stage circulating tank through a pipeline; and the top of the secondary washing tower is connected with the liquid seal tank through a pipeline. According to the utility model, two processes of condensation and multi-stage washing are effectively integrated, and a set of efficient and stable tail gas treatment process flow system is constructed.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the technical field of silicon material production, especially relates to a treatment system for mixed tail gas of chlorosilane and silane. BACKGROUND

[0002] In the modern production process of silicon-based materials such as polysilicon and organosilicon, the generation of mixed tail gas of chlorosilane and silane is an unavoidable link. For example, in the preparation of silane gas by chlorosilane disproportionation method, the tail gas is rich in chlorosilane and silane components. With the rapid expansion of the silicon-based material industry worldwide, the efficiency and environmental protection of tail gas treatment technology have never been more demanding. On the one hand, to meet the increasingly stringent environmental protection standards, it is necessary to minimize the negative impact of tail gas emissions on the ecological environment. On the other hand, from the perspective of resource recycling and cost control, efficient recovery and utilization of valuable substances in the tail gas is imminent.

[0003] The internal characteristics of mixed tail gas of chlorosilane and silane are extremely complex and dangerous. From the chemical properties, chlorosilane has high hydrolysis sensitivity. Once exposed to air, it can undergo hydrolysis reaction and produce smoke. When it comes into contact with water, alcohol, phenol and other compounds containing active hydrogen, it will trigger a violent chemical reaction and release hydrogen chloride gas. Silane belongs to the category of flammable gases, and its reactivity and self-ignition tendency are extremely strong. In the practice of tail gas treatment, if the disposal process is not properly designed or the operation precision is missing, it is easy to induce a series of serious consequences. Not only will it cause persistent and widespread pollution to the surrounding ecological environment, but it may also cause catastrophic accidents such as burning and explosion, posing a direct threat to the life safety of on-site operators and causing huge property losses. Based on this, environmental protection and safety regulations continue to tighten the emission threshold and treatment specifications for such tail gas, which undoubtedly becomes the core driving force for the continuous evolution and innovation of tail gas treatment technology.

[0004] However, the treatment technology for the mixed tail gas of chlorosilane and silane is still in a dilemma at present. Firstly, due to the high similarity in physical properties between chlorosilane and silane, it is difficult to achieve precise separation of the two by using conventional simple physical separation methods such as distillation based on boiling point difference or absorption based on solubility difference. More troublesome is that there is a complex interaction between the two, for example, they can form azeotrope under certain conditions, which greatly increases the technical difficulty and process complexity of separation operation, and advanced and precise separation technology and process are urgently needed to achieve efficient separation. Secondly, at the end of the tail gas treatment process, if the tail gas is in contact with air or other gases and the operating conditions are not properly controlled, it may cause combustion explosion or uncontrolled hydrolysis reaction, which seriously endangers the stability and safety of the system. Thirdly, chlorosilane and its hydrolysis product hydrogen chloride have strong corrosive properties, which puts extremely strict requirements on the material selection of the treatment equipment. If the equipment material is not properly selected or the corrosion prevention treatment measures are not in place, the equipment corrosion will spread rapidly, resulting in a sharp reduction in the service life of the equipment, a substantial increase in equipment maintenance costs, and a serious impact on the economy and sustainability of the entire tail gas treatment system. Fourthly, during the tail gas treatment process, silane reaction may generate some solid products, such as silicon dioxide generated by hydrolysis of chlorosilane. These solid products are prone to deposit and cause blockage in key parts such as pipes, condensers and filters inside the equipment, thereby disrupting the normal operation of the equipment and reducing the processing efficiency and reliability of the system. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a treatment system for mixed tail gas of chlorosilane and silane to solve the problems of high separation difficulty, severe equipment corrosion and many safety hazards in the prior art.

[0006] To solve the above technical problems, the technical scheme adopted by the present application is:

[0007] A treatment system for mixed tail gas of chlorosilane and silane, comprising a condensing device for cooling the mixed tail gas of silane and chlorosilane, the condensing device being connected to the inlet of a first washing tower through a pipeline, and the top of the first washing tower being connected to the inlet of a second washing tower through a pipeline;

[0008] The bottom of the first washing tower is connected to the inlet of a first circulating tank through a pipeline, and the bottom of the second washing tower is connected to the inlet of a second circulating tank through a pipeline;

[0009] The top of the second washing tower is connected to a liquid seal tank through a pipeline.

[0010] Preferably, the bottom of the first circulating tank is connected to a first filter through a pipeline, the first filter is connected to a first circulating pump through a pipeline, and the first circulating pump is used to pump the washing liquid to the spray head in the first washing tower.

[0011] Preferably, the bottom of the secondary circulating tank is connected with the second filter through a pipeline, the second filter is connected with the secondary circulating pump through a pipeline, and the secondary circulating pump is used for pumping the washing liquid to the spray head in the secondary washing tower.

[0012] Preferably, the outlet of the primary circulating pump is provided with a primary waste pipe.

[0013] Preferably, the outlet of the secondary circulating pump is provided with a secondary waste pipe.

[0014] The utility model can achieve the following beneficial effects:

[0015] 1、 the utility model discloses with the condensation and multistage washing synergic process, the accuracy and reliability of separation effect are significantly improved.

[0016] 2、 the utility model discloses the liquid seal tank emptying design, effectively avoids a series of safety risks that the tail gas is directly contacted with air and causes, greatly enhances the operation safety and stability of entire tail gas treatment system.

[0017] 3、 the utility model discloses using calcium hydroxide and sodium hydroxide as washing agent, and adopting ph value monitoring and control system, ensure the stability of washing process, significantly prolong the service life of equipment, reduce equipment maintenance cost and update frequency, improve the economy and sustainability of system. BRIEF DESCRIPTION OF DRAWINGS

[0018] The utility model will be further described below in combination with the drawings and examples:

[0019] Figure 1 It is system structural drawing for the utility model.

[0020] In the drawing: condensing device 1, primary washing tower 2, primary circulating tank 3, primary circulating pump 4, secondary washing tower 5, secondary circulating tank 6, secondary circulating pump 7, liquid seal tank 8, first filter 9, second filter 10. DETAILED DESCRIPTION

[0021] Preferred scheme as Figure 1 Shown, a chlorosilane and silane mixed tail gas's processing system includes: condensing device, washing tower (primary, secondary washing tower), circulating tank (primary, secondary circulating tank, is equipped with ph meter), reflux pump (primary, secondary reflux pump) and liquid seal tank.Specifically, condensing device 1 is used to cool silane and chlorosilane mixed tail gas, and condensing device 1 is connected with the inlet of primary washing tower 2 through a pipeline, and the top of primary washing tower 2 is connected with the inlet of secondary washing tower 5 through a pipeline;

[0022] The bottom of the first washing tower 2 is connected with the inlet of the first circulating tank 3 through a pipeline, and the bottom of the second washing tower 5 is connected with the inlet of the second circulating tank 6 through a pipeline.

[0023] The top of the second washing tower 5 is connected with the liquid seal tank 8 through a pipeline.

[0024] Specifically, the bottom of the first circulating tank 3 is connected with the first filter 9 through a pipeline, the first filter 9 is connected with the first circulating pump 4 through a pipeline, and the first circulating pump 4 is used for pumping the washing liquid to the spray head in the first washing tower 2. The bottom of the second circulating tank 6 is connected with the second filter 10 through a pipeline, the second filter 10 is connected with the second circulating pump 7 through a pipeline, and the second circulating pump 7 is used for pumping the washing liquid to the spray head in the second washing tower 5. The outlet of the first circulating pump 4 is provided with a first waste pipe. The outlet of the second circulating pump 7 is provided with a second waste pipe.

[0025] The system realizes the effective separation of chlorosilane and silane through multiple process steps such as condensation, washing and liquid sealing. The washing tower (including the first washing tower 2 and the second washing tower 5) is a key device for treating tail gas. In the washing tower, the gas flows from bottom to top, and the washing liquid is sprayed from top to bottom, forming a gas-liquid countercurrent flow contact mode. This mode can increase the contact area and contact time, and improve the efficiency of treating tail gas. At the same time, different components in the mixed tail gas will react with the chemicals in the washing liquid to form different compounds, thereby achieving the effect of treating the mixed tail gas.

[0026] The working principle of the system is as follows:

[0027] First, the chlorosilane and silane mixed tail gas is preliminarily separated from most of the chlorosilane liquid through the condensing device, and the remaining gas enters the first washing tower for further treatment. The calcium hydroxide solution is used for washing in the first washing tower, which can effectively treat the remaining chlorosilane gas in the mixed tail gas. Next, the remaining silane tail gas after the first washing tower treatment enters the second washing tower, and the sodium hydroxide solution is used for washing to further purify the tail gas, and finally passes through the liquid seal tank to be emptied to ensure safe discharge.

[0028] The reflux pump retransports the alkali washing liquid at the bottom of the washing tower to the upper part of the washing tower for spraying, and at the same time, the waste water in the circulating tank that needs to be discharged is discharged in time, avoiding the blockage of the pipeline by the residual waste residue in the external waste water discharge, and causing damage to the equipment.

[0029] When discharging waste water, the paddle in the circulating tank stops rotating, the reflux pump is opened, and the filter filters and intercepts the solid residue in the waste water at the bottom of the circulating tank to prevent the pipeline from being blocked by the fixed residue. The filter can be disassembled and cleaned, increasing the service life.

[0030] During the whole treatment process, the primary and secondary washing towers work with the corresponding circulating tanks, and the ph meter equipped in the circulating tank monitors the change of the acidity and alkalinity of the washing liquid in real time. Through the feedback control system, according to the deviation of the ph value and the preset standard value, by means of the accurate control function of the remote controller, the water and alkali supplement flow is quickly and accurately adjusted, and the tail gas flow into the washing tower is dynamically controlled. Specifically, the ph value is strictly controlled in the ideal interval of 12-14, when the ph value is lower than 12, the alkali supplement program is automatically started, and the tail gas entering amount is appropriately reduced, so as to ensure the sufficiency and stability of the washing reaction; when the ph value is higher than 14, the alkali supplement is stopped and water is appropriately added into the circulating tank, and the tail gas flow into the washing tower is appropriately increased, so as to maintain the efficient and stable operation of the system.

[0031] The working process of the system is as follows:

[0032] 1. The mixed tail gas of chlorosilane and silane is separated from most of the liquid chlorosilane after the condensing device 1.

[0033] 2. The mixed tail gas (mostly silane and a small amount of chlorosilane) from the condensing device enters the primary washing tower 2, and the calcium hydroxide solution in the primary circulating tank 3 is pumped to the upper part of the washing tower by the primary circulating pump 4 to absorb the remaining chlorosilane gas in the mixed tail gas.

[0034] 3. The remaining tail gas treated by the primary washing tower enters the secondary washing tower 5, and the sodium hydroxide solution in the secondary circulating tank 6 is pumped to the upper part of the washing tower by the secondary circulating pump 7 to absorb the silane gas in the tail gas. Finally, it is vented through the liquid seal tank 8.

[0035] 4. The first filter 9 and the second filter 10 filter and intercept the solid residues in the wastewater at the bottom of the circulating tank to prevent the fixed residues from blocking the pipeline.

[0036] The above embodiments are only preferred technical solutions of the present application, and should not be regarded as limiting the present application. The protection scope of the present application should be based on the technical solutions claimed in the claims, including the equivalent replacement solutions of the technical features in the claimed technical solutions. That is, the equivalent replacement improvements within this range are also within the protection scope of the present application.

Claims

1. A treatment system for a mixture of chlorosilane and silane tail gas, characterized in that: The condensing device (1) is used for cooling the mixed tail gas of silane and chlorosilane, and is connected with the inlet of the first washing tower (2) through a pipeline. The bottom of the first washing tower (2) is connected with the inlet of the first circulating tank (3) through a pipeline, and the bottom of the second washing tower (5) is connected with the inlet of the second circulating tank (6) through a pipeline. The top of the second washing tower (5) is connected with the liquid seal tank (8) through a pipeline.

2. The system for treating a chlorosilane and silane mixed tail gas of claim 1, wherein: The bottom of the first circulating tank (3) is connected with the first filter (9) through a pipeline, the first filter (9) is connected with the first circulating pump (4) through a pipeline, and the first circulating pump (4) is used for pumping the washing liquid to the spray head in the first washing tower (2).

3. The system for treating a chlorosilane and silane mixed tail gas of claim 1, wherein: The bottom of the second circulating tank (6) is connected with the second filter (10) through a pipeline, the second filter (10) is connected with the second circulating pump (7) through a pipeline, and the second circulating pump (7) is used for pumping the washing liquid to the spray head in the second washing tower (5).

4. The system for treating a chlorosilane and silane mixed tail gas of claim 2, wherein: The outlet of the first circulating pump (4) is provided with a first waste pipe.

5. The system for treating a chlorosilane and silane mixed tail gas of claim 3, wherein: The outlet of the second circulating pump (7) is provided with a second waste pipe.

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