Waste heat recovery system of polycrystalline silicon quench tower

Abstract

The utility model discloses a waste heat recovery system of a polycrystalline silicon quench tower, which solves the problems of high load and large energy consumption in the existing waste heat recovery. According to the technical scheme, a quench tower is sequentially connected with shell sides of a quench tower circulating liquid heat exchanger, a low-temperature condensate heat exchanger, a quench tower air cooler and a quench tower water cooler, and liquid phase outlets of the shell sides of the quench tower circulating liquid heat exchanger and the low-temperature condensate heat exchanger are connected with an inlet of a high-temperature condensation tank; shell side liquid phase outlets of the quench tower air cooler and the quench tower water cooler are connected with an inlet of a low-temperature condensate tank. The system is simple, the heat recovery efficiency is high, the energy consumption is reduced, the load of the cooler is effectively reduced, and the equipment investment and the operation cost are low.

Description

Technical Field

[0001] This utility model relates to a waste heat recovery system, specifically a waste heat recovery system for a polycrystalline silicon quench tower. Background Technology

[0002] The polysilicon industry has always been known for its high energy consumption and pollution. The cold hydrogenation unit is the core unit of polysilicon production, converting silicon tetrachloride into trichlorosilane, a raw material for polysilicon production. This not only avoids environmental pollution but also achieves the effective utilization of silicon tetrachloride, a byproduct of polysilicon production.

[0003] Energy recovery from the tail gas after cold hydrogenation has always been an important means of reducing energy consumption in cold hydrogenation units. Currently, the gas phase of the quench tower after conventional thermal coupling (coarse separator coupled with reboiler, hydrogen preheater, and silicon tetrachloride preheater) still has a temperature above 110°C before entering the quench tower air cooler, resulting in high loads on the quench tower air cooler, subsequent quench tower water cooler, intermediate condenser, and other coolers.

[0004] Furthermore, the condensate from the quench tower after each stage of condensation is not properly distributed and accumulates in the feed tank of the coarse separator, causing back mixing of high-temperature and low-temperature condensate. This not only increases the load on the air cooler, water cooler, and intermediate condenser of the quench tower, but also reduces the feed temperature of the coarse separator and increases the consumption of steam, circulating water, and refrigerant in the coarse separator system. Summary of the Invention

[0005] The purpose of this invention is to solve the above-mentioned technical problems and provide a polycrystalline silicon quench tower waste heat recovery system that is simple in system, has high heat recovery efficiency, saves energy and reduces consumption, effectively reduces the load on the cooler, and has low equipment investment and operating costs.

[0006] The technical solution includes a quench tower connected in sequence to the shell side of a quench tower circulating liquid heat exchanger, a low-temperature condensate heat exchanger, a quench tower air cooler, and a quench tower water cooler. The liquid phase outlets of the shell side of the quench tower circulating liquid heat exchanger and the low-temperature condensate heat exchanger are both connected to the inlet of a high-temperature condenser.

[0007] The shell-side outlet of the quench tower air cooler is connected to the quench tower water cooler via a low-temperature condensate tank.

[0008] The liquid phase outlet of the low-temperature condensate tank is connected to the inlet of the high-temperature condensate tank via the tube side of the circulating liquid heat exchanger of the quench tower.

[0009] The tube-side inlet of the low-temperature condensate heat exchanger is connected to the upstream gas-liquid separator, and the tube-side outlet is connected to the feed tank of the coarse separator.

[0010] The liquid phase outlet of the high-temperature condensate tank is connected to the feed tanks of the quench tower and the coarse separator, respectively.

[0011] Beneficial effects:

[0012] This utility model system fully recovers the waste heat of the gas phase of the quench tower and uses it as a heat source to heat the low-temperature condensate. The original quench tower process condensate system is integrated into a high-temperature condensate tank and a low-temperature condensate tank according to temperature. It has the advantages of energy saving and consumption reduction, waste heat recovery, clear system logic, and convenient on-site management. The system process is simple, and all commonly used equipment is used. The equipment investment and operating costs are low, the stability is good, and the reliability is high. Attached Figure Description

[0013] Figure 1 This is a system diagram of the present utility model.

[0014] Among them, 1—quench tower circulating liquid heat exchanger, 2—low temperature condensate heat exchanger, 3—low temperature condensate tank, 4—high temperature condensate tank, 5—quench tower air cooler, 6—quench tower water cooler, 7—quench tower, 8—coarse separation tower feed tank. Detailed Implementation

[0015] The present invention will be further explained below with reference to the accompanying drawings:

[0016] See Figure 1 The quench tower 7 is sequentially connected to the shell side of the quench tower circulating liquid heat exchanger 1, the low-temperature condensate heat exchanger 2, and the quench tower air cooler 5. The shell-side outlet of the quench tower air cooler 5 is connected to the inlet of the low-temperature condensate tank 3. The gas phase outlet of the low-temperature condensate tank 3 is connected to the quench tower water cooler 6. The liquid phase outlets on the shell sides of the quench tower circulating liquid heat exchanger 1 and the low-temperature condensate heat exchanger 2 are both connected to the inlet of the high-temperature condensate tank 4. The liquid phase outlets on the shell sides of the quench tower air cooler 5 and the quench tower water cooler 6 are both connected to the inlet of the low-temperature condensate tank 3. The liquid phase outlet of the low-temperature condensate tank 3 is connected to the inlet of the high-temperature condensate tank 4 via the tube side of the quench tower circulating liquid heat exchanger 1.

[0017] The inlet of the low-temperature condensate heat exchanger 2 is connected to the upstream gas-liquid separator, and the outlet is connected to the feed tank 8 of the coarse separator. The liquid phase outlet of the high-temperature condensate tank 4 is connected to the quench tower 7 and the feed tank 8 of the coarse separator, respectively.

[0018] Process:

[0019] See Figure 1 After undergoing a conventional thermal coupling process, the gas phase (temperature approximately 115±5℃) from the quench tower 7 passes sequentially through the quench tower circulating liquid heat exchanger 1, the low-temperature condensate heat exchanger 2, the quench tower air cooler 5, the low-temperature condensate tank 3, and the quench tower water cooler 6 to be cooled to 40±5℃.

[0020] The process condensate from the quench tower circulating liquid heat exchanger 1 and the low-temperature condensate heat exchanger 2 on the shell side enters the high-temperature condensate tank 4, where the temperature is 110±5℃.

[0021] The condensate from the quench tower air cooler 5 and quench tower water cooler 6 on the shell side enters the low-temperature condensate tank 3, where the temperature is 50±5℃. The liquid phase exiting the low-temperature condensate tank 3 is heated to 100±5℃ after heat exchange in the quench tower circulating liquid heat exchanger 1, and then enters the high-temperature condensate tank 4.

[0022] The low-temperature condensate (temperature approximately -27±2℃) from the outlet of the upstream gas-liquid separator is heated to 100±5℃ after heat exchange in the low-temperature condensate heat exchanger 2 and then sent to the feed tank 8 of the coarse separator. A portion of the liquid phase in the high-temperature condensate tank 4 is pumped back to the quench tower 7 for circulation, while the remainder is sent to the feed tank 8 of the coarse separator. Since the liquid phase entering the feed tank 8 of the coarse separator is all high-temperature liquid phase, the feed temperature of the coarse separator can be increased to 115±2℃.

[0023] The aforementioned quench tower waste heat recovery system can fully recover the waste heat from the quench tower and use it as a heat source to heat the low-temperature condensate. The original condensate system is integrated according to temperature into a high-temperature condensate tank 4 and a low-temperature condensate tank 3. This not only reduces the load on the quench tower air cooler and water cooler but also increases the feed temperature to the coarse separator, thus reducing the energy consumption of the coarse separator. The entire system has significant energy-saving and consumption-reducing effects, lowers production costs, and facilitates on-site operation and management.

Claims

1. A waste heat recovery system for a polycrystalline silicon quench tower, characterized in that, The system includes a quench tower connected in sequence to the shell side of a quench tower circulating liquid heat exchanger, a low-temperature condensate heat exchanger, a quench tower air cooler, and a quench tower water cooler. The liquid phase outlets on the shell side of the quench tower circulating liquid heat exchanger and the low-temperature condensate heat exchanger are both connected to the inlet of a high-temperature condenser. The liquid phase outlets on the shell side of the quench tower air cooler and the quench tower water cooler are both connected to the inlet of a low-temperature condensate tank.

2. The waste heat recovery system for a polycrystalline silicon quench tower as described in claim 1, characterized in that, The shell-side outlet of the quench tower air cooler is connected to the quench tower water cooler via a low-temperature condensate tank.

3. The waste heat recovery system for a polycrystalline silicon quench tower as described in claim 1 or 2, characterized in that, The liquid phase outlet of the low-temperature condensate tank is connected to the inlet of the high-temperature condensate tank via the tube side of the circulating liquid heat exchanger of the quench tower.

4. The waste heat recovery system for a polycrystalline silicon quench tower as described in claim 1, characterized in that... The tube-side inlet of the low-temperature condensate heat exchanger is connected to the upstream gas-liquid separator, and the tube-side outlet is connected to the feed tank of the coarse separator.

5. The waste heat recovery system for a polycrystalline silicon quench tower as described in claim 1 or 2, characterized in that... The liquid phase outlet of the high-temperature condenser is connected to the feed tanks of the quench tower and the coarse separator, respectively.

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