Hydrogen chloride synthesis furnace circulating water cascade heat exchange system

Abstract

The utility model discloses hydrogen chloride synthetic furnace circulating water cascade heat exchange system, including a plurality of cooling towers, a plurality of cooling towers upper end through circulating water system backwater main pipe respectively with hydrogen chloride synthetic furnace circulating water cooler, first stage hydrochloric acid falling film absorber, second stage hydrochloric acid falling film absorber intercommunication, cooling tower bottom and cold water tower pool intercommunication, and cold water tower pool is connected with hydrogen chloride synthetic furnace circulating water cooler, first stage hydrochloric acid falling film absorber, second stage hydrochloric acid falling film absorber intercommunication respectively. Hydrogen chloride synthetic furnace circulating water cascade heat exchange system, through the new hydrochloric acid falling film absorber and hydrogen chloride synthetic furnace circulating water cooler series pipeline and relevant valve, can realize hydrochloric acid falling film absorber and hydrogen chloride synthetic furnace circulating water cooler series operation when daily system operation, greatly reduces circulating water system circulation amount, reaches the purpose that the circulating water pump energy -conserving.

Description

Technical Field

[0001] This utility model belongs to the field of circulating water heat exchange technology, and relates to a circulating water cascade heat exchange system for a hydrogen chloride synthesis furnace. Background Technology

[0002] In the circulating water system of a chlor-alkali plant, the circulating water from the hydrogen chloride synthesis furnace and the hydrochloric acid falling film absorber are the main water points, characterized by large circulation volumes and small temperature differences, resulting in high energy consumption of the circulating water pumps. Industry technicians often try to reduce the flow rate of the circulating water at these two critical points to save energy. However, reducing the flow rate of the synthesis furnace circulating water can easily lead to higher furnace top temperatures and higher outlet temperatures for the hydrogen chloride product gas. While the hydrochloric acid falling film absorber has a small daily heat load, in the event of a sudden production emergency requiring large-scale acid production, insufficient water supply in a short period can cause a rapid increase in the temperature of the absorbent liquid, thereby reducing the solubility of hydrogen chloride gas in the absorbent liquid, resulting in a decrease in hydrochloric acid absorption rate, excessive residual hydrogen chloride concentration in the tail gas, localized overheating of the graphite tubes, and potentially leading to aging and failure of seals, or even pipe deformation and rupture. Therefore, the conventional control method is to control the flow rate at a high level.

[0003] In summary, existing technologies suffer from problems such as large circulating water volume and low utilization rate in conventional chlor-alkali circulating water systems. Utility Model Content

[0004] The purpose of this invention is to provide a cascade heat exchange system for circulating water in a hydrogen chloride synthesis furnace, which solves the problems of large circulating water volume and low utilization rate in conventional chlor-alkali circulating water systems in the prior art.

[0005] The technical solution adopted in this utility model is a cascade heat exchange system for circulating water in a hydrogen chloride synthesis furnace, comprising several cooling towers. The upper ends of the cooling towers are connected to the circulating water cooler, the primary hydrochloric acid falling film absorber, and the secondary hydrochloric acid falling film absorber respectively through the return water header of the circulating water system. The bottom of the cooling towers is connected to a cooling water tank, which is also connected to the circulating water cooler, the primary hydrochloric acid falling film absorber, and the secondary hydrochloric acid falling film absorber.

[0006] The features of this utility model also include: The cooling water tank is located at the bottom of the cooling tower. The bottom of the cooling water tank is connected to the inlet of several circulating water pumps. The outlet of several circulating water pumps is connected to the cold side outlet of the circulating water cooler of the hydrogen chloride synthesis furnace, the cold side outlet of the first-stage hydrochloric acid falling film absorber, and the cold side outlet of the second-stage hydrochloric acid falling film absorber. A remote pressure gauge for the circulating water supply main pipe is installed on the pipe at the outlet of the circulating water pump.

[0007] A synthesis furnace circulating water inlet valve is installed on the pipeline between the cold side inlet of the hydrogen chloride synthesis furnace circulating water cooler and the circulating water pump.

[0008] The cold-side outlet of the circulating water cooler of the hydrogen chloride synthesis furnace is connected to the return water header of the circulating water system, and a synthesis furnace circulating water outlet valve is installed on the pipeline between the cold-side outlet of the circulating water cooler of the hydrogen chloride synthesis furnace and the return water header of the circulating water system.

[0009] A circulating water inlet valve for the primary hydrochloric acid falling film absorber is installed on the pipeline between the cold side inlet of the primary hydrochloric acid falling film absorber and the circulating water pump.

[0010] The cold-side outlet of the primary hydrochloric acid falling film absorber is connected to the return water header of the circulating water system. A circulating water outlet valve for the primary hydrochloric acid falling film absorber is installed on the pipeline between the cold-side outlet of the primary hydrochloric acid falling film absorber and the return water header of the circulating water system.

[0011] A circulating water inlet valve for the secondary hydrochloric acid falling film absorber is installed on the pipeline between the cold side inlet of the secondary hydrochloric acid falling film absorber and the circulating water pump.

[0012] The cold-side outlet of the secondary hydrochloric acid falling film absorber is connected to the return water header of the circulating water system. A circulating water outlet valve for the secondary hydrochloric acid falling film absorber is installed on the pipeline between the cold-side outlet of the secondary hydrochloric acid falling film absorber and the return water header of the circulating water system.

[0013] The circulating water outlet valve of the first-stage hydrochloric acid falling film absorber, the circulating water outlet valve of the second-stage hydrochloric acid falling film absorber, and the return water main pipe of the circulating water system are connected to the circulating water outlet valve of the hydrochloric acid falling film absorber.

[0014] The circulating water outlet valve of the first-stage hydrochloric acid falling film absorber is located at the end furthest from the first-stage hydrochloric acid falling film absorber, and the circulating water outlet valve of the second-stage hydrochloric acid falling film absorber is located at the end furthest from the second-stage hydrochloric acid falling film absorber. A series inlet valve for the circulating water of the hydrogen chloride synthesis furnace is installed on the pipeline between the cold-side inlet of the hydrogen chloride synthesis furnace circulating water cooler and the circulating water outlet valves of the first-stage and second-stage hydrochloric acid falling film absorbers.

[0015] The beneficial effects of this utility model are as follows: By adding a series pipeline and related valves for the hydrochloric acid falling film absorber and the hydrogen chloride synthesis furnace circulating water cooler, the hydrochloric acid falling film absorber and the hydrogen chloride synthesis furnace circulating water cooler can be operated in series during daily system operation, which greatly reduces the circulation volume of the circulating water system and achieves the purpose of energy saving of the circulating water pump; when the hydrochloric acid falling film absorber needs to produce a large amount of acid, or when the temperature of the furnace top rises and exceeds the alarm value, the hydrochloric acid falling film absorber and the circulating water of the synthesis furnace can be automatically switched from the daily series mode to the parallel mode to ensure production safety; the circulating water pump is set to start automatically. When the circulation volume of the circulating water system in the parallel mode increases and the pressure value of the remote pressure gauge of the circulating water supply main pipe drops to the warning value, an additional circulating water pump can be automatically started to meet the water supply pressure demand. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the circulating water cascade heat exchange system for the hydrogen chloride synthesis furnace of this utility model; Figure 2 This is a flowchart illustrating the usage of the circulating water cascade heat exchange system for the hydrogen chloride synthesis furnace of this utility model.

[0017] In the diagram: 1. Hydrogen chloride synthesis furnace circulating water cooler; 2. Synthesis furnace circulating water inlet valve; 3. Synthesis furnace circulating water outlet valve; 4. Synthesis furnace circulating water inlet valve; 5. Primary hydrochloric acid falling film absorber; 6. Secondary hydrochloric acid falling film absorber; 7. Primary hydrochloric acid falling film absorber circulating water inlet valve; 8. Primary hydrochloric acid falling film absorber circulating water outlet valve; 9. Secondary hydrochloric acid falling film absorber circulating water inlet valve; 10. Secondary hydrochloric acid falling film absorber circulating water outlet valve; 11. Hydrochloric acid falling film absorber circulating water main outlet valve; 12. Cooling tower; 13. Cold water tower pool; 14. Circulating water pump; 15. Circulating water supply header remote pressure gauge. Detailed Implementation

[0018] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0019] The circulating water cascade heat exchange system for the hydrogen chloride synthesis furnace includes several cooling towers 12. The upper ends of the cooling towers 12 are connected to the circulating water cooler 1, the primary hydrochloric acid falling film absorber 5, and the secondary hydrochloric acid falling film absorber 6 of the hydrogen chloride synthesis furnace through the return water header of the circulating water system. The bottom of the cooling towers 12 is connected to the cooling water tank 13, which is also connected to the circulating water cooler 1, the primary hydrochloric acid falling film absorber 5, and the secondary hydrochloric acid falling film absorber 6 of the hydrogen chloride synthesis furnace.

[0020] The cooling water tank 13 is located at the bottom of the cooling tower 12. The bottom of the cooling water tank 13 is connected to the inlet of several circulating water pumps 14. The outlet of several circulating water pumps 14 is connected to the cold side outlet of the circulating water cooler 1 of the hydrogen chloride synthesis furnace, the cold side outlet of the first-stage hydrochloric acid falling film absorber 5, and the cold side outlet of the second-stage hydrochloric acid falling film absorber 6. A remote pressure gauge 15 for the circulating water supply main pipe is installed on the pipe at the outlet of the circulating water pumps 14.

[0021] A circulating water valve 2 for the hydrogen chloride synthesis furnace is installed on the pipeline between the cold side inlet of the circulating water cooler 1 and the circulating water pump 14. The cold side outlet of the circulating water cooler 1 is connected to the return water header of the circulating water system, and a circulating water outlet valve 3 for the synthesis furnace is installed on the pipeline between the cold side outlet of the circulating water cooler 1 and the return water header of the circulating water system.

[0022] A circulating water inlet valve 7 is installed on the pipeline between the cold-side inlet of the primary hydrochloric acid falling film absorber 5 and the circulating water pump 14. The cold-side outlet of the primary hydrochloric acid falling film absorber 5 is connected to the return water header of the circulating water system, and a circulating water outlet valve 8 is installed on the pipeline between the cold-side outlet of the primary hydrochloric acid falling film absorber 5 and the return water header of the circulating water system.

[0023] A secondary hydrochloric acid falling film absorber 6 is installed on the pipeline between its cold-side inlet and the circulating water pump 14. The cold-side outlet of the secondary hydrochloric acid falling film absorber 6 is connected to the return water header of the circulating water system, and a secondary hydrochloric acid falling film absorber circulating water outlet valve 10 is installed on the pipeline between the cold-side outlet of the secondary hydrochloric acid falling film absorber 6 and the return water header of the circulating water system.

[0024] A circulating water outlet valve 11 for hydrochloric acid falling film absorbers is installed on the pipeline between the circulating water outlet valve 8 of the primary hydrochloric acid falling film absorber, the circulating water outlet valve 10 of the secondary hydrochloric acid falling film absorber, and the return water main pipe of the circulating water system. The end of the circulating water outlet valve 8 of the primary hydrochloric acid falling film absorber away from the primary hydrochloric acid falling film absorber 5 and the end of the circulating water outlet valve 10 of the secondary hydrochloric acid falling film absorber away from the secondary hydrochloric acid falling film absorber 6 are connected to the cold side inlet of the circulating water cooler 1 of the hydrogen chloride synthesis furnace. A series inlet valve 4 for the circulating water of the synthesis furnace is installed on the pipeline between the cold side inlet of the circulating water cooler 1 of the hydrogen chloride synthesis furnace and the circulating water outlet valves 8 and 10 of the primary hydrochloric acid falling film absorber.

[0025] This invention solves the problems of excessive circulating water volume, low water utilization rate, and high energy consumption of circulating water pumps in chlor-alkali circulating water systems; it maximizes the on-demand water supply to heat exchangers, avoids the risk of overheating caused by untimely water supply to the synthesis furnace and hydrochloric acid falling film absorber in case of sudden production situations, and effectively ensures production safety.

[0026] This invention reduces the amount of circulating water and lowers the energy consumption of the circulating water pump: Under normal operating conditions, the hydrochloric acid falling film absorber has a low heat load and a low temperature difference in the circulating water. By adding a series pipeline (including the inlet valve 4 for the circulating water of the synthesis furnace), the circulating water first undergoes preliminary heat exchange in the falling film absorber and then enters the hydrogen chloride synthesis furnace circulating water cooler 1 for secondary heat exchange, which greatly reduces the total circulation volume of the system and avoids the circulating water pump 14 from operating at full load for a long time.

[0027] The corresponding valve operations are as follows: Synthetic furnace circulating water outlet valve 3, synthetic furnace circulating water series inlet valve 4, primary hydrochloric acid falling film absorber circulating water inlet valve 7, secondary hydrochloric acid falling film absorber circulating water inlet valve 9, primary hydrochloric acid falling film absorber circulating water outlet valve 8, and secondary hydrochloric acid falling film absorber circulating water outlet valve 10 are open; Synthetic furnace circulating water parallel inlet valve 2 and hydrochloric acid falling film absorber circulating water parallel outlet main valve 11 are closed.

[0028] Circulating water path: Cooling water tower pool 13 → Circulating water pump 14 → Primary hydrochloric acid falling film absorber 5 / Secondary hydrochloric acid falling film absorber 6 → Synthesis furnace circulating water series inlet valve 4 → Hydrogen chloride synthesis furnace circulating water cooler 1 → Synthesis furnace circulating water outlet valve 3 → Circulating water system return water header → Cooling tower 12 → Cooling water tower pool 13.

[0029] The circulating water only needs to be transported once to complete the "preliminary heat exchange of the falling film absorber + deep heat exchange of the synthesis furnace cooler". The total circulation volume of the system is reduced compared with the conventional parallel mode. The circulating water pump 14 does not need to maintain a large flow output, and the energy consumption is significantly reduced.

[0030] This utility model addresses unexpected situations and avoids overheating and equipment risks: In case of emergencies, such as when production requires a large amount of acid production (the heat load of the hydrochloric acid falling film absorber suddenly increases) or the temperature of the top of the synthesis furnace exceeds the alarm value (the hydrogen chloride synthesis furnace needs enhanced cooling), the system can quickly switch to parallel mode to ensure that both key pieces of equipment receive sufficient circulating water, thus avoiding safety issues such as overheating of the absorbent, decreased absorption rate, and overheating of the graphite tubes.

[0031] Triggering conditions: The hydrochloric acid falling film absorber (5 / 6) needs to produce a large amount of acid urgently (sudden increase in heat load); the top temperature of the hydrogen chloride synthesis furnace exceeds the alarm value (requires enhanced cooling).

[0032] Valve switching operation: Open the following valves: Synthesis furnace circulating water inlet valve 2, synthesis furnace circulating water outlet valve 3, hydrochloric acid falling film absorber circulating water outlet valve 11, primary hydrochloric acid falling film absorber circulating water inlet valve 7, secondary hydrochloric acid falling film absorber circulating water inlet valve 9, primary hydrochloric acid falling film absorber circulating water outlet valve 8, and secondary hydrochloric acid falling film absorber circulating water outlet valve 10; Close the following valves: Synthesis furnace circulating water inlet valve 4.

[0033] Circulating water path (parallel branching): Cooling tower tank 13 → Circulating water pump 14 → Two branching paths: Branch 1: Synthesis furnace circulating water connected to inlet valve 2 → hydrogen chloride synthesis furnace circulating water cooler 1 → synthesis furnace circulating water outlet valve 3 → return water header → cooling tower 12; Branch 2: Primary hydrochloric acid falling film absorber 5 / Secondary hydrochloric acid falling film absorber 6 → Hydrochloric acid falling film absorber circulating water connected to outlet main valve 11 → Return water header → Cooling tower 12.

[0034] Safety assurance effect: The hydrochloric acid falling film absorber obtains sufficient circulating water, and the absorbent temperature is stable, avoiding the decrease in hydrogen chloride solubility and the excessive tail gas; the hydrogen chloride synthesis furnace circulating water cooler 1 obtains independent high-flow water supply, and the furnace top temperature drops rapidly, avoiding the product gas outlet temperature from exceeding the limit.

[0035] This invention automatically adjusts the water supply pressure to ensure stable system operation. In parallel mode, the system circulation volume increases sharply, which can easily lead to a drop in water supply pressure; after the series mode is restored, the circulation volume decreases and the pressure rises. Through the interlocking control of the pressure gauge 15 and the circulating water pump 14 via the remote transmission of the circulating water supply main pipe, automatic pressure regulation is achieved to avoid the impact of pressure fluctuations on the heat exchange effect of the equipment.

[0036] 1. Pressure replenishment in parallel mode (increased circulation volume, decreased pressure) Pressure detection: The remote pressure gauge 15 of the circulating water supply main pipe monitors the water supply pressure in real time. When the system is switched to parallel mode, the system flow increases and the pressure drops to the set warning value. Water pump linkage: If it is "water pump auto-start" control: when the pressure is lower than the warning value, circulating water pump 14 will automatically start one more to increase the water supply flow and maintain stable pressure; If it is "variable frequency control": when the pressure is lower than the warning value, the circulating water pump 14, i.e., the variable frequency pump, will automatically increase the frequency and increase the output flow to ensure that the water supply pressure meets the standard.

[0037] 2. In series mode, pressure is reduced (circulation volume decreases, pressure increases). Recovery trigger: When production returns to normal (no need for large-scale acid production, furnace top temperature drops), the system switches back to series mode; Pump regulation: When the pressure gauge 15 of the circulating water supply main pipe detects that the pressure has risen back to the normal range, it automatically stops one circulating water pump 14 (or the frequency converter pump reduces the frequency) to avoid energy waste and maintain system pressure balance.

[0038] Example 1 This embodiment proposes a cascade heat exchange system for circulating water in a hydrogen chloride synthesis furnace, including a cooling tower 12. The upper end of the cooling tower 12 is connected to the circulating water cooler 1, the primary hydrochloric acid falling film absorber 5, and the secondary hydrochloric acid falling film absorber 6 via the return water header of the circulating water system. The bottom of the cooling tower 12 is connected to a cooling water tank 13, which is also connected to the circulating water cooler 1, the primary hydrochloric acid falling film absorber 5, and the secondary hydrochloric acid falling film absorber 6.

[0039] Example 2 This embodiment proposes a cascade heat exchange system for circulating water in a hydrogen chloride synthesis furnace, including two cooling towers 12. The upper ends of the two cooling towers 12 are connected to the circulating water cooler 1, the primary hydrochloric acid falling film absorber 5, and the secondary hydrochloric acid falling film absorber 6 respectively via a return water header of the circulating water system. The bottom of the cooling towers 12 is connected to a cooling water tank 13, which is also connected to the circulating water cooler 1, the primary hydrochloric acid falling film absorber 5, and the secondary hydrochloric acid falling film absorber 6. The cooling water tank 13 is located at the bottom of the cooling towers 12, and its bottom is connected to the inlet of two circulating water pumps 14. The outlets of the two circulating water pumps 14 are connected to the cold side outlet of the circulating water cooler 1, the cold side outlet of the primary hydrochloric acid falling film absorber 5, and the cold side outlet of the secondary hydrochloric acid falling film absorber 6 respectively. A remote pressure gauge 15 for the circulating water supply header is installed on the pipe at the outlet of the circulating water pumps 14.

[0040] Example 3 This embodiment proposes a cascade heat exchange system for circulating water in a hydrogen chloride synthesis furnace, including three cooling towers 12. The upper ends of the three cooling towers 12 are connected to the circulating water cooler 1, the primary hydrochloric acid falling film absorber 5, and the secondary hydrochloric acid falling film absorber 6 respectively through the return water header of the circulating water system. The bottom of the cooling towers 12 is connected to a cooling water tank 13, which is also connected to the circulating water cooler 1, the primary hydrochloric acid falling film absorber 5, and the secondary hydrochloric acid falling film absorber 6 respectively.

[0041] A cooling water tank 13 is located at the bottom of the cooling tower 12. The bottom of the cooling water tank 13 is connected to the inlet of three circulating water pumps 14. The outlets of the three circulating water pumps 14 are connected to the cold side outlet of the hydrogen chloride synthesis furnace circulating water cooler 1, the cold side outlet of the first-stage hydrochloric acid falling film absorber 5, and the cold side outlet of the second-stage hydrochloric acid falling film absorber 6, respectively. A remote pressure gauge 15 for the circulating water supply header is installed on the pipe at the outlet of the circulating water pumps 14. A synthesis furnace circulating water inlet valve 2 is installed on the pipe between the cold side inlet of the hydrogen chloride synthesis furnace circulating water cooler 1 and the circulating water pumps 14. The cold side outlet of the hydrogen chloride synthesis furnace circulating water cooler 1 is connected to the circulating water system return header, and a synthesis furnace circulating water outlet valve 3 is installed on the pipe between the cold side outlet of the hydrogen chloride synthesis furnace circulating water cooler 1 and the circulating water system return header.

[0042] Example 4 This embodiment proposes a cascade heat exchange system for circulating water in a hydrogen chloride synthesis furnace, comprising four cooling towers 12. The upper ends of the four cooling towers 12 are connected to the circulating water cooler 1, the primary hydrochloric acid falling film absorber 5, and the secondary hydrochloric acid falling film absorber 6 respectively via a return water header of the circulating water system. The bottom of the cooling towers 12 is connected to a cooling water tank 13, which is also connected to the circulating water cooler 1, the primary hydrochloric acid falling film absorber 5, and the secondary hydrochloric acid falling film absorber 6. The cooling water tank 13 is located at the bottom of the cooling towers 12, and its bottom is connected to the inlet of four circulating water pumps 14. The outlets of the four circulating water pumps 14 are connected to the cold side outlet of the circulating water cooler 1, the cold side outlet of the primary hydrochloric acid falling film absorber 5, and the cold side outlet of the secondary hydrochloric acid falling film absorber 6 respectively. A remote pressure gauge 15 for the circulating water supply header is installed on the pipe at the outlet of the circulating water pumps 14.

[0043] A circulating water valve 2 for the hydrogen chloride synthesis furnace is installed on the pipeline between the cold side inlet of the circulating water cooler 1 and the circulating water pump 14. The cold side outlet of the circulating water cooler 1 is connected to the return water header of the circulating water system, and a circulating water outlet valve 3 for the synthesis furnace is installed on the pipeline between the cold side outlet of the circulating water cooler 1 and the return water header of the circulating water system.

[0044] A circulating water inlet valve 7 is installed on the pipeline between the cold-side inlet of the primary hydrochloric acid falling film absorber 5 and the circulating water pump 14. The cold-side outlet of the primary hydrochloric acid falling film absorber 5 is connected to the return water header of the circulating water system, and a circulating water outlet valve 8 is installed on the pipeline between the cold-side outlet of the primary hydrochloric acid falling film absorber 5 and the return water header of the circulating water system.

[0045] Example 5 This embodiment proposes a cascade heat exchange system for circulating water in a hydrogen chloride synthesis furnace, comprising five cooling towers 12. The upper ends of the five cooling towers 12 are connected to the circulating water cooler 1, the primary hydrochloric acid falling film absorber 5, and the secondary hydrochloric acid falling film absorber 6 respectively via a return water header of the circulating water system. The bottom of the cooling towers 12 is connected to a cooling water tank 13, which is also connected to the circulating water cooler 1, the primary hydrochloric acid falling film absorber 5, and the secondary hydrochloric acid falling film absorber 6. The cooling water tank 13 is located at the bottom of the cooling towers 12, and its bottom is connected to the inlet of five circulating water pumps 14. The outlets of the five circulating water pumps 14 are connected to the cold side outlet of the circulating water cooler 1, the cold side outlet of the primary hydrochloric acid falling film absorber 5, and the cold side outlet of the secondary hydrochloric acid falling film absorber 6 respectively. A remote pressure gauge 15 for the circulating water supply header is installed on the pipe at the outlet of the circulating water pumps 14.

[0046] A circulating water valve 2 for the hydrogen chloride synthesis furnace is installed on the pipeline between the cold side inlet of the circulating water cooler 1 and the circulating water pump 14. The cold side outlet of the circulating water cooler 1 is connected to the return water header of the circulating water system, and a circulating water outlet valve 3 for the synthesis furnace is installed on the pipeline between the cold side outlet of the circulating water cooler 1 and the return water header of the circulating water system.

[0047] A circulating water inlet valve 7 is installed on the pipeline between the cold-side inlet of the primary hydrochloric acid falling film absorber 5 and the circulating water pump 14. The cold-side outlet of the primary hydrochloric acid falling film absorber 5 is connected to the return water header of the circulating water system, and a circulating water outlet valve 8 is installed on the pipeline between the cold-side outlet of the primary hydrochloric acid falling film absorber 5 and the return water header of the circulating water system.

[0048] A secondary hydrochloric acid falling film absorber 6 is installed on the pipeline between its cold-side inlet and the circulating water pump 14. The cold-side outlet of the secondary hydrochloric acid falling film absorber 6 is connected to the return water header of the circulating water system, and a secondary hydrochloric acid falling film absorber circulating water outlet valve 10 is installed on the pipeline between the cold-side outlet of the secondary hydrochloric acid falling film absorber 6 and the return water header of the circulating water system.

[0049] Example 6 This embodiment proposes a cascade heat exchange system for circulating water in a hydrogen chloride synthesis furnace, comprising six cooling towers 12. The upper ends of the six cooling towers 12 are connected to the circulating water cooler 1, the primary hydrochloric acid falling film absorber 5, and the secondary hydrochloric acid falling film absorber 6 respectively via a return water header of the circulating water system. The bottom of the cooling towers 12 is connected to a cooling water tank 13, which is also connected to the circulating water cooler 1, the primary hydrochloric acid falling film absorber 5, and the secondary hydrochloric acid falling film absorber 6. The cooling water tank 13 is located at the bottom of the cooling towers 12, and its bottom is connected to the inlet of each of the six circulating water pumps 14. The outlets of the six circulating water pumps 14 are connected to the cold side outlet of the circulating water cooler 1, the cold side outlet of the primary hydrochloric acid falling film absorber 5, and the cold side outlet of the secondary hydrochloric acid falling film absorber 6 respectively. A remote pressure gauge 15 for the circulating water supply header is installed on the pipe at the outlet of the circulating water pumps 14.

[0050] A circulating water inlet valve 2 is installed on the pipeline between the cold-side inlet of the hydrogen chloride synthesis furnace circulating water cooler 1 and the circulating water pump 14. The cold-side outlet of the hydrogen chloride synthesis furnace circulating water cooler 1 is connected to the return water header of the circulating water system, and a circulating water outlet valve 3 is installed on the pipeline between the cold-side outlet of the hydrogen chloride synthesis furnace circulating water cooler 1 and the return water header of the circulating water system. A primary hydrochloric acid falling film absorber circulating water inlet valve 7 is installed on the pipeline between the cold-side inlet of the primary hydrochloric acid falling film absorber 5 and the circulating water pump 14. The cold-side outlet of the primary hydrochloric acid falling film absorber 5 is connected to the return water header of the circulating water system, and a primary hydrochloric acid falling film absorber circulating water outlet valve 8 is installed on the pipeline between the cold-side outlet of the primary hydrochloric acid falling film absorber 5 and the return water header of the circulating water system. A secondary hydrochloric acid falling film absorber circulating water inlet valve 9 is installed on the pipeline between the cold-side inlet of the secondary hydrochloric acid falling film absorber 6 and the circulating water pump 14. The cold side outlet of the secondary hydrochloric acid falling film absorber 6 is connected to the return water main pipe of the circulating water system, and the circulating water outlet valve 10 of the secondary hydrochloric acid falling film absorber is installed on the pipeline between the cold side outlet of the secondary hydrochloric acid falling film absorber 6 and the return water main pipe of the circulating water system.

[0051] A circulating water outlet valve 11 for hydrochloric acid falling film absorbers is installed on the pipeline between the circulating water outlet valve 8 of the primary hydrochloric acid falling film absorber, the circulating water outlet valve 10 of the secondary hydrochloric acid falling film absorber, and the return water main pipe of the circulating water system. The end of the circulating water outlet valve 8 of the primary hydrochloric acid falling film absorber away from the primary hydrochloric acid falling film absorber 5 and the end of the circulating water outlet valve 10 of the secondary hydrochloric acid falling film absorber away from the secondary hydrochloric acid falling film absorber 6 are connected to the cold side inlet of the circulating water cooler 1 of the hydrogen chloride synthesis furnace. A series inlet valve 4 for the circulating water of the synthesis furnace is installed on the pipeline between the cold side inlet of the circulating water cooler 1 of the hydrogen chloride synthesis furnace and the circulating water outlet valves 8 and 10 of the primary hydrochloric acid falling film absorber.

[0052] like Figure 1 As shown, this utility model includes a cooling tower 12, with a cold water tank 13 at the bottom of the cooling tower 12. The bottom of the cold water tank 13 is connected to the inlet of a circulating water pump 14. The main outlet pipe of the circulating water pump 14 is connected to the cold side inlets of the hydrogen chloride synthesis furnace circulating water cooler 1, the first-stage hydrochloric acid falling film absorber 5, and the second-stage hydrochloric acid falling film absorber 6. The cold side inlets of the hydrogen chloride synthesis furnace circulating water cooler 1, the first-stage hydrochloric acid falling film absorber 5, and the second-stage hydrochloric acid falling film absorber 6 are respectively equipped with a synthesis furnace circulating water inlet valve 2, a first-stage hydrochloric acid falling film absorber circulating water inlet valve 7, and a second-stage hydrochloric acid falling film absorber circulating water inlet valve 9. The cold side outlets of the hydrogen chloride synthesis furnace circulating water cooler 1, the first-stage hydrochloric acid falling film absorber 5, and the second-stage hydrochloric acid falling film absorber 6 are respectively equipped with a synthesis furnace circulating water outlet valve 3, a first-stage hydrochloric acid falling film absorber circulating water outlet valve 8, and a second-stage hydrochloric acid falling film absorber circulating water outlet valve 10, and are respectively connected to the return water header of the circulating water system. The main outlet pipe of the hydrochloric acid falling film absorber is connected to the cold side inlet of the circulating water cooler 1 of the hydrogen chloride synthesis furnace, and a series inlet valve 4 for the synthesis furnace circulating water is installed on the connecting pipe. The main outlet pipe of the hydrochloric acid falling film absorber is connected to the return water header of the circulating water system, and a main outlet valve 11 for the hydrochloric acid falling film absorber circulating water is installed on the connecting pipe. The return water header of the circulating water system is then connected to the cooling tower 12. A remote pressure gauge 15 for the circulating water supply header is installed on the main outlet pipe of the circulating water pump 14.

[0053] The specific working principle of the circulating water cascade heat exchange system for the hydrogen chloride synthesis furnace of this utility model is as follows: In the circulating water system of the chlor-alkali plant, the circulating water pump 14 transports the circulating water from the cooling tower pool 13 to the system water supply header. In normal processes, the circulating water cooler 1 of the hydrogen chloride synthesis furnace, the primary hydrochloric acid falling film absorber 5, and the secondary hydrochloric acid falling film absorber 6 are connected in parallel and the circulating water is transported to various water points through the circulating water header. Among them, the circulating water in the circulating water cooler 1 of the hydrogen chloride synthesis furnace, as well as the primary hydrochloric acid falling film absorber 5 and the secondary hydrochloric acid falling film absorber 6, all need to maintain a large flow rate to ensure production safety. Moreover, the hydrochloric acid falling film absorber has a very small heat load under normal operating conditions, the temperature difference on the circulating water side is very low, and the water utilization rate is low.

[0054] Combination Figure 2 As shown, the method of using the circulating water cascade heat exchange system for the hydrogen chloride synthesis furnace of this utility model is as follows: Step 1: A small portion of HCl gas produced by the hydrogen chloride synthesis furnace is absorbed by water through the primary hydrochloric acid falling film absorber 5 and the secondary hydrochloric acid falling film absorber 6 to generate hydrochloric acid. The tail gas is pumped into the acid circulation tank by a hydraulic jet pump and vented. In this production process, the circulating water plays an auxiliary role in cooling. The circulating water in the cooling tower pool 13 is pressurized by the circulating water pump 14 and then sent to the primary hydrochloric acid falling film absorber 5 and the secondary hydrochloric acid falling film absorber 6 to remove the heat of reaction. Step 2: Under normal operating conditions, the circulating water passes through the primary hydrochloric acid falling film absorber 5 and the secondary hydrochloric acid falling film absorber 6 in series before entering the hydrogen chloride synthesis furnace circulating water cooler 1. After heat exchange, it is transported to the upper part of the cooling tower 12 via the circulating water system return header. After being cooled and dissipated by the cooling tower 12, it returns to the cooling water tank 13. At this time, the synthesis furnace circulating water outlet valve 3, the synthesis furnace circulating water series inlet valve 4, the primary hydrochloric acid falling film absorber circulating water inlet valve 7, the secondary hydrochloric acid falling film absorber circulating water inlet valve 9, the primary hydrochloric acid falling film absorber circulating water outlet valve 8, and the secondary hydrochloric acid falling film absorber circulating water outlet valve 10 are in the open state, while the synthesis furnace circulating water parallel inlet valve 2 and the hydrochloric acid falling film absorber circulating water parallel outlet main valve 11 are in the closed state.

[0055] Step 3: When production requires a large amount of acid to be produced by the hydrochloric acid falling film absorber, or when the temperature at the top of the synthesis furnace rises and exceeds the alarm value, the hydrochloric acid falling film absorber and the synthesis furnace circulating water automatically switch from the usual series mode to the parallel mode. The hydrochloric acid falling film absorber and the hydrogen chloride synthesis furnace circulating water cooler 1 operate in parallel on the circulating water side. At this time, the following valves are in the open state: synthesis furnace circulating water inlet valve 2, synthesis furnace circulating water outlet valve 3, hydrochloric acid falling film absorber circulating water outlet valve 11, primary hydrochloric acid falling film absorber circulating water inlet valve 7, secondary hydrochloric acid falling film absorber circulating water inlet valve 9, primary hydrochloric acid falling film absorber circulating water outlet valve 8, and secondary hydrochloric acid falling film absorber circulating water outlet valve 10. The synthesis furnace circulating water series inlet valve 4 is in the closed state.

[0056] Step 4: After switching to "parallel mode", the pressure gauge 15 of the circulating water supply main pipe shows a decrease in pressure, the water pump starts automatically, and an additional circulating water pump 14 is automatically added to ensure stable water supply pressure in the system.

[0057] Step 5: When production returns to normal and large-scale acid production is no longer required, switch back from "parallel mode" to "series mode". Step 6: After switching to "series mode", the system water supply pressure increases, one circulating water pump stops, and the system returns to normal operation.

[0058] This utility model of a circulating water cascade heat exchange system for a hydrogen chloride synthesis furnace can solve the problems of low daily heat load of the hydrochloric acid falling film absorber, low utilization rate of circulating water volume, and high energy consumption of circulating water pump. It can also avoid the risk of overheating of the synthesis furnace and hydrochloric acid falling film absorber in case of sudden production situations, effectively ensuring production safety.

[0059] In the circulating water cascade heat exchange system of the hydrogen chloride synthesis furnace of this utility model, the number of synthesis furnaces can be multiple, the number of hydrochloric acid falling film absorbers can be multiple sets, the circulating water supply between multiple synthesis furnaces can be in parallel, and the circulating water supply between multiple hydrochloric acid falling film absorbers can be in parallel.

[0060] In this utility model, the automatic start of the water pump in the circulating water cascade heat exchange system of the hydrogen chloride synthesis furnace can be replaced with variable frequency control, and the pressure value of the pressure gauge 15 of the circulating water supply main pipe is interlocked. When the circulating water of the hydrogen chloride synthesis furnace circulating water cooler 1 and the hydrochloric acid falling film absorber changes from "series mode" to "parallel mode", the system flow demand increases, the variable frequency pump automatically increases the frequency, stabilizes the system pressure, and increases the water supply flow.

Claims

1. A circulating water cascade heat exchange system for a hydrogen chloride synthesis furnace, characterized in that, The system includes several cooling towers (12), the upper ends of which are connected to the circulating water cooler (1), the primary hydrochloric acid falling film absorber (5), and the secondary hydrochloric acid falling film absorber (6) of the hydrogen chloride synthesis furnace through the return water header of the circulating water system. The bottom of the cooling towers (12) is connected to the cold water tank (13), which is connected to the circulating water cooler (1), the primary hydrochloric acid falling film absorber (5), and the secondary hydrochloric acid falling film absorber (6) of the hydrogen chloride synthesis furnace.

2. The circulating water cascade heat exchange system for the hydrogen chloride synthesis furnace according to claim 1, characterized in that, The cooling water tank (13) is located at the bottom of the cooling tower (12). The bottom of the cooling water tank (13) is connected to the inlet of several circulating water pumps (14). The outlet of several circulating water pumps (14) is connected to the cold side outlet of the circulating water cooler (1) of the hydrogen chloride synthesis furnace, the cold side outlet of the first-stage hydrochloric acid falling film absorber (5), and the cold side outlet of the second-stage hydrochloric acid falling film absorber (6). A remote pressure gauge (15) for the circulating water supply main pipe is installed on the pipe at the outlet of the circulating water pump (14).

3. The circulating water cascade heat exchange system for the hydrogen chloride synthesis furnace according to claim 2, characterized in that, A synthesis furnace circulating water inlet valve (2) is installed on the pipeline between the cold side inlet of the hydrogen chloride synthesis furnace circulating water cooler (1) and the circulating water pump (14).

4. The circulating water cascade heat exchange system for the hydrogen chloride synthesis furnace according to claim 3, characterized in that, The cold side outlet of the hydrogen chloride synthesis furnace circulating water cooler (1) is connected to the return water main pipe of the circulating water system, and a synthesis furnace circulating water outlet valve (3) is installed on the pipe between the cold side outlet of the hydrogen chloride synthesis furnace circulating water cooler (1) and the return water main pipe of the circulating water system.

5. The circulating water cascade heat exchange system for the hydrogen chloride synthesis furnace according to claim 4, characterized in that, A circulating water inlet valve (7) for the primary hydrochloric acid falling film absorber (5) is installed on the pipeline between the cold side inlet of the primary hydrochloric acid falling film absorber (5) and the circulating water pump (14).

6. The circulating water cascade heat exchange system for the hydrogen chloride synthesis furnace according to claim 5, characterized in that, The cold side outlet of the first-stage hydrochloric acid falling film absorber (5) is connected to the return water main pipe of the circulating water system, and a circulating water outlet valve (8) of the first-stage hydrochloric acid falling film absorber is installed on the pipe between the cold side outlet of the first-stage hydrochloric acid falling film absorber (5) and the return water main pipe of the circulating water system.

7. The circulating water cascade heat exchange system for a hydrogen chloride synthesis furnace according to claim 6, characterized in that, A secondary hydrochloric acid falling film absorber circulating water inlet valve (9) is installed on the pipeline between the cold side inlet of the secondary hydrochloric acid falling film absorber (6) and the circulating water pump (14).

8. The circulating water cascade heat exchange system for a hydrogen chloride synthesis furnace according to claim 7, characterized in that, The cold side outlet of the secondary hydrochloric acid falling film absorber (6) is connected to the return water main pipe of the circulating water system, and a secondary hydrochloric acid falling film absorber circulating water outlet valve (10) is installed on the pipe between the cold side outlet of the secondary hydrochloric acid falling film absorber (6) and the return water main pipe of the circulating water system.

9. The circulating water cascade heat exchange system for a hydrogen chloride synthesis furnace according to claim 8, characterized in that, The circulating water outlet valve (8) of the primary hydrochloric acid falling film absorber, the circulating water outlet valve (10) of the secondary hydrochloric acid falling film absorber, and the return water main pipe of the circulating water system are connected to the circulating water outlet main valve (11).

10. The circulating water cascade heat exchange system for a hydrogen chloride synthesis furnace according to claim 9, characterized in that, The end of the circulating water outlet valve (8) of the first-stage hydrochloric acid falling film absorber away from the first-stage hydrochloric acid falling film absorber (5) and the end of the circulating water outlet valve (10) of the second-stage hydrochloric acid falling film absorber away from the second-stage hydrochloric acid falling film absorber (6) are connected to the cold side inlet of the circulating water cooler (1) of the hydrogen chloride synthesis furnace. A series inlet valve (4) for the circulating water of the synthesis furnace is installed on the pipeline between the cold side inlet of the circulating water cooler (1) of the hydrogen chloride synthesis furnace and the circulating water outlet valve (8) of the first-stage hydrochloric acid falling film absorber and the circulating water outlet valve (10) of the second-stage hydrochloric acid falling film absorber.

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