A process of thermally coupled and pressure swing distillation of hydrochloric acid with low energy consumption

Abstract

The present invention relates to a low-energy-consuming process of thermally coupled and hydrochloric acid pressure swing distillation. A low-energy-consuming process of thermally coupled and hydrochloric acid pressure swing distillation is as follows: in the hydrochloric acid pressure swing distillation process, in combination with the thermal coupling process, the high-temperature and water-containing hydrogen chloride gas extracted from the top of the hydrochloric acid stripping column is used to siphon, heat, flash and reboil the dilute hydrochloric acid extracted from the bottom of the hydrochloric acid stripping column, and then the gas-liquid two-phase enters the dehydration and concentration column. For the low-energy-consuming process of thermally coupled and hydrochloric acid pressure swing distillation described in the present invention, in the hydrochloric acid pressure swing distillation process, by combining the process thermal coupling technology, the energy consumption of the hydrochloric acid stripping process can be reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrochloric acid analysis process, and particularly relates to a low-energy-consuming process of thermal coupling and hydrochloric acid pressure swing distillation. Background Art

[0002] In the existing hydrochloric acid analysis process, there are mainly calcium method deep regulation analysis, pressure swing distillation analysis, etc. Due to the azeotropy of water and hydrogen chloride, it cannot be highly separated by conventional distillation. Among them, in the calcium method deep regulation analysis, because a high-concentration calcium chloride solution is added as an extractant, after the high-temperature and high-concentration calcium chloride solution brings in miscellaneous salt ions, it is extremely easy to scale in the reboiler, thus affecting the good operation of the system.

[0003] Currently, a new hydrochloric acid pressure swing distillation technology has been developed industrially, which separates hydrochloric acid into water and hydrogen chloride. Since this process does not require additional extractant, there is no risk of blockage in the pipelines and equipment in the system, and the production start-up rate during actual operation is higher than that of the calcium method deep regulation analysis. However, it consumes 1.8 - 2.2 tons of steam per ton of hydrochloric acid processed, which is a high-energy-consuming process, and there is currently no more advanced process to reduce energy consumption.

[0004] In view of this, the present invention proposes a new hydrochloric acid distillation process, which combines the process of thermal coupling technology in the conventional hydrochloric acid pressure swing distillation process to reduce energy consumption. Summary of the Invention

[0005] The purpose of the present invention is to provide a low-energy-consuming process of thermal coupling and hydrochloric acid pressure swing distillation. Through the process of thermal coupling technology, using the high-temperature hydrogen chloride gas containing water at the top of the analysis tower, the dilute hydrochloric acid taken out from the bottom of the tower is siphon-heated, flash-boiled, and then the gas-liquid two-phase enters the dehydration and concentration tower. A large amount of enthalpy carried by the high-temperature hydrogen chloride gas containing water at the top of the analysis tower is recovered and utilized in the front section of the dehydration tower feed to achieve the purpose of reducing energy consumption.

[0006] In order to achieve the above purpose, the technical solution adopted is as follows:

[0007] A low-energy-consuming process of thermal coupling and hydrochloric acid pressure swing distillation is as follows: In the hydrochloric acid pressure swing distillation process, combined with the thermal coupling process, using the high-temperature hydrogen chloride gas containing water taken out from the top of the hydrochloric acid analysis tower, the dilute hydrochloric acid taken out from the bottom of the hydrochloric acid analysis tower is siphon-heated, flash-boiled, and then the gas-liquid two-phase enters the dehydration and concentration tower.

[0008] Further, the process includes the following steps:

[0009] (1) Send the hydrochloric acid solution to the hydrochloric acid analysis tower. After evaporating part of the hydrochloric acid through the reboiler at the bottom of the hydrochloric acid analysis tower, hydrogen chloride gas containing water vapor is taken out from the top of the tower, and dilute hydrochloric acid is taken out from the bottom of the tower;

[0010] (2) The dilute hydrochloric acid described is sent to a dilute acid flash tank and heated by a flash reboiler for vacuum flash treatment;

[0011] The flash reboiler utilizes the heat of the hydrogen chloride gas containing water vapor extracted from the top of the hydrochloric acid stripping tower. After use, the hydrogen chloride gas containing water vapor extracted from the top of the hydrochloric acid stripping tower enters the top condenser of the stripping tower for cooling and then enters the demister of the stripping tower for hydrogen chloride gas to remove the mist in the hydrogen chloride gas, obtaining high-purity hydrogen chloride gas;

[0012] (3) The material after vacuum flash enters a hydrochloric acid dehydration and concentration tower for dehydration and concentration. The hydrochloric acid concentrated at the bottom of the tower is transported to the hydrochloric acid stripping tower for cyclic stripping;

[0013] The acid-containing water vapor extracted from the top of the hydrochloric acid dehydration and concentration tower enters the top condenser of the dehydration tower for condensation and then enters the waste acid water tank of the dehydration tower.

[0014] Furthermore, in the step (1), the concentration of the hydrochloric acid solution is greater than 20 wt%.

[0015] Furthermore, in the step (1), the hydrogen chloride gas containing water vapor with a temperature of 133 ± 5 °C and a pressure of 200 ± 10 kPag is extracted from the top;

[0016] The dilute hydrochloric acid with a temperature of 141 ± 2 °C and a pressure of 200 ± 10 kPag is extracted from the bottom of the tower.

[0017] Furthermore, in the step (2), after being sent to the dilute acid flash tank, the pressure is reduced to -90 ± 5 kPag for flash evaporation until the temperature reaches 58 ± 5 °C;

[0018] The temperature of the hydrogen chloride gas containing water vapor extracted from the top of the hydrochloric acid stripping tower after use is 60 ± 5 °C;

[0019] It enters the top condenser of the stripping tower and is cooled to 0 ± 5 °C.

[0020] Furthermore, in the step (2), the condensate generated by the demister of the stripping tower for hydrogen chloride gas and the liquid-phase concentrated hydrochloric acid condensed by the top condenser of the stripping tower are returned to the hydrochloric acid stripping tower for stripping.

[0021] Furthermore, in the step (3), the concentration tower performs dehydration and concentration at a tower pressure of -93 ± 3 kPag;

[0022] The top condenser of the dehydration tower condenses to 35 ± 5 °C.

[0023] Furthermore, in the step (3), the hydrochloric acid at the bottom of the tower is concentrated to 24 wt%.

[0024] Furthermore, in step (3), the material discharging section of the overhead condenser of the dehydration tower is evacuated by a vacuum pump of the dehydration tower to maintain a negative pressure in the hydrochloric acid dehydration and concentration tower and the acid flash tank. A part of the waste acid water in the waste acid water tank of the dehydration tower flows back into the hydrochloric acid dehydration and concentration tower.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] The present invention discloses a low-energy consumption process of thermal coupling and hydrochloric acid variable pressure distillation. By using the thermal coupling technology, the high-temperature hydrogen chloride gas containing water at the top of the analytical tower is used to siphon and heat-flash and reboil the dilute hydrochloric acid drawn from the bottom of the tower. Then, the gas-liquid two-phase enters the dehydration and concentration tower, and a large amount of enthalpy carried by the high-temperature hydrogen chloride gas containing water at the top of the analytical tower is recovered and utilized in the front section of the dehydration tower feed. After using the technical solution of the present invention, the energy consumption of the hydrochloric acid variable pressure distillation process can be reduced from 1.8 - 2.2 tons to 1.5 - 1.7 tons, that is, the energy consumption of the hydrochloric acid variable pressure distillation process is reduced by 20% by this technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a device diagram adopted by the technical solution of the present invention; wherein, 1 is a hydrochloric acid analytical tower, 2 is a top condenser of the hydrochloric acid analytical tower, 3 is a hydrochloric acid gas demister of the analytical tower, 4 is a reboiler of the hydrochloric acid analytical tower, 5 is a dehydration and concentration hydrochloric acid transfer pump, 6 is a hydrochloric acid dehydration and concentration tower, 7 is a reboiler of the hydrochloric acid dehydration tower, 8 is a waste water transfer pump of the dehydration tower, 9 is an overhead condenser of the dehydration tower, 10 is a vacuum pump of the dehydration tower, 11 is a waste acid water tank of the dehydration tower, 12 is a double-effect flash reboiler, 13 is a hydrochloric acid flash tank; A is hydrochloric acid with a feed concentration > 20%, B is 0.5% waste acid water, and C is the discharged hydrogen chloride gas. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] In order to further elaborate on a low-energy consumption process of thermal coupling and hydrochloric acid variable pressure distillation of the present invention to achieve the intended invention purpose, the following combines preferred embodiments to detail the specific implementation manner, structure, characteristics and functions of a low-energy consumption process of thermal coupling and hydrochloric acid variable pressure distillation proposed according to the present invention. In the following description, different "one embodiment" or "embodiment" do not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics in one or more embodiments can be combined in any suitable form.

[0029] The following will further introduce in detail a low-energy consumption process of thermal coupling and hydrochloric acid variable pressure distillation of the present invention in combination with specific embodiments:

[0030] The present invention discloses a low - energy - consumption process of thermal coupling and pressure - swing distillation of hydrochloric acid. By using thermal coupling technology, the high - temperature hydrogen chloride gas containing water at the top of the stripping tower is used to siphon - heat, flash - vaporize and re - boil the dilute hydrochloric acid withdrawn from the bottom of the tower. Then, the gas - liquid two - phase enters the dehydration and concentration tower, and a large amount of enthalpy carried by the high - temperature hydrogen chloride gas containing water at the top of the stripping tower is recovered and utilized in the front section of the dehydration tower feed, so as to achieve the purpose of reducing energy consumption. The technical solution of the present invention is as follows:

[0031] A low - energy - consumption process of thermal coupling and pressure - swing distillation of hydrochloric acid is as follows: In the pressure - swing distillation process of hydrochloric acid, combined with the thermal coupling process, the high - temperature hydrogen chloride gas containing water withdrawn from the top of the hydrochloric acid stripping tower is used to siphon - heat, flash - vaporize and re - boil the dilute hydrochloric acid withdrawn from the bottom of the hydrochloric acid stripping tower, and then the gas - liquid two - phase enters the dehydration and concentration tower.

[0032] Preferably, the process includes the following steps:

[0033] (1) Send the hydrochloric acid solution to the hydrochloric acid stripping tower. After evaporating part of the hydrochloric acid through the re - boiler at the bottom of the hydrochloric acid stripping tower, hydrogen chloride gas containing water vapor is withdrawn from the top of the tower, and dilute hydrochloric acid is withdrawn from the bottom of the tower;

[0034] (2) After the dilute hydrochloric acid is sent to the dilute acid flash tank, it is heated by the flash re - boiler for vacuum flash treatment;

[0035] The flash re - boiler utilizes the heat of the hydrogen chloride gas containing water vapor withdrawn from the top of the hydrochloric acid stripping tower. After use, the hydrogen chloride gas containing water vapor withdrawn from the top of the hydrochloric acid stripping tower enters the top condenser of the stripping tower for cooling, and then enters the hydrogen chloride gas demister in the stripping tower to remove the mist in the hydrogen chloride gas, obtaining high - purity hydrogen chloride gas;

[0036] (3) The material after vacuum flash enters the hydrochloric acid dehydration and concentration tower for dehydration and concentration. The concentrated hydrochloric acid at the bottom of the tower is transported to the hydrochloric acid stripping tower for cyclic stripping;

[0037] The acid - containing water vapor withdrawn from the top of the hydrochloric acid dehydration and concentration tower enters the top condenser of the dehydration tower for condensation, and then enters the waste acid water tank of the dehydration tower.

[0038] Further preferably, in the step (1), the concentration of the hydrochloric acid solution is greater than 20wt%.

[0039] Further preferably, in the step (1), hydrogen chloride gas containing water vapor with a temperature of 133 ± 5°C and a pressure of 200 ± 10kPag is withdrawn from the top of the tower;

[0040] Dilute hydrochloric acid with a temperature of 141 ± 2°C and a pressure of 200 ± 10kPag is withdrawn from the bottom of the tower.

[0041] Further preferably, in the step (2), after being sent to the dilute acid flash tank, the pressure is reduced to -90±5 kPag for flashing until the temperature reaches 58±5 °C;

[0042] The temperature of the hydrogen chloride gas containing water vapor taken from the top of the used hydrochloric acid stripping tower is 60±5 °C;

[0043] It enters the condenser at the top of the stripping tower and is cooled to 0±5 °C.

[0044] Further preferably, in the step (2), the condensate generated by the demister for hydrogen chloride gas in the stripping tower and the liquid-phase concentrated hydrochloric acid condensed by the condenser at the top of the stripping tower are returned to the hydrochloric acid stripping tower for stripping.

[0045] Further preferably, in the step (3), the concentration tower performs dehydration and concentration at a tower pressure of -93±3 kPag;

[0046] The condenser at the top of the dehydration tower condenses to 35±5 °C.

[0047] Further preferably, in the step (3), the hydrochloric acid at the bottom of the tower is concentrated to 24 wt%.

[0048] Further preferably, in the step (3), the feeding section of the condenser at the top of the dehydration tower is evacuated by the vacuum pump of the dehydration tower to maintain the negative pressure of the hydrochloric acid dehydration and concentration tower and the acid flash tank. A part of the waste acid water in the waste acid water tank of the dehydration tower flows back into the hydrochloric acid dehydration and concentration tower.

[0049] Example 1.

[0050] Combined with Figure 1 , the specific operation steps are as follows:

[0051] (1) Hydrochloric acid with a concentration > 20 wt% (material A) enters the hydrochloric acid stripping tower (①). Part of the hydrochloric acid is evaporated through the reboiler (4) at the bottom of the hydrochloric acid stripping tower. After gas-liquid mass transfer in the tower, the concentration of hydrochloric acid at the bottom of the tower is reduced to 18.5 wt%. The hydrogen chloride gas containing water vapor with a temperature of 133±5 °C and a pressure of 200±10 kPag is taken from the top of the tower, and the dilute hydrochloric acid with a temperature of 141±2 °C and a pressure of 200±10 kPag is taken from the bottom of the tower.

[0052] (2) The dilute hydrochloric acid enters the dilute acid flash tank (13) again, and the pressure is reduced to -90±5 kPag for flashing until the temperature reaches 58±5 °C. The dilute acid flash tank (13) is heated by the flash reboiler (12).

[0053] The flash reboiler (12) continues to heat and evaporate using the hydrogen chloride gas containing water vapor taken from the top of the tower to recover the waste heat in the top gas.

[0054] The hydrogen chloride gas containing water vapor after waste heat utilization becomes the hydrogen chloride gas containing water vapor that is partially liquefied at 60 ± 5 °C, enters the top condenser (2) of the stripping column and is cooled to 0 ± 5 °C. After condensation, hydrogen chloride gas with a purity of 99.9 wt% is produced, enters the demister (3) for hydrogen chloride gas in the stripping column to remove the mist in the hydrogen chloride gas, and high-purity hydrogen chloride gas (material C) is obtained for use in other systems. The condensate generated by the demister and the concentrated hydrochloric acid in the liquid phase condensed by the top condenser of the hydrochloric acid stripping column are returned to the hydrochloric acid stripping column for stripping.

[0055] (3) The dilute hydrochloric acid drawn from the bottom of the hydrochloric acid stripping column is subjected to vacuum evaporation, and the dilute hydrochloric acid and the mixed gas after evaporation enter the negative-pressure hydrochloric acid dehydration and concentration tower (6) to perform dehydration and concentration at a tower pressure of -93 ± 3 kPag.

[0056] The bottom of the dehydration and concentration tower is heated by the hydrochloric acid dehydration tower reboiler (7) to continue evaporating part of the hydrochloric acid and concentrate the hydrochloric acid at the bottom of the tower to 24%. The concentrated hydrochloric acid is continuously transported to the hydrochloric acid stripping column for cyclic stripping by the dehydrated and concentrated hydrochloric acid transfer pump (5).

[0057] The acid-containing water vapor at the top of the dehydration and concentration tower (6) enters the top condenser (9) of the dehydration tower and is condensed to 35 ± 5 °C. The 0.5 wt% waste acid water after condensation enters the waste acid water tank (11) of the dehydration tower. The feeding section at the bottom of the top condenser of the dehydration tower is evacuated by the dehydration tower vacuum pump (10) to maintain the negative pressure in the hydrochloric acid dehydration and concentration tower and the acid flash tank. Part of the waste acid water (about 35%) in the waste acid water tank of the dehydration tower flows back into the dehydration tower, and the remaining waste acid water (about 65%, material B) is externally collected for sewage treatment.

[0058] After actual operation, the energy consumption for treating each ton of hydrochloric acid is reduced from 1.8 - 2.2 tons to 1.5 - 1.7 tons, reducing the energy consumption of the hydrochloric acid variable pressure distillation process by 20%.

[0059] The above is only the preferred embodiment of the embodiments of the present invention, and does not impose any form of limitation on the embodiments of the present invention. Any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the embodiments of the present invention still fall within the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A process for thermally coupled and hydrochloric acid pressure swing distillation with low energy consumption, characterized in that, The described process is as follows: In the hydrochloric acid pressure swing distillation process, in combination with the heat integration process, using the high-temperature, water-containing hydrogen chloride gas extracted from the top of the hydrochloric acid stripping column, the dilute hydrochloric acid extracted from the bottom of the hydrochloric acid stripping column is siphon-heated, flash-boiled, and then the gas-liquid two-phase enters the dehydration and concentration column; The described process specifically includes the following steps: (1) Send the hydrochloric acid solution to the hydrochloric acid stripping column. After evaporating part of the hydrochloric acid through the reboiler at the bottom of the hydrochloric acid stripping column, extract the water-containing hydrogen chloride gas from the top of the column, and extract the dilute hydrochloric acid from the bottom of the column; (2) Send the described dilute hydrochloric acid to the dilute acid flash tank, and heat it through the flash reboiler for vacuum flash distillation treatment; The flash reboiler utilizes the heat of the water-containing hydrogen chloride gas extracted from the top of the hydrochloric acid stripping column. After use, the water-containing hydrogen chloride gas extracted from the top of the hydrochloric acid stripping column enters the top condenser of the stripping column for cooling, and then enters the hydrogen chloride gas demister in the stripping column to remove the mist in the hydrogen chloride gas, obtaining high-purity hydrogen chloride gas; (3) The material after the vacuum flash distillation enters the hydrochloric acid dehydration and concentration column for dehydration and concentration. The concentrated hydrochloric acid at the bottom of the column is transported to the described hydrochloric acid stripping column for cyclic stripping; The acid-containing water vapor extracted from the top of the hydrochloric acid dehydration and concentration column enters the top condenser of the dehydration column for condensation, and then enters the waste acid water tank of the dehydration column.

2. The process according to claim 1, wherein in the step (1), the concentration of the hydrochloric acid solution is greater than 20 wt%.

3. The process according to claim 1, wherein in the step (1), extract the water-containing hydrogen chloride gas at 133 ± 5 °C and with a pressure of 200 ± 10 kPag from the top of the column; extract the dilute hydrochloric acid at 141 ± 2 °C and with a pressure of 200 ± 10 kPag from the bottom of the column.

4. The process according to claim 1, wherein in the step (2), after sending it to the dilute acid flash tank, reduce the pressure to -90 ± 5 kPag for flash distillation until the temperature reaches 58 ± 5 °C; the temperature of the water-containing hydrogen chloride gas extracted from the top of the hydrochloric acid stripping column after use is 60 ± 5 °C; enter the top condenser of the stripping column and cool it to 0 ± 5 °C.

5. The process according to claim 1, wherein in the step (2), the condensate generated by the hydrogen chloride gas demister in the stripping column and the liquid-phase concentrated hydrochloric acid condensed by the top condenser of the stripping column are returned to the hydrochloric acid stripping column for stripping.

6. The process according to claim 1, wherein in the step (iii), the concentration column performs dehydration and concentration at a column pressure of -93 ± 3 kPag; the top condenser of the dehydration column condenses to 35 ± 5 °C.

7. The process according to claim 1, wherein in the step (3), the hydrochloric acid at the bottom of the column is concentrated to 24 wt%.

8. The process according to claim 1, wherein in the step (3), the feeding section of the top condenser of the dehydration column is evacuated by the vacuum pump of the dehydration column to maintain the negative pressure of the hydrochloric acid dehydration and concentration column and the hydrochloric acid flash tank. A part of the waste acid water in the waste acid water tank of the dehydration column flows back into the hydrochloric acid dehydration and concentration column.

Images