A separation system and separation method for hydrogen chloride and sulfur dioxide mixed gas

Abstract

The present invention relates to the technical field of separation of mixed gases, and discloses a separation system and a separation method for a mixture of hydrogen chloride and sulfur dioxide. The separation system comprises an absorption tower, a partial condenser, and a production pump. The present invention refluxes part of the kettle liquid to the top of the tower through a reflux pipeline, and uses it as an absorbent after mixing with process water, which is equivalent to using dilute acid as an absorbent for absorption, and can inhibit the transfer of sulfur dioxide to the liquid phase. The present invention dilutes and heats the gas phase containing more sulfur dioxide in the lower tower by directly passing steam through the tower kettle, and the steam simultaneously strips the liquid phase, so that the sulfur dioxide content in the kettle liquid is significantly reduced. The present invention is a normal pressure device, and only one tower is needed, so the equipment cost and energy consumption are low. The equipment in the present invention has great operational flexibility, and the process design and operation and maintenance are very easy.

Description

Technical Field

[0001] The invention relates to the technical field of separation of mixed gases, and in particular to a separation system and a separation method for a mixed gas of hydrogen chloride and sulfur dioxide. Background Art

[0002] In organic synthesis, when chlorination reaction is carried out with sulfonyl chloride or thionyl chloride as chlorinating agent, a large amount of mixed tail gas of sulfur dioxide and hydrogen chloride will be produced. Both sulfur dioxide and hydrogen chloride are valuable industrial raw materials. Direct discharge will not only pollute the environment, but also cause waste.

[0003] The commonly used tail gas treatment solution is multi-stage water absorption plus alkali absorption, which ultimately converts the acidic tail gas into by-product hydrochloric acid and by-product sodium sulfite. However, this process cannot satisfactorily separate hydrogen chloride and sulfur dioxide. A considerable amount of sulfur dioxide is dissolved in the by-product hydrochloric acid obtained, which not only introduces impurities when the by-product hydrochloric acid is used, but also the reducing sulfur dioxide will directly damage some reaction systems. A large amount of by-product hydrochloric acid and sodium sulfite cannot be properly utilized due to purity issues, and can only be treated as wastewater after neutralization.

[0004] High-purity hydrogen chloride and sulfur dioxide can be obtained by treating the mixed tail gas with the pressure swing distillation process. However, the equipment used in the pressure swing distillation process is very complicated, including multiple distillation towers and a large number of pipelines. The liquid sulfur dioxide and hydrogen chloride mixture is an extremely strong proton acid, and the equipment needs to use relatively expensive corrosion-resistant materials, resulting in high equipment costs. In addition, the pressure swing distillation process inevitably requires vacuum operation, which consumes a lot of electricity.

[0005] The solubility of sulfur dioxide in acid will decrease significantly, and the diffusion rate of sulfur dioxide into the solution is significantly lower than that of hydrogen chloride. Using dilute hydrochloric acid as an absorbent can reduce the sulfur dioxide content in the by-product hydrochloric acid obtained by the absorption method.

[0006] In addition, a large amount of heat is released during the dissolution of hydrogen chloride, which can even make the solution boil. The azeotropic point of hydrogen chloride and water under normal pressure is 110°C, and the molar concentration of hydrogen chloride is 20.24%. Summary of the invention

[0007] The invention provides a separation system and a separation method for a hydrogen chloride and sulfur dioxide mixed gas.

[0008] The technical problem to be solved is that the absorption method for treating the mixed tail gas of sulfur dioxide and hydrogen chloride will produce a large amount of low-purity by-product hydrochloric acid that is difficult to utilize, and the pressure swing distillation method for treating the mixed tail gas of sulfur dioxide and hydrogen chloride has high equipment cost and energy consumption.

[0009] In order to solve the above technical problems, the present invention adopts the following technical solution: a separation system of hydrogen chloride and sulfur dioxide mixed gas, characterized in that it includes an absorption tower, a partial condenser, and a production pump;

[0010] The side line feed port of the absorption tower is connected to the mixed gas feed pipe;

[0011] The top extraction port of the absorption tower is connected to the feed port of the partial condenser through the top extraction pipe, and the condensate outlet of the partial condenser is connected to the top feed port of the absorption tower through the condensate pipe; the non-condensable steam outlet of the partial condenser is connected to the sulfur dioxide discharge pipe;

[0012] The kettle liquid extraction port of the absorption tower is connected to the liquid inlet of the extraction pump through the kettle liquid extraction pipe, and the liquid outlet of the extraction pump is connected to the top feed port of the absorption tower through the pump rear pipe;

[0013] The absorption tower kettle is connected to the steam feed pipe, and the steam feed port is arranged higher than the liquid level of the tower kettle;

[0014] A reflux control valve is arranged on the rear pipe of the pump, a hydrochloric acid outlet is arranged in front of the reflux control valve, and the hydrochloric acid outlet is connected to the hydrochloric acid outlet pipe; a process water feed port is arranged behind the reflux control valve, and the process water feed port is connected to the process water feed pipe.

[0015] Furthermore, the absorption tower is a packed tower, the packing layer of the packed tower is divided into two sections, including an upper packing layer and a lower packing layer, and the mixed gas feed pipe is connected to a side line feed port on the packed tower shell located between the upper packing layer and the lower packing layer.

[0016] Furthermore, the packed tower is a variable diameter tower, the lower tower diameter is smaller than the upper tower; the upper packing layers are all arranged in the upper tower body, the lower packing layers are all arranged in the lower tower body, and the filling height of the lower packing layers is smaller than that of the upper packing layers.

[0017] Furthermore, the steam feed pipe is provided with a steam feed valve, the mixed gas feed pipe is provided with a mixed gas feed valve, the tower top production pipe is provided with a tower top production valve, the tower bottom production pipe is provided with a tower bottom production valve, the process water feed pipe is provided with a process water feed valve, and the hydrochloric acid discharge pipe is provided with a hydrochloric acid discharge valve.

[0018] Furthermore, the process water feed pipe is connected to an acid replenishing pipe, and an acid replenishing valve is provided on the acid replenishing pipe.

[0019] A method for separating a mixed gas of hydrogen chloride and sulfur dioxide, wherein the mixed gas is countercurrently absorbed in an absorption tower using process water introduced from the top of the tower as an absorbent, sulfur dioxide gas is produced from the top of the tower, and hydrochloric acid is produced and recovered from the bottom of the tower; the separation method is characterized in that:

[0020] The mixed gas is fed at the side line of the absorption tower, and steam is directly fed into the tower kettle. The steam feeding position is higher than the maximum liquid level allowed in the tower kettle. The steam fed into the tower kettle dilutes and heats the gas phase in the tower located below the mixed gas feed port, and strips the liquid phase in the tower located below the mixed gas feed port.

[0021] The gas phase produced from the top of the tower is condensed and dehumidified in the partial condenser, and the condensate is pumped back to the top of the tower, and all the non-condensable steam is produced;

[0022] Part of the recovered hydrochloric acid extracted from the tower bottom is refluxed to the top of the tower to inhibit the dissolution of sulfur dioxide in the mixed gas;

[0023] The sum of the mass flow rates of process water and steam shall not be less than 1.7 times the mass flow rate of hydrogen chloride in the mixed gas.

[0024] Further, the separation method uses the separation system of claim 1;

[0025] And includes the following process:

[0026] Step 1, mixed gas absorption: the mixed gas is fed from the side feed port of the absorption tower and flows upward, and is countercurrently contacted with the dilute acid flowing down from the top of the tower. The mixed gas removes hydrogen chloride and becomes sulfur dioxide gas containing a certain amount of water, which is extracted from the top of the tower and enters the partial condenser; the dilute acid absorbs hydrogen chloride and a small amount of sulfur dioxide in the mixed gas and becomes recovered hydrochloric acid, which heats up and continues to flow downward;

[0027] Step 2, sulfur dioxide condensation and dehumidification: The sulfur dioxide gas containing a certain amount of water extracted from the top of the tower is condensed in the partial condenser, the hydrochloric acid mist and most of the water enter the condensate and are returned to the top of the absorption tower, and the sulfur dioxide gas is extracted from the non-condensable steam outlet of the partial condenser as a gas phase product;

[0028] Step 3, stripping of recovered hydrochloric acid: in the tower section below the mixed gas feed port of the absorption tower, the recovered hydrochloric acid is countercurrently contacted with the steam introduced into the tower kettle, and part of the sulfur dioxide in the recovered hydrochloric acid enters the steam; the steam flows upward and merges into the mixed gas, and the recovered hydrochloric acid flows into the tower kettle and is produced from the kettle liquid production port;

[0029] Step 4, kettle liquid reflux: part of the recovered hydrochloric acid extracted from the tower kettle is mixed with process water to form dilute hydrochloric acid and then refluxed to the top of the absorption tower; the remaining recovered hydrochloric acid is extracted as a liquid product.

[0030] Furthermore, during the start-up of the separation system, the kettle liquid reflux rate is set to 0, all the kettle liquid extracted from the tower bottom is extracted as waste liquid, and hydrochloric acid with the same mass flow rate and acidity as the recovered hydrochloric acid refluxed in step four during normal production is added to the process water.

[0031] Furthermore, the absorption tower is operated at normal pressure.

[0032] Furthermore, the liquid phase temperature in the tower at the height of the mixed gas feed port in step one is not lower than 100°C, and the steam feed temperature in step three is not lower than 110°C.

[0033] Compared with the prior art, the separation system and separation method of the hydrogen chloride and sulfur dioxide mixed gas of the present invention have the following beneficial effects:

[0034] The present invention refluxes part of the kettle liquid to the top of the tower through a reflux pipeline and uses it as an absorbent after mixing with process water, which is equivalent to using dilute acid as an absorbent for absorption. Compared with direct absorption with process water, it can inhibit the transfer of sulfur dioxide to the liquid phase.

[0035] The present invention provides a steam inlet at the bottom of the tower to directly pass steam into the tower, dilute and heat the gas phase containing more sulfur dioxide in the lower tower, reduce the sulfur dioxide partial pressure, increase the Henry coefficient of sulfur dioxide, thereby reducing the solubility of sulfur dioxide and inhibiting its transfer to the liquid phase. At the same time, the steam strips the liquid phase to remove part of the dissolved sulfur dioxide, and finally significantly reduces the sulfur dioxide content in the bottom liquid.

[0036] The equipment used in the present invention is normal pressure equipment, and only one tower is needed, so the equipment cost and energy consumption are low.

[0037] The equipment used in the present invention has great operational flexibility, and the process design as well as operation and maintenance are very easy. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a schematic structural diagram of a system for separating a mixture of hydrogen chloride and sulfur dioxide of the present invention;

[0039] Among them, 1-absorption tower, 11-liquid distributor, 121-upper packing layer, 122-lower packing layer, 2-separator, 31-steam feed valve, 32-mixed gas feed valve, 33-tower top production valve, 341-process water feed valve, 342-acid supplement valve, 35-reflux control valve, 36-hydrochloric acid discharge valve, 37-tower bottom production valve, 4-production pump, 51-steam feed pipe, 52-mixed gas feed pipe, 53-tower top production pipe, 54-sulfur dioxide discharge pipe, 55-condensate pipe, 561-process water feed pipe, 562-acid supplement pipe, 57-hydrochloric acid discharge pipe, 581-kettle liquid production pipe, 582-pump rear pipe. DETAILED DESCRIPTION

[0040] like Figure 1 As shown, a separation system of a hydrogen chloride and sulfur dioxide mixed gas of the present invention comprises an absorption tower 1, a partial condenser 2, and a production pump 4;

[0041] The side feed port of the absorption tower 1 is connected to the mixed gas feed pipe 52; the bottom of the absorption tower 1 is connected to the steam feed pipe 51;

[0042] The top outlet of the absorption tower 1 is connected to the feed port of the partial condenser 2 through the top outlet pipe 53, and the condensate outlet of the partial condenser 2 is connected to the top feed port of the absorption tower 1 through the condensate pipe 55; the non-condensable steam outlet of the partial condenser 2 is connected to the sulfur dioxide discharge pipe 54;

[0043] The bottom of the absorption tower 1 is connected to the steam feed pipe 51, and the steam feed port is set higher than the highest liquid level line of the bottom of the tower; because the purpose of passing steam through the bottom of the tower in this system is to strip and inhibit the dissolution of sulfur dioxide, not to directly exchange heat.

[0044] The kettle liquid extraction port of the absorption tower 1 is connected to the liquid inlet of the extraction pump 4 through the kettle liquid extraction pipe 581, and the liquid outlet of the extraction pump 4 is connected to the tower top feed port of the absorption tower 1 through the pump rear pipe 582;

[0045] A reflux control valve 35 is provided on the rear pipe 582 of the pump, and a hydrochloric acid outlet is provided in front of the reflux control valve 35, and the hydrochloric acid outlet is connected to the hydrochloric acid outlet pipe 57; a process water feed inlet is provided after the reflux control valve 35, and the process water feed inlet is connected to the process water feed pipe 561.

[0046] The steam feed pipe 51 is provided with a steam feed valve 31, the mixed gas feed pipe 52 is provided with a mixed gas feed valve 32, the tower top production pipe 53 is provided with a tower top production valve 33, the tower bottom production pipe is provided with a tower bottom production valve 37, the process water feed pipe 561 is provided with a process water feed valve 341, and the hydrochloric acid discharge pipe 57 is provided with a hydrochloric acid discharge valve 36.

[0047] The side of the process water feed pipe 561 is connected to the acid supplement pipe 562, and the acid supplement pipe 562 is provided with an acid supplement valve 342. The acid supplement pipe 562 is provided to facilitate the start-up.

[0048] The absorption tower 1 can be a plate tower or a packed tower, but the packed tower structure is more compact. If a packed tower is used, the packing layer of the packed tower is divided into two sections, including an upper packing layer 121 and a lower packing layer 122, and the mixed gas feed pipe 52 is connected to the side line feed port located between the upper packing layer 121 and the lower packing layer 122 on the packed tower shell. The packed tower is a variable diameter tower, the lower tower diameter is smaller than the upper section, and the filling height of the lower packing layer 122 is smaller than the upper packing layer 121. Because in the lower section of the tower, the gas phase load is significantly reduced, and the function of the lower packing layer 122 is mainly stripping rather than absorption. The viscosity of the liquid phase feed at the top of the tower is not high, and the liquid distributor 11 of the packed tower can be selected from the spray type liquid distributor 11. In addition, since the diameter of the lower packing layer 122 is not large, a liquid redistributor may not be provided.

[0049] The cooling medium of the partial condenser 2 is desalted water. The main function of the partial condenser 2 is to separate the acid mist and part of the water in the gas phase extracted from the top of the tower. The condensate can be directly returned to the absorption tower 1. A buffer tank can also be set on the condensate pipe 55.

[0050] The system has a large operational flexibility, allowing manual adjustment of each valve to operate without a PID control system. However, it can also be controlled by incorporating each valve into a PID control system according to process design.

[0051] A separation system of a hydrogen chloride and sulfur dioxide mixed gas in this embodiment, the start-up process of which includes the following steps:

[0052] Step 1, close the mixed gas feed valve 32, the tower top extraction valve 33, the process water feed valve 341, the acid supplement valve 342, the tower bottom extraction valve 37, and the reflux control valve 35, open the hydrochloric acid discharge valve 36 and the steam feed valve 31, pass steam from the steam feed pipe 51 to replace the gas phase in the tower; pass cooling water to the partial condenser 2;

[0053] Step 2, when condensate flows in the condensate pipe 55, open the process water feed valve 341 and the acid replenishing valve 342, and pass hydrochloric acid into the process water from the acid replenishing pipe 562. The mass flow rate and acidity of the hydrochloric acid passed in are the same as those of the recycled hydrochloric acid refluxed in the normal production process. The hydrochloric acid passed in can be the recycled hydrochloric acid previously produced by the system or purchased hydrochloric acid;

[0054] Step 3, when the kettle liquid level reaches 50%, open the kettle extraction valve 37; when the kettle liquid extraction pipe 581 is full of liquid, start the extraction pump 4 and open the hydrochloric acid discharge valve 36;

[0055] Step 4, opening the mixed gas feed valve 32, and passing the mixed gas of hydrogen chloride and sulfur dioxide through the mixed gas feed pipe 52;

[0056] Step 5: When the acidity of the kettle liquid reaches the process design requirement, open the reflux control valve 35 and close the acid replenishment valve 342.

[0057] A method for separating a mixed gas of hydrogen chloride and sulfur dioxide using the above separation system, wherein water introduced into the top of the tower is used as an absorbent to countercurrently absorb the mixed gas in an absorption tower 1, sulfur dioxide gas is produced from the top of the tower, and hydrochloric acid is produced and recovered from the bottom of the tower; the main points of the separation method are:

[0058] The mixed gas is fed between the upper and lower layers of packing in the absorption tower 1, and steam is directly passed through the bottom of the tower; the gas phase is absorbed in the upper packing layer 121 of the tower to absorb the hydrogen chloride in the mixed gas; the liquid phase is stripped in the lower packing layer 122 to remove the sulfur dioxide that enters the liquid phase. Note that the temperature of the recovered hydrochloric acid entering the lower packing layer 122 should not be lower than 100°C, that is, the boiling point of water under the pressure in the tower; and the steam feed temperature should not be lower than 110°C, that is, the azeotropic point of water and hydrogen chloride under the pressure in the tower; otherwise, most of the stripping steam will be liquefied and stripping cannot be carried out. The temperature of the recovered hydrochloric acid entering the lower packing layer 122 can be controlled by controlling the process water feed temperature, the mixed gas feed temperature and / or the process water flow rate.

[0059] The gas phase produced from the top of the tower is condensed and dehumidified in the partial condenser 2, and the condensate is returned to the top of the tower, and all the non-condensable steam is produced;

[0060] Part of the recovered hydrochloric acid extracted from the tower bottom flows back to the top of the tower, mixes with process water to form dilute hydrochloric acid, and then flows down from the top of the tower, which can inhibit the dissolution of sulfur dioxide from the top of the tower into the liquid phase. Note that the refluxed recovered hydrochloric acid should not be directly injected into the tower, but should be mixed with process water first, and the mass fraction of hydrogen chloride after mixing with process water should be less than 20%, otherwise part of the hydrogen chloride in the liquid phase at the top of the tower will volatilize into the gas phase, polluting the gas phase product.

[0061] The process includes the following: mixed gas absorption: the mixed gas is fed from the side feed port of the absorption tower 1 and flows upward, and is countercurrently contacted with the dilute acid flowing down from the top of the tower, and the mixed gas removes hydrogen chloride to become sulfur dioxide gas containing a certain amount of water, which is extracted from the top of the tower and enters the partial condenser 2; the dilute acid absorbs hydrogen chloride and a small amount of sulfur dioxide in the mixed gas to become recovered hydrochloric acid, which is heated and continues to flow downward;

[0062] Sulfur dioxide condensation and dehumidification: The sulfur dioxide gas containing a certain amount of water extracted from the top of the tower is condensed in the partial condenser 2, the hydrochloric acid mist and most of the water enter the condensate and are returned to the top of the absorption tower 1, and the sulfur dioxide gas is extracted from the non-condensable steam outlet of the partial condenser 2 as a gas phase product;

[0063] Recovered hydrochloric acid stripping: In the tower section of the absorption tower 1 located below the mixed gas feed port, the recovered hydrochloric acid is countercurrently contacted with the steam introduced into the tower kettle, and part of the sulfur dioxide in the recovered hydrochloric acid enters the steam; the steam flows upward and merges into the mixed gas, and the recovered hydrochloric acid flows into the tower kettle and is produced from the kettle liquid production port;

[0064] Kettle liquid reflux: Part of the recovered hydrochloric acid taken from the tower kettle is mixed with process water to form dilute hydrochloric acid and then refluxed to the top of absorption tower 1; the remaining recovered hydrochloric acid is taken out as a liquid product.

[0065] Case 1:

[0066] Process water: temperature 40°C, flow rate 13000kg / h;

[0067] Steam: 7 bar saturated steam, flow rate 270 kg / h;

[0068] Condenser 2: The cooling medium is 20℃ desalted water, and the non-condensable steam temperature is 40℃;

[0069] Mixed gas: HCl and SO 2 Mass ratio 1:1, temperature 40°C, flow rate 10800kg / h;

[0070] Filler: Ceramic filler, the upper filler layer 121 is 6 meters high and 1.8 meters in diameter, and the lower filler layer 122 is 2 meters high and 1 meter in diameter;

[0071] The tower bottom liquid level is controlled at 50%, and the reflux rate is 1300kg / h;

[0072] In this case, the mass concentration of hydrogen chloride in the recovered hydrochloric acid extracted from the bottom of the tower is 30.4%, SO 2 The mass concentration is 0.0451%; SO in the non-condensable steam produced by partial condenser 2 2 The mass concentration is 98.2%, reaching 99.99% after drying.

[0073] Case 2:

[0074] Process water: temperature 40°C, flow rate 13000kg / h;

[0075] Steam: 7 bar saturated steam, flow rate 440 kg / h;

[0076] Condenser 2: The cooling medium is 20℃ desalted water, and the non-condensable steam temperature is 40℃;

[0077] Mixed gas: HCl and SO 2 Mass ratio 1:1, temperature 40°C, flow rate 10800kg / h;

[0078] Filler: Ceramic filler, the upper filler layer 121 is 6 meters high and 1.8 meters in diameter, and the lower filler layer 122 is 2 meters high and 1 meter in diameter;

[0079] The tower bottom liquid level is controlled at 50%, and the reflux rate is 1300kg / h;

[0080] In this case, the mass concentration of hydrogen chloride in the recovered hydrochloric acid extracted from the bottom of the tower is 30.1%, SO 2 The mass concentration is 0.0232%; SO in the non-condensable steam produced by the partial condenser 2 2 The mass concentration is 98.2%, reaching 99.99% after drying.

[0081] Case 3:

[0082] Process water: temperature 40°C, flow rate 13000kg / h;

[0083] Steam: 7 bar saturated steam, flow rate 1400 kg / h;

[0084] Condenser 2: The cooling medium is 20℃ desalted water, and the non-condensable steam temperature is 40℃;

[0085] Mixed gas: HCl and SO 2 Mass ratio 1:1, temperature 40°C, flow rate 10800kg / h;

[0086] Filler: Ceramic filler, the upper filler layer 121 is 6 meters high and 1.8 meters in diameter, and the lower filler layer 122 is 2 meters high and 1 meter in diameter;

[0087] The tower bottom liquid level is controlled at 50%, and the reflux rate is 1300kg / h;

[0088] In this case, the mass concentration of hydrogen chloride in the recovered hydrochloric acid extracted from the bottom of the tower is 28.5%, SO 2 The mass concentration is 0.00274%; SO in the non-condensable steam produced by partial condenser 2 2 The mass concentration is 98.2%, reaching 99.99% after drying.

[0089] Case 4:

[0090] Process water: temperature 40°C, flow rate 13270kg / h;

[0091] Steam: No;

[0092] Condenser 2: The cooling medium is 20℃ desalted water, and the non-condensable steam temperature is 40℃;

[0093] Mixed gas: HCl and SO 2 Mass ratio 1:1, temperature 40°C, flow rate 10800kg / h;

[0094] Filler: Ceramic filler, the upper filler layer 121 is 6 meters high and 1.8 meters in diameter, and the lower filler layer 122 is 2 meters high and 1 meter in diameter;

[0095] The tower bottom liquid level is controlled at 50%, and the reflux rate is 1300kg / h;

[0096] In this case, the mass concentration of hydrogen chloride in the recovered hydrochloric acid extracted from the bottom of the tower is 30.4%, SO 2 The mass concentration is 1.01%; SO in the non-condensable steam produced by partial condenser 2 2 The mass concentration is 98.2%, reaching 99.99% after drying.

[0097] Case 5:

[0098] Process water: temperature 20℃, flow rate 13000kg / h;

[0099] Steam: 7 bar saturated steam, flow rate 270 kg / h;

[0100] Condenser 2: The cooling medium is 20℃ desalted water, and the non-condensable steam temperature is 40℃;

[0101] Mixed gas: HCl and SO 2 Mass ratio 1:1, temperature 40°C, flow rate 10800kg / h;

[0102] Filler: Ceramic filler, the upper filler layer 121 is 6 meters high and 1.8 meters in diameter, and the lower filler layer 122 is 2 meters high and 1 meter in diameter;

[0103] The tower bottom liquid level is controlled at 50%, and the reflux rate is 1300kg / h;

[0104] In this case, the mass concentration of hydrogen chloride in the recovered hydrochloric acid extracted from the bottom of the tower is 30.4%, SO 2 The mass concentration is 1.01%; SO in the non-condensable steam produced by partial condenser 2 2 The mass concentration is 98.2%, reaching 99.99% after drying.

[0105] Case 6:

[0106] Process water: temperature 40°C, flow rate 13000kg / h;

[0107] Steam: 7 bar saturated steam, flow rate 270 kg / h;

[0108] Condenser 2: The cooling medium is 20℃ desalted water, and the non-condensable steam temperature is 40℃;

[0109] Mixed gas: SO 2 Flow rate 5400kg / h, HCl flow rate 3000kg / h;

[0110] Filler: Ceramic filler, the upper filler layer 121 is 6 meters high and 1.8 meters in diameter, and the lower filler layer 122 is 2 meters high and 1 meter in diameter;

[0111] The tower bottom liquid level is controlled at 50%, and the reflux rate is 1300kg / h;

[0112] In this case, the mass concentration of hydrogen chloride in the recovered hydrochloric acid extracted from the bottom of the tower is 20.5%, SO 2 The mass concentration is 1.62%; SO in the non-condensable steam produced by the partial condenser 2 2 The mass concentration is 98.2%, reaching 99.99% after drying.

[0113] The embodiments described above are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solution of the present invention by ordinary technicians in the field, including the application of the present invention in other mixed gases, should all fall within the scope of protection determined by the claims of the present invention.

Claims

1. A method for separating a mixed gas of hydrogen chloride and sulfur dioxide, characterized in that: The separation method adopts a separation system comprising an absorption tower (1), a partial condenser (2), and a production pump (4); The side feed port of the absorption tower (1) is in communication with the mixed gas feed pipe (52); The top extraction port of the absorption tower (1) is connected to the feed port of the partial condenser (2) via the top extraction pipe (53); the condensate outlet of the partial condenser (2) is connected to the top feed port of the absorption tower (1) via the condensate pipe (55); the non-condensable steam outlet of the partial condenser (2) is connected to the sulfur dioxide discharge pipe (54); The kettle liquid extraction port of the absorption tower (1) is connected to the liquid inlet of the extraction pump (4) through the kettle liquid extraction pipe (581), and the liquid outlet of the extraction pump (4) is connected to the tower top feed port of the absorption tower (1) through the pump rear pipe (582); The bottom of the absorption tower (1) is connected to a steam feed pipe (51), and the steam feed port is arranged above the liquid level of the bottom of the tower; A reflux control valve (35) is provided on the rear pipe (582) of the pump, a hydrochloric acid outlet is provided in front of the reflux control valve (35), and the hydrochloric acid outlet is connected to the hydrochloric acid outlet pipe (57); a process water feed port is provided after the reflux control valve (35), and the process water feed port is connected to the process water feed pipe (561); During operation, part of the recovered hydrochloric acid produced from the bottom of the tower does not pass through other containers, but flows back to the top of the tower directly and continuously, and then flows down from the top of the tower after being mixed with process water to form dilute hydrochloric acid, so as to inhibit the transfer of sulfur dioxide to the liquid phase; the rest of the recovered hydrochloric acid is produced as a liquid phase product; the recovered hydrochloric acid produced does not pass through other containers, but leaves the device directly and continuously; The refluxed recycled hydrochloric acid should not be directly injected into the tower, but should be mixed with process water first, and the mass fraction of hydrogen chloride after mixing with process water should be less than 20%, otherwise part of the hydrogen chloride in the liquid phase at the top of the tower will volatilize into the gas phase and pollute the gas phase product; The absorption tower (1) is operated at normal pressure, the liquid phase temperature in the tower at the height of the mixed gas feed inlet is not lower than 100°C, and the steam feed temperature is not lower than 110°C.

2. The method for separating a mixture of hydrogen chloride and sulfur dioxide according to claim 1, characterized in that: The absorption tower (1) is a packed tower, wherein the packing layer of the packed tower is divided into two sections, including an upper packing layer (121) and a lower packing layer (122), and the mixed gas feed pipe (52) is connected to a side line feed port located between the upper packing layer (121) and the lower packing layer (122) on the packed tower shell.

3. The method for separating a mixed gas of hydrogen chloride and sulfur dioxide according to claim 2, characterized in that: The packed tower is a variable diameter tower, wherein the diameter of the lower section is smaller than that of the upper section; the upper section packing layer (121) is entirely arranged in the upper section tower body, the lower section packing layer (122) is entirely arranged in the lower section tower body, and the filling height of the lower section packing layer (122) is smaller than that of the upper section packing layer (121).

4. A method for separating a mixed gas of hydrogen chloride and sulfur dioxide according to any one of claims 1 to 3, characterized in that: The steam feed pipe (51) is provided with a steam feed valve (31), the mixed gas feed pipe (52) is provided with a mixed gas feed valve (32), the tower top extraction pipe (53) is provided with a tower top extraction valve (33), the kettle liquid extraction pipe (581) is provided with a tower kettle extraction valve (37), the process water feed pipe (561) is provided with a process water feed valve (341), and the hydrochloric acid discharge pipe (57) is provided with a hydrochloric acid discharge valve (36).

5. The method for separating a mixed gas of hydrogen chloride and sulfur dioxide according to claim 4, characterized in that: The process water feed pipe (561) is connected to the acid replenishing pipe (562), and the acid replenishing pipe (562) is provided with an acid replenishing valve (342).

6. The method for separating a mixed gas of hydrogen chloride and sulfur dioxide according to claim 1, characterized in that: The mixed gas is subjected to countercurrent absorption in an absorption tower (1), sulfur dioxide gas is extracted from the top of the tower, and hydrochloric acid is extracted and recovered from the bottom of the tower; The mixed gas is fed into the absorption tower (1) at the side line, and steam is directly fed into the tower kettle, and the steam feeding position is higher than the maximum liquid level allowed in the tower kettle; the steam fed into the tower kettle dilutes and heats the gas phase in the tower below the mixed gas feed inlet, and strips the liquid phase in the tower below the mixed gas feed inlet; The gas phase extracted from the top of the tower is condensed and dehumidified in the partial condenser (2), and the condensate is returned to the top of the tower, and all the non-condensable steam is extracted; Part of the recovered hydrochloric acid extracted from the tower bottom is refluxed to the top of the tower to inhibit the dissolution of sulfur dioxide in the mixed gas; The sum of the mass flow rates of process water and steam shall not be less than 1.7 times the mass flow rate of hydrogen chloride in the mixed gas; During the start-up of the separation system, the kettle liquid reflux rate is set to 0, all the kettle liquid extracted from the tower kettle is extracted as waste liquid, and hydrochloric acid with the same mass flow rate and acidity as the recovered hydrochloric acid refluxed during normal production is added to the process water.

7. The method for separating a mixed gas of hydrogen chloride and sulfur dioxide according to claim 6, characterized in that: The process includes: Step 1, mixed gas absorption: the mixed gas is fed from the side feed port of the absorption tower (1) and flows upward, and is countercurrently contacted with the dilute acid flowing down from the top of the tower, and the mixed gas removes hydrogen chloride and becomes sulfur dioxide gas containing a certain amount of water, which is extracted from the top of the tower and enters the partial condenser (2); the dilute acid absorbs the hydrogen chloride and a small amount of sulfur dioxide in the mixed gas and becomes recovered hydrochloric acid, which is heated and continues to flow downward; Step 2, sulfur dioxide condensation and dehumidification: the sulfur dioxide gas containing a certain amount of water extracted from the top of the tower is condensed in the partial condenser (2), the hydrochloric acid mist and most of the water enter the condensate and are returned to the top of the absorption tower (1), and the sulfur dioxide gas is extracted as a gas phase product from the non-condensable steam outlet of the partial condenser (2); Step 3, stripping of recovered hydrochloric acid: in the tower section of the absorption tower (1) located below the mixed gas feed port, the recovered hydrochloric acid is countercurrently contacted with the steam introduced into the tower bottom, and part of the sulfur dioxide in the recovered hydrochloric acid enters the steam; the steam flows upward and merges into the mixed gas, and the recovered hydrochloric acid flows into the tower bottom and is extracted from the bottom liquid extraction port; Step 4, kettle liquid reflux: the partially recovered hydrochloric acid extracted from the tower kettle is mixed with process water to form dilute hydrochloric acid and then refluxed to the top of the absorption tower (1); The remaining recovered hydrochloric acid is produced as a liquid product.

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