KR20230131521A - Method for producing chlorine - Google Patents

Abstract

The present invention relates to a method for producing chlorine that improves process efficiency by reusing oxygen emitted during the production of chlorine by oxidizing hydrogen chloride.

Description

Method for producing chlorine {METHOD FOR PRODUCING CHLORINE}

The present invention relates to a method for producing chlorine, and relates to a method for producing chlorine that improves process efficiency by reusing oxygen emitted when producing chlorine by oxidizing hydrogen chloride.

Chlorine is used as a raw material for vinyl chloride, phosgene, etc. Methods for producing chlorine include salt electrolysis or catalytic oxidation of hydrogen chloride. Among them, the salt electrolysis method has a disadvantage in terms of energy efficiency because it uses relatively large amounts of power. On the other hand, the production of chlorine through oxidation of hydrogen chloride is useful in that hydrogen chloride generated as a by-product in various reactions can be used. Typically, a large amount of hydrogen chloride can be obtained as a co-product through the production of isocyanate or chlorination reaction of aromatic compounds.

Meanwhile, hydrogen chloride obtained as a co-product in the production of the isocyanate is gaseous hydrogen chloride. Gas-phase hydrogen chloride is produced into chlorine in an oxidation reactor using an excess of oxygen, and the produced chlorine can then be obtained through condensation. At this time, in order to condense chlorine from the gaseous product, it is preferable to proceed at high pressure and low temperature. However, unreacted oxygen added in excess and inert gas components such as carbon dioxide accompanied with hydrogen chloride in the production of isocyanate are not condensed and remain.

In terms of process efficiency, it is preferable to recycle unreacted oxygen that is not condensed and exists in the gas phase to the hydrogen chloride oxidation reactor and reuse it for oxidation of hydrogen chloride. At this time, in order to continuously reuse oxygen for oxidation of hydrogen chloride, it is necessary to prevent the accumulation of carbon dioxide as described above to increase the efficiency of the reactor and prevent the scale of the entire process from being enlarged. Previously, a technology was proposed to proceed with the oxidation reaction of hydrogen chloride by removing carbon dioxide in advance, but there was a problem in that an additional process that consumed a lot of energy was needed to remove carbon dioxide.

Accordingly, in the chlorine production process, there is a need to develop a method that can efficiently separate carbon dioxide to increase the reuse of oxygen.

The present invention seeks to provide a method for producing chlorine that efficiently reuses unreacted oxygen by removing carbon dioxide as an impurity during the process of producing chlorine from hydrogen chloride.

In order to solve the above problem, the present invention includes the steps of producing chlorine by reacting a gas mixture containing hydrogen chloride with oxygen in the presence of a catalyst in a fixed bed reactor (step 1); Absorbing unreacted hydrogen chloride in water in a hydrochloric acid absorption tower to remove it in the form of hydrochloric acid, and separating a gaseous product containing chlorine and unreacted oxygen (step 2); Drying the gaseous product that passed step 2 in a drying tower (step 3); Purifying chlorine from the dried gaseous product and recycling unreacted oxygen to step 1 (step 4); and purifying remaining unreacted oxygen (step 5); wherein the gas mixture of step 1 contains at least carbon dioxide, carbon dioxide is removed using an aqueous caustic soda solution in step 5, and A method for producing chlorine is provided, comprising the step of reintroducing gaseous material containing residual unreacted oxygen to step 3.

In the present invention, terms such as first and second are used to describe various components, and the terms are used only for the purpose of distinguishing one component from another component.

Additionally, the terminology used herein is only used to describe exemplary embodiments and is not intended to limit the invention.

Singular expressions include plural expressions unless the context clearly dictates otherwise.

In this specification, terms such as “comprise,” “comprise,” or “have” are used to describe implemented features, numbers, steps, components, or combinations thereof, and include one or more other features or numbers, The possibility of steps, components, combinations or additions thereof is not excluded.

Additionally, in this specification, when each layer or element is referred to as being formed “on” or “on” the respective layers or elements, it means that each layer or element is formed directly on the respective layers or elements, or other This means that layers or elements can be additionally formed between each layer, on the object, or on the substrate.

Since the present invention can be subject to various changes and can take various forms, specific embodiments will be illustrated and described in detail below. However, this does not limit the present invention to the specific disclosed form, and should be understood to include all changes, equivalents, and substitutes included in the spirit and technical scope of the present invention.

The present invention relates to a method for producing chlorine, which includes removing carbon dioxide contained in some unreacted oxygen using caustic soda during the chlorine production process and adding it to a drying tower.

According to the method for producing chlorine of the present invention, carbon dioxide is appropriately removed using caustic soda during the chlorine production process, thereby preventing concentration of carbon dioxide and enabling additional reuse of oxygen without a separate carbon dioxide removal process, thereby reducing oxygen usage. You can. In addition, the water generated in the process of removing carbon dioxide using caustic soda can be removed in the drying tower, which is excellent in terms of process efficiency.

Hereinafter, the present invention will be described in detail at each step.

(Step 1)

Step 1 is a step of producing chlorine by reacting a gas mixture containing hydrogen chloride with oxygen in a fixed bed reactor.

The hydrogen chloride can be obtained as a by-product through the synthesis of isocyanates, which are mainly produced by reacting phosgene and amine. In addition, it can be obtained from acid chloride production, polycarbonate production, vinyl chloride production, chlorination of aromatic compounds, etc. At this time, during the manufacturing process, not only hydrogen chloride but also carbon dioxide is produced along with it. Therefore, in this reaction step, a gas mixture containing hydrogen chloride is used as a reaction raw material.

In addition, in the present invention, oxygen is introduced separately from the gas mixture containing hydrogen chloride, and chlorine is produced through a reaction between hydrogen chloride and oxygen contained in the gas mixture. The amount of oxygen introduced can be adjusted depending on the amount of hydrogen chloride, the reactor, and the equipment applied in the post-process, and is usually 1:1 to 20:1, preferably 2:1 to 8:1, or 2:1 to 2:1. It is 5:1.

In addition, the step of producing chlorine through the oxidation reaction of hydrogen chloride is preferably performed in the presence of a catalyst. There is no particular limitation on the catalyst that can be used in this reaction, but it may include one or more selected from the group consisting of ceria, alumina, copper oxide, ruthenium oxide, and silica. Additionally, they can be used in the form of being supported on a carrier, and the carrier that can be used may include one or more types selected from silica, alumina, titania, and zirconia, but is not particularly limited thereto.

In addition, the catalyst may be manufactured using a common catalyst preparation method such as coprecipitation or impregnation. The catalyst may be used in the form of powder, particles, or molded bodies, and the formed bodies may be pellet-shaped or ring-shaped. It may have a shape, a cylindrical shape, a star shape, a wheel shape, or a sphere.

Preferably, the amount of catalyst used in step 1 is defined by the space velocity of the gas mixture introduced into the reactor, and the space velocity of the gas mixture is operated at 300 hr ^-1 to 1500 hr ^-1 . If the space velocity is less than 300 hr ^-1 , catalyst deactivation may be accelerated by operating at a high temperature to achieve the desired conversion rate of hydrogen chloride, and if the space velocity is greater than 1500 hr ^-1 , the reactor becomes enlarged, which is economically disadvantageous. do. More preferably, the space velocity is 350 hr ^-1 or more, 400 hr ^-1 or more, or 450 hr ^-1 or more, and can be used as 1200 hr ^-1 or less, 1000 hr ^-1 or less, or 900 hr ^{-1 or} less. there is.

Preferably, step 1 may be carried out at 200 to 500 °C. The catalytic oxidation reaction of hydrogen chloride of the present invention is an exothermic reaction and an equilibrium reaction, and it is advantageous in terms of equilibrium conversion rate as it proceeds at a relatively low temperature, but if the temperature is too low, the reaction progress rate may be very slow. Therefore, proceeding in the above temperature range in the presence of a catalyst is superior in terms of reaction rate and equilibrium conversion rate. More preferably, step 1 may be carried out at 250 ℃ or higher, 270 ℃ or higher, 280 ℃ or higher, or 290 ℃ or lower, and at 450 ℃ or lower, 430 ℃ or lower, 420 ℃ or lower, or 400 ℃ or lower. In addition, Step 1 may be performed by controlling the initial reactor temperature and the latter reactor temperature, respectively, in consideration of catalyst activity and reaction equilibrium. In this case, the initial reactor temperature is 200 to 400 ℃, 250 to 350 ℃, or 300 to 320 ℃. , the later reactor temperature may be 300 to 450 °C, 320 to 425 °C, or 350 to 400 °C.

(Step 2)

Step 2 of the present invention is a step of removing the product from step 1 by absorbing hydrogen chloride in water in a hydrochloric acid absorption tower and separating the gaseous product containing chlorine and unreacted oxygen.

Specifically, step 2 of the present invention is a step of separating a gaseous product mainly composed of chlorine and unreacted oxygen from the reaction product mainly composed of chlorine, water, unreacted hydrogen chloride, and unreacted oxygen obtained in the reaction step. At this time, water and/or low-concentration hydrochloric acid water may be used as the absorbent, and by contacting the absorbent with the reaction product, hydrogen chloride and water are discharged to the bottom of the absorption tower in the form of hydrochloric acid, and chlorine and oxygen are contained to the top of the absorption tower. It emits gaseous products. Meanwhile, in this specification, the gaseous product containing chlorine and unreacted oxygen prepared through step 2 may be called “crude-chlorine gas.”

The form of the absorption tower that can be used in step 2 may be an appropriate form to facilitate contact between the reaction product and the absorbent water and/or hydrochloric acid, for example, a packed column, tray column, jet scrubber, or spray. Towers, or a mixture of these may be used.

Additionally, step 2 is carried out at 30 to 50° C. and 0.01 to 0.1 MPa. Preferably, step 2 is carried out at a temperature of 35 to 45 ℃, or 38 to 42 ℃, and a pressure of 0.05 to 0.9 MPa, or 0.07 to 0.8 MPa. Operating the absorption tower at the temperature and pressure in the above range can stably absorb hydrogen chloride into water and separate gaseous products.

Preferably, the concentration of hydrochloric acid discharged to the bottom of the absorption tower through step 2 is 20 to 35% by weight, 25 to 32% by weight, or 27 to 30% by weight. Using water as an absorbent to discharge hydrochloric acid with a concentration in the above range reduces the load on the drying process and purification process described later.

(Step 3)

Step 3 of the present invention is a step of drying the gaseous product discharged from the top of the hydrochloric acid absorption tower to remove moisture.

The gaseous product flowing from the hydrochloric acid absorption tower can flow into the lower part of one or more drying towers connected in series, and comes into contact with the sulfuric acid flowing into the upper part of each drying tower in a countercurrent flow to remove moisture. At this time, the drying tower may be a packing column, tray tower, spray tower, or a combination thereof.

Drying agents that can be used in step 3 include sulfuric acid, calcium chloride, magnesium perchlorate, or zeolite, and sulfuric acid is preferred because it is easy to discharge after use. In addition, the sulfuric acid may be 0.5 to 2.0% by weight, more preferably 0.7 to 1.5% by weight, or 1.0 to 1.3% by weight of the gaseous product introduced in step 3. When the concentration of sulfuric acid is used in the above range, moisture is easily removed from the gaseous product and sulfuric acid is easily discharged.

(Step 4)

Step 4 of the present invention is a step of purifying chlorine from the dried gaseous product and recycling unreacted oxygen to step 1. After the drying process, the gaseous product contains chlorine and unreacted oxygen, and the chlorine purification step is a step of separating and reusing a stream mainly containing chlorine and a stream mainly containing unreacted oxygen.

In the step of purifying chlorine, a gaseous product containing chlorine may be separated into a liquid stream containing chlorine as a main component and a gaseous stream containing unreacted oxygen as a main component through a compression and cooling process. Liquefaction of chlorine can be carried out within the range of temperature and pressure at which chlorine in the gaseous product can exist in a liquid state, but an appropriate range can be selected considering the economic efficiency of the equipment. Preferably, it may be carried out at -60 to -10 ℃ and 10 to 30 bar. More preferably, it may be carried out at a temperature of -50 to -20 ℃, -45 to -30 ℃, or -40 to -35 ℃, 15 bar or more, 17 bar or more, 19 bar or more, 25 bar or less, It can be carried out below 23 bar or below 21 bar.

Meanwhile, through the compression cooling process, the liquid stream containing chlorine as a main component may contain trace amounts of oxygen, carbon dioxide, and/or inert gas in addition to chlorine, which may optionally be subjected to additional chlorine purification such as flash and/or distillation. The process can be introduced.

In addition, the gaseous stream containing unreacted oxygen as a main component may contain trace amounts of carbon dioxide, chlorine, etc. in addition to oxygen. Preferably, a portion of the gaseous stream may be reused by inputting it into the reactor together with the gas mixture of step 1. The recycle ratio, defined as the mass of the gaseous stream recycled to Stage 1 relative to the total mass of the gaseous stream discharged to the top of the refinery tower in Stage 4 of the present invention, is 50 to 97%, 80 to 97%, or 90 to 97%. .

(Step 5)

Step 5 of the present invention is a step of purifying and recovering the remaining unreacted oxygen discharged without being recycled from Step 4 to Step 1. In order to recover unreacted oxygen, the reaction raw material and circulating carbon dioxide are purified and recovered using an aqueous caustic soda solution. This is a step to additionally recover unreacted oxygen while preventing the accumulation of carbon dioxide by removing it.

The existing method of producing chlorine through catalytic oxidation of hydrogen chloride was mainly carried out by purifying the reaction raw materials to remove carbon dioxide from the reaction raw materials and then introducing the reaction raw materials into the reactor to proceed with the reaction. In this case, additional equipment is needed to purify the reaction raw materials, and the raw material gas must be cooled and then heated again to the reaction conditions, which results in large energy consumption. Accordingly, the researchers of the present invention reduced the amount of carbon dioxide circulation in the process without separately removing carbon dioxide from the reaction raw materials through a chlorine production method that removes carbon dioxide using caustic soda in the step of recovering remaining unreacted oxygen. The present invention was completed by confirming that process efficiency can be increased by stably reusing oxygen.

The device used in the step of recovering the remaining unreacted oxygen may typically be a scrubbing column equipped with a scrubber. Specifically, a gaseous stream that has undergone a chlorine purification step, containing unreacted oxygen and carbon dioxide, is introduced into the lower part of the scrubbing column, and caustic soda is introduced into the upper part, so that the caustic soda and carbon dioxide come into contact within the scrubber, Carbon dioxide is converted to sodium bicarbonate, etc., which is dissolved in water and discharged as wastewater from the bottom of the scrubbing column. Meanwhile, a stream containing unreacted oxygen from which carbon dioxide has been removed is discharged to the top of the scrubbing column, and in consideration of the occurrence of equipment corrosion in contact with hydrogen chloride, the discharged unreacted oxygen is dried in step 3 rather than step 1. It is re-injected to remove some of the trace moisture contained therein.

In the step of reintroducing the gaseous material containing unreacted oxygen that has passed through step 5, the gaseous material and the gaseous product that have passed through step 2 can be mixed and added to the drying tower, or the gaseous material and the gaseous product can be added to the drying tower separately. , it is preferable to mix them and add them to the drying tower in terms of efficiency in removing moisture contained in the gaseous material.

Meanwhile, the gas mixture in step 1 contains 0.05 to 5 vol% of carbon dioxide. More preferably, the gas mixture of step 1 contains at least 0.06 vol%, at least 0.07 vol%, at least 0.08 vol%, at least 0.09 vol%, or at least 0.1 vol%, but at most 4 vol% and at most 3 vol%. , 2 vol% or less, or 1 vol% or less. As described above, carbon dioxide contained in the gas mixture corresponds to carbon dioxide accompanying the process of producing hydrogen chloride, which is a raw material.

In addition, the carbon dioxide contained in the gas mixture as a reactant is mixed/accumulated with the accompanying carbon dioxide during the process of recycling the gaseous material containing unreacted oxygen after going through step 4. Therefore, the total gaseous material substantially introduced into the reactor can be understood as a gaseous material mixed with a gas mixture including hydrogen chloride and carbon dioxide, oxygen, and a recycled stream. Preferably, the carbon dioxide introduced into the fixed bed reactor of step 1 is included in 5 to 20% by weight of the total gaseous materials introduced into the reactor. More preferably, the carbon dioxide introduced into the fixed bed reactor is 6% by weight, 6.5%, 7%, or 7.5% by weight of the total gaseous material, but is 19% by weight or less, 18% by weight, or 16% by weight. % or less, or 15% by weight or less.

Preferably, 50 to 90% by mass of the gaseous material stream containing unreacted oxygen that has passed through step 5 is reintroduced into step 3. More preferably, at least 55%, at least 60%, at least 70%, or at least 75%, and at most 87%, 85%, 83%, or 82% by mass of the gaseous material stream are re-incorporated in step 3. Put in. If the gaseous material stream is circulated below the above range, the process benefit from additional oxygen recovery may not be significant, and if the gaseous material stream is circulated above the above range, step 3 due to the accumulation of inert components (N ₂ , Ar, etc.) that cannot be removed. Problems may arise where the efficiency of the equipment decreases in the future.

Also, preferably, the gaseous material containing the remaining unreacted oxygen that has passed through step 5 may contain 10% or less of carbon dioxide. More preferably, the gaseous material may contain 5% or less, 3% or less, 1% or less, 0.5% or less, or 0.1% or less of carbon dioxide. If the carbon dioxide in the gaseous material containing unreacted oxygen that has gone through step 5 exceeds the above range, the amount of carbon dioxide circulating in the process cannot be reduced, which may cause the problem of equipment enlargement in the subsequent process. Meanwhile, the smaller the carbon dioxide concentration in the gaseous material that has passed step 5, the better, so the theoretical lower limit is 0, but for example, it may be 0.01% or more, 0.05% or more, or 0.07% or more. If the carbon dioxide in the gaseous material containing unreacted oxygen that has gone through step 5 is below the above range, the amount of wastewater generated may increase due to the use of an excessive amount of caustic soda to remove carbon dioxide.

Preferably, the aqueous caustic soda solution is a gaseous stream fed into step 5. It may be 200 to 500% by weight, more preferably 250% by weight or more, 300% by weight, or 350% by weight, but 470% by weight or less, 450% by weight or less, 430% by weight or less, or 420% by weight. It may be less than %. When caustic soda is used in the above range compared to gaseous stream, carbon dioxide reduction and wastewater discharge can be appropriately controlled.

Also, preferably, the concentration of the aqueous caustic soda solution added in step 5 may be 5 to 50% by weight, 6 to 40% by weight, 7 to 30% by weight, or 8 to 20% by weight. When the caustic soda is at the above concentration, it is possible to appropriately remove carbon dioxide in gaseous materials while suppressing deterioration of process stability due to the production of solids.

Hereinafter, with reference to the drawings, the method for producing chlorine according to an embodiment will be described in more detail for each step. Figure 2 shows a schematic diagram of a chlorine production device applied to the chlorine production method according to an embodiment of the present invention.

Referring to FIG. 2, the apparatus for the chlorine production method consists of a fixed bed reactor (1), a hydrochloric acid absorption tower (2), a drying tower (3), a chlorine purification tower (4), and an exhaust gas purification tower (5). It can be.

The fixed bed reactor 1 is a device in which an oxidation reaction of hydrogen chloride progresses, and may further include an external jacket for heat removal to control reaction heat.

The hydrochloric acid absorption tower (2) is a device that recovers hydrogen chloride and water and separates gaseous products containing chlorine and unreacted oxygen.

The drying tower (3) is a device that removes moisture contained in the gaseous product.

The chlorine purification tower (4) is a device that purifies chlorine and recycles unreacted oxygen.

The exhaust gas purification tower 5 is a device that removes carbon dioxide in gaseous materials containing residual unreacted oxygen, and recovers and recycles unreacted oxygen.

As an example, the method for producing chlorine of the present invention may proceed as follows. A gas mixture containing hydrogen chloride and at least carbon dioxide and oxygen are introduced into the fixed bed reactor (1) to produce chlorine in the presence of a catalyst. After completion of the reaction, the produced product is introduced into the hydrochloric acid absorption tower (2).

In the hydrochloric acid absorption tower (2), water is added to remove hydrogen chloride, and gaseous products containing chlorine and unreacted oxygen are separated. Hydrogen chloride is absorbed in water and discharged to the bottom of the absorption tower in the form of hydrochloric acid, and gaseous products containing chlorine and unreacted oxygen are discharged to the top of the absorption tower and input into the drying tower (3).

In the drying tower (3), the gaseous product is dried to remove moisture. As a drying agent, sulfuric acid may be used as described above. Additionally, the gaseous material containing residual unreacted oxygen that has passed through step 5 of the present invention can be introduced into the drying tower (3), and at this time, it can be mixed with the gaseous product that has gone through step 2 and then added. A desiccant, for example, sulfuric acid, is discharged from the bottom of the drying tower, and a gaseous product with moisture removed is discharged from the top of the drying tower and input into the chlorine purification tower (4).

In the chlorine purification tower (4), chlorine and other substances are separated, and chlorine is discharged to the bottom of the purification tower, and other substances are discharged to the top of the purification tower. The material discharged to the top includes unreacted oxygen and carbon dioxide contained in the reaction raw materials, some of which is input into the exhaust gas purification tower (5), and some of which is mixed with the reaction raw materials and recycled to the fixed bed reactor.

The exhaust gas purification tower 5 discharges gaseous substances containing residual unreacted oxygen to the upper part and waste water to the lower part. As described above, the gaseous material discharged to the top is reintroduced into the drying tower.

However, the position of each device in FIG. 2 can be changed, and other devices not shown in FIG. 2 can be included as needed, so the chlorine production method of the present invention is limited to the device and process sequence shown in FIG. 2. That is not the case.

As described above, the method for producing chlorine according to the present invention can increase process efficiency and economic feasibility by removing carbon dioxide contained in the reactant without a separate carbon dioxide removal device and further reusing unreacted oxygen.

Figure 1 is a schematic diagram schematically showing a conventional chlorine production device.
Figure 2 is a schematic diagram schematically showing a chlorine production device applied to a chlorine production method according to an embodiment of the invention.

Below, preferred embodiments are presented to aid understanding of the invention. However, the following examples are only for illustrating the present invention and do not limit the present invention to these only.

<Example>

Comparative example

Using the device shown in Figure 1, chlorine was produced through the following process.

(Step 1)

18479 kg/hr of hydrogen chloride, 4065 kg/hr of oxygen, 14093 kg/hr of unreacted recovered oxygen, and 5322 kg/hr of carbon dioxide were added to the reactor, and an oxidation reaction was performed at 315°C and 5 bar in the presence of a ruthenium oxide catalyst. The input temperature of the reaction raw materials was 290°C.

(Step 2)

The produced gas discharged from the reactor was cooled to 40° C. with a cooler and introduced into the hydrochloric acid absorption tower. 2762 kg/hr of water was injected into the top of the absorption tower. Hydrogen chloride was absorbed into water, and hydrochloric acid (30% by weight) was discharged from the bottom of the absorption tower, and a gaseous product containing chlorine and oxygen was discharged from the top. The gaseous substances emitted included 45% by weight chlorine, 35% by weight oxygen, and 15% by weight carbon dioxide.

(Step 3)

The gaseous material discharged from the absorption tower was put into a drying tower to remove moisture. Sulfuric acid was used as a drying agent, and sulfuric acid was added at 1.2% by weight (426 kg/hr) of the gaseous product input into the drying tower.

(Step 4)

The gaseous product from which moisture was removed was put into a chlorine purification tower to separate chlorine. The purification tower was operated at -37°C and 20 bar. Meanwhile, some of the gaseous substances discharged from the top of the chlorine purification tower were recirculated into the reactor (19146 kg/hr, recirculation ratio 95%), and some were input into the exhaust gas purification tower (986 kg/hr).

(Step 5)

The exhaust gas purification tower was operated at 15°C and 1 bar, and gaseous substances of oxygen and carbon dioxide and wastewater were separated and discharged.

Example

Using the device shown in Figure 2, chlorine was produced through the following process.

(Step 1)

18549 kg/hr of hydrogen chloride, 3650 kg/hr of oxygen, 17612 kg/hr of unreacted recovered oxygen, and 3592 kg/hr of carbon dioxide were added to the reactor, and an oxidation reaction was performed at 315°C and 5 bar in the presence of a ruthenium oxide catalyst. The input temperature of the reaction raw materials was 290°C.

(Step 2)

The produced gas discharged from the reactor was cooled to 40° C. with a cooler and introduced into the hydrochloric acid absorption tower. 2787 kg/hr of water was injected into the upper part of the absorption tower. Hydrogen chloride was absorbed into water, and hydrochloric acid (30% by weight) was discharged from the bottom of the absorption tower, and a gaseous product containing chlorine and oxygen was discharged from the top. The gaseous substances emitted included 44% by weight of chlorine, 33% by weight of oxygen, and 10% by weight of carbon dioxide.

(Step 3)

The gaseous material discharged from the absorption tower was put into a drying tower to remove moisture. Sulfuric acid was used as a drying agent, and sulfuric acid was added at 1.1% by weight (424 kg/hr) of the gaseous product input into the drying tower.

(Step 4)

The gaseous product from which moisture was removed was put into a chlorine purification tower to separate chlorine. The purification tower was operated at -37°C and 20 bar. Meanwhile, some of the gaseous substances discharged from the top of the chlorine purification tower were recycled to the reactor (20864 kg/hr, recirculation ratio 93%), and some were input into the exhaust gas purification tower (1586 kg/hr).

(Step 5)

The exhaust gas purification tower was operated at 15°C and 1 bar, and gaseous substances of oxygen and carbon dioxide and wastewater were separated and discharged.

After removing carbon dioxide in the gaseous material by injecting 6,315 kg/hr of 10% caustic soda solution into the top of the exhaust gas purification tower, the remaining unreacted oxygen is recovered, and 80% (974 kg/hr) of the gaseous material containing the remaining unreacted oxygen is removed. hr) was mixed with the gaseous product from step 2 and added to step 3.

The amounts of substances discharged from each device in the comparative examples and examples are listed in Table 1 below.

Comparative example Example sheep water sheep water kg/hr wt% kg/hr wt% hydrochloric acid production 9103.34 30.00 9137.78 30.00 Sulfuric acid production 643.12 65.00 700.79 65.00 goat production 15000 99.95 15000 99.95 Hydrogen chloride consumption 18478.67 98.54 18549.5 98.54 oxygen consumption 4065 99.70 3650 99.70 CO ₂ circulation amount in feed 5322.15 12.77 3592.37 8.31

As shown in Table 1, the chlorine production method of the example can stably remove carbon dioxide compared to the comparative example at the same level of hydrogen chloride consumption and chlorine production, thereby reducing the amount of CO ₂ circulation in the feed and stably recirculating oxygen. By doing so, oxygen consumption can be reduced and overall process efficiency can be improved.

1: Hydrogen chloride fixed bed oxidation reactor
2: Hydrochloric acid absorption tower
3: Sulfuric acid drying tower
4: Chlorine purification tower
5: Exhaust gas purification tower

Claims (14)

Producing chlorine by reacting a gas mixture containing hydrogen chloride with oxygen in the presence of a catalyst in a fixed bed reactor (step 1);
Absorbing unreacted hydrogen chloride in water in a hydrochloric acid absorption tower to remove it in the form of hydrochloric acid, and separating a gaseous product containing chlorine and unreacted oxygen (step 2);
Drying the gaseous product that passed step 2 in a drying tower (step 3);
Purifying chlorine from the dried gaseous product and recycling unreacted oxygen to step 1 (step 4); and
It includes a step of purifying remaining unreacted oxygen (step 5),
The gas mixture of step 1 contains at least carbon dioxide, carbon dioxide is removed using an aqueous caustic soda solution in step 5, and the gaseous material containing residual unreacted oxygen that has passed through step 5 is reintroduced into step 3. Including,
How to make chlorine.
According to paragraph 1,
The step of reintroducing the gaseous material that has gone through step 5 is mixing it with the gaseous product that has gone through step 2 and adding it to the drying tower.
How to make chlorine.
According to paragraph 1,
The catalyst of step 1 is any one selected from the group consisting of ceria, alumina, copper oxide, ruthenium oxide, and silica,
How to make chlorine.
According to paragraph 1,
Step 1 is carried out at 200 to 500 ° C.
How to make chlorine.
According to paragraph 1,
Step 2 is carried out at 30 to 50 ℃ and 0.01 to 0.1 MPa,
How to make chlorine.
According to paragraph 1,
Through step 2, the concentration of hydrochloric acid discharged to the bottom of the absorption tower is 20 to 35% by weight,
How to make chlorine.
According to paragraph 1,
Drying the gaseous product of step 3 uses sulfuric acid,
How to make chlorine.
In clause 7,
Sulfuric acid is 0.5 to 2.0% by weight of the gaseous product fed into step 3,
How to make chlorine.
According to paragraph 1,
Step 4 is carried out under -60 to -10 ℃ and 10 to 30 bar,
How to make chlorine.
According to paragraph 1,
Carbon dioxide introduced into the fixed bed reactor of step 1 is comprised of 5 to 15% by weight of the total gaseous material introduced into the reactor.
How to make chlorine.
According to paragraph 1,
Reintroducing 50 to 95% by mass of the gaseous material stream containing residual unreacted oxygen that has passed through step 5 into step 3,
How to make chlorine.
According to paragraph 1,
The gaseous material containing residual unreacted oxygen that has gone through step 5 contains less than 10% carbon dioxide,
How to make chlorine.
According to paragraph 1,
The caustic soda aqueous solution is 200 to 500% by weight relative to the gaseous stream introduced in step 5,
How to make chlorine.
According to paragraph 1,
The concentration of the caustic soda aqueous solution is 5 to 50% by weight,
How to make chlorine.