KR100821133B1 - Removal method of sodium cyanide in the sea oji refining process - Google Patents

Abstract

The present invention relates to a method for removing sodium cyanide in a COG purification process, which absorbs and purifies hydrogen sulfide (H₂S) in COG, oxidizes and regenerates in a regeneration tower, and dissolves the free sulfur separated by an oxidative regeneration reaction through a free sulfur transfer tube. Moving to a first step; A second step of reacting the free sulfur transferred to the dissolution tank with caustic soda flowing from the caustic soda feed pipe to produce sodium polysulfide; The dissolving tank is a third step of dividing the dissolution tank discharge liquid, which is sodium polysulfide, in a predetermined ratio, and divides the buffer solution into a buffer solution and an absorption column solution, and distributes the solution to a buffer tank and an absorption tower; In the buffer tank, a fourth step of producing a reactant by reacting the buffer solution solution supplied from the dissolution tank and the solution that flows from the regeneration tower through the free sulfur uptake pipe, and moves the absorption tower buffer buffer solution, which is a reactant, to the absorption tower; The absorption column dissolution solution and absorption column buffer bath discharged to the absorption tower were transferred to the regeneration tower while reacting with sodium cyanide (NaCN) contaminant absorbed and purified by hydrogen cyanide (HCN), and the reductant was reacted with sodium cyanide in the regeneration tower. A fifth step of converting (NaCN) to rodan salt (NaSCN).

Absorption tower, regeneration tower, buffer tank, melting tank, free sulfur transfer pipe, sodium cyanide, sodium polysulfide, caustic soda

Description

The method for elimination of NaCN by COG purification process             

1 is a block diagram of a wet deoiling apparatus used in the impurity purification method in the COG purification process according to the prior art.

Figure 2 is a block diagram of a wet deoiling apparatus used in the method for removing sodium cyanide in the COG purification process of the present invention.

Figure 3 is a flow chart showing a method for removing sodium cyanide in the COG purification process according to the present invention.

           ** Description of the symbols for the main parts of the drawings **

1: Contaminant Transfer Pipe 1a: Dissolution Operation Contaminant

2: circulating purified liquid 3: free sulfur overflow pipe

4: buffer tank discharge liquid 5: dissolution tank discharge liquid

10: absorption tower 20: regeneration tower

21: circulating purified liquid cooler (Cooler) 30: buffer tank

40: dissolution tank 50: molten sulfur tank                 

100: free sulfur transfer pipe 200: absorption column solution

300: buffering solution lysis solution 400: absorption column buffer bath discharge liquid

500: caustic soda supply pipe

The present invention relates to a method for removing sodium cyanide (NaCN) in the process of absorbing and purifying impurities (H₂S, HCN) in COG (Coke Oven Gas), specifically, during oxidation and regeneration of the contaminated liquid in which impurities in COG are purified. The present invention relates to a method for removing sodium cyanide in a COG refining process that sends separated free sulfur (S) to a dissolution tank to improve sodium polysulfide production, thereby improving the efficiency of removal of highly toxic sodium cyanide.

Figure 1 shows the configuration of the wet de-oiling apparatus used in the impurity purification method in the COG purification process according to the prior art, looking at the impurity purification method in the COG purification process as follows.

In the conventional wet desulfurization facility, as shown in FIG. 1, the absorption tower 10 and the regeneration tower 20 are converted into caustic soda (NaOH) as a circulating purification solution 2 to absorb and purify impurities (H 2 S and HCN) in COG. , Buffer tank 30, dissolution tank 40, molten sulfur tank (Molten Sulfur Tank; 50), and removes impurities (H₂S, HCN) in COG by the following reaction, the process is largely hydrogen sulfide It is divided into hydrogen sulfide removal process for removing hydrogen cyanide and hydrogen cyanide removal process for removing hydrogen cyanide.

First, [Formula 1] to [Formula 3] shows the hydrogen sulfide (H₂S) removal process in the COG, absorbing hydrogen sulfide (H₂S) in the COG with the circulating purification solution (2) in the absorption tower 10 and again regeneration tower ( 20 shows the process of oxidative regeneration to use as circulating purification liquid (2).

NaOH + H₂S → NaHS + H₂O ............ (Absorbing reaction)

(자유황) ............. (재생반응)NaHS + ½O₂ + Catalyst → NaOH + S

(Free sulfur) ............. (regeneration reaction)

2NaHS + 2O₂ → Na₂S₂O₃ + H₂O ............. (side reaction)

In addition, the following [Formula 4] to [Formula 6] shows a hydrogen cyanide (HCN) removal process in the COG, regeneration tower of hydrogen cyanide (HCN) absorbed into the circulating purification solution (2) in the absorption tower (10) (20) shows a process for changing to harmless rodan salt (NaSCN).

NaOH + HCN → NaCN + H₂O ................... (Absorbing reaction)

2NaOH + H₂S + XS → Na₂S _{X + 1} + 2H₂O ........... (polyemulsification)

NaCN + Na₂S _{X + 1} → NaSCN + Na₂S _X .............

Accordingly, referring to FIG. 1, the impurity purification method in the COG purification process according to the prior art is as follows.

First, the COG supplied from the COG inlet comes into contact with the circulating purification liquid 2 injected through the upper injection nozzle of the absorption tower 10 in the HEILEX inside the absorption tower 10, whereby impurities (H₂S and HCN) in the COG are discharged. Absorption purification (absorption reaction).

Purified liquid (hereinafter, contaminated liquid) absorbing and purifying hydrogen sulfide (H₂S) impurities in COG in the absorption tower 10 is sent to the regeneration tower 20 through the contaminant transport pipe 1 and compressed in the regeneration tower 20. Oxidation and regeneration (regeneration) by oxygen in the air and a catalyst is then carried to the absorption tower 10 and reused as the circulating purification liquid 2 in the absorption tower 10. At this time, in order to remove the reaction heat generated during the oxidation and regeneration the circulating purification liquid cooler (Cooler) 21 to remove the reaction heat by supplying water to the upper portion of the absorption tower 10 at a predetermined temperature (40 ℃ or less), repeating this process As a result, impurities in the COG are removed.

Meanwhile, in order to remove sodium cyanide from the contaminant obtained by absorbing and purifying hydrogen cyanide (HCN) impurities in COG, the contaminant transport contaminant 1a is sent from the contaminant transport pipe 1 to the dissolution tank 40, and the dissolution tank 40 is used. Mixed with molten sulfur supplied from the molten sulfur tank 50 to the dissolution tank 40 to produce sodium polysulfate (Na₂S _{X + 1} ; polyemulsification reaction), and then the dissolution tank discharge liquid 4, which is the product, is buffered ( 30), and the buffer tank discharge liquid (4) is sent to the regeneration tower (20), and the poisonous sodium cyanide (NaCN) in the contaminated liquid absorbing hydrogen cyanide (HCN), which is an impurity in COG, is harmless to rhodan salt (NaSCN; Rodan). Oxidization reaction), and the surplus flow rate is circulated to the buffer tank (30) through the free sulfur overflow pipe (3) for constant water level management of the regeneration tower (20). Repeatedly performing such a process to absorb and purify the impurities in the COG, the concentration of the circulating purification liquid (2) in the system rises to send a certain amount of circulating purification liquid (2) to the wastewater treatment to treat the wastewater, circulating purification liquid (2 The shortage of) is to supplement the fresh water and caustic soda into the absorption tower 10 and the contaminant transport pipe (1), respectively, to operate the facility.

However, even when molten sulfur is supplied from the molten sulfur tank 50 to the melting tank 40 at a temperature of 115 ° C. in the conventional method, the molten sulfur solidifies the instant of contact with the cold solution (40 ° C. or lower) inside the melting tank 40. As it is not dissolved, the utilization rate is very low and the removal rate of sodium cyanide (NaCN) of high toxicity is low. This can be seen as the concentration of rhodan salt collected and analyzed in the pipeline for circulating purified liquid (2) to be sent to the wastewater treatment.

In addition, the free sulfur accumulated in the buffer tank 30 through the free sulfur overflow pipe 3 accumulates and the free sulfur concentration is increased. ), The operation of the facility is not possible due to the generation of sulfur bubbles during oxidation and regeneration by compressed air.

Therefore, the present invention was devised to solve the problems of the prior art as described above, after the free sulfur (S) separated during oxidation and regeneration in the regeneration tower to produce a sodium polysulfide (Na₂S _{X + 1} ) The discharging tank discharged from the dissolution tank is divided into two parts of the absorption tower and the buffer tank, and the flow rate is controlled. In the buffer tank, the buffer solution dissolved in the dissolution tank and the solution flowing through the free sulfur transfer pipe are mixed into the absorption tower. It is an object of the present invention to provide a method for removing sodium cyanide in a COG refining process that improves the removal rate of sodium cyanide in a contaminated solution obtained by absorbing and purifying hydrogen cyanide in COG by supplying.

Another object of the present invention is to send the free sulfur separated during the oxidation and regeneration in the regeneration tower to produce a sodium polysulfide (Na₂S _{X + 1} ) and then supply to the absorption tower absorbed and purified hydrogen cyanide produced sodium cyanide contamination It is an object of the present invention to provide a method for removing sodium cyanide in a COG refining process to improve the removal rate of sodium cyanide by converting sodium cyanide into harmless rhodan salt by moving to a regeneration tower while reacting with a resonant.

Sodium cyanide removal method in the COG purification process of the present invention for achieving this object, the first step of moving the free sulfur separated by the oxidation and regeneration reaction to the dissolution tank through a free sulfur transfer pipe; A second step of reacting the free sulfur transferred to the dissolution tank with caustic soda flowing from the caustic soda feed pipe to produce sodium polysulfide; The dissolving tank is a third step of dividing the dissolution tank discharge liquid, which is polysodium sulfide, in a predetermined ratio, and divides the buffer solution into a buffer solution and an absorption column solution, and distributes the solution to a buffer tank and an absorption tower; In the buffer tank, a fourth step of producing a reactant by reacting the buffer solution solution supplied from the dissolution tank and the solution that flows from the regeneration tower through the free sulfur uptake pipe, and moves the absorption tower buffer buffer solution, which is a reactant, to the absorption tower; The absorption column dissolution solution and absorption column buffer bath discharged to the absorption tower were transferred to the regeneration tower while reacting with sodium cyanide (NaCN) contaminant absorbed and purified by hydrogen cyanide (HCN), and the reductant was reacted with sodium cyanide in the regeneration tower. And a fifth step of converting (NaCN) to rodanol (NaSCN).

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Figure 2 shows the configuration of the wet deoiling apparatus used in the sodium cyanide removal method in the COG purification process of the present invention, Figure 3 shows a sodium cyanide removal method in the COG purification process according to the present invention.

Looking at the method for removing sodium cyanide in the COG purification process according to the present invention with reference to Figures 2 to 3 as follows.

First, when COG (Coke Oven Gas) is introduced from the bottom of the absorption tower 10, the contact with the circulating purification liquid (2) that is injected through the upper injection nozzle of the absorption tower 10 in the absorption (Heilex) inside the absorption tower (10). As a result, impurities (H2S and HCN) in COG are absorbed and purified (absorption reaction) (S10 and S20).

The contaminant obtained by absorbing and purifying impurities (H₂S and HCN) in COG in the absorption tower 10 is sent to the regeneration tower 20 through the contaminant transport pipe 1, and hydrogen sulfide impurities (H₂S) in the contaminant are transferred. The contaminated liquid that has been absorbed and purified is oxidized and regenerated by oxygen in the compressed air in the regeneration tower 20 and a catalyst supplied out of the system and then moved to the absorption tower 10 and reused as the circulating purification liquid 2 in the absorption tower 10. It becomes (S30). By repeating this oxidative regeneration process, impurities in COG are removed. At this time, in order to remove the reaction heat generated during the oxidation and regeneration the circulating purification liquid cooler (Cooler) 21 to remove the heat of reaction by supplying water to the upper portion of the absorption tower 10 at a predetermined temperature (40 ℃ or less).

On the other hand, the process of removing the contaminated liquid absorbed and purified by hydrogen cyanide impurities (HCN) sent from the absorption tower 10 to the regeneration tower 20 in the above process, in the contaminated liquid absorbed and purified hydrogen cyanide in COG 10 m3 / hr of free sulfur separated during the oxidation and regeneration in the regeneration tower 20 through the free sulfur transfer pipe 100 branched from the free sulfur overflow pipe 3 to remove sodium cyanide from the dissolution tank 40 Mixing with the caustic soda supplied through the caustic soda supply pipe 500 in (40) to increase the alkalinity to produce sodium polysulfide (Na₂S _{X + 1} ) and then the buffer bath liquid ratio (dissolution tank) of the product dissolution tank discharge (5) The ratio of the amount of buffer solution dissolved liquid (300) to the amount of discharge liquid (5), that is, the buffer solution solution dissolved in solution / dissolution tank) is 0.6 to 0.4, and is divided into two parts of the buffer tank 30 and the absorption tower 10. (S40 to S50).

At this time, when the flow rate of the free sulfur transfer pipe 100 is less than 10 ㎥ / hr, the concentration of rodan salt is low and the sodium cyanide removal rate is low. Thus, the free sulfur concentration increases in the circulating purification liquid and foaming occurs. When the flow rate of the transfer pipe 100 is more than 10 ㎥ / hr, the rodan salt concentration increases (sodium cyanide removal rate is high), so that the side reaction proceeds, the chemical cost increases and the operating cost increases.

In addition, when the buffer tank separation ratio is higher than 0.6, the utilization rate of free sulfur is low, so that the concentration of rhodan salt is low, and when the buffer tank separation ratio is lower than 0.4, the concentration of rhodan salt rises and a side reaction proceeds, thereby increasing the drug cost.

On the other hand, the buffer bath solution 300 supplied from the dissolution tank 40 to the buffer tank 30 is separated during the oxidation and regeneration in the regeneration tower 20 and mixed with the solution that is overflowed through the free sulfur uptake pipe (3) Absorption column buffer tank discharge liquid 400 as a product is supplied to the bottom of the absorption tower (10) (S60).

As described above, in the absorption tower 10 supplied with the absorption tower dissolving liquid 200 and the absorption tower buffer discharging liquid 400, which are the discharging tank discharge liquid 5 which is transferred to the absorption tower 10, it is introduced from the COG inlet. Absorption and purification of hydrogen cyanide in the COG is sent to the regeneration tower 20 through the contaminant transport pipe 1 while reacting with the high concentration of the sodium cyanide, and thus the absorption tower 10 and the regeneration tower 20. ), The reaction time (15 ~ 16 minutes) is secured enough to secure the time to react sodium cyanide with rhodan salt, so the rhodium salt concentration is 60 ~ 70 g / l (S70 ~ S80). At this time, the reason for sending the solution to the regeneration tower 20 is to maintain the sufficient reaction time to keep the reaction time 15 to 16 minutes in the absorption tower 10 and the regeneration tower 20.

When the concentration of the circulating purification liquid 2 in the system is increased by repeatedly performing this process, a predetermined amount of circulating purification liquid 2 is sent to the wastewater treatment to treat the wastewater as in the prior art, and the deficiency of the circulating purification liquid 2 is absorbed in the absorption tower. Replenish fresh water with (10).                     

The reason why the concentration of rhodan salt is controlled at 60 to 70 g / l as above is that when the concentration of rhodan salt is less than 60 g / l, the free sulfur concentration in the circulating purification liquid (2) in the system rises and foaming occurs. This is because the concentration of sodium cyanide in the circulating refining liquid (2) is high, which causes disturbances in wastewater treatment. In addition, when the concentration of rhodan salt is 70g / l or more side reactions proceed to increase the drug costs.

Hereinafter, impurities (H₂S, HCN) removal process in COG according to the present invention is largely divided into hydrogen sulfide (H₂S) removal process and hydrogen cyanide (HCN) removal process, it is generally used [Formula 1] to [Formula 6] Based on the following.

First, [Formula 1] to [Formula 3] shows the hydrogen sulfide removal process in COG, in the absorption reaction of [Formula 1] sodium hydroxide (NaOH) regenerated in the regeneration tower 20 and hydrogen sulfide (H₂S introduced from COG) ) Reacts to produce sodium hydrogen sulfide (NaHS) and water (H₂O).

In the regeneration reactions of [Formula 2] to [Formula 3], sodium hydrogen sulfide (NaHS) produced by the absorption reaction, external compressed air (½O₂), and a catalyst react with sodium hydroxide (NaOH) and free sulfur (S). . Here, a side reaction of sodium hydrogen sulfide (NaHS) and oxygen (2O₂) is combined to produce sodium trioxide (Na₂S₂O₃) and water (H₂O).

[Formula 4] to [Formula 6] shows the hydrogen cyanide removal process in the COG, in the absorption reaction of [Formula 4] sodium cyanide (NaOH) regenerated in the regeneration tower 20 is hydrogen cyanide (HCN) introduced from the COG ) Is combined with sodium cyanide (NaCN) and water (H₂O).                     

The polyemulsification in the following Chemical Formula 5b combines sodium hydroxide (NaOH) and free sulfur (S) generated in the regeneration tower 20 in the dissolution tank 40 to produce sodium polysulphate (Na₂S _{X + 1} ). .

Na₂S _X + S → Na₂S _{X + 1} ........................ (Polymulsification)

At this time, the product dissolution tank discharge liquid (5) to the buffer tank 30 and the absorption tower (10) in a buffer tank liquid ratio (ratio of the buffer solution solution 300 to the amount of the dissolution tank discharge liquid) of 0.6 ~ 0.4. It will be divided and supplied. Thereafter, the sodium polysulfide (Na₂S _{X + 1} ) moved to the buffer tank 30 is moved to the absorption tower 10.

In the chemical formula [6], the rhodanization reaction is discharged from the dissolution tank 100 and moved in the sodium polyhydride (Na₂S _{X + 1} ) and the buffer tank 30 which are discharged liquids 5 moved to the absorption tower 10. Sodium emulsion (Na₂S _{X + 1} ) is reacted with sodium cyanide (NaCN) generated by absorption and purification of hydrogen cyanide (HCN) introduced from the COG inlet by absorption reaction, and then moves to the regeneration tower (20). ), Sodium cyanide (NaCN) is converted to harmless rhodan salt (NaSCN).

Hereinafter, the present invention will be described in detail with reference to comparative examples and examples.                     

[Comparative Example]

Comparative Example shows the experimental value using the impurity purification method according to the prior art, it can be seen that in the conventional method, the concentration of free sulfur in the system and the concentration of rhodan salt is lower than when using the sodium cyanide removal method of the present invention. This indicates that the sodium cyanide removal rate is low.

In addition, it can be seen that the reaction time required to remove sodium cyanide is considerably shorter than 15 to 16 minutes of the present invention.

Example 1

It can be seen that the concentration of rhodan salt changes as the flow rate of the free sulfur transfer pipe 100 changes. If the flow rate of the free sulfur transfer pipe 100 is small, the sulfur concentration required for the production of sodium polysulfide is insufficient. If the low (sodium cyanide removal rate is low) and the flow rate of the free sulfur transfer pipe 200 is high, the concentration of the rodan salt is increased (sodium cyanide removal rate is high), it can be seen that the chemical cost increases. It is shown that the flow rate of the free sulfur transfer pipe 100 is 10 m 3 / hr, and the concentration of rodan salt is in the range, and the concentration of liposulfur in the circulating purification liquid 2 is kept constant.

Example 2

When the flow rate of the free sulfur transfer pipe 100 is constant at 10 m 3 / hr, as the buffer tank liquid ratio (buffer solution solution flow rate / dissolution tank discharge flow rate) increases, rhodan salt concentration is lower (lower sodium cyanide removal rate), and buffering. The lower the crude fraction, the higher the concentration of rhodan salt (the higher the sodium cyanide removal rate), and the higher the drug ratio. In particular, the buffer bath ratio is 0.6 ~ 0.4 to show that the free sulfur concentration is kept constant and within the range of rodan salt concentration.

Example 3

The flow rate of the free sulfur transfer pipe 100 is constant at 10㎥ / hr, the buffer bath liquid ratio is 0.6-0.4, and the concentration of free sulfur in the system is constant and the rhodan salt concentration is kept constant within the range (sodium cyanide removal rate is high). In particular, it can be seen that the concentration of rhodan salt is best maintained when the buffer separation ratio is 0.5.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention is not limited to the contents described in the accompanying drawings and the detailed description of the specification.

As described above, according to the present invention, sodium polysulfide is produced using free sulfur separated during oxidation and regeneration in a regeneration tower without the need for adding molten sulfur as a separate facility, thereby increasing the efficiency of removing sodium cyanide in the circulating filtration solution. At the same time, the free sulfur concentration in the circulating purification liquid can be kept constant low, thereby having an excellent effect of preventing foaming.

Claims (5)

In the method for absorbing and purifying impurities (H₂S, HCN) in COG, Absorbs and purifies hydrogen sulfide (H₂S) in the COG, and oxidized and regenerated in the regeneration tower 20, the agent for moving the free sulfur separated by the oxidation and regeneration reaction to the dissolution tank 40 through the free sulfur transfer pipe 100. Stage 1; A second step of reacting the free sulfur transferred to the dissolution tank 40 with caustic soda flowing from the caustic soda supply pipe 500 to produce sodium polysulfide (Na₂S _{X + 1)} ; The dissolution tank 40 is divided into a buffer tank dissolution liquid 300 and the absorption tower dissolution liquid 200 by adjusting the amount of the dissolution tank discharge liquid 5, which is sodium polysulfide, at a set ratio, the buffer tank 30 and the absorption tower ( 10) distributing to; In the buffer tank 30 reacts the buffer solution flow solution 300 supplied from the dissolution tank 40 and the solution flowing through the free sulfur flow pipe (3) from the regeneration tower 20 to produce a reactant, A fourth step of moving the reactant absorption column buffer tank discharge liquid 400 to the absorption tower 10; The absorption tower dissolution solution 200 and the absorption tower buffer bath solution 400 supplied to the absorption tower 10 were reacted with sodium cyanide (NaCN) contaminant absorbed and purified by hydrogen cyanide (HCN) while regeneration tower ( 20), and a method for removing sodium cyanide in the COG purification process, comprising a fifth step of changing the sodium cyanide (NaCN) to the rhodium salt (NaSCN) by subjecting it to a rotamation reaction in the regeneration tower (20). . The method of claim 1, wherein in the first step, in the COG refining process, the flow rate of free sulfur moved to the dissolution tank 40 through the free sulfur transfer pipe 100 is adjusted to 10 ㎥ / hr How to remove sodium cyanide. The method of claim 1, wherein in the third step, the ratio of the dissolution tank discharge liquid 5 distributed to the buffer tank 30 and the absorption tower 10 is equal to the buffer tank liquid ratio (the amount of buffer operation solution dissolved in the dissolution tank discharge liquid amount). Sodium cyanide removal method in the COG purification process characterized in that the b) is adjusted to 0.6 ~ 0.4. [Claim 2] The COG of claim 1, wherein in the fifth step, the rhonetization reaction is controlled to be performed for 15 to 16 minutes while passing through the absorption tower 10 and the regeneration tower 20. Method for removing sodium cyanide in the purification process. According to claim 1, Sodium cyanide (NaCN) in the fifth step, sodium cyanide removal in the COG purification process, characterized in that the hydrogen cyanide (HCN) introduced from the COG inlet by absorption absorption purification produced by Way.

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