Method for preparing liquid hcn by ammonia oxidation and reaction gas absorption system

Abstract

The application discloses a method for preparing liquid HCN by an ammonia oxidation method and a reaction gas absorption system, and the preparation process is as follows: reaction gas is introduced into an absorption device to realize total absorption of HCN, NH3 and H2O, then the absorption rich solution is sent into a rectification device to realize resolution and rectification, liquid HCN and absorption lean solution are obtained, the liquid HCN is recovered, and part of the absorption lean solution is returned and mixed with sulfuric acid to form a sulfuric acid-containing solution. Compared with the existing process, the process method of the application realizes total absorption in one step, then liquid HCN is obtained by rectification, the process flow is short, the equipment is less, the investment is lower, the operation is more stable and safe, and the total energy consumption is lower.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of compound preparation, and relates to production of small-molecule compounds, in particular to a method for preparing liquid HCN by an ammoxidation method and a reaction gas absorption system. BACKGROUND

[0002] Hydrocyanic acid is an important chemical raw material and is widely used. Hydrocyanic acid is a highly toxic chemical and cannot be transported. The synthesis of hydrocyanic acid is matched with downstream products. Main synthesis methods of hydrocyanic acid include: propylene nitrile by-product method, natural gas ammoxidation method, light oil cracking method, methanol ammoxidation method, and formamide dehydration method.

[0003] The natural gas ammoxidation method for synthesizing HCN is mature, and accounts for the largest proportion of about 60% in the total amount of HCN synthesized in the world, and a single device reaches more than 100,000 tons / year. In China, the largest industrialization scale is more than 30,000 tons / year, and the economic and technical indicators of the most competitive hydrocyanic acid production method. The methanol ammoxidation method for synthesizing HCN has developed rapidly in China, with more than 30 production devices, the largest single capacity of 25,000 tons / year, and a total capacity of 300,000 tons / year. Due to the stable performance of the catalyst, the easy availability of methanol raw materials, the mild production conditions, and the high yield of hydrocyanic acid, it has obvious cost advantages and has become a relatively competitive method for producing hydrocyanic acid.

[0004] The natural gas ammoxidation method or the methanol ammoxidation method for synthesizing HCN has reaction gas containing HCN, NH3, H2O and inert gas. The existing method for preparing liquid HCN first uses sulfuric acid to remove ammonia to form an ammonium sulfate solution, and removes the dissolved HCN in the ammonium sulfate solution, then absorbs HCN with water, and then analyzes and rectifies to produce liquid HCN, while discharging the ammonium sulfate solution balance absorption liquid to avoid the accumulation of HCN oligomers in the absorption liquid and induce the intensification of HCN polymerization. A typical process for preparing liquid HCN includes steps such as sulfuric acid deamination, HCN analysis, HCN absorption, HCN rectification, and heat exchange between low-temperature rich liquid and high-temperature lean liquid, as shown in Figure 3 .

[0005] All the disclosed reaction gas absorption methods at present are ammonia and water, HCN absorption respectively, ammonia absorbent is divided into two kinds, one is ammonium dihydrogen phosphate absorbs ammonia to generate monohydrogen phosphate, the other is sulfuric acid absorbs ammonia to generate ammonium sulfate, for example, the method disclosed in patent document CN107500313A. The existing HCN refining process is introduced from foreign technology, which has been used for a long time and the process is relatively mature and stable; and for large-scale process equipment, the reaction structure and process are not easily changed; in addition, the existing technology generally believes that when using sulfuric acid to absorb ammonia, the generated ammonium sulfate may have a negative impact on the physical absorption of HCN, so it is not thought that HCN, NH3 and H2O in the reaction gas are treated by one-step absorption. However, the ammonia in the reaction gas is absorbed into ammonium sulfate solution, HCN needs to be resolved, and HCN in the sulfur ammonium solution is removed; the HCN-containing steam enters the system again, consumes steam and increases the energy consumption of HCN absorption; a small part of water in the reaction gas is discharged with the ammonium sulfate solution, and most of it enters the rectification lean liquid and is continuously discharged from the HCN rectification tower, increasing the treatment amount of the rectification lean liquid. Under the development trend of advocating energy-saving and consumption-reducing process, the existing technology for processing the reaction gas of ammonia oxidation method for synthesizing HCN is not short and economical. SUMMARY

[0006] Therefore, one of the purposes of the present application is to provide a method for preparing liquid HCN by ammonia oxidation method, which uses a sulfuric acid solution to fully absorb HCN, NH3 and H2O in the reaction gas, dissolves HCN in water, neutralizes NH3 with sulfuric acid to form stable ammonium sulfate, and condenses H2O to form a continuously updated solvent, then resolves and rectifies HCN to obtain liquid HCN and absorption lean liquid, part of the absorption lean liquid is supplemented with sulfuric acid and recycled as absorbent, and part of the lean liquid is continuously discharged from the system to recover ammonium sulfate.

[0007] The technical scheme is as follows:

[0008] A method for preparing liquid HCN by ammonia oxidation method, the key is that the steps are:

[0009] Reaction gas absorption: the reaction gas containing HCN, NH3, H2O and inert gas is introduced into the absorption device, and the H2O and HCN are absorbed while the neutralization reaction of the ammonia is carried out by introducing the sulfuric acid solution, to generate absorption rich liquid, and the tail gas outlet of the absorption device discharges the neutralization tail gas;

[0010] Resolution and rectification: the absorption rich liquid is sent into the rectification device for resolution and rectification to obtain liquid HCN and absorption lean liquid;

[0011] Absorption lean liquid treatment: the absorption lean liquid is divided into two parts, the first part of the absorption lean liquid is mixed with sulfuric acid to form the sulfuric acid solution, and then introduced into the absorption device together, and the second part of the absorption lean liquid recovers ammonium sulfate.

[0012] As preferred, the mass concentration of free sulfuric acid in the above-mentioned sulfuric acid-containing solution is 2-8%, the temperature of the sulfuric acid-containing solution is 0-10°C, the discharge temperature of the absorption rich solution is 10-40°C, and the temperature of the neutralization tail gas discharged from the absorption device is 0-20°C.

[0013] As preferred, the temperature of the neutralization tail gas discharged from the absorption device is 5-15°C.

[0014] As preferred, the temperature of the neutralization tail gas discharged from the absorption device is 5-8°C.

[0015] As preferred, the temperature of the sulfuric acid-containing solution is 3-8°C, and the discharge temperature of the absorption rich solution is 10-30°C.

[0016] As preferred, after the first part of the absorption lean solution is subjected to heat exchange with the absorption rich solution in a heat exchanger, the first part of the absorption lean solution is mixed with sulfuric acid again, and the absorption rich solution is fed into the rectification device again.

[0017] As preferred, an acidic polymerization inhibitor is also introduced into the rectification device to inhibit the polymerization reaction of HCN.

[0018] As preferred, the acidic polymerization inhibitor is any one of concentrated sulfuric acid, SO2, concentrated acetic acid and hydroxyacetic acid.

[0019] As preferred, the rectification device is a rectification column, the absorption rich solution is fed into the rectification column from the middle part of the rectification column, the acidic polymerization inhibitor is fed into the rectification column from the top of the rectification column, the liquid HCN is drawn from the top of the rectification column, and the absorption lean solution is drawn from the bottom of the rectification column.

[0020] As preferred, the pressure at the bottom of the rectification column is normal pressure, and the pressure at the top of the rectification column is higher than 80 kpaA and does not exceed 20 kpaG.

[0021] The feeding temperature of the absorption rich solution is 50-100°C, the mass content of HCN in the absorption rich solution is 0.5-2.0%, the temperature of the absorption lean solution discharged from the bottom of the rectification column is 80-120°C, and the mass content of HCN in the absorption lean solution is less than 0.05%.

[0022] The temperature of the liquid HCN collected from the top of the rectification column is not higher than -10°C, and the concentration is 95.0-99.9%.

[0023] As preferred, the pressure at the top of the rectification column is 80-100 kpaA.

[0024] As preferred, the mass content of HCN in the absorption rich solution is 1.0-1.5%.

[0025] As preferred, the feeding temperature of the absorption rich solution is 70-90°C.

[0026] Preferably, the temperature of the absorption lean solution discharged from the rectification tower is 90-110 DEG C.

[0027] The second object of the present application is to provide a reaction gas absorption system.

[0028] The technical scheme is as follows:

[0029] The reaction gas absorption system is used for treating reaction gas containing HCN, NH3, H2O and inert gas, and comprises an absorption device and a rectification device.

[0030] The rectification device is provided with an absorption rich solution inlet, an absorption lean solution outlet and a liquid HCN outlet.

[0031] The sulfuric acid supply device is connected to the sulfuric acid solution inlet, and the absorption rich solution outlet is connected to the absorption rich solution inlet.

[0032] The liquid HCN outlet is connected to a liquid HCN collecting device.

[0033] The absorption lean solution outlet is connected to the sulfuric acid solution inlet, and is further connected to an ammonium sulfate recovery device.

[0034] Preferably, the reaction gas absorption system further comprises a heat exchanger, which is provided with a rich solution flow channel and a lean solution flow channel capable of heat exchange with each other.

[0035] The absorption rich solution outlet is connected to the absorption rich solution inlet through the rich solution flow channel, and the absorption lean solution outlet is connected to the sulfuric acid solution inlet through the lean solution flow channel.

[0036] Preferably, the tail gas outlet is connected to a tail gas treatment device.

[0037] The rectification device is a rectification tower, the top of which is provided with the liquid HCN outlet and a polymerization inhibitor inlet, the middle of which is provided with the absorption rich solution inlet, and the bottom of which is provided with the absorption lean solution outlet.

[0038] The polymerization inhibitor inlet is further connected to a polymerization inhibitor adding device.

[0039] The process method of the present application has the following advantages: compared with the prior art, the process method of the present application completes full absorption in one step, and then rectification is performed to obtain liquid HCN; through engineering simulation calculation and experimental research, it is found that the generated ammonium sulfate in the absorption solution does not affect the absorption effect of HCN; the process flow is short, the equipment is less, the investment is lower, the operation is more stable and safe, and the total energy consumption is lower. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 is a schematic diagram of a production system;

[0041] Figure 2 is a process flow diagram of the method of the present application;

[0042] Figure 3 is a process flow diagram of the prior art. DETAILED DESCRIPTION

[0043] The present application is further illustrated by the following examples and figures.

[0044] Example 1

[0045] Example 1 provides a reaction gas absorption system for the production of liquid HCN by the ammoxidation process.

[0046] A reaction gas absorption system for treating reaction gas containing HCN, NH3, H2O and inert gas, comprising an absorption device 1, a rectification device 3, the absorption device 1 being provided with a reaction gas inlet, a sulfuric acid solution inlet, an absorption rich liquid outlet and a tail gas outlet; the rectification device 3 being provided with an absorption rich liquid inlet, an absorption lean liquid outlet and a liquid HCN outlet; the sulfuric acid solution inlet being connected with a sulfuric acid supply device 4, the absorption rich liquid outlet being connected with the absorption rich liquid inlet; the liquid HCN outlet being connected with a liquid HCN collection device 7.

[0047] In order to reduce the treatment amount of the ammonium sulfate solution, the absorption lean liquid outlet is connected with the sulfuric acid solution inlet, and further connected with an ammonium sulfate recovery device 8.

[0048] In order to improve the heat utilization rate of the system, the reaction gas absorption system further comprises a heat exchanger 2, which is provided with a rich liquid flow channel and a lean liquid flow channel capable of heat exchange with each other, and the flow directions of the two are opposite. The absorption rich liquid outlet is connected with the absorption rich liquid inlet through the rich liquid flow channel, and the absorption lean liquid outlet is connected with the sulfuric acid solution inlet through the lean liquid flow channel.

[0049] In order to control the temperature of the absorption lean liquid returned to the absorption device 1, a cooling device is further provided on the pipeline between the outlet end of the lean liquid flow channel and the sulfuric acid solution inlet. The cooling device can be a water cooling device, and can further comprise a low-temperature water cooling device.

[0050] Specifically, the absorption device 1 can be an absorption tower, such as one or a combination of a packed tower and a plate tower. The tail gas outlet is connected with a tail gas treatment device 5 for treating the tail gas to meet the emission standard.

[0051] Specifically, in this embodiment, the rectification device 3 is a rectification tower, such as one or a combination of a packed tower and a plate tower. The top of the rectification tower is provided with a liquid HCN outlet and a polymerization inhibitor inlet, the middle of the rectification tower is provided with an absorption rich liquid inlet, and the bottom of the rectification tower is provided with an absorption lean liquid outlet. The polymerization inhibitor inlet is also connected with a polymerization inhibitor adding device 6.

[0052] Based on the above reaction gas absorption system, a method for preparing liquid HCN by the ammonia oxidation method is provided, and the steps are as follows:

[0053] Reaction gas absorption: the reaction gas containing HCN, NH3, H2O and inert gas is introduced into the absorption device 1, and at the same time, the deamination neutralization reaction is carried out by introducing the sulfuric acid solution, and H2O and HCN are absorbed to generate absorption rich liquid. The reaction gas is natural gas or the mixed gas product of the methanol ammonia oxidation method for synthesizing HCN, and the inert gas refers to the gas that hardly causes physical state change and does not react with other products or reagents in the subsequent separation and treatment steps such as absorption and rectification, for example, nitrogen. The neutralization tail gas discharged from the tail gas outlet of the absorption device 1 is sent to the tail gas treatment device 5 for treatment.

[0054] Rectification and analysis: the absorption rich liquid is sent to the rectification device 3 for rectification and analysis to obtain liquid HCN and absorption lean liquid.

[0055] Absorption lean liquid treatment: the absorption lean liquid is divided into two parts, and the first part of the absorption lean liquid is mixed with sulfuric acid to form the sulfuric acid solution, and then introduced into the absorption device 1 together, and the second part of the absorption lean liquid is recovered to ammonium sulfate. Unlike the use of high-concentration sulfuric acid solution in the prior art, the mass concentration of free sulfuric acid in the sulfuric acid-containing solution in this embodiment is 2-8%, and the pH is preferably 1.0-5.0, and the temperature of the sulfuric acid-containing solution is 0-10°C, which is used for neutralization reaction and cooling absorption of the reaction gas. More preferably, considering the absorption effect and cost, the temperature of the sulfuric acid-containing solution is 3-8°C, and the pH value is 2.5-3.5. The concentration of ammonium sulfate in the sulfuric acid-containing solution is limited by the balance, and is different according to different natural gas ammonia oxidation methods or methanol ammonia oxidation methods, and is generally 5-15%.

[0056] In this way, the absorption of NH3, HCN and H2O can be completed at one time in the absorption device; at the same time, the absorption lean liquid generated after the rectification of the liquid HCN, i.e. the ammonium sulfate solution, is partially returned to the absorption device 1 for recycling, and only part of the absorption lean liquid is used for recovering ammonium sulfate, so that the amount of absorption lean liquid is greatly reduced. Overall, the process is more concise, and the energy consumption is reduced.

[0057] The temperature of the neutralization tail gas discharged after absorption is 0-20°C, and the temperature is preferably 5-15°C; the tail gas after absorption does not contain NH3, and the volume content of HCN is less than 0.05%.

[0058] To further utilize the cold energy of the liquid in the absorption device 1, the first part of the absorption lean liquid is mixed with sulfuric acid and fed into the absorption device 1 after heat exchange with the absorption rich liquid in the heat exchanger 2, and the absorption rich liquid is fed into the rectification device 3. In this way, the absorption rich liquid can be used to cool the absorption lean liquid with a higher temperature, so that the temperature of the sulfuric acid-containing solution fed into the absorption device 1 can be more conveniently controlled at a lower level.

[0059] In addition, an acidic polymerization inhibitor is also introduced into the rectification device 3 to inhibit the polymerization reaction of HCN, which can be any one of concentrated sulfuric acid, SO2, concentrated acetic acid, and hydroxyacetic acid.

[0060] When the rectification device 3 is a rectification column, the absorption rich liquid is introduced from the middle of the rectification column, the acidic polymerization inhibitor is introduced from the top of the rectification column, the liquid HCN is drawn from the top of the rectification column, and the absorption lean liquid is drawn from the bottom of the rectification column.

[0061] The top of the rectification column can be kept at normal pressure, slightly negative pressure (≥80 kpaA), or slightly positive pressure (≤20 kpaG).

[0062] The temperature of the absorption rich liquid introduced from the middle of the rectification column is 50-100°C, preferably 70-90°C, and the mass content of HCN in the solution is 0.5-2.0%, preferably 1.0-1.5%.

[0063] The temperature of the absorption lean liquid flowing out from the bottom of the rectification column is 80-120°C, preferably 90-110°C, and the mass content of HCN in the absorption lean liquid is less than 0.05%.

[0064] The liquid HCN is collected from the top of the rectification column, with a temperature less than -10°C and a concentration of 95.0-99.9%.

[0065] Using a 4000 t / a HCN device of a natural gas ammonia oxidation method in a domestic factory as a reference, the related comparative experiments before and after the technical improvement were carried out.

[0066] Comparative Example 1

[0067] The raw material ammonia gas was fed at a flow rate of 502.4 kg / h, the raw material natural gas was fed at a flow rate of 696 Nm 3 / h, the air was fed at a flow rate of 4681 kg / h, and the volume ratio of the raw material gases was ammonia gas:natural gas:air = 1:1.05:5.50, and the total raw material gas was fed at a flow rate of 5722.4 kg / h.

[0068] After the ammonia oxidation reaction, the gas composition content was analyzed under stable conditions, and the average molecular weight of the reaction gas was calculated to be 22.6, and the flow rates of the gas components were as shown in Table 1.

[0069] Table 1 Reaction gas composition

[0070] Component HCN [N2] [H2] H2O [CAT] O2 [CAT] CO CO2 mol % 7.5 52.2 12.3 20.6 2.1 0.2 0.1 4.1 0.9 kg / h 513.3 3704.6 62.4 939.8 90.5 16.2 4.1 291.0 100.4

[0071] Before the technical improvement, the treatment process of the reaction gas absorption treatment device for the reaction gas includes the steps of sulfuric acid deamination, ammonium sulfate solution de-cyanide, HCN absorption and HCN rectification. Figure 3 According to the detection, the operation condition of the 4000t / a HCN device before the technical improvement is related to the parameters of HCN, NH3 and H2O in the reaction gas as shown in Table 2.

[0072] Table 2: Gas phase composition, liquid phase composition and related parameters of each treatment step

[0073]

[0074]

[0075] The HCN flow in the reaction gas is 513.3kg / h, of which 0.26kg / h enters the ammonium sulfate solution, 4.3kg / h enters the tail gas, 8.2kg / h is discharged from the rectification lean liquid, 504kg / h is recovered as liquid HCN, and the yield is 98.2%.

[0076] The water flow in the reaction gas is 939.8kg / h, of which 330kg / h enters the ammonium sulfate solution, 17.1kg / h enters the tail gas, 1.0kg / h enters the liquid HCN, and the remaining 591.7kg / h is continuously discharged from the rectification tower lean liquid.

[0077] The ammonia flow in the reaction gas is 90.5kg / h, which enters the ammonium sulfate solution in the form of ammonium sulfate.

[0078] According to the reaction gas absorption system of Example 1, the original device is technically improved, and the full absorption process is used to absorb HCN, NH3 and H2O in the reaction gas, and then HCN rectification is performed. The absorption rich liquid temperature, absorption tower top temperature, absorption liquid H2SO4 concentration and rectification tower lean liquid ammonium sulfate concentration are changed for related experiments.

[0079] Examples 2-5

[0080] The difference between Examples 2-5 is the absorption rich liquid discharge temperature.

[0081] Raw material gas, HCN synthesis reaction condition: according to the original operation.

[0082] Absorption conditions: the reaction gas containing HCN, NH3, H2O and the absorption lean solution from HCN rectification are added with a certain amount of sulfuric acid to obtain a sulfuric acid-containing solution, which is condensed, dissolved and chemically reacted in the total absorption tower. The mass concentration of free sulfuric acid in the sulfuric acid-containing solution is controlled to be 5-8%, the amount of ammonia in the reaction gas is neutralized, and the temperature of the sulfuric acid-containing solution is controlled to be 5°C after heat exchange. The tail gas temperature at the top of the absorption tower is controlled to be 8°C.

[0083] Rectification conditions: the rectification tower is under normal pressure at the bottom and 85 kpaA at the top; an acidic polymerization inhibitor acetic acid is added from the top of the rectification tower; the absorption rich solution is fed from the middle of the rectification tower, and the feeding temperature is 85°C; the temperature of the absorption lean solution at the bottom of the rectification tower is 110°C; the temperature of the liquid HCN taken out from the top of the rectification tower is -12°C.

[0084] Experiments are carried out by adjusting the discharge temperature of the absorption rich solution to be 10, 20, 30 and 40°C respectively, each group of experiments is stably operated for not less than 24 hours, and the HCN mass content of the absorption rich solution, the HCN mass content of the discharged ammonium sulfate solution, the liquid HCN mass content, the HCN yield, and the pressure drop of the rectification tower and the color of the lean solution reflecting the HCN polymerization phenomenon are investigated.

[0085] Table 3 Parameters of the reaction system at different absorption rich solution temperatures

[0086]

[0087] As can be seen from Table 3, the temperature of the absorption rich solution has an effect on the HCN content of the absorption rich solution, the higher the temperature, the lower the HCN mass content of the absorption rich solution; but it has no effect on the HCN mass content of the absorption lean solution, the HCN mass content of the discharged ammonium sulfate solution, the liquid HCN mass content, the HCN yield, the pressure drop of the rectification tower and the color of the lean solution, and the more suitable temperature of the absorption rich solution is 10-20°C.

[0088] Examples 6-9

[0089] The difference between Examples 6-9 is that the neutralization tail gas temperature at the top of the absorption tower is different.

[0090] The raw material gas, HCN synthesis reaction conditions, absorption conditions and rectification conditions are the same as those in Reference Example 2.

[0091] The stable absorption rich solution temperature is 15°C, the temperature of the absorption lean solution returned to the inlet of the sulfuric acid-containing solution is adjusted by adjusting the cooling amplitude of the cooling device, and the neutralization tail gas temperature at the top of the absorption tower is adjusted to be 3, 5, 8 and 10°C respectively, each group of experiments is stably operated for not less than 24 hours, and the HCN mass content of the absorption solution, the HCN mass content of the discharged sulfuric acid solution, the liquid HCN mass content, the HCN yield, and the pressure drop of the rectification tower and the color of the lean solution reflecting the HCN polymerization phenomenon are investigated.

[0092] As shown in Table 4, the tower top temperature has an effect on the HCN yield, but has no effect on the HCN mass content of the absorption liquid, the HCN mass content of the discharged sulfuric acid liquid, the liquid HCN mass content, the rectification tower pressure drop and the lean liquid color. In order to improve the HCN yield, the more suitable tower top temperature is 5-8°C.

[0093] Table 4 Parameters of the reaction system under different tower top tail gas temperature conditions of the absorption tower

[0094]

[0095] Examples 10-12

[0096] The difference between Examples 10-12 is the free H2SO4 concentration in the sulfuric acid-containing solution.

[0097] The raw material gas, the HCN synthesis reaction condition, the absorption condition and the rectification condition are the same as in Example 2.

[0098] The stable absorption rich liquid temperature is 15°C, the free H2SO4 concentration in the sulfuric acid-containing solution is adjusted to be 5%, 6% and 8% respectively, and the experiment is performed, each group of experiment is stably operated for not less than 24h, and the HCN mass content of the absorption liquid, the HCN mass content of the discharged sulfuric acid liquid, the liquid HCN mass content, the HCN yield, and the rectification tower pressure drop and the lean liquid color reflecting the HCN polymerization phenomenon are observed.

[0099] As shown in Table 5, the H2SO4 concentration in the absorption liquid has an effect on the HCN concentration of the absorption rich liquid and the HCN yield, but has no effect on the HCN mass content of the discharged sulfuric acid liquid, the liquid HCN mass content, the rectification tower pressure drop and the lean liquid color, and the more suitable H2SO4 concentration in the absorption liquid is 5-8%, according to the amount of neutralizing ammonia in the reaction gas.

[0100] Table 5 Parameters of the reaction system under different free H2SO4 concentration conditions of the sulfuric acid-containing solution

[0101]

[0102] Examples 13-15

[0103] The difference between Examples 13-15 is the rectification tower top pressure.

[0104] The raw material gas, the HCN synthesis reaction condition, the absorption condition and the rectification condition are the same as in Example 2.

[0105] The stable absorption rich liquid temperature was 15°C, and the rectification column top pressure was adjusted to 80 kPaA, 90 kPaA, and 100 kPaA for experiment, and the column bottom pressure and lean liquid temperature changed accordingly. Each group of experiments was stably operated for not less than 24 hours, and the HCN mass content of the discharged sulfuric acid liquid, the liquid HCN mass content, the HCN yield, and the pressure drop of the rectification column and the lean liquid color reflecting HCN polymerization were observed.

[0106] As shown in Table 6, the change of the rectification column top pressure slightly affected the lean liquid HCN mass content and the HCN yield. When the pressure increased to 100 kPaA, the lean liquid color deepened, indicating that the HCN oligomers increased, and the more suitable pressure of the rectification column top was 80-90 kPaA.

[0107] Table 6 Parameters of the reaction system under different rectification column top pressure conditions

[0108]

[0109] Examples 16-19

[0110] The difference between Examples 16-19 was the different polymerization inhibitors used.

[0111] The raw gas, HCN synthesis reaction conditions, absorption conditions, and rectification conditions were the same as those in Reference Example 2.

[0112] The stable absorption rich liquid temperature was 15°C, and the rectification column top pressure was adjusted to 80 kPaA, 90 kPaA, and 100 kPaA for experiment, and the column bottom pressure and lean liquid temperature changed accordingly. Each group of experiments was stably operated for not less than 24 hours, and the HCN mass content of the discharged sulfuric acid liquid, the liquid HCN mass content, the HCN yield, and the pressure drop of the rectification column and the lean liquid color reflecting HCN polymerization were observed.

[0113] As shown in Table 7, concentrated sulfuric acid did not corrode 316L material, but HCN polymerization intensified; SO2 did not corrode 316L material, and there was no HCN polymerization intensification; concentrated acetic acid and hydroxyacetic acid slightly corroded 316L material in the column, and there was no HCN polymerization intensification. In this case, the column must be made of higher material resistant to sulfuric acid and organic acid mixed acid.

[0114] Table 7 Influence of different acidic polymerization inhibitors on the parameters of the reaction system

[0115]

[0116]

[0117] Example 20

[0118] The continuous reaction stability of the reaction system after the technical improvement was observed.

[0119] The raw gas, HCN synthesis reaction conditions, absorption conditions, and rectification conditions of Example 2 are referenced.

[0120] After the reaction is stable, the HCN content in the reaction gas is 513.3 kg / h, 4.3 kg / h of HCN enters the tail gas, 5.1 kg / h of HCN is discharged from the rectification lean liquid, 503.5 kg / h of liquid HCN is recovered, and the yield is 98.1%.

[0121] The water content in the reaction gas is 939.8 kg / h, 17.1 kg / h of water enters the tail gas, 1.0 kg / h of water enters the liquid HCN, and the remaining 921.7 kg / h of water is continuously discharged from the rectification tower lean liquid.

[0122] The ammonia content in the reaction gas is 90.5 kg / h, which enters the rectification tower lean liquid in the form of ammonium sulfate, and the ammonium sulfate content in the lean liquid is about 10%.

[0123] The reaction is continuously carried out for a long time, and the parameters of the reaction system are basically stable.

[0124] Table 8 Parameters of the reaction system after the technical improvement

[0125]

[0126]

[0127] As shown in Table 9, under the condition that the reaction gas compositions of the two processes before and after the technical improvement are similar, and by using the more suitable reaction gas treatment conditions for absorption and resolution, the process flow of the process method of the present application is shortened, the equipment requirements are reduced, and the overall energy consumption is lower.

[0128] Table 9 Comparison of the two processes before and after the technical improvement

[0129]

[0130]

[0131] Finally, it should be noted that the above description is only for the preferred embodiments of the present application, and those of ordinary skill in the art can make various similar modifications under the inspiration of the present application without deviating from the purpose and scope of the claims. Such modifications fall within the scope of the present application.

Claims

1. A process for the production of liquid HCN by the oxidation of ammonia, characterized in that The steps are: Reaction gas absorption: the reaction gas containing HCN, NH3, H2O and inert gas is introduced into the absorption device (1), and H2O and HCN are absorbed while the deamination neutralization reaction is carried out by introducing the sulfuric acid solution, to generate absorption rich liquid, and the tail gas outlet of the absorption device discharges neutralization tail gas; Analysis rectification: the absorption rich liquid is sent into the rectification device (3) for analysis and rectification to obtain liquid HCN and absorption lean liquid; Absorption lean liquid treatment: the absorption lean liquid is divided into two parts, the first part of the absorption lean liquid is mixed with sulfuric acid to form the sulfuric acid solution, and then introduced into the absorption device (1) together, and the second part of the absorption lean liquid recovers ammonium sulfate; An acidic polymerization inhibitor is also introduced into the rectification device (3) to inhibit the polymerization reaction of HCN; The rectification device (3) is a rectification column, the absorption rich liquid is introduced from the middle of the rectification column, the acidic polymerization inhibitor is introduced from the top of the rectification column, the liquid HCN is drawn from the top of the rectification column, and the absorption lean liquid is drawn from the bottom of the rectification column; The mass concentration of free sulfuric acid in the sulfuric acid solution is 2-8%, the temperature of the sulfuric acid solution is 0-10℃, the discharge temperature of the absorption rich liquid is 10-40℃, and the temperature of the neutralization tail gas discharged by the absorption device is 0-20℃; The pressure at the bottom of the rectification column is atmospheric pressure, and the pressure at the top of the rectification column is above 80kpaA and does not exceed 20kpaG.

2. A process for the production of liquid HCN by the ammoxidation process according to claim 1, characterized in that: The temperature of the sulfuric acid solution is 3-8℃, and the discharge temperature of the absorption rich liquid is 10-30℃.

3. A process for the production of liquid HCN by the ammoxidation of a hydrocarbon according to claim 1 or 2, characterized in that: The first part of the absorption lean liquid exchanges heat with the absorption rich liquid in the heat exchanger (2), then the first part of the absorption lean liquid is mixed with sulfuric acid, and the absorption rich liquid is sent into the rectification device (3).

4. The method for preparing liquid HCN by ammonia oxidation according to claim 1, characterized in that: The feed temperature of the absorption rich liquid is 50-100℃, the mass content of HCN in the absorption rich liquid is 0.5-2.0%, the temperature of the absorption lean liquid discharged from the bottom of the rectification column is 80-120℃, and the mass content of HCN in the absorption lean liquid is less than 0.05%; The temperature of the liquid HCN collected from the top of the rectification column is not higher than -10℃, and the concentration is 95.0-99.9%.

5. A reaction gas absorption system for treating a reaction gas containing HCN, NH3, H20 and inert gas, comprising an absorption device (1), a rectification device (3), characterized in that: The absorption device (1) is provided with a reaction gas inlet, a sulfuric acid solution inlet, an absorption rich liquid outlet and a tail gas outlet; The rectification device (3) is provided with an absorption rich liquid inlet, an absorption lean liquid outlet and a liquid HCN outlet; The sulfuric acid solution inlet is connected with a sulfuric acid feeding device (4), and the absorption rich liquid outlet is connected with the absorption rich liquid inlet; The liquid HCN outlet is connected with a liquid HCN collecting device (7); The absorption lean liquid outlet is connected with the sulfuric acid solution inlet and is also connected with an ammonium sulfate recovery device (8); The tail gas outlet is connected with a tail gas treatment device (5); The rectification device (3) is a rectification column, the top of the rectification column is provided with the liquid HCN outlet and the polymerization inhibitor inlet, the middle of the rectification column is provided with the absorption rich liquid inlet, and the bottom of the rectification column is provided with the absorption lean liquid outlet. The polymerization inhibitor inlet is also connected with a polymerization inhibitor adding device (6).

6. The reaction gas absorbing system according to claim 5, wherein: The heat exchanger (2) is provided with a rich liquid flow channel and a lean liquid flow channel capable of heat exchange with each other. The absorption rich liquid outlet is connected with the absorption rich liquid inlet through the rich liquid flow channel, and the absorption lean liquid outlet is connected with the sulfuric acid solution inlet through the lean liquid flow channel.

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