Feeding system for improving uniform distribution of nitric acid in nitric acid reduction reaction

Abstract

The utility model belongs to the technical field of dimethyl oxalate synthesis, and particularly provides a feeding system capable of improving uniform distribution of nitric acid in nitric acid reduction reaction, which comprises an alcohol-containing waste liquid-nitric acid mixer, an alcohol-containing waste liquid inlet pipe and a nitric acid inlet pipe connected with an inlet of the alcohol-containing waste liquid-nitric acid mixer, an outlet of the alcohol-containing waste liquid-nitric acid mixer is communicated with an inlet of the nitric acid reduction reactor through a pipeline, an alcohol-containing waste liquid inlet pipe is provided with an alcohol-containing waste liquid feeding regulating valve, and a nitric acid inlet pipe is provided with a nitric acid feeding regulating valve, a nitric acid flowmeter and a nitric acid feeding stop valve. According to the system, the mixing uniformity of nitric acid can be improved, the nitric acid reduction efficiency is improved, the adding amount of the nitric acid is reduced, equipment corrosion is reduced, and meanwhile the risk of material mixing under the abnormal condition is avoided by arranging the check valve and the stop valve.

Description

Technical Field

[0001] The utility model relates to the technical field of dimethyl oxalate synthesis, and particularly relates to a feeding system for improving the uniform distribution of nitric acid in the nitric acid reduction reaction. Background Technique

[0002] In the dimethyl oxalate synthesis device, due to reasons such as the purge of the system, the venting of the tail gas tower, and the unreacted nitric acid in the wastewater, nitrogen elements will be lost. Nitric acid needs to be replenished into the nitric acid reduction reactor to react with NO in the recycle gas and methanol in the alcohol-containing waste liquid to produce MN as the nitrogen element supply system to maintain the nitrogen element balance.

[0003] Since the amount of nitric acid added is very small, about 150 kg / h of nitric acid needs to be replenished corresponding to 30 t / h of alcohol-containing waste liquid. The nitric acid is directly added to the nitric acid reduction reactor, and the mixing effect is not good. The existing process still needs to start the stirrer to improve the mixing effect, resulting in high power consumption. The uneven distribution of nitric acid concentration will lead to an increase in the amount of nitric acid added, increasing the corrosion rate of the system equipment by nitric acid, and there is also a risk of local nitric acid concentration enrichment and over-temperature caused by violent reactions. Summary of the Invention

[0004] The technical problem to be solved by the utility model is to provide a feeding system for improving the uniform distribution of nitric acid in the nitric acid reduction reaction and improving the mixing uniformity of nitric acid in the nitric acid reduction reactor.

[0005] To solve the above technical problems, the technical solution adopted by the utility model is: a feeding system for improving the uniform distribution of nitric acid in the nitric acid reduction reaction, including an alcohol-containing waste liquid-nitric acid mixer, an alcohol-containing waste liquid inlet pipe and a nitric acid inlet pipe are connected to the inlet of the alcohol-containing waste liquid-nitric acid mixer, and the outlet of the alcohol-containing waste liquid-nitric acid mixer is communicated with the inlet of the nitric acid reduction reactor through a pipeline. An alcohol-containing waste liquid feed regulating valve is provided on the alcohol-containing waste liquid inlet pipe, and a nitric acid feed regulating valve, a nitric acid flowmeter and a nitric acid feed cut-off valve are provided on the nitric acid inlet pipe.

[0006] In a preferred solution, a check valve is provided on the nitric acid inlet pipe.

[0007] In a preferred solution, a nitric acid thermometer is provided on the nitric acid inlet pipe.

[0008] In a preferred solution, a differential pressure gauge is provided between the nitric acid inlet pipe and the alcohol-containing waste liquid inlet pipe.

[0009] The feeding system for improving the uniform distribution of nitric acid in the nitric acid reduction reaction provided by the utility model has the following beneficial effects:

[0010] 1. Compared with the prior art, after adopting this feeding system, nitric acid first mixes with the alcohol-containing waste liquid in the alcohol-containing waste liquid-nitric acid mixer. The mixed process liquid then mixes with the circulating gas bubbling gas in the nitric acid reduction reactor, greatly improving the mixing uniformity of nitric acid, reducing the amount of nitric acid added, reducing equipment corrosion, and being pre-mixed evenly before entering the nitric acid reduction reactor, which can avoid local enrichment of nitric acid concentration and prevent the risk of over-temperature caused by violent reactions, and has a positive significance for the stable operation of the device.

[0011] 2. A differential pressure gauge, a flow meter, and a thermometer are set to interlock and monitor the nitric acid feed, avoiding the situation of the alcohol-containing waste liquid flowing into the nitric acid pipeline and preventing the overpressure explosion of the nitric acid pipeline caused by the violent reaction between methanol and nitric acid. Brief Description of the Drawings

[0012] The following further describes the present utility model in conjunction with the drawings and embodiments:

[0013] Figure 1 It is a schematic structural diagram of the present utility model;

[0014] In the figure: alcohol-containing waste liquid-nitric acid mixer 1, alcohol-containing waste liquid inlet pipe 2, nitric acid inlet pipe 3, nitric acid reduction reactor 4, check valve 5, nitric acid feed cut-off valve 6, nitric acid feed regulating valve 7, differential pressure gauge 8, nitric acid flow meter 9, nitric acid thermometer 10, alcohol-containing waste liquid feed regulating valve 11. Detailed Embodiment

[0015] As Figure 1 shown, a feeding system for improving the uniform distribution of nitric acid in the nitric acid reduction reaction includes an alcohol-containing waste liquid-nitric acid mixer 1, an alcohol-containing waste liquid inlet pipe 2, and a nitric acid inlet pipe 3 connected to the inlet of the alcohol-containing waste liquid-nitric acid mixer 1. The alcohol-containing waste liquid-nitric acid mixer 1 mixes the added alcohol-containing waste liquid and nitric acid to form a process liquid. The outlet of the alcohol-containing waste liquid-nitric acid mixer 1 is connected to the inlet of the nitric acid reduction reactor 4 through a pipeline. An alcohol-containing waste liquid feed regulating valve 11 is provided on the alcohol-containing waste liquid inlet pipe 2, and a nitric acid feed regulating valve 7 and a nitric acid flow meter 9 are provided on the nitric acid inlet pipe 3. By setting the alcohol-containing waste liquid feed regulating valve 11 and the nitric acid feed regulating valve 7, it is convenient to adjust the mixing ratio of the alcohol-containing waste liquid and the nitric acid mixed process liquid.

[0016] The provided nitric acid flow meter 9 facilitates the monitoring of the nitric acid flow in the nitric acid inlet pipe 3. During specific production, when the flow in the nitric acid inlet pipe 1 drops to the parameter value, the nitric acid feed cut-off valve 6 operates to cut off the nitric acid feed, preventing the alcohol-containing waste liquid from flowing into the nitric acid pipeline and causing the overpressure explosion of the nitric acid pipeline due to violent reactions.

[0017] Preferably, a check valve 5 is provided on the nitric acid inlet pipe 3. The check valve 5 and the nitric acid feed cut-off valve 6 are arranged at the tail end of the nitric acid inlet pipe 3. By providing the check valve 5, the reverse flow of the alcohol-containing waste liquid into the nitric acid inlet pipe 3 is prevented, and overpressure explosion is avoided.

[0018] Preferably, a nitric acid thermometer 10 is provided on the nitric acid inlet pipe 3. By providing the nitric acid thermometer 10, the temperature of the nitric acid is monitored. During specific production, when the temperature of the nitric acid inlet pipe 1 rises to the set parameter value, the nitric acid feed cut-off valve 6 operates to cut off the nitric acid feed.

[0019] A differential pressure gauge 8 is provided between the nitric acid inlet pipe 3 and the alcohol-containing waste liquid inlet pipe 2. The differential pressure gauge 8 is used to measure the pressure difference between the inlet ends of the nitric acid inlet pipe 3 and the alcohol-containing waste liquid inlet pipe 2. During specific use, when the nitric acid inlet pipe 1 abnormally drops in pressure and the pressure difference between the nitric acid inlet pipe 1 and the alcohol-containing waste liquid inlet pipe 2 drops to the set parameter value, the nitric acid feed cut-off valve 6 operates to cut off the nitric acid feed.

[0020] During specific production, the alcohol-containing waste liquid at 0.4 MPa is controlled by the feed regulating valve 11 to add the amount into the alcohol-containing waste liquid-nitric acid mixer 1, and the replenishment amount is 30 t / h. The nitric acid at 0.75 MPa is controlled by the feed regulating valve 7 to add the amount into the alcohol-containing waste liquid-nitric acid mixer 1, and the replenishment amount is 150 kg / h. After the alcohol-containing waste liquid and the nitric acid are uniformly mixed in the alcohol-containing waste liquid-nitric acid mixer 1, the mixed process liquid is sent to the nitric acid reduction reactor 4 through the outlet pipeline of the alcohol-containing waste liquid-nitric acid mixer 1, and further uniformly mixed with the circulating gas bubbling gas before starting the reaction. When the nitric acid inlet pipe 1 abnormally drops in pressure and the instrument parameters of the differential pressure gauge 8 between the nitric acid inlet pipe 1 and the alcohol-containing waste liquid inlet pipe 2, the flowmeter 9 of the nitric acid inlet pipe 1 or the thermometer 10 of the nitric acid inlet pipe 1 reach the interlock value, the nitric acid feed is quickly cut off. In this embodiment, when the pressure difference between the nitric acid inlet pipe 1 and the alcohol-containing waste liquid inlet pipe 2 drops to 0.1 MPa, the flow rate of the nitric acid inlet pipe 1 drops to 30 kg / h, or the temperature of the nitric acid inlet pipe 1 rises to 45 °C, the nitric acid feed cut-off valve 6 operates to interlock and cut off the nitric acid feed, preventing the alcohol-containing waste liquid from flowing into the nitric acid pipeline and causing overpressure explosion of the nitric acid pipeline due to violent reaction.

[0021] The nitric acid consumption is reduced from 250 kg / h before the transformation to 150 kg / h. Calculated based on 8000 hours per year, 800 t of nitric acid can be saved in one year. Calculated at 1036 yuan / t for nitric acid, 828,800 yuan can be saved in one year. The reduction of the nitric acid addition amount will reduce the corrosion of the subsequent equipment. Premixing evenly before entering the nitric acid reduction reactor can avoid local enrichment of nitric acid concentration and prevent the risk of over-temperature caused by violent reaction, which has a positive significance for the safe and stable operation of the device. At the same time, the setting of the nitric acid feed interlock avoids the situation of the alcohol-containing waste liquid flowing into the nitric acid pipeline and prevents overpressure explosion of the nitric acid pipeline caused by the violent reaction between methanol and nitric acid.

[0022] The above embodiments are only the preferred technical solutions of the present utility model and should not be regarded as limitations on the present utility model. The embodiments in this application and the features in the embodiments can be arbitrarily combined with each other without conflict. The protection scope of the present utility model shall be the technical solutions recorded in the claims, including the equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, the equivalent replacement improvements within this scope are also within the protection scope of the present utility model.

Claims

1. A feeding system for improving the uniform distribution of nitric acid in a nitric acid reduction reaction, characterized in that: The invention comprises an alcohol-containing waste liquid-nitric acid mixer (1), an alcohol-containing waste liquid inlet pipe (2) and a nitric acid inlet pipe (3) connected to the inlet of the alcohol-containing waste liquid-nitric acid mixer (1), an outlet of the alcohol-containing waste liquid-nitric acid mixer (1) being connected to the inlet of a nitric acid reduction reactor (4) through a pipeline, an alcohol-containing waste liquid feed regulating valve (11) being provided on the alcohol-containing waste liquid inlet pipe (2), and a nitric acid feed regulating valve (7), a nitric acid flowmeter (9) and a nitric acid feed cut-off valve (6) being provided on the nitric acid inlet pipe (3).

2. A feeding system for improving uniform distribution of nitric acid in nitric acid reduction reaction according to claim 1, characterized in that: The nitric acid inlet pipe (3) is provided with a check valve (5).

3. A feeding system for improving uniform distribution of nitric acid in nitric acid reduction reaction according to claim 1, characterized in that: The nitric acid inlet pipe (3) is provided with a nitric acid thermometer (10).

4. A feeding system for improving uniform distribution of nitric acid in nitric acid reduction reaction according to claim 1, characterized in that: A differential pressure gauge (8) is provided between the nitric acid inlet pipe (3) and the alcohol-containing waste liquid inlet pipe (2).

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