Device for reducing ammonium sulfate content in amide oil

Abstract

The utility model relates to the technical field of caprolactam, in particular to a device for reducing ammonium sulfate content in amide oil, which comprises a static mixer, the static mixer is provided with an amide oil feed pipe and a benzene feed pipe, a discharge port of the static mixer is connected to a decanter after passing through a decanter feed pump and a heat exchanger, the decanter is provided with a heavy phase discharge port and a light phase discharge port, and the heavy phase discharge port is connected with the light phase discharge port. A light-phase discharge port is conveyed to a cyclone membrane filter through a decanter discharge pump, a heavy-phase outlet of the cyclone membrane filter and a heavy-phase discharge port of the decanter are converged and connected to an ammonium sulfate mother liquor tank, and a light-phase outlet of the cyclone membrane filter is connected to a subsequent amide oil purification process. The device is provided with the links of benzene dissolving and crystallization, filtration, cooling, decanting, refiltration, cyclone separation, membrane filtration and the like, ammonium sulfate mother liquor and free ammonium sulfate particles in the amide oil are removed, the quality of the amide oil is improved, and the content of ammonium sulfate in the amide oil can be reduced to 0.5 wt% or below.

Description

Technical Field

[0001] This utility model belongs to the field of caprolactam production technology and relates to a device for reducing the ammonium sulfate content in caprolactam oil. Background Technology

[0002] Currently, most caprolactam production both domestically and internationally utilizes the Beckmann rearrangement technology. This involves the Beckmann rearrangement of cyclohexanone oxime in the presence of fuming sulfuric acid, resulting in the transformation of cyclohexanone oxime to caprolactam, which then combines with fuming sulfuric acid to exist as caprolactam sulfate esters (hereinafter referred to as the rearrangement solution). The rearrangement solution undergoes an ammonia neutralization reaction with ammonia in an ammonium sulfate crystallizer. Due to the density difference, a high-concentration caprolactam aqueous solution (hereinafter referred to as amide oil) separates from the ammonium sulfate slurry and is sent to a decanter for further separation of entrained ammonium sulfate mother liquor. Finally, the oil enters the amide oil storage tank. Because a large number of fine ammonium sulfate crystal nuclei are formed during the crystallization process, and ammonium sulfate has high solubility in water, a small amount of ammonium sulfate is entrained and dissolved in the amide oil, affecting the quality of the caprolactam product.

[0003] In caprolactam enterprises, the ammonium sulfate content in amide oil is generally around 1%wt. There is no effective technology to directly reduce or remove the ammonium sulfate content in amide oil. It is all treated in downstream refining units by water washing, alkali washing, ion exchange and other methods, which is costly and has limited removal efficiency. Once it fails, it will affect the caprolactam product.

[0004] CN209636135U discloses an apparatus for reducing ammonium sulfate in crude caprolactam. This apparatus involves separating the crude caprolactam into oil and liquid phases using a decanter, followed by centrifugation, and then adding demineralized water to dissolve the ammonium sulfate. The resulting crude caprolactam still contains 0.6-0.7% ammonium sulfate. Therefore, it is necessary to reduce the ammonium sulfate content and improve caprolactam quality by optimizing process control and technological modifications at the source—the caprolactam oil. Summary of the Invention

[0005] This invention provides a device for reducing the ammonium sulfate content in amide oil. It involves mixing benzene with amide oil, then filtering and cooling the mixture before it enters a decanter, and finally filtering it again before it enters a cyclone membrane filter. This method effectively reduces the ammonium sulfate content in amide oil, improves the quality of amide oil, and reduces the ammonium sulfate content in the amide oil to <0.5%wt, which is more than 50% lower than the existing mainstream process.

[0006] The technical solution of this utility model is to provide a device for reducing the ammonium sulfate content in amide oil, including a static mixer with an amide oil feed pipe and a benzene feed pipe. The outlet of the static mixer is connected to the decanter via a decanter feed pump and a heat exchanger. The decanter has a heavy phase outlet and a light phase outlet. The light phase outlet is pumped to a hydrocyclone membrane filter via a decanter discharge pump. The heavy phase outlet of the hydrocyclone membrane filter merges with the heavy phase outlet of the decanter and is connected to the ammonium sulfate mother liquor tank. The light phase outlet of the hydrocyclone membrane filter is connected to the subsequent amide oil purification process.

[0007] Optionally, a first filter is provided between the static mixer and the decanter feed pump; the filter is a Lenz, Y-type, or T-type filter.

[0008] Optionally, the heat exchanger uses cooling water as the heat exchange medium and is equipped with a cooling water inlet pipe and a cooling water return pipe.

[0009] Optionally, a second filter is provided between the decanter and the decanter discharge pump; the filter is a Lenz, Y-type, or T-type filter.

[0010] Optionally, the decanter is equipped with multiple baffles to deflect the flow. The baffles between the heavy phase outlet and the light phase outlet of the decanter separate the lower part of the decanter, leaving an overflow channel only at the top of the decanter.

[0011] Optionally, a cyclone separator is provided inside the cyclone membrane filter near the feed inlet.

[0012] Optionally, a membrane tube is provided below the light phase outlet inside the cyclone membrane filter.

[0013] Optionally, the amide oil feed pipe and the benzene feed pipe are both equipped with flow meters and regulating valves; the cooling water return pipe of the heat exchanger is equipped with a thermometer and a regulating valve; the decanter is equipped with a level gauge, a liquid level gauge and a pressure gauge, and the heavy phase outlet is equipped with a regulating valve; the decanter discharge pump is equipped with a variable frequency motor; the cyclone membrane filter is equipped with a level gauge and a differential pressure sensor, and its heavy phase outlet is equipped with a regulating valve.

[0014] This utility model has the following beneficial effects:

[0015] The device provided by this utility model adds amide oil from the amide oil tank and benzene from the tank area to a static mixer in a certain proportion for thorough mixing. The addition of benzene reduces the solubility of ammonium sulfate in the amide oil. After mixing in the static mixer, the amide is filtered and sent to the cooler by the decanter feed pump after cooling to the decanter. The decanter is equipped with several separation baffles to further separate the ammonium sulfate mother liquor in the amide oil. The separated heavy phase ammonium sulfate mother liquor enters the ammonium sulfate mother liquor tank. The light phase amide oil is filtered and sent to the hydrocyclone membrane filter by the decanter discharge pump. The amide oil is separated from the residual ammonium sulfate mother liquor and ammonium sulfate particles by the high-efficiency hydrocyclone in the hydrocyclone membrane filter and sent to the ammonium sulfate mother liquor tank. The upper amide oil is filtered by the membrane tube at the top of the hydrocyclone membrane filter to intercept fine ammonium sulfate particles before being sent out of the device. The device includes steps such as benzene crystallization, filtration, cooling, decantation, re-filtration, cyclone separation, and membrane filtration to remove ammonium sulfate mother liquor and free ammonium sulfate particles from the amide oil, thereby improving the quality of the amide oil. The ammonium sulfate content in the amide oil can be reduced to below 0.5%wt. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of this utility model. Detailed Implementation

[0017] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that the following embodiments are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention.

[0018] like Figure 1 As shown, this utility model provides an apparatus for reducing the ammonium sulfate content in amide oil, including a static mixer 1, which is provided with an amide oil inlet pipe 1-1 and a benzene inlet pipe 1-2. The outlet 1-3 of the static mixer is connected to a decanter 4 after passing through a decanter feed pump 2 and a heat exchanger 3. The decanter is provided with a heavy phase outlet 4-1 and a light phase outlet 4-2. The light phase outlet is transported to a cyclone membrane filter 6 by a decanter discharge pump 5. The heavy phase outlet 6-1 of the cyclone membrane filter merges with the heavy phase outlet of the decanter and is connected to an ammonium sulfate mother liquor tank. The light phase outlet 6-2 of the cyclone membrane filter is connected to the subsequent amide oil purification process.

[0019] In some embodiments, a first filter 7 is further provided between the static mixer and the decanter feed pump; this filter is a Lenz, Y-type, or T-type filter. The filter accuracy is preferably 50 μm to 4 mm.

[0020] In some embodiments, the heat exchange medium of the heat exchanger is cooling water, and it is provided with a cooling water inlet pipe and a cooling water return pipe. The temperature of the amide oil discharged from the heat exchanger is preferably 50±5℃.

[0021] In some embodiments, a second filter 8 is provided between the decanter and the decanter discharge pump; this filter is a Lenz, Y-type, or T-type filter. The filter accuracy is preferably 20μm to 2mm.

[0022] In some embodiments, the decanter is provided with multiple baffles 4-3, and the baffles between the heavy phase outlet and the light phase outlet of the decanter separate the lower part of the decanter, leaving an overflow channel only at the top of the decanter.

[0023] In some embodiments, a cyclone separator 6-3 is provided near the feed inlet in the cyclone membrane filter. This separator is used to efficiently separate ammonium sulfate mother liquor and ammonium sulfate particles from the amide oil. The ammonium sulfate particles and mother liquor are discharged from the bottom heavy phase outlet and sent to the ammonium sulfate mother liquor tank.

[0024] In some embodiments, a membrane tube 6-4 is provided below the light phase outlet of the cyclone membrane filter. The membrane tube used is a high-flux metal membrane tube, ceramic membrane tube, or silicon carbide membrane tube, with a pore size of 50nm~10μm and an outer diameter of 15mm~50mm. The amide oil separated by cyclone separation is further separated into small ammonium sulfate particles in the amide oil through the membrane tube.

[0025] In a more preferred embodiment, a controller (such as a DCS controller) may also be provided. Flow meters and regulating valves are respectively installed on the amide oil inlet pipe and the benzene inlet pipe. The flow meter signal is input to the controller, which is electrically connected to the regulating valve to adjust the volume ratio of amide oil and benzene. A thermometer and regulating valve are installed on the cooling water return pipe of the heat exchanger. The thermometer signal is input to the controller, which is electrically connected to the regulating valve to adjust the temperature of the amide oil in the heat exchanger. A level gauge, a liquid level gauge (located on the amide oil side), and a pressure gauge are installed in the decanter, with the heavy phase discharged. The decanter outlet is equipped with a regulating valve, and the decanter discharge pump is equipped with a variable frequency motor. The signals from the interface level gauge, liquid level gauge, and pressure gauge are respectively sent to the controller. The signal output of the controller is electrically connected to the regulating valve and the variable frequency motor. The regulating valve at the heavy phase outlet adjusts the interface level inside the decanter, and the variable frequency motor at the decanter discharge pump adjusts the liquid level on the amide oil side. The cyclone membrane filter is equipped with an interface level gauge and a differential pressure sensor. Its heavy phase outlet is equipped with a regulating valve. The signals from the interface level gauge and differential pressure sensor are respectively sent to the controller. The controller is electrically connected to the regulating valve, and the regulating valve controls the interface level inside the cyclone membrane filter.

[0026] In a specific application example, when using the device provided by this utility model for production, the amide oil treatment flow rate is 40m³ / h. 3The ammonium sulfate content is 1.2%wt. The decanter feed filter uses a 250μm filter screen, and the decanter discharge filter uses a 48μm filter screen. The volume ratio of amide oil to benzene in the static mixer is controlled at 50:1. The amide oil outlet temperature in the heat exchanger is controlled at 42℃. The decanter interface is 45%, the amide oil level is 60%, the cyclone membrane filter interface is 45%, and the membrane tube accuracy is 2μm. The final ammonium sulfate content in the amide oil is 0.496%.

[0027] The above embodiments describe preferred embodiments of the present invention, but the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, including combining the various technical features in any other way. These simple modifications and combinations should also be considered as the content disclosed by the present invention and all fall within the protection scope of the present invention. Therefore, the protection scope of the present invention patent should be determined by the appended claims.

Claims

1. An apparatus for reducing the ammonium sulfate content in amide oil, characterized in that: It includes a static mixer with an amide oil inlet pipe and a benzene inlet pipe. The outlet of the static mixer is connected to the decanter via a decanter feed pump and a heat exchanger. The decanter has a heavy phase outlet and a light phase outlet. The light phase outlet is pumped to a hydrocyclone membrane filter via a decanter discharge pump. The heavy phase outlet of the hydrocyclone membrane filter merges with the heavy phase outlet of the decanter and is connected to the ammonium sulfate mother liquor tank. The light phase outlet of the hydrocyclone membrane filter is connected to the subsequent amide oil purification process.

2. The apparatus according to claim 1, characterized in that: A first filter is also provided between the static mixer and the decanter feed pump; this filter is a Lens, Y-type, or T-type filter.

3. The apparatus according to claim 1, characterized in that: The heat exchanger uses cooling water as its heat exchange medium and is equipped with a cooling water inlet pipe and a cooling water return pipe.

4. The apparatus according to claim 1, characterized in that: A second filter is also provided between the decanter and the decanter discharge pump; this filter is a Lenz, Y-type, or T-type filter.

5. The apparatus according to any one of claims 1 to 4, characterized in that: The decanter is equipped with multiple baffles to prevent flow. The baffles between the heavy phase outlet and the light phase outlet of the decanter separate the lower part of the decanter, leaving an overflow channel only at the top of the decanter.

6. The apparatus according to any one of claims 1 to 4, characterized in that: A cyclone separator is installed inside the cyclone membrane filter near the feed inlet.

7. The apparatus according to claim 6, characterized in that: A membrane tube is installed below the light phase outlet of the cyclone membrane filter.

8. The apparatus according to claim 7, characterized in that: Both the amide oil feed pipe and the benzene feed pipe are equipped with flow meters and regulating valves; the cooling water return pipe of the heat exchanger is equipped with a thermometer and a regulating valve; the decanter is equipped with a level gauge, a liquid level gauge and a pressure gauge, and the heavy phase outlet is equipped with a regulating valve; the decanter discharge pump is equipped with a variable frequency motor; the cyclone membrane filter is equipped with a level gauge and a differential pressure sensor, and its heavy phase outlet is equipped with a regulating valve.

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