An apparatus for mitigating butadiene polymer formation at low load in a butadiene apparatus

Abstract

The utility model provides a device for slowing down butadiene polymer generation under low load of butadiene device, through increasing the pipeline of butadiene product entering the light removal tower and water scrubbing tower on butadiene product line, butadiene medium feed load becomes larger, the flow rate in the tower becomes larger, the separation efficiency of tray is increased, the polymerization inhibition effect of polymerization inhibitor is increased, the operation parameter is close to the design optimal parameter, can effectively avoid high concentration butadiene on butadiene heavy removal tower lower section, butadiene water scrubbing tower, light removal tower butadiene polymer generation, avoid the butadiene polymer generation due to butadiene polymer generation causes the tray equipment blockage, causes the non - scheduled parking and butadiene polymer generation after the rise and crack equipment, lead to the flammable and explosive butadiene medium exudation caused by fire and explosion accident.

Description

Technical Field

[0001] This utility model belongs to the field of butadiene production technology, specifically relating to a device for slowing down the formation of butadiene polymer under low load in a butadiene plant. Background Technology

[0002] The butadiene unit uses acetonitrile extraction to produce butadiene. This involves using acetonitrile as a solvent and employing extractive distillation and rectification to separate butadiene from the C4 fraction, a byproduct of the ethylene unit. Besides butadiene, the C4 fraction contains various C3-C5 hydrocarbons such as butane, butene, and butyne. These components have similar boiling points and can form azeotropes. When acetonitrile is added to the separation system, the relative volatility difference between the components increases. A two-stage extractive distillation method is used to first remove butane and butene, then remove the C4-acetylenes, yielding crude butadiene. Further two-stage rectification removes the heavier components and propyne, producing the polymer-grade butadiene.

[0003] The specific process is as follows: industrial butadiene raffinate C4 is separated at the top of column T101A; acetonitrile and butadiene at the bottom of column T101B enter solvent stripping column T102; crude butadiene is collected at the top of column T102 and enters alkyne extractive distillation column T103; alkynes are separated off in the side stream of T102; crude butadiene without alkynes is obtained at the top of column T103; this part of the material enters the upper and lower sections of butadiene de-heavy column T201A / B; heavy components such as cis-butene are separated at the bottom of column T201B; crude butadiene with heavy butadiene components removed at the top of column T201A enters butadiene water washing column T301; after solvent acetonitrile is removed in T301, it enters light component removal column T202; at the top of column T202, light component propyne is separated and discharged to the flare; polymer-grade butadiene product is obtained at the top of the column.

[0004] Currently, the C4 feed load of the butadiene unit is below the lower limit of the unit's design feed load, resulting in the unit's designed production capacity not being utilized. High-concentration butadiene flows slowly and has a long residence time in T201A / B, T301, and T202. This prolonged residence time of high-concentration butadiene easily leads to butadiene polymer formation, clogging the equipment and causing production disruptions, thus requiring shutdown. Furthermore, butadiene polymers can easily rupture pipelines and equipment, causing butadiene leakage and potentially resulting in fire or explosion accidents.

[0005] Because the feed load design of the butadiene extraction unit is based on the output of mixed C4 by-products from the ethylene unit, changes in the feed composition of the ethylene unit may lead to insufficient mixed C4 output. Insufficient butadiene content in the mixed C4 will cause the butadiene feed load to the refining unit to be far lower than the unit's design load. This results in high reflux in the distillation system, low flow rate, long butadiene media residence time, and low contact efficiency of the polymerization inhibitor within the column. This makes it easy for butadiene polymers to form in the distillation system, leading to the unit's inability to operate normally. Therefore, it is necessary to avoid butadiene polymer formation caused by prolonged low-load feed to the butadiene unit. Utility Model Content

[0006] (a) Technical problems to be solved

[0007] This invention proposes a device to slow down the formation of butadiene polymers under low load conditions in a butadiene unit, thereby solving the technical problem of slow flow rate and long residence time in the distillation systems T201A / B, T301, and T202 during low-load feeding of the butadiene unit, which leads to the formation of butadiene polymers and causes unit shutdown.

[0008] (II) Technical Solution

[0009] To address the aforementioned technical problems, this utility model proposes a device for mitigating butadiene polymer formation under low load conditions in a butadiene unit. This device comprises: adding a pipeline between the butadiene product outlet line of the light-light removal tower and the heavy-light removal tower and butadiene washing tower; adding an automatic flow regulating valve for the heavy-light removal tower on the feed line of the newly added pipeline into the heavy-light removal tower, which regulates the flow rate of the butadiene product into the feed line of the heavy-light removal tower during low load operation; and adding an automatic flow regulating valve for the washing tower on the feed line of the newly added pipeline into the butadiene washing tower, which controls the flow rate of the butadiene product into the feed line of the butadiene washing tower during low load operation.

[0010] Furthermore, the automatic flow regulating valve of the de-weighting tower is equipped with a bypass valve, which is used when the automatic flow regulating valve of the de-weighting tower fails.

[0011] Furthermore, the automatic flow regulating valve of the water washing tower is equipped with a bypass valve, which is used when the automatic flow regulating valve of the water washing tower fails.

[0012] (III) Beneficial Effects

[0013] This invention proposes a device to mitigate butadiene polymer formation under low load conditions in a butadiene plant. By adding pipelines for butadiene products into the light weight removal tower and washing tower on the butadiene product line, the feed load of the butadiene medium is increased, the flow velocity inside the tower is increased, the separation efficiency of the trays is increased, and the polymerization inhibition effect of the polymerization inhibitor is enhanced. The operating parameters are close to the design optimal parameters, which can effectively prevent the formation of butadiene polymers in the upper and lower sections of the butadiene heavy weight removal tower, the butadiene washing tower, and the light weight removal tower due to high concentrations of butadiene. This avoids unplanned shutdowns caused by tray blockage due to butadiene polymer formation and equipment cracking after butadiene polymer formation, which could lead to fire and explosion accidents caused by the leakage of flammable and explosive butadiene medium. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the device for mitigating butadiene polymer formation under low load according to this invention.

[0015] In the diagram: 1-T201A / B heavy-weight removal tower; 2-Heavy-weight removal tower condenser; 3-T301 butadiene water washing tower; 4-T202 light-weight removal tower; 5-Light-weight removal tower condenser; 6-Butadiene product extraction line; 7-New pipeline; 8-Water washing tower automatic flow regulating valve; 9-Water washing tower automatic flow regulating valve bypass valve; 10-Heavy-weight removal tower automatic flow regulating valve; 11-Heavy-weight removal tower automatic flow regulating valve bypass valve; 12-Heavy-weight removal tower feed pipeline. Detailed Implementation

[0016] To make the objectives, contents, and advantages of this utility model clearer, the specific embodiments of this utility model will be described in further detail below with reference to the accompanying drawings and examples.

[0017] The present invention relates to a device for mitigating butadiene polymer formation under low load conditions in a butadiene unit. The reasons for butadiene polymerization under low load conditions and measures to prevent butadiene polymer formation are analyzed.

[0018] 1. Analysis of the reasons for butadiene polymerization in a butadiene unit under low load

[0019] The butadiene is fed into the unit at the lower limit of the designed feed load of C4. The butadiene medium has a low flow rate in the system, and the control temperature and control pressure are high, which provides good space for the formation of butadiene polymer.

[0020] Butadiene media has a low flow rate and long residence time in the distillation system. Once butadiene polymer seeds are formed, they are irreversible. Butadiene polymer seeds continuously trigger the formation of butadiene polymers, eventually leading to a large accumulation of polymers in the tower. This can cause blockages in equipment, pipelines, and trays, affecting normal vapor-liquid phase heat and mass transfer separation, resulting in substandard products or shutdowns. In severe cases, pipelines may burst and equipment may ignite or explode.

[0021] To maintain the balance of vapor and liquid phase materials in the tower, the reflux flow rate needs to be increased under low load conditions to meet the vapor-liquid phase balance and product quality requirements. As a result, the amount of steam used at the bottom of the tower and the amount of condensate at the top of the tower increase. Excessive reflux wastes the tower's designed separation efficiency and also increases the residence time of butadiene media in the tower, providing fertile ground for the formation of butadiene polymer seeds.

[0022] The faster flow rate of butadiene medium in the tower improves the contact efficiency of the polymerization inhibitor, allowing the inhibitor to better exert its polymerization inhibition effect.

[0023] 2. Analysis of measures to prevent butadiene polymer formation in butadiene units under low load: Crude butadiene from T103 enters the de-heavy component tower T201A. Heavy components are separated at the bottom of the de-heavy component tower, and butadiene containing light components is obtained at the top of the tower. It enters T301 to wash away acetonitrile and then enters tower T202. The light component propyne is discharged to the flare in the reflux tank at the top of the tower. Polymer-grade butadiene product with a purity of ≥99.5% is obtained at the bottom of the de-heavy component tower.

[0024] Based on the above analysis, this utility model adds a pipeline to the butadiene product outlet pipeline, which leads to T201A / B and T301 respectively. A flow control valve is installed on the pipeline. When the actual feed load is too low, the flow control valve is used to supplement the butadiene raw material, increasing the load in the T201A / B, T301, and T202 towers. This can effectively increase the butadiene flow rate, improve the tray separation efficiency, and avoid the formation of butadiene polymer.

[0025] like Figure 1 As shown, this embodiment proposes a device for mitigating butadiene polymer formation under low load conditions in a butadiene unit. The structure of this device is as follows:

[0026] Add a new pipeline 7 from the butadiene product extraction line 6 of T202 light tower 4 to T201A / B heavy tower 1 and T301 butadiene washing tower 3.

[0027] An automatic flow regulating valve 10 for the deweighting tower is added to the feed pipeline 12 of the new pipeline 7. When the load is low, the automatic flow regulating valve 10 can regulate the flow rate of butadiene product into the feed pipeline 12 of the deweighting tower.

[0028] The automatic flow regulating valve 10 of the deweight tower is equipped with a bypass valve 11, which is used when the automatic flow regulating valve 10 of the deweight tower fails.

[0029] An automatic flow regulating valve 8 is added to the feed pipeline of the new pipeline 7 into the T301 butadiene washing tower 3. When the load is low, the automatic flow regulating valve 8 can automatically control the flow rate of butadiene products entering the feed pipeline of the butadiene washing tower.

[0030] The automatic flow regulating valve 8 of the water washing tower is equipped with a bypass valve 9, which is used when the automatic flow regulating valve 8 of the water washing tower fails.

[0031] When the butadiene unit is below the lower limit of the mixed C4 design feed load, the high-purity butadiene from the top of the T201A / B heavy removal tower 1 changes from gaseous butadiene to liquid butadiene after passing through the heavy removal tower condenser 2. Similarly, the high-purity butadiene from the top of the T301 butadiene washing tower 3 and the T202 light removal tower 4 changes from gaseous butadiene to liquid butadiene after passing through the light removal tower condenser 5. The flow rate in the T202 light removal tower 4 is slow, the residence time of the high-concentration butadiene medium is long, and the contact rate of the polymerization inhibitor in the system is low, ultimately resulting in the formation of a large amount of butadiene polymer. By adding butadiene product into the feed line 12 of the de-weighting tower and the feed line into the T301 butadiene washing tower 3, and increasing the butadiene product flow rate of the T201A / B de-weighting tower 1 or the T301 butadiene washing tower 3 according to the actual operating conditions of the unit, or by simultaneously increasing the butadiene product flow rate of the T201A / B de-weighting tower 1 and the T301 butadiene washing tower 3, the generation of butadiene polymer caused by low-load feed of the butadiene unit can be overcome. This will effectively extend the operating time of the unit and avoid economic losses and safety hazards caused by polymer generation in the butadiene unit.

[0032] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present utility model, and these improvements and modifications should also be considered within the protection scope of the present utility model.

Claims

1. A device for mitigating butadiene polymer formation under low load conditions in a butadiene plant, characterized in that, The device for mitigating butadiene polymer formation under low load conditions in the butadiene unit comprises: adding a pipeline between the butadiene product outlet line of the light-light removal tower and the heavy-light removal tower and the butadiene washing tower; adding an automatic flow regulating valve for the heavy-light removal tower on the feed pipeline of the new pipeline into the heavy-light removal tower, which regulates the flow rate of butadiene product into the feed pipeline of the heavy-light removal tower during low load operation; and adding an automatic flow regulating valve for the washing tower on the feed pipeline of the new pipeline into the butadiene washing tower, which controls the flow rate of butadiene product into the feed pipeline of the butadiene washing tower during low load operation.

2. The apparatus for mitigating butadiene polymer formation under low load conditions in a butadiene unit as described in claim 1, characterized in that, The automatic flow regulating valve of the deweight tower is equipped with a bypass valve, which is used when the automatic flow regulating valve of the deweight tower fails.

3. The apparatus for mitigating butadiene polymer formation under low load conditions in a butadiene unit as described in claim 1, characterized in that, The automatic flow regulating valve of the water washing tower is equipped with a bypass valve, which is used when the automatic flow regulating valve of the water washing tower fails.

Images