Quenching system of ethylene device
By installing a hydrocyclone separator on the reflux gasoline pipeline of the quenching oil tower and utilizing density difference and centrifugal force to separate the colloid, the scaling problem of the quenching oil tower was solved, and the long-term operation of the device and cost reduction were achieved.
Patent Information
- Application Number
- CN202422597070.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-25
- Publication Date
- 2025-09-05
- Estimated Expiration
- 2034-10-25
AI Technical Summary
The accumulation of styrene polymers in the quench oil tower in the ethylene plant leads to fouling of the tower trays, affecting normal production. The existing solution increases costs and has limited effectiveness.
A hydrocyclone separator is installed on the reflux gasoline pipeline of the quenching oil tower. The density difference between the colloid and the gasoline is used to separate the denser colloid and coke powder to the bottom through centrifugal force, thereby removing the colloid in the reflux gasoline and preventing scaling.
Effectively remove colloids from reflux gasoline, extend the operating cycle of the quench oil tower, and reduce the operating costs of the device.
Smart Images
Figure CN223299963U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the field of ethylene production, and more specifically to a quenching system of an ethylene device. Background Art
[0002] The quenching system in the ethylene unit is located at the junction of the cracking furnace and the separation system. It is mainly composed of a quenching oil tower, a quenching water tower, a process water recovery system, etc. It is responsible for the initial fractionation of ethylene cracking gas. Its main purpose is to achieve pre-fractionation of oil products, recovery of lower-grade heat, and recycling of process water.
[0003] During normal operation of the quench tower in an ethylene plant, the pyrolysis gasoline separated from the quench water tower is used as reflux to control the tower's top temperature. Because the pyrolysis gas contains large amounts of styrene, phenylacetylene, and other unsaturated hydrocarbons, these compounds polymerize under the high temperatures of the quench tower, forming polystyrene-like colloids. These colloids largely dissolve in the pyrolysis gasoline and return to the top of the quench tower as reflux, forming scale on the tower's upper trays, clogging them and increasing pressure, impacting normal plant production. In particular, with the increasing use of lighter pyrolysis feedstocks and the resulting decrease in heavy pyrolysis gasoline production, the resulting colloids accumulate in the reflux system, making them more susceptible to quench tower upper tray scaling.
[0004] The most common solution to quench tower fouling caused by styrene polymers is to add a polymerization inhibitor to the gasoline reflux to reduce styrene polymer formation. However, due to the high styrene content in the reflux gasoline, averaging around 4-6%, as the reflux liquid descends, styrene and heavier hydrocarbons evaporate below trays 8-10, concentrating at even higher concentrations. This produces more styrene polymers. Some of this polymer colloid falls back into the bottom fraction, while others accumulate in the pyrolysis gasoline after exiting the top of the tower. Consequently, the colloid content in the reflux gasoline remains high. Due to its high viscosity, the colloid easily adheres to the trays, forming a scale-like substance that can clog the tray apertures or downcomers, ultimately affecting the proper operation of the quench tower. Therefore, in addition to the polymerization inhibitor, quench towers typically require the addition of a dispersant to break up the accumulated scale into small pieces that gradually fall to the bottom fraction, where it is removed from the bottom feed.
[0005] Another solution to reduce quench tower fouling is to add diluent to the gasoline reflux system. Due to the lighter feedstock, the production of heavy pyrolysis gasoline (primarily composed of cracked C9+) decreases. This leads to higher concentrations of styrene and styrene polymers in the pyrolysis gasoline. To reduce the styrene concentration and remove the accumulated styrene polymers, hydrocracked C9 is used as a diluent. However, the use of this diluent significantly increases the unit's operating costs. Assuming 2 tons / h of diluent is used, the direct cost increases by 2,000 RMB / h.
[0006] In view of the shortcomings of the above-mentioned traditional solutions of adding chemical inhibitors and adding diluents in process production, the present application hopes to propose a new solution to prevent scaling of the quenching oil tower. Utility Model Content
[0007] Therefore, the present application provides a quenching system for an ethylene plant, comprising a quenching oil tower and a quenching water tower. The quenching oil tower is characterized in that a vapor phase discharge pipeline and a reflux gasoline pipeline are provided at the top of the quenching oil tower. The quenching oil tower is connected to the quenching water tower via the vapor phase discharge pipeline. Furthermore, the reflux gasoline pipeline, which is used to transport pyrolysis gasoline from the quenching water tower, is drawn from the bottom of the quenching water tower and is sequentially connected to a gasoline reflux pump and a hydrocyclone. The pyrolysis gasoline produced by the quenching water tower is separated into two branches after passing through the gasoline reflux pump. One branch passes through the hydrocyclone, with the portion exiting the top of the hydrocyclone returning to the top of the quenching oil tower as reflux gasoline. The heavy component separated from the bottom of the hydrocyclone returns to the bottom of the quenching oil tower. The other branch can be connected to a gasoline stripping tower.
[0008] In some examples, a quenching oil discharge pipeline is provided at the bottom of the quenching oil tower, and a branch pipeline is provided on the quenching oil discharge pipeline. The branch pipeline is connected to the quenching oil pump and then connected to the quenching oil tower at the quenching oil reflux position to form a quenching oil circulation loop.
[0009] In some examples, the quench oil reflux location is above the quench oil tower bottom.
[0010] The quenching system of this application installs a hydrocyclone on the reflux gasoline pipeline of the quenching oil tower. This system utilizes the different densities of the colloids and reflux gasoline, which accumulate in the reflux gasoline. By using the hydrocyclone, the denser colloids and coke powder in the gasoline are thrown toward the wall by centrifugal force and flow down the wall in a spiral line to the bottom outlet (underflow) of the hydrocyclone. The clarified, colloid-free gasoline liquid rises and overflows from the top outlet, thereby removing the colloids from the reflux gasoline and preventing colloid fouling in the quenching oil tower. The quenching oil tower of this application can effectively remove colloids from the reflux gasoline, ensuring the long-term operation of the ethylene plant. BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Figure 1 Schematic diagram of a quenching system according to one embodiment of the present invention. DETAILED DESCRIPTION
[0012] A quenching system according to an embodiment of the present application is described below with reference to the accompanying drawings.
[0013] Figure 1 FIG1 shows a simplified structural diagram of a quenching system according to an embodiment of the present invention. Figure 1 As shown, in one embodiment of the present invention, a vapor discharge pipeline 2 and a reflux gasoline pipeline 3 are provided at the top of the quench oil tower 1. The vapor discharge pipeline 2 is connected to a quench water tower 4. The reflux gasoline pipeline 3 is drawn from the bottom of the quench water tower 4 to transport pyrolysis gasoline from the quench water tower 4. The reflux gasoline pipeline 3 is sequentially connected to a gasoline reflux pump 6 and a hydrocyclone 5 before reaching the top of the quench oil tower 1. The pyrolysis gasoline produced by the quench water tower 4 is separated into two branches after passing through the gasoline reflux pump 6. One branch passes through the hydrocyclone 5. The portion exiting the top of the hydrocyclone is returned to the top of the quench oil tower via the reflux gasoline pipeline 3 as reflux gasoline. The heavy component separated from the bottom of the hydrocyclone is returned to the bottom of the quench oil tower via pipeline 7. The other branch can be connected to a gasoline stripping tower (not shown) via pipeline 11.
[0014] In some embodiments, a quench oil discharge line 8 is provided at the bottom of the quench oil tower 1. A branch line 9 is provided on this quench oil discharge line 8. This branch line is connected to a quench oil pump 10 and then to the quench oil tower at the quench oil return point, forming a quench oil circulation loop. In some embodiments, the quench oil return point is higher than the quench oil tower kettle. In some embodiments, the discharged quench oil can be used as fuel oil.
[0015] like Figure 1 As shown, the process for pyrolysis gas entering the quench oil tower of an ethylene plant is as follows: pyrolysis gas is fed from the bottom into quench oil tower 1. After cooling and separation, the overhead light fraction distillate, including gasoline, flows through vapor phase discharge line 2 to quench water tower 4, where it undergoes further condensation and separation. The separated pyrolysis gasoline flows from the bottom of the quench water tower through gasoline reflux pump 6, and a large portion enters hydrocyclone 5. The clean gasoline separated by hydrocyclone 5 is then returned to the top of the quench oil tower via reflux gasoline line 3 as reflux gasoline. The separated heavier colloids and entrained heavy components, such as coke powder, are returned to the bottom of quench oil tower 1 via line 7. A portion of the quench oil at the bottom of quench oil tower 1 enters the quench oil circulation loop to maximize heat recovery, while the remaining portion enters the stripping tower.
[0016] With the quench oil tower device of the utility model, the pyrolysis gasoline produced by the quench water tower kettle is output through a gasoline reflux pump and then passes through a hydrocyclone. Utilizing the different centrifugal forces of different components, the denser colloid (density: about 1.0 kg / L) and entrained coke powder in the gasoline are separated from the bottom of the hydrocyclone and returned to the quench oil tower kettle (maintaining at least 1 t / h of bottom material). The clean gasoline without colloid exiting the top of the hydrocyclone serves as the quench oil tower reflux. The hydrocyclone separation can significantly reduce the colloid in the pyrolysis gasoline reflux, thereby effectively slowing down the fouling of the quench oil tower tray and thereby extending the operating cycle of the quench oil tower.
[0017] The quench oil tower according to the present application has been described above with reference to the embodiments and illustrations. These embodiments and illustrations provide some exemplary implementations and do not indicate that the included features are preferred or essential features of the quench oil tower according to the present application. Persons skilled in the art may modify and vary the described embodiments without departing from the teachings of the present application.
Claims
1. A quenching system for an ethylene plant, comprising a quenching oil tower and a quenching water tower, characterized in that: A gas phase discharge pipeline and a reflux gasoline pipeline are provided at the top of the quenching oil tower. The gas phase discharge pipeline is connected to the quenching water tower. The reflux gasoline pipeline is extracted from the bottom of the quenching water tower and is sequentially connected to a gasoline reflux pump and a hydrocyclone. The pyrolysis gasoline produced by the quenching water tower is divided into two branches after passing through the gasoline reflux pump. One branch passes through the hydrocyclone, and the portion coming out of the top of the hydrocyclone is returned to the top of the quenching oil tower as reflux gasoline. The portion separated from the bottom of the hydrocyclone is returned to the kettle of the quenching oil tower. The other branch is connected to the gasoline stripping tower.
2. The quenching system of the ethylene device according to claim 1, characterized in that: A quenching oil discharge pipeline is provided at the bottom of the quenching oil tower, and a branch pipeline is provided on the quenching oil discharge pipeline. The branch pipeline is connected to the quenching oil pump and then connected to the quenching oil tower at the quenching oil reflux position to form a quenching oil circulation loop.
3. The quenching system of the ethylene device according to claim 2, characterized in that: The quenching oil reflux position is higher than the quenching oil tower kettle.