Gravity Separator Design for Coke Particle Removal in Quench Columns
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Solution Overview
Problem
The existing methods for separating coke particles from the water phase in olefin plants require large, costly infrastructure due to the need for extensive residence time and high quench water usage, leading to inefficient use of space and increased structural expenditure.
Innovation Solution
The process involves taking the water phase off from the scrubbing water column predominantly from a point above the column bottom, allowing the bottom phase region to act as a gravity separator, thereby reducing the size and height of subsequent gravity separators and eliminating the need for the scrubbing water column to be positioned above the first gravity separator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the water phase is taken off from the column bottom and passed to large multistage settling tanks, then sufficient residence time is achieved for complete particle separation, but the plant requires very large diameter and length with high structural expenditure
Solution Approach 1:
The patent divides the settling process into two distinct stages: a first settling tank for removing the majority of solid particles from the water phase, and a second settling tank for polishing and removing remaining particles. This segmentation allows each tank to be more compact while achieving the same overall separation efficiency, thereby reducing the total volume and structural expenditure required.
Solution Approach 2:
The invention introduces a preliminary settling stage in the first settling tank where the bulk of particle removal occurs before the water phase enters the second settling tank. This preliminary action removes the majority of solids upfront, allowing the second tank to be smaller and more efficient, thus reducing the overall plant footprint and structural requirements.
2Ease of operation
If the scrubbing water column is positioned above the first gravity separator, then gravity flow is maintained, but the overall plant height increases significantly
Solution Approach 1:
The patent repositions the first settling tank laterally adjacent to the scrubbing water column rather than positioning it vertically below. This dimensional change from vertical stacking to horizontal arrangement maintains gravity-driven flow while significantly reducing the overall plant height, allowing for more compact plant design and reduced structural expenditure.
3Reliability
If large amounts of quench water are applied to the scrubbing water column, then effective cooling and purification of cracked gas is achieved, but the volume of water phase requiring separation increases
Solution Approach 1:
The two-stage settling system efficiently handles the increased water phase volume resulting from large quench water application. The first settling tank processes the bulk volume and removes most particles, while the second tank handles the reduced flow with higher separation precision. This segmented approach manages the increased water volume effectively while maintaining cooling and purification efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for a smaller multistage settling tank and reduced overall plant height, decreasing structural expenditure while maintaining separation efficiency, and enables joint processing of heavy water phases from both the scrubbing water column and settling tank.
Implementation Method 1
allowing the bottom phase region to act as a gravity separator
Implementation Method 2
the cracked gas is simultaneously cooled and scrubbed by the contact with water
Implementation Method 3
the solid coke particles are scrubbed out of the cracked gas by the quench water in the scrubbing water column
Data Source
AI summary
The invention relates to a process for separating off solid particles, in particular coke particles, from a water phase by means of gravity in a plant for generating hydrocarbons by cracking a hydrocarbonaceous feed, and also to a device for carrying out the process. In contrast to the prior art, the water phase is taken off predominantly from a point above the column bottom B via the outlet A. The first gravity separator 2 which is constructed as a multistage settling tank 2 is situated not beneath, but next to, the scrubbing water column 1. The bottom phase of the scrubbing water column 1 already acts as a part of the first gravity separator 2. Thus, via the outlet 5 in the column bottom B, a heavy water phase which is loaded with coke particles is already taken off and passed into the second gravity separator 3. This heavy water phase is further treated, together with the heavy water phase which is loaded with coke particles from the recesses 6 of the multistage settling tank 2. In this embodiment of the invention, the feed rate into the multistage settling tank 2 need not be controlled as in the prior art. The multistage settling tank 2 and the bottom phase of the quench column 1 form a communicating liquid system in which the same level of the water phase is established.