Pilot Plant Semi-Condensing Polymerization Process
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Solution Overview
Problem
Pilot plant reactors are unable to operate in condensed mode, limiting their ability to mimic commercial gas phase polymerization processes, which poses risks and challenges when scaling up new catalysts or polyolefin products, as they lack the capability to study the effects of condensed liquids on a small scale.
Innovation Solution
A process is developed to test commercial polyolefin condensed mode operation on a pilot plant scale by flowing olefin monomers and inert fluids into a fluidized bed reactor, with a cycle gas stream being compressed and cooled to create a gas-liquid mixture, which is then returned to the reactor, mimicking commercial reactor conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pilot plant reactors operate at small scale with limited heat removal systems, then capital costs and operational risks are reduced, but the ability to mimic commercial condensed mode operation is lost
Solution Approach 1:
The cycle gas stream is divided into two separate streams: a main stream that bypasses the secondary cooler and a side stream that is cooled to condense mode temperatures. This segmentation allows the pilot plant to simulate condensed mode operation without requiring the entire system to operate at commercial-scale heat removal rates, thus maintaining reliability of mimicry while respecting productivity limitations.
Solution Approach 2:
The temperature parameter of a portion of the cycle gas stream is changed by cooling it below the dew point in the secondary cooler, transforming it from a gas-only stream to a gas-liquid mixture. This parameter change enables the pilot plant to replicate the condensed mode conditions of commercial reactors, allowing reliable simulation of fouling and gel formation phenomena.
2Reliability
If pilot plant reactors operate without condensed mode capability, then operational simplicity is maintained, but capital and safety risks increase when scaling up new catalysts or products
Solution Approach 1:
The cooling system is segmented into a primary cooling path (main cycle gas stream) and a secondary cooling path (side stream through secondary cooler). This segmentation allows the system to gain condensed mode capability without requiring complete redesign of the entire cooling system, thus reducing device complexity while improving safety and reliability for scale-up studies.
Solution Approach 2:
The secondary cooler acts as an intermediary device that introduces condensed mode conditions into otherwise a gas-phase system. By adding this intermediate cooling stage, the pilot plant can study fouling and gel formation without requiring complete redesign of the base reactor system, balancing enhanced capability with acceptable complexity.
3Reliability
If the entire cycle gas stream is cooled to condense mode temperatures, then condensed liquid effects are maximized, but energy consumption and system complexity increase
Solution Approach 1:
Instead of cooling the entire cycle gas stream to condense mode temperatures, only a portion (side stream) is cooled to the required temperature. The main stream bypasses the secondary cooler and mixes with the condensed side stream. This partial action achieves the necessary condensed liquid effects for reliable simulation while significantly reducing energy consumption compared to cooling the full flow.
Solution Approach 2:
Condensed mode conditions are applied locally to a side stream rather than uniformly to the entire cycle gas. This localized application of cooling creates gas-liquid mixture zones within the reactor where needed, maintaining reliable simulation of fouling and gel formation while minimizing overall energy consumption by avoiding unnecessary cooling of the full gas stream.
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 the generation of condensed liquids on a small scale, enabling the study of fouling and gel formation, thereby reducing capital and safety risks associated with scaling up new catalysts and products, and providing a cost-effective analytical tool for troubleshooting commercial operations.
Implementation Method 1
The cycle gas stream can be compressed to a pressure above the reaction pressure within the housing
Implementation Method 2
the side stream can be cooled to a temperature that is below its dew point to create a gas-liquid mixture
Implementation Method 3
The one or more olefin monomers can be contacted with one or catalysts within the fluidized bed at conditions sufficient to produce a polyolefin
Implementation Method 4
gas phase polyolefin polymerization
Implementation Method 5
a gaseous stream containing one or more monomers is passed through a fluidized bed
Data Source
AI summary
A process for testing a commercial polyolefin condensed mode operation on a pilot plant scale is provided. A feed stream including one or more olefin monomers and one or more inert fluids can be introduced to a fluidized bed contained within a reactor housing having a length to diameter ratio of 1.0 to 20. The one or more olefin monomers can be contacted with one or catalysts within the fluidized bed at conditions sufficient to produce a polyolefin. A cycle gas stream can be withdrawn from the housing, the cycle gas stream having a gas velocity of 1.0 ft/sec to 3.0 ft/sec and including the unreacted monomers and the inert fluids. The cycle gas stream can be compressed to a pressure above the reaction pressure within the housing. The cycle gas stream can be cooled to a temperature that is above the dew point of the cycle gas, and a portion of the compressed cycle gas stream can be removed to create a side stream of the compressed cycle gas stream. The side stream can be cooled to a temperature that is below its dew point to create a gas-liquid mixture, and the cycle gas stream and the cooled side stream including the gas-liquid mixture can be returned to the reactor housing.