Catalyst Injection Device for Fluidized Bed Fouling Prevention
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Solution Overview
Problem
Existing processes for injecting catalysts into gas-phase fluidized beds face issues with blocking and fouling due to the presence of fines and components in cooled recycle process gas, which is not ideal for catalyst introduction.
Innovation Solution
A process using an injection device with specific dimensions for the inner and outer tubes, employing a carrier gas and a shielding gas with controlled linear velocities and mass flow rates, where the shielding gas is primarily composed of hydrocarbons like ethylene, to ensure effective catalyst introduction without using cooled recycle process gas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If cooled recycle process gas is used as shielding gas, then the injection device is readily available and convenient to operate, but the presence of fines and other components causes blocking of the injection device and/or fouling
Solution Approach 1:
The invention extracts and removes the harmful components (fines and other blocking components) from the gas stream before it reaches the injection device. This is achieved by introducing fresh gas that does not contain these contaminants, thereby preventing blocking and fouling of the injection device while maintaining the shielding function.
Solution Approach 2:
The invention introduces a fresh gas stream as an intermediary medium to replace the contaminated recycle process gas. This fresh gas acts as a clean carrier and shielding gas that does not contain fines or other components that would cause blocking, thereby protecting the injection device while maintaining the necessary gas flow for catalyst introduction.
2Reliability
If high flows of monomer are used in injection devices, then shielding of catalyst is achieved, but the gas consumption increases significantly
Solution Approach 1:
The invention changes the parameters of the gas flow by using fresh gas with controlled flow rates instead of high monomer flows. The linear velocity and mass flow rate parameters are optimized to provide adequate shielding while minimizing gas consumption. The fresh gas is introduced at specific velocities that maintain catalyst shielding without requiring excessive gas volumes.
Solution Approach 2:
The invention applies shielding gas locally at the injection point rather than using high flows throughout the reactor. The fresh gas is introduced specifically at the injection device to provide localized shielding where it is most needed, reducing overall gas consumption while maintaining effective catalyst protection during introduction.
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 minimizes the risk of agglomerate formation and maintains stable operation by reducing the flow rate of shielding gas, ensuring catalyst particles penetrate the fluidized bed sufficiently to avoid fouling, thereby extending reactor operation time and increasing production rates without the drawbacks of using recycle process gas.
Implementation Method 1
passing said polymerisation catalyst and a carrier gas through the inner tube and into the gas-phase fluidised bed at a linear velocity of said carrier gas of 4 to 14 m/s
Implementation Method 2
passing a shielding gas through the outer tube and into the gas-phase fluidised bed at a linear velocity of said shielding gas of 1 to 10 times the linear velocity of the carrier gas through the inner tube
Implementation Method 3
gas-phase fluidised bed
Data Source
AI summary
Process for introducing a solid polymerization catalyst into a gas-phase fluidized bed using an injection device having an inner tube of internal cross-sectional area of 10 to 100 mm2 and an outer tube forming an annulus around the inner tube with a cross-sectional area of 1 to 10 times the internal cross-sectional area of the inner tube. The polymerization catalyst and a carrier gas are passed through the inner tube and into the gas-phase fluidized bed at a carrier gas linear velocity of 4 to 14 m/s and a carrier gas mass flow rate of 10-35 kg/h. A shielding gas is passed through the outer tube and into the gas-phase fluidized bed at a linear velocity of 1 to 10 times the carrier gas linear velocity through the inner tube and at a mass flow rate of 100-500 kg/h. No cooled recycle process gas is provided to the injection device.