Fluidized Catalytic Reactor Startup Heating to Reduce Catalyst Loss
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Solution Overview
Problem
Existing fluidized bed paraffin dehydrogenation reactors face significant catalyst loss during startup due to insufficient volumetric flow rates, which are critical for effective gas-solid separation in cyclones, leading to operational difficulties and catalyst loss.
Innovation Solution
A start-up process utilizing a start-up heater to heat the feed stream to at least 240°C, maintaining a critical volumetric flow rate of at least 60% of the design flow rate, ensuring sufficient gas velocity for cyclone operation and catalyst transport.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the reactor is operated at low temperature during startup, then the heating requirement is reduced, but the volumetric flow rate drops below the critical rate required for effective cyclone separation
Solution Approach 1:
The feed stream is preheated in a heat exchanger using hot effluent before entering the reactor. This preliminary heating action ensures that the feed achieves sufficient temperature and volumetric flow rate to maintain critical cyclone separation velocity, preventing catalyst loss during the startup phase when reactor temperature is still low.
2Loss of substance
If auxiliary feed streams such as steam are added to increase volumetric flow rate, then catalyst loss is reduced, but utilities requirements and plant complexity increase significantly
Solution Approach 1:
The system uses the hot effluent stream, which is already present in the process, to preheat the feed stream through a heat exchanger. This self-service approach utilizes existing process streams to achieve the necessary temperature increase and volumetric flow rate, avoiding the need for additional auxiliary feeds like steam and the associated utilities infrastructure.
3Loss of substance
If the feed flow rate is increased to maintain critical cyclone velocity at low temperature, then catalyst separation is improved, but the energy required to heat the feed increases
Solution Approach 1:
The heat exchanger creates a feedback loop where hot effluent from the reactor continuously preheats the incoming feed stream. This feedback mechanism recovers thermal energy from the process output and applies it to the process input, reducing the net energy requirement for heating while maintaining the feed flow rate necessary for effective catalyst separation.
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
Minimizes catalyst loss during reactor startup by maintaining the necessary flow rates and fluidization, allowing effective gas-solid separation and reducing operational challenges.
Implementation Method 1
A start-up process utilizing a start-up heater to heat the feed stream to at least 240°C
Implementation Method 2
a critical volumetric flow rate of the vapor (gas) is required to enable catalyst recovery in cyclones
Implementation Method 3
Fluidized-bed paraffin dehydrogenation is designed to operate at low pressure
Data Source
AI summary
A fluidized catalytic reactor connected to a start-up heater is provided. The start-up heater provides sufficient heat to a catalyst containing stream to gradually increase the feed temperature. This allows for a critical volumetric flow rate to be achieved so that catalyst can be recovered from product instead of being entrained in product.