Fired Heater Restriction Orifice Flow Distribution

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Solution Overview

Problem

Conventional fired heaters in hydrocarbon conversion processes face limitations due to maximum tube wall temperature constraints, leading to reduced production rates, metal-catalyzed coking, and non-uniform fluid distribution across heater tubes, which can result in costly upgrades and shutdowns.

Innovation Solution

The implementation of restriction orifices adjacent to the inlets of heater tubes in fired heaters to manage fluid flow distribution, allowing for increased throughput without exceeding maximum tube wall temperatures and reducing the risk of coking, while minimizing capital costs and shutdown time.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the firing of the heater is increased to raise throughput, then the production rate increases, but the tube wall temperature reaches its maximum limit

Engineering Contradiction:

Improveproduction rateVSAvoidtube wall temperature

Core Design Contradiction:

ProductivityVSTemperature

Solution Approach 1:

The patent applies local quality by installing restriction orifices at specific locations (inlet manifold or individual tube inlets) to create localized flow control. This ensures that tubes with higher heat flux or lower flow capacity receive restricted flow, while other tubes maintain higher flow rates, thereby distributing the thermal load more evenly and preventing any single tube from exceeding maximum wall temperature

Inventive Principle:

Principle #3Local quality

2Productivity

If the tube wall temperature is raised to increase throughput, then the production rate increases, but metal-catalyzed coking occurs in the fired heater tubes

Engineering Contradiction:

ImprovethroughputVSAvoidmetal-catalyzed coking

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent applies preliminary anti-action by proactively restricting fluid flow to specific tubes before coking can occur. The restriction orifices pre-establish flow distribution that prevents tubes prone to coking from reaching temperatures that would trigger metal-catalyzed coke formation, thereby preventing the harmful effect before it manifests

Inventive Principle:

Principle #9Preliminary anti-action

3Power

If the heater is enlarged with more tubes and/or burners to increase surface area, then the heat transfer capacity increases, but the cost increases

Engineering Contradiction:

Improveheat transfer capacityVSAvoidcost

Core Design Contradiction:

PowerVSEase of manufacture

Solution Approach 1:

The patent applies parameter changes by modifying the flow distribution parameters (via restriction orifices) rather than changing the physical size parameters (number of tubes or burners). This changes the operational parameters of the existing heater to achieve better heat transfer capacity without the capital cost of enlargement

Inventive Principle:

Principle #35Parameter changes

4Object-generated harmful factors

If sulfur is injected to inhibit coke formation, then coking is reduced, but reformer yields decrease

Engineering Contradiction:

Improvecoke formationVSAvoidreformer yields

Core Design Contradiction:

Object-generated harmful factorsVSProductivity

Solution Approach 1:

The patent uses restriction orifices as an intermediary device to control flow distribution and prevent coking, replacing the chemical intermediary (sulfur) with a mechanical intermediary. This intermediary approach achieves coke inhibition without the harmful side effect of reduced reformer yields

Inventive Principle:

Principle #24Intermediary (Mediator)

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 solution enables economic design and expansion of existing reforming units by correcting fluid distribution issues, reducing the risk of metal-catalyzed coking and allowing for increased feed rates without exceeding tube wall temperature limits, thereby enhancing the reliability and efficiency of hydrocarbon conversion processes.

Implementation Method 1

at least one restriction orifice adjacent to at least one heater tube inlet and in the fluid flow path from the manifold to the inlet

Methodology Applied

Scientific EffectFluid flow restriction: Pressure Drop

Implementation Method 2

at least one burner

Methodology Applied

Scientific EffectCombustion: Combustion

Implementation Method 3

an all radiant fired heating zone to heat the fluid

Methodology Applied

Scientific EffectThermal radiation: Thermal Radiation

Data Source

PatentUS8282814B2Fired heater for a hydrocarbon conversion process

Publication Date: 2012.10.09 UOP LLC

AI summary

One exemplary embodiment of the present invention can be a fired heater for a hydrocarbon conversion process. The fired heater includes inlet and outlet headers or manifolds, a set of heater tubes with each heater tube having an inlet and an outlet, at least one restriction orifice adjacent the inlet of at least one heater tube. The restriction orifice may be within the inlet manifold and adjacent the inlet of a heater tube, or between the inlet manifold and the inlet to the heater tube. A process may include passing a hydrocarbon stream through the fired heater described herein during the course of operating a hydrocarbon conversion process.