Ejector Block Burner System for Low-NOx Steam Cracking
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Solution Overview
Problem
Conventional steam cracking furnaces face challenges with increasing NOx emissions, which are exacerbated by the need to increase firebox dimensions to comply with emission regulations, leading to higher capital costs and reduced furnace efficiency.
Innovation Solution
A burner system for a steam cracking furnace that incorporates an ejector block to recirculate flue gas within the firebox, reducing adiabatic flame temperature through intense premixing of flue gas with fuel and oxidant, thereby minimizing NOx production without enlarging the firebox dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If firebox dimensions are increased to reduce NOx emissions, then NOx production is minimized, but capital cost increases
Solution Approach 1:
The patent changes the temperature parameter by introducing flue gas recirculation to lower the adiabatic flame temperature. This allows achieving low NOx emissions without increasing firebox dimensions, as the chemical parameter (temperature) is modified rather than the physical dimension
Solution Approach 2:
Flue gas acts as an intermediary substance that is recirculated back into the combustion zone. This mediator absorbs excess heat and lowers the flame temperature, reducing NOx formation without requiring larger firebox volume
2Object-generated harmful factors
If adiabatic flame temperature is reduced to minimize NOx production, then NOx emissions decrease, but combustion efficiency may be affected
Solution Approach 1:
The system dynamically adjusts the flue gas recirculation rate to optimize the balance between temperature control and combustion efficiency. The ejector block creates a dynamic recirculation flow that adapts to operating conditions, maintaining efficient combustion while limiting peak temperatures
Solution Approach 2:
The combustion process utilizes periodic mixing zones where fuel, oxidant, and recirculated flue gas interact in staged combustion zones. This periodic mixing pattern allows complete combustion to occur while maintaining lower average temperatures that reduce NOx formation
3Loss of energy
If side wall burners are removed to increase furnace fuel efficiency, then fuel efficiency improves, but heat distribution may be affected
Solution Approach 1:
The combustion system is segmented into multiple zones: primary combustion zone, flue gas recirculation zone, and secondary mixing zone. This segmentation allows efficient fuel combustion in the primary zone while using recirculated flue gas in subsequent zones to maintain stable heat distribution without side wall burners
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
The burner system effectively reduces NOx emissions by lowering adiabatic flame temperature, enhancing combustion efficiency, and maintaining furnace capacity while minimizing capital costs.
Implementation Method 1
The ejector block is located within the radiant section, such that the ejector block, in combination with a high velocity jet of propellant, can provide a certain amount of suction
Implementation Method 2
the ejector block, in combination with a high velocity jet of propellant, can provide a certain amount of suction on for example flue gas in the firebox
Implementation Method 3
Flue gas generated in the combustion zone of the firebox is drawn back into the burner system via the ejector block generating a recirculating flue gas flow
Implementation Method 4
The main effect of flue gas recirculation is that it reduces an adiabatic flame temperature in the firebox, the adiabatic flame temperature being the temperature of the flue gas produced by the combustion before it releases any heat to its environment. This is due to an intense premixing of flue gas with fuel and/or oxidant at relatively low temperature, prior to the final combustion.
Implementation Method 5
In the radiant coil the hydrocarbon feedstock is quickly heated up to the point where the pyrolysis reaction starts and the hydrocarbon feedstock is converted into products and by-products
Implementation Method 6
The waste heat in the cracked gas can be recovered in at least one transfer line exchanger and can be used to generate saturated high pressure (HP) steam. This steam may be generated from boiler water coming from a steam drum. In the transfer line exchanger the boiler water is partly vaporized.
Implementation Method 7
The waste heat from the flue gas is recovered in the convection section using various types of convection banks. Part of the heat is used for the process side, the preheat and/or evaporation of the hydrocarbon feed and the dilution steam
Data Source
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AI summary
Burner system for a radiant section of a steam cracking furnace configured to provide heat to the radiant section, the burner system including a fuel inlet and an oxidant inlet, and further comprising an ejector block arranged located within the radiant section and to receive a propellant and a propelled fluid and arranged to premix said propellant with said propelled fluid.