NO<sub>x </sub>removal method
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Solution Overview
Problem
Existing methods for removing nitrogen oxides (NOx) from hydrocarbon-containing streams, particularly in low-temperature methane-molecular hydrogen separation systems, face challenges such as uncontrolled reactions of NOx gums and salts, leading to energy release and equipment safety concerns, and require improvements in removal efficiency and capacity.
Innovation Solution
A process involving NOx removal agents that operate at high space velocities (≥2.5×10^4 hr^-1) to remove ≥50% of NOx from hydrocarbon streams, using a combination of NOx and water removal agents in the same vessel, with partial regeneration of the agents to maintain efficiency and safety, thereby preventing NOx accumulation and reducing the formation of NOx gums and salts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional low-capacity adsorbents are used at low space velocity, then NOx removal efficiency is achieved, but run length before regeneration is limited and system productivity is reduced
Solution Approach 1:
The patent changes the key parameter of space velocity from low (conventional) to high (≥2.5×10^4 hr^-1), enabling the use of high-capacity adsorbents that can handle increased flow rates while maintaining NOx removal efficiency. This parameter change allows the system to process more gas volume per unit time before regeneration is needed, extending run length and improving productivity.
2Productivity
If higher space velocities are used, then system productivity and NOx removal capacity are improved, but the risk of uncontrolled reactions of NOx gums and salts increases
Solution Approach 1:
The patent applies preliminary action by removing NOx from the hydrocarbon-containing stream before the stream enters the low-temperature separation system where gums and salts could form. By preemptively removing NOx at high space velocities upstream, the system prevents the subsequent formation and accumulation of reactive NOx gums and salts that would otherwise pose safety risks in the cold box.
Solution Approach 2:
The patent introduces a high-capacity adsorbent as an intermediary substance between the NOx-containing stream and the low-temperature separation system. This adsorbent mediates the interaction by capturing NOx molecules through adsorption, preventing them from reaching conditions where they would react to form harmful gums and salts downstream.
3Reliability
If multiple separate removal agents are used for NOx and water, then removal effectiveness is achieved, but device complexity and operational difficulty increase
Solution Approach 1:
The patent applies universality by using a single high-capacity adsorbent that can simultaneously remove both NOx and water from the hydrocarbon-containing stream. This multi-functional adsorbent eliminates the need for separate removal agents and systems for NOx and water, simplifying the overall device structure and reducing operational complexity while maintaining effective removal of both contaminants.
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 process effectively reduces NOx levels to ≤5 ppbw, preventing uncontrolled reactions and ensuring safe operation of low-temperature separation systems, while maintaining the efficiency of hydrocarbon separation and extending the lifespan of equipment.
Implementation Method 1
U.S. Pat. No. 5,955,045 discloses a method for the selective chemisorption of NOx compounds
Implementation Method 2
U.S. Pat. No. 5,955,045 discloses a method for the selective chemisorption of NOx compounds
Implementation Method 3
vapor mixtures comprising molecular hydrogen and methane can be exposed to a relatively low temperature in order to condense a stream comprising at least a portion of the mixture's methane
Data Source
AI summary
The invention relates to mixtures comprising molecular hydrogen, hydrocarbons, and nitrogen oxides; to processes for removing at least a portion of the nitrogen oxides therefrom; to equipment useful in such processes; and to the use of such hydrocarbons for, e.g., chemical manufacturing.