Methane Oxidation Reactor Temperature Control via Heat Recovery
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Solution Overview
Problem
Existing methods for removing methane from coal mine ventilation gas with low concentrations face challenges such as safety concerns due to the need for temperature control in oxidation processes, catalyst degradation, and fluctuations in methane concentration, which can lead to inefficient operation and safety risks.
Innovation Solution
A method involving the optional mixing of feed gas with make-up methane or air, heating through a heat exchanger, oxidation in a reactor with a catalyst, and heat recovery, with controlled inlet and outlet temperatures to maintain optimal operating conditions and extend catalyst life, while accommodating fluctuations in methane concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the gas is heated to high temperature for oxidation reaction, then the oxidation reaction occurs efficiently, but the catalyst may be damaged or deactivated
Solution Approach 1:
The patent applies parameter changes by implementing a two-stage temperature control strategy: preheating the gas to an initial temperature (first parameter change) before oxidation, then controlling the temperature to remain below a second threshold during the oxidation reaction. This dynamic parameter adjustment enables efficient methane oxidation while preventing catalyst damage from excessive temperatures.
2Duration of action of stationary object
If the temperature is controlled to protect the catalyst, then the catalyst life is extended, but the oxidation reaction may not occur efficiently
Solution Approach 1:
The patent applies preliminary action by preheating the ventilation gas to a specific temperature range (50-150°C, preferably 80-120°C) before the gas contacts the catalyst in the oxidation reactor. This preheating step ensures the gas reaches the optimal temperature for oxidation reaction when it enters the reactor, while the reactor temperature is simultaneously controlled to stay below the catalyst damage threshold, thus achieving both efficient reaction and catalyst protection.
3Productivity
If the ventilation gas is concentrated to increase methane content, then the methane recovery efficiency improves, but the gas concentration passes through the explosion limit creating safety risks
Solution Approach 1:
The patent converts the harmful low-concentration methane in ventilation gas into a beneficial resource by using catalytic oxidation to transform methane into carbon dioxide and water. Instead of concentrating the methane (which would create explosion risks), the system directly oxidizes the methane at low concentrations, turning the previously harmful greenhouse gas into useful heat energy and safe combustion products, thus eliminating the need for dangerous concentration steps.
4Productivity
If the gas flow rate is increased to handle high methane concentration, then the processing capacity improves, but the temperature control becomes more difficult
Solution Approach 1:
The patent applies feedback control by continuously monitoring the temperature in the oxidation reactor and adjusting the gas flow rate and preheating temperature accordingly. When the reactor temperature approaches the catalyst damage threshold, the system reduces the gas flow rate or preheating temperature to maintain safe operating conditions. This feedback mechanism enables the system to handle varying gas flow rates while maintaining stable temperature control and protecting the catalyst.
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 method effectively oxidizes methane to carbon dioxide and water, maintains catalyst longevity, and safely manages temperature fluctuations, ensuring efficient methane removal from low-concentration gas streams without exceeding safe operational temperatures.
Implementation Method 1
passing the feed gas and optional make-up gas through a heat exchanger to raise the temperature of the gas to the desired inlet temperature T1 of an oxidation reactor
Implementation Method 2
passing the gas stream removed in step (d) through the heat exchanger against the reactor stream from step (b) to allow the heat to be recovered from the gas stream removed in step (d) and utilised to heat the reactor stream in step (b)
Implementation Method 3
passing the heated stream from step (b) to the oxidation reactor containing an oxidation catalyst, where the methane is oxidised
Implementation Method 4
the methane is oxidised to carbon dioxide and water
Implementation Method 5
removing a gas stream including the products of the oxidation reaction from the reactor, said gas stream being at an outlet temperature T2 which is higher than the inlet temperature T1
Data Source
AI summary
In a method for removing methane from feed gas having a methane concentration of 2 mole % or less, the feed gas is optionally mixed with make-up methane or air and passed through a heat exchanger to heat the gas to an oxidation reactor inlet temperature T1. The heated stream is passed to the reactor where the methane is oxidised. A gas stream including the products of the oxidation reaction are removed with the gas stream being at a reactor outlet temperature T2 higher than the inlet temperature T1. The gas stream is then passed through the heat exchanger against the reactor stream to recover heat from the gas stream removed in the reactor and to heat the reactor stream. The outlet temperature T2 is measured and the inlet temperature T1 is controlled by adjusting the relative amount of make-up methane and/or air added to the feed gas.