Lignite Coke Adsorbent Sulfur Doping for Mercury Recovery
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Solution Overview
Problem
Existing methods for producing mercury-containing adsorbents are not economically viable for regeneration, leading to high landfill costs and energetically expensive recovery processes, as the adsorbents become irreversibly bound with mercury, making them unsuitable for repeated use.
Innovation Solution
A process involving lignite coke doped with elementary sulfur, where the mixture is heated in a controlled oxygen-containing atmosphere between 120 °C and 150 °C for 0.5 to 1 hour, allowing for reversible mercury adsorption and desorption without forming irreversible chemical bonds with sulfur, enabling cost-effective regeneration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the adsorbent is treated in an inert gas atmosphere with sulfur impregnation, then the adsorbent effectively removes mercury from exhaust gases, but the mercury becomes irreversibly bound and the adsorbent cannot be regenerated
Solution Approach 1:
The patent changes the atmospheric parameters during heat treatment from inert gas to oxygen-containing atmosphere (1-21% oxygen). This parameter change transforms the chemical environment, allowing surface oxidation that prevents irreversible mercury-sulfur bonding while maintaining mercury adsorption effectiveness. The controlled oxygen concentration creates conditions where mercury remains reversibly bound.
Solution Approach 2:
The patent intentionally avoids using inert gas atmosphere during heat treatment, instead employing an oxygen-containing atmosphere. By eliminating the inert environment that would allow irreversible chemisorption, the process enables reversible mercury binding. The oxygen-containing atmosphere fundamentally changes the chemical behavior of sulfur on the carbon surface.
2Loss of substance
If existing regeneration processes are used to recover mercury from adsorbents, then mercury recovery is achieved, but the processes are energetically expensive and not economically viable
Solution Approach 1:
The patent changes the thermal and atmospheric parameters during the adsorption phase to enable lower-temperature regeneration. By controlling the heat treatment in oxygen-containing atmosphere at 120-150°C, the process creates reversible bonds that can be broken at lower temperatures than conventional processes, reducing regeneration energy requirements while maintaining mercury recovery efficiency.
Solution Approach 2:
The patent converts what would normally be a harmful irreversible chemisorption reaction into a beneficial reversible process. By using oxygen-containing atmosphere during heat treatment, the sulfur forms surface oxides that prevent permanent mercury binding, turning a potential waste stream into a regenerable adsorbent system.
3Ease of manufacture
If the adsorbent is landfilled after use, then disposal is simple, but landfill costs are high and mercury recovery is lost
Solution Approach 1:
The patent implements a recovery system where mercury is desorbed from the adsorbent and condensed for reuse. The regenerated adsorbent can be returned to service for additional cycles. This closed-loop system prevents mercury loss and eliminates the need for landfilling, recovering both the valuable mercury and the adsorbent material.
Solution Approach 2:
The adsorbent system is designed to be self-regenerating through thermal desorption. The mercury-loaded adsorbent undergoes heating in oxygen-containing atmosphere that releases mercury while regenerating the adsorbent's capacity, enabling multiple reuse cycles without external regeneration facilities or landfilling.
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 allows for efficient and cost-effective recovery of mercury from exhaust gases, with the lignite coke adsorbents maintaining mercury adsorption and desorption capabilities over multiple cycles, reducing landfill costs and energy consumption.
Implementation Method 1
The sulfur is both physically adsorbed, ie deposited in the pores by capillary condensation of the vapor, and chemisorbed.
Implementation Method 2
Carbon-sulfur complexes are formed by chemisorption, in which the sulfur is chemically bound
Implementation Method 3
the mercury contained in the exhaust gas does not form any chemical compound with the sulphur
Implementation Method 4
the mixture is heated to a temperature between 120 °C and 150 °C and the temperature is maintained for a period of between 0.5 and 1 hour
Data Source
AI summary
Preparing adsorption agents containing carbon doped with elementary sulfur, comprises mixing sulfur with the adsorption agent, heating the mixture at 120-150[deg]C and retaining the temperature over a period of 0.5-1 hour, where the heating of the mixture takes place under controlled oxygen-containing atmosphere. An independent claim is included for cleaning exhaust gas under use of an adsorption agent doped with elementary sulfur, comprising alternately carrying out the adsorption and desorption of mercury over the exhaust gas system, preferably by at least a packed bed adsorbers.