Mercury Removal in Cement Clinker Line via Bypass Flue Gas
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Solution Overview
Problem
Cement clinker manufacturing processes face challenges in reducing mercury and other heavy metal emissions, with existing methods either being costly or ineffective in maintaining low mercury concentrations within the manufacturing line, leading to environmental impact.
Innovation Solution
The method involves preheating raw meal in a kiln, cooling the flue gas to condense mercury and other heavy metals onto dust particles, using a bypass flue gas stream to vaporize and remove mercury-loaded dust, and employing adsorbents to capture mercury, thereby reducing emissions and maintaining low mercury concentrations within the process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If flue gas is cooled to condense mercury onto dust particles for removal, then mercury emissions are reduced, but the condensed mercury concentrates in the manufacturing line when dust is reintroduced
Solution Approach 1:
The patent extracts the harmful mercury substance from the main manufacturing process by introducing a bypass flue gas stream that diverts mercury-containing flue gas away from the preheater system. This allows mercury to be removed without being reintroduced into the manufacturing line, solving the contradiction between reducing emissions and preventing concentration buildup.
Solution Approach 2:
The flue gas stream is segmented into a main stream (continuing to preheat raw meal) and a bypass stream (withdrawn for mercury removal). This segmentation allows selective treatment of mercury-containing gas without disrupting the main manufacturing process, enabling emission reduction while preventing mercury concentration in the clinker line.
2Ease of manufacture
If substitute fuels like plastic waste are used to reduce manufacturing costs, then operating costs are reduced, but heavy metal content including mercury increases in the process
Solution Approach 1:
The patent converts the harmful effect of heavy metals introduced by substitute fuels into a manageable problem by designing a removal system. The bypass flue gas stream captures heavy metals and mercury that are inevitably introduced by cost-effective substitute fuels, allowing the plant to maintain low operating costs while controlling emissions through active removal rather than preventing fuel selection.
3Productivity
If dust loaded with mercury is reintroduced to the preheater for processing, then dust is utilized in the process, but mercury is vaporized again and concentrates in the manufacturing line
Solution Approach 1:
The patent extracts mercury-loaded dust from the dust stream before it can be reintroduced to the preheater. By withdrawing a bypass flue gas stream that contains the mercury-laden dust and treating it separately, the system prevents mercury from cycling back into the manufacturing line while still allowing clean dust to be utilized in the preheater for productive purposes.
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 approach effectively reduces mercury and other heavy metal emissions while minimizing operating costs by utilizing existing thermal energy and reducing the need for additional cooling gases, resulting in a more environmentally friendly and cost-effective cement clinker production process.
Implementation Method 1
cooling the flue gas to a temperature below that corresponding to the boiling point of mercury and dedusted, thereby obtaining mercury-loaded dust
Implementation Method 2
At least a fraction of the mercury (and/or other heavy metals) of the mercury-loaded dust is vaporized in a bypass flue gas stream
Implementation Method 3
employing adsorbents to capture mercury, thereby reducing emissions
Data Source
AI summary
A method for manufacturing clinker includes sintering raw meal in a kiln to clinker, preheating the raw meal (prior to sintering the raw meal) in a preheater using a main flue gas stream from the kiln as heat source, dedusting the main flue gas downstream of the preheater at a temperature below the boiling point of mercury (thereby obtaining mercury loaded dust) and withdrawing a bypass flue gas stream from the kiln. The method is configured to efficiently remove mercury from the manufacturing process if mercury in the bypass flue gas is vaporized by injecting of at least a fraction of the mercury-loaded dust into the bypass flue gas stream. Subsequently, the bypass flue gas is dedusted and cooled down. Thereby, the mercury can be adsorbed by injecting an adsorbent (such as activated charcoal) into the bypass flue gas. With subsequent removal of the adsorbent, mercury is finally removed from the manufacturing process.