Cement Preheater Segmentation for Mercury Separation
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Solution Overview
Problem
Current methods for reducing mercury emissions in cement clinker production are energy-intensive and economically inefficient, often requiring large air quantities and plant sizes, with existing solutions like the expulsion reactor involving high energy expenditure due to repeated heating of dust in the preheater.
Innovation Solution
A process where two raw material streams with different concentrations of volatile components are fed into separate lines of a preheater, with the higher concentration stream treated in one line and the lower concentration stream in another, allowing for efficient separation of volatile components using a substream of off-gases, eliminating the need for intermediate storage and cooling, thereby reducing energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the entire off-gas stream is cleaned with activated carbon filters, then mercury separation is achieved, but plant size and costs become economically unacceptable due to large air quantities
Solution Approach 1:
The off-gas stream is divided into two separate lines: the first line handles off-gases with high mercury concentration from the preheater, while the second line handles off-gases with low mercury concentration from the kiln. This segmentation allows targeted treatment only where necessary, reducing overall plant size and costs.
Solution Approach 2:
Different treatment approaches are applied to different locations in the process: the first line receives activated carbon injection for mercury binding, while the second line uses dust injection for mercury binding. This local differentiation optimizes resource usage and reduces overall treatment costs.
2Object-affected harmful factors
If an expulsion reactor is used to separate mercury, then mercury is expelled from sorbent, but energy expenditure increases due to repeated heating of dust in the preheater
Solution Approach 1:
The harmful effect of repeated heating is extracted and eliminated by designing a system where dust is heated only once in the preheater to a sufficient temperature range (250-500°C), then directly injected into the second line without returning to the preheater for re-heating.
Solution Approach 2:
The temperature parameter is optimized to a sufficient range (250-500°C) that allows effective mercury binding without requiring excessive heating energy, and this temperature is maintained throughout the process without repeated heating cycles.
3Quantity of substance
If raw materials are prepared with hot gases to vaporize mercury, then mercury is separated in concentrated form, but a relatively large amount of energy is required increasing overall costs
Solution Approach 1:
The off-gases, which would otherwise be wasted or require expensive treatment, are converted into a useful heating medium for preparing raw materials and binding mercury, turning a potential harm into a beneficial resource.
Solution Approach 2:
The off-gas stream serves multiple functions: it heats raw materials in the preheater, provides the temperature necessary for mercury binding with dust/activated carbon, and maintains the thermal regime in the system without requiring additional energy input.
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 significantly increases energy efficiency and reduces gas volume flow, making the process more cost-effective by minimizing additional energy use and maintaining high mercury emission reduction.
Implementation Method 1
the first raw material stream heated to a temperature of at least 250° C. by heat exchange with the first substream of the off-gases in the first line of the preheater
Implementation Method 2
the volatile component bound in the raw materials is vaporised and separated off from the off-gases
Data Source
AI summary
A process and device separate off a volatile component from the off-gases in cement clinker production. Raw materials for cement clinker production are passed through a preheater with heat exchange with the off-gases and are then burnt in a rotary kiln. Owing to the heating in the preheater, the volatile component bound in the raw materials is vaporized and separated off. A first raw material stream having a relatively high concentration of the volatile component is applied to a first line of the preheater and a second raw material stream having a lower concentration of the volatile component is applied to a second line. The volatile component is separated off from the first substream of the off-gases. The first raw material stream heated to a temperature of at least 250° C. with the first substream of the off gases in the first line is combined with the second raw material stream.