Cement Cooling via Carbon Dioxide Injection
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Solution Overview
Problem
Existing methods for cooling cement or cement-like powders, such as direct contact with liquid nitrogen, result in insufficient thermal contact and excessive gas escape, leading to inefficient cooling and increased burden on dedusting filters and the environment.
Innovation Solution
Using liquefied or cold gaseous carbon dioxide, which is introduced into the delivery line and mixes with cement, providing efficient cooling without phase transition issues and minimizing gas release, thus reducing dust loss and filter requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If liquid nitrogen is sprayed into the cement silo via a separate feed line, then the nitrogen vaporizes and is discharged as a gas, but sufficient cooling cannot be achieved due to insufficient thermal contact between the nitrogen and cement
Solution Approach 1:
The patent combines the cement feed line and nitrogen feed line into a single integrated conveying line, allowing cement and liquid nitrogen to be mixed and conveyed together. This merging ensures intimate thermal contact between the cooling medium and cement throughout the conveying process, resolving the insufficient thermal contact issue while maximizing nitrogen enthalpy utilization.
Solution Approach 2:
The patent uses pneumatic conveying to transport both cement and liquid nitrogen through a shared conveying line. The gas stream carries both the cement particles and liquid nitrogen droplets, ensuring thorough mixing and heat exchange. This pneumatic approach enables efficient thermal contact without requiring separate feed lines.
2Temperature
If liquid nitrogen is introduced via a socket arranged in the cement line, then cement is fed pneumatically into a silo, but there is no homogeneous heat exchange between the cement and nitrogen
Solution Approach 1:
The patent implements continuous mixing and conveying of cement and liquid nitrogen through a single line, ensuring homogeneous heat exchange throughout the entire process. The continuous pneumatic conveying maintains constant contact between the cooling medium and cement, eliminating the heterogeneous heat exchange that occurs with discrete injection points.
3Temperature
If a Venturi nozzle is installed in the delivery line with liquid nitrogen injected through a mixing tube, then the substance is mixed with nitrogen and cooled, but strong gas evolution at the feed point causes brief blocking of the delivery flow
Solution Approach 1:
The patent merges the feed line and conveying line into a single integrated system, allowing gradual mixing and cooling of cement with liquid nitrogen throughout the conveying process. This eliminates the sudden phase transition and gas evolution at a discrete feed point, preventing flow blocking while maintaining continuous delivery.
4Quantity of substance
If the silo is more than 70% full and high gas development occurs, then cement is carried away by the nitrogen gas, leading to substance loss and requiring a very large filter surface
Solution Approach 1:
The patent changes the physical state and introduction method of the cooling medium from liquid nitrogen (causing sudden vaporization) to cold gaseous carbon dioxide. This parameter change reduces gas evolution intensity and eliminates the turbulent gas flows that carry cement out of the silo, thereby reducing substance loss and minimizing the required filter surface area.
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 method achieves efficient cooling of cement with reduced gas development, minimizing dust loss and filter maintenance, and maintaining concrete quality by avoiding pH changes and outgassing, allowing for smaller dedusting systems and lower environmental impact.
Implementation Method 1
carbon dioxide is fed into the delivery line in the liquefied or cold gaseous state at a feed point and mixed with the cement in a mixing section of the delivery line. The mixed and thus cooled cement then flows down into the silo
Implementation Method 2
When it enters the delivery line, the carbon dioxide is expanded and greatly cooled with the formation of carbon dioxide gas and carbon dioxide snow
Implementation Method 3
The carbon dioxide snow predominantly still sublimates within the conveying line, but to a lesser extent only when it exits the conveying line
Data Source
Figure 1
AI summary
In the production of fresh concrete, it is sometimes necessary to cool the cement mixed into the mix. This is achieved using a known method by introducing liquid nitrogen into a pneumatic conveying line for the cement. Upon contact with the cement, the liquid nitrogen vaporizes rapidly. The resulting pressure increase leads to a brief interruption of the cement conveying process. Consequently, dust is periodically blown out through the silo's exhaust system, posing a risk to employees and the environment. The invention proposes using carbon dioxide as the cooling medium, supplied in a liquid or cold gaseous state. Due to its higher specific cooling capacity compared to nitrogen, carbon dioxide can be used in smaller quantities for the same cooling performance, thus resulting in less gas evolution.Preferably, the carbon dioxide in liquid form is fed into the cement conveying line (9) of a silo (10) and expanded there with a strong release of cold.