Fluidized Bed Cooling for Fresh Concrete Temperature Control
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Solution Overview
Problem
Existing methods for producing cooled fresh concrete often result in inhomogeneous temperature distribution and inefficient refrigerant use, leading to substance loss and environmental burden due to inadequate thermal contact between refrigerants and additives, as well as impractical cooling processes that interfere with mixing device operation.
Innovation Solution
A method where a partial flow of the additive is cooled in a fluidized bed reactor using a cryogenic refrigerant like nitrogen or carbon dioxide, allowing for precise temperature control and efficient heat transfer, with the cooled additive being separated and fed directly to the mixing device, avoiding unnecessary refrigerant consumption and substance loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If liquid nitrogen is sprayed into the cement silo via a separate feed line, then the cement is cooled, but sufficient cooling cannot be achieved due to insufficient thermal contact between cement and nitrogen
Solution Approach 1:
The cement flow is divided into a first portion that is cooled in a cooling device and a second portion that is not cooled, allowing selective cooling of only the necessary amount of cement rather than cooling the entire stored supply
Solution Approach 2:
A cooling device is introduced as an intermediary component between the cement storage silo and the mixing device, providing a dedicated space where liquid nitrogen can efficiently contact and cool the cement before it is fed to the mixer
2Temperature
If a large amount of liquid nitrogen is used to cool cement in the storage silo, then cooling effect is achieved, but substance is lost and environmental burden increases due to cement being entrained by nitrogen gas
Solution Approach 1:
The cement flow is segmented into cooled and uncooled portions, with only the first portion being cooled, thereby reducing the total amount of nitrogen required and minimizing cement entrainment and loss
Solution Approach 2:
The cooling process is extracted from the storage silo environment and relocated to a dedicated cooling device, preventing nitrogen gas from mixing with and entraining cement in the storage area
3Temperature
If refrigerant is fed into the supply line between storage silo and mixer, then cooling occurs, but strong gas development blocks the flow of substance and causes pulse-like blowing off of dust
Solution Approach 1:
The phase change process of the refrigerant is extracted and confined to the cooling device, where gas development occurs in a controlled environment separate from the pneumatic conveying line, preventing flow blocking and dust blowing off
Solution Approach 2:
The cooling device serves as an intermediary that decouples the refrigerant injection process from the cement conveying process, allowing efficient heat transfer without interfering with the stability of the pneumatic flow
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 enables efficient cooling of fresh concrete with precise temperature control, reducing environmental impact and operational challenges by minimizing refrigerant usage and preventing substance loss, while ensuring homogeneous temperature distribution in the final product.
Implementation Method 1
a partial flow of the additive removed from the storage silo is brought into thermal contact with a refrigerant in a cooling device and is thereby cooled
Implementation Method 2
the refrigerant heated during thermal contact with the additive is separated from the cooled additive
Implementation Method 3
the substance, mixed with the nitrogen and thus cooled, is then conveyed to the silo
Data Source
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AI summary
A necessary part of the production of fresh concrete is to cool the cement or other mixing material mixed with the fresh concrete. According to a known method, said cooling is accomplished, for example, by feeding liquid nitrogen through a feed line to the pneumatic cement feed. The liquid nitrogen evaporates immediately upon contact with the cement. The associated increase in pressure leads to a short-term break in the conveyance of cement. As a result, periodic blow-off of dust occurs through the exhaust unit of the silo, which leads to placing a burden on workers and the environment. According to the invention, it is suggested to arrange a second feed line, parallel to the existing feed line between the supply silo and scale or mixing unit, wherein at least part of the flow of each mixing material is diverted and fed through a cooling unit. In the cooling unit, the mixing material contacts a cooling material which is removed from the cooling unit at the end of the cooling process. For the cooling process, a cryogenic cooling material, for example nitrogen or carbon dioxide, is preferably used. The cooling unit is preferably a fluidized screw cooler or a fluidized bed reactor. The invention allows an exact dosing and temperature target for the cooled mixing material.