Cooling Hygroscopic Bulk Materials via Exhaust Air Heat Recovery
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Solution Overview
Problem
Current methods for cooling hygroscopic bulk materials, such as fertilizers and salts, require significant energy to dry cooling air, leading to high operational costs and potential product quality issues due to moisture absorption, which can result in reduced hardness and shape loss or clumping.
Innovation Solution
A method involving the recycling of heated exhaust air to preheat the cooling air flow, reducing the need for process heat and fresh air, while maintaining low relative humidity to prevent moisture absorption, using a two-stage cooling process with indirect heat exchange and steam heating for energy efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cooling air is dried to prevent moisture absorption by hygroscopic bulk materials, then product quality is maintained, but energy consumption increases significantly
Solution Approach 1:
The invention recovers waste heat from the exhaust air stream and uses it to preheat the incoming cooling air. The exhaust air, which contains thermal energy, is directed through a heat exchanger where it transfers heat to the incoming air stream, thereby reducing the energy required for heating and drying the cooling air while maintaining product quality
Solution Approach 2:
The invention converts the harmful effect of warm exhaust air (which would normally be wasted) into a beneficial resource by using it to preheat the cooling air stream. This reduces the energy demand for heating cooling air and maintains low relative humidity without excessive energy consumption
2Reliability
If process heat is supplied to warm cooling air to desired relative humidity, then moisture absorption is prevented, but operational costs increase
Solution Approach 1:
The system recovers thermal energy from the exhaust air stream and uses it to preheat the incoming cooling air. This reduces the amount of process heat required from external sources, thereby lowering operational costs while maintaining the desired relative humidity levels for moisture control
3Productivity
If large quantities of fresh air are used for cooling, then cooling effectiveness is improved, but energy consumption for heating and drying increases
Solution Approach 1:
The invention recovers heat from exhaust air to preheat incoming fresh air, reducing the energy required for heating and drying large volumes of cooling air, thereby maintaining cooling effectiveness while reducing energy consumption
Solution Approach 2:
The warm exhaust air, which would normally be wasted, is converted into a useful resource for preheating the incoming fresh air stream, reducing the energy penalty associated with using large quantities of fresh air for cooling
4Productivity
If air conditioning systems are sized for full cooling capacity, then cooling performance is ensured, but investment costs increase
Solution Approach 1:
By recovering waste heat from exhaust air to preheat incoming cooling air, the system reduces the total cooling capacity required from the air conditioning system, allowing for smaller, less expensive equipment while maintaining full cooling performance
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 reduces energy consumption and investment costs by minimizing the need for process heat and fresh air, while ensuring product quality by maintaining low relative humidity, allowing for more efficient cooling with lower operating costs and smaller air conditioning systems.
Implementation Method 1
a part of the exhaust air flow is mixed with the air flow in order to preheat the latter
Implementation Method 2
an air flow is used in a contact device for cooling the solid
Data Source
AI summary
The present disclosure relates to a method and a device for cooling a solid, in particular a hygroscopic bulk material, in a more energy-efficient manner. For this purpose, an air flow is, if needed, cooled and/or dehumidified and/or subsequently heated in order to reduce the relative humidity of the air flow. The cooling air flow conditioned in this manner is then used in a contact device for cooling the solid, and a heated exhaust air flow is drawn from the contact device. According to the invention, a part of the exhaust air flow is mixed with the air flow in order to pre-heat the air flow and thus reduce the relative humidity of the air flow. In addition, a second part of the exhaust air flow can be mixed with feed air and used in a separate second contact device in order to pre-cool the solid.