Dual-Circuit Heat Pump Drying System for Paper Mill Waste Heat Recovery
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Solution Overview
Problem
The existing drying methods for cellulose-containing base materials in paper production, such as through-flow drying, require high thermal energy and generate significant waste heat, making them inefficient and resource-intensive.
Innovation Solution
A dual-circuit system is introduced, where a first circuit uses a heat transfer medium to dry the material, and a second circuit, equipped with a heat pump, recovers and refeeds heat energy into the first circuit, reducing energy consumption and waste heat utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If through-flow drying with high temperature gas or steam is used, then drying effectiveness is improved, but thermal energy consumption increases and waste heat is generated
Solution Approach 1:
The patent implements a feedback mechanism by circulating the heat transfer medium through a closed loop system where it continuously picks up moisture from the drying stock and returns to the drying unit. The medium is repeatedly heated and utilized, creating a self-sustaining thermal cycle that reduces external energy input while maintaining drying effectiveness.
Solution Approach 2:
The patent changes the parameter of heat transfer medium temperature utilization by maintaining it in a liquid state at elevated temperatures (above 100°C) throughout the circuit, rather than allowing it to cool down and discard heat. This parameter optimization enables continuous heat recovery and reuse, significantly reducing thermal energy consumption.
2Speed
If high temperature gas or steam is used for drying, then drying speed is improved, but waste heat production increases
Solution Approach 1:
The patent converts the previously harmful waste heat into a beneficial resource by implementing heat recovery in the closed circuit. The heat transfer medium, after absorbing moisture and cooling slightly, is reheated in the same circuit and reused, transforming what would have been waste heat into useful thermal energy for continuous drying operations.
Solution Approach 2:
The patent ensures continuity of useful thermal action by maintaining a continuous circulation of the heat transfer medium through the closed loop system. The medium continuously absorbs and releases heat in a repetitive cycle, ensuring that thermal energy is constantly utilized for drying without interruption or waste, thereby maintaining high drying speed with minimal energy loss.
3Use of energy by moving object
If a closed circuit with heat transfer medium circulation is used, then energy efficiency is improved, but system complexity increases
Solution Approach 1:
The patent applies universality by designing the heat transfer medium circuit to perform multiple functions simultaneously: it acts as a drying agent, a heat carrier, a moisture transport medium, and a reusable thermal reservoir. This multi-functionality reduces the need for separate systems for each function, thereby limiting the increase in overall system complexity while achieving high energy efficiency.
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 during the drying process, enables more efficient use of waste heat, and prevents contamination between heat transfer media, leading to a resource-saving production of base materials like pulp and paper.
Implementation Method 1
a second circuit comprises a heat pump for feeding heat energy into the first circuit
Implementation Method 2
at least a part of the solvent evaporates and is separated from the base material by the flow of steam
Implementation Method 3
an optional condenser for the solvent, in particular water, is used to extract the solvent from the heat transfer medium
Data Source
AI summary
A method for drying drying-stock includes separating solvent-containing drying stock within a drying unit into a base material and a solvent with the aid of a first heat transfer medium that flows through a first circuit, where after the solvent has been taken up by the first heat transfer medium, the solvent is extracted from the heat transfer medium via heat energy (condensation), where the heat energy is transferred by a heat exchanger with the aid of an evaporation unit to a second circuit and made available to a second heat transfer medium, and where the heat energy is fed in a condensation unit of the heat pump back to the first circuit with the aid of a heat pump.