Heat Pump Waste Heat Recovery for Methanol Distillation
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Solution Overview
Problem
The inefficiency in using waste heat from water electrolysis in methanol production, as it is typically lost due to low temperature and requires additional energy to be useful in process units, necessitates a method to enhance heat utilization.
Innovation Solution
A heat pump system with a compressor and indirect heat exchangers is integrated into a heating loop to recover and elevate low-temperature waste heat from electrolysis, utilizing it for methanol distillation, thereby reducing energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If waste heat from electrolysis is recovered at low temperature, then energy recovery is achieved, but the heat cannot be used for process units requiring higher temperature
Solution Approach 1:
The heat pump system changes the temperature parameter of the recovered waste heat by compressing the heat transfer medium, elevating it from low temperature (suitable only for heating) to high temperature (suitable for process units and steam generation). This parameter transformation resolves the contradiction between recovering energy and achieving usable temperature levels.
Solution Approach 2:
A heat transfer medium acts as an intermediary between the waste heat source and the process units. The medium absorbs low-temperature waste heat, is compressed to raise its temperature, and then transfers the high-temperature heat to process units, enabling energy utilization across different temperature levels.
2Temperature
If additional energy is added to increase waste heat temperature, then heat becomes useful for process units, but overall energy efficiency decreases
Solution Approach 1:
The system converts the harmful waste heat that would otherwise be lost into a beneficial high-temperature heat source for process units. By using the compressor to elevate the temperature, the previously useless low-temperature waste heat becomes valuable process heat, turning an energy loss into an energy asset.
Solution Approach 2:
The heat transfer medium undergoes phase transitions (evaporation and condensation) during the heat pump cycle. These phase changes enable efficient heat absorption at low temperature and heat rejection at high temperature, facilitating the temperature elevation while utilizing the thermodynamic properties of the working medium.
3Loss of energy
If a heat pump system with compressor is installed, then waste heat utilization is improved, but device complexity increases
Solution Approach 1:
The heat pump system performs multiple functions: it recovers waste heat, elevates its temperature, and supplies it to various process units including distillation columns and heaters. This multi-functionality justifies the added complexity by providing versatile heat utilization across different process requirements.
Solution Approach 2:
The heat pump operates continuously to recover and upgrade waste heat throughout the production process, ensuring uninterrupted supply of process heat. This continuous operation maximizes energy utilization and offsets the initial complexity investment through sustained energy savings.
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 reduces overall energy consumption by effectively utilizing waste heat, lowering steam requirements and optimizing power usage in the methanol production process.
Implementation Method 1
providing a second process stream consisting of hydrogen by electrolyzing water in an electrolysis unit
Implementation Method 2
recovering waste heat generated in the electrolysis unit by transferring the waste heat to a circulating heat transfer medium by indirect heat exchange
Implementation Method 3
the heat transfer medium, in its gaseous state, is pressurized and circulated through the loop by the compressor
Implementation Method 4
the hot and pressurized vaporized heat transfer medium is cooled in a heat exchanger by heat exchange with steam used in the methanol distillation unit and condensed into a pressurized liquid
Implementation Method 5
The condensed heat transfer medium is then flash evaporated through a pressure-lowering device e.g. an expansion valve
Implementation Method 6
catalytic converting the methanol synthesis gas into raw methanol in at least one methanol reactor
Data Source
AI summary
Process for the preparation of a methanol product comprising the steps of a) providing a first process stream consisting essentially of carbon dioxide; b) providing a second process stream consisting of hydrogen by electrolyzing water in an electrolysis unit; c) mixing the first and second process in amount to obtain a methanol synthesis gas with a mole ratio of H2 and CO2 of between 2.5 and 3.5; d) catalytic converting the methanol synthesis gas into raw methanol in at least one methanol reactor; e) purifying the raw methanol in a distillation unit; and recovering waste heat generated in the electrolysis unit in step (b) by transferring the waste heat to a circulating heat transfer medium by indirect heat exchange with the waste heat and by indirect heat exchange of the heated heat transfer medium with steam used for the distillation of the raw methanol, wherein the heated transfer medium is compressed upstream the indirect heat exchange with steam.