Drying heat recovery - Industrial purification heat recovery

Waste Heat Recovery Systems for Industrial Dryers

Waste heat recovery systems for industrial dryers capture and reuse thermal energy from hot exhaust gases or air streams to improve energy efficiency, reduce operating costs, and lower emissions. These systems are valuable for energy-intensive drying processes in industries like chemical, food, ceramics, and textiles. Below, I outline key technologies, benefits, and U.S.-based suppliers with contact information.

Key Technologies for Waste Heat Recovery in Industrial Dryers
Industrial dryers produce hot, moist exhaust air containing sensible and latent heat. Recovery systems extract this heat for reuse. Common technologies include:

Air-to-Air Heat Exchangers:
Transfer heat from hot exhaust air to incoming fresh air via plate or rotary heat exchangers. Polymer air preheaters resist corrosion and fouling.
Applications: Preheating dryer inlet air, reducing fuel consumption by up to 20%.
Advantages: Simple, cost-effective, low maintenance.
Air-to-Liquid Heat Exchangers:
Capture heat from exhaust to warm liquids for process heating or facility HVAC.
Applications: Heating process water in food processing plants.
Advantages: Versatile heat reuse.
Heat Pumps:
Upgrade low-temperature waste heat to higher temperatures for reuse.
Applications: Lifting heat for dryer air preheating in chemical or dairy industries.
Advantages: High efficiency for low-temperature sources.
Direct Contact Heat Exchangers:
Hot exhaust gases directly contact a liquid to transfer heat, often cleaning flue gas contaminants.
Applications: Recovering heat from kilns, ovens, or dryers.
Advantages: Cleans exhaust while recovering heat.
Waste Heat Boilers:
Convert high-temperature exhaust into steam for process use or power generation.
Applications: High-temperature dryers in ceramics or minerals processing.
Advantages: Generates steam or electricity.
Benefits of Waste Heat Recovery for Dryers
Energy Savings: Efficiency improvements of up to 20%.
CO2 Reduction: Every 1% efficiency gain cuts CO2 emissions by 1%.
Cost Reduction: Payback periods from months to 3 years.
Environmental Compliance: Reduces emissions and waste heat release.
Process Optimization: Stable temperatures enhance product quality.
Challenges and Solutions
Fouling and Corrosion: Polymer heat exchangers or in-line cleaning systems mitigate issues.
Heat Sink Availability: Requires nearby heat use for economical integration.
System Design: Custom engineering ensures compatibility.

how does air to air heat exchanger work in Spray drying heat recovery

In spray drying heat recovery, an échangeur de chaleur air-air is used to recover waste heat from the hot, moist exhaust air leaving the drying chamber and transfer it to the incoming fresh (but cooler) air. This reduces the energy demand of the drying process significantly.

How It Works:

Exhaust Air Collection:
- After spray drying, hot exhaust air (often 80–120°C) contains both heat and water vapor.
- This air is pulled out of the chamber and sent to the heat exchanger.
Heat Exchange Process:
- The hot exhaust air flows through one side of the heat exchanger (often made of corrosion-resistant materials due to possible stickiness or mild acidity).
- At the same time, cool ambient air flows through the other side, in a separate channel (counter-flow or cross-flow setup).
- Heat is transferred through the exchanger walls from the hot side to the cool side, without mixing the air streams.
Preheating Incoming Air:
- The incoming fresh air gets preheated before entering the spray dryer’s main heater (gas burner or steam coil).
- This lowers the fuel or energy required to reach the desired drying temperature (typically 150–250°C at the inlet).
Exhaust Air Post-Treatment (optional):
- After heat extraction, the cooler exhaust air can be filtered or treated for dust and moisture before being released or further used.

Benefits:

Energy Savings: Cuts down fuel or steam consumption by 10–30% depending on setup.
Lower Operating Costs: Less energy input reduces utility expenses.
Environmental Impact: Reduces CO₂ emissions by improving energy efficiency.
Temperature Stability: Helps maintain consistent drying performance.

how does air to air heat exchanger work in nmp heat recovery

An air-to-air heat exchanger in NMP heat recovery transfers thermal energy between a hot, NMP-laden exhaust air stream from an industrial process and a cooler incoming fresh air stream, improving energy efficiency in industries like battery manufacturing.

The hot exhaust air (e.g., 80–160°C) and cooler fresh air pass through separate channels or over a heat-conductive surface (e.g., plates, tubes, or a rotary wheel) without mixing. Heat transfers from the hot exhaust to the cooler fresh air via sensible heat transfer. Common types include plate heat exchangers, rotary heat exchangers, and heat pipe heat exchangers.

NMP-specific designs use corrosion-resistant materials like stainless steel or glass fiber-reinforced plastic to withstand NMP’s aggressive nature. Larger fin spacing or clean-in-place systems prevent fouling from dust or residues. Condensation is managed to avoid blockages or corrosion.

The hot exhaust air transfers heat to the fresh air, preheating it (e.g., from 20°C to 60–80°C) and reducing energy needs for subsequent processes. The cooled exhaust air (e.g., 30–50°C) is sent to an NMP recovery system (e.g., condensation or adsorption) to capture and recycle the solvent. Heat recovery efficiency is 60–95%, depending on the design.

This reduces energy consumption by 15–30%, lowers greenhouse gas emissions, and improves NMP recovery by cooling the exhaust air for easier solvent capture. Challenges like fouling are addressed with wider gaps, extractable elements, or cleaning systems, while robust sealing prevents cross-contamination.

In a battery manufacturing plant, a plate heat exchanger preheats fresh air from 20°C to 90°C using 120°C exhaust air, reducing oven energy demand by ~70%. The cooled exhaust air is processed to recover 95% of NMP.

how does air to air heat exchanger work in wood drying

An air-to-air heat exchanger in wood drying transfers heat between two air streams without mixing them, optimizing energy efficiency and controlling drying conditions. Here's how it works:

Purpose in Wood Drying: Wood drying (kiln drying) requires precise temperature and humidity control to remove moisture from wood without causing defects like cracking or warping. The heat exchanger recovers heat from exhaust air (leaving the kiln) and transfers it to incoming fresh air, reducing energy costs and maintaining consistent drying conditions.
Components:
- A heat exchanger unit, typically with a series of metal plates, tubes, or fins.
- Two separate air pathways: one for hot, humid exhaust air from the kiln and one for cooler, fresh incoming air.
- Fans or blowers to move air through the system.
Working Mechanism:
- Exhaust Air: Hot, moisture-laden air from the kiln (e.g., 50–80°C) passes through one side of the heat exchanger. This air carries heat energy from the drying process.
- Heat Transfer: The heat from the exhaust air is conducted through the exchanger’s thin metal walls to the cooler incoming fresh air (e.g., 20–30°C) on the other side. The metal ensures efficient heat transfer without mixing the two air streams.
- Fresh Air Heating: The incoming air absorbs the heat, raising its temperature before it enters the kiln. This preheated air reduces the energy needed to heat the kiln to the desired drying temperature.
- Moisture Separation: The exhaust air, now cooler, may condense some of its moisture, which can be drained away, helping to control humidity in the kiln.
Types of Heat Exchangers:
- Plate Heat Exchangers: Use flat plates to separate air streams, offering high efficiency.
- Tube Heat Exchangers: Use tubes for air flow, durable for high-temperature applications.
- Heat Pipe Exchangers: Use sealed pipes with a working fluid to transfer heat, effective for large kilns.
Benefits in Wood Drying:
- Energy Efficiency: Recovers 50–80% of heat from exhaust air, lowering fuel or electricity costs.
- Consistent Drying: Preheated air maintains stable kiln temperatures, improving wood quality.
- Environmental Impact: Reduces energy consumption and emissions.
Challenges:
- Maintenance: Dust or resin from wood can accumulate on exchanger surfaces, requiring regular cleaning.
- Initial Cost: Installation can be expensive, though offset by long-term energy savings.
- Humidity Control: The system must balance heat recovery with proper moisture removal to avoid overly humid conditions.

In summary, an air-to-air heat exchanger in wood drying captures heat from exhaust air to preheat incoming air, improving energy efficiency and maintaining optimal drying conditions. It’s a critical component in modern kiln systems for sustainable, high-quality wood processing.

how does a heat exchanger work in a boiler

A heat exchanger in a boiler transfers heat from the combustion gases to the water circulating in the system. Here's how it works step by step:

Combustion occurs: The boiler burns a fuel source (like natural gas, oil, or electricity), creating hot combustion gases.
Heat transfer to the heat exchanger: These hot gases flow through a heat exchanger—typically a coiled or finned metal tube or series of plates made of steel, copper, or aluminum.
Water circulation: Cold water from the central heating system is pumped through the heat exchanger.
Heat absorption: As the hot gases pass over the surfaces of the heat exchanger, heat is conducted through the metal into the water inside.
Hot water delivery: The now-heated water is circulated through radiators or to hot water taps, depending on the boiler type (combi or system boiler).
Gas expulsion: The cooled combustion gases are vented out through a flue.

In condensing boilers, there's an extra stage:

After the initial heat transfer, the remaining heat in the exhaust gases is used to preheat incoming cold water, extracting even more energy and improving efficiency. This process often creates condensate (water), which is drained from the boiler.

Heat recovery device for whitening and defogging exhaust gas from paper mill drying

The exhaust gas generated by paper mills during the production process has the characteristics of high temperature, high humidity, and foul odor. If directly discharged, it not only pollutes the environment but also wastes a large amount of heat energy. To solve this problem, our company has developed a whitening and defogging heat recovery device for drying waste gas in paper mills.

Heat recovery device for whitening and defogging exhaust gas from paper mill drying
working principle:
Heat exchange principle: Using the principle of plate heat exchangers, heat is exchanged through a series of parallel metal plates. High temperature exhaust gas flows through one side of the plate, while fresh air flows through the other side, transferring heat through the plate wall to achieve waste heat recovery.
Cooling and heating process: Firstly, the high-temperature exhaust gas is cooled to a temperature close to the ambient temperature, and then heated by a reheater to make the exhaust gas temperature higher than the ambient temperature, thereby eliminating the phenomenon of white mist.
Technical advantages:
Efficient and energy-saving: By recovering waste heat from exhaust gas, energy consumption and operating costs are significantly reduced.
Environmental protection and emission reduction: effectively removing moisture and odorous components from exhaust gas, reducing pollution to the environment.
Compact structure: small size, light weight, easy installation, and occupies less space.
Application scenarios:
Paper industry: Recovering heat during the paper drying process to preheat the air entering the dryer, improve drying efficiency, and reduce fuel consumption.
Food processing industry: Recycling waste heat from the drying process of grains, vegetables, fruits, etc., to preheat fresh air and improve drying efficiency.
Chemical industry: Recycling high-temperature waste gas from the drying process of chemical products for heating other process gases or air.
Textile industry: used for the recovery of waste heat during the drying process of textiles, improving drying efficiency and energy-saving effects.

Heat pump drying heat recovery energy saving system

With the further development of China's economy, the use of green energy will be more and more extensive. Heat pump dehumidification dryers with plate type obvious heat recovery function have developed rapidly in recent years and have been widely used in the Yangtze River basin, southwest China and South China.

The unit using the inverse cano principle at the same time, combined with efficient heat recovery technology, in the whole drying dehumidifying process, through the duct the wet air within the chamber connected to the host using the sensible heat plate heat collector recovery of the sensible heat and latent heat of hot and humid air, thermal recycling, greatly improve the performance of the host, improve the drying speed and material quality. The waste heat can not only improve the performance of the unit, but also reduce the thermal pollution to the environment and alleviate the urban heat island effect.

The heat pump drying heat recovery system is not only used in the mud drying system, but also widely used in many other drying industries. It has the characteristics of good drying quality and high degree of automation, and is the best choice product for energy saving, green and environmental protection in the modern drying industry.

Heat pump dryers with and without heat recovery working principle

When the heat pump dryer dries the air, the air forms a closed cycle between the drying chamber and the equipment. The evaporator's heat absorption function is used to cool and dehumidify the hot and humid air, and the condenser's heat release function is used to heat the dry cold air, so as to achieve the effect of cycle dehumidification and drying.

The main difference between heat recovery function and heat pump dryers without heat recovery function lies in the different air circulation modes. The former is equipped with plate type sensible heat exchanger, which plays the function of pre-cooling and preheating in the air circulation process, reducing the load of compressor operation and achieving the purpose of energy saving.

Heat pump drying heat recovery energy saving system(图1)

Heat pump drying system operation mode

Heat pump drying heat recovery energy saving system(图2)

Energy saving analysis of heat recovery

Taking a heat pump dryer as an example, the air temperature of drying is designed to be 65℃, the relative humidity is 30%, the circulating air temperature is 65℃, the temperature before passing through the evaporator is 65℃, and the temperature after evaporation cooling is 35℃. The condenser needs to heat the air of 35℃ to 65℃ before it can be used.

After matching with BXB500-400-3.5 heat exchanger, 35℃ return air absorbs heat from exhaust air after passing through plate heat exchanger, and the temperature rises to 46.6℃. The condenser only needs to heat the air from 46.6℃ to 65℃ to meet the use requirements, greatly reducing the load of evaporator and condenser, thus reducing the power of the whole machine, achieving the purpose of energy saving.

Energy saving analysis of heat recovery

Heat pump drying heat recovery energy saving system(图3)

Selection and economic calculation

We are very glad to show you the calculation and selection software of plate heat exchanger jointly developed by us and Tsinghua University. If you need, please contact us!

Design of Drying, Dehumidification and Heat Recovery System

With the rapid development of manufacturing industry, many products require drying and dehumidification treatment during the production process. These processes not only require efficient moisture removal, but also require maintaining the characteristics and quality of the material. Traditional drying and dehumidification methods often consume high energy and may have adverse effects on the environment, such as emitting greenhouse gases and other pollutants.

By adopting efficient heat recovery technology, waste heat can be maximally recovered and reused to reduce energy consumption. Heat recovery technology has been widely applied in multiple industries to improve energy efficiency and reduce operating costs. But in the field of drying and dehumidification, the potential of this technology has not been fully tapped. We customize and develop a heat recovery system that suits your specific production needs and on-site conditions. We carefully design the system layout for you to ensure minimal loss of thermal energy during conversion and transmission. Welcome to inquire via email.

Ventilation heat exchanger for vegetable low-temperature processing area and supermarket sorting area

In the low-temperature vegetable processing area, the main function of the ventilation heat exchanger is to ensure that the temperature of the processing environment is suitable to maintain the freshness and quality of the vegetables. Ventilation heat exchangers use efficient heat exchange technology to dissipate indoor heat while introducing external cold air or cooled air for effective temperature control.
In addition, the ventilation heat exchanger in the low-temperature vegetable processing area also needs to consider humidity control, as excessive humidity may cause vegetable rot. Therefore, some ventilation heat exchangers are also equipped with humidity regulation functions to ensure that the humidity in the processing environment remains within an appropriate range.
The sorting area of a supermarket or shopping mall is responsible for sorting, packaging, and delivering goods. The main function of the ventilation heat exchanger in this area is to provide fresh air and remove indoor turbid air and excess heat.
The ventilation heat exchanger in the sorting area of supermarkets usually has a large air volume and efficient heat exchange performance to meet the needs of large spaces and high pedestrian flow. At the same time, they also need to have the characteristics of easy maintenance and cleaning to ensure long-term stable operation.
Whether it is a low-temperature vegetable processing area or a supermarket sorting area, ventilation heat exchangers are indispensable and important equipment. They provide a comfortable and healthy working environment for these areas through efficient air conditioning and temperature control, which helps improve production efficiency and product quality.
Our cross countercurrent plate heat exchanger is made of high-quality hydrophilic aluminum foil, epoxy resin aluminum foil, stainless steel, polycarbonate and other materials. The air flows partially in cross flow and partially in relative flow to avoid the transmission of odors and moisture. Applied to energy recovery in civil and commercial ventilation systems, as well as industrial ventilation systems. Fast heat conduction, no secondary pollution, good heat transfer effect.

Salle de séchage de légumes, de thé, de haricots, échangeur de chaleur à air de déshumidification et d'élimination de l'humidité

Des systèmes de déshumidification et de déshumidification efficaces sont nécessaires pendant le processus de séchage des produits agricoles tels que les légumes, le thé et les haricots pour garantir la qualité et l'efficacité du processus de séchage. L'échangeur de chaleur à gaz joue un rôle crucial dans ce processus. Ce qui suit est une introduction détaillée au système de déshumidification et de déshumidification des salles de séchage de légumes, de thé et de haricots.

Processus de déshumidification :
L'air humide et chaud de la salle de séchage est aspiré par le ventilateur d'extraction et échange de la chaleur avec l'air sec entrant lorsqu'il traverse l'échangeur thermique air-air.
Après avoir traversé l'échangeur de chaleur, la température de l'air humide et chaud évacué diminue et la vapeur d'eau se condense en eau liquide et est évacuée.
L'air sec entrant est préchauffé par un échangeur de chaleur et entre dans la salle de séchage, améliorant ainsi l'efficacité du séchage.

Scénarios d'application
Séchage des légumes : comme les piments, les carottes, le chou, etc., en contrôlant la température et l'humidité, la couleur et la nutrition des légumes séchés ne sont pas détruites.
Séchage du thé : Pour le thé vert, le thé noir, le thé oolong, etc., l'arôme et la qualité du thé sont maintenus grâce à un contrôle approprié de la température et de l'humidité.
Séchage des légumineuses : telles que le soja, les haricots mungo, les haricots rouges, etc., sont séchés uniformément à l'air chaud pour garantir la sécheresse et la qualité de conservation des haricots.

L'application d'échangeurs de chaleur gaz-air dans les salles de séchage de légumes, de thé et de haricots a amélioré l'efficacité énergétique et la qualité des produits du processus de séchage grâce à des fonctions efficaces de déshumidification et de déshumidification. Une conception et une utilisation raisonnables peuvent réduire considérablement la consommation d'énergie et les coûts d'exploitation, tout en étant respectueuses de l'environnement, ce qui en fait un élément indispensable de la technologie de séchage moderne.

Récupération de chaleur d’épuration industrielle

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