How To Recovery Heat From Exhaust Gases Of The Drying

Recovering heat from exhaust gases of industrial drying processes is an effective way to improve energy efficiency, reduce costs, and lower emissions. Below is a concise guide on how to recover heat from dryer exhaust gases, focusing on practical steps, technologies, and considerations, tailored to your interest in air-to-air heat exchangers and waste heat recovery systems.

Steps to Recover Heat from Dryer Exhaust Gases

1. Assess Exhaust Gas Characteristics:
   • Measure the temperature (typically >60°C for dryers), flow rate, and composition of the exhaust (e.g., moisture, dust, or corrosive elements).
   • Determine the sensible (temperature-based) and latent (moisture-based) heat content.
   • Example: Spray dryer exhaust in food processing may be 80–150°C with high humidity.
2. Identify Heat Sink Opportunities:
   • Find nearby processes that can use recovered heat, such as preheating dryer inlet air, heating process water, or supplying facility HVAC.
   • Prioritize direct integration (e.g., preheating dryer air) for maximum efficiency.
3. Select Appropriate Heat Recovery Technology:
   • Air-to-Air Heat Exchangers (Primary Focus):
     • Plate Heat Exchangers: Use metal or polymer plates to transfer heat from exhaust to incoming air. Polymer plates resist corrosion and fouling from moist, dusty exhaust.
     • Rotary Heat Exchangers: Rotating wheels transfer heat, ideal for high-volume flows.
     • Application: Preheat dryer inlet air, reducing fuel use by up to 20%.
   • Air 빨간색-Liquid Heat Exchangers:
     • Transfer heat to water or thermal oil for process heating or boiler feedwater.
     • Application: Heat cleaning water in food or chemical plants.
   • Heat Pumps:
     • Upgrade low-temperature exhaust heat for reuse in drying or other processes.
     • Application: Boost heat for dryer air preheating in dairy processing.
   • Direct Contact Heat Exchangers:
     • Exhaust gases contact water to recover heat and clean contaminants.
     • Application: Suitable for kilns or dryersWITH acidic exhaust.
   • Waste Heat Boilers:
     • Generate steam from high-temperature exhaust for process use or power.
     • Application: High-temperature dryers in ceramics.
4. Design and Install the System:
   • Work with a supplier to design a system tailored to your dryer’s exhaust conditions and heat sink needs.
   • Ensure materials (e.g., polymer or stainless steel) resist fouling and corrosion.
   • Install the heat exchanger downstream of the dryer, with filters or scrubbers if dust is present.
   • Example: A polymer air-to-air exchanger can be retrofitted to a spray dryer to preheat inlet air, reducing energy costs.
5. Monitor and Optimize Performance:
   • Use sensors to track temperature, flow, and efficiency of heat recovery.
   • Clean heat exchangers regularly to prevent fouling.
   • Adjust system settings to maximize heat transfer based on production demands.