Waste-Heat Recovery Case Study: Stack & Exhaust

The opportunity

A metal-finishing plant exhausted 18,000 m3/h of 160C air from curing ovens to atmosphere – pure lost energy. The brief was to recover it for winter make-up air heating and preheat a process water loop.

The solution

• A high-temperature plate air-to-air exchanger (stainless, rated to 200C+) transferred exhaust heat to incoming fresh air.
• A secondary air-to-water coil pulled surplus heat into the water buffer.
• Fouling-prone exhaust demanded a cleanable core and a maintenance plan from our cleaning guide.

Results

• Recovered ~520 kWth at peak.
• Gas boiler load cut ~35% in winter.
• Payback: 2.8 years.

Lessons

Capture heat in grade order – high-grade first (process water), low-grade last (ventilation). Match the core material to exhaust temperature and contaminants. See waste-heat recovery basics 및 standards overview before specifying.

Why capture at the source

The plant curing ovens rejected 160C air continuously, a high-grade, high-volume stream far more valuable than typical ventilation exhaust. Recovering it at the source, before it mixes with cooler building air, maximizes the temperature lift available to the incoming make-up air and the process-water loop. This grade-first logic is the backbone of any waste-heat strategy.

Material and contamination matching

At 160C and with curing by-products, a standard aluminum core would not survive. The stainless, high-temperature-rated plate exchanger was selected specifically for the exhaust condition, and the fouling-prone nature of the stream dictated a cleanable core plus a maintenance plan. Matching material and cleanability to the exhaust is what keeps the 520 kWth recovery stable year after year.

From one oven to a program

A single successful project often reveals more opportunities. The same approach, measure the stream, grade it, pick a core rated for the temperature and contaminants, then verify savings, scales to other process exhausts across the site. Tracking recovered energy against the boiler baseline proves the case for the next project and supports any efficiency-reporting requirement.

자주 묻는 질문

What did the industrial case recover?
About 520 kWth at peak from 18,000 cubic metres per hour of 160C oven exhaust, cutting boiler load about 35 percent in winter.

Why specify a stainless plate exchanger?
The exhaust at 160C and above, with curing by-products, needs a high-temperature-rated, cleanable material. Standard aluminum would not survive.

What was the payback?
About 2.8 years. The lesson is to capture high-grade heat first and match the core to the exhaust conditions.

How do I replicate this result?
Measure the stream, grade the heat, select a core rated for the temperature and contaminants, plan cleaning, and verify against the boiler baseline.

자주 묻는 질문

What did the industrial case recover?

About 520 kWth at peak from 18,000 cubic metres per hour of 160C oven exhaust, cutting boiler load about 35 percent in winter.

Why specify a stainless plate exchanger?

The exhaust at 160C and above, with curing by-products, needs a high-temperature-rated, cleanable material. Standard aluminum would not survive.

What was the payback?

About 2.8 years. The lesson is to capture high-grade heat first and match the core to the exhaust conditions.

How do I replicate this result?

Measure the stream, grade the heat, select a core rated for the temperature and contaminants, plan cleaning, and verify against the boiler baseline.