DOC Metal Substrate

DOC Metal Substrate Solutions for Distributed Power Systems

In distributed power systems—industrial boilers, regional heating plants, small power stations—the exhaust profile is very different from what we see on-road. Loads are steadier, temperatures climb slowly, and the units may run for thousands of hours without shutdown. Because of that, the expectations for the DOC Metal Substrate inside these systems shift toward reliability, long service intervals, and predictable performance under stable but high-temperature conditions.

After dealing with multiple CHP units and boiler retrofit projects, I’ve found that the metal substrate plays a bigger role than people think. Once it’s installed, it must handle continuous thermal stress, occasional start–stop shocks, and a wide range of exhaust compositions—from light hydrocarbon slip to heavy SOF depending on the fuel and burn quality.

Why Metal Substrates Work Well in Distributed Energy Applications

A DOC for distributed power systems mainly needs three things: fast heat-up, strong resistance to long-duration operation, and stable conversion efficiency. Metal substrates support all three:

Quick thermal response

Metal heats faster than ceramic. During cold starts, oxidation reactions begin sooner, which reduces visible smoke and CO peaks.

Better vibration tolerance

Power units don’t vibrate like off-road machines, but they do transmit low-frequency structural vibration. Metal honeycombs handle these well.

High thermal fatigue resistance

Continuous operation at 500–650°C plus occasional spikes demands a substrate that won’t warp or lose coating adhesion. FeCrAl-based DOC Metal Substrates hold up extremely well under this kind of load.

Design Priorities for Power-Generation DOCs

Unlike on-road DOCs, which chase compact size and low backpressure, distributed power systems give you more room—but they introduce other constraints.

1. Material Selection

Most engineers end up choosing FeCrAl because:

it forms a durable oxide layer that helps the washcoat bond,

it holds shape at high temperature,

it survives long-duration operation without creep deformation.

Stainless steels like 304/316L may be fine for lower temperature boilers, but for consistent >550°C operation, FeCrAl has a clear advantage.

2. Cell Density and Foil Thickness

DOC Metal Substrates for boilers or CHP units need to balance two factors:

surface area for conversion and pressure drop across long operating hours.

Typical ranges we use:

200–300 CPSI for biomass or low-quality fuel applications

300–400 CPSI for natural-gas or light-oil systems

0.05–0.08 mm foil for long-term shape retention

Too dense, and ash fouling becomes an issue. Too open, and CO reduction suffers. The right choice depends heavily on the fuel and expected particulate level.

3. Geometry and Flow Distribution

Distributed power systems often use larger-diameter substrates or multi-brick assemblies. The geometry influences:

gas residence time,

catalyst light-off behavior,

long-term thermal gradient inside the housing.

Round DOC Metal Substrates work best for even flow. For retrofit projects with irregular duct shapes, oval sections are sometimes used, but round carries less risk of edge hot spots.

4. Coating Durability and Washcoat Adhesion

This is easily the most underestimated point.

Power systems accumulate sulfur, vapor-phase ash, and unburned hydrocarbons. The coating must stay bonded even as the substrate expands and contracts during daily temperature cycles. High-quality pre-oxidation of FeCrAl foil makes a noticeable difference in real field tests.

Application Notes by Scenario

1. Industrial Boilers

Boiler exhaust varies widely based on fuel.

For coal/biomass boilers:

ash load is high,

moisture fluctuates,

temperature ramps are slower.

Here a lower CPSI, thicker foil DOC Metal Substrate is less likely to clog and more tolerant of thermal deformation.

For cleaner gas-fired boilers:

higher CPSI improves HC and CO conversion,

pressure drop is less of a concern.

2. Regional Heating Systems

Heating plants tend to run long steady cycles at mid-high temperature.

Key concerns:

long-term creep resistance,

washcoat stability over 5,000+ hour intervals.

Larger-diameter metal substrates with FeCrAl foil typically provide the most stable performance in these systems.

3. Small Distributed Power Stations (CHP)

CHP exhaust has a lot of variation because the engines constantly adjust to load demand.

Design considerations include:

faster light-off after short shutdowns,

strong thermal-cycle durability,

stable conversion efficiency even with fuel quality changes.

Metal substrates excel here simply because ceramic types don’t like repeated thermal cycling.

Installation and Integration Tips

A DOC Metal Substrate is only as good as the housing and mounting around it:

Avoid over-compressing the mounting mat.

Maintain straight inlet flow to prevent channel overloading.

Allow enough axial space for thermal expansion.

Inspect downstream components—excessive backpressure accelerates oxidation of the foil.

In distributed systems, these small details have a big impact on service life.

Distributed power systems place different demands on a DOC compared with vehicles or off-road machines. They run longer, hotter, and more consistently. That’s exactly where DOC Metal Substrates show their strengths: stability, oxidation efficiency, and resistance to thermal fatigue.

When designed properly—right foil, right cell density, right geometry—metal substrates offer long service life with minimal maintenance, which is critical for plants where downtime is costly.