WASTE GAS INCINERATION

What is Waste Gas Incineration?

Many industrial processes create a byproduct of low concentration air contaminants collectively called volatile organic compounds (VOC). Despite the low concentration, VOC emissions remain directly harmful to humans and damage the overall environment due to the large scale of the industries contributing to the VOC production.

Industries Contributing to VOC Emissions

    • Oil and gas processors
    • Chemical plants
    • Landfills
    • Large-scale cattle farming

The Environmental Protection Agency (EPA) provides specific guidelines for addressing VOC emissions. The most common approach is incineration, i.e., burning unwanted hydrocarbons and other VOC in the contaminated air. However, this process requires supplemental fuel as the VOCs are insufficiently concentrated to sustain the flame. Furthermore, a poorly executed incineration can create more harm than good (NOx production from hot spots, improved spreading of unburned VOC that slipped through, etc.).  

How Can Swiss Roll Technology Address VOC Emissions?

Figure 1. Operating principle of heat-recirculating Swiss-roll incinerator.

Figure 1. Operating principle of heat-recirculating Swiss-roll incinerator. VOC-contaminated air (blue) enters the device and is preheated as it travels to the core, where combustion occurs. Hot air and combustion products (green) continue outwards, sharing their thermal energy with the new portion of VOC-contaminated air.

The unique thermal design of Swiss roll allows it to address the identified issues of classical incinerators. The self-enclosing spiral section enables the recycling of the heat from products back into the reactants, as shown in Figure 1. The hotter the reactants, the easier it is to burn and sustain the flame. In technical terms, the excess enthalpy recuperated from the products extends the lean flammability limits in the core, enabling a steady-state ultra-lean operation. The experiments performed at ACT supported this principle, as shown in Figure 2. The ACT lean Swiss roll incinerator was able to operate at almost four times lower fuel load than it is usually possible with using traditional burners. Furthermore, the overall temperature is lower, preventing NOx and other secondary emissions. ACT was able to test a range variety of Swiss roll incinerator sizes (right of Figure 2) and confirmed no change in combustion performance while addressing different ranges of flow rates. In practical incineration cases, the ultra-lean operation dramatically reduces the supplementary fuel requirements and, in certain VOC-heavy cases, avoids the fuel addition entirely.

Figure 2: Results of Swiss-roll incinerator efforts at ACT:

Figure 2: Results of Swiss-roll incinerator efforts at ACT: (left) large 1’ and small 2” units presented side-by-side (right) lean operational limits for propane and biogas fuels proven significantly lower than conventional values over a range of flow rates. That means our incinerator can operate without the supplementary fuel for a significantly wider range of conditions.

The compact, thermally efficient design, with no moving parts, makes the Swiss roll an attractive option for waste gas incineration applications.

Waste Gas Incineration Innovation

ACT has been awarded an ARPA-E Reducing Emissions of Methane Every Day of the Year (REMEDY) project, where a Swiss roll incinerator will be applied to oil field gas flares. The goal is to improve the VOC destruction efficiency beyond the industry-standard 98% level. The remaining 2% represent effectively doubles the flare stack’s effective carbon footprint due to flare gas’s very high Global Warming Potential (GWP). A 2021 UN Environment Programme Global Methane Assessment identified reducing methane emissions as the most effective method of fighting climate change. The proposed system, shown conceptually in Figure 3, aims to reach 99.9% flare gas combustion, significantly reducing harmful emissions.  

Figure 3: The flare incineration system for ARPA-E REMEDY project:

Figure 3: The flare incineration system for ARPA-E REMEDY project: (left) conceptual view (right) operational principle with flare gas entering directly to the center. The unique thermal design enables 99.9%+ methane destruction efficiency.

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Swiss-roll Volatile Organic Compound (VOC) Incinerator

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