Biogas and landfill gas are valuable renewable energy sources, but they rarely arrive at the point of use in a clean, dry state. Raw gas streams are typically saturated with moisture and carry trace levels of corrosive compounds such as ammonia and Volatile Organic Compounds (VOCs). Left untreated, these contaminants can cause serious damage to engines, boilers, and gas-handling infrastructure. Gas chillers are the engineering solution designed to tackle this problem head-on.
What Is a Gas Chiller?
A gas chiller is a process unit that cools a gas stream to reduce its moisture content, while also lowering concentrations of ammonia and VOCs. By chilling the gas under controlled pressure conditions, condensate is deliberately dropped out of the stream before it reaches sensitive downstream equipment such as combined heat and power (CHP) engines or gas boilers.
The Problem: Moisture and Corrosion in Biogas Systems
It’s well documented that biogas and, in particular, landfill gas, can contain a wide range of potentially corrosive substances. When condensate forms in an engine manifold or charge-cooler, these substances are deposited out, leading to damage ranging from gradual corrosion of charge-coolers to complete, catastrophic engine failure. Similar risks apply when biogas is used to fire boilers.
Why Moisture Forms
The moisture-holding capacity of a gas is directly linked to its temperature and pressure. For example:
At 90°C and 1 atmosphere, air can hold a maximum of 1.416 kg of water per kg of air. Cool that same air to 10°C, and its moisture capacity drops to just 0.0076 kg per kg — a 99.45% reduction.
Landfill gas typically emerges from a site fully saturated with moisture at the temperature within the landfill itself — sometimes as high as 50°C. This is the gas’s dew point, and at that temperature the gas carries roughly 0.09 kg of moisture per kg of gas.
On calm, sunny days with overland pipework, the gas temperature may not fall before reaching its point of use — it can even rise. If the gas is then cooled to 20°C at the point of use, around 0.07 kg of moisture per kg of gas will condense out. For a gas flow of 600 Nm³/hr, that equates to approximately 54 litres of condensate per hour.
The Ammonia Problem
Condensate isn’t just water — it can be highly corrosive in its own right.
Ammonia levels of up to 4,000 mg/l have been measured in biogas condensate generated at an engine intercooler — a concentration corrosive enough to attack copper and brass fittings.
By controlling where and how condensate forms, gas chillers prevent this corrosive liquid from collecting in sensitive engine or boiler components.
How Gas Chillers Work
A refrigeration cycle uses energy — either electrical power or heat — to produce cooling. The degree of cooling achieved depends on the process used and the amount of energy applied.
Gas chillers can be configured in two main ways:
- Electrically powered refrigeration, using conventional compressor-driven cooling cycles.
- Flame-powered (adsorption) refrigeration, where biogas itself drives the cooling cycle, minimising electrical parasitic load on the facility.
Pressure also plays a key role: as pressure increases, a gas’s moisture-holding capacity decreases. Operating a chiller at elevated pressure reduces the cooling load required but increases the energy needed for compression. For example, near zero temperatures, gas at 3 bar g holds less moisture than gas at ambient pressure — an important trade-off in system design.
Key Features
- Stainless steel headers and tubes as standard, for maximum longevity
- Choice of electrical-powered or flame-powered refrigeration cycles
- Standard pressure ranges from 100 mbar g up to 6 bar g, with higher pressures available on request
- Complete compression and cooling packages, including dewatering facilities
- Cryogenic temperature range cooling packages available
- Options for integration with main facility control systems
Technical Specifications
| Parameter | Specification |
|---|---|
| Flow rates | 50 to 20,000 m³/hour |
| Pressure range | Vacuum up to 6 bar g standard (higher available as special builds) |
| Temperature range | Minimum chill (to prevent pre-combustion condensation) down to sub-zero dewpoints; standard exit temperature ~2°C |
| Materials | Stainless steel headers and tubes (standard); explosion-bonded headers/tubes for heavy duty available |
| Power sources | Electrical energy or fuel sources (e.g. biogas, landfill gas) |
| Chemicals required | Glycol for cooling water, depending on cooling water temperature |
| Pre-treatment | Demisting and filtration recommended |
Typical Applications
Gas chillers are used across a range of gas processing contexts, including:
- Biogas utilisation for CHP and power generation
- Landfill gas utilisation
- Air-stream drying
- Biogas upgrading to biomethane
Why Correct Sizing and Design Matter
Every site has unique gas characteristics — composition, moisture loading, pressure, and ambient conditions all vary. These factors must be carefully accounted for at the design and specification stage to ensure the chiller delivers the right dew point reduction without over- or under-sizing the plant. Experienced engineering input is essential to avoid costly downstream corrosion issues while keeping capital and energy costs proportionate to the application.
Key Takeaways
- Untreated biogas and landfill gas can carry significant moisture and corrosive compounds like ammonia, risking serious engine and boiler damage.
- Gas chillers cool the gas stream in a controlled way, dropping out condensate before it reaches sensitive equipment.
- Systems can be electrically powered or driven by biogas itself via adsorption cooling, reducing parasitic electrical load.
- Standard units handle 50–20,000 m³/hour at pressures up to 6 bar g, with stainless steel construction for long service life.
- Correct design must account for site-specific gas composition, temperature, and pressure conditions.
Get in Touch
If you’re dealing with moisture, corrosion, or condensate issues in your biogas, landfill gas, or gas upgrading process, our team has extensive experience designing gas chiller solutions tailored to your site’s specific conditions. Contact us today to discuss how a properly specified gas chiller package can protect your engines, boilers, and equipment for the long term.