CobaDGS

The centrifugal-compressor seal that reduces methane emissions to zero

CobaDGS – A new zero-emission centrifugal-compressor mechanical seal delivering higher reliability and safety than a typical tandem dry gas seal.

The 2015 Paris Climate Change Conference was a breakthrough for international climate policy. 195 contracting parties are responding to the call for a climate-friendly global economy with the Paris agreement. It will be challenging for policymakers and businesses to achieving the agreement goals.

Most international energy companies recognize the importance of their contributions and are implementing the necessary strategies. One particular focus is on methane emitted due to leaks at sealing points or mechanical seals when extracting, transporting and distributing natural gas.

CobaDGS – The solution for you to reduce methane emissions and commit to a better future, both environmentally and economically

EagleBurgmann's CobaDGS me­chan­i­cal seal is the world's first turbo com­pres­sor seal that reduces harmful fugitive process gas emis­sions to zero. A CobaDGS retrofit not only pre­serves the en­vi­ron­ment, it also makes economic sense.

The CobaDGS mechanical seal pays for itself

You don’t have to sac­ri­fice sus­tain­abil­ity with added costs. The below example provides a cost/benefit cal­cu­la­tion for a typical natural gas pipeline cen­trifu­gal com­pres­sor.
 

Venting a single com­pres­sor and as­so­ci­ated piping, releases approx. 100,000 m³ of process gas/methane into the at­mos­phere every year. A similar amount – in our example over 128,000 m³ – is emitted from seal leakage. The total gas emitted per year and turbo com­pres­sor is around 228,000 m³, which is equiv­a­lent to ap­prox­i­mately 12,542 metric tons of CO₂.

Zero Emissions: CobaDGS eliminates process gas emissions at the shaft seals

Modern natural gas cen­trifu­gal pipeline com­pres­sors are equipped with gas-lu­bri­cated tandem seals, supplied with con­di­tioned process gas as the sealing media. Leakage occurs for tech­ni­cal reasons, re­leas­ing methane into the en­vi­ron­ment directly or pro­duc­ing CO₂ emis­sions when it is flared. The new CobaDGS me­chan­i­cal seal is con­tin­u­ously supplied with dry, clean nitrogen instead of process gas.

Ad­di­tional benefit: When a com­pres­sor is shutdown, it is usually vented to prevent dirt and moisture from entering the seal chamber. The CobaDGS seal supply is a separate clean and dry nitrogen, which ensures a con­tin­u­ous clean seal purge gas; elim­i­nat­ing the need to vent the com­pres­sor.

The energy (and as­so­ci­ated CO₂ emis­sions)  required to generate the nitrogen is hardly sig­nif­i­cant. It is equiv­a­lent to about 4.8 % of natural gas that normally leaks from them (cal­cu­lated using methane as an example; 5.5 kWh com­pres­sor; 10 kWh/m³).

What does 12,542 metric tons of CO2 equate to: A mid-size car in Europe emits about 120 g of CO₂ per km. Driving 10,000 km produces 1.2 metric tons of CO₂. 10,452 cars, driving 10,000 km per year equals the emissions eliminated when a compressor is retrofitted with CobaDGS seals. Imagine the reduced emissions with a fleet of compressors.

How quickly do you benefit from a CobaDGS retrofit?

Com­par­ing a con­ven­tional seal total cost of own­er­ship to a CobaDGS retrofit, shows a breakeven point after ap­prox­i­mately five years of op­er­a­tion. After this point your zero-emis­sion seal upgrade has been paid for along with the elim­i­nated en­vi­ron­men­tal impact.

This calculation does not include CO₂ incentives for reducing emissions.

However, methane mitigation strategies are under discussion, and emission allowance policies expanding to include methane and tax incentives, which are now within reach.
 

The following graph demonstrates how drastically these changes impact a retrofit payback, using 25 €/t CO₂, the current "CO₂ European Emission Allowances price" (Dec. 2020).

When carbon emission pricing is considered, the breakeven point for a CobaDGS retrofit is just one year.