Nordsol's technology explained
Operability and reliability

Bio-LNG is produced by liquefaction of biomethane extracted from biogas. The production of liquefaction-ready biomethane and the liquefaction itself are very different processes. This is why companies that manufacture process equipment focus on either gas treatment or liquefaction.

Why is this important? To realise a bio-LNG plant, EPC companies and system integrators must bring all the components for gas treatment and liquefaction together. To build a complete installation, the unit interfaces on these components must be matched. Also, for the installation to appear as one system to the operator requires a reliable PLC control and safeguarding system. This system communicates with all sensors and valve actuators, position feedback sensors, motor frequency drives, etc., while being compliant with safety standards.

Does that sound easy? It’s not. Energy-efficient and extremely reliable biomethane liquefaction is complex. At atmospheric pressure, biomethane becomes liquid at -162°C. Cooling the gas requires a process that includes different pressures, varying gas flows, and of course very low temperatures. It also requires ultra-pure biomethane, since other components in the gas, such as CO₂, heavier hydrocarbons (VOC’s) and water, will easily freeze and cause blockages and potential damage to the equipment. Therefore, the selection of process technology and equipment is decisive for the operability and energy consumption of a bio-LNG facility.

The design of Nordsol’s innovative process line-up and the selection of equipment played a key role in reaching a safe, reliable and very user-friendly production process. In this process, we fully integrated the biogas treatment and liquefaction steps. This is not only visible in the plant itself but also in the HMI system. This system, designed and developed by Nordsol, provides a single look and feel to all processes in the plant.

Full integration provides significant operational and economic benefits, in addition to energy efficiency. A stable and continuous plant operation means higher bio-LNG production volume and lower operational costs, as we currently experience every day at our bio-LNG plants in Amsterdam and Wilp.

The Nordsol design allows a safe and easy bio-LNG truck loading by unexperienced drivers. This is an unique feature. The semi-automated system guides the truck driver through a sequence of several steps, starting with connecting the earth cable and inerting the loading hoses. All actions are monitored and safeguarded by interlocks in the control system. During the last 3 years and hundreds of truck loadings, Nordsol has been able to make the truck-loading operations a safe and standard, well-controlled operation. Feedback from many truck drivers confirms the very user-friendly truck loading.

The detailed process simulation model in Unisim was the basis for all equipment design and shows a very close match with actual plant operation. It was also helpful in the optimisation of the plant in the second and third year, achieving more energy efficiency and higher uptime.

Today, the plant in Amsterdam can operate for several months with interruption, unmanned, at 110% of design capacity. The process is very stable, highlighted by the fact that the deviation between the gas flow setpoint and measurement is max 1%. Also, cold restarts can be done in 1,5 hours, which further increases the uptime and yield of the plant.

The improvements made to the process and equipment at the Amsterdam plant are also applied in the design of new plants for our customers. The commissioning of the second plant, (at Attero in the Netherlands), the third plant (at RenEco in the UK), and also the 4th plant (at CapWatt in Portugal) went very well. Within a week, the biomethane liquefaction process was stable.