Power-to-Liquid

Navigation:

The Power-to-Liquid Component

The Power-to-Liquid component represents the production of liquid fuels from gaseous fuel. Surplus electricity from renewable energy sources, such as wind, is preferably used as an energy source, and cold and heat are also added.

Component Template

Th Power-to-Liquid.e-ctpl component template is located in the Component template library folder Renewable Energy Sources.

Pins

The component has the following pins.

Cold water in (top)
Cold water out (bottom)
Heat in (orange)
Power (red)
Fuel in (left) – absorbed gaseous fuel
Liquid out (right) – liquid fuel delivered (produced)

Integration Into a Scheme

The following figure shows an example of how to integrate the Power-to-Liquid component into a scheme.

The supplied heat (orange) can come from a steam or hot water circuit, which are connected with the components Heat_Extraction_From_Steam or Heat_Extraction_From_Warm_Water. The process heat generated is either dissipated using cooling water and a connected cooling tower (recooler) or used in a hot water circuit.

Special Features

The component has four incoming powers and one outgoing power.

The conversion ratio and the nominal ratio of the individual input to output power are defined reciprocally:

Total efficiency = outgoing power / sum of incoming power

Conversion ratio = incoming power / outgoing power

The fuel outputs refer to the lower heating value H_i.

Selection of Process

In the Technical input data, first select which process is to be modeled: Specific methanol synthesis (for pure methanol production) or Other processes (own specification, see following figure).

The structural optimization of the component is only possible for Other processes and not for the Specific methanol synthesis.

The amount of CO₂ consumed and the resulting revenues can only be taken into account for Specific methanol synthesis.

Methanol Synthesis

If you want to evaluate the pure production of methanol, select Specific methanol synthesis as the process from the drop-down list. Methanol synthesis is modeled using a white box model: The output data are determined on the basis of the physical relationships from the input data. The thermodynamic calculation of the individual process steps forms the basis for this. Methanol synthesis comprises the following process steps.

1. Compressing CO₂ and H₂
2. Mixing CO₂ and H₂ with the Recycle stream (H₂, CO₂, and CO)
3. First preheating
4. Reverse water-gas shift reaction (rWGS): CO₂ + H₂ \( \rightleftharpoons \) CO + H₂O
5. First cooling
6. Condensation of the produced water
7. Second preheating
8. Methanol synthesis: CO + 2 H₂ \( \rightleftharpoons \) CH₃OH
9. Second cooling
10. Separation of the methanol as the end product from the unreacted starting materials (H₂, CO₂, and CO), which are fed back into the process as a recycle stream to step 2

The Design parameters in the Technical input data include the efficiencies for the compressor, preheating, and cooling. For the heat recovered within the process, specify the Heat recovery rate in percent. The Specific energy for separation is the energy required to separate the synthesized fuel, its unit is kJ/kg related to the fuel mass.

In the Technical input data, select the Carbon dioxid source from the drop-down list under Operating parameters and enter the Electricity demand for CO2 extraction if necessary.

If CO₂ is self-generated, the rated power and the Consumed electrical power are made up of the shares of the power required for CO₂-extraction and for fuel synthesis, which are given in the Technical output data under the heading Constituents of the electric power consumption.

In the Economic input data, enter the EUA price for CO2 emission rights.

Other Processes

For other processes for the production of liquid fuel that go beyond the pure production of methanol, select from the drop-down list Other processes. These are mapped using a black box model that links the input and output data with each other using purely statistical mathematical relationships without any direct physical meaning. This concerns the conversion ratios of electricity, heat, cooling, and fuel required to fuel produced.

Part Load Behavior

Part load behavior refers to the nominal output of fuel produced \( P_{fuel\ out} \). As with all energy converters, it can be determined by a constant efficiency or characteristic curves.

Under the heading Design of energy conversion, select the desired energy related input method:

Constant conversion ratio (energetic) \( ratio = \frac{P_{el}}{P_{fuel\ out}} \) ; \( \begin{equation} \begin{aligned} P_{el\ nom} = \dot{m} \cdot H_i \cdot ratio \end{aligned}\end{equation}\) with
- Nominal conversion ratio (ratio of consumed power to delivered fuel power in nominal state: electricity/fuel, fuel/fuel, heat/fuel, and cooling/fuel) or
- Nominal driving power (drive power),
Absolute characteristic (correlation between the fuel power \( \begin{equation} \begin{aligned} \dot{m} \cdot H_{i} \end{aligned}\end{equation}\) and the electrical power \( \begin{equation} \begin{aligned} P_{el\ nom} \end{aligned}\end{equation}\) via a characteristic curve \( \begin{equation} \begin{aligned} f_{el\ abs}\end{aligned}\end{equation}\) with the following formula:\( \begin{equation} \begin{aligned} P_{el\ nom} = f_{el\ abs} (\dot{m} \cdot H_{i}) \end{aligned}\end{equation}\)) or
Relative characteristic (correlation between the fuel power \( \begin{equation} \begin{aligned} \dot{m} \cdot H_{i} \end{aligned}\end{equation}\) and the electrical power \( \begin{equation} \begin{aligned} P_{el\ nom} \end{aligned}\end{equation}\) via a characteristic curve \( f_{el\ rel}\) with the following formula: \( \begin{equation} \begin{aligned} f_{el\ rel} \left ( \frac{P_{el}}{P_{el\ nom}} \right) = \frac{\dot{m}}{\dot{m}_{nom}} \end{aligned}\end{equation}\)).

When specifying a constant conversion ratio, the nominal fuel capacity of the fuel produced must be specified in relation to the lower heating value H_i. If the individual nominal conversion ratios are specified, the Nominal electrical, thermal, and cooling capacity, and the Nominal fuel power (ref. LHV) based on the lower heating value of the incoming fuel are calculated and specified in the Technical output data. If the driving power is specified, the nominal ratios are calculated and output in reverse. In addition, the Operating performance, the course of the individual powers, is indicated in the Output data.

Reference Conditions for Material Values

The material values used to calculate the methanol synthesis do not refer to the DIN or ISO standard as in the other components, but to the SATP conditions (Standard Ambient Temperature and Pressure: 25 °C, 1.013 bar).

Temperature-Dependent Simulation With Specified Outlet Temperature

In simulations with the material property Heat/Cooling temperature dependent, the mixture temperatures are determined after optimizing the energy balance. To do this, enter the Outlet temperature of the Transfer medium (water/coolant) bottom in the Technical input data form. The article about Special Features of Cold and Heat provides further information.

Simulation Considering Composition

The following must be observed when simulating with the material property Fuel Considering composition.

Fuel Gaseous Model Considering Composition

If Specific methanol synthesis is selected, pure hydrogen is required. If the incoming fuel connected via the pin is not pure hydrogen, a warning is displayed during the simulation.

Fuel Liquid/Solid Model Considering Composition

In Specific methanol synthesis, the material composition and the outlet variables outlet temperature and outlet pressure are fixed for the process and are included as parameters in the thermodynamic calculation. They cannot be freely selected by the user.
For Other processes, you can specify the characteristic data for liquid fuel, its Elementary composition, and the Physical properties of the ashes in the Technical input data (see following figure).

Technical Output Data

The calculated Consumed electrical power is indicated under the Technical output data (see following figure). Consumed electrical power includes not only the production of liquid fuel but also, if specified in the Input data, the extraction of CO2 from the air and the compression of the gas produced. For this reason, the total Consumed electrical power may be greater than the maximum power consumption of the pure power-to-liquid plant, which relates solely to water electrolysis and methanation and is specified in the input data.

Under the heading Constituents of the electric power consumption, the shares of the power required for CO2 extraction and for fuel synthesis in the nominal capacity and the Consumed electrical power are listed if CO2 is generated by the system itself.

Economic Data

In addition to the usual Economic input data, you can enter the EUA price for CO₂ emission rights for Methanol synthesis because the binding of CO₂ in the fuel produced can generate EUA revenues for CO₂ emission rights, which are shown in the Economic output data of the component and are taken into account as Operating revenues (excluding energy) in the economic balance in the Variant analysis and in the Excel-Export of the Variant comparison. For the Other processes, the amount of CO₂ consumed for production is not taken into account.

Life Cycle Assessment of CO₂ and Primary Energy

The articlel How Life Cycle Assessment (LCA) Works describes how CO₂ and primary energy savings are calculated using two examples.

Cookie Notice