Project SynopsisDevelop an FEL-2 level process design package including balance of plant utilities for a pilot-scale process to convert well gas-to-liquid (GTL) hydrocarbon fuels.
WELLHEAD GAS TO FISCHER-TROPSCH LIQUIDS FEL-2 PROCESS DESIGN
Process Engineering Associates, LLC (PROCESS) was subcontracted by the client, a modular process fabricator, to produce an FEL-2 level process design package for the ultimate client, a renewable energy technology company. The process design package is for a pipeline or wellhead gas to Fischer-Tropsch (FT) liquids unit. The ultimate client had previously developed a process flowsheet, computer model, and heat and material balance for most of the main process unit operations. The purpose of the FEL-2 process design performed by PROCESS was to extend the ultimate client’s work by adding balance of plant equipment items and developing enough additional process detail to the facility flowsheet, items such as gas conditioning reactors, FT fractionation, phase separation, etc., to allow for a preliminary, Rough Order of Magnitude cost estimate and provide documentation for initiation of a FEL-3 design (to be performed by the client).
The first step in this work effort was to establish the process scope of the FEL-2 design and expand the ultimate client’s Block Flow Diagram (BFD) into a Process Flow Diagram (PFD). The BFD indicated an electrically-heated reformer converts feedstock gas to synthesis gas (syngas). PROCESS used the ultimate client’s steam reformer design to convert wellhead gas to syngas. Syngas was conditioned (treated for sulfur, HCl, BTX, and mercury), cooled, and compressed. A technical evaluation was conducted to determine the best approach to syngas conditioning and cooling. Next, syngas was converted to hydrocarbons in the ultimate client’s FT reactor process. The FT Reactor is a novel conversion device used to generate FT hydrocarbons for liquid fuel production.
Hydrocarbons generated in the FT Reactor were cooled and separated as a liquid phase from the gaseous light-ends. The bulk of the light-ends were recycled back through the steam reformer and FT reactor. FT hydrocarbons were fractionated into “cuts”. Various hydrocarbon cuts differ by boiling point and carbon chain length. It is desired by the ultimate client to produce naphtha, Jet-A, and diesel from the fractionator as salable products. PROCESS identified the separation equipment required to produce the desired product slate and also identified the equipment necessary to recover waste heat and produce enough electric power to make the facility electrically self-sufficient.
Once the PFD was discussed and agreed to between all of the project team members, the PFD was used to develop a steady-state CHEMCAD process simulation model. The model depicted the chemical reactions required to describe steam reforming, gas conditioning, and FT liquids production. The model included a fractionator with multiple side splitter columns. A second separation column was used to concentrate Jet-A fuel and ensure the specification for flash and freeze point was met. A Combustion Turbine Generator with a Heat Recovery Steam Generator was modeled. A Steam Turbine Generator utilized steam generated by the recovery of energy from waste heat to produce electrical energy. A cooling tower was modeled along with water treatment.
Heat and Material Balance (H&MB) tables were generated following completion of the CHEMCAD model. Streams were included in the H&MB tables with all primary process and utility (steam, cooling water service) streams. Streams were identified on the PFD and H&MB with a unique label such that the streams could be easily referenced, and the composition and physical properties easily checked. Also, a utility table summarizing electrical requirements was generated from the results of the CHEMCAD model.
An equipment list was developed, and all major plant equipment shown on the PFD was tagged and identified on the list. Preliminary equipment sizing calculations were performed to estimate basic equipment geometries. Equipment prices were obtained either from vendor solicitation or through the use of Aspen’s Icarus software. Bare equipment costs were used to generate a Total Installed Cost (TIC) estimate. The TIC was a factored cost estimate. The factors used in generating the TIC were discussed and agreed upon with the client.
- Alternative Fuels
- FEL-2 level pilot-plant design
- Balance of plant / OSBL systems design