T2C-ENERGY, LLC
PINELLAS PARK, FLORIDA

An idea needs to be tested and confirmed before going mainstream. We started to optimize the catalytic technology needed to convert landfill gas constituents (methane and carbon dioxide) into synthesis gas. They worked tirelessly to achieve this via a little known technology called tri-reforming. Tri-reforming synergistically combines three oxidants together to generate synthesis gas. In addition, we also used syngas constituents (carbon monoxide and hydrogen) to further optimize the final product output. Prior to integrating both technologies together, we designed a set of experiments using each reactor system independently. From literature studies and site visits to Florida landfills we noticed a ratio of CH of about 1.0:0.7 to be a typical concentration found in landfill gas. From this we did many experiments around the tempeature, pressure, catalyst shape, and residence time in the reactor to produce a suitable synthesis gas feed to be used in the next step, Fischer-Tropsch synthesis (FTS). We were successful. From there we focused our attention on tailoring our final product cuts to be towards a middle-distillate range, specifically a diesel fuel. As we did with tri-reforming, we tweaked our catalyst shape, temperatures, and pressures, inlet feed ratios, catalyst pore filling procedures until we were satisfied that we could get consistent results. Now, we were ready to integrate the two systems. To our knowledge, combining a tri-reformer and an FTS system together had never been done before. We had to engineer it from scratch based on what we knew about existing steam reformers and FTS. Both reactors operated at different pressures and temperatures, so a lot of engineering went into optimizing the system with the lab equipment available. We weaved together a Swagelok system to include both reactor systems, mass flow controllers, pressure relief valves, booster pumps, chillers, and gas governers. Since we now had raw unfiltered landfill gas, we also had to clean it up before reacting it further downstream. We put flanged three 1 liter volume filter beds in series to absorb sulfur, siloxanes, and halides respectively. The tri-reforming reaction is endothermic and needs a lot of heat to generate the reaction. We bought a Hastelloy tube which we stuffed with catalyst and used a furnace to heat the reactor. After generating our synthesis gas, we knew we needed to dehydrate the stream for the FTS feed. We utilized a chiller and glycol solution to jacket around the flowstream. The condensed water was then gravitationally removed from the stream. We also had only a 60 psi air pressure supply. With that we essentially had to compress the syngas to pressures to room temperature for the first product extraction. Secondarily, we designed a colder trap to ensure that all liquids would condense out of the system. The gaseous products were to be vented off. After some trial and error we were now ready to test using real landfill gas to make diesel. Testing surrogate gases and getting good results gave us assurance that we were on to something. Testing actual landfill gas (LFG) and making a diesel from it was the goal. In order to accomplish this goal, landfill gas had to be collected and transported to the lab. We set about this task by visiting eight landfills within a two hour driving radius from our business headquarters in Tampa, Florida. Sarasota County was willing to let us compress their gas into a cylinder. Now, LFG has very low pressure, so we had to find a compressor that would take gas from atmospheric pressure all the way to pressures greater than 2,000 psi. To do this we found a home fueling compressed natural gas unit capable of compressing natural gas at 0.4 psig up to 3600 psig at a flow rate of 1.3 standard cubic feet per minute. The model was safe. It included automatic shutoff interlocks based on temperature and pressure readings. Another neat feature of the model was it only required 220 Volts to power. Therefore, we could use portable generator with no dependence on the landfill operations electricity sources. We wanted avoid any moisture accumulation and possible corrosion in the pressurized cylinders, so we affixed two 1 liter volume filter beds of DRIERITE in a parallel configuration to ensure that inlet LFG feed to the compressor was completely dry. We tapped into the main LFG header using ½” NPT piping/connections and a natural gas certified flexible hose to deliver gas to the DRIERITE filter bed and ultimately the inlet to the compressor. We also placed a gas governor prior to the compressor inlet to regulate pressure to 0.4 psig recommended pressure supply to compressor. We also installed pressure gauges before and after gas governor and also the cylinder inlet. Thus, pressures were safely monitored. Stainless steel ¼” tubing was connected to the outlet of the compressor and a check valve installed as a safety precaution. The tubing was coiled and submersed in an ice water bath to regulate compressed gas temperature below 37°C and connected to gas cylinder. A CO2 monitor was utilized as a safety precaution during the collection of the LFG. Once we had our cylinders of actual LFG, we brought it back to the lab! We were excited to start this. This was the first time in history tri-reforming of actual landfill gas had been coupled with Fischer-Tropsch synthesis (FTS). We designed our experiment run for about a week. We prepped our catalysts and made sure they were reduced properly. Everything was a go. We cracked open the LFG cylinder and started the process. We ran round the clock operations and closely scrutinized every detail of the reaction. Lots of coffee, Red Bulls, and Monsters were consumed during the trials. We closely monitored flow rates and conversion rates of each reaction. We monitored compositions, temperatures and pressures. When we collected our samples, we closed our mass balance. Once we had our final liquid product, we injected it into a gas chromatograph/mass spectrometer (GC/MS) we were very happy with what we found. Inspecting the tables accompanying this article allows for a good comparison of the chemical and physical footprint of TRIFTS fuel. Our chromatograph had a very similar footprint to that of commercial diesel sold at fueling stations across the world. While the TRIFTS process produced a slightly higher number of lighter hydrocarbons. These were very little issue to separate out, and can easily be separated out in the process design. When comparing the chemical families, we can see that our TRIFTS diesel had a higher paraffinic content to what is commercially sold on interstate exits. Longer, straighter hydrocarbon chains