MultiFuel GTL Fischer-Tropsch (FT) Reactor

W2 Energy’s MultiFuel Gas-to-Liquid (GTL) Reactor produces ultra low sulfur diesel (ULSD), or a blend of JP8 jet fuel, gasoline and ULSD. The synthesis of hydrocarbons from CO hydrogenation over transition metal catalysts was discovered in 1902 when Sabatier and Sanderens produced CH4 from H2 and CO mixtures passed over Ni, Fe, and Co catalysts. In 1923, Fischer and Tropsch reported the use of alkalized Fe catalysts to produce liquid hydrocarbons rich in oxygenated compounds-termed the Synthol process. The development of pressurized FT synthesis started in Germany in 1925, and developed to an industry with 600 000 tons per year in 1945, using coal as a feedstock.

FT synthesis is a heterogeneous process of carbon monoxide hydropolymerization catalyzed by VIIIB group metals supported on appropriate carrier. Principal reactions are the following:

(a) olefins formation: n CO + 2n H2 ® CnH2n + n H2O

(b) paraffins formation: n CO + (2n +1) H2 ® CnH2n+2 + n H2O

Enthalpy of -CH2- group formation at 227°C is known to be DH227 = – 165 kJ/mol. Recent calculations taking into account molecular weight distribution of paraffinic products gave the heat produced during FT synthesis of about 38 kcal per mol of reacted CO, actually close to former value.

Main side reactions together with their enthalpy follows [1]:

(c) methane formation: CO + 3 H2 ® CH4 + H2O
?H227 = – 214.8 kJ/mol

(d) Water gas shift reaction (WGSR): CO + H2O ® CO2 + H2
?H227 = – 39.8 kJ/mol

(e) Bell-Boudouard reaction: 2CO ® CO2 + C
?H227 = – 134 kJ/mol

W2 Energy’s FT reactor design is a continuous tubular fixed bed reactor (TFBR) providing the following advantages:

  • Simple to construct and operate
  • Can be used in wide ranges of pressure and temperature irrespective of whether the products are gaseous or liquids, or both.
  • No problem to separate liquid products from the catalyst.
  • Traces of catalyst poisons such as H2S, RSH in syngas are absorbed by the top layer of the catalyst bed, thus the remainder of the bed stays unaffected.W2 Energy's Fischer Tropsch System

The Unit is divided into high and low pressure zones. The high pressure zone contains the feed gas supply system (2, 4, 5), the gas heater (6), the Reactor (7), the hot (11) and warm (13) product accumulators. The low pressure zone contains cold trap (14) for collecting light hydrocarbons at 0°C, online gas chromatograph and gas flow meter (15).

The pressure in high pressure zone up to 20 bar is set by dome loaded pressure reducing regulator (2) and dome loaded backpressure regulator (3). Pressure is checked by gauges (1). High pressure nitrogen line to pressurize the pneumatically controlled pressure regulators (2, 3) is included in the scheme.

Once these regulators are adjusted to the desired pressure, their domes should be blocked in by the valves provided (these valves aren’t shown in the picture).

A valve should be provided to introduce nitrogen in syngas line before the Reactor. Before catalyst reloading, syngas flow should be cut off and the Reactor flushed with nitrogen to prevent explosive gas mixture formation.

Interconnecting piping in the Unit may done with 6.35 mm outside diameter, 0.89 mm wall thickness 316 stainless steel seamless tubing, the same as used in ZIOC lab. Tubes between heater (6) and the Reactor (7) as well as between the Reactor and hot accumulator (11) should be surrounded by heat isolating material for example glass wool. The valves in high pressure zone are provided with graphite packing witch allows high temperature use.

Hot product accumulator (11) and vertical tube connecting them with the Reactor are heated by cable heater up to 120°C temperature. Next product accumulator (12) is kept at ambient temperature. Cold trap (14) accumulates light hydrocarbons at 0°C temperature.

A line is provided which bypasses the Reactor and sends the gases directly to backpressure regulator (3). It is used for calibration of the rotameter (4) with the wet test meter (15). The use of the bypass line makes flow calibration more accurate.

Our FT diesel fuel produced from synthesis gas (CO and H2) through Fischer-Tropsch synthetic processes using coal as the feedstock is a high quality, low emissions diesel substitute. FT diesel fuel is characterized by a high cetane number, a near-zero sulfur content and a very low aromatic level. Studies conducted on unmodified diesel engines have shown that the exhaust emissions are reduced significantly with the use of FT diesel fuel. The CO, HC, NOx, smoke emissions from an unmodified diesel engine operating on FT diesel fuel were reduced simulta­neously when compared with those of conventional diesel fuel operation.

Advantages of FT diesel include:

  • FT diesel contains virtually no sulfur or aromatics. In a properly tuned engine this is expected to lead to lower particle exhaust emissions.
  • The absence of sulfur means that oxidation catalysts and particulate traps will operate at maximum efficiency.
  • The existing diesel infrastructure can be used, unchanged, for Fischer-Tropsch Diesel.
  • FT diesel can be used in existing diesel engines.
  • Diesel is one of the safest of the automotive fuels.
  • An FT plant does not produce any of the less desirable co-products from a refinery, such as heavy fuel oil or coke.
  • Provided an FT plant uses an oxygen feed, it produces a pure CO2 stream that provides an option for the collection and sequestration of CO2.