Conversion of Natural Gas to Energy through PEMFC to Apply at Commercial Application

Conversion of Natural Gas to Energy through PEMFC to apply at Commercial Application

Vaishali Umrigar, Abhi Soni*, Hiralkumar Morker, Naim Memon

Chemical Engineering Department,

Sarvajanik College of Engineering & Technology, Surat, India.

*Email:soni.abhi705@gmail.com

Due to depletion of fuel and the scarcity of crude in coming years, inclination towards alternative energy sources lead us to think for an alternative to the existing fuels’ replacement. Also as many industrial processes, combustion processes releases excess amount of natural gas. This amount of natural gas is burned off or flared in the atmosphere. Much of such gas is being wasted which worth billions of dollars. Hence Natural gas can be utilized for the energy production and alternative to fuels’ for automobile Industries. To fulfil this objective, the scope of the study targets the following project execution at application level.

1)      Separation of Hydrogen from Natural Gas

2)      Synthesis of Polymeric membrane

a.       Synthesis of Nafion Membrane

b.      Synthesis of alternative to Nafion membrane

c.       Modification of existing Nafion synthesis process

3)      Assemble the Polymeric electrolytic material Fuel Cell (PEMFC) for Electricity generation

4)      Energy production trials and engine performance with Natural gas as a fuel

Each process from literature and well established mechanism has been explained in detail:

Step: 1

        i.            Removal of H₂S from Natural gas: - In natural gas two types of sulphur content are present such as H₂S and organic sulphur. H₂S is absorbed by zinc oxide. Organic sulphur is converted into inorganic sulphur (H₂S) by CoMoX (Cobalt Molybdenum Oxide) and absorbed. Many processes are available to remove Hydrogen sulphide.

      ii.            Reforming of gas to convert hydrocarbons into H₂ gas: - In reformer, natural gas is heated at high temperature (800-850 ⁰C) with steam to convert methane into hydrogen with CO & CO_2.  Separation of H₂ in a pure form can be achieved by the following mechanism.

    iii.            Conversion of CO to CO₂:- To remove CO, it can convert into CO₂ by reacting it with steam at high temperature and where more yield of H₂ is achieved.

    iv.            Removal of CO₂:- After conversion of CO into CO₂ and less amount of H₂S, it can absorbed by Benfield solution (K₂CO₃) and form bicarbonate and bisulphide. Hence pure H₂ is ready for the use in for the process.

After this 4 step process hydrogen is formed and can be used in PEMFC for electricity generation.

Step: 2

In PEMFC, membrane is main component to transfer electrons for production of electricity. Now a day, Nafion is mainly used as PEM because of its better chemical stability, higher conductivity and oxidative stability. The most successful result of Nafion is its lifetime, which is four times higher than the crossed-linked polystyrene membranes about 50000 hours at 80 °C.

Nafion synthesis:

Nafion is synthesized in four steps process as shown below:

        i.            Reaction of tetrafluoroethylene with SO₃ to form cyclic sulfone

      ii.            Condensation reaction with Na₂CO₃ followed by the copolymerization of perfluoro vinyl ether sulfonyl fluoride with tetrafluoroethylene to afford an insoluble thermoplastic resin

    iii.            Hydrolysis of sulfonyl fluoride extruded film to form a perfluorosulfonic polymer

    iv.            Exchange of sodium counter ion with a proton in a suitable electrolyte

Due to serious disadvantages of high cost, low operating temperature (<80 °C), and high fuel crossover, various research groups have focused to develop some alternative polymer materials. Polymeric electrolytic materials (PEM) with low cost of synthesis and better performance under fuel cell operating conditions can be the alternative to overcome these drawbacks. These materials include sulfonatedpoly (phenylene oxide), polysulfone, sulfonated poly (ether-ether ketone), sulfonated poly (benzimidazole), phosphoric acid doped polybenzimidazole, and sulfonated polyimide. Polymeric materials such as sulfonated poly (arylene ether ether ketone) (PEEK) and polysulfones (PS) show good chemical and thermal stabilities under the real fuel cell conditions but they have the disadvantage of lower proton conductivities due to the weak acidity of the aryl sulfonic acid group than Nafion.

These are the alternatives of Nafion membrane but the cost of Nafion can also reduce by modification in process. The modification in process of Nafion is by Sol-gel method using SiO₂ which can increase characteristics and also the cost of production. Therefore, to find out alternative of Nafion is quite challenging for better optimization of PEMFC.

Objective will be satisfied by the modification in Nafion synthesis with economical process.

Step: 3

Once pure H₂ from natural gas is extracted and proper alternative for synthesis of modified nafion is identified with trial and error by doing experiments, the next target is assembling of this to frame the PEMFC as per the process available. It is formed with anode-cathode plate for the flow of O₂ and H₂ to produce heat and electricity.

The process deals again with feasibility check and experiments done with the installed set up. The small-lab scale set up will be commissioned at the college and the experiments will be performed based on the target objective. This project the group has targeted to present as their UG project as a part of graduation. It will be more focused on end application of this study.

The basic aim of this project is to generate electricity using PEMFC with natural gas as feed. Proton Exchange Membrane Fuel Cell (PEMFC) for is chosen due to its favourable characteristics. For efficient way of natural gas conversion to energy, PEMFC proposed has high efficiency of electricity production. Different operating parameters will be identified such as surface area, temperature, pressure, flow rate, concentration with a fruitful design of the system. The expected efficiency of above mentioned fuel cell is 45-60% when operated on optimum parameters.

Figure 1 : PEMFC assembly

 Step: 4

Applications need the stability and efficiency of the PEMFC to generate energy from Natural gas. Sources of PEM will be tried first to compare the efficiency. Then Fuel Cell (FC) will be assembled with a high capacity to replace fuel engine in automobile. Engine performance only can give final application to move beyond our explanation of this project. Target till assembly will be completed by December 2018. And trials and data will be generated by March 2019. The new abstract can further submitted with data inputs with energy production and PEMFC efficiency.

Keywords: Natural gas, PEM, PEMFC, Nafion, Feasibility