Proyecto VA191U14

Study of the process for obtaining methanol, hydrogen and Fischer-Tropsch diesel, from syngas from energy crops 

Ref.: VA191U14

Introduction.

The total consumption of hydrocarbons, oil and natural gas in final energy represents 62.8% of the total in 2014 (SEE, 2014), this figure being higher than the average of the countries in the economic environment, and making it necessary to redouble efforts in diversification and energy saving, to reduce as much as possible this excessive dependence on hydrocarbons, which weigh down the trade balance, depending excessively on the outside, since the internal production of hydrocarbons does not even reach 0.2% of the needs.

In this context, lignocellulosic biomass gasification processes are among the most promising technologies, since it allows obtaining a synthesis gas (syngas) that can be used both to obtain a wide range of 2nd-grade biofuels. generation (synthetic diesel or Fischer-Tropsch diesel, methanol, hydrogen, dimethyl ether or DME, etc.). Furthermore, unlike other Renewable Energy technologies, they allow the use of a wide variety of raw materials (forest residues, herbaceous, liquid carbonaceous residues, etc.), which do not compete with the food markets (as is the case of the biodiesel obtained from vegetable oils).

Another important advantage it presents is its versatility, since syngas can be used not only for the synthesis of biofuels, but also for obtaining other types of compounds (plastic derivatives, ammonia, etc.), as well as for the generation of electric power. In addition, the thermal energy of the different streams of the process can be used to generate heat and cold.

However, today, its development requires an extensive research program that, among others, must cover the following points:

• Increase the flexibility and versatility of gasification systems in order to take advantage of both herbaceous and woody biomass, and obtain different products in the same equipment. There is little experimentation with regard to gasification processes in the same reactor aimed at obtaining different products using different types of raw materials, however, its development will greatly increase the flexibility and viability of these facilities.
• Improve gas cleaning systems, in order to meet the high requirements that are required both for its use as synthesis gas, and for obtaining electrical energy. Today and in some cases, these requirements have forced the use of water washing systems, with the consequent increase in the cost of the process by generating a waste that requires a highly expensive subsequent treatment.
• Development of models that allow to simulate the complex processes that take place in gasification reactors, as well as in the synthesis processes of different biofuels.

The Project focuses precisely on the study of these lines, developing both at laboratory and pilot plant level a systematic study of the different processes involved (bubbling fluidized bed gasification, gas cleaning and synthesis of 2nd Generation biofuels), as well as its corresponding modeling.

Goals.

The main goal of the Project is to contribute to developing a technology that allows the joint or individual obtaining of alternative biofuels (Fischer-Tropsch diesel, methanol and hydrogen) and electrical energy, through the application of gasification processes to biomass from energy crops ( thistle and poplar), applying green chemistry procedures that allow minimizing and / or revaluing the waste generated.

The development of biofuels from biomass can be obtained from forest and agricultural residues, but ultimately they require a constant and stable supply of raw material, in this sense energy crops play an essential role, an example of this type of crops can be thistle and poplar, which due to their characteristics can be used in different areas of Castilla y León.

Figura 3. Biomasas empleadas

Main advances and conclusions.

• Kinetic models of thermal degradation in inert atmosphere of these two species (thistle and poplar) have been developed, in order to characterize the initial pyrolysis stage, which is the initial stage of any gasification process in which tars are generated. initials.

Figure 34. Experimental data and model of the Tar during the devolatilization of thistle.

• Gasification tests have been carried out in a bubbling fluidized bed, varying the Equivalent Ratio (ER) and the type of gasifying agent, determining the amount of tar generated and the composition of the gas. The main conclusions of this study have been:
  • As the ER value and therefore the temperature increase, the total tar concentration decreases.
  • The following families also decrease with ER: 1 and 2 ring aromatics, phenol, cresols, oxygenated heteroaromatics.
  • As the ER increases, however, the gases concentrate on recalcitrant compounds such as: benzene, naphthalene, and compounds with 3 and more than 4 aromatic rings.
  • From the point of view of the gasifying agent and the production of tars, the one that generates the least amount is enriched air, followed by air and finally the vapor / air mixture.
  • The use of oxygen comparatively reduces the concentration of recalcitrant compounds.
  • These data reinforce the conclusion that the most suitable type of gasifying agent is enriched air, using a 0.3-0.4 stoichiometric ratio.

• Tar removal tests have been carried out with various bio-solvents, in order to eliminate tar remains, finding that the most suitable bio-solvent in this case was residual sunflower oil.

• A modeling of the gasification process for the production of syngas has been carried out using MATLAB. The model developed is based on non-stoichiometric equilibrium models, since this type of model
  allows knowing the composition of the gas generated based on the input variables: Composition of the biomass, type and composition of the gasifying agent, ER ratio, and operating temperature.

Figure 7. Simulation of the composition of the syngas during the gasification of the poplar with enriched air and ER = 0.3.

• A model has been made in ASPEN, which allows simulating the production of the three biofuels (methanol, hydrogen and Fischer-Tropsch diesel) using ASPEN.

Figure 110. Simplified diagram of the process for the synthesis of methanol, hydrogen and diesel Fischer-Tropsch

• As a result of the project, it is observed that in order to increase the viability of biorefineries, and favor their adaptation to the market, it is very useful to design facilities that allow the joint generation of various biofuels.
• The viability of facilities of this type, however, is estimated to be above the consumption of 950,000 t / year of biomass, which can be a challenge for their development. This difficulty can be solved through the joint use of biomass waste and energy crops close to the facility.

Publications.

• Steam reforming of model tar compounds over nickel catalysts prepared from hydrotalcite precursors. Díez, A. Urueña, R. Gil, F. Corona, G. Antolín. 5^th International Conference on Sustainable Solid Waste Management. ATHENS 2017. 21–24 June 2017.

http://uest.ntua.gr/athens2017/proceedings/pdfs/Poster_Athens2017_Diez_Uruena_Gil_Corona.pdf

• Determination of cellulose, hemicellulose and lignin content of different biomass species by a unique kinetic model from TGA analysis. A. Urueña, D. Díez, G. Antolín, J.A. Conesa. 5^th International Conference on Sustainable Solid Waste Management. ATHENS 2017. 21–24 June 2017.

http://uest.ntua.gr/athens2017/proceedings/pdfs/Poster_Athens2017_Uruena_Diez_Conesa.pdf

• The pyrolytic behavior of evolved gases and tar from energy crops. D. Díez, A. Urueña, G. Antolín.
• Pyrolysis Kinetic of thistle D. Díez, A. Urueña, G. Antolín.

References.

SEE. Energy in Spain 2014. 2014. Ministry of Industry, Energy and Tourism, Secretary of State for Energy (SEE).

Thanks.

The Project "Study of the process for obtaining methanol, hydrogen and Fischer-Tropsch diesel, from syngas from energy crops", with Ref. VA191U14:, has been financed by the Consejería de Educación de la Junta de Castilla y León in the call for research project to start in 2014.