Brian Kelleher

Review of literature on catalysts for biomass gasification

Biomass gasification is a possible alternative to the direct use of fossil fuel energy. Biomass, a CO2 neutral source of renewable fuel, can contribute to the demand for heat, electricity and synthesis gas. However, there are inefficiencies in the technology, which at present render biomass gasification economically unviable. The presence of condensable organic compounds and methane in the product gas renders the gas unsuitable for specific applications. Elimination of the condensable organic compounds and methane by a suitably cheap technology will enhance the economic viability of biomass gasification. This paper contains an extensive literature review of the three main groups of catalysts, which have been evaluated for the elimination of these hydrocarbons. These three groups of catalysts are dolomite, alkali metals and nickel.

Advances in poultry litter disposal technology--a review.

The land disposal of waste from the poultry industry and subsequent environmental implications has stimulated interest into cleaner and more useful disposal options. The review presented here details advances in the three main alternative disposal routes for poultry litter, specifically in the last decade. Results of experimental investigations into the optimisation of composting, anaerobic digestion and direct combustion are summarised. These technologies open up increased opportunities to market the energy and nutrients in poultry litter to agricultural and non-agricultural uses. Common problems experienced by the current technologies are the existence and fate of nitrogen as ammonia, pH and temperature levels, moisture content and the economics of alternative disposal methods. Further advancement of these technologies is currently receiving increased interest, both academically and commercially. However, significant financial incentives are required to attract the agricultural industry.

Combustion of poultry litter in a fluidised bed combustor

Abstract Combustion studies of poultry litter alone or mixed with peat by 50% on weight basis were undertaken in an atmospheric bubbling fluidised bed. Because of high moisture content of poultry litter, there was some uncertainty whether the combustion could be sustained on 100% poultry litter and as peat is very available in Ireland; its presence was considered to help to improve the combustion. However, the results showed that, as long as the moisture content of poultry litter was kept below 25%, the combustion did not need the addition of peat. The main parameters that were investigated are (i) moisture content, (ii) air staging, and (iii) variations in excess air levels along the freeboard. The main conclusions of the results are (i) combustion was influenced very much by the conditions of the fuel supply, (ii) the steady fuel supply was strongly dependent on the moisture content of the poultry litter, (iii) temperature appeared to be still very influential in reducing the levels of unburned carbon and hydrocarbons released from residues, (iv) the air staging in the freeboard improved combustion efficiency by enhancing the combustion of volatiles released from residues in the riser and (vi) NOx emissions were influenced by air staging in the freeboard. Particles collected from the bed and the two cyclones were analysed to determine the levels of heavy metals and the leachability tests were carried out with ashes collected to verify whether or not they could safely be used in agricultural lands.

Investigation of nickel supported catalysts for the upgrading of brown peat derived gasification products

Abstract A gasification test rig was designed in which peat was gasified under nitrogen over a temperature range 25–550°C at 5° C min −1 . The gasification unit resulted in 35.5 wt% of the carbon present in the peat being converted to a volatile fraction. The volatile fraction was transferred to a secondary catalytic reforming reactor at 800°C. The thermal effect of the second reactor resulted in an increase in the CO, CO2 and CH4 content of the volatile fraction, a syngas ratio of 0.75 and a higher heating value (HHV) of 26.5 MJ kg −1 . Several nickel-supported catalysts were investigated with the intention that they should give an increase in the conversion of the condensable hydrocarbons in the volatile fraction to CO, CO2 and CH4, and a resultant gas stream suitable for use in an integrated gasification combined cycle plant (IGCC) (i.e. syngas ratio 2:1, low methane content and better HHV). Alumina-supported nickel catalysts investigated gave the highest activities and co-precipitated Ni/Al catalysts were most active. A Ni/Al 3:17 catalyst increased the conversion of the hydrocarbons to 91.5%, gave a syngas ratio of 1.81:1, increased the HHV by a factor of 5.3 and completely eliminated methane from the gas stream.

Emissions modeling of fluidised bed co-combustion of poultry litter and peat

Gaseous emissions from the fluidised bed co-combustion of 50% w/w chicken litter and peat were monitored and recorded. Emission data were used to create a dispersion model for a proposed site on a poultry farm in Ireland. Variables within the combustion unit influenced both combustion and emission levels of pollutants such as SO(2) and NO(x), CO. Concentrations of atmospheric pollutants decreased with use of the correct ratio between fluidising and secondary air. Dispersion modelling of combustion at a proposed poultry unit predicted that ground level concentrations for the set of emissions data would be below the limits and guidelines set by air quality standards.

Catalytic conditioning of organic volatile products produced by peat pyrolysis

A series of metal oxides were investigated for up-grading the quality of the product gas from peat pyrolysis. The designed test rig pyrolysed brown peat in a nitrogen atmosphere at 550°C. This resulted in of the carbon present in the peat being converted to a volatile fraction. The volatile fraction was transferred to a secondary catalytic reforming reactor, at 800°C, which was located downstream from the gasifier. The thermal effect alone of the second reactor resulted in an increase in the CO, CO2 and CH4 content of the volatile fraction, a synthesis gas ratio of 0.75 and a HHV of . A selection of metal oxides (Al2O3,SiO2,ZrO2,TiO2) and MOR1 investigated in the secondary reactor at 800°C showed an increase in the quality of the product gas. Notably TiO2 increased the conversion of the hydrocarbons present in the gas stream to 79.5%, resulting in a synthesis gas ratio of 2.22 and increased the HHV by .

Monitoring and dispersion modelling of emissions from the fluidised bed combustion of poultry litter.

Gaseous emissions from the fluidised bed combustion of chickenlitter were monitored and recorded. Emission data was used tocreate a dispersion model for a proposed site on a poultry farmin Limerick, Ireland. Variables within the combustion unit notonly influenced combustion but also emission levels ofpollutants such as SO2 and NOx. CO emissions decreased withuse of the correct ratio between fluidising and secondary air,the staging of secondary air and the degree of turbulence withwhich the secondary air is introduced. Dispersion modelling ofactual combustion at a proposed poultry unit predicted thatground level concentrations for the set of emissions data wouldbe below the limits and guidelines set by air quality standards.This was true for both and line source. Line sourceconcentration levels were less than those for point source.

An Investigation into the Adsorption Characteristics of Grafted Mesoporous Silicates for the Removal of Tetramethyl Ammonium Hydroxide from Aqueous Solution

Four cubic mesoporous silicates (CMS), one unmodified and three grafted with amine, carboxylic and cyano surface functional groups, were prepared, characterised and compared as adsorbents for tetramethyl ammonium hydroxide (TMAH) from aqueous solution. The adsorption process was studied as a function of molecular size and CMS pore volume. Sorption on the unmodified, cyano- and carboxylic-grafted adsorbents closely followed the Langmuir model while adsorption on the amine-treated silicate conformed to the Freundlich model. A comparison of the adsorbent pore volume and the volume of sorbed TMAH molecules suggested that monolayer sorption occurred, there being some evidence that surface functional groups influenced the adsorption process. The presence or absence of structural order, as defined by X-ray diffraction analysis, had no significant influence on the adsorption, as all materials, both ordered and disordered, had relatively high adsorption capacities.

Utilisation of a Mesoporous Silicate Material for the Removal of Quaternary Ammonium Hydroxides (QAHs) from Aqueous Solution

A cubic mesoporous silicate (CMS) was prepared, characterised and assessed as an adsorbent for quaternary ammonium hydroxides (QAHs) from aqueous solution. The adsorption process was studied as a function of molecular size and CMS pore volume. Sorption closely followed the Langmuir model. A comparison of the CMS pore volume and the volume of the sorbed molecules suggested that monolayer sorption occurred and that the number of molecules sorbed was a function of the size of the quaternary ammonium hydroxide molecule and the threshold area capable of being occupied by this molecule.