Katia Gallucci

Gas cleaning, gas conditioning and tar abatement by means of a catalytic filter candle in a biomass fluidized-bed gasifier

A bench-scale fluidized-bed biomass gasification plant, operating at atmospheric pressure and temperature within the range 800-820 degrees C, has been used to test an innovative gas cleaning device: a catalytic filter candle fitted into the bed freeboard. This housing of the gas conditioning system within the gasifier itself results in a very compact unit and greatly reduced thermal losses. Long term (22h) tests were performed on the gasifier both with and without the catalytic candle filter, under otherwise identical conditions. Analysis of the product gas for the two cases showed the catalytic filtration to give rise to notable improvements in both gas quality and gas yield: an increase in hydrogen yield of 130% and an overall increase in gas yield of 69% - with corresponding decreases in methane and tar content of 20% and 79%, respectively. HPLC/UV analysis was used to characterize the tar compounds.

Olivine, dolomite and ceramic filters in one vessel to produce clean gas from biomass

Heavy organic compounds produced during almond shells gasification in a steam and/or air atmosphere, usually called tar, are drastically reduced in the product gas by using simultaneously in one vessel a ceramic filter placed in the freeboard and a mixture of olivine and dolomite particles in the fluidized bed of the gasifier. The content of tar in the product gas during a reference gasification test with air, in presence of fresh olivine particles only, was 8600mg/Nm3 of dry gas. By gasifying biomass with steam at the same temperature level of 820°C in a bed of olivine and dolomite (20% by weight), and in the presence of a catalytic ceramic filter inserted in the freeboard of the fluidized bed gasifier, the level of tar was brought down to 57mg/Nm3 of dry producct gas, with a decrease of more than two orders of magnitude.

Cold model characterisation of a fluidised bed catalytic reactor by means of instantaneous pressure measurements

Abstract The analysis of instantaneous pressure fluctuations is utilised in a cold modelling study of a pilot scale fluidised bed catalytic reactor for ethane oxychlorination. It is demonstrated that the fluid dynamic behaviour of a cold model of this fine particle (Geldart group A) system is well characterised by the frequency spectrum, the standard deviation and the cross-correlation of pressure signals detected at different locations within the bed and in the freeboard. The influence of operating parameters, such as gas flow rate, initial bed height, reactor configuration (internals) and average value of the local pressure, is investigated, and a comparison is made with the features exhibited by Geldart group B systems (fluidised bed combustors) for which the same diagnostic techniques have been applied. Finally, the applicability to fine particle suspensions of literature correlations for dominant frequency and propagation velocity of pressure waves is discussed with reference to the combined influence of the eruption of many small bubbles at the bed surface, and the compressibility of the gas contained within the particle-bed interstices.

Characterisation of Tar produced in the Gasification of Biomass with in situ Catalytic Reforming

This paper concerns the cleaning of the hot gas produced by steam gasification of biomass in a fluidized bed. The cleaning takes place in a catalytic filter candle device placed directly in the freeboard of the bed. Such integration results in a compact processing unit and increased thermal efficiency; the result of the cleaning being carried out directly at the reactor outlet temperature. It thus lends itself to exploitation in distributed power generation systems utilizing renewable energy sources. Results are reported for runs performed in a bench scale fluidized bed steam gasifier fitted with a single full-size catalytic candle filter. Tar and particulates in the product gas were sampled in accord with technical specification CEN/TS 15439 with analysis by UV and fluorescence spectroscopy.

Influence of temperature on oxygen permeation through ion transport membrane to feed a biomass gasifier

Oxygen-permeable perovskite membranes with mixed ionic-electronic conducting properties can play an important role in the high temperature separation of oxygen from air. A detailed design of a membrane test module is presented, useful to test mechanical resistance and structural stability of Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) capillary membrane in the reactor environment. Preliminary experimental results of membrane permeation tests highlight the positive effect of temperature on perovskite materials. This behaviour is also confirmed by a computational model of char combustion with oxygen permeated through the membrane module, when it is placed inside a gasifier reactor to provide the necessary input of heat to the gasification endothermic process. The results show that the temperature affects the oxygen permeation of the BSCF membrane remarkably.

CO2 Sorption-Enhanced Processes by Hydrotalcite-Like Compounds at Different Temperature Levels

Abstract The aim of this work is to identify solid sorbents for CO2 capture for coal and biomass syngas conditioning and cleaning by means of a sorption-enhanced reaction process. Hydrotalcite-like compounds (HTlcs) were synthesized with and without K2CO3 impregnation. Samples were characterized by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) and Barrett–Joyner–Halenda (BJH) porosimetry after synthesis and after capture tests, respectively. Sorption and desorption tests were performed in a fluidized bed reactor, under cyclic conditions, at two different temperature levels: 350/450°C and 600/700°C. At low temperature only the Mg–Al HTlcs K promoted samples showed stability and sorption capacity comparable with literature values. On the other hand, results at high temperature indicate that the mixed Mg-Ca-Al HTlcs samples exhibit the best behavior with the highest sorption capacity (1.7 mmolCO2/g) almost stable over 5 sorption/regeneration cycles; furthermore, addition of steam allowed increasing their reactivity by 70% compared to the dry value. This type of sorbent could be a promising candidate to prepare a bifunctional sorbent–catalyst for sorption-enhanced processes, taking place directly in the fluidized bed gasifier, or downstream the reactor for adjustment of gas composition before further conversion in gaseous energy carriers.

CO2 Sorption by Hydrotalcite-Like Compounds in Dry and Wet Conditions

Abstract A pre-combustion removal option, coupling water–gas shift and CO2 capture is the well-known sorption-enhanced water–gas shift (SEWGS): the removal of CO2 produced by WGS reaction, shifting the thermodynamic equilibrium, enhances H2 production. Among the different CO2 sorbents, hydrotalcite-like compounds work at the required intermediate temperature (T = 200–400°C). Using low supersaturation method, three different sorbents were synthesized. Sieved fractions were impregnated with 20%w/w K2CO3 and then dried and subjected to thermal treatment. Sample characterization was performed by means of FT-IR spectroscopy, XRD analysis and TG-DTA analysis. Sample analysis was carried out after synthesis, thermal treatment (calcination) and after fixed bed reactor capture tests. Sorption and desorption tests were performed in a fixed bed microreactor, under cyclic conditions, at temperature level of T = 350°C and P = 5 bar in dry and wet condition. The amount of CO2 captured by the sorbent in each test was quantified by means of a first order with dead time flow distribution model applied to the experimental system. Sorption capacity of sorbents in dry conditions increases of 30% with respect to previous atmospheric pressure results obtained in fluidized bed. These sorbents seem to be good candidates to be used as a bi-functional sorbent-catalyst for SEWGS.

Biomass and Waste Gasification

The potential of biomass as an abundant and distributed source of energy has been extensively investigated in the last decades; this growing interest is due to the increasing attention to avoid greenhouse gases accumulating in the atmosphere. Among available biomass thermal conversion processes, the most feasible option, closest to industrial exploitation, is the gasification technology that produces a syngas rich of hydrogen, carbon monoxide and, at a lower content, methane. In addition to efficient power generation, it allows synthesis of commodity chemicals from a renewable source, adopting a so called polygeneration strategy. Despite the universally recognised environmental advantages, open issues remain the higher costs of power generation systems based on biomass with respect to fossil fuels, and technologic improvements of hot gas cleaning and conditioning devices to increase the efficiency of the utilization of thermal and chemical energy of the product gas.

Digesters, Gasifiers and Biorefineries: Plants and Field Demonstration

In the present chapter an indication is given of the degree of industrialization reached so far by the biomass and waste conversion technologies described in Chaps. 3 and 4. Anaerobic digestion is a consolidated technology, which is reflected by the vast diffusion of waste water treatment plants. However, there is great potential for increased exploitation of this technology, especially by utilization of the diverse byproducts from the process. The future of anaerobic digestion is therefore closely related to the development of the biorefinery concept. As regards gasification, the flexibility of possible feedstock and the many varieties of syngas production routes lead to a large number of demonstration sites, with only few plants commercially in operation. These are summarized according to technology and geographical location.

H2 from SERP: CO2 Sorption by Double-Layered Hydroxide at Low and High Temperatures

Sorption-enhanced processes of removing CO2 maximize hydrogen production. In this work, three kinds of CO2 sorbents were synthesized using a low supersaturation method and keeping the M2+/M3+ = 2/1 (M2+ = Mg, Ca and M3+ = Al). High- and low-temperature capture tests were carried out in a fluidized bed reactor and compared with thermogravimetric analysis. Differential thermal analysis was used to investigate the sorption behavior. Samples were characterized by means of Brunauer–Emmett–Teller (BET)Barrett–Joyner–Halenda (BJH), X-ray diffraction (XRD), scanning electron microscopy (SEM)energy-dispersive X-ray spectroscopy (EDX) analysis.