Correlation of the Minimum Spouting Velocity for the Design of Open-Sided Draft Tube Conical Spouted Beds for the Treatment of Fine Materials

The hydrodynamics of conical spouted beds provided with open-sided draft tubes have been studied for the treatment of fine particles. A correlation has been proposed for the calculation of the minimum spouting velocity as a function of dimensionless moduli that take into account the geometric factors of the contactor and the draft tube, particle characteristics and operating conditions

Development of the Conical Spouted Bed Technology for Biomass and Waste Plastic Gasification

Gasification is one of the most effective methods for upgrading different wastes, such as plastics and biomass, because the gas produced can be used directly as a fuel or as a renewable raw material for the production of chemicals and fuels. The conical spouted bed reactor (CSBR) has demonstrated to perform well in gasification process due to its specific features, such as (i) the cyclic and vigorous particle movement that avoids bed defluidization (a limitation in fluidized beds), (ii) capability for handling irregular or sticky solids, (iii) high heat transfer rates between phases, and (iv) bed stability in a wide range of gas flow rates. However, the conventional CSBR is characterized by its short residence time, which involves serious problems for minimizing tar formation. The incorporation of a fountain confiner in the CSBR is key to increasing the gas residence time and improving the contact between the gas and heat carrier particles, thereby promoting tar cracking reactions and so enhancing carbon conversion efficiency from 81.5% (without confiner) to 86.1% under fountain enhanced regime. The quality of the syngas is clearly improved as the H2 concentration increases from 36 to 42% with and without the fountain confiner, whereas that of CO decreases from 34 to 29%, respectively

A CONICAL SPOUTED BED REACTOR FOR THE VALORISATION OF WASTE TIRES

A pilot plant provided with a conical spouted bed reactor has been used for the valorisation of waste tires by thermal pyrolysis in continuous mode. The effect of pyrolysis temperature on product distribution and properties has been studied in the temperature range from 425 to 600 ºC. This variable has proven to have an important effect on product distribution. Thus, pyrolysis oil yield was reduced from 64.3 wt% at 425 ºC to 55.9 wt% at 600 ºC. However, the quality of carbon black was improved operating at high temperatures (increasing BET surface area values). High yields of certain interesting chemicals have been obtained in the liquid fraction, such as limonene (19.3 wt%), isoprene (5.7 wt%) and styrene (6.1 wt%)

Waste Plastics Valorization by Fast Pyrolysis and in Line Catalytic Steam Reforming for Hydrogen Production

This chapter summarizes the most recent results obtained in the plastic waste pyrolysis-reforming strategy for hydrogen production. An original two-reactor configuration consisting of a conical spouted bed reactor for the pyrolysis step and a fluidized bed reactor for the pyrolysis volatile reforming is proposed. The fundamental aspects and challenges of this joint process are discussed in detail, and the prospects for the full-scale implementation of this valorization route are assessed. Thus, the influence the main reforming parameters (temperature, space time and steam/plastic ratio) have in the pyrolysis-reforming of HDPE on product yields and catalyst stability are reported. Moreover, the role played by plastic composition on process performance is also described by studying the influence of following polymers: high density polyethylene (HDPE), polypropylene (PP), polyethylene terephthalate (PET) and polystyrene (PS). The operating conditions used for the valorization of different plastics have been as follows: pyrolysis temperature of 500°C, reforming temperature of 700°C, space time of 16.7 gcatalyst min gplastic−1and steam/plastic ratio of 4

The pyrolysis study of polybutadiene rubber under different structural and process parameters : comparison with polyvinyl chloride degradation

The effect of the initial cross-link, as well as process parameters, such as heating rate and temperature, was investigated on the pyrolysis of poly butadiene rubber (PBR) using a semi-batch stirred reactor and a TG equipment. To better evaluate the degradation mechanisms of polybutadiene rubber, the degradation of polyvinyl chloride was also investigated at similar heating rates using TG instrument. The results showed that due to the production of double bonds after HCl release, the pyrolysis of polyvinyl chloride proceeds similar to polybutadiene rubber. It is to note that in PBR pyrolysis, the degradation mechanisms were completely different under fast and slow pyrolysis, i.e., whereas slow pyrolysis follows a cross-linking mechanism and Diels-Alder reactions leading to cyclic products, fast pyrolysis promotes a chain scission mechanism, and therefore more aliphatic products are obtained. While PVC degradation involves three stages of HCl release, cross-link networks creation, and chain scission, respectively, with increasing heating rate, the intermediate stage is almost eliminated and PVC pyrolysis shows two obvious stages. Furthermore, as the cross-link of PBR was more severe, the liquid production was higher and the process time was longer, which significantly promoted char production. Moreover, the TG results of PBR and PVC are evidence that the ratio of cross-link and Diels-Alder over chain scission mechanism decreases as temperature and heating rate are increased. Thus, an increase in heating rate, and so operation under relatively fast pyrolysis conditions (above 90 K min(-1)), leads to PBR degradation at lower temperatures, which is evidence of the effect polymer structure has on the degradation

Conversion of HDPE into Value Products by Fast Pyrolysis Using FCC Spent Catalysts in a Fountain Confined Conical Spouted Bed Reactor

Continuous catalytic cracking of polyethylene over a spent fluid catalytic cracking (FCC) catalyst was studied in a conical spouted bed reactor (CSBR) with fountain confiner and draft tube. The effect of temperature (475–600 °C) and space‐time (7–45 g(cat) min g(HDPE) (−1)) on product distribution was analyzed. The CSBR allows operating with continuous plastic feed without defluidization problems and is especially suitable for catalytic pyrolysis with high catalyst efficiency. Thus, high catalyst activity was observed, with waxes yield being negligible above 550 °C. The main product fraction obtained in the catalytic cracking was made up of C(5)−C(11) hydrocarbons, with olefins being the main components. However, its yield decreased as temperature and residence time were increased, which was due to reactions involving cracking, hydrogen transfer, cyclization, and aromatization, leading to light hydrocarbons, paraffins, and aromatics. The proposed strategy is of great environmental relevance, as plastics are recycled using an industrial waste (spent FCC catalyst)

Valorization of waste eggshell for CO2 sorbents production by sol-gel citric acid treatment in a fixed-bed reactor

This study assesses the potential of the eggshells as a promising and alternative CO2 adsorbent. With the aim of enhancing the CO2 capture performance of raw eggshell, it was modified by sol-gel citric acid treatment. Both adsorbents were characterized by N2 adsorption-desorption, XRF, XRD and SEM techniques. Preliminary adsorption tests in TGA revealed that the acid-modified eggshell achieved significantly higher carbonation conversion than the raw eggshell adsorbent in the 650–750 ºC adsorption temperature range, reaching a carbonation conversion of 69% at 700 ºC. The cyclic performance of the modified eggshell, tested in TGA at 700 ºC under 15 vol% CO2, confirmed that sol-gel acid treatment led to a very stable adsorbent, with a slight improvement in CO2 adsorption capacity during the first four cycles (from 0.54 to 0.58 gCO2 gads−1), followed by stable performance due to self-reactivation phenomena. Moreover, additional experiments were carried out in a fixed bed reactor under more realistic conditions to study the influence of temperature (600–750 ºC) and CO2 flow rate (50–125 mL min−1) using the modified eggshell. An increase in temperature under 15 vol% CO2 stream led to a decrease in the carbonation conversion of the adsorbent, with the maximum CO2 uptake at 600 ºC (0.64 gCO2 gads−1). Regarding the role of the CO2 flow rate at 700 ºC, increasing from 75 to 125 mL min−1 CO2 had minimal effect, maintaining a capture amount of approximately 0.49 gCO2 gads−1. These results confirmed the potential of the acid-modified eggshell as a low-cost and environmental friendly adsorbent for CO2 capture, which indeed may significantly improve the economic feasibility of the CCUS processes