• Energy Research

A new two-stage gasifier with fixed-bed has recently been installed on CIRAD facilities in Montpellier. The pyrolysis and the gasifier units are removable. In order to characterise the pyrolysis products before their gasification, experiments were carried out, for the first time onlywith the pyrolysis unit and this paper deals with the results obtained. The biomass used is Pinus pinaster. The parameters investigated are: temperature, residence time and biomass flow rate. It has been found that increasing temperature and residence time improve the cracking of tars, gas production and char quality (fixed carbon rate more than 90%, volatile matter rate less than 4%). The increase of biomass flow rate leads to a bad char quality. The efficiency of tar cracking, the quality and the heating value of the charcoal and the gases, indicate that: temperature between 650 °C and 750 °C, residence time of 30 min, biomass flow rate between 10 and 15 kg/h should be the most convenient experimental conditions to get better results from the experimental device and from the biomass pyrolysis process. The kinetic study of charcoal generation shows that the pyrolysis process, in experimental conditions, is a first-order reaction. The kinetic parameters calculated are comparable with those found by other researchers. (Resume d'auteur)

Abstract Performance of wood gasification genset is sensitive to the moisture content in the feedstock and the electrical load (demand of users). This study investigates the influence of these process parameters on the electrical efficiency of the genset (ηglobal), the electrical engine efficiency (ηengine), the cold gas efficiency (CGE), and the syngas composition. Experimental tests were carried out by varying the moisture content from 11% to 23% and the electrical power from 4.7 kW to 12.8 kW on a commercial gasifier equipped with precise measuring tools. The increase of the performance when the electrical load is increased or when the moisture content in the wood chips is decreased is both quantified and discussed. Such behaviour was mainly explained by differences in engine filling rates and reactor temperatures.

Substitution of fossils reducers by charcoal from woody biomass is one of the most suitable option to reduce greenhouse gas emissions of metallurgical industries. The main problem involved in fossils reducers replacement is the lack of mechanical strength of charcoal. Aim of this study is to investigate the impact of pyrolysis parameters, such as temperature and solid residence time, on the mechanical properties of charcoal. Charcoal was produced from two woody biomasses, Eucalyptus globulus and Picea abies (Spruce), in a pilot scale fixed bed rector; with three temperatures (500, 650 and 800 °C) and two solid residence times (0 and 90 min). The particle sizes used were close to those in the industry. Charcoals were characterized by proximate and ultimate analysis, apparent density, friability and compressive strength. Results show an increase in charcoal mechanical strength with increasing pyrolysis temperature. On the other hand solid residence time has a little influence on the mechanical properties. Eucalyptus has a higher density than Spruce, but Eucalyptus charcoal shows a lower mechanical stability than Spruce charcoal independently of the pyrolysis conditions. Proceedings of the 26th European Biomass Conference and Exhibition, 14-17 May 2018, Copenhagen, Denmark, pp. 1240-1243

Ex situ hot gas filtration (HGF) has been shown to be a simple and robust technique to upgrade the quality of flash pyrolysis oils. In this study, the secondary reactions inside the HGF unit and their impact on product yields and the chemical composition of bio-oils were investigated in a total of 18 experiments conducted at both pilot and bench reactor scales (1 and 0.1 kg/h), with beech wood (BW) and sunflower stalks (SFS). The impact of HGF on yields was found to be dependent on the extent of secondary reactions which, in turn, were determined by three parameters: (a) HGF temperature, (b) HGF char cake thickness, and (c) AAEM content of the raw feedstock. Nevertheless, independently of the conditions used, the drop in the organic yield was less than 10 wt % with both BW and SFS feedstocks. Our results demonstrated that (1) cracking reactions mainly took place in the homogeneous gas phase and (2) dehydration, coking, and decarboxylation reactions took place in the HGF char cake, probably catalyzed by th...

The effects of important practical parameters, specifically feedstock heterogeneity and heat-mass transfer on steam gasification of rice husk were investigated and quantified. Through proximate and ultimate analysis of ten rice husk types, the heterogeneity was expressed not only between different types but also within the same rice husk type. TGA-DTG curves showed notable differences in the thermal behaviors of rice husk during pyrolysis. The time required to gasify the same quantity of rice husk can vary in a ratio of 1–1.5 depending on the type. The Si content in rice husk showed an inhibitory effect to the char reactivity during steam gasification. An empirical factor of 1.3 could be applied to the conversion rate of rice husk for every 1-cm increase in the bed thickness. Results of this study could contribute to the improvement of existing systems or the design of new efficient rice husk gasifiers.

Oxidative pyrolysis of pine wood particles was analysed thermo-gravimetrically. The effects of the concentration of oxygen in the surrounding gas and of particle size were investigated. Three different oxygen concentrations (0%, 10% and 20% v/v) and three different sized cylindrical pine wood samples (4 mm, 8 mm and 12 mm in diameter and 15 mm long) were tested. Two types of Macro-TG apparatuses were used; the first was non isothermal and was used at a heating rate of 20 degrees C/min, and the second was isothermal used at two temperatures, 400 degrees C and 600 degrees C. In the low heating rate non isothermal apparatus, results showed that oxygen had a strong influence on pyrolysis behaviour, but particle size did not. In the high heating rate isothermal apparatus, particle size had a significant influence on conversion: transfer phenomena limit oxidative pyrolysis.

Bã mía là nguồn nguyên liệu tiềm năng cho khí hóa với tác nhân hơi nước, nhưng kiến thức về công nghệ này vẫn còn hạn chế và phân mảnh. Tốc độ gia nhiệt là một trong những yếu tố quan trọng nhất ảnh hưởng đến quá trình khí hóa. Tuy nhiên, thông số này vẫn chưa được nghiên cứu đầy đủ. Trong nghiên cứu này các đặc tính của bã mía cùng than làm từ bã mía đã được xác định, và ảnh hưởng của tốc độ gia nhiệt đến động học của quá trình khí hóa đã được nghiên cứu. Bã mía chứa hàm lượng tro thấp, tương đồng với gỗ nên có lợi trong các quá trình khí hóa. Than làm từ bã mía có nhiệt trị cao, tương đương với than đá. Tốc độc gia nhiệt thay đổi nhỏ từ 5 lên đến 15 °Cmin-1 không gây ảnh hưởng tới tốc độ chuyển đổi, trong khi một sự thay đổi lớn từ 15 lên đến 1800 °Cmin-1 gây ảnh hưởng đáng kể đến động học khí hóa hơi nước. Than sản xuất ở tốc độ gia nhiệt cao làm tăng tốc độ chuyển hóa lên 1,35 lần so với than sản xuất ở tốc độ gia nhiệt thấp. Kết quả và dữ liệu của nghiên cứu có thể hữu ích cho việc phát triển các hệ thống khí hóa mới sử dụng bã mía, ví dụ như các hệ thống khí hóa nhiều tầng có tầng làm than được tách biệt với tầng khí hóa.

Abstract This paper deals with a new method to calculate the higher heating value (HHV) of pyrolysis oils by using the analysis results of their gas chromatography–mass spectrometry or high-pressure liquid chromatography. This new method is called “GC–MS method” or “GCM”. The HHV which is calculated by this method is compared to the one given by the researchers (generally obtained by bomb calorimeter) on the one hand and those of Dulong’s and Vondracek’s formulae on the other hand. The results show that GCM and Vondracek are generally in a good agreement with the experimental values than those obtained with Dulong’s formula.