Conception et caractérisation expérimentale d'un réacteur de gazéification pour l'Afrique de l'Ouest

Gasification is a thermochemical conversion process of biomass. Gasification is used for heat and power generation applications. This process is promising in a West African environment where energy needs are significant and where biomass potential is considerable. The aim of this study is the valorization by gasification of agricultural residues especially rice husk. It resulted to a design and a manufacture of a gasification reactor suitable for small-scale industrial units in the agricultural processing sector. This study is divided into several stages, namely a design methodology of the prototype, an equilibrium modelling of the gas composition, a simulation of the process heat losses and an experimental study of the prototype. Several parameters have been studied experimentally, namely the equivalence ratio, the air injection levels as well as the fuel supply mode. The produced gas was analyzed in order to determine the operating conditions to obtain the best yield of gasification. The best experimental results were carried out at an equivalence ratio of 0.32 for a thermal power of 50 kWth[LHV] and a global efficiency of 46 %. The composition of the produced gas is 14.62 % of CO, 12.89 % of CO2, 2.89 % of CH4 and 6.84 % of H2. These results with a relatively low yield are explained by the low process temperatures and a cold reduction zone. In fact, the heat losses estimated at 8 % of the energy balance of the exiting entities of the reactor, but they are probably higher. Some operational difficulties such as the homogenization of the bed during gasification lead to the formation of bypass where the pyrolysis gases are entrained towards the outlet. This also explains the proportions of the gas obtained with low CO and H2 contents. The experimental campaign carried out on the gasifier allows to issue perspectives to improve yields for future work.(SC - Sciences) -- UCL, 202

Design of a Gasification Reactor for Manufacturing and Operation in West Africa

This paper introduces the design of a biomass gasification reactor with specific constraints for its manufacturing and operation in the West African conditions. The foreseen applications are the valorisation into heat and electricity of agricultural biomass residues. Rice husk is chosen as the reference fuel for the design. Local manufacturing is a key feature and the main focus of the design, as it allows us to reduce the capital costs and facilitate the maintenance. The design methodology is based on the conceptual approach proposed by Cross. This approach leads in several steps to a rational design choice based on the evaluation of different solutions. In this study, nine reactor types have been compared leading to a prototype that best suits the defined objectives such as a local manufacturing, a secure installation and a sufficient gas quality. From this conception approach, the Semi-Batch, Fixed-bed reactor with air Aspiration appears the most suitable. Its specific characteristics for the foreseen application are a power of 44 kW based on the syngas lower heating value, an average fuel consumption of 20.38 kg/h and an average air flow of 28.8 kg/h for optimal gasification. The gasifier resulting from the design methodology has been built. It is presented in the paper

Design of a Gasification Reactor for Manufacturing and Operation in West Africa

This paper introduces the design of a biomass gasification reactor with specific constraints for its manufacturing and operation in the West African conditions. The foreseen applications are the valorisation into heat and electricity of agricultural biomass residues. Rice husk is chosen as the reference fuel for the design. Local manufacturing is a key feature and the main focus of the design, as it allows us to reduce the capital costs and facilitate the maintenance. The design methodology is based on the conceptual approach proposed by Cross. This approach leads in several steps to a rational design choice based on the evaluation of different solutions. In this study, nine reactor types have been compared leading to a prototype that best suits the defined objectives such as a local manufacturing, a secure installation and a sufficient gas quality. From this conception approach, the Semi-Batch, Fixed-bed reactor with air Aspiration appears the most suitable. Its specific characteristics for the foreseen application are a power of 44 kW based on the syngas lower heating value, an average fuel consumption of 20.38 kg/h and an average air flow of 28.8 kg/h for optimal gasification. The gasifier resulting from the design methodology has been built. It is presented in the paper

First digital characterization of the transhumance corridors through Benin used by cattle herds from Burkina Faso and associated risk scoring regarding the invasion of Rhipicephalus (Boophilus) microplus.

BACKGROUND: Livestock plays a key role in the macro economy of West Africa and provides livelihoods for millions of people. The main cattle rearing strategy in West Africa is pastoralism, including transhumance: i.e. a seasonal migration of cattle with their herders. This adaptive strategy aims to optimize livestock access to water and pastures. However, it can favour pathogens and vectors transboundary spread. This study aim is to highlight, firstly the corridors and grazing areas used by Burkina Faso transhumant cattle herds going to Benin, secondly the characteristics of departure and arrival areas of transhumance and thirdly, the risk score related to introduction and spread of the invasive tick species, Rhipicephalus (Boophilus) microplus, in free areas. METHODS AND PRINCIPAL FINDINGS: Therefore, GPS devices were given to 27 herders to monitor a full transhumance season between East Burkina Faso and North Benin. The analysis of 14,966 spots generated by the GPS devices revealed four main corridors and five main grazing areas used by cattle herds during transhumance. Statistical analysis of normalized difference vegetation index (NDVI), rainfall and temperature data, highlighted significant differences between departure and arrival areas. NDVI and rainfall are significantly higher in Benin than Burkina Faso whereas temperature is significantly lower. Additionally, using biotic and abiotic parameters, a risk scoring was developed to predict the presence of Rhipicephalus (Boophilus) microplus at municipality level. CONCLUSIONS AND SIGNIFICANCE: The better vegetation, temperature and rainfall conditions during the dry seasons in Benin attract cattle herds from Burkina Faso. The invasiveness and adaptability of Rhipicephalus (Boophilus) microplus added to the frequent stays of transhumant herds in infested areas suggest its potential introduction and establishment in free areas soon. Moreover, frequent intrusions of the transhumant cattle in the wildlife reserves is another risk of vectors and pathogen exchange between domestic and wild animals