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Chemical Looping Combustion (CLC) is a promising novel combustion technology involving inherent separation of carbon dioxide with minimum energy penalty. An oxygen carrier is employed to continuously transfer oxygen from the air reactor to the fuel reactor where the oxygen is delivered to the fuel. Consequently, direct contact between the air and fuel is prevented. The resulting flue gas is CO2-rich, without N2 dilution. The reduced oxygen carrier is then transported back to the air reactor for re-oxidation purposes, hence forming a chemical loop. Various CLC configurations have already been developed and tested on laboratory scales. However, more investigations are required to achieve feasible CLC processes. Among the different points to address, control of the solid circulation rate between the two reactors is of the highest importance regarding its effect on achievement of an appropriate oxygen transfer rate and solid oxidation degrees. Moreover, minimization of gas leakage between the fuel and air reactors is another important issue to be considered. A novel CLC configuration is proposed where reactions are carried out in two interconnected bubbling fluidized beds. Solid circulation rate control is achieved independently of gas flow rate in the reactors through use of pneumatic non-mechanical valves (L-valves). Moreover, loopseals are employed to minimize gas leakage while transferring solids. Experimental results from operation of a 10 kWth equivalent cold prototype are presented in this paper. The effect of operating variables on the solid circulation rate, gas leakage between the two beds and the pressure balance on all of the process elements is studied. The results demonstrate stable solid circulation with efficient control of the solid flow rate and effective gas tightness of the system. La combustion en boucle chimique (CLC) est une nouvelle technologie prometteuse qui implique la separation inherente du dioxyde de carbone avec une perte minimale d’energie. Un transporteur d’oxygene est utilise pour le transfert de l’oxygene en continu du “reacteur air” vers le “reacteur fioul” ou l’oxygene est apporte au combustible. Ainsi, le contact direct entre l’air et le combustible est evite. Le gaz resultant est riche en CO2 et n’est pas dilue avec de l’azote. Le transporteur d’oxygene reduit est ensuite transporte vers le reacteur air afin d’etre re-oxyde, formant ainsi une boucle chimique. Diverses configurations CLC ont deja ete developpees et testees a l’echelle laboratoire. Cependant, des travaux de recherche supplementaires sont necessaires pour garantir la faisabilite du procede. Parmi les differents points a aborder, le controle du debit de circulation du solide entre les deux reacteurs est de la plus haute importance, notamment en ce qui concerne son impact sur l’apport en oxygene et le degre d’oxydation du solide. Aussi la reduction des fuites de gaz entre le reacteur fioul et le reacteur air est un autre point important a prendre en consideration. Dans cette etude, une nouvelle configuration de CLC est proposee ou les reactions sont effectuees dans deux lits fluidises bouillonnants interconnectes. Le controle du debit de circulation du solide est realise independamment du debit de gaz de fluidisation des reacteurs en utilisant des vannes pneumatiques non-mecaniques. Les siphons sont egalement employes pour reduire au mieux les fuites de gaz lors du transfert solide. Les resultats experimentaux obtenus dans une maquette froide equivalente a un pilote de 10 kWth sont presentes dans ce travail. L’impact des parametres operatoires sur le taux de circulation du solide, des fuites de gaz entre les deux lits et l’equilibre des pressions sur l’ensemble des elements du systeme est etudie. Une circulation stable du solide a ete obtenue grace a un controle maitrise du debit du solide et une etancheite efficace du systeme.

CLC is a new promising combustion process for CO2 capture with less or even no energy penalty compared to other processes. Up to now, most of the work performed on CLC was conducted with gaseous or solid fuels, using methane and coal and/or pet coke. Liquid fuels such as heavy fuels resulting from oil distillation or conversion may also be interesting feedstocks to consider. However, liquid fuels are challenging feedstock to deal with in fluidized beds. The objective of the present work is therefore to investigate the feasibility of liquid feed injection and contact with oxygen carrier in CLC conditions in order to conduct partial or complete combustion of hydrocarbons. A batch experimental fluidized bed set-up was developed to contact alternatively oxygen carrier with liquid fuels or air. The 20 mm i.d. fluidized bed reactor was filled up with 45 g of NiAl0.44O1.67 and pulses of 1-2 g of liquid were injected in the bed at high temperatures up to 950˚C. Different feedstocks have been injected, from dodecane to heavy fuel oils No.2. Results show that, during the reduction period, it is possible to convert all the fuel injected and there is no coke remaining on particles at the end of the reduction step. Depending upon oxygen available in the bed, either full combustion or partial combustion can be achieved. Similar results were found with different liquid feeds, despite their different composition and properties. Le CLC est un nouveau concept prometteur appliqué à la combustion qui permet le captage de CO en minimisant la pénalité énergétique liée au captage. Jusqu’à présent, l’essentiel des travaux de recherche dans le domaine du CLC concerne les charges gazeuses (méthane) et solides (charbon et coke). Les charges liquides, et particulièrement les résidus pétroliers, sont des charges également intéressantes à considérer a priori. La mise en oeuvre de ces charges en lit fluidisé est cependant délicate. L’objet de ce travail est d’étudier la faisabilité de la combustion partielle ou totale des charges liquides dans les conditions du CLC au contact d’un matériau porteur d’oxygène. Un petit réacteur en lit fluidisé opérant en batch a été développé pour permettre alternativement le contact du matériau porteur d’oxygène avec une charge liquide ou de l’air. Le réacteur de 20 mm de diamètre est rempli de 45 g de particules de NiAl0.44O1.67. Environ 1-2 g de charge liquide est injecté par pulse dans le lit à des températures allant jusqu’à 950˚C. Différentes charges liquides ont été étudiées, du dodécane au fioul lourd n˚2. Les résultats montrent que pendant la période de réduction du matériau porteur d’oxygène, il est possible de convertir tous les hydrocarbures injectés. À l’issue de cette phase, il ne subsiste pas de dépôt de coke à la surface des particules. En fonction de la quantité d’oxygène disponible dans le lit, on effectue une combustion totale ou partielle des hydrocarbures injectés. Des résultats similaires sont obtenus pour les différents hydrocarbures testés, malgré leurs propriétés a priori très différentes.

In fluidised bed processes, the solids are in vigorous motion and thus inevitably subjected to mechanical stresses due to inter-particle and particle-wall impacts. These stresses lead to a gradual degradation of the particles by surface wear, abrasion and body fragmentation commonly termed attrition. One significant contribution of attrition comes from the air jets of the fluidised bed distributor. Particles are entrained into the air jet, where they get accelerated and impacted onto the fluidised bed particles. The jet induced attrition only affects the part of the bed which is limited by the jet length, where the mode of attrition is largely collisional. The overall jet attrition rate is therefore the result of the combination of the single particle damage and the flux of particles entering into that region. The attrition behaviour of particles in the jet region is analysed by evaluating their propensity of breakage experimentally and by simulating an air-jet in a bed of particles by CFD-DEM. The frequency of collisions and impact velocities are estimated from which the attrition due to a single air-jet is predicted.

Abstract Background Seasonal malaria chemoprevention (SMC) is a World Health Organization-recommended intervention for the prevention of malaria among children at high risk in areas with seasonal transmission. During the coronavirus disease 2019 (COVID-19) pandemic, SMC drug distribution was rapidly adapted to reduce contact and mitigate the risk of transmission between communities and community distributors, with caregivers administering doses. To address the challenges and find local solutions to improve administration and adherence, the role model approach was designed, implemented and evaluated in selected communities of Burkina Faso, Chad and Togo. This paper describes the results of this evaluation. Methods Focus group discussions were held with primary caregivers in all three countries to understand their perceptions of the approach’s acceptability and feasibility. In Burkina Faso and Togo, household surveys assessed the characteristics of caregivers reached by role model activities. Key indicators on SMC coverage and adherence allowed for an assessment of caregiver engagement outcomes related to participation in activities. Statistical associations between participation in study’s activities and caregiver beliefs related to SMC had been tested. Results The majority of caregivers believed the approach to have a positive effect on drug administration, with most adopting the promoted strategies. Greater involvement of fathers in drug administration and acknowledgement of their joint responsibility was a notable positive outcome. However, several barriers to participation were noted and there was criticism of the group approach. In Burkina Faso and Togo, end-of-round survey results revealed that 98.4% of respondents agreed the approach improved their knowledge and skills in malaria prevention, while 100% expressed a desire to continue practicing the behaviours learned. However, there was a relatively low level of awareness of the approach among communities. Participation was strongly associated with participants’ self-reported belief in ease of remembering to administer, and ease of administering, SMC medicines. Conclusion Caregivers perceived the role model approach to be beneficial in aiding drug administration, with other positive impacts also reported. Replication and scale-up should utilize the most popular communication channels and existing community structures to ensure activities are promoted effectively. A mixture of group and one-on-one approaches should be used where appropriate and feasible.

Abstract Background Indoor residual spraying (IRS) is a cornerstone malaria control intervention in Burkina Faso. From 2018 to 2021, non-pyrethroid IRS was implemented annually in two regions of Burkina Faso with distinct malaria transmission patterns, concurrently with annual seasonal malaria chemoprevention (SMC), and a mass insecticide-treated net (ITN) distribution in 2019. Methods A retrospective quasi-experimental approach was used to evaluate the impact of the 2018, 2020, and 2021 IRS campaigns on routinely reported confirmed malaria case incidence at health facilities. The 2019 campaign was excluded due to lack of data reporting during a health sector strike. Controlled interrupted time series models were fit to detect changes in level and trend in malaria case incidence rates following each IRS campaign when compared to the baseline period 24-months before IRS. IRS districts Solenzo (Sudano-Sahelien climate), and Kampti (tropical climate) were compared with neighbouring control districts and the analyses were stratified by region. Modelled health facility catchment population estimates based on travel time to health facilities and weighted by non-malaria outpatient visits were used as an offset. The study period encompassed July 2016 through June 2022, excluding July 2018 to June 2019. Results District-level population and structure coverage achieved by IRS campaigns was greater than 85% in 2018, 2020, and 2021 in Solenzo and Kampti. In Solenzo a significant difference in malaria case incidence rates was detected after the 2018 campaign (IRR = 0.683; 95% CI 0.564–0.827) when compared to the control district. The effect was not detected following the 2020 or 2021 IRS campaigns. In Kampti, estimated malaria incidence rates were between 36 and 38% lower than in the control district following all three IRS campaigns compared to the baseline period. Conclusions Implementation of IRS in Kampti, a tropical region of Burkina Faso, appeared to have a consistent significant beneficial impact on malaria case rates. An initial positive impact in Solenzo after the first IRS campaign was not sustained in the successive evaluated IRS campaigns. This study points to a differential effect of IRS in different malaria transmission settings and in combination with ITN and SMC implementation.

Abstract Background Recommended since 2012 by the World Health Organization (WHO), seasonal malaria chemoprevention (SMC) is a community-based intervention to prevent malaria in children in African regions where malaria transmission follows a seasonal pattern. Following the publication of consolidated WHO guidelines for malaria, SMC is expected to reach more children in new geographies in future years. Though SMC has been shown to reduce malaria-related morbidity and mortality, there is potential for quality improvement of the intervention implementation. Assisted by ten quality standards from a framework developed by Malaria Consortium, this paper aims to better understand the quality of SMC implementation and identify potential barriers to quality delivery of SMC. Methods A qualitative thematic analysis on data collected after the annual SMC rounds implemented in Burkina Faso and Chad in 2019 was conducted. Sixteen focus group discussions conducted with caregivers and community distributors were analysed. Three selected quality standards for SMC delivery; planning and enumeration; community engagement; and administration of SMC medicines provided overarching quality themes under which subthemes were identified. Results Eight subthemes relating to the three quality standards were identified. Although SMC was well accepted by communities in both settings, common barriers to the quality delivery of SMC were identified including difficulty ensuring adherence to the SMC administration protocol; difficulties reaching mobile populations; concerns around adverse drug reactions; rumours, and concerns about SMC safety; and community distributors’ working conditions. Context-specific barriers included: the suboptimal timeliness of the SMC round in Burkina Faso, and the lack of involvement of female caregivers in mobilization activities in Chad. Conclusion In the context of increased adoption of SMC, this paper provides relevant insights and recommendations for the improved implementation of SMC programmes. These include the integration of strategies addressing communities’ concerns around adverse drug reactions, gender-specific mobilization strategies, and attention to community distributors’ working conditions. It also highlights the importance and utility of further, robust research on the quality of SMC delivery.