Atributos do reator anaeróbio contínuo de tubos múltiplos no controle da carga orgânica volumétrica específica na fase acidogênica visando à produção de hidrogênio

Abstract

The continuous multiple tube reactor (CMTR) is a configuration proposed to produce hydrogen to contribute to energy sustainability. This technology has been shown to be promising due to its ability to guarantee the maintenance of the specific organic loading rate (SOLR), through the continuous disposal of biomass. In this context, the objective of this study was to evaluate the performance of the CMTR in the control of SOLR and in the production of hydrogen in a continuous and stable form. For this, the inner surface of tubes was adapted with grooves in the shape of an endless screw to improve the aspects related to the biomass balance of the reactor. The CMTR was operated under mesophilic temperature conditions (25°C), inoculated by a natural fermentation process and fed with synthetic wastewater based on sucrose as the carbon source. The influence of the organic loading rate (OLR) was evaluated by varying the COD in 2000, 4000, 6000, 8000, 12000 and 16000 mg COD L -1 and using a hydraulic retention time (HTR) of 2 and 4 hours. From these variations, four OLR conditions were obtained: 24 (E1 and E5), 48 (E2 and E6), 72 (E3 and E7) and 96 (E4 and E8) g COD L-1d -1 . The results revealed that the hydrogen production remained continuous for long periods of operation (~ 90 days) in all tests, although with signs of instability. The structural effect of adapting grooves to the inner surface of the tubes was effective in fixing the biomass, while being efficient in preventing its excessive accumulation in the medium, which contributed to the natural dragging needs of the system. In this way, the biomass balance was favorable in maintaining SOLR values appropriate for continuous hydrogen production. The results showed that the tests operated with lower load values (E1, E2, E5 and E6) were superior considering the parameters: sucrose conversion efficiency, molar hydrogen flow rate, volumetric hydrogen production rate and hydrogen yield. The percentages of hydrogen in the biogas from these tests remained above 63%. The tests with higher OLR values (E3, E4, E7 and E8) had a loss of performance in terms of hydrogen production due to possible inhibition of biomass by the substrate (overload conditions). The main metabolites produced in the tests were acetic, lactic, butyric acids and ethanol and the best performance was achieved in the E2 test (1593.6 mL H2 L -1 h - 1 ; 0.5 mol H2 mol-1sac; 1.80 mmol H2 h -1 ). The CMTR proved to be promising for the continuous production of hydrogen and dispensed with the use of additional biomass disposal strategies.