Research On UASB Adopting Molasses As Substrate To Produce High Purity Hydrogen At Low PH

Energy plays an essential role in the economic development in each and every country at present. Environmental problems such as the earth’s climate warming, ozone layer destruction and acid rain and others are highlighted. The emission of greenhouse gases mainly comes from the burning of fossil fuels. Therefore, it is crucial to search for renewable alternative energy sources or methods of reducing energy consumption. In April 2009, European Union adopted the "Plan on Climate Action and Renewable Energy Package", whose goal is to improve energy efficiency by 20%, increase the proportion of renewable energy in total energy consumption to 20% and reduce the total EU greenhouse gas emissions by 20% by 2020 compared with that of 1900. In December 2009, Chinese government put forward in the Copenhagen Climate Change Conference that we should strengthen energy-saving and improve the working efficiency in ways that our carbon dioxide emissions per unit of GDP will drop 40% to 45% by 2020 compared with that of 2005. We should vigorously develop renewable energy and nuclear power, that is how we can make proportion of non fossil energy accounting for disposable energy consumption reach more or less 15% by 2020.We should energetically increase forest carbon sinks, by doing so, we will increase the forest coverage by 40 million hectares in 2020 more than that of 2005 and increase the forest stock volume by 13 billion cubic meters compared with that of 2005. We will vigorously develop green economy and actively develop a low carbon economy and circular economy, meanwhile, conduct researches and development and promote climate friendly technologies.In order to accomplish these challenges, all countries should adhere to the principles of developing green economy, including the supply of renewable energy replacing the supply of fossil fuel based energy in ways to balance the relationship between economic and social development and environmental protection. In the global scope, the scholars all over the world have attached great importance to the issues such as the rapid consumption of fuel resources, consumption augment of fossil fuel, uncertainty of future availability of fossil fuels and increasing global energy demands and pollutant emissions and climate change. And they have begun to study to use different sources of energy to replace the traditional fossil fuels, such as natural gas, bio fuels and hydrogen. Hydrogen can be generated in a variety of ways, such as biological method of producing hydrogen by dark fermentation, which processes a lot of advantages including high growth rate of bacteria, less energy, consuming zero oxygen and lights, being in low cost. We could use a variety of carbon sources as the substrate. Many types of waste can be converted into sacchariferous organic wastewater in ways that they can be used as a biological substrate. In most of industrial waste water, there is a carbon source which is easy to be degraded. Sucrose and glucose and other sugars under appropriate temperature can have a high hydrogen conversion efficiency. That is the reason why sacchariferous organic wastewater adopted as raw materials in biological production is more efficient than other materials. This shows that sacchariferous organic wastewater is the most useful way for industrial hydrogen production.This research sudied the hydrogen production performance at low pH by adopting the up-flow anaerobic sludge blanket (UASB) made of organic glass, using molasses wastewater as fermentation substrate and adding appropriate amount of ammonium chloride and potassium dihydrogen phosphate. In the initial startup of this system, sodium bicarbonate was added to control the water pH=6.75-7.15 which enabled the system to be in a neutral anaerobic fermentation with the fixed influent COD of 4000 mg-L-1 and HRT=8 h. Twenty days after the operation of this system, it was in a mixed-type fermentation, then stop adding sodium bicarbonate. Forty-five days after its operation, the concentration of ethanol and acetic acid accounted for 79.39% of the total, while the propionic acid concentration only accounted for 10.89% of the total concentration, which formed the stable typical ethanol-type fermentation. On the sixty-fifth day of its operation, the concentration of ethanol and acetic acid was 840.56 mg-L-1 and 403.12 mg-L-1 respectively which accounted for 93.2% of the total concentration with hydrogen content of 86.97%. When the effluent pH=2.81, the hydrogen production performance was the best with the hydrogen production rate of 2.079 mmol·L-l·h-1, hydrogen production of 1.12 m3/m3·d and biogas hydrogen content of 91.46%, which was 1.65 times of the biogas hydrogen content in the stable phase.