Study On Hydrothermal Conversion Of Livestock Carcasses

The annual productions of livestock and poultry whose annual mortality rates caused by the infectious diseases are about 12% to 20% are more than 0.1 billion tons.Therefore,the annual qualities of livestock carcasses are more than ten millions tons.But the existing disposal technologies(landfill,burning,incineration,rendering,composting,anaerobic digestion,alkaline hydrolysis etc)can cause certain harm to the environment and the residents' health.So a new disposal technology needs to be explored.The hydrothermal treatment technology will be able to kill the pathogens and this technology doesn't request the moisture content of raw material.Water as solvent in the technology is friendly to environment.So this article by selecting pigs,chickens and ducks as typical raw materials studied the hydrothermal parameters' influences including reaction temperature,residence time,solid-liquid ratio and catalyst for the physical and chemical performance of products and pyrolysis characteristics of solid products and this article studied the way on the enrichment of target products by controlling hydrothermal parameters,which provided the foundation for the harmless and high value utilization.Firstly,in order to explore the mechanism of the hydrothermal conversion of livestock carcasses,this article by selecting pigs,chickens and ducks as typical raw materials studied reaction temperature' influences for the physical and chemical performance of products.The study found that during the hydrothermal process,the conversion from lipids to esters was dominant below 150?;During 150-190?,the conversion from esters to carboxylic acids or the conversion from carboxylic acids to alkanes was dominant;During 150-190?,the conversion from protein to nitrogen compounds occupied the leading role.The high relative content of long-chain alkanes and carboxylic acids which can be degraded into alkanes in the liquid products was in favour of the application in the field of aviation biofuels.Therefore,the best reaction temperature of hydrothermal conversion for livestock carcasses was within 150-190?.Secondly,this article studied the influences of residence time and solid-liquid ratio for the physical and chemical performance of products and discussed the optimal conditions for the control and enrichment of the target products.The study found that the relative contents of carboxylic acids decreased continuously and the relative contents of alkanes increased continuously in liquid products when the residence time was increased from 10 mins to 70 mins or the solid-liquid ratio was reduced from 1:5 to 1:10.It was indicated that the conversion from carboxylic acids to alkanes was dominant.So,in order to enrich more alkanes,the optium residence time was within 50-70 min and the optium solid-liquid ratio was 1:5-1:10.Then,the thermogravimetric analysis and PY-GCMS analysis were used to study the pyrolysis characteristics of the hydrothermal solid products.The study found that the solid products of the livestock carcasses by hydrothermal conversion could be used for the next pyrolysis.Finally,the article studied the influence of different concentration of sulfuric acid,potassium carbonate and potassium hydroxide as catalysts on physical and chemical performance of products,which could provide the theoretical foundation for the control and enrichment of target products.The study found that the three catalysts could promote the conversion from esters to carboxylic acids and inhibit the conversion from carboxylic acids to alkanes,which made the retaive contents of target products(carboxylic acids with sixteen carbons or eighteen carbons)increasing from 42.85% whith no catalyst to 75%.And in the same concentration,the sequence of the target products' relative content for three catalysts was: potassium carbonate > potassium oxide > sulfuric acid.And the best target products' relative content was 87.82% when the potassium carbonate was 0.005mol/l.