Study On Pyrolysis Recycling Process Of Typical Space Human-induced Solid Waste

The"three steps"of Chinese manned space program is in the process of building a manned space station for a long time.A multi-person,long-duration manned space mission would generate a lot of human waste,this part of waste might occupy the scarce volume resources and increase the useless load,at the same time,at the same time,bring microbe stir up problem,causing corrosion of the spacecraft and releasing harmful gases,affecting the health of astronauts.At present,the method of transporting wastes back to the earth by cargo spacecraft is not suitable for deep space solid waste treatment due to its large resource consumption and high cost.which puts forward a strong demand for in-situ treatment of space solid wastes.The goal of space solid waste treatment is to reduce the volume,make the waste harmless and recycle the waste.Solid waste pyrolysis is a technology with great potential application prospect.The characteristics of spatial solid waste determine the way of waste disposal.According to the characteristics of the solid waste generated in manned spaceflight,the first step for China to deal with the challenge of the solid waste caused by human beings in space is to establish a hybrid solid waste model.In this paper,the generation rhythm of solid waste in China's manned spaceflight was investigated in detail,and a typical space solid waste model was established based on the ground simulation of the generation rhythm of solid waste in manned spaceflight and foreign solid waste models.In this model,the human excreted waste and clothing waste were account for the largest proportion,which were 48.9%and 23.4%respectively.The proportion of C,H,O and N elements in the typical mixed solid waste model after drying was42.45%,30.24%,11.49%and 15.73%.It is the basis of capacity reduction treatment and effect evaluation to study the composition and pyrolysis characteristics of solid waste in space.In this paper,thermogravimetric characteristics and dynamics of nine typical spatial human-induced solid waste and their mixed solid waste models were studied by thermal analysis.It was found that the maximum decomposition rate of typical solid waste was concentrated at 300??400?,and the final decomposition temperature was concentrated at 600??700?.The simulated urine had the highest solid residue rate?24.5%?,while the other single component solid waste thermolysis residue rate was basically less than 21%.The reaction series of nine typical solid waste thermolysis reactions could be well described by 0 or 1.The maximum activation energy required for PE in solid waste was 285.92 k J/mol,The lowest simulated feces was 93.3 k J/mol.During the pyrolysis of the mixed solid waste model,the initial decomposition temperature of the mixed solid waste was reduced to 180?,and the pyrolysis final temperature was extended to 850?,and the solid waste residual rate was reduced to only 15.5%.The pyrolysis process showed 5 distinct weightless temperature ranges,but it was not a simple superposition of the single component solid waste pyrolysis process.The weighted total activation energy E'of the pyrolysis of the mixture was122.7 k J/mol,lower than the linear superposition value of the activation energy of the single component solid waste pyrolysis.Aiming at the difficult problems of space solid waste capacity reduction and resource recovery,In this paper,the effects of pyrolysis temperature,heating rate and inorganic salt additives on the composition and distribution of gas,liquid and solid,key resources of pyrolysis products in the solid waste model,and the recycling of solid waste residues were studied,to establish and optimize the optimum process conditions for reducing the volume of solid waste in space and selectively generating CH₄,the mechanism of the process of solid waste thermal solution was preliminarily discussed in combination with the analysis method of thermogravimetric mass spectrometry.According to the distribution law of pyrolysis three-phase products of solid waste model,in the temperature range of 300??900?,the pyrolysis coke yield of typical solid waste model was decreased gradually with the temperature increasing,with the lowest being 20.3%.The pyrolysis gas yield was decreased first with the temperature and then increased,and reached the maximum value of 72.6%at 900?,while the pyrolysis tar was increased first and then decreased with the temperature.In the heating rate range of 5?/min?40?/min,the heating rate had no significant influence on the yield of pyrolysis three-phase products of typical solid waste model.The yield of pyrolytic carbon was decreased slowly,but remained basically between18.8%?25.1%,while the yield of pyrolysis gas was increased slowly,and remained basically within the range of 56.3%?63.6%.According to the distribution law of resource-based gases,as the pyrolysis temperature increased,the gas production rates of CH₄,CO,C₂H₂and C₂H₄generally were shown an increasing trend,while the CO₂gas first was decreased and then increased.The proportion of these 5 major resource gases in the total gas was reached the maximum at 800?.With the increase of the heating rate,the variation law of the gas production rate of the five major resources was basically the same,decreasing first and then increasing.When the heating rate was 5?/min and the pyrolysis temperature was 800?,the yield of CH₄,the pyrolysis product of the solid waste model,was reached the maximum?5.5%?.According to the recycling law of solid waste pyrolytic carbon,the pyrolysis temperature was 800?,and the specific surface area was 117.155 m²/g,which was mainly composed of macropores and mesopores.In addition to organic carbon,pyrolytic charcoal also contained a certain amount of inorganic nutrient mineral elements such as N,P and K.,At the pyrolysis final temperature of 800?,the contents were 59.630 mg/g,0.335mg/g and 32.184 mg/g,respectively.Therefore,it could be considered to improve the fertility of plant cultivation soil in the space controlled ecological biological protection system.According to the influence law of inorganic salt,the introduction of inorganic salt K₂SO₄reduced the initial decomposition temperature of mixed solid waste by 100?,and the pyrolysis activation energy significantly was decreased,only to 143.04 k J/mol.In the pyrolysis gas products,CO was increased by 11%and CO₂was increased by 3.55%,while CH₄did not change significantly,only increasing by0.1%,while C₂H₄was significantly decreased by 8%.In addition,the TG-MS method was used in this paper to conduct a preliminary study on the mechanism of gas production during solid waste model pyrolysis.The experiment found that CO₂,CH₄,CO,C₂H₄and C₂H₂and other five typical gases were precipitated at three temperature points of 350?,420?and 780?,which was consistent with the law of weight loss of solid waste model.A typical mixing model of space solid waste was established and the pyrolysis characteristics of the mixing model and the recycling process were studied in this paper.The research results of this paper could be directly applied to the treatment of space solid waste in China.