| At present,the biochar has been arisen the concern of domestic and foreign experts and scholars very well,biomass carbonization technology has become one of the most effective measures to solve the utilization of agricultural waste,biochar has been proven to have improved soil properties,enhanced soil fertilities,passivated heavy metals,sequestered carbon and mitigated greenhouse gases emissions,and other effects.However,there are large differences in the nature of biochar prepared under different pyrolysing conditions for a wide variety of agricultural wastes and different types of biomass feedstocks.Therefore,it is great significance to systematically study the physical and chemical properties of different biomass materials and their biochar to understand their agricultural and environmental applications.In this study,15 common agricultural wastes were selected:WS,RS,RH,CS,CC,RB,PS,RAS,SD,BB,CM,PMBC,BG,HR,SS,SSBP was used to decompose into biochar at a pyrolysing temperature of 450℃.Analyzing the physical and chemical properties of biomass and its biochar raw materials,and studing the effects of biomass on the properties of biochar;and the nutrient elements of biomass and biochar were analyzed to explain the transformation of nutrient elements in the process of carbonization;the potential application value of biochar in the environmental field was analyzed.Finally,the pyrolysis carbonization efficiency of large-scale high-capacity biochar continuous pyrolysis rotary kiln was discussed,and the characteristics of the product were analyzed and its practicability was evaluated.The main results are as follows:(1)By analyzing the basic physical and chemical properties of biochar prepared from different biomass,the highest pH value of RSBC was 10.16,while the pH of BGBC was the lowest,only 7.15.The ash and yield of SSBC were 80.59%and 60.55%,much higher than other types of biochar;the EC of CMBC and PMBChigher than other straw biochar;the contents of CEC in WSBC,RSBC and CSBC were 81.13%,77.00%and 79.13%,respectively,which were significant higher than other biochar;The content of hot water capacitive organic carbon in rice straw and corn stalk was 22.83g·kg-1,which was significantly higher than that of other biochar;the BET of BGBC is 29.03m2·g-1,which is more than 2 times of CMBC.On the elements of it,C element to the highest levels of BGBC is as high as 75.66%,and the SSBC of C element content is the lowest,only 13.47%.Thus,different biomass preparation physical and chemical properties of biochar is quite different.(2)Analyzing the nutrient and heavy metal contents of different raw materials and corresponding biochar.The results showed that,biomass after pyrolysing,the content of nutrients in the biochar was increased,the total nitrogen content of maize straw was increased from the concentration of 6.80(g·kg-1)to 13.93(g·kg-1)in the raw material,The total potassium content of biomass was also increased after low temperature cracking,among which WS,RS and RB were the most obvious growth trend,respectively,from 8.49(g·kg-1),10.54(g·kg-1),8.43(g·kg-1)increased to 20.9(g·kg-1),23.24(g·kg-1),20.5(g·kg-1);from the aspects of nutrient recovery,the recovery rate of N was the lowest,only 44.58%,the highest recovery rate of BG was 92.77%,the recovery rate of K in biomass carbon was the highest,averaging more than 60%;full quantity heavy metal content increased while biomass was after pyrolysing,but the effective state of heavy metal content is significantly reduced,HRBC effective state of Zn,Cu,Mn was reduced by 81.60%,82.4%and 86.5%respectively,the best effect,which showed that the biochar had heavy metals passivation effect.(3)Solid,liquid and gas in the process of biomass pyrolysis had a great relationship with the biomass.Corn was after pyrolysing accounted for only 33.4%,while the wood vinegar and gas content accounted for 27.5%and 39.1%.In China,the four crop straws of corn straw,wheat straw,rice straw,rice husk,can produce 16.3 million tons of biochar each year,which contains 82.8 million tons of carbon,which is equivalent to the annual emissions of 0.3Pg to avoid CO2.Biochar can be used as a stable carbon pool,has a good carbon storage capacity,which can reduce greenhouse gas emissions,increase the terrestrial ecosystem of carbon sequestration capacity.(4)The large capacity study of continuous turning kiln of biomass,the equipment can handle 1.3 tons of biomass pellets per hour,production of 490 kg dry biochar per hour,the production of biochar products to meet the requirements of pyrolysing,and the pyrolysing gas calorific value up to 2600 kcal,it can meet the normal operation of equipment,this set of equipment can be run continuously,energy independence,high carbon production,meet the demand of agricultural production. |
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