| In order to provide reference for selecting noncombustible herbs in constructing fire prevention and disaster avoidance landscape garden in Hohhot,the combustibility of 16garden herbs in Hohhot was studied during the autumn fireproof period.Take each herbs’stems and leaves as materials,based on thermogravimetric analysis,raise to 600℃from room temperature at the oxygen flow rate 30m L/min and the heating rate 40℃/min to get TG and DTG curves,use the Coats-Redfern model to calculate the first-order reaction kinetics activation energy（E）,frequency factor（A）,pyrolysis characteristic index（P）,blaze index（Di）of rapid pyrolysis stage,combine the ash content,crude fat content,calorific value and ignition point all those 4 physicochemical properties together,evaluate the combustibility of 16 garden herbs synthetically by factor analysis.The results show that:1.The pyrolysis process of 16 garden herbs under air atmosphere can be divided into dehydration stage,pyrolysis stage and carbonization stage,the temperature range of rapid pyrolysis stage is 253.75～334.92℃,and the weight loss of both leaves and stems of Coleus blumei are 52.71%and 56.18%,which makes it the least quality consumption sample after burning out,and the maximal pyrolysis rate of both leaves and stems of Petunia hybrida are 4.514%·min-1and 9.317%·min-1,which makes it the fastest pyrolytic sample,and the combustibility of Petunia hybrida is mainly affected by leaves;2.The pyrolysis temperature and activation energy of 16 garden herbs’leaves are lower than stems,but the crude fat content and calorific value of leaves are obviously higher than stems.The ash content of leaves is similar to stems,15.84%and 13.03%;Due to the low lignin content of herbs,the TG and DTG curves of carbonization stage have no obvious weight loss steps and peaks;3.The combustibility sequence of 16 garden herbs is:Petunia hybrida>Hemerocallis flava>Hemerocallis×hybrida>Iris lactea var.chinensis>Catharanthus roseus>Hosta ventricosa>Sedum spectabile>Paeonia lactiflora>Salvia officinalis>Coleus blumei>Iris pseudocorus>Ipomoea purpurea>Gaillardia aristata>Sedum kamtschaticum>Zinnia linearis>Celosia cristat.The results show that based on optimization of the combustibility of noncombustible herbs during the autumn fireproof period in Hohhot are Celosia cristata.Zinnia linearis,Sedum kamtschaticum,Gaillardia aristata,Ipomoea purpurea;The pyrolysis kinetic parameters are better than the physical and chemical properties in describing the comprehensive combustibility of herbs;Among the pyrolysis kinetic parameters which were conducted by thermogravimetric analysis,the activation energy and the frequency factor should be mainly referenced in describing the pyrolysis characteristic;Crude fat content has a less effect than other variables on combustibility of herbs in the autumn fireproof period.Cauline leaf herbs’leaves are generally more flammable than stems. |
