Catalytic Charring And Smoke Suppression Attenuated Of The Flame Retardant Wood In Fire

The surface carbonization layer formed by fire-retardant wood in fire environment could play a key role in preventing flame spread and protecting wood.The research on the catalytic charcoal reaction and the flame retardant and smoke suppression mechanism of wood in fire is very important for the development of high efficiency flame retardant system and the reduction of fire loss.Thesis mainly guided by the guidance of modern catalytic reaction theory to research the principle of catalyzed char formation and smoke capture of wood,when which flame retardant by ammonium polyphosphate(APP)and porous materials,such as 5A zeolite,char sulfonic acid.Use CONE,TGA,Py-GC-MS,SEM and FTIR et al to study the rules of char formation and smoke release under different flame retardant systems,to explore the dynamic relationship between the composition and structure of pore materials and smoke release of wood,to study the catalytic conversion mechanism of fire smoke.The conclusions obtained are as follows:Investigated the effect of flame retardant wood using different degree of polymerization ammonium polyphosphate(APP),it was found that the low polymerization degree APP 100 was mainly weightless before 250℃ and matched with the burning point of wood(230-290℃).Thus its degradation products could inhibit the thermal decomposition of wood exactly right,and catalyze the wood to form closely stick carbon that can provide effective isolation.The initial decomposition temperature of high polymerization degree APP 163 and APP201s is higher than 300℃,and the effect of inhibiting the heat release is lower than APP 100.But they can form stronger carbon with a large number of unbroken bubbles had resistant to high temperature and not broken.This carbon can reduce the particles to produce dust,so could make smoke release less than the APP100.Therefore the different polymerization degree of ammonium polyphosphate is closely related to its initial degradation temperature,the maximum weight loss rate and the corresponding temperature,which affects its thermal decomposition process,its degradation products and its catalytic charring to the wood.Blend different polymerization degree APP to flame retardant wood would have a better effect on reducing the heat and smoke release.The metal-organic frameworks[Co5(OH)2(tca)2(ina)2(H2O)2]·4H2O(Co5)is a porous metal,formed by metal cobalt ions,isonicotinic acid(Hina)and 1,2,3-Propanic acid(H3tca).The flame retardant effect of Co5 with APP on poplar was better than that of APP alone.Compared with s-APP,total heat release(THR)reduced by 18.3%,carbon residue increased by 7.9%of s-APP/Cos with 1.7%Co5.The results of Py-GC-MS showed that nitrogen heterocyclic and carbohydrates increased,nevertheless CO2 and phenol compounds decreased in degradation products of s-APP/Co5.It indicated that the degradation of poplar powder to nitrogen containing hybrid compounds and carbohydrates was not further degraded to small molecular fat oxide and phenols,which is because APP/Co5 effectively inhibited the degradation of poplar wood.These showed Co5 has better gas phase flame retardation or to promote gas phase flame retardation in the process of APP flame-retardant poplar.When 5A zeolite flame retardant poplar particleboard in coordination with APP,the porous structure of 5A zeolite and excellent carbon forming ability make the production of smoke and CO from APP/5A fire-retardant poplar particleboard decreased significantly.Although THR can be reduced,the effect of 5A zeolite on heat release is not prominent,because the peak heat release rate(PHRR)of s-APP/5A increased slightly.The flame retardant contribution of 5A zeolite to poplar particleboard is mainly to promote carbon formation and lead to the formation of stable and high temperature resistant Ca-Al-Si-phosphocarbonaceous charcoal structure.5A zeolite modified by isonicotinic acid can catalyze early decomposition of APP,which promoted earlier and faster charcoal.That maked s-APP/5AA have lower PHRR,THR,SPR and YCO,formed dense and coherent Ca-Al-Si-phosphocarbonaceous charcoal without surface cracks better than s-APP/5A.The particles in different silica gel systems were deposited in wood cell cavity and cell gap,did not change the porous structure and the appearance characteristics of Paulownia.Single silica gel did not reduce the heat release of the PW-Gel samples,but it can slow down the degradation rate of the samples and reduce the total amount of smoke,especially the YCO.The APP/silica gel can effectively inhibit the heat release of the samples and reduce the flue gas during the flame combustion,but increase the total amount of smoke in the whole experiment process,which is the shortcoming of APP need to overcome.Cu,Mn sulfate doped APP/silica gel could make PHRR,THR of PW-Mn/APP/Gel,PW-Cu/APP/Gel decreased more significantly than the PW-APP/Gel’s,their THR were only 7.90 MJ/m2 and 5.02 MJ/m2,which was 57.8%and 73.2%lower than that of PW-APP/Gel respectively.And nd SPR,TSP,YCO of them are also significantly lower than PW-APP/Gel’s.In combination with the thermogravimetric analysis and the residual morphology,the PW-Mn/APP/Gel and PW-Cu/APP/Gel formed the Cu(Mn)-Si-phosphocarbonaceous charcoal,which was a solid and continuous whole charcoal,and the stability of resistant 600-800℃ high temperature were better than that of the other samples.Synthetically,the stability order of charcoal from different flame retardant systems in descending is Cu(Mn)-Si-phosphocarbonaceous,Si-phosphocarbonaceous,Si-carbonaceous and pure carbonaceous.The solid char sulfonic acid(SCA),which is prepared from wood residues by sulfuric acid catalytic carbonization and followed sulfonation,has an acidity of 2.12 mmol.g-1.CSA flame-retardant poplar particleboard reduced PHRR 39.4%and time-to-PHRR delayed 145s,THR decreased by 20.4%,and the amount of carbon residue increased by 10%.The effect of CSA to restrain smoke was more significant,its SPR and TSP were only 1/5 of pure poplar particleboard,and the release of toxic gas CO was 51.9%less than that of pure poplar particleboard.The results of Py-GC-MS show that SCA could catalyze the degradation of poplar particleboard before 280℃,and promote the formation of charcoal containing more oxygen heterocycles and carbohydrates than other samples.The energy spectrum analysis shows that the residual charcoal of sb-CSA had maximum C/O weight and atomic percentage,0.89wt%S.These indicate that there is a larger proportion of carbon in the residue,and the successful construction of the sulfonic group on the carbon skeleton and the effect of the catalytic carbon formation of the particleboard.Pure poplar charcoal(CS)catalyzed by sulphuric acid would prolong the flame burning time,could not reduce the total heat release of the sb-CS samples.But CS could inhibit the release of smoke and CO.This may be that the adsorption of porous charcoal structure can effectively reduce the emission of smoke.The reasons that CSA is better than CS to inhibit degradation of particleboard and reduce its heat release,one might be that sulfonic groups can promote hydroxyl compounds in wood dehydrate to esters and then charcoal,and the other is CSA could be heated to produce SO2,CO2 and H2O.CSA can not only effectively reduce the heat release,but also efficiently inhibit the release of smoke and CO,which indicates it is an environmentally friendly flame retardant.The preparation process of CSA is simple,and it is a new way to develop and utilize wood residues.