EXPERIMENTAL DETERMINATION OF THERMAL CHARACTERISTICS OF MUNICIPAL SOLID WASTE

Transcription

1 EXPERIMENTAL DETERMINATION OF THERMAL CHARACTERISTICS OF MUNICIPAL SOLID WASTE Vyacheslav Bukhmrov 1, *, Olga Kolbaba 1, and Raml Gabtov 1 1 Ivanovo State Power Engneerng Unversty, Ivanovo, Russa Abstract. The artcle s devoted to the expermental study of effectve thermal characterstcs of muncpal sold waste (MSW) wet layer n the dryng process. The research s based on the zone method. Seres of laboratory experments was performed. The dryng knetcs and temperature curves were obtaned on the base of whch the knetc coeffcents were determned. We constructed a graph of the knetc coeffcents of the materal mosture. The research results can be used for determnaton the temperature and mosture content felds n the MSW layer durng ts processng. 1 Introducton In world practce an overwhelmng amount of muncpal sold waste (MSW) are taken to landflls. Increased cost of MSW bural and delverng them to the grave stes, a permanent envronmental hazards connected wth the dsposal of large volumes of waste, as well as the dffculty of selecton and arrangement of new landflls are stmulatng the ndustral waste processng as a way takes nto account the most requrements of the economy, ecology and resources. Industral processng provdes an ntegrated approach to addressng dsposal, recyclng and dsposal of waste. It makes t possble to save land resources, to produce of waste new products (heat and electrcty), to solve envronmental problems. The gradual transton from landfll to ndustral processng s the man trend of the soluton of sold waste problem n the world. MSW s a heterogeneous mxture of complex morphologcal structure, ncludng: food and vegetable waste, paper and textle components, plastc, leather, rubber, wood, ferrous and nonferrous metals, glass, stones, bones. When consderng the entre complex of problems assocated wth the collecton, transportaton, dsposal and recyclng of sold waste n the frst place the queston of the composton and the propertes of ths materal. If for decson the problem on the collecton and transportaton of MSW the nformaton on ther mosture content and densty s suffcent, then for the choce of dsposal and utlzaton method and technology t s necessary to obtan complete nformaton about the morphology and elemental * Correspondng author: buhmrov@tot.spu.ru The Authors, publshed by EDP Scences. Ths s an open access artcle dstrbuted under the terms of the Creatve Commons Attrbuton Lcense 4.0 (

2 composton, ncludng thermal propertes of MSW. The morphologcal structure of MSW s gven n Table 1. [1] Table 1. Morphologcal composton of MSW n dfferent clmatc zones, % by weght. Component Clmatc zone medum south north Food waste Paper Wood Black scrap metal Nonferrous scrap metal Textle Bones Glass Leather, rubber Stone, stucco Plastc Other Screenngs (less than 15 mm) In world practce for the MSW recyclng and dsposal are usng thermal, chemcal, bologcal and physco-chemcal methods. The content n the MSW to 60-70% organc (combustble) facton prefers ther processng energy effcent thermal methods, where the energy for processng tself can be removed from MSW whle producng the new fuel and on the bass of electrcty and heat. 2 Statement of the Problem Thermal processng of sold waste s most often carred out n shaft furnaces (thermal reactors) n whch MSW layer sequentally through dryng processes and pyrolyss wth subsequent gasfcaton of sold carbonaceous resdue. Gaseous fuel formed n the processng s removed to the consumer for use n thermal technologcal process. Sold waste can be attrbuted to partculate materal, whch n the presence of mosture nternal requre hgh energy consumpton for the dryng process. In order to select a ratonal regme of the reactor t s necessary to determne the temperature feld of sold waste layer, dryng tme raw materal and energy costs n the process. Knowledge of these parameters s possble to calculate the speed of chargng, the heght of the dryng zone of the thermal reactor and, therefore, to desgn t properly. Determnaton of MSW layer temperature felds as a mult-porous body, makes t necessary to determne the dependence of ts effectve heat-physcal propertes on the mosture content and temperature. Currently, there are many dfferent methods and technques for determnaton of the effectve thermal characterstcs of the porous bodes [2,3]. As for the sold waste, n lterature there are only scattered data obtaned based on expermental studes of thermal propertes of some ndvdual MSW components [4,5,6]. The purpus of ths research s an expermental study of thermal propertes of the MSW layer. 3 Experment and processng 2

3 As shown n Table 1, the base components of MSW wth the greatest percent n the morphologcal structure are: food waste, paper (cardboard) and textle, whch n the form of mosture due to the materal related to the capllary-porous collodal bodes. To dentfy the physcal pcture of the heat and mass transfer n collodal capllary-porous bodes you need to know the dependence of the thermal coeffcents on the physcal - chemcal propertes and mosture content, whch s the man factor that determnes the thermal propertes of most bodes. In general, heat and mass transfer process s characterzed by varablty of physcal parameters: temperature and mosture content. In order to determne the materal temperature and mosture content dependences of the transfer coeffcents we put a seres of experments. In ths connecton, we used a zonal method whch ensures the accuracy of determnng the physcal characterstcs values, acceptable n techncal calculatons. Fgure 1 shows the expermental setup. The expermental procedure was as follows. The test materal (MSW layer sample) was placed n two thn-walled copper cylnder wth a dameter of 16 mm and a length of 110 mm. One cylnder s suspended for weghng devce, the other s used for fxng the materal temperature change usng thermocouples connected to the nverter MBA8. Then cylnders were placed n an nsulated ppe, purged wth a hot heatng medum at a speed of 8 m / s, excludng the external dffuson resstance to vapor transport from the open ends of the sample nto the envronment. Temperature change over tme of the materal along the length of the sample and the mass loss are fxed. Thus, the dryng knetcs curves and the temperature curves were obtaned, from whch the effectve thermal conductvty coeffcent was calculated. Fg. 1. Schematc of the expermental setup. 1. Ar heater; 2. Insulated ppe; 3. Electronc balance; 4. Unt MBA-8; 5. PC; 6. Thermo-couples TCA (c); 7. Samples. In accordance wth the zonal method, the nterval of mosture concentraton varaton n the sold phase US UE and the temperature TS TEwas dvded nto n zones, each of whch assumes a constant thermal conductvty coeffcent. To determne the effectve thermal conductvty the zonal method was supplemented by removng the temperature curve. Each temperature curve was dvded nto n zones correspondng to of knetcs curve zones. For each of the zones T S and T E were measured and the thermal balance was made: mccct mm сw T mcur q (1) 3

4 Then, consderng that the quantty of heat requred to heat up the mass of materal, mass of mosture contaned n t and evaporate the mosture s suppled by heat conducton through the sde surface of the sample, we determned the effectve thermal conductvty of most materal n the dryng process by the formula: q (2) F( TH TM ) In the equatons (1), (2) s ndcated: mc - mass of dry substance n the sample, kg; c c - heat capacty of dry substance, J/(kg K); T TE T - temperature change of the materal S over tme, C; m M - the mass of mosture n a sample to the tme, kg; c W - water heat capacty, J/(kg K); radus of the sample, m; F - the lateral surface of the sample, m 2 ; TH TM the temperature dfference between the heatng medum and the average temperature of the materal n the -th tme nterval, C. Effectve thermal dffusvty was determned by the well-known formula: a (3) c Specfc heat of most body lnearly dependent on the mosture content, was determned on the prncple of addtve: с cc(1 U) cw U (3) The densty of the materal to be dred was determned by the expresson: c(1 U) W U (4) where n -, the densty of water and dry materal respectvely. W c 4 Results and Dscusson The expermental results are presented graphcally n fg Fg. 2. Varaton of the effectve thermal conductvty of МSW durng process at temperatures of the dryng agent (1 132 С, С, С, С, С). 4

5 Fg. 3. Varaton of the effectve thermal dffusvty of МSW durng process at temperatures of the dryng agent (1 132 С, С, С, С, С). 5 Concluson As a result of the experments dryng knetcs curves and temperature curves were obtaned. On the base of the curves effectve thermal conductvty and thermal dffusvty of MSW were calculated. The results of ths research can be used to calculate the temperature feld and mosture concentratons n the MSW layer durng ts processng n the thermal reactor. Acknowledgments The work wthn the framework of the state contract No Development of research method and process of manufacture of gaseous fuel and energy based on thermal processng of organc raw materals. References 1. Thermal utlzaton of sold household waste (SRI concept Stromkompozt, Krasnoyarsk, 2006) 2. L.L. Vaslev, S.A. Tanaeva, Thermal propertes of porous materals (Scence and technology, Mnsk, 1971) 3. G.N. Dulnev, Y.P. Zarchnyak, The thermal conductvty of mxtures and composte materals (Energy, Lenngrad, 1974) [n Russan] 4. A.S. Gnzburg, M.A. Gromov, T.I. Krasovskaa, Thermophyscal characterstcs of food products (Moskow, Food Industry, 1980) [n Russan] 5. S.A. Ilyn, V.M. Fokn, ASTU Messenger 2 (2006) 6. A.V. Mtrofanov, J. Vestnk ISPU 2 (2015) 5