Study on the Incineration Characteristics Using Agricultural Wastes in Bubbling Fluidized Bed Incinerator
Date Issued
2007
Date
2007
Author(s)
Wang, Feng-Jehng
DOI
zh-TW
Abstract
This study was based on the analysis results of the physical and chemical characteristics of the agricultural wastes: For example the used plastic sheets from agricultural production and sick-and-dead pigs (L.Y.D.3 male pig), etc., as well as the combustion and mass-energy balances theories of the agricultural wastes, together with the main parameters of the incinerator design and operation, etc. In order to design and manufacture a middle Laboratory-scale Bubbling Fluidized Bed Incinerator (BFBI). Moreover, through the fluidized theory, numerical simulation analysis and experimental measurements etc., to determine the relationship between the fluidized gas flow velocity and pressure drop within the fluidized bed incinerator. In order to prove and confirm the fluidized characteristics of the bed sand (silica sand) of the BFBI developed by oneself. Finally, the incinerations of the agricultural wastes were being tested. The sample analysis from the emission pollutants and ash discharged through incinerating, in order to set up the optimum operation and control system of this incinerator.
This research based on the analysis of the physical and chemical characteristics of agricultural wastes. The standard methods of American Society for Testing Materials (ASTM ) were being used for proximate analysis, higher heating value（HHV）and ultimate analysis. The experimental results indicated that for the entire L.Y.D.3 male pig, the average lower heating value (LHV) and the average rate for the moisture content were 5763.65kcal/kg and 65.86%wb, respectively; carbon content was 55.27%, and oxygen content was 23.53% on average. These showed that L.Y.D.3 male pig's body had high heat and moisture contents, as well as high carbon and oxygen content organic fuel. Moreover, the agriculture discarded plastic films, such as PP, PE, PVC and PS, etc., contained up to more than 95% carbons and hydrogen combustible compositions, as well as the LHV all reached 10000 kcal/kg, had extremely higher chemical heat compound, together with the moisture content and ash were all extremely low (under 1% on average). According to the analysis result of the physical and chemical characteristics of the agricultural wastes can be concluded that the method of incinerating to deal with these agricultural wastes was considered as the optimal and feasible method.
The research also based on the L.Y.D.3 male pig's chemical compositions weight percentage and actual measurement value of HHV, through the regression analysis by SAS software, can develop the correlation models accurately in order to determine the HHV of pigs (their correlation coefficients all reached to R2 =0.65), as well as to build up a set of standard research approach formulae for the prediction of the HHV of bio-fuel.
This research through the methods of fluidized theory, the numerical simulation analysis, and the experimental measurement to prove that relationship between the fluidized characteristics and pressure drops of the BFBI. To determine that change flows within the incinerator, as well as to set up a saving time and effective method for bubbling fluidized bed incinerator numerical simulation. This study used the computational fluid dynamics (CFD) to determine relationship between the superficial velocity and pressure drop in BFBI. According to results of the numerical simulation showed that the linear equation had a significant relationship between the superficial velocity and pressure drop. When the superficial velocity of bed is 0.188m/s, the pressure drop equaled to 4562.499Pa was close to the result of the experimental calculating value (4573.33Pa) extremely. So this research adopted the superficial velocity 0.188m/s to be regarded as the minimum fluidization velocity when incinerated experiments. This research utilized 3 kinds of different assumption formulae with drag coefficient and Reynolds numbers to obtain the terminal velocity of bed particle was 3.684m/s. And then, confirmed that the superficial velocity must be limited between minimum fluidization velocity and terminal velocity in the BFBI.
This research utilized the BFBI to incinerate the agriculture discarded plastic film of PP. Under the regular feed rate and oxygen support, combustion temperature from 500 to 1000℃, the sampled emission gas and the analysis results showed that: the emission trend of SO2 slightly decreased progressively with the increase of temperature; the emission trend of NO was increased progressively as the increase of temperature; the emission trend of CO decreasing progressively as the increase of temperature; the emission trend of CO2 increasing progressively as the rising of temperature; the emission trend of PM10 decreasing progressively as the rising of temperature, respectively. The results showed based on the result of the incineration experiments of agriculture discard plastic film of PP, there was an increasing progressively trend with the increase of the temperature to incineration efficiency, and the incineration efficiency at the above of 700℃ (include) of bed temperature was up to 94% (include) above, showed that the incineration efficiency of the BFBI is extremely well.
This research utilized the BFBI to incinerate the agriculture discards plastic films, such as PE, PP and PVC, etc. The analysis results of the emission gas sample showed that incineration under difference temperatures 500, 600 , 700 , 800 , 900 and 1000℃, etc., the total emission of 16 kinds of PAHs was less or there was no PAHs emission at 700℃. Ashes composition was sampled and analyzed after incinerating; the results indicated that combustible carbon and hydrogen which included in fly ash and bottom ash were lowest with incinerating temperature at 700℃. Therefore, the results proved that 700℃ was the optimal operation temperature for the BFBI.
Subjects
流體化
氣泡式流體化床
焚化爐
數值模擬
fluidized
bubbling fluidized bed
incinerator
agricultural waste
numerical
Type
thesis
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