環境不友善農業廢棄物造粒可行性與基本性質探討

Abstract

本次研究以地瓜（Ipomoea batatas）藤蔓、番茄（Solanum lycopersicum）莖葉殘體、油茶（Camellia oleifera）殼作為原料，柳杉（Cryptomeria japonica）木粉為混合配料進行造粒，藉由比較造粒前、後在熱能、燃燒性質上表現的差異進行評估，以解決國內此類無法堆肥，且對環境具有危害性的環境不友善農業廢棄物之處置問題。 地瓜藤蔓、番茄莖葉殘體為草本生質物，灰分較高、熱值較低。而油茶殼與柳杉木粉則為木本生質物，灰分較低，熱值較高。實驗中，除了單獨使用地瓜藤蔓、番茄莖葉殘體、油茶殼造粒（P10、T10、O10），也分別與柳杉木粉以80：20、60：40、40：60、20：80比例混合、調高含水率至30%後造粒，並測量所有顆粒的含水率、熱值、灰分、顆粒堅牢度等基本性質。 從結果可發現，來自油料木本植物的油茶殼，不但具有與柳杉木粉接近的熱值（4,438 cal/g），也有極低的灰分（0.451%），但單獨造粒時，因材料本身真密度高（1.4 g/cm3），投入造粒機時較不易被擠壓成型，絕大多數以粉末直接掉出，經過提高材料初始含水率至30%後，方可順利造粒，且有達到PFI顆粒燃料標準中Premium等級之實力。而為統一比較基準，也將其它單獨造粒與混料配方的材料初始含水率調高至與前者相等，卻同時提高了卡料的發生次數與機會，降低了顆粒成品的顆粒堅牢度、熱值等性質。 草本生質物的地瓜藤蔓、番茄莖葉殘體，雖然單獨造粒後的表現，相比原始材料差異不大，但隨著混入的柳杉木粉比例愈高，各項性質也隨之上升，藉由計算、比對其在不同比例的熱值與灰分之迴歸線後，得出如果本次實驗顆粒如果要達到2018年PFI顆粒燃料標準中Utility級或Standard級，番茄莖葉殘體需搭配至少75%、92%的柳杉木粉，地瓜藤蔓則需搭配至少65%、91%的柳杉木粉。 本次研究可確定這3種環境不友善農業廢棄物的造粒可行性，唯未來仍需要注意材料初始含水率的調整，避免造粒過程中卡料、塞模等現象發生的機會，方可進一步提升產出顆粒的熱值與PDI，增加其應用價植。

In this study, potato (Ipomoea batatas) vines, tomato (Solanum lycopersicum) residual stems and leaves, and shells of camellia’s (Camellia oleifera) seeds were used as raw materials; Japanese Cedar’s (Cryptomeria japonica) wood powder was used as a mixed ingredient for pelletizing. Through evaluating the differences in thermal energy and combustion properties before and after, we want to solve the problem of the environmental unfriendly agricultural waste disposal that is not compostable and harmful to the environment. Potato vines and tomato residual stems and leaves are herbaceous biomass with higher ash content and lower calorific value. Shells of camellia’s seeds and Japanese Cedar’s wood powder are woody biomass with lower ash content and higher calorific value. In this experiment, we not only separately used potato vines, tomato residual stems and leaves, and shells of camellia’s seeds to pelletize (P10, T10, O10), but also mixed them with Japanese Cedar’s wood powder with the ratio: 80:20, 60:40, 40:60, and 20:80 to pelletize with moisture adjustment up to 30%. After pelletizing, we measure the basic properties of pellets such as moisture content, calorific value, ash content and pellet durability index. According to the results, it can be found that shells of camellia’s seeds, which are from oily woody plants, not only have the calorific value that is close to Japanese Cedar’s (4,438 cal/g), but also have very low ash content (0.451%). However, when they pelletize alone, due to their true density are high (1.4 g/cm3), they are not easy to be extruded when throwing into the mill, and most of them are directly dropped out in powder form. After the initial moisture content of them is increased to 30%, they can be successfully pelletize and reach the premium grade in PFI pellet fuel standard. Yet, on the other hand, in order to unify the comparative benchmarks, the initial moisture content of other materials with pelletizing whether in separate or in mixed formula are also increased to 30%. At the same time, the times of occurrence and opportunities of stuck are increased, and the durability and calorific value of the pellets are reduced. After pelletizing, although the performance of potato vines and tomato residual stems and leaves, which both are the herb biomass, are still similar to their original materials, the higher proportion of Japanese Cedar’s wood powder they mixed with, the better the various properties of them display. After calculating and comparing the regression lines of calorific value and ash content in different proportions, we can conclude that if the experimental pellets want to reach the “utility” or “standard” grade in 2018 PFI pellet fuel standard, tomato residual stems and leaves must be blended with at least 75% or 92% of Japanese Cedar’s wood powder; potato vines need to be blended with at least 65% or 91% of Japanese Cedar’s wood powder. After this research, we can confirm the pelletizing feasibility of these 3 kinds of environmental unfriendly agricultural wastes. However, in the future, it is still necessary for us to notice the adjustment of the initial moisture content of the material, so that the risks of stuck or plug will decrease, and the pellets will be able to enhance their properties and utilization value further.