A Study on the RDF Manufacturing of Coffee grounds by using Pilot scale Oil-drying Equipment

Pilot scale 유중건조 장비를 이용한 커피찌꺼기의 고형연료화 연구

Abstract

We studied to find the optimal manufacturing conditions of coffee grounds sludge RDF with oil drying method. We expanded the lab scale to pilot scale to compare the efficiency of the oil-drying equipment and The selection of the ratio of coffee grounds and oil, the setting temperature, and the temperature change and water content with time were measured. In order to analyze the characteristics of the research results, characteristics of solid fuels produced(Coffee grounds of oil-dried) by calorimeter, TGA, combustion equipment, and combustion gas measuring instrument were analyzed. As a result, the ratio of oil to coffee grounds was 4: 1, and when the setting temperature was set to $300^{\circ}C$, the water content reached 10wt.% or less within 20 minutes. ln addition, it showed high calorific value of 6,273kcal/kg. However, coffee grounds had a similar composition to wood and showed high luminance and produced a lot of CO in combustion gas. As a result, it is considered to be unsuitable for thermoelectric power plant and camping fuel, but the initial ignition speed is high and the heat generation is high, so it is considered that it can replace the fuels for current use.

본 연구에서는 유중건조 공정으로 커피찌꺼기 고형연료를 제조하기 위한 최적 조건을 선정하는 연구를 수행하였다. 유중건조 장비를 실험실 규모에서 파일럿 규모로 확장하여 효율을 비교 분석하였으며, 최적 조건을 선정하기 위하여 커피찌꺼기와 기름의 비율 선정, 세팅 온도, 비율별 시간에 따른 온도변화 및 함수율을 측정하였다. 또한 연구결과물(커피찌꺼기 유중건조물)의 특성분석을 위하여 칼로리미터와 TGA, 연소 장비, 연소 가스 측정기를 이용하여 생산한 고형연료의 특성분석을 하였다. 그 결과 기름과 커피찌꺼기의 비율은 4:1이었고 세팅 온도 $300^{\circ}C$로 설정 시 20분 이내에 함수율 10wt.% 이하에 도달하였다. 또한 6,273kcal/kg의 높은 발열량을 보였으나 커피찌꺼기의 경우 목재와 비슷한 성분을 지니고 있어 높은 휘도를 보이며 연소 가스에서 많은 CO를 생성하였다. 이로 인하여 화력발전소, 캠핑용 연료로는 부적합하다고 판단되나 초기 착화속도가 빠르며 발열량이 높아 현재 사용 중인 불쏘시개용 연료를 대체할 수 있을 것으로 판단된다.

Fig. 1. Porous structure of coffee grounds by using quanta 3D microscope

Fig. 2. Drying equipment (a) Oil-drying(Pilot scale) (b) Hot-Air drying

Fig. 3. Sieve analysis test by particle size (a) 75㎛ (b) 106㎛ (c) 125㎛

Fig. 4. Lab scale pelletizer

Fig. 5. Fuel characteristics analysis equipment (a) IKA C1 Calorimeter (b)Combustion equipment (c) Testo 330-LL (d)TGA Q500 (e)Hot-air drying equipment

Fig. 6. Ash after combustion of fuel by water content (a) Moisture content 15wt.% (b) Moisture content 1wt.%

Fig. 7. Temperature calibration of pilot scale equipment

Fig. 8. Changes in oil-drying temperature and moisture content at drying time by oil to coffee ratio

Fig. 9. Changes in hot-air drying temperature and moisture content

Fig. 10. Oil-dried coffee grounds deoiling by sieve test (a) 75㎛ (b) 106㎛ (c) 125㎛

Fig. 11. Pelletized oil-dried coffee grounds (a) Moisture content 15wt.% (b) Moisture content 1wt.%

Fig. 12. Pelletized hot-air dried coffee grounds (a) Moisture content 15wt.% (b) Moisture content 1wt.%

Fig. 12. The amount of carbon monoxide and the temperature inside of combustion equipment

Table 1. Changes in drying temperature and moisture content at drying time by oil to coffee ratio

Table 2. Changes in drying temperature and moisture content at drying time by oil to coffee ratio

Table 3. Proximate analysis by drying method of coffee grounds

Table 4. Changes in drying temperature and moisture content at drying time by oil to coffee ratio

Table 5. Calorie & water content in varrious livestock manure sludges

Table 6. Proximate analysis by drying method of coffee grounds