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Characteristics of spent coffee ground as a fuel and combustion test in a small boiler (6.5 kW)
Kang, Sae Byul,Oh, Hong Young,Kim, Jong Jin,Choi, Kyu Sung Elsevier 2017 Renewable energy Vol.113 No.-
<P><B>Abstract</B></P> <P>Spent Coffee Ground is a residue of coffee drink mainly used at a coffee shop. Spent coffee ground is used as an odor removal, manure in flowerpot and so on. However most of spent coffee ground is discarded as garbage. In this study, we investigated characteristics of spent coffee ground as a fuel and combustion characteristics in a small boiler system (6.5 kW based on input lower heating value), such as CO, NO<SUB>x</SUB>, O<SUB>2</SUB> and heating characteristic of heating boiler. Drying of spent coffee ground in the open air condition takes less than 6 days in case of height of 11 mm. More than 96% of spend coffee ground is between 100 and 500 μm in particle size. Lower heating value of spent coffee ground used as fuel is about 18.8 MJ/kg (4500 kcal/kg at water content 10%). Combustion chamber of the boiler is a crucible type with primary and secondary air supply and heat exchanger is one through type. Spent coffee ground consumption as a fuel of the boiler is about 1.17 kg/hr. O<SUB>2</SUB> concentration of the flue gas of the boiler is about 17.8% which is higher than a commercial domestic gas boiler or a domestic wood pellet boiler. CO and NO<SUB>x</SUB> concentration are 643 and 163 ppm respectively.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Large amount of spent coffee ground has been treated as waste. </LI> <LI> Spent coffee ground as a fuel with enough heating value was compared to the other renewable solid biomass. </LI> <LI> Natural drying of wet spent coffee ground about takes less than 3 days in the open air. </LI> <LI> Higher Nitrogen content in spent coffee ground cause higher NOx emission in combustion than wood pellet. </LI> <LI> Precise design of combustor for dried spent coffee ground should be needed for boiler efficiency and emission performance. </LI> </UL> </P>
Development of an air fuel control system for a domestic wood pellet boiler
Sae Byul Kang,김종진,최규성,Bong Suk Sim,Hong Young Oh 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.6
Wood pellets are a kind of solid biomass energy and a renewable energy source. Made by compressing sawdust, wood pellets have a higher energy density than split firewood and wood chips. In 2007, the new and renewable energy (NRE) portion was 2.4% with respect to total primary energy in Korea. The Korean government wants to increase the new and renewable energy (NRE) portion up to 6.1% by 2020 [1]. To achieve this target, the government has been establishing some policies, such as incentive policy, NRE mandatory use for public building and renewable portfolio standard (RPS) and so on. To supply wood pellets as fuel for the combustion chamber of a wood pellet boiler, most domestic wood pellet boilers put a constant volume by using an auger type fuel feed system. In an auger system as fuel feeding, there is the possibility of changing energy input due to the different density of wood pellets even in a constant volume flow rate of wood pellets. If fuel input rate is changed without any correction of air flow rate for combustion, the condition of combustion in a wood pellet boiler can be deteriorated. We have developed an air-fuel control system for a domestic wood pellet boiler by using flue gas oxygen concentration measurement and a PID controller. To measure O2 concentration of flue gas, a wide band O2 sensor was adopted. We changed fuel input from 100% to 50% by artificial manipulation to confirm the control system. The O2 concentration in flue gas can be controlled to be 8.5% ± 1% without significant change of CO and NOx concentration.
An Effective Calculation Method for Radiative Exchange in an Enclosure with Specular Surfaces
Kang, Sae Byul,Lee, Woo Il,Lee, Joon Sik Taylor Francis 2006 NUMERICAL HEAT TRANSFER PART A-APPLICATIONS - Vol.50 No.9
<P>A new calculation method is proposed to determine the radiative heat transfer in enclosures composed of specularly reflecting surfaces. This method is based on the concept of the transition reflection in the context of the ray-tracing method, by which only two reflections of ray tracing are necessary to consider in the evaluation of net radiative transfer rate. This method can also be used not only for diffuse and specular surfaces but also for directional surfaces such as non-Lambert surface. Because the radiative exchange rate can be obtained by considering only two reflections of ray tracing, the matrix inversion is not required, and thus computational time can be reduced substantially. In order to validate the present method, the radiative exchange between two parallel plates is calculated, and the results are compared with those of previous methods including analytic solutions and stochastic methods. The parameters tested are the wall emissivity and the ratio of the distance between two plates to the length of plates. For all cases considered, the present results are in excellent agreement with exact solutions within 0.5% error, and show better accuracy than other methods. The new calculation method is also tested for nondiffusely emitting and reflecting surfaces of platinum and glass.</P>