Guilin Piao

Combustion test of refuse derived fuel in a fluidized bed

Abstract Power generation from refuse derived fuel (RDF) is one of the promising technologies for the utilization of municipal solid waste. To understand the combustion behavior of two kinds of RDF burnt in a fluidized bed incinerator, commercial sized RDF was fed continuously into a 0.3×0.3 m 2 and 2.73 m high bubbling type fluidized bed combustor. Gases such as CO, NO x , SO x and HCl concentrations in the flue gas from the combustor were detected by a continuous measurement system. It was found that, for RDF-A which is lower in density and strength than RDF-B, the concentrations of CO in flue gas are high and are strongly affected by the air ratio. When secondary air was injected, the CO concentrations for both RDF-A and RDF-B were decreased. The increase in the air ratio led to an increase of NO x concentration when only primary air was injected at a bed temperature of 1073 K. The addition of secondary air effectively reduced the NO x level for both RDF-A and RDF-B. The temperature where the HCl concentration was the lowest was about 1073 K. Nonetheless the concentrations of HCl were always less than 60 ppm in all experiments. The HCl removal ratio by the calcium compound was higher than 70% even though the bed temperature was higher than 1173K. This indicates that the added calcium compound in the RDFs effectively controlled the HCl emissions.

Combustion of refuse derived fuel in a fluidized bed

Power generation from Refuse Derived Fuel (RDF) is an attractive utilization technology of municipal solid waste. To explain the behavior of RDF-fired fluidized bed incinerator, the commercial size RDF was continuously burnt in a 30×30 cm bubbling type fluidized-bed combustor. It was found that 12 kg/h of RDF feed rate was too high feed for this test unit and the CO level was higher than 500 ppm. However, 10 kg/h of RDF was a proper feed rate and the CO level was kept under 150 ppm. Secondary air injection and changing air ratio from the pipe grid were effective for the complete combustion of RDE. It was also found that HCl concentration in flue gas was controlled by the calcium component contained in RDF and its level was decreased with decreasing the combustor temperature.

High temperature air-blown woody biomass gasification model for the estimation of an entrained down-flow gasifier

A high temperature air-blown gasification model for woody biomass is developed based on an air-blown gasification experiment. A high temperature air-blown gasification experiment on woody biomass in an entrained down-flow gasifier is carried out, and then the simple gasification model is developed based on the experimental results. In the experiment, air-blown gasification is conducted to demonstrate the behavior of this process. Pulverized wood is used as the gasification fuel, which is injected directly into the entrained down-flow gasifier by the pulverized wood banner. The pulverized wood is sieved through 60 mesh and supplied at rates of 19 and 27kg/h. The oxygen-carbon molar ratio (O/C) is employed as the operational condition instead of the air ratio. The maximum temperature achievable is over 1400K when the O/C is from 1.26 to 1.84. The results show that the gas composition is followed by the CO-shift reaction equilibrium. Therefore, the air-blown gasification model is developed based on the CO-shift reaction equilibrium. The simple gasification model agrees well with the experimental results. From calculations in large-scale units, the cold gas is able to achieve 80% efficiency in the air-blown gasification, when the woody biomass feedrate is over 1000kg/h and input air temperature is 700K.

Research and Development on Gasification Technology of Organic Waste Material (OWM) by using Entrained-flow

To understand the behavior of the entrained-flow gasification of organic wastes, high calorie value polypropylene (PP) and low calorie value polyethylene terephthalate (PET) were gasified in a single nozzle type Drop Tube Furnace (DTF). In a small scale of gasifier, it is very difficult to obtain as high temperature as 1, 300°C with a low oxygen-carbon molar ratio as being done in larger scale than pilot plants, and it is necessary to operate in high oxygen-carbon molar ratio in order to maintain the reaction temperature 1, 300°C because the heat loss becomes significant in comparison with heating load in the furnace. When methane gas was introduced as an auxiliary fuel under the low oxygen-carbon molar ratio, the reaction temperatures was achieved over 1, 300°C and higher carbon gasification conversion than 80% was attained. The composition of the main gas produced by gasification was correlated by the shift reaction equilibrium at the temperature above 1, 250°C. Then the equilibrium constant, which was almost independent of the temperature in the range, could be approximated about 0.85.

Gasification of organic waste materials (OWM) for power generation using fuel cell

A novel energy recycle system of organic waste materials is proposed. In this system, waste materials are converted into gaseous fuel by gasification, and subsequently applied to power generation systems using fuel cells. There are several technological problems that should be solved in order to realize the present system. In particular, an increase in the production of H/sub 2/ and CO gas from gasification and the development of a high efficiency removal system of contaminants in the gas are key factors for attaining high quality energy conversion and maintenance of the fuel cell operation in the long term. In order to understand the behavior of the entrained-flow gasification of organic waste, two types of fuel-coal and polypropylene (PP), were gasified in a 250 mm across and 3.4 m high drop tube furnace (DTF). The study has generated the following conclusions. (1) PP was perfectly analyzed at a temperature of 673 K, where significant weight losses take place. (2) For coal gasification, H/sub 2/ concentration is about 15%, CO concentration is about 25-30%, and CH/sub 4/ concentration is less than 5%. For PP gasification, an H/sub 2/ concentration decreases with an increase in oxygen-carbon molar ratio, and CO concentration is about 30-35%, more than coal gasification. (3) Carbon conversion increased with an increase in oxygen/carbon (O/C) molar ratio for coal and PP, and carbon conversion is about 70% for coal. For PP gasification, carbon conversion is 75%. (4) The cool gas efficiency decreased with increasing O/C for coal and PP. Moreover, for PP gasification, cool gas efficiency is 50% more than cool gas efficiency of coal at 40%.

Simulation modeling of fluidized bed coal gasifier for new topping cycle system

A new topping cycle coal power generation process is to be developed as a Japanese national project of high efficiency power generation process of coal. This process consists of a combination system of a pressurized bubbling fluidized-bed coal gasifier and a pressurized bubbling fluidized-bed combustor in series. To evaluate the performances and also to determine specifications and operation parameters of this process, it is extremely important to analyze the behavior and the performance of this system by a reasonable simulation model. A simulation model of this new process is developed in this paper. It is demonstrated by calculated results from this model that the carbon conversion in the gasifier, the composition and the heating value of produced gas are strongly dependent on operating conditions. Heat recovery by the steam in the combustor is also estimated as the function of coal feed rate.