Co-combustion Characteristics Research Articles

A comparison of co-combustion characteristics of coal with wood and hydrothermally treated municipal solid waste

In this work, thermogravimetric analysis was used to investigate the co-combustion characteristics of wood and municipal solid waste (MSW) with Indian coal. Combustion characteristics like volatile release, ignition were studied. Wood presented an enhanced reaction rate reflecting its high volatile and low ash contents, while MSW enhanced ignition behavior of Indian coal. The results indicate that blending of both, wood and MSW improves devolatization properties of coal. Significant interaction was detected between wood and Indian coal, and reactivity of coal has improved upon blending with wood. On the other hand, MSW shows a good interaction with Indian coal leading to significant reduction in ignition temperature of coal and this effect was more pronounced with higher blending ratio of MSW. Hence MSW blending could more positively support the combustion of low quality Indian coal as compared to wood, due to its property of enhancement of ignition characteristics.

Characteristics of co-combustion and kinetic study on hydrothermally treated municipal solid waste with different rank coals: A thermogravimetric analysis

This study presents an investigation on the influence of hydrothermally treated municipal solid waste (MSW) on the co-combustion characteristics with different rank coals, i.e. Indian, Indonesian and Australian coals. MSW blends of 10%, 20%, 30% and 50% (wt.%) with different rank coals were tested in a thermogravimetric analyser (TGA) in the temperature range from ambient to 700 °C under the heating rate of 10 °C/min. Combustion characteristics such as volatile release, ignition and burnout were studied for the blend fuel. Different ignition behavior was observed depending on the blends composition and the coal rank. The result of this work indicates that the blending of MSW improves devolatization properties of coal. But it was found that the co-combustion characteristics of MSW and coal blend cannot be predicted only from the pyrolytic and or devolatization phenomena as the other factors such as the coal quality also plays a vital role in deciding the blends co-combustion characteristics. The TGA combustion profiles showed that the combustion characteristics of blends followed those of parent fuels in both an additive and non-additive manners. These experimental results help to understand and predict the behavior of coal and MSW blends in practical applications.

The Deposition and Burning Characteristics During Slagging Co-Firing Coal and Wood: Modeling and Numerical Simulation

Numerical analysis was used to study the deposition and burning characteristics of combining co-combustion with slagging combustion technologies in this paper. The pyrolysis and burning kinetic models of different fuels were implanted into the WBSF-PCC2 (wall burning and slag flow in pulverized co-combustion) computation code, and then the slagging and co-combustion characteristics—especially the wall burning mechanism of different solid fuels and their effects on the whole burning behavior in the cylindrical combustor at different mixing ratios under the condition of keeping the heat input same—were simulated numerically. The results showed that adding wood powder at 25% mass fraction can increase the temperature at the initial stage of combustion, which is helpful to utilize the front space of the combustor. Adding wood powder at a 25% mass fraction can increase the reaction rate at the initial combustion stage; also, the coal ignitability is improved, and the burnout efficiency is enhanced by about 5% of suspension and deposition particles, which is helpful for coal particles to burn entirely and for combustion devices to minimize their dimensions or sizes. The results also showed that adding wood powder at a proper ratio is helpful to keep the combustion stability, not only because of the enhancement for the burning characteristics, but also because the running slag layer structure can be changed more continuously, which is very important for avoiding the abnormal slag accumulation in the slagging combustor. The theoretic analysis in this paper proves that unification of co-combustion and slagging combustion technologies is feasible, though more comprehensive and rigorous research is needed.

Combustion of agro-waste with coal in a fluidized bed

In this study, a review of the studies done on the co-combustion of some agro-waste in a bubbling fluidized bed combustor (BFBC) having an inside diameter of 102 mm and a height of 900 mm is given. The agro-waste used to investigate the co-combustion characteristics were peach and apricot stones produced as a waste from the fruit juice industry, and olive cake produced as a waste from the olive oil industry. These are typical wastes for a Mediterranean country. A lignite coal was used for co-combustion. On-line concentrations of O2, CO, CO2, SO2, NO x and total hydrocarbons (C m H n ) were measured in the flue gas during combustion experiments. Variations of emissions of various pollutants were studied by changing the operating parameters (excess air ratio, fluidization velocity and fuel feed rate). Temperature distribution along the bed was measured with thermocouples. Emissions were also monitored from the exhaust. Various combinations of coal and biomass mixtures were tested. During the combustion tests, it was observed that the volatile matter from the biomass quickly volatilizes and mostly burns in the freeboard. The temperature profiles along the bed and the freeboard also confirmed this phenomenon. It was found that as the volatile matter of the biomass increases, combustion takes place more in the freeboard region. Better combustion conditions occur at higher excess air ratios. The results showed that co-combustion with these three proposed biomasses lowers the SO2 and NO x emissions considerably. CO and hydrocarbon emissions are lower at the higher excess air ratios.

Interactions between oil shale and its semi-coke during co-combustion

In the present work, thermogravimetric analysis was employed to investigate the interactions between oil shale and its semi-coke during co-combustion process. During the test, the blends of semi-coke and oil shale were prepared at different blending ratios of 1:0, 4:1, 3:1, 2:1, 1:1, and 0:1. The results indicated some interactions were detected between oil shale and semi-coke during the tests. The rapid combustion of organic matter in oil shale, which led to the fuel particle temperature’s rapid increase and made semi-coke ignite in advance, improved the co-combustion characteristics in terms of ignition temperature ( T i ), the temperature reaching the maximum mass loss rate ( T max ), the maximum mass loss rate ( R ma x), the combustibility index ( C) and the specific reactivity of the co-combustion. With the increase in semi-coke mass fraction in the blends, the specific reactivity of the samples was found to decrease gradually due to lower volatile content and high carbon condensation structure in semi-coke. As the temperature increased, the specific reactivity of the samples first gradually increased, then decreased attributed to the oxidation of selectivity. The poor diffusion caused mainly by the ash shells made the decomposition of minerals more complicated. It was also analyzed that the ‘particle groups’ phenomenon that the dispersed particles are agglomerated by some forces in semi-coke ash went against the decomposition of minerals. Activation energies E from distributed activation energy (DAEM) slowly decreased at the initial stage, then increased sharply over a narrow conversion region, which indicted a difficult burnout stage. Meantime, a power law model was employed to investigate quantitatively the interactions. The experimental reaction orders could be predicted accurately from the calculated values. At the third stage, the kinetic parameters E 3 and A 3 were almost as much as the calculated values. At the low temperature region (470–540 °C), there was little difference between kinetic parameters E and A from the experiment data and the calculated data.

Co-combustion of peach and apricot stone with coal in a bubbling fluidized bed

In this study a bubbling fluidized bed combustor (BFBC) having an inside diameter of 102 mm and a height of 900 mm was used to investigate the co-combustion characteristics of peach and apricot stones produced as a waste from the fruit juice industry with coal. A lignite coal was used for co-combustion. On-line concentrations of O2, CO, CO2, SO2, NOX and total hydrocarbons (CmHn) were measured in the flue gas during combustion experiments. Variations of emissions of various pollutants were studied by changing the operating parameters (excess air ratio, fluidization velocity, and fuel feed rate). Temperature distribution along the bed was measured with thermocouples.For co-combustion of apricot and peach fruit stones with a lignite coal, various ratios of biomass to coal ranging from 0 to 100 wt.% were tested. For the peach stone co-combustion tests, efficiencies are about 98% and for the apricot stone co-combustion tests, efficiencies ranged between 94.7% and 96.9% for 25%, 50% and 75% of apricot stone in the fuel mixture.The results of this study have shown that as the biomass ratio in the fuel mixture increases, the combustion takes place at the upper regions of the main column. This causes higher temperatures in the freeboard than the bed. Also the CO and hydrocarbon (CmHn) emissions increase as the biomass percentage increases in the fuel mixture. This causes decrease in the combustion efficiency.These results suggest that peach and apricot stones are potential fuels that can be utilized for clean energy production in small-scale fruit juice industries by using BFBC. The percentage of peach stones or apricot stones in the fuel mixture is suggested to be below 50 wt.% in order to obtain the emission limits of EU. During the design of the BFBC, one has to be careful about the volatile matter (VM) content of the biomass. For the complete combustion of the VM, longer freeboard or secondary air addition should be considered.

Co-combustion of Korean anthracite with bituminous coal in two circulating fluidized bed combustors

The co-combustion characteristics for Korean anthracites and bituminous coals were determined in a lab-scale CFB reactor and the commercial scale Tonghae CFB Power Plant. In the lab-scale CFB combustion tests, the effluent rate of the emission gases, which can indicate the reactivity of the combustion, did not change appreciably when each coal burned. As the bituminous coal was added, however, the effluent rate of the emissions increased. The amount of the unburned carbon in ash decreased with increasing the ratio of the bituminous coal during the co-combustion. When the co-combustion was tested in the Tonghae CFB power plant, the temperatures at the upper part of the combustor and the cyclones, which were somewhat higher than designed and expected, could be reduced as the bituminous coal ratio increased. Consequently, more stable operation of the CFB boiler was achieved. The efficiency of the CFB boiler also increased due to increasing the reactivity of the combustion.

Thermogravimetric analysis of the co-combustion of the blends with high ash coal and waste tyres

Incineration methods are becoming increasingly important from the view point of the need to minimize the environmental impact of waste tyre disposal. Combustion of waste tyre, one high ash coal and tyre-coal blends with 10, 30 and 50% waste tyre were investigated by means of thermogravimetric analysis (TGA) carried out at 20 K min −1 in the temperature range from ambient temperature to 1273 K. And effects of the mixed proportion between coal and waste tyre on the combustion process, ignition and burnout characteristics were also studied. The results indicate that the combustion of waste tyre is controlled by the emission of volatile matter, the regions are more complex for waste tyre (three or more peaks) than for coal (one peak). Also as compared with the case of burning only high ash coal, the incorporation of waste tyre can improve the combustion characteristics of high ash coal, especially the ignition performance and the peak weight loss compared with the separate burning of waste tyre and coal. Moreover, comparisons of the TG–DTG profiles between experimental and calculational results, it is indicate that there is a comparatively important difference, the co-combustion characteristics is the coupling effect between waste tyre and coal. The data resulting also showed that the co-combustion of waste tyre and low quanlitied coal as fuel is feasible.

Characteristics of Co-combustion of Low-Rank Coal with Biomass

The fundamentals of ignition, NOx (NO and N2O) emissions, and ash formation characteristics for biomass and mixtures of coal with biomass are precisely elucidated in this study. In this study, biomass, coal, and a biomass−coal mixture are burned, using an electrically heated drop tube furnace. In the combustion test, the focus is on the ignition behavior, combustion efficiency, NOx emission behavior, and formation characteristics of particulate matter, based on the results of gas compositions along the furnace axis and a collection of particulate matter by a low-pressure impactor. As a result, the addition of biomass into low-rank coal affects combustion behavior, especially for ignition enhancement. The NO and N2O concentrations in co-combustion are almost the same as those in coal combustion, even if the quantity of input fuel nitrogen under the co-combustion condition is half of that under the coal combustion conditions. A kinetic simulation of the NO and N2O behavior results is conducted, using the homogeneous reaction schemes at constant temperature. The simulation result of NO concentration agrees with the experimental result obtained. However, the N2O concentration calculated is less than the experimental result, because the heterogeneous schemes that are related to N2O are not considered in this simulation. Fine particulates with a size of <2 μm during biomass combustion are produced. Burning the biomass with coal shifts the particle size distribution from fine particles to coarse particles, which can be captured by dust collection systems.

Emission Characteristics of Co-combustion of Sewage Sludge with Olive Cake and Lignite Coal in a Circulating Fluidized Bed

In this study, a circulating fluidized bed (CFB) of 125 mm diameter and 1800 mm height was used to find the combustion characteristics of sewage sludge (SS) produced in Turkey. Sludge + olive cake, and sludge + lignite coal mixtures were burned separately. Various sludge-to-lignite coal and sludge-to-olive cake ratios (5/95, 10/90, 15/85, 20/80) were tried. On-line concentrations of major components (O2, SO2, CO2, CO, NO x , C m H n ) were measured in the flue gas, as well as temperature and pressure distributions along the bed. Combustion efficiencies of sludge + olive cake and sludge + lignite coal mixtures were calculated, and the optimum conditions for operating parameters were discussed. The results have shown that the combustion mainly takes place in the upper regions of the main column where the temperature reaches 900°C. SS + Coal burn in the CFB with an efficiency of 95.14% to 96.18%, which is considered to be quite good. When burning sludge mixed with olive cake, appreciable amounts of CO and unburned hydrocarbons are formed and the combustion efficiency drops to 92.93%. CO and C m H n emissions are lower when lignite coal is mixed with various amounts of SS than the emissions when the coal is burned alone. As the %SS is increased in the fuel mixture, the SO2 emission decreases. NO x emissions are slightly higher. When burning sludge mixed with olive cake, SO2 and NO x emissions are slightly higher. CO and C m H n emissions decrease sharply when SS is mixed with 5%wt. olive cake. With increasing sludge ratio these emissions increase due to the unburned hydrocarbons. As a result of this study, it is believed that SS can be burned effectively in a CFBC together with other fuels, especially with olive cake (OC). OC will be a good additive fuel for the combustion of lower quality fuels.

04/02394 Fundamentals on co-combustion characteristics of low-grade coal with biomass: Naruse,I. et al. Preprints of Symposia — American Chemical Society, Division of Fuel Chemistry, 2003, 48, (1), 365–367

04/02394 Fundamentals on co-combustion characteristics of low-grade coal with biomass: Naruse,I. et al. Preprints of Symposia — American Chemical Society, Division of Fuel Chemistry, 2003, 48, (1), 365–367

The characteristics of coincineration of dewatered sludge, waste oil and waste solvent in commercial-scale fluidized bed incinerator

A commercial-scale Fluidized Bed Incinerator (FBI), which has a capacity of 60 tons per day to treat dewatered sludge and waste oil or solvent, was developed as one of the governmental R&D projects from 1990 to 1997. From the design, construction and operation of the plant, the characteristics of co-combustion and appropriate operating conditions with successful fly ash recirculation and with effluent controls have been investigated. Without adding any bed materials, sand, the co-incineration of sludge and spent-solvent can be achieved. The sludge combustion steps could be observed and confirmed, which consist of evaporation, agglomeration, devolatilization, combustion and attrition. The plant can also incinerate various types of sludge from wastewater treatment facilities with waste oil or solvent.

K-2233 石炭・バイオマスの混焼特性(S29-3 地域エネルギーシステムにおける小型発電技術の動向(3))(S29 地域エネルギーシステムにおける小型発電技術の動向)

K-2233 石炭・バイオマスの混焼特性(S29-3 地域エネルギーシステムにおける小型発電技術の動向(3))(S29 地域エネルギーシステムにおける小型発電技術の動向)

99/00663 An improved ablative pyrolysis reaction system

In this study a bubbling fluidized bed combustor (BFBC) having an inside diameter of 102 mm and a height of 900 mm was used to investigate the co-combustion characteristics of peach and apricot stones produced as a waste from the fruit juice industry with coal. A lignite coal was used for co-combustion. On-line concentrations of O2, CO, CO2, SO2, NOX and total hydrocarbons (CmHn) were measured in the flue gas during combustion experiments. Variations of emissions of various pollutants were studied by changing the operating parameters (excess air ratio, fluidization velocity, and fuel feed rate). Temperature distribution along the bed was measured with thermocouples.For co-combustion of apricot and peach fruit stones with a lignite coal, various ratios of biomass to coal ranging from 0 to 100 wt.% were tested. For the peach stone co-combustion tests, efficiencies are about 98% and for the apricot stone co-combustion tests, efficiencies ranged between 94.7% and 96.9% for 25%, 50% and 75% of apricot stone in the fuel mixture.The results of this study have shown that as the biomass ratio in the fuel mixture increases, the combustion takes place at the upper regions of the main column. This causes higher temperatures in the freeboard than the bed. Also the CO and hydrocarbon (CmHn) emissions increase as the biomass percentage increases in the fuel mixture. This causes decrease in the combustion efficiency.These results suggest that peach and apricot stones are potential fuels that can be utilized for clean energy production in small-scale fruit juice industries by using BFBC. The percentage of peach stones or apricot stones in the fuel mixture is suggested to be below 50 wt.% in order to obtain the emission limits of EU. During the design of the BFBC, one has to be careful about the volatile matter (VM) content of the biomass. For the complete combustion of the VM, longer freeboard or secondary air addition should be considered.

98/03742 Coal gasification in molten slag to manufacture reducing gas for smelting in blast furnaces

Experimental research on co-combustion characteristics of Huadian oil shale and its semi-coke was conducted on a bench of Circulating Fluidized Bed (CFB). The distribution of temperatures along furnace of the pilot was obtained. The factors that affect the temperature were analysis. The results showed that the blend fuel with 20% oil shale mixed with 80% semi-coke will suit for CFBC and the fluidized air ratio is less than 66.7%. The experiment also proved that bottom ash and fly ash could be utilized as build material for all conditions.