Bottom Of Boiler Research Articles

Design and performance of a cyclone separator integrated with a bottom ash bed for the removal of fine particulate matter in a palm oil mill: A simulation study

<abstract> <p>Long-term exposure to pollution from particulate matter in palm oil mills can result in chronic respiratory diseases, cardiovascular diseases and mortality. Particulate matter with a size of less than 2.5 μm (PM2.5) has a greater impact than one with a size of 10 μm. The current PM cleaning equipment in palm oil mills consists of cyclones that are incapable of optimally filtering PM2.5. For this reason, it is necessary to design cyclone applications for fine particle separation in palm oil mills. Normal cyclones are incapable of segregating particles smaller than 2.5 μm. This study's objective was to design a cyclone with a filter on the vortex detector. These cyclones are utilized in PM2.5 fine particle filtration systems. Using computational fluid dynamics, cyclone performance is analyzed in terms of removal efficiency and pressure decrease. The research was conducted utilizing the Reynolds tress model with varying inlet velocities of 10, 15, 20, 25 and 30 meters per second. The filter is composed of boiler bottom ash refuse from palm oil mills; 0.310 meters is the height of the filter bed inserted in the vortex finder. The obtained results demonstrated that the PM2.5 removal efficiency reached 98%, while the pressure decrease was only 93 Pa greater than that of conventional cyclones. Thereby, cyclone designs with bottom ash filters can be used to filter fine particulate matter, particularly particles smaller than 2.5 μm.</p> </abstract>

Characteristics of Porous Asphalt Mixture by Using a Bottom Ash Boiler as a Filler

Porous asphalt is asphalt mixture using open gradation dominated by coarse aggregate to produce a large enough cavity. Bottom ash waste produced by a boiler used in the extraction process of palm oil into crude palm oil. Shells and pulps that has been burned at high temperature between 500°C to 700°C will later become of boiler bottom ash. The aim of this study was to inspect the performance of Porous Asphalt Mixture characteristics which combining bottom ash boiler and cement as filler using Retona Blend 55 as a binder. The specimen preparation were designed by the Australian Asphalt Pavement Association (AAPA) method by parameter of Cantabro Loss (CL), Asphalt Flow Down (AFD), Voids In Mix (VIM), Stability and Marshall Quotient (MQ). The Optimum Asphalt Contain (OAC) obtain was used to prepare specimens within OAC with variation 50 % bottom ash boiler and 50 % cement as filler. The result of study showed that the OAC obtained 6%. Almost all parameter values were meet to the required specification of AAPA (2004). The value of CL is 9.25 %, AFD value is 0.19%, Stability 573.27 kg, flow 4.7 mm and VIM 12.29%. The value of VIM not meet to required specification (18%-25%).

Increasing the safety operation of railway tanks in emergency situations by improving the design of boiler bottom protective elements

This article presents an analysis of the problem of reliability of tank boilers in an emergency event. The designs of the boiler bottom protection and the prevention of wagon crawls on top of each other in collisions are evaluated. An analysis of the requirements for the tank protective elements is performed. A technical solution to improve the protective shield of the bottom is developed. The proposed solution will increase rigidity and strength of the protective shield structure, reduce the risk of damage to the railway tank boiler bottom when the protruding elements of the adjacent wagon collide. The work presents the results of the stressstrain state of the proposed design protective shield in the case of rail car collision and, accordingly, the force impact of 150 kN according to the RID TE25 standard.

Mineral Sequestration of Carbon Dioxide in Circulating Fluidized Bed Combustion Boiler Bottom Ash

This paper investigates the mineral sequestration of carbon dioxide in circulating fluidized bed combustion (CFBC) boiler bottom ash. CFBC bottom ash, which originated from two sources, was prepared along with pulverized coal-fired (PC) boiler bottom ash as a control. These ashes were exposed to accelerated carbonation conditions at a relative humidity of 40% and 100%, in order to investigate the effects of humidity on the carbonation kinetics of the bottom ash. The obtained results showed that not only lime but other calcium-bearing phases (gehlenite, wollastonite, and brownmillerite) in CFBC bottom ash participated in the mineral carbonation reaction. In particular, these phases underwent hydration in a wet carbonation environment, whereby the carbon dioxide uptake and capacity of CFBC bottom ash are significantly enhanced. This study may have important implications, demonstrating the feasibility of carbon dioxide sequestration and recycling of CFBC boiler bottom ash.

Oxidation, reemission and mass distribution of mercury in bituminous coal-fired power plants with SCR, CS-ESP and wet FGD

Mercury (Hg) speciation variations in flue gas at the inlet and outlet of various air pollution control devices (APCDs) were studied, including a selective catalytic reactor (SCR), a cold side-electrostatic precipitator (CS-ESP), a wet flue gas desulfurization system (wet FGD) and the stack of bituminous coal-fired power plants. Effects of flue gas temperature, flow rate and selected flue gas components on Hg oxidation were also studied. The association of selected parameters on Hg0 oxidation and removal by the APCDs and the mass distribution of Hg within the system were estimated. Sampling and analysis were carried out using the Ontario Hydro Method. Solid and liquid samples were analyzed according to US EPA methods 7470A and 7471A, respectively. Hg concentration in the flue gas at the outlet boiler and stack ranged from 4.70 to 27.3μg/Sm3 and 3.1 to 0.48μg/Sm3, respectively. The overall Hg removal efficiency in the APCDs ranged from 43.8% to 94.9%, and oxidized Hg in flue gas decreased with increasing temperature. With an increase in HCl concentration, a decrease in flue gas flow rate and decreasing temperature, oxidation of elemental Hg in combustion flue gas increased. The effects of SOx and NOx concentrations on elemental Hg oxidation in flue gas were rather complex. Among the parameters studied, the most significant parameters affecting overall Hg removal in the APCDs, in order, were removal in the ESP, oxidation in the SCR system and removal in the wet FGD. Experimental data and statistical analysis confirmed the promotion of a co-beneficial control of Hg in the SCR, CS-ESP and wet FGD configurations. The mass distribution showed that 43.0% of Hg was collected in ESP fly ash, 49.4% in wet FGD by-products and effluents, 3.9% of Hg was removed in boiler bottom ash and 3.7% was released into the atmosphere. In the SCR+CS-ESP+wet FGD configuration, a major portion of Hg was distributed into the by-products and removed by the APCDs compared to the lower removal levels seen in the CS-ESP+wet FGD configuration.

Development of a novel fluidized bed ash cooler for circulating fluidized bed boilers: Experimental study and application

A novel bottom ash cooler (BAC) called compound fluidized bed ash cooler (CFBAC) was developed in this paper. The CFBAC combined the major technical features of spouted bed and bubbling bed, and could achieve the selective discharge on the bottom ash. Experiments about the gas–solid flow characteristics of the CFBAC were conducted in a visible cold test rig. The experimental results indicated that the separation chamber working in the spouted bed state had a good particle separation effect on the boiler bottom ash. A small quantity of fluidizing air was needed for the cooling chambers to work in the bubbling bed state. The particle separation effect could be controlled by the fluidizing air flow and physical dimensions such as the height of separation partition. The CFBAC had also been industrially applied in a 300 MW circulating fluidized bed unit. The application showed that the CFBAC had a well separation effect, an excellent adaptability on the bottom ash, a good cooling effect and a large ash discharge capacity over 30 t/h. Compared with the water-cooled BAC, the CFBAC had a better energy conservation performance.

Drag coefficient of Solid Recovered Fuels (SRF)

The numerical simulation of Solid Recovered Fuels (SRF) co-combustion in pulverised coal power plants requires a flexible particle model, which among other properties should be able to predict the aerodynamic behaviour of the irregular-shaped particles, especially their trajectories along the boiler axis. This will help to provide vital information on whether the SRF particles are entrained in the combustion gases or drop to the boiler bottom. One difficulty encountered in the process is the true value of the drag coefficient ( C D) of the coarse SRF particles. Most of the numerical simulation codes calculate the particle trajectories by integrating the force balance of the particles in which the C D plays an important role. As a result, a true C D of SRF will definitely lead to more realistic results. In this short communication, the authors have taken a practical approach in determining the C D of the SRF. It was found that within the Newton’s law range the C D of the SRF lies between 0.6 and 2.0 with a mean value of 1.5. The results were further validated by correlating the calculated lift velocities of SRF using different C D values and that obtained through experiment.

Influence of CFB (circulating fluidized bed) boiler bottom ash heat recovery mode on thermal economy of units

CFB (circulating fluidized bed) boiler bottom ash contains large amounts of physical heat. A BAC (bottom ash cooler) is often used to treat high temperature bottom ash to reclaim heat, and to have the ash easily transported. The unit thermal economic indicators of three CFB power plants in China were derived based on heat balance calculation and analysis on the principled thermal system in turbine heat acceptance condition, taking the influence of two different bottom ash heat recovery modes into account. One of the two bottom ash heat recovery modes was the FBAC (fluidized bed ash cooler) mode, and the other was the RAC (rolling-cylinder ash cooler) mode. The results indicated that two modes both improved the thermal economy of units. Compared with the RAC mode, the FBAC mode obtained higher plant thermal efficiency, lower plant heat rate and less standard coal consumption. The standard coal consumption rate of the FBAC mode was less nearly 2 g/(kW h) than the RAC mode in the three CFB power plants, when the net calorific power of standard coal was 29.27 MJ/kg.

Fluoride exposure in the endemic fluorosis area of Guizhou, China

The dental and skeletal fluorosis is highly prevalent in Zhijin, Guizhou, especially at Hualuo Village, Hehua Village and Majiazhuang Village. The contents of fuorine in coal, clay used for coal combustion, mixed fuel of coal and clay, corn, and chili from households of the three villages were determined by the pyrohydrolysis-fluorine ion-selective electrode method. The average contents of fluorine in the above samples respectively are 237 mg/g, 2262 mg/g, 828 rag/g, 1419 mg/g, and 110 mg/g. The clay used for coal combustions is the main fluorine source of endemic fluorosis and the inferior coal and weathered coal are the secondary source of fluorine. During the combustion of mixed fuel of coal and clay, about eighty percent of fluorine was volatilized, approximately two thirds of which was from the clay and the other one third from the coal. The occurrence of fluorine in clay used for coat combustion is closely related to apatite and hornblende. The contents of fluorine in corn and chili, dried by coal-clay mixed fuel are about 1400 and 73 times higher than the permitted level of fluorine in foods according to the Chinese Standard. It is worth paying attention to the high-fluorine indoor surroundings, such as coal, clay, corn, and chili, particularly ash from boiler bottom with the fluorine content of 15738 ~g/g. Besides the technologies of fluorine fixation during the combustion, changes in living habits of the residents will help reduce the fluorine absorption, for example, washing the corn and chili before eating and improving the ventilation condition.

Partitioning of natural radionuclides in the waste streams of coal-fired utilities.

Five coal-fired electric utility plants were sampled to determine radionuclide concentrations in all major process streams. The results, together with plant operating data, were used to track the following six naturally occurring radionuclides: 238U, 226Ra, 210Po, 210Pb, 230Th and 232Th. For each plant, radionuclide balances were computed and the amount and extent of volatilization and enrichment of any radionuclides in the stack effluent were determined. In general, most of the radioactivity was found in boiler bottom ash or particulate control equipment hopper ash; atmospheric emissions were quite small in comparison. Radionuclides in the stack effluent were not detected in the gaseous state and some (especially 210Po and 210Pb) were preferentially associated with the smallest fly-ash particles.