Aerodynamic Characteristics of the Combustion Process of Sawdust in a Vortex Furnace with Counter-Swirling Flows

The aim of this work is to study the working processes of burning the low-quality fuels, namely, the saw dust in the swirling-type furnaces with an opposite twisted motion of the air. The goal was achieved using the physical and mathematical modeling of the flows interaction. The article presented the results of numerical study of aerodynamic characteristics of burning the saw dust in the swirling-type furnace with the opposite twisted air flows. For the research, the facility was used for the saw dust burning with the air supply into the lower and upper zones of burning. The most essential result of the work was modeling of the working process at the ratio of the flows of the primary air and secondary air without the fuel admixture, equal to 0.2. The tangential rate of the flow changed according to the horizontal sections from 3-5 m/s to 40-42 m/s and with respect to the furnace height from 51 m/s to 30 m/s. The average angular rate of the mixture changed relatively the furnace height in the ranges of 171-500 l/s to 100—300 l/s. The significance of the results obtained consists in determination of the possibility of increasing the efficiency of the work of the furnace facilities at the expense of the introduction of the primary and secondary air flows. In this situation, the optimal ratio of consumptions of primary and secondary air was 0.2. Thus, in this work the consumption of primary air was 1.285 kg/s, the consumption of the secondary air was 0.255 kg/s.

Elaboration and realization of new approaches to diagnostic and control of blast furnace heat

Under conditions of unstable supply of quality charge materials and technological fuel, the elaboration of new effective means of blast furnace heat control becomes actual for reaching acceptable technical and economic indices of its operation. Results of the studies carried out at the BF No. 3 of Enakievo steel-works (EMZ, Ukraine) during the period from October 2011 until December 2016 presented. During the period, various fuel additives to the blast were used within a wide range of their variation, and composition of charge materials was characterized by numerous components and variable quality. In the charge content, various additives were used: iron ore, limestone, BOF slag, briquettes of pellets siftings, manganese-containing additives. The new approach to the selection of rational charging programs was justified, providing stable economic BF running under variation of heat technological conditions. For the first time the temperature indices of estimation of gas stream distribution along the furnace radius were elaborated, the rational ranges of their variation at the operation under various gas-dynamic and fuel conditions determined, requirements to the gas stream temperature distribution along the furnace radius formulated. Based on analysis of information about lining temperature along the furnace height over the five year of EMZ BF No. 3 running, its values were ascertained, showing the partial or complete lining wear in the middle and upper part of the shaft. For the lining of the furnace bottom and other parts the temperature was ascertained, showing the formation in the lower zone unstable protective scull, as well the temperature characterizing its complete absence. The influence of blast mode during addition into it an increased volume of steam, natural gas and pulverized coal on variation of distribution of peripheral gas stream temperature along the furnace height from the tuyere zone to the top studied. It became a reason for an elaboration a method of the identification of the viscous-plastic state zone border in the peripheral zone of the furnace. Regulations of the blowing-in of blast furnaces after a long time stoppage without tapping the emergency hot metal elaborated. The technology of usage manganese-containing materials in the BF charge adjusted, which demonstrated the most effective washing out of the hearth under conditions of low and unstable charge materials quality and pulverized coal injection.

Analisis sistem ruang bakar boiler jenis fluidized bed combustion untuk PLTU kapasitas 8 MW

Boiler adalah alat yang berfungsi untuk memanaskan air untuk menjadi uap bertekanan dan bertemperatur tinggi, dengan menggunakan panas dari hasil pembakaran bahan bakar pada ruang bakar. Analisa sistem ruang bakar pada boiler jenis fluidized bed combustion dilakukan dengan menghitung parameter-parameter desain sistem ruang bakar dan pengaruh perubahan jenis bahan bakar terhadap efisiensi dari desain ruang bakar. Parameter-parameter sistem ruang bakar tersebut yaitu nilai laju kalor pembangkitan uap, proses pembakaran, heat balance, fuel heat input, mass balance, furnace cross section, furnace height, dan ketebalan dinding ruang bakar. Hasil perhitungan diketahui bahwa untuk membangkitkan daya PLTU dengan kapasitas 8 MW membutuhkan kalor pembangkitan uap sebesar 6279 kcal/kw-h dengan kemampuan produksi uap sebesar 9,58 kg/s dan konsumsi bahan bakar sebesar 1,196 kg/s. Sedangkan hasil perhitungan parameter-parameter desain sistem ruang bakar diperoleh dimensi luas ruang bakar sebesar 109,871 m2, luas dinding ruang bakar 103,67 m2, luas penampang bed sebesar 8,858 m2, panjang 4,21 m, lebar 2,105 m, tinggi 8,21 m, dan ketebalan dinding ruang bagian luar menggunakan material blanket alumina silica fiber dengan ketebalan 1,893 cm serta bagian dalam menggunakan material fireclay brick dengan ketebalan 30,45 cm. Berdasarkan parameter-parameter tersebut maka pengaruh perubahan jenis batu bara berpengaruh terhadap efisiensi sistem ruang bakar boiler. Untuk kecepatan fluidasi sebesar 4,293 m/s jenis bahan bakar sub bituminus mampu menghasilkan efisiensi sistem ruang bakar boiler jenis fluidized bed sebesar 85,824 %.

Air staging application effects on overall steam boiler operation

This paper presents the results of calculation system of main processes in power steam boiler, before and after application of air staging. Modified air injection scheme was implemented during 2015 on the power steam boiler within unit 1 of TPP Kostolac B. Measurements performed on site showed that applied reconstruction led to a permanent loss of the steam boiler power. This study was performed in order to define the cause of such an occurrence and to consider the possibility for regaining the designed steam parameters along with keeping NO concentration in prescribed limits. This paper x discusses the influence of repositioning the air injection location on processes within the furnace. Furthermore, the influence of the redistribution of injected air-flow along the furnace height on important boiler operation parameters has been analyzed. Analysis showed that, with appropriate dosing of air along the height of the existing furnace, it is possible to achieve the optimum of the boiler's operation parameters. Results of research showed that air staging throughout the furnace height in best test case additionally reduces NO concentration (195-225 mg/Nm3) and increases the power of x considered boiler (828.8-751.1 MW) with an insignificant decrease of the boiler's efficiency (86.27-86.77%). Furthermore, the designed temperatures of superheated (540-498?C) and reheated (540-518?C) steam have been reached again, whereby the safety of the boiler's operation has been significantly increased. Results of this study improve the present explanation of the processes occurred in the furnace with applied primary measures. They also give directions on defining the most influential parameters on considered processes with the final purpose to increase the efficiency and availability of the entire plant.

Benefits and risks of blast furnaces with high intensity

Increase in the intensity of blast furnace smelting at NLMK JSC is achieved by improving quality of coke and iron ore materials, by increasing pressure under the blast furnace mouth and by oxygen enrichment. It is accompanied by an increase in the rate of wustite indirect reduction and decrease in specific heat losses with cooling water. However, the risks of burden yield problems are significantly lower with high intensity. It has been established that with the change in quality of charge materials, reason for burden yield problems can be also the variation in ore load ratio along the furnace radius. A new method for diagnosing causes of burden yield problems was developed. Using method of mathematical modeling, effect of change in ore load and size of iron-ore materials on peripheral gases temperature change and the degree of CO use were analyzed. The method is based on analysis of joint change in gas temperature and degree of CO use in peripheral area. Analysis of peripheral gases temperature variation and degree of CO use makes it possible to identify reasons of pressure drops along the furnace height. As a result of analysis of pressure drops dynamics changes along the furnace height, there have been found signs that can be used to judge the probability of burden yield problems. The possibility of reducing pressure drops due to redistribution of ore load along the furnace radius and the amount of gases is considered. It is shown that various methods of reducing the amount of gases are accompanied by different changes in coke consumption and furnace productivity. Mathematical model has been developed to select the best combination of parameters changing of the fuel-enriched blast in specific conditions.

A comparison of fuzzy logic and cluster renewal approaches for heat transfer modeling in a 1296 t/h CFB boiler with low level of flue gas recirculation

The interrelation between fuzzy logic and cluster renewal approaches for heat transfer modeling in a circulating fluidized bed (CFB) has been established based on a local furnace data. The furnace data have been measured in a 1296 t/h CFB boiler with low level of flue gas recirculation. In the present study, the bed temperature and suspension density were treated as experimental variables along the furnace height. The measured bed temperature and suspension density were varied in the range of 1131-1156 K and 1.93-6.32 kg/m3, respectively. Using the heat transfer coefficient for commercial CFB combustor, two empirical heat transfer correlation were developed in terms of important operating parameters including bed temperature and also suspension density. The fuzzy logic results were found to be in good agreement with the corresponding experimental heat transfer data obtained based on cluster renewal approach. The predicted bed-to-wall heat transfer coefficient covered a range of 109-241 W/(m2K) and 111-240 W/(m2K), for fuzzy logic and cluster renewal approach respectively. The divergence in calculated heat flux recovery along the furnace height between fuzzy logic and cluster renewal approach did not exceeded ±2%.

Experimental Study on the Pollutants Release Characteristics During Combustion of Lean Coal with Different Coal Rank

In this paper, the characteristics of SO2 and NO release during combustion of lean coal with different coal rank were experimentally studied in the one-dimensional furnace for pulverized coal combustion. The results showed: The coal property and proportion of the component coals have great influence on the characteristics of SO2 and NO release. The releasing concentration of SO2 and NO distributing along the furnace height is generally between that of component coals, and the releasing characteristics of SO2 and NO would be more near to that of the larger proportion coal. The measuring value of the formation concentration of SO2 and NO are different from the calculating value based on the weighted means of the component coals to a certain extent. While the different coal are added to lean coal, the time corresponding with peak value releasing concentration of SO2 and NO is different.