Fundamental study on iron ore sintering new process of flue gas recirculation together with using biochar as fuel

It is of great significance for cleaner production to substitute bio-energy for fossil fuels in iron ore sintering. However, with the replacement ratio increasing, the consistency of heat front and flame front is broken, and the thermal utilizing efficiency of fuel is reduced, which results in the decrease of yield and tumble index of sinter. Circulating flue gas to sintering bed as biochar replacing 40% coke, CO in flue gas can be reused so as to increase the thermal utilizing efficiency of fuels, and the consistency of two fronts is recovered for the circulating flue gas containing certain CO2, H2 O and lower O2, which contributes to increasing the maximum temperature, extending the high temperature duration time of sintering bed, and results in improving the output and quality of sinter. In the condition of circulating 40% flue gas, the sintering with biomass fuels is strengthened, and the sintering indexes with biomass fuel replacing 40% coke breeze are comparative to those of using coke breeze completely.

Effect of steam spraying on a sintering bed on sinter quality and the emission of flue gas pollutants

The technology for spraying a sintering bed and thus improving sinter quality indicators while reducing the emission of flue gas pollutants has recently become an important research topic.The impacts on sinter quality and emissions when spraying the sintering surface with different amounts and flow rates of steam were investigated in this study.The sinter quality indicators were most effectively improved by spraying 180 g of steam flow continuously at a rate of 0.02 m^(3)/min for 15 min after ignition for 8 min.The optimal effect on emission reduction was obtained by spraying 90 g of steam flow continuously at a rate of 0.01 m^(3)/min for 15 min after ignition for 8 min.

Simultaneous desulfurization and denitrification of sintering flue gas via composite absorbent

Experiments on simultaneous absorption of SO_2 and NO_X from sintering flue gas via a composite absorbent NaClO_2/NaClO were carried out. The effects of various operating parameters such as NaClO_2 concentration(ms), NaClO concentration(mp), molar ratio of NaClO_2/NaClO(M), solution temperature(TR), initial solution pH, gas flow(Vg) and inlet concentration of SO_2(CS) and NO(CN) on the removal efficiencies of SO_2 and NO were discussed. The optimal experimental conditions were determined to be initial solution pH = 6, TR=55 °C and M = 1.3 under which the average efficiencies of desulfurization and denitrification could reach99.7% and 90.8%, respectively. Moreover, according to the analysis of reaction products, it was found that adding NaClO to NaClO_2 aqueous solution is favorable for the generation of ClO_2 and Cl_2 which have significant effect on desulfurization and denitrification. Finally, engineering experiments were performed and obtained good results demonstrating that this method is practicable and promising.

Development and applications of Baosteel sintering flue gas desulphurization technology

The research background and technical features of Baosteel sintering flue gas desulphurization （ FGD）--swirl- jet-absorbing wet limestone-gypsum sintering FGD technology, process and equipment are introduced in this paper. Main contents and achievements of the pilot experiment and the engineering practice of Baosteel FGD are analyzed and discussed systematically. Past engineering practice experiences indicate that Baosteel FGD has the following merits： wide applicability to sintering flue gas features, such as frequently changing temperatures, unstable SO2 concentration, intensively fluctuating flow rates ,etc. ,high pollutants removal efficiency ,low investment and energy consumption; stable and reliable operation ,utilizable byproduct （gypsum）, etc. It indicates that Baosteel sintering FGD is of extensive application value for the FGD of large and medium-scaled sintering machines.

NO_x reduction in the sintering process

A new process, NOx reduction with recycling flue gas and modifying coke breeze, was proposed. The effects of modified coke breeze and recycled flue gas on NOx reduction were investigated by sinter pot tests. The results show that the NOx reduction rate is over 10wt% in the sintering of modified coke breeze, the effects of the additives on NOx reduction are： CeO2〉CaO〉K2CO3. The NOx reduction rate increases with the amount of recycled flue gas, and is 22.35wt% in the sintering with recycling 30vol% of the flue gas. When 30vol% of the flue gas is recycled into the sintering of CeO2, CaO, and K2CO3 modified coke breeze, the NOx reduction rates are 36.10wt%, 32.56wt%, and 32.17wt%, respectively.

Research and industrial testing of dioxin emission reduction technology in the sintering process

Based on an analysis of the chlorine elements in each component of the sintering mixture,industrial tests of the use of dioxin reduction techniques in the sintering process were found to reduce the chlorine sources and inhibit the formation of dioxins.The dioxin reduction effect obtained in the industrial experiment was better than that in the sintering pot experiment,but their patterns were consistent.When urea is used as an inhibitor,the dioxins can be significantly reduced.When a 0.02%ratio of urea was added,a maximum dioxin emission reduction of 79%was obtained.Reducing the chlorine sources also had an obvious dioxin reduction effect,enabling a 69.49%reduction.In addition,when these two technologies were applied simultaneously,a significant emission reduction rate of 92.23%was achieved.The concentration of dioxins in flue gas dropped to 0.2421 ng TEQ/m^(3) before desulfurization,which meets the emission standard for dioxins in the final exhaust gas.

Study on influencing factors of Baosteel’s swirl-jet sintering FGD technology

This paper introduced the research background and technical features of Baosteel＇ s sintering flue gas desulfurization （FGD）. It was also named swirl-jet-absorbing wet limestone-gypsum sintering FGD technology. By means of industrial online pilot plants, through continuous running and orthogonal tests, the effects of various influencing factors on SO2 removal efficiency of Baosteel sintering flue gas desulgurization （BSFGD） were studied carefully. The results indicate that the slurry pH value,temperature （T） and flow rate （Q） of inlet flue gas,liquid level （H） in the absorber and flue gas jet velocity （V） are the main influencing factors. Furthermore, when pH is between 5.0 and 5.5, H is between 4.2 m and 4.3 m, Q is 43 000 m3/h, T is below 65℃ and V is between 20 m/s and 28 m/s, the best desulfurization efficiency can be available.

Gas-phase and particle-phase PCDD/F congener distributions in the flue gas from an iron ore sintering plant

The activated carbon injection-circulating fluidized bed（ACI-CFB）-bag filter coupling technique was studied in an iron ore sintering plant. For comparison, the removal efficiencies under the conditions without or with ACI technology were both evaluated. It was found that the polychlorinated dibenzo-p-dioxins and dibenzofuran（PCDD/F） removal efficiency for total international toxic equivalence quantity（I-TEQ） concentration was improved from 91.61% to 97.36% when ACI was employed, revealing that ACI was very conducive to further controlling the PCDD/F emissions. Detailed congener distributions of PCDD/Fs in the gas-phase and particle-phase of the Inlet and Outlet samples were determined. Additionally, the PCDD/F distribution for the Fly ash-with ACI sample of was also studied.

CO_(2)emission evaluation and cost analysis of oxygen blast furnace process with sintering flue gas injection

In order to achieve ultra-low emissions of SO_(2)and NO_(x),the oxygen blast furnace with sintering flue gas injection is presented as a promising novel process.The CO_(2)emission was examined,and a cost analysis of the process was conducted.The results show that in the cases when the top gas is not circulated(Cases 1–3),and the volume of injected sintering flue gas per ton of hot metal is below about 1250 m^(3),the total CO_(2)emissions decrease first and then increase as the oxygen content of the blast increases.When the volume of injected sintering flue gas per ton of hot metal exceeds approximately 1250 m^(3),the total CO_(2)emissions gradually decrease.When the recirculating top gas and the vacuum pressure swing adsorption are considered,the benefits of recovered gas can make the ironmaking cost close to or even lower than that of the ordinary blast furnace.Furthermore,the implementation of this approach leads to a substantial reduction in total CO_(2)emissions,with reductions of 69.13%(Case 4),70.60%(Case 5),and 71.07%(Case 6),respectively.By integrating previous research and current findings,the reasonable oxygen blast furnace with sintering flue gas injection can not only realize desulfurization and denitrification,but also achieve the goal of reducing CO_(2)emissions and ironmaking cost.

Low-temperature oxidation behavior and mechanism of semi-dry desulfurization ash from iron ore sintering flue gas

The low-temperature wet oxidation behavior of semi-dry desulfurization ash from iron ore sintering flue gas in ammonium citrate solution was investigated for efficiently utilizing the low-quality desulfurization ash. The effects of the ammonium citrate concentration, oxidation temperature, solid/liquid ratio, and oxidation time on the wet oxidation behavior of desulfurization ash were studied. Simultaneously, the oxidation mechanism of desulfurization ash was revealed by means of X-ray diffraction, Zeta electric resistance, and X-ray photoelectron spectroscopy (XPS) analysis. Under the optimal conditions with ammonium citrate, the oxidation ratio of CaSO_(3) was up to the maximum value (98.49%), while that of CaSO_(3) was only 8.92% without ammonium citrate. Zeta electric resistance and XPS results indicate that the dissolution process of CaSO_(3) could be significantly promoted by complexation derived from the ammonium citrate hydrolysis. As a result, the oxidation process of CaSO_(3) was transformed from particle oxidation to SO_(3)^(2−) ion oxidation, realizing the rapid transformation of desulfurization ash from CaSO_(3) to CaSO_(4) at low temperature. It provides a reference for the application of semi-dry desulfurization ash and contributes to sustainable management for semi-dry desulfurization ash.

A pilot-scale study of selective desulfurization via urea addition in iron ore sintering

The iron ore sintering process is the main source of SO_2 emissions in the iron and steel industry. In our previous research, we proposed a novel technology for reducing SO_2 emissions in the flue gas in the iron ore sintering process by adding urea at a given distance from the sintering grate bar. In this paper, a pilot-scale experiment was carried out in a commercial sintering plant. The results showed that, compared to the SO_2 concentration in flue gas without urea addition, the SO_2 concentration decreased substantially from 694.2 to 108.0 mg/m^3 when 0.10wt% urea was added. NH_3 decomposed by urea reacted with SO_2 to produce（NH_4）_2SO_4, decreasing the SO_2 concentration in the flue gas.

Influence of O_2 Content in Circulating Flue Gas on Iron Ore Sintering

Circulating flue gas can reduce the emission of flue gas , and furthermore , it can reuse the waste heat effectively in the sintering process.Compared with conventional sintering , O2 that gets through the sintering bed decreases because of substituting circulating gas for air.The influences of O2 content on sintering process are studied through simulating the flue gas circulation sintering with artificial gas.It shows that , with the reducing of O2 content in circulating gas , the combustion speed of fuel decreases and incomplete combustion degree increases , which makes the flame front fall behind the heat front and reduces the heat utilization efficiency of fuel.The ultimate result is that the temperature of sintering bed decreases and the liquid phase reduces.In addition , the reducing atmosphere is strengthened because of flue gas circulation , which makes the magnetite increase yet calcium ferrite reduce gradually. Because the content of calcium ferrite with good strength reduces , the sinter yield and tumble strength decrease.To ensure the sinter index , the favorable O2 content of circulating flue gas is no less than 15%.

Operating condition influences on PCDD/Fs emissions from sinter pot tests with hot flue gas recycling

This study was designed to clarify the influence of operating conditions on the formation and emissions of polychlorinated-p-dibenzodioxins and dibenzofurans （PCDD/Fs） from a sintering process with hot flue gas recycling. A pilot scale sinter pot with simulated flue gas recycling was developed, and four key operational parameters, including temperature, oxygen content of the simulated waste flue gas, the coke rate of the sintering mixture, and the quicklime quality, were selected for exploring PCDD/Fs formation. The results showed that the temperature of the recycled flue gas had a major affect on PCDD/Fs formation, and a high temperature could significantly increase their formation during sintering. A clear linear correlation between the temperature of recycling flue gas and PCDD/Fs emission （r = 0.93） was found. PCDD/Fs could be reduced to a certain extent by decreasing the level of oxygen in the recycled flue gas, while sintering quality was unchanged. The coke rate had no significant influence on the formation of PCDD/Fs, but the quality of quicklime used in the sintering mixture could affect not only the amount of PCDD/Fs emissions but also the sintering productivity. Compared with a benchmark sinter pot test, PCDD/Fs emissions markedly decreased with improvements to quicklime quality. However, the reduction in PCDD/Fs emissions realized by using high-quality quicklime was limited by the temperature of the inlet gas. The highest reduction achieved was 51% compared with conventional quicklime when the temperature of the inlet gas was 150°C.

Effect of H_2O(g)Content in Circulating Flue Gas on Iron Ore Sintering with Flue Gas Recirculation

The influence of H2O （g） content in circulating flue gas on sintering was studied by simulating the flue gas circulating sintering. The results show that the burning speed of solid fuel and the heat transfer rate during sintering process are improved when the H2O （g） content increases from 0 to 6%, which accelerates the sintering speed. However, when the H2O （g） content exceeds 6 %, the over-wet zone in sinter bed is thickened, which deteriorates the permeability of sintering bed. In addition, the magnetite content in sinter increases, while the acicular calcium ferrite content decreases. Accordingly, the sinter yield and tumble index decrease with excessive H2O （g） content. To guarantee the yield and quality of sinter, the favourable H2O （g） content in circulating flue gas should be controlled to be less than 6%.

O_(3)oxidation combined with semi-dry method for simultaneous desulfurization and denitrification of sintering/pelletizing flue gas

With the vigorous development of China's iron and steel industry and the introduction of ultra-low emission policies,the emission of pollutants such as SO_(2)and NO x has received unprecedented attention.Considering the increase of the proportion of semi-dry desulfurization technology in the desulfurization process,several semi-dry desulphurization technologies such as flue gas circulating fluidized bed(CFB),dense flow absorber(DFA)and spray drying absorption(SDA)are briefly summarized.Moreover,a method for simultaneous treatment of SO_(2)and NOx in sintering/pelletizing flue gas by O_(3)oxidation combined with semidry method is introduced.Meantime,the effects of key parameters such as O_(3)/NO molar ratio,Ca SO_(3),SO_(2),reaction temperature,Ca/(S+2 N)molar ratio,droplet size and approach to adiabatic saturation temperature(AAST)on denitrification and desulfurization are analyzed.Furthermore,the reaction mechanism of denitrification and desulfurization is further elucidated.Finally,the advantages and development prospects of the new technology are proposed.

Properties change of activated coke for sintering flue gas purification in cyclic removal of SO_(2) and NO_(x)

The properties of activated coke(AC)for sintering flue gas purification greatly affect the efficiency of desulfurization and denitration,but they gradually change during cycles.The change in properties of coal-based AC during cycles was studied to clarify the change law and AC optimization index.The AC oxygen content rapidly increases 13.49 to 17.87 wt.%in the early cycles to form phenol,which promotes the denitration rate 55.63%to 78.20%.The denitration performance slowly increases in subsequent cycles becaof the generation of quinone AC slow oxidation.However,the oxygen-containing groups are not conducive to adsorption capacity of AC for NO.The adsorbed NO species which can be replaced SO2 is the main NO species on AC,and its amount decreases with the decrease in CC content of AC.The AC chemical loss leads to the opening of closed pores,expansion of original pores and formation of new pores,causing micropore volume to increase 0.085%to 0.152%,compressive strength to decrease 472 to 336 N,and abrasive resistance to decrease 97.87%to 94.16%during cycles.The low oxygen content and high micropore volume are favorable to the initial desulfurization performance,and the former is more decisive.After a while,the desulfurization rate is linearly positively correlated with the micropore volume regardless of the chemistry.4-h desulfurization rate increased 69.03%to 85.91%during 25 cycles due to the increasing micropore volume.The AC properties change in cycles will greatly affect the desulfurization and denitration rate in the height direction of the flue gas purification system.Selecting the coal-based AC with moderate micropore volume,easy oxidation surface and less original oxygen-containing groups facilitates the better purification efficiency at lower cost for sintering plants.

Sintering flue gas desulfurization with different carbon materials modified by microwave irradiation

Modification of metallurgical coke,biomass char and semi-coke was carried out using a microwave device with power of 450-850 W and irradiation time of 6-12 min.The desulfurization rates of three carbon materials before and after modification were tested.The effects of microwave power and irradiation time on the pore texture and surface chemical characteristics of the three carbon materials were examined by SEM,BET and Fourier transform infrared spectroscopy（FTIR）.The results showed that the specific surface area,total pore volume and pore diameter of biomass char and semi-coke after irradiation decreased slightly.Noteworthily,the pore diameter turned small and the acidic functional groups on their surface decomposed,thereby the basicity of carbon surface increased by microwave modification.The optimal promotion of desulfurization rate of three carbon materials was semi-coke irradiated at 850 W for 9 min and the sulfur dioxide adsorption rate was up to 45%.

Analysis of operational parameters affecting denitrification rate of sintering flue gas in cross-flow activated coke purification facility

The denitrification rate of the cross-flow activated coke flue gas purification facility varies with operational parameters. According to the simulated experiments, the denitrification rate with the height drop of the denitrification unit experiences 100%, rapid decreasing, and gradual rising to the equilibrium. According to the correlation analysis results based on production data, several operational parameters affecting the denitrification rate have been obtained. The denitrification rate has negative relationships with the activated coke bed temperature, the flue gas flow, the H2O content, the SO2 content and the NH3 slip, and has positive relationships with the O2 content, the NOx content, the NH3–NOx molar ratio, the flue gas pressure and the regeneration temperature. Properly increasing the sintering air leakage or the cooling air added into flue gas is beneficial to increase the denitrification rate. Priority should be given to O2, NH3–NOx molar ratio and flue gas flow to improve the denitrification rate. Additionally, a linear model, which had been validated, was developed and can be used to predict and control the denitrification rate.

静电除尘在烧结机头烟尘治理中的应用

通过对安钢烧结机一、二期工程中烧结机头电除尘器结构性能和运行效果对比 ,结合安钢实际运行情况 ,分析了一期工程中电除尘器运行存在的问题 ,重点对电除尘器的结构特点进行阐述 。

烧结工艺余热利用多种技术方案的比较研究

文章分析了烧结工艺烟气余热利用的情况及其存在问题,指出在目前烧结环冷机余热基本上已得到利用的基础上,若能对烧结机尾烟气余热进行利用,可以有效地提高烧结工艺余热利用的效率,为此,以某钢铁企业烧结设备为例,提出了3种技术改造方案,并进行了节能效果分析。