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.

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.

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 NOx,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.

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.

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%.

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.

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%.

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%.

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.

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.

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.

Target the neglected VOCs emission from iron and steel industry in China for air quality improvement

Recent years have witnessed significant improvement in China’s air quality.Strict environmental protection measures have led to significant decreases in sulfur dioxide(SO2),nitrogen oxides(NOx),and particulate matter(PM)emissions since 2013.But there is no denying that the air quality in 135 cities is inferior to reaching the Ambient Air Quality Standards(GB 3095–2012)in 2020.In terms of temporal,geographic,and historical aspects,we have analyzed the potential connections between China’s air quality and the iron and steel industry.The non-target volatile organic compounds(VOCs)emissions from iron and steel industry,especially from the iron ore sinter process,may be an underappreciated index imposing a negative effect on the surrounding areas of China.Therefore,we appeal the authorities to pay more attention on VOCs emission from the iron and steel industry and establish new environmental standards.And different iron steel flue gas pollutants will be eliminated concurrently with the promotion and application of new technology.