Chapter 19 - Sintering emissions and mitigation technologies

The aim of this article is to investigate the removal of polycyclic aromatic hydrocarbons (PAHs) by sorbent injection from the flue gas during municipal solid waste (MSW) incineration. For this purpose, the incineration tests of MSW were performed in a fluidized bed incinerator and the influence of sorbent on PAHs was studied. The samples analyzed were taken from the raw MSW, the flue gas, the fly ash, and the bottom ash. The 16 PAHs specified by the U.S. EPA were analyzed by a high performance liquid chromatography (HPLC). The results obtained show that there were a few PAHs in the raw MSW and the bottom ash. The total PAHs in the fly ash and the flue gas were dominated by 3- to 5-ring PAHs and 2- to 4-ring PAHs, respectively. The removal efficiency of PAHs increased with the rise of activated carbon, and the removal efficiency of PAHs by kaoline was better than activated carbon and activated bauxite. PAHs could be effectively removed by sorbent injection from the flue gas during the MSW incineration.

Emission characteristics and impact factors of air pollutants from municipal solid waste incineration in Shanghai, China

Multi-objective optimization and Techno-economic analyses of conventional combustion and chemical looping combustion for a Municipal solid waste incineration plant in China.

JFE Steel Corporation developed the hydrogen-based gas fuel injection technology for sintering machines to improve sinter quality without increasing coke breeze ratio. With the technology, it is possible to extend the temperature zone between 1200°C and 1400°C by injecting the gaseous fuel from the top surface of the sintering machine as a partial substitute for coke breeze. Theoretical and experimental studies were carried out to verify the effect of the gaseous-fuel injection technology on pore structure in the sinter cake with the X-ray CT scanner and sintering pot test.It is important to hold the temperature between 1200°C and 1400°C in order to produce high strength and high reducibility sinter. The liquid phase ratio can be increased with extending the proper temperature zone by applying the gaseous fuel injection technology. The increase in liquid phase ratio promotes the combination of pores (1–5 mm) and sinter strength is improved. At the same time, the pores over 5 mm growth are promoted and the permeability is improved in the sintering bed. Moreover, the low-temperature sintering process depresses the iron ore self-densification. Micro pores under 1 μm remain in unmelted ores and improve sinter reducibility. As a result, the technology enables to improve the pore structure in the sinter cake and sinter quality.The technology was put into commercial operation at Keihin No. 1 sinter plant in January 2009 and stable operation has continued up to the present. As a result, the energy efficiency in the sintering process is greatly improved, and it has been achieved to reduce CO2 emissions by a maximum of approximately 60000 t/year at Keihin No. 1 sinter plant.

Sources of dioxins in the United Kingdom: the steel industry and other sources

Experimental study on the removal of PAHs using in-duct activated carbon injection

Sintering is the most economic and widely used agglomeration process to prepare iron ore fines for blast furnace use. Owing to the depleting reserves of traditional high grade iron ore, there have been considerable changes in iron ore resources available throughout the world, especially in steel mills in East Asia. Corresponding to the changes in the availability of iron ore resources, the amount of impurities in iron ore has been slowly increasing. Some of these impurities have been found to have deleterious impacts on sinter quality and sintering performance. In the meantime, an increasing number of large blast furnaces with inner volumes of more than 5000 m3 have been built in East Asia which require more sinter and are often more demanding in terms of the quality requirements of the ferrous materials. Finally, sinter plants are facing increasing pressure due to more stringent regulations regarding their environmental impact. This paper gives an overall review of a variety of technologies developed worldwide to tackle the changing raw material characteristics and mitigate emissions from sintering operations. Given the high sinter usage and volume of their blast furnaces, most of the recent sintering technologies have originated from East Asia, particularly Japan.

Iron ore sintering is an established thermal agglomeration process where fine iron ores are fused together to produce a coarser product which is a suitable burden material for blast furnaces. Due to the scale of blast furnace demands, a typical steelworks sinter plant can produce thousands of tonnes of sinter every day which in turn results in the formation of significant quantities of dusts. The majority of these dusts will be captured and reused in the process due to their iron content. However, dusts released to atmosphere can create environmental concerns and they can also be problematic to the sintering process itself. This thesis considers two major aspects related to the optimisation of environmental emissions from blast furnace sinter production; namely sinter dusts and the addition of recycled steelmaking material by-products (reverts) back into the sintering process. Firstly, considering sinter dusts, these are removed from the exhaust stream using processes including electrostatic precipitators (ESPs). But the dusts must be removed from ESP plates to maintain dust removal efficiency. The dusts consist of sinter sub-components and metal chlorides. Although an established method for removing chlorides from the dusts, following an industrial scale trial carried out by Tata Steel UK, in this thesis, experiments have been carried out to optimise the water washing process of sinter plant waste dust. This involved varying parameters such as washing time, agitation speed and liquid to solid ratios. Initial tests confirmed that > 95 % of soluble chlorides within the dusts can be mobilised by water washing with only one wash under standard operating conditions. Experiments were then carried out to assess whether the washing solution could be effectively recycled to wash more dusts. Results showed that the washing solution could still mobilise chloride from the dust for up to ten cycles, although there was decline in effectiveness at later cycles. One issue noted during these experiments was the hydrophobicity of ESP dust, making it harder to work with during washing and even allowing some dust to apparently remain dry after washing. To combat this, more dust washing experiments were then carried out which featured the inclusion of surfactants, the aim being for the surfactants to mitigate the hydrophobic effects. Three surfactants were tested, each of varying properties, and all showed positive impacts to the processing of the dust, TX-100 being the most effective. More detailed analysis of the surfactants outside of a dust washing setting was also undertaken and confirmed that TX-100 was more effective at tackling the dusts hydrophobicity. Upon completion of dust washing experiments, tests were undertaken using a pilot-scale sinter pot to better establish the impacts of sintering before and after washing the dusts. These results showed impacts on sinter strength and dust production when including both dust types, although utilising the washed dust appeared to result in higher dust emissions. Furthermore, both dusts were then micro-pelletised and sintered alongside sinter blends with the same dust content, to establish if reducing the fines content in the sinter blend could allow their use at higher rates. These showed that pelletising the dusts greatly improved the sinter bed permeability, aided sinter strength and reduced dust emissions. Overall, this thesis considers the environmental optimisation of raw material sintering for steel manufacturing, focusing on the remediation and recycling of input materials. Investigating how these processes can be improved and identifying any impacts on process quality, product quality and dust emissions.

Effect of magnetite on the catalytic oxidation of polycyclic aromatic hydrocarbons in fly ash from MSW incineration: A comparative study of one-step and two-step hydrothermal processes

Polycyclic aromatic hydrocarbon (PAH) emission from co-firing municipal solid waste (MSW) and coal in a fluidized bed incinerator

Commercial sinter plants are currently exploring the potential addition of high-grade iron ore concentrate in sinter production to improve the sinter grade for sustainable ironmaking. It is known that a significant proportion of ultrafine iron ore concentrates in the sinter blend has a negative impact on the permeability of the sinter bed. Consequently, an adverse effect on the overall productivity of the sinter plant. This study provides an overview of some of the commercially applied sintering technologies installed as countermeasures to the loss of productivity and assesses their capability to accommodate significant proportions of ultrafine iron ore resources. It is noted that retrofitting existing technologies is required to sustain and stabilise the ironmaking process as well as reduce CO 2 emission levels. A conceptual illustration of a sustainable sinter plant is also proposed accounting for these factors.

The emission of polycyclic aromatic hydrocarbons (PAHs) during start-up, burning, and burn-out were determined for four municipal solid waste MSW incinerators. During start-up conditions, PAH concentrations were shown to be high due to unstable combustion. A positive correlation was seen between PAH concentrations and the organic carbon content of the dust. This study was conducted to examine the emission behaviors of PAHs according to furnace type and to measure emissions during the combustion cycle. The organic carbon in the dust, as well as PAH emissions, during three combustion periods were determined for four MSW incinerators. PAHs were high during start-up because of incomplete combustion at low temperature. In the fluid-ized-bed incinerator, PAHs were high because combustion in the fluidized bed, was more unstable than in the step grate. A batch fluidized bed showed particularly higher concentrations compared to a continuous fluidized bed, owing to less stable combustion. Organic carbon in the dust was normally highest during start-up and lowest during burning. Continuous incinerators with longer operation periods showed higher emission rates during burning. This parameter for the batch-type fluidized bed increased during start-up and burn-out.

Studies into the formation of PBDEs and PBDD/Fs in the iron ore sintering process

The variation of the O 2 content in the suction gas, in the range from 7 to 30 vol.%, during the iron ore sintering process, is investigated. Miniaturized laboratory-scale sintering experiments are carried out using an industry-like raw mixture to study the effects of O 2 variation on the sintering process with particular emphasis on the off-gas composition, specific sintering parameters and the sinter strength as well as the chemical composition of the sinter. After the ignition at the bed surface, the gas hood is placed on the sintering column, allowing a synthetic gas mixture to be drawn through the sinter bed until the burn-through point is reached. For additional interpretation of the experimental results, the theoretical coke combustion rate as a function of the oxygen partial pressure was calculated and plotted against the experimentally measured peak temperature in the sinter bed of the respective sinter series. An increasing O 2 content in the suction gas results in a faster flame front speed combined with a more gradual temperature rise of the heat wave and longer dwell time in the melt phase formation temperature range. Due to the more pronounced flame front, both sinter yield and strength increase, resulting in lower return rates. Below 12 vol.% O 2 , a sharp decrease in sinter yield and strength can be observed, probably due to the low extent of melt phase formation and the associated minor formation of silico ferrite of calcium and aluminum (SFCA). The carbon burnout as well as the calcination increases with increasing the O 2 content in the suction gas, resulting in higher levels of CO 2 in the off-gas, with more or less constant amounts of CO above 15 vol.% O 2 . The amounts of NO and SO 2 show a similar trend with a continuous increase with increasing O 2 supply, with the SO 2 breakthrough starting earlier and being released over a shorter period. The chemical analysis of the sinter indicates the highest Fe(II) values in the range of 12–21 vol.% O 2 in the suction gas.

Mixed incineration of municipal solid waste (MSW) in existing coal gangue power plant is a potentially high-efficiency and low-cost MSW disposal way. In this paper, the co-combustion and pollutants emission characteristic of MSW and coal gangue was investigated in a circulating fluidized bed (CFB) combustor. The effect of MSW blend ratio, bed temperature and excess air ratio was detailedly studied. The results show the NOx and HCl emission increases with the increasing MSW blend ratio and the SO2 emission decreases. With the increase of bed temperature, the CO emission decreases while the NOx and SO2 emission increases. The HCl emission is nearly stable in the temperature range of 850–950 °C. The increase of excess air ratio gradually increases the NOx emission but has no significant effect on the SO2 emission. The HCl emission firstly increases and then decreases with the increase of excess air ratio. For a typical CFB operating condition with excess air ratio of 1.4, bed temperature of 900 °C and MSW blend ratio of 10%, the original CO, NOx, SO2 and HCl emissions are 52, 181, 3373 and 58 mg/N m3 respectively.