Utilisation of the binders prepared from coal tar pitch and phenolic resins for the production metallurgical quality briquettes from coke breeze and the study of their high temperature carbonization behaviour

To reduce the cost of the formed coke briquettes which can be used as a substitute fuel to the metallurgical coke for the blast furnace from the coke breeze alternative binders and their blends were used. The high temperature behavior was investigated. The binders tested were: the nitrogen blown, air blown coal tar pitch and the blend of air blown coal tar pitch with the phenolic resins blends. The phenolic resin blends were prepared by mixing equal amount of resole and novalac. From the results, nitrogen blowing resulted in the weakest briquettes. The air blowing procedure should be preferred in place of nitrogen blowing for this purpose. When the air blown coal tar pitch was used alone as a binder, the briquettes must be cured at 200 °C for 2 h, then carbonized at a temperature above 670 °C. Since it requires higher temperature at carbonization stage, using air blown coal tar pitch alone as a binder was not economical. Therefore, the briquettes were prepared from the blended binder, containing air blown coal tar pitch and phenolic resins blend. The optimum amount of air blown coal tar pitch was found to be 50% w/w in the blended binder. Curing the briquettes at 200 °C for 2 h was found to be sufficient for producing strong briquettes with a tensile strength of 50.45 MN/m². When these cured briquettes were carbonized at temperatures 470 °C, 670 °C and 950 °C, their strength were increasing continuously, reaching to 71.85 MN/m² at the carbonization temperature of 950 °C. These briquettes can be used as a substitute for the metallurgical coke after curing; the process might not require un-economical high temperature carbonization stage.     

Phenolic resin binder for the production of metallurgical quality briquettes from coke breeze: Part II the effect of the type of the basic catalyst used in the resol production on the tensile strength of the formed coke briquettes

In order to develop a new and cost effective formed coke production process which does not require higher temperature carbonization stage, coke breeze was briquetted with resol binders and the change in the tensile strength of the briquettes with the amount and the type of the alkaline metal hydroxides, alkaline earth metal oxides, their carbonates and amine catalysts were studied. It was recognized that carbonates of alkaline or alkaline earth metals have a modifying effect on the properties of resol binders which results in briquettes of higher tensile strength than the resol produced with hydroxide or oxides of these metals. The average tensile strength of the briquettes was found to be much higher with the sodium carbonates catalyzed resol used as binder comparing with sodium hydroxide catalyzed resoles. The former was 45.40 MPa while the latter was 33.72 MPa. Although triethanolamine catalyzed resol, resulted in the briquettes of the highest tensile strength (53.43 MPa), among the catalyst studied in this work, due to flammability caused by triethanolamine, it was found unsuitable for this purpose.     

Molasses and air blown coal tar pitch binders for the production of metallurgical quality formed coke from anthracite fines or coke breeze

The effect of the type and the amount of hardeners, such as ammonium nitrate, ammonium carbonate and nitric acid on the molasses bonded briquettes prepared from anthracite fines or coke breeze were investigated. Amongst the hardener studied the best results were obtained with 2.5% ammonium nitrate hardener. The briquettes produced with this hardener were highly water resistant but not waterproof and their tensile strengths were not adequate to be used as a substitute for the metallurgical coke. Therefore, the briquettes were prepared with molasses containing 2.5% ammonium nitrate hardener and air blown coal tar pitch blended binder. When the blended binder was used for the production of anthracite fines or coke breeze briquettes, after curing at 200 °C for 2 h, they became waterproof and their tensile strengths were found to be sufficient to be used as a substitute for coke oven coke. The briquettes after curing could be directly charged into the blast furnace without carbonizing them at high carbonization temperatures. Since molasses and coal tar pitch, are relatively cheap and readily available materials, the process investigated could be economical way of producing high quality formed coke.     

Factors affecting the strength of formed coke made from lignite char

Char made from narrow size fractions of lignite in a fluidized bed was briquetted at 140 MPa with various binder tars produced from the lignite. The raw briquettes were cured in air at 200 °C and then carbonized, usually at 925 °C. The tensile strength of the resulting formed coke could be as much as three times that of the best metallurgical coke, or as low as 2–3 MPa, depending on the type of binder used, or even a factor of ten lower than this if the curing stage was omitted. Curing is thus a crucial stage. Distinct optima of binder percentage and char particle size were found, giving maximum briquette strengths (≈ 13 MPa). A corresponding ‘strength surface’ suggested four factors associated with weakness of a briquette. Binders produced by air-blowing rather than nitrogen-blowing gave stronger briquettes. Fluidized bed tar was greatly ‘improved’ in this way, but Gray-King tar only slightly so, probably because the former contained more generally reactive species. Cured-only briquettes were usually surprisingly strong and carbonization increased this strength ≈ 1.5 times. Curing is considered to ‘fix’ the binder; carbonization changes the chemical nature of the ‘cement’ between the char surfaces but does not appreciably alter its spatial distribution. The carbonized briquette thus has substantially the same structural flaws as were present in the cured state and so has a strength closely correlated with that achieved merely by curing.     

Investigation of resole, novalac and coal tar pitch blended binder for the production of metallurgical quality formed coke briquettes from coke breeze and anthracite

In order to reduce the cost and also enlarge the solid carbon source suitable for the formed coke production further investigations were conducted to produce formed coke using anthracite which can provide a new and relatively economic abundant raw material suitable for this purpose. The results indicated that, anthracite can also be used for the production of metallurgical quality formed coke, but the tensile strength of the anthracite formed coke were found to be comparatively lower than that of the coke breeze formed coke, 64.6 MPa, 73.2 MPa, respectively, when carbonized at 950 °C for 1 h, due to the decomposition of the volatiles that causes fissures, cracks and new pores. To produce anthracite briquettes of higher tensile strength, either anthracite of lower volatile matter should be used or it should be blended with coke breeze.     

Influence of mineralogy on the hydraulic properties of ladle slag

The present study is aimed at investigating the hydraulic characteristics of ladle furnace slag (LFS), under the pretence of using LFS as a cement substitute in certain applications. Furthermore, LFS has been considered as a possible activator in a blend containing 50% LFS, and 50% ground granulated blast furnace slag (GGBFS). Phases detected in LFS were quantified using Rietveld analysis. Calorimetric studies were performed at 20, 25 and 30 °C in order to calculate the apparent activation energy of hydration and thereby to suggest a kinetic model for the tested compositions within this temperature interval. In addition, compressive strength tests were performed on mortar prisms made with LFS, and LFS/GGBFS which had hydrated for 2, 7 and 28 days. Both compositions reached acceptable early strengths, (e.g. LFS, 33.1 MPa, and LFS/GGBFS, 17.9 MPa, after 2 days), but after 28 days hydration the blend was superior to neat LFS. Related apparent activation energies were determined using an Avrami–Erofeev model and gave E_a = 58 kJ/mol for neat LFS and E_a = 63 kJ/mol for the blend. The results imply that LFS or a LFS/GGBFS blend can be favourably used as supplement in binder applications such as binder in by-product metallurgical briquettes, which are used as recycle to the blast furnace or basic oxygen furnace depending on the specific briquette composition.     

A self-reduced intermediate product from iron and steel plants waste materials using a briquetting process

This study aims to investigate the possible solution for blast furnace flue dust which generates from the Egyptian Iron and Steel Company by forming self-reducing briquettes composed of flue dust and mill scale with different mass ratios, used in electric arc furnace to produce steel. The results indicated that the mechanical properties of the briquettes improved with increasing mill scale ratio in the mixture, whereas the reduction percentages decreased with decreasing temperatures. The addition of coke breeze fines to the briquette mixture (1 mill scale : 1 flue dust) improved the compressive strength of the produced briquette. XRD analysis and microscopic structure of briquette containing 11% coke reduced at 1100 °C for 2 h in isolated atmosphere, showed that the iron phase was predominate phase and the quantity of metallic iron increased.     

型煤型焦技术研究新进展

根据国内型煤型焦生产情况认为,应注重研究焦油、沥青类粘结剂的改性机理。为了避免型煤在炭化时软化变形和粘连,型煤预处理是非常重要的过程,预处理工艺及如何实现工业上预处理和炭化一体化是值得研究的课题。酚醛树脂作为粘结剂,固化后残炭多,强度大,而且只经低温预处理即可达到高炉用焦的要求,值得国内借鉴,今后的研究要立足如何降低酚醛树脂的成本。     

Thermal degradation of metallurgical coke

To understand the drastic deterioration of coke at the 3–5 m level above the tuyeres in the blast furnace, studies were made of the tensile strength in relation to the JIS drum strength, and measurements were made of the tensile strength of coke at high temperatures (maximum 2300 °C). Plastic deformation was observed above 2000 °C and this could be estimated from the microstrength and the porosity of coke. It was concluded that the factors affecting the resistivity to plastic deformation were the coke bonding between inerts and reactives and the existence of amorphous texture, and that the thermal degradation of the matrix strength must contribute, to some extent, to the drastic reduction in drum strength in the lower part of blast furnace.     

Phenolic resin binder for the production of metallurgical quality briquettes from coke breeze: Part III the effect of the type of acidic hardeners on the quality of the formed coke and the possibility to avoid the curing stage to produce metallurgical briquettes with enough strength

In order to avoid the curing stage in formed coke production, the effects of hardeners, on the tensile strength of the briquettes bonded with resole binders of F / P = 2.0 and N / P ratios ranging 0.1–0.5, were studied. The raw briquettes were produced by mixing the resole binders containing these hardeners, with the coke breeze. They were hardened at room temperature for 24 h and also at 200 °C for 2 h. The briquettes were also produced from the resole binders of the same N / P but containing no hardener, and cured at 200 °C for 2 h. The tensile strengths of the briquettes were measured. H₃PO₄ resulted in the briquettes having the lowest tensile strength under any conditions investigated. H₂SO₄ and p-TSA hardeners were found to be unsuitable for the aim of this investigation, because they could not fully harden the briquettes at room temperature. ATP resulted in the briquettes of the highest tensile strength of 52.13 MPa, with the resole binder of N / P = 0.1 after 24 h hardening at room temperature but resulted in briquettes of relatively lower tensile strength when the N / P ratio of resoles was increased. By blending ATP and p-TSA it became possible to produce formed coke with sufficient tensile strength by hardening them at room temperature.     

Properties and potential of formed cokes derived from two Turkish lignites by carbonization of binderless briquettes

Two high-sulphur Turkish lignites were briquetted at room temperature under pressures of 113 or 212 MPa and the briquettes were carbonized to 1158–1173 K over special heating cycles. The lower-rank lignite gave a formed coke of superior mechanical strength, lower porosity and higher sulphur content than typical blast furnace cokes. The formed coke produced from the higher-rank lignite briquettes had slightly poorer mechanical strength, lower porosity and much higher ash yield and sulphur content than conventional cokes. The products were considered attractive for use in non-ferrous metallurgy.     

型煤与焦粉型焦粘合剂的研究及应用

探讨了型煤粘合剂的粘结机理 ,介绍了几种主要粘合剂的分类 ,重点论述了WIN -1型民用与锅炉型煤粘合剂、WIN - 2超微粉造气型煤粘合剂及WIN - 3焦粉型焦粘合剂的研究和应用情况 ,利用这些粘合剂生产的锅炉型煤、造气型煤、焦粉型焦等产品均达到了应用要求     

焦粉型球的研制及工业中试

介绍了利用廉价的焦粉加入复合粘结剂生产焦粉型球代替煤气发生炉所用块焦的研制、工业中试和试烧过程。型球的配方合理 ,技术上可行 ,生产流程先进 ;生产的型球冷强度、热稳定性好 ,能满足人工煤气发生炉的制气工艺要求 ,生产的煤气组分及热值与块焦的基本相同 ,具有显著的经济效益     

Curing temperature effect on mechanical strength of smokeless fuel briquettes prepared with molasses

Environmental acceptable smokeless fuel briquettes have been prepared with a low-rank coal and olive stone as biomass. The binder chosen for this study was molasses which acts with different roles, as chemical and matrix type. The effect of the curing temperature on these briquettes has been studied by Fourier transform infrared spectroscopy, temperature programmed decomposition (TPD) followed on-line by mass spectrometry and optical microscopy. TPD experiments help to predict the final properties of the briquettes more clearly than infrared spectroscopy. The aliphatic structures and methoxy groups as well as the hydrogen bonds decrease during the curing. On the other hand, the carboxylic groups tend to be formed due to the oxidation produced by the effect of curing temperature. In addition, the briquettes cured at 200 °C, 2 h showed the highest mechanical strength. These curing conditions also produce waterproof briquettes due to the presence of carboxylic groups which contribute to the stabilisation of the briquettes because of the formation of hydrogen bonds.     

干化污泥型煤抗压强度的实验研究

利用微波干燥脱水污泥制备型煤粘结剂,与粉煤混合压制成型煤。通过正交试验考察成型压力、干化污泥含水率及添加比例对型煤抗压强度的影响。结果表明：微波干化的污泥型煤较粘土型煤的抗压强度大;成型压力、干化污泥含水率及添加比例均为型煤抗压强度的显著因素,各因素优化范围：成型压力为25～30MPa,干化污泥水分为40％左右,干化污泥添加比例为20％～30％。     

Plastic wastes, lube oils and carbochemical products as secondary feedstocks for blast-furnace coke production

Two plastic wastes (polyolefin-enriched and multicomponent), two lube oils (paraffinic and synthetic) and one coal-tar were assessed as individual and combined additives to coal blends for the production of blast furnace coke. The effects of adding 2 wt.% of these additives or their mixtures (50:50 w/w) on the coking capacity of coal, coking pressure and coke quality parameters were investigated. It was found that the two plastic wastes reduce fluidity, whereas the addition of oils and tar helps to partially restore the fluidity of the coal-plastic blend. From the co-carbonization of the coking blend with the different wastes in a movable wall oven of over 15 kg capacity, it was deduced that polyolefins have a detrimental effect on coking pressure. The addition of oils and tar to the coal-plastic blend has different modifying effects. Whereas paraffinic oil eliminated the high coking pressure caused by the polyolefins, polyol-ester oil had a weak reducing effect unlike coal-tar which had a strong enhancing effect. The compatibility of the oils/tar with plastics and coal and the beneficial influence of these combinations on coking pressure is discussed in relation to the miscibility of the plastic and the oily and bituminous additives, and the amount and composition of the volatile matter evolved from each additive during pyrolysis as evaluated by thermal analysis. Furthermore, it was found that coke reactivity towards CO₂ (CRI) and coke strength after reaction with CO₂ (CSR) are heavily dependent on the composition of the plastic waste, with polystyrene (PS) and polyethylene terephthalate (PET) having a clear negative effect. The porosity of the cokes obtained from blends containing plastic wastes is always higher, but the pores are smaller in size.     

Briquetting of Istanbul-Kemerburgaz lignite of Turkey

A lignite sample from the Kemerburgaz-Istanbul area was briquetted with or without binder material. Molasses and Şirnak (Turkey) asphaltite were used as binder materials at different ratios. The effects of the moisture content of the lignite and the concentration of the binder on briquette strength were examined at two different briquetting pressures, 150 and 200 MPa. Briquetting of lignite samples without binder material gave products with low strength and low water resistance. The maximum briquette strength was achieved with a lignite moisture content of 13% and an asphaltite concentration of 12% at a briquetting pressure of 200 MPa. The strongest briquettes obtained with lignite-molasses blends were achieved with a molasses concentration of 12% and a lignite moisture content of 8% at a briquetting pressure of 200 MPa.     

改性花生壳基型焦性状研究

采用六组不同粒级的神木粉煤为原料,质量分数1. 5%和2. 5%NaOH改性花生壳为粘结剂,通过干法冷压成型制备型煤,而后高温干馏制备改性花生壳基型焦。利用红外光谱仪表征其官能团结构,测定改性花生壳基型焦的抗压强度、跌落强度和机械强度等宏观性质。结果表明,神木煤粒度(3～1. 5) mm,质量分数2. 5%NaOH改性花生壳基型焦的性能强度更优,跌落强度98. 4%,抗压强度5 187. 15 N,抗碎强度与耐磨强度分别为82. 08%和17. 92%。NaOH浓度对型焦的性能强度影响不大。随着粉煤粒度减小,型焦宏观性能强度降低。神木煤粒度0. 425 mm,抗碎强度急剧降低至0,耐磨强度高达100%。改性花生壳基型焦红外谱线相对简单,出峰数目少,不同粒级神木煤型焦的红外谱峰峰型相似,出峰位置一致,但峰强弱略有差异。     

Examination of some effects of dry cooling on coke quality

A series of coals were carbonized, on the 250 kg scale under standardized conditions, to provide both dry-cooled and wet-quenched cokes which were subsequently subjected to reactivity and strength testing. The data from the tests of reactivity to CO₂ at ≈1000 °C support the view that dry coke cooling leads to lower reactivity, but examination of the porous structure in the pore size range > 5.45 μm and of the optical anisotropy of the coke carbon revealed no changes to account for this effect. Although the micum test indices were sometimes improved by dry coke cooling, the differences were not statistically significant. On the other hand, there was clear evidence of increased coke tensile strength. The effect of dry coke cooling on coke properties appears to be sufficient to exert some influence on the blast furnace coke rate and thereby on the economy of the dry-cooling process.     

Yttria stabilized zirconia formed by micro ceramic injection molding: Rheological properties and debinding effects on the sintered part

Micro Ceramic Injection Molding (μCIM) is a near net-shape process to produce smaller and intricate parts at a competitive cost. The application of nano-sized ceramic powder in μCIM has the advantages of fine grain size growth and good surface finish. However, the nano size effect causes agglomeration and low powder loadings, which result in defects during the μCIM process and in the sintered components. This study extensively investigated the debinding and sintering of yttria-stabilized zirconia (YSZ), as well as its rheological properties, using polypropylene (PP) as the primary binder and palm stearin as the secondary binder. 50 nm Yttria stabilized zirconia (YSZ) powders were mixed with palm stearin and PP at a powder loading of 37–43 vol%. The results of rheological studies showed that the feedstock had a dilatant flow characteristic and a viscosity of around 10–40 Pa s. Feedstock with 38 vol% powder loading had the lowest activation energy of 9.48 kJ/mol. The green part of the injected feedstock had flexural strength ranging from 13 to16 MPa, within which the feedstock with 43 vol% powder loading had the highest green density. Solvent debinding was carried out at three temperatures (50, 60, and 70 °C) using heptane. A large porous region was clearly identified at 70 °C compared with 50 °C. A debinding split furnace with argon gas was used to remove PP at 450 °C for 4 h. The debound samples did not shrink when 94%–98% of the binder system was removed. All debound samples sintered at 1350 °C and 41 vol% had the highest mechanical properties with hardness of 900 HV and a flexural strength of 400 MPa.