Process optimization for treatment of methyltin mercaptide effluents using modified semi-coke

The central composite process optimization was performed by response surface methodology technique using a design for the treatment of methyltin mercaptide with modified semi-coke. The semi-coke from the coal industry was suitably modified by treating it with phosphoric acid, with a thermal activation process. The objective of the process optimization is to reduce the chemical oxygen demand （COD） and NH4＋-N in the methyltin mercaptide industrial effluent. The process variables considered for process optimization are the semi-coke dosage, adsorption time and effluent pH. The optimized process conditions are identified to be a semi-coke dosage of 80 g/L, adsorption time of 90 min and a pH value of 8.34. The ANOVA results indicate that the adsorbent dosage and pH are the significant parameters, while the adsorption time is insignificant, possibly owing to the large range of adsorption time chosen. The textural characteristics of modified semi-coke were analyzed using scanning electron microscopy and nitrogen adsorption isotherm. The average BET surface area of modified semi-coke is estimated to be 915 mE/g, with the average pore volume of 0.71 cm3/g and a average pore diameter of 3.09 nm, with micropore volume contributing to 52.36%.

Investigation on activated semi-coke desulfurization

An activated semi coke with industrial scale size was prepared by high pressure hydrothermal chemistry activation, HNO 3 oxidation and calcination activation in proper order from Inner Mongolia Zhalainuoer semi coke, which is rich in resource and cheap in sale. SO 2 adsorption capacity on this activated semi coke was assessed in the fixed bed in the temperature range of 60—170℃, space velocity range of 500—1300 h -1 , SO 2 concentration of 1000—3000 ppmv, and N 2 as balance. The surface area, elemental and proximate analysis for both raw semi coke and activated semi cokes were measured. The experimental results showed that the activated semi coke has a high adsorption capacity for sulfur dioxide than the untreated semi coke. This may be the result of increase of surface area on activated semi coke and surface oxygen functional groups with basicity characteristics. Comparison to result of FTIR, it is known that group of —C—O—C? ?may be active center of SO 2 catalytic adsorption on activated semi coke.

Impact of impregnation pressure on desulfurization performance of Zn-based sorbents supported on semi-coke

High-pressure impregnation, a new preparation method for sorbents to remove H2S from hot coal gas, is introduced in this paper. Semi-coke （SC） and ZnO is selected as the support and active component of sorbent, respectively. The sorbent preparation process includes high-pressure impregnation, filtration, ovendry and calcination. The aim of this research is to primarily study the effects of the impregnation pressure on physical properties and desulfurization ability of the sorbent. The desulfurization experiment was carried out in a fixed-bed reactor at 500 ~C and a simulated coal gas used in this work was composed of CO （33 vol%）, H2 （39 vol%）, H2S （300 ppm in volume）, and N2 （balance）. Experimental results show that the pore structure of the SC support can be improved effectively and ZnO active component can be uniformly dispersed on the support, with the small particle size of 10-500 nm. Sorbents prepared using high-pressure impregnation have better desulfurization capacity and their active components have higher utilization rate. P20-ZnSC sorbent, obtained by high-pressure impregnation at 20 atm, has the best desulfurization ability with a sulfur capacity of 7.54 g S/100g sorbent and a breakthrough time of 44 h. Its desulfurization precision and efficiency of removing H2S from the middle temperature gases can reach 〈 1 ppm and 〉99.7%, respectively, before sorbent breakthrough.

Effects of ultrasound on the desulfurization performance of hot coal gas over Zn-Mn-Cu supported on semi-coke sorbent prepared by high-pressure impregnation method

Zn-Mn-Cu/SC（U） sorbent was hydrothermally synthesized by ultrasound-assisted high-pressure impregnation method with semi-coke（SC）as support and the mixed solution of zinc nitrate,manganese nitrate and copper nitrate as active component precursors.The desulfurization performances of hot coal gas on the prepared sorbent at a mid-temperature of 500°C were tested in fixed-bed reactor.Morphology and pore structure of the prepared sorbent were also characterized by TEM,N2adsorption/desorption isotherms and XRD.For comparison,the sorbent of Zn-Mn-Cu/SC prepared by conventional high-pressure impregnation was also evaluated and characterized in order to study the effects of ultrasound treatment.Zn-Mn-Cu/SC（U） sorbent prepared by high-pressure impregnation under ultrasound-assisted condition showed a better desulfurization performance than Zn-Mn-Cu/SC.It could remove H2 S from 1000×10-6m3/m3 to 0.1×10-6m3/m3 at 500°C and maintained for 12.5 h with the sulfur capacity of 7.74%,in which both the breakthrough time and sulfur capacity were about 32% and 51% higher than those of Zn-Mn-Cu/SC sorbent.The introduction of ultrasound during high-pressure impregnation process greatly improved the morphology and pore structure of the sorbent.The ultrasonic treatment made particle size of active components smaller and made them more evenly disperse on semi-coke support,which provided more opportunities to contact with H2S in coal-based gases.However,there were no any difference in compositions and existing forms of active components on the Zn-Mn-Cu/SC and Zn-Mn-Cu/SC（U） sorbents.

Combustion characteristics of Daqing oil shale and oil shale semi-cokes

Thermo-gravimetric-analysis(TGA) was used to analyze the combustion characteristics of an oil shale and semi-cokes prepared from it.The effect of prior pyrolysis and TGA heating rate on the combustion process was studied.Prior pyrolysis affects the initial temperature of mass loss and the ignition temperature.The ignition temperature increases as the volatile content of the sample decreases.TG/DTG curves obtained at different heating rates show that heating rate has little effect on ignition temperature.But the peak of combustion shifts to higher temperatures as the heating rate is increased.The Coats-Redfern integration method was employed to find the combustion-reaction kinetic parameters for the burning of oil shale and oil shale semi-coke.

Effects of process parameters on pore structure of semi-coke prepared by solid heat carrier with dry distillation

The semi-coke was prepared by solid heat carrier with dry distillation in single factor method. The pore structures of raw coal and semi-coke were characterized by Brunauer-Emmett-Teller (BET) and scanning electron microscope (SEM). The results show that the adsorption and desorption isotherm of semi-coke are not coincident. There was a wide pore distribution on the semi-coke, in which mesopores and micropores account for a considerable proportion. Also there are many more secondary pores. With the increase of the final temperature of heat carrier and constant temperature, as well as the decrease of volume ratio of coal and hot carrier reactor, specific surface area and pore volume of semi-coke increased rapidly first and then decreased and finally increased, along with the rapidly reduction of average pore size. SEM photos show that the surface of semi-coke becomes increasingly rough and glossy.

Characterization of semi-coke generated by coal-based direct reduction process of siderite

Solid wastes derived from metallurgical industries pose a significant threat to environment. The utilization and disposal of these solid wastes are the major concern in the world. Semi-coke generated in coal-based direct reduction process of iron ore is a by-product and its suitable utilization is not available so far. In order to handle it properly, the characteristics of this by-product were comprehensively investigated. A series of analysis methods were used to demonstrate its mineral compositions, petrography and physico-chemical properties. The results reveal that the semi-coke has poor washability. The fixed carbon content of semi-coke reaches 76.11% and the gross calorific value is 28.10 MJ/kg, both of which are similar to those of traditional sinter coke breeze. Also, semi-coke ash possesses lower content of SiO2, Al2O3, S and higher content of CaO and MgO, which could improve the strength of sinter ore when partially substituting for coke breeze in sintering. Semi-coke features well-development porous structure and higher reaction activity, which predicts that the sintering speed could be elevated to some extent when employing it as a partial replacement of coke breeze, so the studies further suggest that the potential adverse effect of the high reactivity on sintering process could be weakened by adequately coarsening the semi-coke's particle size.

Effect of Limestone on NO Emission during the Co-Combustion of Semi-Coke and Bituminous Coal

When semi-coke is co-combusted with bituminous coal with higher sulfur content in a circulating fluidized bed(CFB)boiler,the necessity of desulfurization in furnace increases.Meanwhile,limestone,which is a widely used desulfurizing agent,also has an effect on NO emission.In order to explore its effect during co-combustion,the combustion experiments were conducted in both a CFB test rig and a fixed bed reactor.The results show that blending semi-coke with bituminous coal will change the occurrence forms of nitrogen in the fuel and more fuel NO is released during the devolatilization stage.During the desulfurization process,CaO will be generated through the calcination reaction.It has catalytic effects on both the oxidation and reduction reactions of NO,and the catalytic strength in these two types of reactions decides the final effect on NO emission.For the blended fuel with 50%semi-coke and 50%bituminous coal(SC50BC50),the NO emission initially increases and then decreases as the Ca/S molar ratio increases from 0 to 4 at 900℃.Compared to the situation of burning semi-coke alone,semi-coke in the blended fuel has more opportunities to contact with CaO under the same Ca/S molar ratio,leading to the heterogeneous reduction reaction of NO enhanced.As the combustion temperature increases from 800℃ to 1000℃,the effect of limestone on NO emission will change from promotion to inhibition.This is because the higher combustion temperature can intensify not only the catalytic reduction of NO precursors in the dense-phase region,but also the reaction between NO and unburnt char in the dilute-phase region in the CFB.Besides,the lower O_(2) concentration in the atmosphere is also favorable for enhancing the catalytic effect of CaO on the NO-char reduction reaction for semi-coke and SC50BC50,so the conversion of fuel-N/NO will be inhibited compared with the cases without limestone.The achievements of this study are beneficial for the coordinated control of NOx and SO_(2) during the co-combustion of semi-coke and bituminous coal.

Synthesis of biochar/clay mineral nanocomposites using oil shale semi-coke waste for removal of organic pollutants

Due to the poor surface/interfacial interaction and the large gaps in the size and microstructure between biomass and clay mineral,it was difficult to adjust the structure and performance of biochar/clay mineral composites at the molecular level.Herein,oil shale semi-coke composed of multi-minerals and organic matters was used as a promising precursor to prepare biochar/clay mineral nanocomposites via phosphoric acid-assisted hydrothermal treatment followed by KOH activation for removal of organic pollutants from aqueous solution.The results revealed that the nanocomposites presented well-defined sheet-like morphology,and the carbon species uniformly anchored on the surface of clay minerals.With the changes in the pore structure,surface charge and functional groups after two-step modification,the nanocomposites exhibited much better adsorption property toward organic pollutants than the raw oil shale semi-coke,and the maximum adsorption capacities of methylene blue,methyl violet,tetracycline,and malachite green were 165.30 mg g^(−1),159.02 mg g^(−1),145.89 mg g^(−1),and 2137.36 mg g^(−1),respectively.The adsorption mechanisms involved electrostatic attraction,π-πstacking and hydrogen bonds.After five consecutive adsorption-desorption,there was no obvious decrease in the adsorption capacity of malachite green,exhibiting good cyclic regeneration performance.It is expected to provide a feasible strategy for the preparation of biochar/clay mineral nanocomposites with the excellent adsorption performances for removal of organic pollutants based on full-component resource utilization of oil shale semi-coke.

Mercury oxidation and adsorption characteristics of potassium permanganate modified lignite semi-coke

The adsorption characteristics of virgin and potassium permanganate modified lignite semi-coke （SC） for gaseous Hg were investigated in an attempt to produce more effective and lower price adsorbents for the control of elemental mercury emission. Brunauer-Emmett- Teller （BET） measurements, X-ray powder diffraction （XRD） and X-ray photoelectron spectroscopy （XPS） were used to analyze the surface physical and chemical properties of SC, Mn-SC and Mn-H-SC before and after mercury adsorption. The results indicated that potassium permanganate modification had significant influence on the properties of semi-coke, such as the specific surface area, pore structure and surface chemical functional groups. The mercury adsorption efficiency of modified semi-coke was lower than that of SC at low temperature, but much higher at high temperature. Amorphous Mn7＋, Mn6＋ and Mn4＋ on the surface of Mn-SC and Mn-H-SC were the active sites for oxidation and adsorption of gaseous Hg~, which oxidized the elemental mercury into Hg2＋ and captured it. Thermal treatment reduced the average oxidation degree of Mn2＋ on the surface of Mn-SC from 3.80 to 3.46. However, due to the formation of amorphous MnOx, the surface oxidation active sites for gaseous Hg0 increased, which gave Mn-H-SC higher mercury adsorption efficiency than that of Mn-SC at high temperature.

Experimental Study on Preheated Combustion of Pulverized Semi-coke

In a test rig,pulverized semi-coke was preheated to 850℃in a circulating fluidized bed(CFB)and then cornbusted at 1100℃in a down-fired combustor(DFC).Experiments were conducted to reveal the effects of three secondary air nozzle cases(co-axial jet,top circular jet and wall circular jet)on the NO emission.The results show that the optimized secondary air nozzle can reduce NO emission.O_2 concentration profile is the major factor affecting NO generation and emission,which is led by the secondary air nozzle.The lower O_2 concentration led to the generation of lower initial NO.The NO emission at the exit of the DFC was reduced from 189 to 92mg/m^3(@6%O_2)with the decrease of initial generation.The peak of NO at 100 mm below the nozzle should be attributed to the oxidization of NH_3 in the syngas,rather than the oxidization of fuel-N in the char.The low and well-distributed O_2 concentration contributes to the reduction of initial NO,which helps to reduce the NO emission.The combustion effieiencies of the eases of the co-axial jet,the top circular jet,and the wall circular jet are97.88%,98.94%and 98.74%,respectively.

Experimental Investigation for Co-Combustion Characteristics of Semi-Coke and Bituminous Coal in a 3 MWth Tangential Combustion Facility

An experimental investigation was conducted in a 3 MW pilot-scale tangential combustion facility to explore the co-combustion characteristics of bituminous coal mixed with semi-coke.The thermal gravimetric analyzer(TGA)was used to obtained fuel thermal analysis.The results presented effects of semi-coke blending ratio(BR)on average furnace temperature,ignition temperature,NO emission and combustion efficiency.The excess air coefficient in main combustion sections and outlet were fixed at 0.85 and 1.2 while BR increased from 0%to 50 wt.%.The temperature profiles of combustion decreases along the height of furnace while average furnace temperature fluctuates slightly with an increasing BR.The concentration of NO has an increasing tendency with the increasing of BR.The ignition temperature obtained from TGA measurement agreed well with experiment result.In addition,combustion efficiency was not sensitive to BR and decreased slightly with the increasing BR.

Experimental and Numerical Study on Co-combustion Behaviors and NO_(x) Emission Characteristics of Semi-coke and Coal in a Tangentially Fired Utility Boiler

The utilization of powdery semi-coke as a power fuel in pulverized coal-fired power plants has become a new and potential technique to consume the excess powdery semi-coke.The characteristic of low volatile results in poor combustion performance and high NO_(x) emission,and to co-fire with bituminous coal is a practical strategy to address this problem.However,the co-combustion characteristics and the inherent interaction between semi-coke and coal remain insufficiently understood.In addition,the influences of secondary air arrangement,the boiler operation load,and the fuel type on co-combustion process are still unclear,which is urgent to be further explored.In the present study,experiments and numerical simulations were jointly utilized to inquire into the co-combustion behaviors and NO_(x) emission features of semi-coke and coal.The results demonstrated that the"out-furnace method"was a suitable choice for small-capacity boiler when the proportion of semi-coke was 33%,due to the limited combinations of the semi-coke injection position.It was recommended that semi-coke was preferred to be injected from the middle layers of the furnace under the"in-furnace method"to improve the overall co-combustion performance.The critical value of the separated over fire air ratio in this study was 27.5%,over which a slight drop of carbon content in fly ash could come about.Moreover,the elevation in the proportion of separated over fire air gave rise to the significant decline of NO_(x) concentration.The constricted secondary air arrangement was preferred to be employed due to the high boiler efficiency.The separated over fire air and the surrounding air needed to maintain a wide-open degree to prevent the increase of NO_(x) emissions and the coking of nozzles.For the load reduction regulation method adopted in this study,the NO_(x) concentration first rose and then dropped,while the burnout ratio decreased obviously as the operation load was reduced.Different combinations of coal and semi-coke generated significant influences on co-combustion behaviors within the furnace.The NO_(x )generated by high-volatile fuel (bituminous coal) combustion was mainly affected by volatile-N,while the NO_(x )generated by low-volatile fuel (semi-coke) was mainly impacted by char-N.This study is of guiding significance for the efficient and clean utilization and beneficial to the large-scale application of powder semi-coke in power plants.

Experimental research on semi-coke for blast furnace injection

The combustion properties and grindability of Shenmu low-rank coal(SM)and its four different semi-cokes were studied by the self-designed equipment and Hardgrove method.The four semi-cokes were obtained under the pyrolysis temperature of 400,500,600 and 700℃,named as SM-400,SM-500,SM-600 and SM-700,respectively.The analyses of nitrogen adsorp-tion,Fourier-transform infrared spectroscopy(FTIR)spectra and Raman spectra were carried out to explain the change in combustion ratio and grindability.The result showed that the specific surface area of samples had an essential effect on the combustion ratio of SM-400 and SM-500.Meanwhile,the grindability depended on the strength of coal matrix,and the augment of pore amounts would increase the grindability.The functional groups and graphitization degree of the same sam-ple were identical with the combustion ratio.With the pyrolysis upgrading temperature increasing,the combustion ratio of sample decreased,corresponding to the decrease in the benzene ring and the increase in graphitization degree.In addition,the thermogravimetric analysis was carried out,and the result was compared against what was shown in the data of com-bustion ratio.For pulverized coal injection,the combustion ratio was more intuitive and more accurate than combustibility.

Comparison of semi-coke with traditional pulverized coal injection and iron ore sintering fuels based on chemical structure and combustion behavior

Substantial semi-coke has been produced through the industrialized low-temperature pyrolysis process,which has great potential as an alternative fuel for pulverized coal injection(PCI)and iron ore sintering.X-ray diffraction,Raman spectroscope,and thermal analysis were used to compare the carbon chemical structure and combustion reactivity of semi-coke,pulverized coal,and coke breeze.The results show that the average volatile matter content in 46 types of semi-cokes is 8.94 wt.%.The fluctuation range of the characteristic parameters of the semi-coke chemical structure is d_(002)=(0.352–0.379)nm and A_(D1)/A_(G)=(2.51–7.92),while the fluctuation range of the characteristic parameters of pulverized coal is d_(002)=(0.348–0.373)nm and A_(D1)/A_(G)=(1.71–9.03)(where d_(002)means the interlayer spacing between the aromatic planes,and A_(D1)/A_(G)is an index that characterizes the degree of disorder of the char structure through the area ratio of the defect peak band D1 to the perfect graphite peak band G);the overlap between these ranges is relatively high.Contrarily,the fluctuation range of the characteristic parameters of coke breeze is d_(002)=(0.343–0.350)nm and A_(D1)/A_(G)=(0.75–2.51),which is markedly different from that of semi-coke.Semi-coke combustion reactivity is close to that of pulverized coal,but considerably better than that of coke breeze.In terms of chemical structure and combustion reactivity,semi-coke can be used as an alternative fuel for PCI;however,when used for sintering alternative fuel,matching of the heat supply and demand in the later sintering stage must be scrupulously analyzed.

Effect of oil shale semi-coke on deposit mineralogy and morphology in the flue path of a CFB burning Zhundong lignite

The effect of oil shale semi-coke(SC)on the mineralogy and morphology of the ash deposited on probes situated in the flue path of a circulating fluidized bed(CFB)which burns Zhundong lignite(ZD)was investigated.10 wt%or 20 wt%SC was added to ZD,which were then combusted in the CFB furnace at 950℃.Two probes with vertical and horizontal orientations were installed in the flue duct to simulate ash deposition.Both windward and leeward ash deposits on probes(P_(1)W,P_(1)L,P_(2)W and P_(2)L)were analyzed by using a scanning electron microscopy with energy dispersive X-ray(SEM-EDX),X-ray diffraction(XRD),an inductively coupled plasma optical emission spectrometry ICP-OES,and a particle size analyzer.When ZD was burned alone,the P1W deposit was comprised of agglomerates(<30µm)enriched in CaSO_(4)and Na_(2)SiO_(3),incurring significant sintering.The P1L and P2W deposits,however,were of both discrete and agglomerated particles in similar mineral phases but with coarser sizes.The P_(2)L deposit was mainly fine ash particles where Na_(2)SiO_(3)and Na_(2)SO_(4)were absent.As SC was added,the agglomerates in both P1W and P1L decreased.Moreover,SiO_(2)and Ca/Na aluminosilicates dominated the mineral phases whereas Na_(2)SiO_(3)and Na_(2)SO_(4)disappeared,showing a decrease in deposit stickiness.Likewise,the P2W deposit was found less spread on the probe,decreasing its deposition propensity.Na-bearing minerals turned into(Na,K)(Si_(3)Al)O_(8)and(Ca,Na)(Si,Al)4O8 in the P_(2)W deposit.Moreover,Na in the deposits decreased from 32 mg/g to less than 15 mg/g as SC presented.The addition of SC would therefore help alleviate the propensity of ash deposition in the flue path in the CFB combustion of ZD.

燃煤锅炉改燃兰炭燃烧工艺及效益分析

兰炭因热值高、硫含量低的特点被广泛应用于散煤替代,燃煤锅炉改燃兰炭是实现资源合理利用、降低污染物排放和改善企业经济效益的有效途径。以河北某循环流化床锅炉改燃兰炭工程为例,燃烧系统采用掺烧灰渣的方法,解决改燃后机械未完全燃烧导致损失大和物料循环不稳定问题,确定了兰炭和灰渣的最佳掺混比为9∶1;配风系统采用控制总量并降低一次风率的方法,解决兰炭着火困难的问题,确定了最佳一次风比例为55%;换热系统采用增加锅炉尾部受热面的方法,解决因燃料热值提升较大产生的蒸汽超温和锅炉效率下降问题。改燃扩容后锅炉烟尘、SO2和NOx排放分别比原锅炉降低了73%、94%和55%,以原锅炉35 t/h的额定功率运行,每小时节约燃料成本5.51%,产吨蒸汽所需燃料成本降低6.47元。

煤制兰炭过程中挥发性有机污染物和臭氧协同处理机理

为探究低温等离子体联合催化剂载体协同处理煤制兰炭过程中产生的挥发性有机污染物及臭氧,以二甲苯作为目标污染物,选取γ-氧化铝小球为催化剂载体,考察功率、氧通量、二甲苯初始浓度、催化剂载体用量等因素对挥发性有机污染物和臭氧协同处理效果的影响。结果表明:低温等离子体放电功率越大,二甲苯的脱除效果越好;在放电功率为70 W、氧通量为15%、初始浓度为600×10^(-6)时,二甲苯的去除率为64.41%,此时臭氧的产生量为125.21×10^(-6),综合考量在该性能下的协同处理效率最高;在最优低温等离子体性能的条件下,γ-氧化铝载体粒径越小,二甲苯的去除效率越高,协同处理效果最佳,二甲苯总去除率最高可达73.93%,臭氧抑制率最高为66.45%。γ-氧化铝载体对低温等离子体协同处理挥发性有机污染物与臭氧具有一定的促进作用。研究成果可为协同处理挥发性有机污染物提供有效的参考。

不同有机肥对土壤及核桃果实品质的影响

为探究“辽宁1号”核桃较适宜的有机肥,在河北省隆尧县红沙峪生态农业科技有限公司核桃园以10年生“辽宁1号”核桃树为试验材料,利用半焦肥、鸡粪及生物菌肥3种有机肥进行施肥处理,检测不同有机肥对土壤性状、核桃产量和品质的影响。结果表明,生物菌肥(2.5 kg/株)能显著提高种仁黄酮含量;鸡粪(40 kg/株)能显著提高种仁Fe、Zn含量以及土壤速效磷、速效钾含量;5.0 kg/株半焦肥能显著提高种仁多酚、土壤有机质含量;10.0 kg/株半焦肥施肥能显著提高青果的横径,坚果的单果质量、纵径、横径、侧径,种仁的脂肪、K、Ca、Mn、Cu含量以及土壤全磷含量。10.0 kg/株半焦肥在相关果实品质方面的综合效果最好,而5.0 kg/株半焦肥的经济效益最高。

硅铁冶炼用兰炭的调控制备与工业应用试验

介绍了硅铁冶炼用兰炭的调控制备方法,考察了依据调控制备方法生产的兰炭在硅铁冶炼中的应用,通过对调控制备兰炭的质量检测和其入硅铁炉后的冶炼指标进行追踪分析,证实了调控制备方法的可行性。试验结果表明:以优选原煤、调整干馏工艺参数和入炉还原剂再优化为手段的调控制备方法可以稳定兰炭的质量,并有效降低硅铁冶炼电耗;通过对原煤热解兰炭的性能评估可预测其工业兰炭的性能,从而优选出可生产适宜硅铁冶炼用兰炭的原煤;通过优选原煤和调控干馏炉参数可生产出成分和性质稳定的高性能硅铁冶炼用兰炭。