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.

Effect of impregnation methods on sorbents made from lignite for desulfurization at middle temperature

With lignite after vacuum drying as the raw material,a series of Zn-based sorbents were prepared by static impregnation,ultrasonic-assisted impregnation,bubbling-assisted impregnation and high-pressure impregnation.The physical properties and the desulfurization performances of Zn-based sorbents were studied systematically by XRD,BET,AAS characterization techniques and the fixed-bed desulfurization evaluation apparatus.The sorbents obtained by high-pressure impregnation method have a larger specific surface area,pore volume and pore diameter comparing with other methods,which is conducive to the sulfidation reaction of hydrogen sulfide gas in the sorbent.The effects of pressure during the high-pressure impregnation and concentration of Zn(NO3)2 precursor solution on the sorbents properties and desulfurization behavior were investigated.The higher the impregnation pressure and the concentration of impregnation solution are,the greater the amount of the active components are uploaded.However,overhigh impregnation pressure can cause collapse and blocking of the carrier pore.The optimal operating condition of high-pressure impregnation method for preparing the sorbents was the impregnation pressure of 20 atm and the solution concentration of 41%.Under that condition,the sorbent had the best desulfurization ability with a sulfur capacity of 13.94 gS/100 gsorbent and a breakthrough time of 54 h.Its desulfurization precision and efficiency of removing H2S before sorbent breakthrough from the middle temperature gases of 400℃ can reach【5 ppm and】99%,respectively.Sorbents could be regenerated under the condition of 1 vol%O2,20 vol% H2O,0.5 vol% NH3,and N2balance gas.The regenerated sorbent could be used for repeated absorption of H2S with a slight decrease in desulfurization effect.

High-temperature H_2S Removal with Calcium-based Sorbent

The H2S removal characteristics of Taxada lime tinder the high temperature of 600-900℃ have been investigated. The test results indicated that this kind of sorbent almost was inert to H2S When temperature lowered down to 600℃,while its reactivity increased with increased temperature and the equilibrium conversion reached up to over 60% at temperatLlre of 900℃.However, side reactions of H2S in conjunction with high-temperature decomposition and mineral catalysis to elemental sulfur and sulfur dioxide were testified.

Desulfurization kinetics of ZnO sorbent loaded on semi-coke support for hot coal gas

Zn-based sorbent （Z20SC） prepared through semi-coke support in 20 wt% zinc nitrate solution by high-pressure impregnation presents an excellent desulfurization capacity in hot coal gas,in which H2 S can not be nearly detected in the outlet gas before 20 h breakthrough time.The effects of the main operational conditions and the particle size of Z20SC sorbent on its desulfurization performances sorbent were investigated in a fixed-bed reactor and the desulfurization kinetics of Z20SC sorbent removing H2 S from hot coal gas was calculated based on experimental data.Results showed that the conversion of Z20SC sorbent desulfurization reaction increased with the decrease of the particle size of the sorbent and the increases of gas volumetric flow rate,reaction temperature and H 2 S content in inlet gas.Z20SC sorbent obtained from hydrothermal synthesis by high-pressure impregnation possessed much larger surface area and pore volume than semi-coke support,and they were significantly reduced after the desulfurization reaction.The equivalent grain model was reasonably used to analyze experimental data,in which k s=4.382×10-3 exp（-8.270×103/RgT） and Dep=1.262×10-4exp（1.522×104/RgT）.It suggests that the desulfurization reaction of the Z20SC sorbent is mainly controlled by the chemical reaction in the initial stage and later by the diffusion through the reacted sorbent layer.

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.

Study on Zn_2SiO_4 Formation Kinetics and Activity Stability of Desulfurization Sorbent

A new industrial S Zorb sorbent(Ni/Zn O-P) was prepared by using the spray drying technique. The other two traditional sorbents(Ni/Zn O-M and Ni/Zn O-H) were prepared in exactly the same way except the use of different silica-alumina binder matrices. The XRD, Rietveld quantitative phase analysis, BET, and laser particle size analysis were employed to characterize their physico-chemical properties. The deactivation mechanism and desulfurization kinetics of sorbent was investigated on a water vapor aging treatment device. It was shown that both the water vapor pressure and reaction temperature significantly could influence the formation rate of inactive Zn2 Si O4, which could decrease the sulfur storage capacity of sorbents. The Zn2 Si O4 content profiles could be fitted into the zero order equation, from which the apparent rate constant k and the activation energy E a were calculated. The matrix P greatly raised the E a of Zn2 Si O4 formation due to the less bridged hydroxyl silanol groups on its surface, which accounted for the high stability of Ni/Zn O-P. The desulfurization performance of the fresh and aged sorbents showed that the overall average sulfur conversion of Ni/Zn O-P(aged) was 92%, which was close to that of fresh sorbents(95%), and was higher than that of Ni/Zn O-M(aged)(86%) and Ni/Zn O-H(aged)(90%). Based on these findings, the application of Ni/Zn O-P can greatly improve the long-term running stability of the industrial unit.

Effect of Calcium Oxide Additive on the Performance of Iron Oxide Sorbent for High-Temperature Coal Gas Desulfurization

The effect of calcium oxide additive in iron oxide sorbent for hot gas desulfurization was investigated by XRD and TPR techniques.XRD characterization showed that CaO was highly dispersed after the calcination of sorbents.Calcium sulfate formed in the desulfurization was decomposed and regenerated to CaO by reacting with CO before the next sulfidation process.Calcium participated in every sulfidation/regeneration cycle and contributed to the enhancement of sulfur capacity.The TPR results showed that the reduction temperature of the sorbent increased with the increase of the content of calcium.Calcium played a role of retarding reduction.Therefore,the addition of calcium oxide additive will benefit the utilization of iron oxide sorbent in strongly reducing atmospheres.

Effect of binder on the properties of iron oxide sorbent for hot gas desulfurization

The most difficult problem in hot gas desulfurization in Integrated Coal Gasification Combined Cycle （IGCC） is the pulverization of sulfur removal sorbents.Appropriate binders for hot gas sulfur removal sorbents can solve the pulverization problem.In this paper,six sorbents with binders of different argillaceous minerals were prepared by mechanical mixing method.Desulfurization behavior for hot gas desulfurization sorbents was investigated in a fixed-bed reactor.Result showed that sorbent NTKW2 with binder of clay had a better sulfidation performance.NTKW2 had a more stable performance than other sorbents in the continuous sulfidation-regeneration cycles.Sulfur capacity of sorbent remained the same in each cycle.The desulfurization efficiency and mechanical strength of NTKW2 were the best among the tested sorbents.The behavior of NTKW2 at different temperatures showed different performances,and the best reaction temperature was 550 ℃.Higher heat stability,sulfur capacity and desulfurization efficiency were found on NTKW2 in six continuous sulfidation-regeneration cycles.

Experimental study on SO_2 recovery using a sodium-zinc sorbent based flue gas desulfurization technology

A sodium–zinc sorbent based flue gas desulfurization technology(Na–Zn-FGD) was proposed based on the experiments and analyses of the thermal decomposition characteristics of Ca SO3 and Zn SO3·2.5H2 O, the waste products of calcium-based semi-dry and zinc-based flue gas desulfurization(Ca–SD-FGD and Zn–SD-FGD) technologies, respectively. It was found that Zn SO3·2.5H2 O first lost crystal H2 O at 100 °C and then decomposed into SO2 and solid Zn O at 260 °C in the air, while Ca SO3 is oxidized at 450 °C before it decomposed in the air. The experimental results confirm that Zn–SD-FGD technology is good for SO2 removal and recycling, but with problem in clogging and high operational cost. The proposed Na–Zn-FGD is clogging proof, and more cost-effective. In the new process, Na2CO3 is used to generate Na2SO3 for SO2absorption, and the intermediate product Na HSO3 reacts with Zn O powders, producing Zn SO3·2.5H2 O precipitate and Na2SO3 solution. The Na2SO3 solution is clogging proof, which is re-used for SO2 absorption. By thermal decomposition of Zn SO3·2.5H2 O, Zn O is re-generated and SO2 with high purity is co-produced as well. The cycle consumes some amount of raw material Na2CO3 and a small amount of Zn O only. The newly proposed FGD technology could be a substitute of the traditional semi-dry FGD technologies.

Research on improvement in Zn-based sorbent for hot gas desulfurization

Two Zn-based sorbents, L-991 and L-992 used for hot gas desulfurization (HGD) were introduced. Zn/Ti ratio of the two sorbent was 1:1 and 2:3 resptively and a certain proportion of Cu and Mn metal oxide were added into L-992, which provided better performance than L-991 in aspects of suitable work temperature, sulfur capacity and agglomeration on the surface of sorbent particles. The evaluation tests were done on both sorbents include multi cycles tests. ARD and SEM analysis were done on fresh and post tests sorbent. During continuous sulfidation/regeneration, the H2S concentra- tion can be reduced from about 10 g/m3 to less than 20 mg/m3, the H2S removal effi- ciency >99 %.

Influence of Carbon Content on S Zorb Sorbent Activity

The reaction activity of S Zorb sorbents with different sulfur contents was investigated, and the structure and composition of carbon-containing sorbents were characterized by XRD, FT-IR and TG-MS in order to delve into the kind and morphology of carbon on the sorbent. Test results have revealed that coke could be deposited on the S Zorb sorbent during the operating process, and the coke content was an important factor influencing the reaction performance of the S Zorb sorbent. Retention of a definite amount of coke on the sorbent while securing the desulfurization activity of the S Zorb sorbent would be conducive to the reduction of octane loss of reaction product.

Effect of impurities on desulfurization properties of limestone during coal gasification

In order to understand the function of calcium based sorbents on desulfurization during coal gasification and the effect of impurities on it, a series of tests using three different limestones and four kinds of different sodium salts and four kinds different chlorides were conducted by X ray diffraction and X ray photoelectron spectroscopy techniques. The structure of precursory compounds and pretreatment materials were examined by XRD. The binding energy and relative contents of sulfur, calcium and carbon, which exist in different forms in the residues after coal gasification, were measured by means of XPS. The existing forms of sulfur and calcium vary with impurities in limestone. Sodium or chloride play a promotive role on limestone desulfurization, but this promotion is affected by the chemical environment.

Reaction mechanism of arsenic capture by a calcium-based sorbent during the combustion of arsenic-contaminated biomass: A pilot-scale experience

Large quantities of contaminated biomass due to phytoremediation were disposed through combustion in low-income rural regions of China.This process provided a solution to reduce waste volume and disposal cost.Pilot-scale combustion trials were conducted for in site disposal at phytoremediation sites.The reaction mechanism of arsenic capture during pilot-scale combustion should be determined to control the arsenic emission in flue gas.This study investigated three Pteris vittata L.biomass with a disposal capacity of 600 kg/d and different arsenic concentrations from three sites in China.The arsenic concentration in flue gas was greater than that of the national standard in the trial with no emission control,and the arsenic concentration in biomass was 486 mg/kg.CaO addition notably reduced arsenic emission in flue gas,and absorption was efficient when CaO was mixed with biomass at 10% of the total weight.For the trial with 10% CaO addition,arsenic recovery from ash reached 76%,which is an ~8-fold increase compared with the control.Synchrotron radiation analysis confirmed that calcium arsenate is the dominant reaction product.

New nanostructured sorbents for desulfurization of natural gas

Desulfurization of natural gas is achieved commercially by absorption with liquid amine solutions. Adsorption technology could potentially replace the solvent extraction process, particularly for the emerging shale gas wells with production rates that are generally lower than that from the large conventional reservoirs, if a superior adsorbent （sorbent） is developed. In this review, we focus our discussion on three types of sorbents： metal- oxide based sorbents, Cu/Ag-based and other commercial sorbents, and amine-grafted silicas. The advantages and disadvantages of each type are analyzed. Possible approaches for future developments to further improve these sorbents are suggested, particularly for the most promising amine-grafted silicas.

Resource utilization of flue gas calcium-based desulfurization ash:a comprehensive review

Calcium-based desulfurization ash(CDA)is mainly produced in dry and semi-dry flue gas desulfurization processes.The property of CDA is extremely unstable because its main component,calcium sulfite,makes it difficult to be directly applied to the field of building materials.The modification of desulfurization ash can be realized by high-temperature oxidation and wet oxidation.After modification,CDA can be widely used in building materials.Hydrothermal oxidation has broad development prospects because it can complete the oxidation of CDA and the removal of impurity elements at the same time.CDA can be used to prepare high value-added products of calcium sulfate whiskers and ecological rubber fillers.

Effects of steam on CO2 absorption ability of calcium-based sorbent modified by peanut husk ash

The CO_2 absorption ability of synthetic calcium-based sorbent modified by peanut husk ash (PHA) was tested by Thermal Gravimetric Analyzer (TGA), and the effects of steam and calcination temperature were investigated. The PHA composition was analyzed by X-Ray Fluorescence (XRF), the apparent morphology was characterized by scanning electron microscope (SEM), and the phases of the sorbent before and after calcination were examined by X-ray diffraction (XRD). The addition of PHA effectively improved the cyclic stability of the calcium-based sorbent. The optimal molar ratio of SiO_2 in PHA to CaO was around 0.07. Steam had positive effect on keeping porosity of the sorbent at the chemical reaction stage, and improved its CO_2 absorption ability. Steam also reduced the diffusion resistance of the product layer, and depressed the influence of high temperature calcination. It was also found that the steam hydration after calcination was an effective way to recover the absorption ability of the sorbent, while the hydration duration of 10 min was enough.

高温煤气铁系脱硫剂的研究

高温煤气脱硫净化是目前先进洁净煤利用技术之一 ,但是以前高温煤气脱硫剂在多次硫化再生循环过程中出现粉化 ,妨碍脱硫剂进一步使用 .本研究选择钢厂赤泥作为脱硫剂原料 ,添加不同活性组分和防粉化结构助剂 ,制备了氧化铁基高温煤气脱硫剂 .经过 1 0次硫化 /再生循环实验 .结果表明 :1 0次循环累计 1 96.98% ,再生后脱硫活性不发生变化 ,具有较高和较稳定的脱硫活性 .再生后脱硫剂的机械强度高于新鲜样品 ,在使用过程中没有出现粉化现象 ,这为氧化铁基高温煤气脱硫剂的工业化研究提供了可靠的依据 .

半干半湿法烟气脱硫技术研究

在实验的基础上，分析了半干半湿法烟气脱硫技术的优点。根据影响该技术脱硫效率的主要因素，通过实验，较系统地研究了温距与喷嘴布局、入塔烟温、Ｃａ／Ｓ 摩尔比、脱硫灰循环利用等对脱硫效率的影响，并对脱硫灰制砖的成分配制也进行了讨论。结果表明，在整体Ｃａ／Ｓ 摩尔比为１－５ ～１－７ 时，该技术工艺可以达到８０ ％

燃煤炉预混—喷钙二段脱硫技术研究

文章指出了煤燃烧高温脱硫3方面难点:①石灰石分解速率低于煤燃烧时硫析出速率;②脱硫产物在CaSO_41200℃以上再分解;③CaO颗粒高温严重烧结。对此,提出二段脱硫工艺,即一部分添加剂与煤预混进行料层脱硫,另一部分喷入炉内捕捉烟气中硫。建立了10t/h链条炉二段脱硫示范装置。试验和运行结果表明锅炉除尘器前脱硫率达到70％以上,除尘器后,烟气经半干法处理可达到80％～90％。

高活性吸收剂脱硫和脱氮实验及机理研究

为了实现同时脱硫、脱氮,制备了以粉煤灰、石灰、添加剂为原料、具有氧化能力的高活性吸收剂。在固定床、管道喷射进行了同时脱硫、脱氮实验,研究了影响吸收剂脱硫、脱氮效率的若干因素。探讨了高活性吸收剂脱硫、脱氮的机理。在Ca/(S+N)为1.2时,SO2和NOX的脱除效率分别为86%和64%。产生的废物为干粉状。最佳的实验温度为55℃,湿度为5%。与传统的干法FGD相比,该工艺具有费用低、设备简单、废物易于处置等优点,可为工业化应用提供有益的参考。