• Applied Chemistry for Engineering
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• v.26 no.2
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• pp.193-198
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• 2015

Ceria supported on various commercial $TiO_2$ catalysts were prepared by wet-impregnation method. We confirmed that the correlation between physicochemical properties of $TiO_2$ supports and SCR activities. Physicochemical properties of the various $TiO_2$ were evaluated using X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area, X-ray photoelectron spectroscopy (XPS), and pH analysis. Ce/Ti catalyst exhibited different SCR activities with respect to physicochemical properties of $TiO_2$. An excellent activity was obtained as the surface area of $TiO_2$ increased. In the case of CeOx surface density, the excellent activity in a range of $2.5{\sim}14.5CeOx/nm^2$ was achieved and the activity tended to decrease above $14.5CeOx/nm^2$. The O/Ti mole ratio of $TiO_2$ in the range of 1.32 to 1.79 showed an excellent SCR activity. It was also confirmed that the pH of the $TiO_2$ has no effects on the SCR activity. In order to achieve excellent SCR activities, ceria oxide should be supported on $TiO_2$ possessing a high specific surface area and certain O/Ti mole ratio. In addition, the catalyst with the low CeOx surface density resulted from the high dispersed ceria oxide should be prepared.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.979-984
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• 2001

As a preceding process for developing design technology and establishing operation technology, the design procedure of the SCR(Selective Catalytic Reduction) pilot plant that can handle $1,000Nm^{3}/hr$ of flue gas was reported in this paper. And we also considered several factors that might cause abnormality of the plant in the designing process. The plant was designed and fabricated to test the $DeNO_{x}$ performances in variable operating conditions in the range of $3,000{\sim}36,000hr^{-1}/hr$ in space velocities, $1.67{\sim}6\;m/s$ in linear velocities, $200{\sim}500^{\circ}C$ temperatures, $300{\sim}1,000Nm^{3}/hr$ flow rates, and $0{\sim}1.4:1\;NH_{3}/NO$ ratios. In order to maintain the flow uniformity, the guide vanes and flow straightener were designed and constructed in the plant. The SCR pilot plant can be operated by the automatic control system, which enable to obtain performance data in real time and to set up the operating technology. The catalyst reactor consists of 4 catalyst layers and surface area of each layer can be adjusted to be of small size. Arrangement of catalysts per layer is $3{\times}6$ with the catalyst dimensions of $150{\times}150{\times}500mm(L{\times}W{\times}H)$.

• Journal of the Korean Institute of Gas
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• v.15 no.2
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• pp.21-26
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• 2011

Emissoin of heavy duty vehicle have much positioned in air pollution although its limited number of vehicles. CNG vehicles are coming to the fore as one of the solution of diesel vehicles. CNG vehicles exhaust smaller emission than diesel vehicles on PM and NOx. In this study, aftertreatment technologies are introduced on vehicles which use CNG and hydrogenmixed fuel. Withmixing hydrogen with CNG, combustion efficiency is enhanced, and harmful emission might be decreased, but methane that is main component of CNG brings green house effect. In order to remove methane and NOx in exhaust gas of CNG engine, methane oxidation catalyst and SCR technologies were respectively analyzed.

• Journal of Korean Society for Atmospheric Environment
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• v.17 no.4
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• pp.347-354
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• 2001

SCR (Selective Catalytic Reduction) process is presently considered as one of the most effective techniques for removing nitric oxides from exhaust gases. In this study, based on the conceptually designed SCR reactor of 500 MW coal fired power plant. a reduced scale (1/20) SCR reactor model was made to analyze the flow pattern in front of catalyst layer according to the guide vane's design factors such as the number, interval, and angle of vanes. The results of the test were compared to those numerical simulation in order to assure the reliability of two methods. On the basis of our study. the critical Reynolds number (2.0$\times$ 10$^{5}$ ) was proposed for ensuring the similarity between the reduced scale model and the prototype of SCR reactor. Optimum design parameters of guide vanes were determined as follows, 4 vanes, the first vane angle of 93$^{\circ}$, and the vane intervals of 0.85 S/n, 1.05 S/n, 1.1 S/n, 1.0S/n, 1.0S/n (S: the distance of duct, n: the number of guide vanes). The excellent agreement between the results of the numerical simulation and the reduced scale model provides the validation of two methods for prediction of flow through SCR reactor.

• Environmental Engineering Research
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• v.20 no.2
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• pp.155-161
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• 2015

Experimental research shows that the nitric oxides ($NO_X$) concentration track at the outlet of selective catalytic reduction (SCR) catalyst with a transient variation of Adblue dosage has a time delay and it features a characteristic of resistance-capacitance (RC). The phenomenon brings obstacles to get the simultaneously $NO_X$ expected to be reduced and equi-molar ammonia available to SCR reaction, which finally inhibits $NO_X$ conversion efficiency. Generally, engine loads change frequently, which triggers a rapid changing of Adblue dosage, and it aggravates the air quality that are caused by $NO_X$ emission and ammonia slip. In order to increase the conversion efficiency of $NO_X$ and avoid secondary pollution, the paper gives a comprehensive analysis of the SCR system and tells readers the key factors that affect time delay and RC characteristics. Accordingly, a map of time delay is established and a solution method for time constant and proportional constant is carried out. Finally, the paper accurately describes the input-output state relation of SCR system by using "variable RC model with time delay". The model can be used for a real-time correction of Adblue dosage, which can increase the conversion efficiency of $NO_X$ in SCR system and avoid secondary pollution forming. Obviously, the results of the work discover an avenue for the SCR control strategy.

• Bulletin of the Korean Chemical Society
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• v.27 no.9
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• pp.1287-1288
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• 2006

• Korean Chemical Engineering Research
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• v.49 no.1
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• pp.89-94
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• 2011

DeNOx characteristics of hybrid SNCR-SCR process have been investigated in a pilot scale flow reactor. DeNOx efficiency of SNCR reaction was about 80% at $970^{\circ}C$ and hybrid SNCR-SCR process showed 92% at $940^{\circ}C$ with NSR = 2.0. Compared to SNCR process alone, hybrid SNCR-SCR process was more effective at cool side, which is lower than $940{^{\circ}C}$. It should be also noted that ammonia slip from hybrid SNCR-SCR process was below 1ppm at the condition of higher space velocity and the required catalyst volume can be decreased to 2/3 of SCR process. Key factors for DeNOx efficiency of hybrid SNCR-SCR process were found to be $NH_3$ concentration and NOx selectivity of urea injected in SNCR process.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.2
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• pp.24-30
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• 2010

In this study, numerical experiments were carried out to estimate the SCR De-NOx performance in DOC plus SCR systems. The SCR De-NOx phenomena are described by Langmuir-Hinshelwood reaction scheme. After validating the present approach by comparing the present results with the experimental results, such various parameters as space velocity, $H_2O$ concentration, $NO_2$/NOx ratio and relative volume of DOC are explored to increase the SCR De-NOx performance. The results indicate that SCR De-NOx performance largely depends on space velocity and $NO_2$/NOx ratio, especially below $200^{\circ}C$. SCR De-NOx performance is seriously affected by relative volume of DOC with SCR due to increasing in $NO_2$/NOx ratio at below $250^{\circ}C$.

• Applied Chemistry for Engineering
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• v.23 no.3
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• pp.348-351
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• 2012

The effect of the addition of Cu on the catalytic activity of the $Mn/CeO_2-ZrO_2$ catalyst for the low-temperature SCR reaction of NO was investigated. Three different amounts of Cu, 5, 10, and 15 wt%, were impregnated on the $Mn/CeO_2-ZrO_2$ catalyst. The characteristics of the synthesized catalysts were examined by BET, XRD, XPS, and $H_2-TPR$ analyses. The de-NOx efficiency of the Cu-added catalysts increased with the amount of Cu. When 15 wt% Cu was impregnated, the deNOx efficiency was the highest, reaching as high as 99%. The increased deNOx efficiency is attributed to the enhanced reducing power stemming from the interaction between Mn and Cu on the catalyst surface.

• Clean Technology
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• v.27 no.4
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• pp.332-340
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• 2021

With the recent reinforcement of emission standards, it is necessary to make efforts to reduce NOx from air pollutant-emitting workplaces. The NOx reduction method mainly used in industrial facilities is selective catalytic reduction (SCR), and the most commercial SCR catalyst is the ceramic honeycomb catalyst. This study was carried out to reduce the NOx emitted from steel plants by applying De-NOx catalyst coated on metallic monolith. The De-NOx catalyst was synthesized through the optimized coating technique, and the coated catalyst was uniformly and strongly adhered onto the surface of the metallic monolith according to the air jet erosion and bending test. Due to the good thermal conductivity of metallic monolith, the De-NOx catalyst coated on metallic monolith showed good De-NOx efficiency at low temperatures (200 ~ 250 ℃). In addition, the optimal amount of catalyst coating on the metallic monolith surface was confirmed for the design of an economical catalyst. Based on these results, the De-NOx catalyst of commercial grade size was tested in a semi-pilot De-NOx performance facility under a simulated gas similar to the exhaust gas emitted from a steel plant. Even at a low temperature (200 ℃), it showed excellent performance satisfying the emission standard (less than 60 ppm). Therefore, the De-NOx catalyst coated metallic monolith has good physical and chemical properties and showed a good De-NOx efficiency even with the minimum amount of catalyst. Additionally, it was possible to compact and downsize the SCR reactor through the application of a high-density cell. Therefore, we suggest that the proposed De-NOx catalyst coated metallic monolith may be a good alternative De-NOx catalyst for industrial uses such as steel plants, thermal power plants, incineration plants ships, and construction machinery.