Sulfuric Dew Point Research Articles

Low-temperature direct electrochemical splitting of H2S

Hydrogen is considered one of the most promising decarbonized fuels. However, its applicability is limited due to the ecological constraints of its production. Hydrogen sulfide (H2S) is widely available in oil and gas reservoirs and has the potential of becoming an energetically favorable source of hydrogen. Nevertheless, its electrochemical separation into H2 and elemental sulfur has not been successfully achieved at the industrial scale, due to sulfur poisoning of the electrodes at the sulfur oxidation half-reaction. This review highlights the progress of the direct electrolytic separation of H2S below the sulfur dew point, where the sulfur poisoning effect becomes more prominent. The article discusses the different technologies and approaches explored to improve the energy efficiency and stability of H2S electrolytic systems, including the recent use of nanostructured electrodes and novel sulfur solvents as electrolytes.

EFFECTS OF EXCESS AIR AND COAL SULFUR CONTENT IN PERFORMANCE IMPROVEMENT OF 660 MW SUPERCRITICAL BOILERS IN TERMS OF ACID DEW POINT TEMPERATURE

The objective of this study was to select an appropriate fuel having different sulfur contents in various coal fuels and optimize the excess air in order to reduce dry flue gas loss, avoid equipment damage due to sulfur dew point corrosion, and reduce maintenance and equipment installation costs. A tri-sector rotary air preheater was employed to exchange heat between dry flue gases and preheat the air (both primary and secondary air). The results showed that coal with 0.6165% sulfur (fuel 2) caused acid dew point temperatures (ADPTs) of 122.38°C and 124.947°C with 15% and 20% excess air, respectively, in a rotary air preheater set at a 30.5° angle, whereas coal with 1.627% sulfur (fuel 1) caused ADPTs of 131.299°C and 133.602°C with 15% and 20% excess air, respectively, in a rotary air preheater set at a 35.99° angle. The experimental results indicate that the use of fuel 2 coal consumption can reduce carbon dioxide (CO<sub>2</sub>) emission by nearly 4 metric tons (MT)/hour, which is equivalent to a reduction of CO<sub>2</sub> emission of 3.8 MT/hour.

Mechanism research on coupling effect between dew point corrosion and ash deposition

In order to study the coupling mechanism between ash deposition and dew point corrosion, five kinds of tube materials frequently used as anti-dew point corrosion materials were selected as research objects. Dew point corrosion and ash deposition experiments were performed with a new type experimental device in a Chinese thermal power plant. The microstructures of the materials and the composition of ash deposition were analyzed by X-ray diffraction (XRD) and Energy Dispersive Spectrometer (EDS). The results showed that the ash deposition layer could be divided into non-condensation zone, the main condensation zone and the secondary condensation zone. The acid vapor condensed in the main condensation zone rather than directly on the tube wall surface. The dew point corrosion mainly is oxygen corrosion under the condition of the viscosity ash deposition, and the corrosion products are composed of the ash and acid reaction products in the outer layer, iron sulfate in the middle layer, and iron oxide in the inner layer. The innermost layer is the main corrosion layer. With the increase of the tube wall temperature, the ash deposition changes from the viscosity ash deposition to the dry loose ash deposition, the ash deposition rate decreases dramatically and dew point corrosion is alleviated efficiently. The sulfuric dew point corrosion resistance of the five test materials is as follows: 316L > ND > Corten>20G > 20# steel.

Kinetic peculiarities in the low-temperature oxidation of H 2S over vanadium catalysts

H 2S oxidation by oxygen over V 2O 5/Al 2O 3, V 2O 5/TiO 2, V 2O 5/SiO 2, V 2O 5/Al 2O 3/TiO 2 catalysts was studied at the temperature below the sulfur dew-point. High activity and the oscillation nature of the oxidation process were demonstrated for the catalysts with low V 2O 5 contents (2–5 wt.%) supported on Al 2O 3, TiO 2 or a combination thereof. An increase in the V 2O 5 concentration up to 10–20 wt.% resulted in lowering of the catalytic activity and oscillation ability. The oscillations were not determined using V 2O 5/SiO 2 and pure V 2O 5 catalysts. Difference between pure V 2O 5, catalysts with high- and low-loaded V 2O 5 catalysts was accounted for by the structure of V 5+ species formed in catalysts. The high activity of the catalysts with the low vanadium content supported on Al 2O 3, TiO 2 or combinations thereof was attributed to vanadium species bound directly to the surface.

Continuous process for selective oxidation of H 2S over SiC-supported iron catalysts into elemental sulfur above its dewpoint

Iron supported on silicon carbide (SiC) is shown to be a high conversion catalyst for the oxidation of H 2S with a high selectivity into elemental sulfur above sulfur dewpoint in the presence of large amounts of oxygen and steam in the feed. The active phase is probably an iron oxysulfide or a non-stoichiometric sulfate phase. It is stable for several weeks in an industrial micropilot plant, and no deactivation is observed even in the presence of a large amount of steam. These performances are due to the intrinsic physical properties of the SiC carrier but also because of the optimal dispersion of the active phase.

Kinetic Peculiarities in the Low-Temperature Oxidation of H 2 S on Vanadium Catalysts

H2S oxidation by oxygen on catalysts V2O5/Al2O3, V2O5/TiO2, V2O5/Al2O3/TiO2 was studied at temperatures below the sulfur dew point. High activity and the oscillation character of the oxidation were demonstrated by catalysts with low contents of V2O5 (3–5 wt.%). The increase in the V2O5 concentration to 10–20 wt.% results in the reduction of the catalytic activity and oscillation ability. On a pure V2O5 catalyst, the oscillations were not detected. The difference between the catalysts with the high and low concentrations of V2O5 is explained in terms of the structures of the V5+ species formed in the catalysts.

Kinetics and Mechanism of low-Temperature Oxidation of H2S with Oxygen in the gas Phase

The possibility of the formation of polysulfides during oxidation of H2 S with oxygen on oxide catalysts has been checked, and the sequence of the reaction stages at temperatures below the sulfur dew point determined. The amount of polysulfides formed during H2 S oxidation has been found to exceed significantly that obtained in the reaction of sulfur with H2 S. Polysulfides are concluded to be intermediates in H2 S oxidation to sulfur. The rate of formation of SO2 from sulfur vapor is shown to be negligibly low at 100-200°C. A reaction scheme involving the formation of sulfur from polysulfides and the formation of sulfur dioxide by direct oxidation of H2 S is suggested.

硫酸露点腐食

硫酸露点腐食

The Mechanism of Sulfur Dewpoint Corrosion

The Mechanism of Sulfur Dewpoint Corrosion

硫黄露点腐食機構

硫黄露点腐食機構

硫黄露点腐食における実験室的試験方法

硫黄露点腐食における実験室的試験方法

含銅鋼の硫黄露点腐食性におよぼす合金元素の影響

含銅鋼の硫黄露点腐食性におよぼす合金元素の影響

硫酸中における含銅鋼のアノード分極挙動におよぼす合金元素の影響

Selecting some essential and important alloying elements from the point of view of sulfur dewpoint corrosion, the anodic polarization curves of copper steels in 85%H2SO4 at 110°C have been obtained for understanding their effect on the passivation behavior of the steels. The results of the study were shown as follows.(1) Effect of P, V, Zr, As and Cr (containing about 0.5%) on the anodic bahavior of 0.5%Cu-0.5%Ni steel: Cr followed by P was the most effective element in decreasing the primary passive current density (p.p.c.d.). On the other hand, As resulted in a remarkable increase in both the primary passivation current density and p.p.c.d., Zr and V had little effect on the polarization curve.(2) Effect of C, B and Cr on the anodic behavior of 0.3%Cu steel: Increasing C up to 0.45% resulted in some reduction of the secondary passive current density, and 0.3% of boron a remarkable decrease in the p.p.c.d. Both elements shifted the corrosion potential to the noble direction. For the effect of less than 18%Cr, the steels containing Cr 18% resulted in lowering p.p.c.d. while 5%Cr resulted in an increase in the current density more than mild steel.(3) Effect of Si and Mn on the anodic behavior of 0.3%Cu-1%Cr steel: Increasing Si up to 2.76% resulted in a remarkable rising of the primary passive current density, whereas increasing Mn up to 1.45% resulted in a large reduction of p.p.c.d. Increasing Si also decreased the secondary passive current density to some extent.(4) In general, the corrosion resistant low alloy steels to the sulfur dewpoint corrosion had a comparatively lower primary passive current density than that of the non-corrosion resistant steels.

低合金鋼の耐硫酸性におよぼす添加元素の影響について

In an attempt to develop the better effective low-alloy steel to the sulfur dewpoint corrosion in flue gases, an investigation was made in which the effects of alloying elements on the corrosion rate in 40% sulfuric acid at 60°C were studied. Since the superior effect of copper (0.1%) in steel had already been recognized, these effects of alloying elements were investigated in the presence of copper.According to the results of weight-loss tests with 4-hour immersion in the same solution as mentioned before, the effects of alloying elements may be classified as follows:(1) more effective: Sb, Se, As (antimony was most effective),(2) slightly effective: Si,(3) little effective: Sn, Bi, Te,(4) slight accelerating effect on corrosion: C, Mn,(5) accelerating effect on corrosion: P, S, Ti, Mo, Cr, Ni (The corrosion rate was linear to the sulfur content, and exponential to the phosphorus content).