NH3-H2O Mixture Research Articles

Corrosion Behavior of Sliding Materials in NH3-H2O Solutions at High Temperature

To investigate the shaft seal for NH3-H2O binary vapor turbines, first of all, immersion tests of several sliding materials were carried out in a static NH3-H2O mixture (NH3 concentration: 30wt%) for 100h under the condition of maximum temperature at 450°C. The test materials were selected from the sliding materials commonly used as mechanical seal rings, such as SiC ceramics, Al2O3 ceramics, hard metals and carbon materials. (1) SiC specimens prepared with B (boron) and C (carbon) as sintering additives under the pressureless sintering process were confirmed to be most preferable. On the other hand, pressureless sintered SiC with Al2O3 additive and reaction bonded SiC indicated worse anti-corrosive resistivity. The Al2O3 additive in the pressureless sintered SiC and the excess metallic Si in the reaction bonded SiC were the most corrosive parts in the structure of SiC ceramics. (2) Al2O3 were recognized as anti-corrosive materials. (3) Hard metals were corroded easily. (4) The resin was corroded selectively in resin impregnated carbon material. Non-impregnated carbon material was hardly corroded. (5) These materials, with better anti-corrosive properties, can be used for the mechanical seal of NH3-H2O binary vapor turbines, although the increase in the surface roughness and the reduction of the bending strength were observed slightly.

Kinetic and electron paramagnetic resonance studies of photochemical reactions of gas mixtures of methane, ammonia and water

Photoactivation of methane has been kinetically studied in the CH4–NH3–H2O mixture, and the radical intermediates measured by the spin trap (PBN, α-phenyl-N-tert-butylnitrone)–EPR method. The trapped radicals were CH3O˙(aN= 1.35, aHβ= 0.20 mT), ˙CH2NH2(aN= 1.46, aHβ= 0.26 mT), and ˙CHNH (aN= 1.48, aHβ= 0.62 mT). It was suggested that ˙CH2NH2 was mainly provided by H abstraction from methylamine and the photolysis of CH3NH2 to CH3NH˙ and ˙CH2NH2 was low. The coupling of ˙CH2NH2 led to the formation of ethylenediamine, while CH3NH˙ decayed to CH2NH from which the ˙CHNH radical was generated by the H elimination. The water photolysis proceeded with a quantum yield of 0.06 in the gas mixture.

Development of Dry-Type Simultaneous Removal Process for Sulfur Oxides and Nitrogen Oxides

A dry method to remove simultaneously SOx and NOx with CuO-Al2O3-TiO2 was investigated. This method is based on the principle that SOx can be removed by the sulfation with CuO (SO2+ (1/2) O2+CuO-CuSO4, SO3+CuO→CuSO4) and NOx removed by the catalytic reduction with NH3 (NO+NH3+ (1/4) O2→N2+ (3/2) H2O, NO2+ (4/3) NH3→ (7/6) N2+2H2O, NO+NO2+2NH3→2N2+3H2O) over CuSO4 formed. Thus, the most important problem for practical use of this process is to develop a technique to regenerate repeatedly the-catalyst employed. The experiment for removal of SOx and NOx was carried out using a flow type packed bed reactor under atmospheric pressure at 350°C. The inlet gas was 1000ppm SO2-500ppm NO-667ppm NH3-5%O2-10%H2O-N2. The metal oxides were prepared by the coprecipitation from CuSO4, TiCl4 aq. etc. with NH3 aq., The examinations for regeneration were carried out by reduction with NH3, etc. or by thermal decomposition. The third components added to CuO-TiO2 as an improvement agent were Al2O3, SiO2, Fe2O3 or V2O5. The following results were obtained: 1) 40-50mol%CuO-60-50mol%TiO2 was suitable for only a SOx absorbents. The regeneration of these solids was possible by mild reduction (CuSO4→Cu3N) with NH3-H2O mixture (1% NH3-7.4% H2O-N2) at 400°C, and then by mild oxidation (Cu3N-CuO) with O2-H2O mixture (5% O2-10% H2O-N2) at 350°C. 2) 40mol%CuO-20mol% Al2O3-40mol% TiO2 was the metal oxides of the most preferable composition for the dry simultaneous removal of SOx and NOx. This regeneration was carried out sufficiently by the reduction (CuSO4→Cu3N) with 20% NH3-7.4% H2O-N2 at 400°C, and then by the oxidation (Cu3N→CuO) with 5% O2-10% H2O-N2 at 350°C.

Ultrasound propagation in NH3–H2O mixtures

Data on the sound velocity and absorption in liquid mixtures of NH3 and H2O are presented. The sound velocity at 10 MHz was measured as a function of concentration and temperature. The absorption was measured as a function of frequency (between 10 and 85 MHz), concentration, and temperature. The results indicate that the NH3−H2O system behaves ultrasonically like mixtures of associated liquids with a relaxation due to the electrolytic nature of NH3.