Reducing industrial hydrogen demand through preheating with very high temperature heat pumps

Decarbonising industry while maintaining economic competitiveness and improving living standards is one of the main challenges of reaching net zero targets, and low-carbon process heating will play a key role in this. In this work we investigate the potential to reduce the energy demands of hydrogen-based industrial heating systems using very high temperature reverse Joule-Brayton cycle heat pumps as preheaters, considering their economics and technical challenges. A thermodynamic process model is used to assess performance at temperatures of 300–500 °C, and cost optimisation is used to conduct cost-benefit analysis of preheating green hydrogen using heat pumps. It is found that over this temperature range, heat pump coefficient of performance lies in the range 1.4–1.7, with the turbine meeting 30–40% of the compressor load. At the electricity prices currently paid by heavy industry in Western Europe, levelised cost of heat from these heat pumps would be less than 4.5p/kWh. Using 500 °C heat pumps as preheaters in hydrogen heating systems could reduce hydrogen demands by over 20% and provide savings on the cost of green hydrogen of at least 8% out to 2050. With process heat accounting for three-quarters of industrial energy use and half of this being at temperatures above 400 °C, these savings are significant and suggest that very high temperature heat pumps could make an important contribution to industrial decarbonisation

Investigation of particle radiation and its effect on NO prediction in a pilot-scale facility for both air and oxy-coal combustion

Radiation heat transfer plays an important role in pulverised coal combustion, influencing the overall combustion efficiency, pollutant formation and flame ignition and propagation. In this paper, the radiation properties of the particles as well as gas property models on the overall influence of the prediction of the formation of NOx pollutants in a pulverised coal combustion have been investigated. The non-grey weighted sum of grey gases (WSGG) model has been employed to calculate the radiation of the gas phase coupled with the radiation interaction from the particulate phase. The Mie theory, as well as constant or linear models, have been employed to describe the particle radiative properties. The prediction results, calculated from the data from a 250 kW pilot scale combustion test facility (CTF), are compared against experimental measurements under air-fired condition and a range of oxyfuel conditions. The results show that the choice of radiation solution can have a considerable impact on the radiative heat transfer results, in which the Mie theory shows a significant improvement in the incident wall heat flux compared to the constant or linear models. Also, the more accurate solution employed for radiation of gases and particles considerably improves the NOx prediction in the flame region

Ab Initio Calculation of the Lattice Distortions induced by Substitutional Ag- and Cu- Impurities in Alkali Halide Crystals

An ab initio study of the doping of alkali halide crystals (AX: A = Li, Na, K, Rb; X = F, Cl, Br, I) by ns2 anions (Ag- and Cu-) is presented. Large active clusters with 179 ions embedded in the surrounding crystalline lattice are considered in order to describe properly the lattice relaxation induced by the introduction of substitutional impurities. In all the cases considered, the lattice distortions imply the concerted movement of several shells of neighbors. The shell displacements are smaller for the smaller anion Cu-, as expected. The study of the family of rock-salt alkali halides (excepting CsF) allows us to extract trends that might be useful at a predictive level in the study of other impurity systems. Those trends are presented and discussed in terms of simple geometric arguments.Comment: LaTeX file. 8 pages, 3 EPS pictures. New version contains calculations of the energy of formation of the defects with model clusters of different size

Ductile-Phase Toughening of Brazed Joints

A heat treatment is presented that uses ductile-phase toughening to mitigate the effect of brittle intermetallics in a Ni-based braze alloy. The fracture resistance has been enhanced by creating a microstructure containing elongated ductile γ-(Ni) domains that align, preferentially, across the joint. The development of this beneficial microstructure is based on an understanding of the transient dissolution, isothermal solidification, and coarsening phenomena. Due to slow kinetics, the elimination of intermetallics by diffusion is avoided in favor of ductile domain formation through solidification control. The toughening has been attributed to a combination of bridging and process zone dissipation, enabled by the ductile phase

Joining of nickel-base substrates using Ni-Si-B and Ni-P alloys

Available from British Library Document Supply Centre- DSC:D061559 / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo

Intrinsic thresholds in polycrystalline Udimet 720

The long crack threshold behaviour of polycrystalline Udimet 720 has been investigated. Faceted crack growth is seen near threshold when the monotonic crack tip plastic zone is contained within the coarsest grain size. At very high load ratios R(=P[min]/P[max]) it is possible for the monotonic crack tip plastic zone to exceed the coarsest grain size throughout the entire crack growth regime and non-faceted structure insensitive crack growth is then seen down to threshold. Intrinsic threshold values were obtained for non-faceted and faceted crack growth using a constant K[max], increasing K[min], computer controlled load shedding technique (K is stress intensity factor)