Integration of sorption-enhanced steam glycerol reforming with methanation of in-situ removed carbon dioxide - An alternative for glycerol valorization

Coupling CO₂ desorption and methanation in the presence of hybrid materials offers a promising alternative to convert the CO₂ in-situ removed during sorption-enhanced steam glycerol reforming (SESGR) avoiding the high energy-intensive CO₂ sorbent regeneration. The all-inclusive integrated process exemplifies an option for glycerol valorization via consecutive SESGR and CO₂ conversion by catalytic hydrogenation. The dual-function catalyst performing successively, in the same reactor, SESGR and CO₂ desorption/conversion encompasses reforming/methanation catalyst (10%Ni5%Co) and dispersed nano-sized CaO on γ-Al₂O₃. Simultaneous CO₂ desorption/conversion integrated process is explored in a fixed-bed reactor via an unsteady-state, two-scale, non-isothermal model, highlighting the impact of key parameters on the process performance. At large adsorbent/catalyst mass ratio (2.0) and high CaO conversion (0.5) in preceding SESGR, CO₂ is released and hydrogenated for an extended period with extra hydrogen consumption, without a balance between CO₂ desorption and CO₂ hydrogenation rates. Increasing pressure (3.0 MPa) and gas velocity offers a match between these competitive reaction rates, resulting low CO₂ concentration in the exit stream. Desorption/methanation thermal behavior controls the magnitude of CO₂ low concentration period and the methanation efficiency.     

Analysis of laminar heat transfer in micro-Poiseuille flow

The present study examines laminar forced convective heat transfer of a Newtonian fluid in a microchannel between two parallel plates analytically. The viscous dissipation effect, the velocity slip and the temperature jump at the wall are included in the analysis. Both hydrodynamically and thermally fully developed flow case is examined. Either the hot wall or the cold wall case is considered for the two different thermal boundary conditions, namely the constant heat flux (CHF) and the constant wall temperature (CWT). The interactive effects of the Brinkman number and the Knudsen number on the Nusselt numbers are analytically determined. Different definitions of the Brinkman number based on the definition of the dimensionless temperature are discussed. It is disclosed that for the cases studied here, singularities for the Brinkman number-dependence of the Nusselt number are observed and they are discussed in view of the energy balance.     

An advanced zero emission power cycle with integrated low temperature thermal energy

An innovative zero emission hybrid cycle named HICES (hybrid and improved CES cycle) is presented in this paper. It can utilize fossil fuel and low quality thermal energy such as waste heat from industrial processes and solar thermal energy for highly efficient electric power generation. In the HICES cycle, natural gas is internally combusted with pure oxygen. External low quality thermal energy is used to produce saturated steam between 70 and 250 °C as part of the working fluid. The thermodynamic characteristics at design conditions of the HICES cycle are analyzed using the advanced process simulator Aspen Plus. The influences of some key parameters are investigated. The results demonstrate that the thermodynamic performances of the HICES cycle are quite promising. For example, when the external heat produced saturated steam is at 70 °C, the net fuel-to-electricity efficiency is 54.18% even when taking into account both the energy penalties to produce pure oxygen and to liquefy the captured CO₂. The incremental low temperature heat to electric efficiency is as high as 14.08% at the same time. When the external heat produced saturated steam is at 250 °C, the net fuel-to-electricity efficiency reaches 62.66%. The incremental low temperature heat to electric efficiency achieves 48.92%.     

Fast Vortex Method for the Simulation of Flows Inside Channels With and Without Injection

A fast vortex method is presented for the simulation of fluid flows inside two-dimensional channels. The first channel studied is formed by two parallel walls simulating the entrance length of a developing flow. The second channel is similar to the first one but with an injection of a secondary fluid through a slot on one of its walls. In both cases, results are presented for flows at low Reynolds numbers and for flows at a high Reynolds number. The numerical method used is based on the Random Vortex Method and on the Vortex-In-Cell algorithm. Physical analyses of the numerical results are also presented, mostly in application to film cooling.     

Numerical analysis on a microchannel evaporator designed for CO2 air-conditioning systems

A microchannel heat exchanger was numerically analyzed using the finite volume method. The air and refrigerant-side heat transfer coefficients and pressure drops were calculated using the existing correlations that were developed for microchannel heat exchangers. To verify the present model, performance tests of the microchannel heat exchanger were conducted at various test conditions with R134a. The present model yielded a good correlation with the measured heat transfer rate, demonstrating a mean deviation of 6.8%. The performance of the microchannel evaporator for CO₂ systems can be improved by varying the refrigerant flow rate to each slab and changing fin space to increase the two-phase region in the microchannel. Based on the comparison of the performance of the microchannel heat exchanger with that of the fin-tube heat exchanger designed for CO₂ systems, it was proposed that the arrangement of the slabs and inlet air velocity in the microchannel heat exchanger need to be optimized by considering heat exchanger size, air outlet conditions and required capacity.     

膜盘联轴器-燃气轮机发电机组转子系统动力学分析

通过MATLAB对燃气轮机发电机组耦联转子系统进行了数值仿真,采用Newmark-β方法求解运动微分方程,在考虑膜盘联轴器由于大变形引起的刚度非线性下,分析了耦联转子系统临界转速、模态振型、不平衡响应和联轴器刚度对耦联转子系统动力学特性的影响,仿真结果表明:采用非线性刚度和线性刚度模型描述膜盘联轴器相差16.77%;耦联转子系统的临界转速和不平衡振动响应较单转子系统有所增加;联轴器刚度的增加会提高耦联转子系统的临界转速同时不平衡振动响应也会增大。     

服务业公建洗浴余热回收器实验及应用研究

针对服务业公共建筑中的洗浴热能浪费问题,应用一种余热回收器实现洗浴用水余热的回收利用,通过实验研究了不同冷水温度和喷淋温度下回收器的节能效果,结果表明该回收器性能优越,可以回收超过50%的淋浴余热,具有明显的经济效益和广阔的市场前景.     

Efficient energy systems with CO2 capture and storage from renewable biomass in pulp and paper mills

This paper investigates the impact of combining CO₂ capture and storage with alternative systems for biomass-based combined heat and power production (CHP) in Kraft pulp and paper mills. We compare heat, power, and CO₂ balances of systems with alternative configurations of the CHP and CO₂-capture systems. Because the captured CO₂ comes from renewable biomass, the studied systems yield negative CO₂ emissions. It is shown that pulp mills and integrated pulp and paper mills have the potential to become net exporters of biomass-based electricity while at the same time removing CO₂ from the atmosphere on a net basis. The study shows that that the overall best CO₂ abatement is achieved when CO₂ capture is carried out within a biomass integrated gasifier with combined cycle where the syngas undergoes a CO-shift reaction. This configuration combines efficient energy conversion with a high CO₂ capture efficiency. Furthermore, cost curves are constructed, which show how the cost of CO₂ capture and storage in pulp and paper mills depends on system configuration and the CO₂ transportation distance.     

NUMERICAL SIMULATION AND ANALYSIS OF PRESSURE PULSATION IN FRANCIS HYDRAULIC TURBINE WITH AIR ADMISSION

In this article, the three-dimensional unsteady multiphase flow is simulated in the whole passage of Francis hydraulic turbine. The pressure pulsation is predicted and compared with experimental data at positions in the draft tube, in front of runner, guide vanes and at the inlet of the spiral case. The relationship between pressure pulsation in the whole passage and air admission is analyzed. The computational results show: air admission from spindle hole decreases the pressure difference in the horizontal section of draft tube, which in turn decreases the amplitude of low-frequency pressure pulsation in the draft tube; the rotor-stator interaction between the air inlet and the runner increases the blade-frequency pressure pulsation in front of the runner.     

Combustion in bubbling fluidised bed with bed material of limestone to reduce the biomass ash agglomeration and sintering

A bed material of limestone was used in order to reduce/eliminate the tendency for bed material agglomeration and sintering that normally occurs in plants that operate with the traditional silica bed material. Combustion tests were carried out in a bubbling fluidised bed (BFB) combustion pilot plant (1 MWth). Mass balances of the inorganic elements and ash characterisation with respect to bed agglomeration, fouling and emissions were performed in the BFB combustion pilot plant.Limestone bed material with particle sizes between 0.25 and 2 mm, corresponding to a mean fluidisation velocity of 1.2 m/s and at a mean bed temperature of 775 °C, were chosen. It has been successfully proven that the limestone bed material eliminates the bed agglomeration. The calcium particles, which escape from the limestone bed material and are adhered on heat exchangers, reduce the sintering of ash deposits on the tubes.