Hydrogen Recovery Ratio Research Articles

New insights into the impurity transport and separation behaviours during metal hydride dehydrogenation for ultra-pure hydrogen

The hydrogen separation and purification method based on metal hydride (MH) is viewed as one of the ideal methods for recycling industrial by-product hydrogen. Usually, self-produce hydrogen purging is conducted to remove the impurity. However, the mechanism of impurity transport and separation under the MH dehydrogenation process is still not clear so that the purity of produced hydrogen or the hydrogen recovery ratio is low. In this paper, a novel poisoning dehydrogenation kinetics considering the effect of passivation layer is proposed to accurately describe the dehydrogenation properties under the impurity poisoning conditions. The poisoning factor is introduced to describe the poisoning effect of impurities on MH materials. More active impurity or higher impurity concentration result in the larger poisoning factor. Based on the poisoning dehydrogenation kinetics, the MH dehydrogenation reaction model for self-produce hydrogen purging process is developed to describe the impurity transport and separation behaviours. The effects of operating parameters on the impurity transport and separation are further investigated for ultra-pure hydrogen. It is found that the low temperature and low outlet flow rate results in the low hydrogen loss for ultra-pure hydrogen. After the optimization, an efficient hydrogen separation and purification with both a hydrogen purity of 99.9999% and a hydrogen recovery ratio of more than 80% is achieved, which shows the potential in the hydrogen separation and purification of industrial by-product hydrogen.

Total Site Hydrogen Integration with fresh hydrogen of multiple quality and waste hydrogen recovery in refineries

This paper proposes a novel method combining Pinch Methodology and waste hydrogen recovery, aiming to minimise fresh hydrogen consumption and waste hydrogen discharge. The method of multiple-level resource Pinch Analysis is extended to the level of Total Site Hydrogen Integration by considering fresh hydrogen sources with various quality. Waste hydrogen after Total Site Integration is further regenerated. The technical feasibility and economy of the various purification approaches are considered, demonstrated with a case study of a refinery hydrogen network in a petrochemical industrial park. The results showed that fresh hydrogen usage and waste hydrogen discharge could be reduced by 21.3% and 67.6%. The hydrogen recovery ratio is 95.2%. It has significant economic benefits and a short payback period for Total Site Hydrogen Integration with waste hydrogen purification. The proposed method facilitates the reuse of waste hydrogen before the purification process that incurs an additional environmental footprint. In line with the Circular Economy principles, hydrogen resource is retained in the system as long as possible before discharge.

Application of elevated temperature pressure swing adsorption in hydrogen production from syngas

A clean and energy-efficient power system can be developed by the combination of hydrogen (as an energy carrier) and fuel cells (as power generation units); such system has the potential to compete with the current energy consumption pattern of direct combustion of fossil fuels. A novel CO/CO2 purification process, called the elevated-temperature pressure swing adsorption (ET-PSA), is coupled into an integrated gasification fuel cell (IGFC) power plant system in this work. A quantitative evaluation standard for the purification energy consumption is developed by considering both the net power efficiency loss of the IGFC after introducing the purification unit, and the total CO/CO2 removal rate. The sensible heat loss of syngas and the thermal regeneration of the saturated adsorbents are avoided; consequently, the calculated energy consumption of the ET-PSA (1.11 MJ/kg) process using the ideal purification unit as the base case is 36.2% lower than of the conventional solvent absorption method. Alternatively, high-temperature steam is consumed in the ET-PSA process during the rinse and purge steps, which leads to a decrease in the output power of the steam turbine. The purification energy consumption of the ET-PSA process can be further reduced either by increasing the hydrogen recovery ratio or by reducing the total steam consumption.

Process analysis of hydrogen production from biomass gasification in fluidized bed reactor with different separation systems

Gasification is one of the most effective and studied methods for producing energy and fuels from biomass as different biomass feedstock can be handled, with the generation of syngas consisting of H2, CO, and CH4, which can be used for several applications. In this study, the gasification of hazelnut shells (biomass) within a circulating bubbling fluidized bed gasifier was analyzed for the first time through a quasi-equilibrium approach developed in the Aspen Plus environment and used to validate and improve an existing bubbling fluidized bed gasifier model. The gasification unit was integrated with a water-gas shift (WGS) reactor to increase the hydrogen content in the outlet stream and with a pressure swing adsorption (PSA) unit for hydrogen separation. The amount of dry H2 obtained out of the gasifier was 31.3 mol%, and this value increased to 47.5 mol% after the WGS reaction. The simulation results were compared and validated against experimental data reported in the literature. The process model was then modified by replacing the PSA unit with a palladium membrane separation module. The final results of the present work allowed comparison of the effects of the two conditioning systems, PSA and palladium membrane, indicating a comparative increase in the hydrogen recovery ratio of 28.9% with the palladium membrane relative to the PSA configuration.

Two-train elevated-temperature pressure swing adsorption for high-purity hydrogen production

The trade-off between hydrogen recovery ratio (HRR) and hydrogen purity (HP) is one of the main drawbacks in normal temperature pressure swing adsorption (NT-PSA) for producing high-purity hydrogen from shifted gas. In this paper, a two-train elevated-temperature pressure swing adsorption (ET-PSA) process that achieved 99.999% HP and over 95% HRR is proposed, which has wide application potentials in fuel cells and chemical industries. Potassium-promoted layered double oxide (K-LDO), which shows reasonable working capacity and fast adsorption/desorption kinetics at elevated temperatures (200–450 °C), is adopted as the CO2 adsorbent. CO in the shifted gas is co-purified by high-temperature water gas shift (WGS) catalysts added to the columns. The first-train ET-PSA adopted an eight-column thirteen-step configuration with shorter step time to remove most of the CO/CO2 in the shifted gas, and the second-train ET-PSA adopted a double-column seven-step configuration with longer step time to purify the residual gas impurities. The introduction of co-current high-pressure steam rinse and counter-current low-pressure steam purge is the key to achieve both high HRR and HP. The high-temperature steam is the main energy consumption of ET-PSA rather than low HRR in NT-PSA, and the total steam consumption is reduced by adopting the tail gas from second-train ET-PSA as the purge gas for first-train ET-PSA. The optimal results achieved 97.51% HRR and 99.9994% HP with only 0.188 rinse-to-feed ratio and 0.263 purge-to-feed ratio, which are the highest values reported for PSAs producing high-purity hydrogen from carbon-based fuels.

Optimal design of inter-plant hydrogen network with purification reuse/recycle

Hydrogen-rich gas from fertilizer plant and ethylene plant can be sent to refinery in a petrochemical complex, which can alleviate the deficit of hydrogen in refinery. Thus the optimization of inter-plant hydrogen network in a petrochemical complex is attractive. A novel superstructure for the optimal design of inter-plant hydrogen network with purification process is proposed and the corresponding mathematical programming models are presented for different scenarios. Two cases are utilized to illustrate the proposed approach. The flowrates of hydrogen utilities in refinery can be reduced via the inter-plant optimization. The number of inter-plant connections is optimized to simplify the network configuration. The shortcut model for pressure swing adsorption (PSA) considering the design conditions (pressure ratio and adsorbent selectivity) is also embedded into the mathematical programming model. The impacts of those design conditions of PSA on the performance of inter-plant hydrogen network are investigated. With the reduction of adsorbent selectivity and the increment of pressure ratio, the hydrogen recovery ratio will increase and the total annual cost will be reduced.

Assessment of feasible strategies for seasonal underground hydrogen storage in a saline aquifer

Renewable energies fluctuate, resulting in temporary mismatches between demand and supply. The conversion of surplus energy to hydrogen and its storage in geological formations is one option to counteract this energy imbalance. This study evaluates the feasibility of seasonal storage of hydrogen produced from wind power in Castilla-León region (northern Spain). A 3D multiphase numerical model is used to test different extraction well configurations during three annual injection-production cycles in a saline aquifer. Results demonstrate that underground hydrogen storage in saline aquifers can be operated with reasonable recovery ratios. A maximum hydrogen recovery ratio of 78%, which represents a global energy efficiency of 30%, has been estimated. Hydrogen upconing emerges as the major risk on saline aquifer storage without using other cushion gases. However, shallow extraction wells can minimize its effects. Steeply dipping geological structures are key for an efficient hydrogen storage.

Numerical study of hydrogen purification using metal hydride reactor with aluminium foam

The present paper describes a numerical study of heat and mass transfer processes in a metal hydride reactor for hydrogen purification with aluminium foam. The mathematical model, which was used previously for numerical simulation of heat and mass transfer processes in different types of metal hydride reactors, was modified for a reactor with aluminium foam. To validate the thermal equilibrium between the aluminium foam and metal hydride, pore-scale modelling was performed. In the case of pure hydrogen sorption, the model was validated by a comparison with experimental data; good agreement for sorption dynamics was obtained. The effects of various parameters of the pressure swing absorption method on the effectiveness of metal hydride systems for hydrogen purification were studied. The obtained results show that the use of aluminium foam enhances intensity of heat and mass transfer and consequently decreases the time required for hydrogen purification (up to two times) compared to a case without aluminium foam, while the volumetric capacity of the system is reduced slightly (9%). It is shown that pressure swing absorption method with fixed time interval between purges and the method with fixed interval of the fraction changing of the transformed material between purges provide a similar performance; in the second case the hydrogen recovery ratio remains constant during the hydrogen purification process.

An iterative method for designing hydrogen networks with regeneration unit

In order to release resource shortage constraints, hydrogen effective use is of great importance for refineries nowadays. Hydrogen utility consumption in a hydrogen network involving regeneration can be reduced further compared to that of the network involving reuse only. In this article, an iterative method is presented for design of hydrogen networks involving regeneration reuse. The following new insight obtained in water networks is adopted: the hydrogen network involving regeneration can be formed by adding the regenerated stream into the original hydrogen network. This will simplify the design and targeting of the networks with regeneration unit(s). The iterative method proposed can be used to design and target the networks with both fixed regenerated concentration and that with fixed hydrogen recovery ratio. An estimation method is proposed to calculate the regenerated concentration and flow rate for the regeneration unit with fixed hydrogen recovery ratio. A few literature examples are investigated with the proposed method. The results obtained in this work are comparable to that obtained in the literature. It is shown that the method proposed is simple and effective.

Pd-based composite membrane and its high-pressure module for pre-combustion CO2 capture

This study investigates configuration of a module for withstanding high pressure and temperature for CO2 capture from a coal gasifier. In order to increase the durability of the module at high pressure and temperature, a flange-type unit-cell module was installed in a high-pressure chamber. Hydrogen permeation and N2 leakage tests showed that H2/N2 selectivity remained at ∼4000 after ∼300 h at a pressure difference of 2000 kPa (∼20 bar) and 673 K. A CO2 capturing test was carried out at 673 K and a pressure difference of 2000 kPa with a 40% CO2 + 60% H2 feed gas mixture, which is similar to the composition in a coal gasifier after shift reaction and H2O removal. It was shown that CO2 could be enriched up to 78–95% with a hydrogen recovery ratio of 82–97% when the feed flow rate was 0.05–0.17 Nm3 h−1 with a membrane surface area of 16. 6 cm2.

The property of hydrogen separation from CO2 mixture using Pd-based membranes for carbon capture and storage (CCS)

This study investigates the module configuration for upscaling CO2 capture capacity to a bench-scale in hydrogen selective Pd-based composite membranes. In order to confirm effective upscaling, four plate-type membranes of two inch diameter were stacked in a newly designed plate-and-frame type module, reaching a total membrane surface area of 6.64 × 10−3 m2 (66.4 cm2). A pure gas test carried out using H2 and He confirmed that there were no effects of module configuration in gas permeation behavior, indicating that the upscale of the separation capacity by numbering-up of membranes using our module design was successful. The CO2 enrichment test was conducted using a 40%CO2 + 60%H2 mixture (i.e. a similar composition for the coal gasifier after both the shift reaction and H2O removal), under high feed pressure and flow rate, i.e. 600–2100 kPa and 0.48–0.72 N m3 h−1. The mixture gas test confirmed that the bench-scale membrane module could enrich 40% of the CO2 at a feed flow rate of 0.48 N m3 h−1 up to 93% with a hydrogen recovery ratio of >90% at 673 K and a total feed pressure of 2100 kPa, i.e. ∼4 times CO2 enrichment capacity of one membrane.

Hydrogen recovery from ethylene mixture with PD-AU composite membrane

Hydrogen separation from the refinery off-gas of the ethylene decomposition was carried out with Pd-1wt.%Au alloy membranes deposited on a porous nickel support using the sputtering and polishing method. In order to verify the effect of ethylene on the membrane, hydrogen permeation tests were carried out with 5% ethylene mixtures at temperatures ranging from 573 to 673 K and pressure differences ranging from 500 to 1500 kPa. Hydrogen permeation tests, which were carried out with the membranes that had an effective area of 16.6 cm2, revealed that the ethylene mixture did not affect hydrogen permeation behavior when the feed streams were 3000 ml min−1 and the pressure difference was 500 kPa at 673 K. As the pressure difference and temperature increased and the feed flow rate decreased, hydrogen permeation flux became less than ideal, indicating that depletion was a major factor in the hydrogen permeation behavior. From the aspect of process design, the membrane with an effective area of 16.6 cm2 could enrich 5% ethylene of 2000 ml min−1 up to 76, 80, and 82% at 573 K, 623 K, and 673 K, respectively with a hydrogen recovery ratio of >96% at a pressure difference of 1500 kPa.

Module configuration in CO 2 capture using Pd-based composite membranes

In this study, the effect of module configuration on the performance of Pd-based membrane devices was examined using a Pd-Au composite membrane deposited on a porous nickel support. Hydrogen permeation flux, recovery, and CO 2 enrichment were experimentally examined using two different modules. The module configuration that had a narrower space between the surface of the membrane and cover plate provided a large linear flow velocity of the gas mixture, which allowed for a reduction in the concentration polarization. The CO 2 enrichment capacity of the membrane module with a space distance of 0.4 mm was 4 times higher than the module with a space distance of 2.5 mm. In regards to the process design, the membrane with an effective area of 16.6 cm 2 could enrich 40% of the CO 2 at a flow rate of 2000 ml min −1 up to 87% with a hydrogen recovery ratio of >90% at 673 K and a total feed pressure of 1600 kPa.

A hydrogen purification and storage system using metal hydride

This work is to develop a new hydrogen purification and storage system for daily start and stop (DSS) operations. The new system enables us to minimize emissions of carbon dioxide by using compact and highly efficient fuel cells. The new system first removes carbon monoxide, which is poisonous to metal hydride, from reformed gas by using a special carbon monoxide adsorbent. After removing carbon monoxide, the reformed gas is introduced to a metal hydride bed to purify and store hydrogen. Some 100 NL/h Laboratory scale apparatus was operated in daily start and stop operations for 100 cycles for a total of 150 h with quite good efficiency. The new process has achieved an 83% hydrogen recovery ratio in one-month DSS operations.

A design study of a palladium diffuser for a D-T fusion reactor fuel clean-up system

In a recent study a palladium diffuser was shown to be feasible for a fusion fuel purification process which removes various impurities from plasma exhaust gases. In this study a mathematical model was developed to analyse the separation characteristics for a tubular palladium diffuser. Experiments with H 2-He mixtures were carried out to determine some parameters for an actual diffuser. The hydrogen recovery ratio is defined as a function of the tube dimensions and operating conditions for a diffuser with a high recovery ratio are estimated. A fuel clean-up system for a fusion reactor equipped with the diffuser was also designed.

核融合炉燃料精製系を対象としたパラジウム拡散器の解析と設計

Characteristics of tube-type palladium diffuser for a fusion reactor fuel cleanup system was analyzed with mathematical models. It was proved that a diffuser can recover most of tritium from plasma effluent gas. Calculations gave the profiles of concentration and flow rate of hydrogen in the diffuser. Hydrogen recovery ratio was described as a function of axial dispersion coefficient and feed gas flow rate.Based on the results, dimensions and operating conditions of the diffuser can be estimated. A diffuser for fuel cleanup system was designed under the conditions of Tritium Systems Test Assembly (TSTA) at Los Alamos National Laboratory.