Hydrogen Recovery and Recycling
Today’s high cost of hydrogen, driven by increasing costs of production and delivery, has created a financial incentive for the heat-treating industry to consider hydrogen-recovery alternatives in order to reduce costs and improve the efficiency of operations. A hydrogen-recovery and recycling device offered by H2 Pump (manufacturer) can efficiently and cost-effectively recover and recycle by-product or unconsumed hydrogen, creating an opportunity to return significant value to heat-treat operations. Instead of venting or burning by-product hydrogen, the H2 Pump device can recover, purify and recycle up to 90% of the hydrogen discharged from hydrogen-containing atmospheres (depending on the composition of your particular effluent gas stream). An additional benefit of the technology is that it offers an opportunity to manage emissions of hydrogen and greenhouse gases previously thought to be unprocessable due to the residual hydrogen content.
Hydrogen recovery and recycling is not a new concept, but until the manufacturer developed this technique, most recovery and recycling options have been limited to conventional mechanical approaches – mechanical compressors combined with pressure-swing absorption units. The H2 Pump technology can offer significant advantages compared to the conventional approaches, including an ability to recover, purify and pressurize hydrogen in a single stand-alone device. Other significant advantages include a near-infinite turndown ratio, high tolerance to impurity gases, high reliability with few moving parts, small footprint and low capital and operating costs.
Hydrogen-Recovery SystemThe H2 Pump “3-in-1” hydrogen-recovery system combines electrochemical technology with a proprietary design to efficiently separate hydrogen from other gases, purify it and “pump” it back into the feed stream of the heat-treating or other site-specific process.
Electrochemical hydrogen-recovery and pumping technology (EHP) utilizes a process whereby hydrogen is actively removed from a mixed feed gas (furnace exhaust) producing a high-purity hydrogen-gas stream while the rest of the exhaust gases passes through as waste. The electrochemical subsystem performs the actual separation and pumping process but is only a portion of a complete system (Fig. 1).
A power subsystem is required to deliver the DC power to the pump (in order to drive hydrogen flow), maintain proper operating temperature and power the balance of the plant. A controls subsystem is required to manage the power and pumping subsystems.
H2 Pump’s hydrogen-recovery system is being designed as a turnkey system that can integrate seamlessly into a heat-treating operation with an ability to cost-effectively scale down (or up), enabling effective integration with a single furnace or a series of furnaces, and thereby minimizing infrastructure changes. In many cases, simple plumbing is all that is required.
Electrochemical Membrane TechnologyElectrochemical membrane technology used in hydrogen pumps was first developed in the 1960s, and H2 Pump has reintroduced the concept of EHP by taking advantage of 21st-century materials. The concept is simple, requires little power and can pump hydrogen to high pressures. The pump is operated in an electrolytic mode meaning that power is required to “drive” hydrogen through a membrane. In the electrochemical process, hydrogen is introduced into the anode chamber of the cell where it is oxidized on an electrode. A DC power supply provides the electrical potential for electrons to migrate from the anode to the cathode and drive the protons from the anode through a proton-exchange membrane to the cathode. Electrons and protons recombine at the cathode chamber to produce pure hydrogen (Fig. 2).
The hydrogen flux – pumping rate – is determined by the number of cells within the pump, the size of each cell and the electrical current applied. One molecule of hydrogen (H2) consists of two electrons and two protons. For every two electrons that migrate to the cathode (via the power supply), two protons are driven through the membrane to the cathode. The result is one molecule of H2 being “pumped” from the anode to the cathode side of the cell.
I = NF(dn/dt)
where: I = current, N=2 electrons, F = Faraday’s constant (~96,500 amp-sec) and dn/dt = moles of hydrogen per second. Using this relationship it can be shown that 0.015 cubic feet per hour (CFH) of hydrogen is pumped for each cell and each amp of current. Increasing the number of cells within the pump and/or the electrical current will increase the rate of hydrogen pumped (Fig. 3).
The resistance to proton and electron flow, the change in hydrogen pressure from anode to cathode chambers and the gas mixture from which the hydrogen is being separated determines the voltage required to “pump” hydrogen. Increased resistance to migration (proton and electron) or increased current results in increased voltage. In the case of pure hydrogen, the pumping module is capable of operating at greater than 90% efficiency (with respect to the lower heating value of hydrogen). For exhaust streams containing high hydrogen content, the voltage per cell is typically less than 50mV.
Pressurization is accomplished isothermally, meaning that the device will “pump” hydrogen without the generation of heat, thereby reducing the inefficiencies associated with hydrogen compression.
- Purification – Inherent purification of the effluent stream is the result of separating hydrogen from the other by-product gases. Secondary gases, particularly carbon-based gases such as methane, carbon monoxide and carbon dioxide as well as water vapor, do not poison or otherwise harm our device as they may in many conventional systems. Hydrogen with purity as high as 99.99% has been separated from mixed gas streams initially containing as little as 30% hydrogen.
- Scalable – Easily scaled down (or up) in order to meet a variety of hydrogen flow requirements.
- Low Cost – Simple, low-cost components with few moving parts result in high efficiency and low operating and maintenance costs. The system can be installed at the point of use, thereby minimizing infrastructure modifications. The power required to operate the system is minimal, and the value proposition can be compelling (Fig. 5).
Value PropositionThe cost of delivered hydrogen is significant with production, delivery and storage all contributing to its high cost (approaching $25 per 100ft3 for many). Recycling (and purifying) hydrogen with proprietary electrochemical membrane technology can offer heat-treat operations an opportunity to recycle upwards of 90% of their waste hydrogen and substantially reduce the cost of their operations by reducing hydrogen feedstock requirements. The value proposition for recycling hydrogen is based primarily on an ability to cost-effectively recover, process and direct the newly processed hydrogen back to the original feed stream or to another application where the heat and/or energy value can be used.
Most of the hydrogen used for heat treating and other industrial processes is produced from natural gas (by steam reforming), and with 50 million tons of annual worldwide hydrogen production, the volume of natural gas and amount of energy required to produce hydrogen is significant and rising. As the cost of hydrogen increases due to these rising production costs, the ability to recover and reuse up to 90% of your waste hydrogen, at a fraction of the cost for a new supply, is compelling.
The manufacturer’s system design is simple and has few moving parts. As such, operating costs are dominated by the power required to facilitate the process of “driving” protons through a membrane (Fig. 2). The amount of power required to facilitate hydrogen separation is variable depending on the composition of the effluent stream, but the power requirement generally increases as the composition of hydrogen decreases (assuming a constant volume of hydrogen). For effluent streams containing less hydrogen, the power requirement increases and is dependent on the actual composition of the secondary gases. Figure 5 quantifies the annual cost of electricity for three different mixed-gas compositions.
SummaryAn electrochemical hydrogen-recovery and pumping system offered by H2 Pump can efficiently and cost effectively recover and recycle by-product (waste) hydrogen, creating an opportunity to return significant value to heat-treat operations. This hydrogen-recovery system is being designed as a turnkey system that can integrate seamlessly into any heat-treating operation using a modular approach that provides an ability to scale down, or up, in order to meet specific hydrogen requirements for any number of furnace and heat-treating processes. Unlike current mechanical technology, the system can be effectively integrated with a single furnace, or a series of furnaces, in order to minimize infrastructure changes. IH
For more information: If you would like to learn more about this process for separating hydrogen, or if you would be interested in becoming a demonstration partner, please contact H2 Pump LLC by e-mailing us at Info@h2pumpllc.com or calling 518-783-2241.
Additional related information may be found by searching for these (and other) key words/terms via BNP Media SEARCH at www.industrialheating.com: hydrogen recycling, furnace atmosphere, hydrogen recovery, electrochemical, effluent stream