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ChevronTexaco: An Approach to Distributed Hydrogen Production

Clearly, one of the major requirements for a hydrogen-based transportation system is the production of the hydrogen itself.

Cttv_reformer

At the recent Hydrogen Expo USA in Washington, ChevronTexaco Technology Ventures (CTTV) and Modine Manufacturing presented a paper outlining their development of an innovative, distributed, natural-gas-fed, smaller scale Steam Methane reformer for hydrogen production.

In principle, ChevronTexaco believes that development of an economic distributed hydrogen infrastructure is fundamental to the success of a hydrogen economy and the commercialization of fuel cells in both transport and stationary power applications.

The new compact reformer design features mechanical as well as thermal integration of the steam reforming, catalytic oxidizer, and water-gas shift reactions in a single vessel.  The design is thermally neutral and requires no external cooling and no control loops, and improves the energy balance of an SMR system.

The production design target for the system is approximately 40kg of hydrogen per day—enough to service a neighborhood’s worth of hydrogen-fueled cars.

The company concludes that its design has the potential to surpass the near-term targets set by the DOE for hydrogen cost: $13.94/GJ or $1.98/kg by this year. CTTV calculations yield a total reforming cost of $12.95/GJ or $1.84/kg.

However, despite the energy and economic improvements delivered through this design, the compact reformer still operates at a negative energy balance (i.e., more energy is used in producing the hydrogen than is obtained from the hydrogen), and hydrogen costs linked to the cost of natural gas seem bound to rise steeply.

Natural gas is only a short-term option.

—Jack Johnston, ExxonMobil, GCEP presentation

CTTV used a hypothetical cost of $4.00/MMBTU of natural gas in its calculations. The spot price for natural gas at Henry Hub for the week of 13–20 April 2005 was, by contrast, $7.10/MMBTU. The industrial market hasn’t seen $4.00 natural gas since 2002.

This doesn’t reflect a problem with the CTTV design—as noted above (and as we’ll explore a bit more below), it is energy- and cost-efficient within its class. It does, however, highlight the larger problem of Steam Methane Reforming as a process with natural gas as its feedstock for the production of hydrogen.

Some quick background first.

Hydrogen is prevalent on earth, but is usually bonded to carbon or oxygen—e.g., “hydrocarbon” fuels, biomass, or water. It takes energy to break those bonds. There are a variety of processes for this, with more under development.

The US already produces 9 million tons of hydrogen per year primarily for use in ammonia production, petroleum refining, and methanol production, with steam methane reforming accounting for 95% of that production. Globally, the figure is closer to 48%.

The DOE notes that 9 million tons of hydrogen would power 20–30 million cars.

The basic Steam Methane Reforming process uses steam to heat natural gas to approximately 850ºC over a nickel catalyst bed, yielding  a mixture of CO and H2O. The mixture is then cooled and catalyzed with steam again to yield pure hydrogen and CO2 (lots of CO2).

Goswami_h2_chart

At this point, SMR is the most cost-effective process for hydrogen production. That will change, as the projection of the cost curves of select processes and feedstocks plotted to the right from Dr. Yogi Goswami at the University of Florida shows. (Click to enlarge.)

Shown on this graph is the DOE target price for hydrogen produced from natural gas in 2010: $10.56/GJ or $1.50/kg. The DOE has higher-priced targets for other processes. 

Given the probable supply constraints with natural gas in the future, the cost outlook for natural gas may even shift further to the left—i.e., cost more, sooner.

There are a variety of process approaches that are being explored to reduce the energy imbalance in the production of hydrogen from natural gas, and to sequester the CO2 thereby generated. Little of that will be able to affect the cost aspect, however. That alone—should the price of natural gas continue to rise—may be enough to make this approach a non-starter in the medium- to long-term.

That also begs the question of where the 9 million tons (and rising) already spoken for in the US will come from, and how cost-effectively.

Gloom about the feedstock aside, the CTTV approach seems pretty interesting. The company’s key attributes for the reformer are:

  1. Safe, robust and reliable

  2. Low operating cost through improved fuel efficiency

  3. Low capital costs through reduced system components and controls complexity

  4. Manufacturable in high volumes

The process chemistry for small scale SMR is the same as in a large scale refinery, but the authors of the paper point out that there are severe economy-of-scale penalties.

Scaling the process down from larger systems results in greater heat losses that contribute directly to lower production efficiency, higher operating costs, and ultimately higher cost of hydrogen.  To address these challenges, the project approach aims at developing a small scale SMR that is: (1) thermally and mechanically integrated to maximize heat recovery, minimize heat loss, and minimize balance of plant components, (2) able operate at pressure required for purification step to minimize electrical power consumption, and (3) thermally balance to achieve passive temperature control and to minimize the number of process control loops.

Cttv2

The CTTV team combined all process reactions and necessary heat transfer steps into a single, unitized vessel assembly. Concentric fin-type heat exchangers coated with catalysts allow the heat generated by the endothermic oxidizing reaction to be directly transferred to the endothermic steam reforming reaction.

The paper asserts that the maximum reformer hydrogen production rate is 55 kg/day, or 7,810 GJ of energy. The maximum natural gas consumption rate to achieve that production is 145 kg/day, or 8,051.85 GJ. In other words—you’re still running a net negative energy ratio—more energy goes in than comes out. Better than typical SMR systems, but still at a deficit.

Resources:

Comments

richard schumacher

It may have some success in attracting R&D funds from of the DOE.

odograph

And when you "attract R&D funds" it becomes a profit center, right?

C. Scott Miller

The BRI Process can be adapted to produce Hydrogen or ethanol while cogenerating electricity in excess of that consumed. The feedstock is essentially any hydrocarbon source including agricultural, forestry, and urban waste, sewage, and/or fossil fuels. See http://www.brienergy.com/

Brook Porter

Negative net energy ratio? Are you suggesting there is such a thing as a positive net energy ratio? A perpetual motion device? How did you get into the position of writing on subjects of which you clearly have no understanding? Please consult someone with at least a competency in the field of science before publishing such statements...they do nothing put perpetuate misunderstandings about issues like energy. I for one care too much about such issues to let misstatements like this slide by without comment...

Mike

No, I’m not suggesting there is a perpetual motion machine. :-)

Clearly, I have done a poor job in conveying my point, which is really the point reflected in two lifecycle analyses from the National Renewable Energy Laboratory on different methods of hydrogen production: one for Natural Gas Steam Methane Reforming (NREL/TP-570-27637); the other for Wind Electrolysis (NREL/MP-560-35404).

From the LCA on Steam Methane Reforming:

On a life cycle basis, for one MJ of fossil fuel consumed by the system, 0.66 MJ of hydrogen is produced (LHV basis). This reflects the fact that because natural gas is a non-renewable resource, more energy is consumed by the system than is produced. This number also accounts for the upstream energy used in producing and distributing the natural gas and in producing the electricity required to operate the hydrogen plant. (Exec Summary, p2)

From the LCA on Wind Electrolysis:

The net energy ratio, defined in Table 6, provides another means of examining the system’s energy balance. It illustrates how much energy is produced for each unit of fossil fuel energy consumed. Because of the nature of the wind/electrolysis system, the net energy ratio is greater than one indicating that the energy in the product hydrogen is greater than the fossil energy consumed. For every 13.2 MJ of hydrogen produced, 1 MJ of fossil energy must be consumed (LHV basis). (p4)

I used “negative” conceptually—as in you’re putting more fossil fuel energy into the process than the hydrogen energy produced, and hence, running negative on the account balance. To be precise in referring to the net energy ratio, yes, I should have said “less than one”.

chibuzor Albert

you need to create more information for your on line student.and also i will like to be a member of this organization

babaloo

very nice i lik site

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