This webcast features perspectives from operational technology (OT), information technology (IT) as well as the general industry outlook, to provide attendees insight into the challenges utilities are facing today as well as a holistic view into smart grid strategies to more...
Grid threats increase daily - from foreign foes, terrorists, criminals and hackers. Utilities are tasked with guarding against a rising tide of potentially disruptive intrusions into their power grid and electronic networks. What will it take to keep the power more...
Monday Jun 24, 2013
- Tuesday Jun 25, 2013 -
Philadelphia, Pennsylvania - USA
Data Informed´s Marketing Analytics and Customer Engagement provides marketing, sales, and customer support managers with the information they need to create an effective data-driven customer strategy. more...
We know you have something to say!
There is an immediate need for articles on
the hot topics in the Power Industry!
EnergyPulse, like no other publication,
also provides a means for our readers to
immediately interact with experts like you.
Long distance pipelines carry natural gas from the wells to the markets across North America and much of Europe. The density and flowrate of the gas is maximized by keeping it at high pressure as well as at low temperature. Pumping stations along the pipelines are equipt with massive heat exchangers that cool the gas after it has been re-pressurised. The engines that drive some of the pumping equipment burn natural gas and also reject a tremendous of waste heat. During summer it may be possible to use heat from both these sources to generate electric power from an engine that operates on low-grade heat (temperature difference between ambient air and the peak temperature of the natural gas).
There are multiple uses for this heat during cold winter months in northern climates. It can be used to heat nearby buildings and even provide district heating for small and remote northern communities. It can aslo be used to energise engines that can operate from low-grade heat. The table below provides data from a pumping station. It is based on the pressure ratio of the pump (85% isentropic efficiency) and temperature to which the gas will rise. The ambient air temperature and the temperature of the natural gas are assumed to be 40-degrees F (4.4445-degrees C). The heat exchangers nomimally operate at 80% effectiveness.
There are occasions when the ambient temperature in northern locations can drop to below zero degrees F (-17.777-degrees C). The table changes as follows:
Natural gas has a density of 0.5979-pounds per cubic foot at a pressure of 200-psia and temperature of 40-degrees F. A million cubic feet per hour were pumped through the pipeline would weigh 597,944-pounds. A heat exchanger at the pumping station that rejects 100-BTU/lb of heat would process 59,794,456-BTU of heat per hour from a high temperature of over 200-degrees F. It would be possible to transfer this heat into district heating systems in northern communities during winter months.
There are locations where the communities may be too small to use all the heat that could be made available to it from pumping stations during winter. The difference in temperature between the newly re-pressurised gas and the ambient winter air would be sufficient to energise a low-heat engine. Honeywell’s Genetron division now supplies a chemical that can be used in such an engine. Such an engine could fulfill all or part of the power generation requirements of a northern remote community during winter.
Pressure in natural gas pipelines had to be reduced prior to the gas being distributed to customers. Power can be extracted from the pressure differential in natural gas pipelines where the gas pressure needs to be reduced. A previous article by this author covered that possibility. The gas that exists a pressure reduction is notable cooler than the ambient air temperature. The specific heat of natural gas is about twice that of air (0.5099 vs 0.24) and there are locations where air conditioning and cooling can be extracted from pressure reduction stations.
The following table illustrates the cooling effect of a turbine (isentropic efficiency of 90%) in pressure reduction station on the natural gas (at 100-degrees F) and over a range of pressure engine ratios.
About 100,000-pounds per hour of natural gas could pass through the engine of a pressure reduction station with a pressure ratio of 5:1. The natural gas passing through the turbine would yield a cooling effect of some 4,207,000-BTU/hour. This cooling effect could be distributed through the pipelines of a district heating system during hot summer months. An alternative would be to use the cooling effect in a commercial refrigeration system such as a food terminal. The cooling effect on the natural gas could also serve as the heat sink of an engine that would operate from low-grade heat. The heat source would be atmospheric heat or concentrated solar heat.
Conclusions
Natural gas pumping stations produce thermal energy that is rejected so as to maximize the amount of gas that can be pumped through long distance pipelines. The companies earn revenue from the sale of the gas. There is much downstream thermal energy that is available from the pumping stations throughout the year. There are productive uses to which that heat energy may be put.
The pressure of natural gas needs to be reduced prior to being distributed to the final customers at low pressure (3-psi or 17.7-psia). Power can be generated at the pressure reduction stations from the pressure drop. The temperature of the natural gas would drop as it passes through the turbines at a pressure reduction station. This drop in temperature can be used for air conditioning purposes or as a heat sink for an engine that runs on small differences in temperature.
For information on purchasing reprints of this article, contact sales. Copyright 2013 CyberTech, Inc.
Where it's feasible, I wouldn't disparage efforts to recapture through CHP a portion of the considerable energy that's expended in pumping NG through pipelines. Somebody can supply better figures, but I believe it's on the order of 3% of all gas usage in the country?
However, I don't think there's much prospect for using waste heat from the gas compression to generate electricity. For one thing, the capital cost of low delta heat engines is high for the limited output they're able to produce. But even if it were cost-effective to install them at pumping stations, the most sensible way to use their output would be to supply a portion of the mechanical power to the pumps. That would reduce the fraction of pipeline gas that had to be bled off to power the pump motors.
A more cost-effective way to improve pumping efficiency would probably just be to employ pumps with more stages and larger heat exchangers running at lower temperatures. That gives a closer approximation to isothermal compression, with the tradeoff of higher capital equipment cost.
Dr. Hussain Alrobaei 6.26.07
A sound of energy policy call for rational utilization of all available energy sources, minimizing the pollution and fuel consumption for heat, mechanical and electrical power production. Novel concepts are needed for using waste heat and other forms of thermal energy. From this standpoint the repowering and modification of industrial gas turbine units for mechanical drive applications are often considered an effective way for increasing the economical effectiveness of Natural Gas Compression Plants ( NGCP ). Visualizing the importance of combined cycle and Multi Effect Distillation (MED) process in industrial cogeneration plants, the recent study was undertaken to include the following proposed schemes for repowering and modification of NGCP: Combined Mechanical Power Plant; Combined Cogeneration Mechanical Power Plant ; Combined Mechanical and Electrical Power Plant; Combined Cogeneration Mechanical and Electrical Power Plant. The main object of the study is to discuss the economical and environmental effectiveness of duel and triple power generation in proposed schemes of NGCP The Study result shows : 1.The effectiveness of proposed schemes for modification and repowering of NGCP. These technologies will help in optimizing the consumption of fossil fuel and minimizing the environmental impact. For the case study (Combined Mechanical Power Plant) the economical effect amount 365 ton fuel/year for each MW design mechanical energy of NGCP and the corresponding decrease in exhaust gases emissions (Nitrogen oxides (NOx) 1.16 ton/year. MW, Carbon dioxides (CO2) 767.74 ton/year. MW). 2. Modification and repowering of NGCP for combined seawater desalination and mechanical power generation (Combined Cogeneration Mechanical Power Plant) will be increase the economical and environment effectiveness in section 1 by 34.8 % besides produces about 44072 ton/year.MW of distilled water. 3. Implementation of triple power generation in technological schemes of NGCP could improve the economical and environment effectiveness in section 1 by 43 % beside produce about 46965 ton/year.MW of distilled water and 1739 Mw.hr/year.MW of high – voltage electricity. 4. Low temperature MED is the unique desalination process enabling water production from very low steam pressure ( 0.3 bar ). This will improve the economical effectiveness of industrial cogeneration plants by producing more power in steam turbine. Detailed calculations of MED plants shows that for proposed schemes of NGCP 8 effects will be need.
David McGee 6.26.07
This is not a new idea to the gas compression industry. With a 5 year payback though it isn't high on everyone's list. Someday it will be. Another problem is that Gas compression stations are generally located "out of the way" so using the last of the heat for district heating is problematic. Piping the heat transfer fluid to a user is expensive and often the losses in transit would be excessive. For some of what is in place, here are some links and a brief on one station here in Louisiana that was severely effected by Hurricane Katrina. Being able to get up and running without grid electricity would have speeded up recovery. http://www.wowenergies.com/applications.html http://www.ormat.com/our-businesses/recovered-energy/ http://www.chpcenterpr.org/wasteheat2power06/presentations/Day2-Feb16/Session2/Day2-Rouse-3.pdf Enterprise Products Operating LP’s Neptune Gas Plant in Centerville, La, produces 100% of the facility’s power needs, plus some for sale, with a 4.5-MW ORC serving two GT-driven compressors. The saving associated with self generation, combined with income from power sales, reportedly will pay back the initial investment in less than five years.
Ron Rebenitsch 6.26.07
One example: Basin Electric Power Cooperative worked with Ormat Technologies and the Northern Border Pipeline to develop four waste heat recovery systems on the compressors for the Northern Border Pipeline. Each of those systems captures the waste heat from the gas turbine driving the pipeline compressors, then uses that heat to generate a net power output of about 5.5 MW per site for a total of about 22 MW. The earlier comment about remote sites accurately reflects this situation. Over 15 miles of transmission interconnect was required for those four units. Another four sites are now planned.
Paresh Trivedi 7.10.07
I like that idea...since 2005....I looking forward that at least we have one Gas Utility with this PiP™ power generation & Pressure into Power™ energy reclamation.... May be rich city Government like New York will use this technology one day!!!
PiP™ power generation & Pressure into Power™ energy reclamation English Portugu?s Espa?ol
The latest solution from Dresser for North American gas pressure regulation, distribution and energy markets.
Click on image for animation FULL SCREEN
Play PiP Expansion Engine Video (52 MB)
Documents:
Introduction Brochure
List of Installations & some Technical Data Pressure into Power™ energy reclamation simultaneously generates up to 1.5 MWe per unit while acting as a pressure reducing gas regulator. It is not a replacement for traditional pressure regulating stations, but instead runs in parallel. It is the next generation of gas pressure regulation and recovers potential energy from pressurized gas. Power generation and gas pressure regulation is achieved by expanding and flowing the gas, but without any internal combustion or consumption of gas. It acts like a compressor in reverse.
Simultaneous to generating power, PiP™ energy reclamation can be configured to produce up to 420 tons of refrigeration per hour - again, without any consumption of gas.
This system is modular and configurable: from 1 cylinder up to 6 cylinders per unit, ranging from 250 kWe up to 1.5 MWe.
