Higman Chris Gasification (Газификация угля)
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350
Gasification
logy suppliers have their own strict safety regulations, but also trade associations
such as Compressed Gas Association (CGA), British Compressed Gas Association
(BCGA), and European Industrial Gas Association (EIGA), in which these companies
and other major operators of oxygen systems are represented, publish codes of practice
based on the joint experience of all their members.
Many substances such as oils and grease will combust spontaneously in the
presence of pure oxygen. The energy of impact of small particles on many
metals is sufficient to cause ignition. Fires initiated by both these causes are
sufficient to ignite the primary material of construction. The principle means of
combating these dangers lies in meticulous cleaning of the system prior to the
introduction of oxygen. All safety guidelines for oxygen systems include
recommendations for cleaning and inspection after cleaning, such as CGA
publication G-4.1.
An important aspect of safety precautions for oxygen service is material selection
and system geometry. Materials are selected to keep the ignitability of the material and
its capability of sustaining a fire in an oxygen atmosphere to a minimum. Typically,
copper-based materials (e.g., Monel) or stainless steels are used in high-pressure
noncryogenic systems. Inside the coldbox, where low temperature suitability is also
a criterion and pressures are limited, aluminum is also used. For pressures up to 40
bar, carbon steel may also be used. Cleaning in such applications is, however,
extremely important.
System geometry is also important. Velocities in oxygen lines are generally kept
low as a measure to limit the energy release on impact of any particles in the system.
An additional measure to limit the ignition risk is to avoid sharp bends in piping
where turbulence can increase local velocities much above these limits. For this
reason also much attention is required to the design of valving and piping at pressure
letdown stations.
An additional approach to safety in oxygen systems is to incorporate design
features, which ensure that personnel is not put at risk and that any material damage
in the event of a fire is kept to a minimum. This type of precaution is taken with
oxygen compressors, which are enclosed by a fireproof wall. There is an extensive
monitoring system that, on detection of a fire risk, will cause the machine to be
stopped, depressurized, and flooded with nitrogen (e.g., EIGA code of practice).
The cooling water circuit for intercooling is usually a closed-circuit system to avoid
any potential corrosion and subsequent leaks on the intercoolers.
An important safety aspect to consider is the quality of the air entering the air
separation unit. Modern molecular sieve PPUs will generally remove heavy
hydrocarbons present in the air. Cases are known where the concentration of
hydrocarbons in the atmosphere increased substantially over the life of the ASU and
overloaded an internal hydrocarbon filter inside the coldbox, breaking through into
the oxygen-rich environment of the LP column. In one case known to us, results of
ethylene leakage from a nearby plant were detected in time and the filter was
enlarged to cope with the new air quality. In another, the mechanism was more
complicated and an explosion resulted (van Hardeveld et al. 2001). Such incidents
Economics, Environmental, and Safety Issues
351
do, however, illustrate the need to specify the feed air quality conservatively and
with an eye to future developments.
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Amik, P., and Dowd, R. “Environmental Performance of IGCC Repowering for Conventional
Coal Power Plants.” Paper presented at Gasification Technologies Conference, San Francisco,
October 2001.
Appl, M. Ammonia: Principles and Industrial Practice. Weinheim: Wiley VCH, 1999.
Beecy, D. “U.S. Carbon Sequestration RD&D Program.” Paper presented at Gasification
Technologies Conference, San Francisco, October 2002.
BP. BP Statistical Review of World Energy. London: BP PLC, June 2002.
Chang, R., and Offen, G. “Mercury Control Options.” Modern Power Systems (November
2001).
Clayton, S. J., Siegel, G. J., and Wimer, J. G. “Gasification Technologies: Gasification Markets
and Technologies—Present and Future: An Industry Perspective.” U.S. DOE Report DOE/
FE-0447, U.S. DOE:July 2002.
Compressed Gas Association. “Cleaning Equipment for Oxygen Service.” Publication G-4.1,
4th ed. Arlington, VA, 1996.
Coste, C., Rovel, J. M., and George, J. M. “Effluent System in View of Both Zero Discharge
and Hazardous Solid Waste Minimization.” Paper presented at VGB Conference, Buggenum
IGCC Demonstration Plant, Maastricht, November 1993.
European Industrial Gas Association. Centrifugal Compressors for Oxygen Service. Code of
Practice. IGC Doc 27/01/E Brussels: EIGA, 2001.
Forte, R., Porter, F., Tavoulareas, E. S., and Ratafia-Brown, J. “Coal Gasification and Air
Emissions.” Paper presented at 19th Annual International Pittsburgh Coal Conference,
September 2002.
Geertsema, A., Groppo, J., and Price, C. “Demonstration of a Beneficiation Technology for
Texaco Gasifier Slag.” Paper presented at Gasification Technologies Conference, San
Francisco, October 2002.
Greil, C., Hirschfelder, J., Turna, O., and Obermeier, T. “Operating Results from Gasification
of Waste Material and Biomass in Fixed Bed and Circulating Fluidized Bed Gasifiers.”
Paper presented at IChemE Conference, “Gasification: The Clean Choice for Carbon
Management,” Noordwijk, April 2002.
Hannemann, F., Schiffers, U., Karg, J., and Kanaar, M. “V94.2 Buggenum Experience and
Improved Concepts for Syngas Application.” Paper presented at Gasification Technologies
Conference, San Francisco, October 2002.
352
Gasification
Higman, C. A. A. “Gasification: An Indian Perspective.” Paper presented at IChemE Confer-
ence “Gasification: The Gateway to a Cleaner Future,” Dresden, September 1998.
Higman, C. A. A. “Methanol Production by Gasification of Heavy Residues.” Paper pre-
sented at IChemE Conference, “Gasification: An Alternative to Natural Gas,” London,
November 1995.
Higman, C. A. A. “Perspectives and Experience with Partial Oxidation of Heavy Residues.”
Paper presented at AFTP Conference, “L’Hydrogène, Maillon Essentiel du Raffinage de
Demain,” Paris, 1994.
Hrivnak, S. “Fine-Tuning to Improve Availability and Reliability of Coal-Based Gasification.”
Paper presented at Gasification Technologies Conference, San Francisco, October 2001.
Jones, R. M., and Shilling, N. Z. “IGCC Gas Turbines for Refinery Applications.” Paper
presented at Gasification Technologies Conference, San Francisco, October 2002.
Koss, U., and Meyer, M. “Zero Emission IGCC with Rectisol Technology.” Paper presented
at Gasification Technologies Conference, San Francisco, October 2002.
Lewandowski, D., and Gray, D. “Potential Market Penetration of IGCC in the East Central
North American Reliability Council Region of the U.S.” Paper presented at Gasification
Technologies Conference, San Francisco, October 2001.
O’Keefe, L. F., and Strum, K. V. “Clean Coal Technology Options—A Comparison of IGCC vs.
Pulverized Coal Boilers.” Paper presented at Gasification Technologies Conference, San
Francisco, October 2002.
O’Keefe, L. F., Weissman, R. C., DePuy, R. A., Griffiths, J., East, N., and Wainwright, J. M.
“A Single Design for Variable CO
2
Capture.” Paper presented at Gasification Technologies
Conference, San Francisco, October 2001.
Ricketts, B., Hotchkiss, R., Livingston, B., and Hall, M. “Technology Status Review of
Waste/Biomass Co-gasification with Coal.” Paper presented at IChemE Conference,
“Gasification: The Clean Choice for Carbon Management,” Noordwijk, 2002.
Rutkowski, M. D., Klett, M. G., and Maxwell, R. C. “The Cost of Mercury Removal in an
IGCC Plant.” Paper presented at 19th Annual International Pittsburgh Coal Conference,
September 2002.
Schaub, G., and Unruh, D. “Synthetische Kohlenwasserstoff-Kraftstoffe und Minderung
fossiler CO2-Emissionen.” VDI-Berichte Nr. 1704, 2002.
Schmidt, W. P., Winegardner, K. S., Dennehy, M., and Castle-Smith, H. “Safe Design and
Operation of a Cryogenic Air Separation Unit.” Paper presented at AIChE Annual Loss
Prevention Symposium, Houston, April 2001.
Schwalb, A. M., Withum, J. A., and Statnick, R. M. “The Re-evolution of Mercury from Coal
Combustion Materials and By-Products.” Paper presented at 19th Annual International
Pittsburgh Coal Conference, September 2002.
Shell. Venster. The Hague (November/December 2002), p. 9.
Economics, Environmental, and Safety Issues
353
Simbeck, D. “Overview of Climate Change Policy and Technical Developments.” Paper
presented at Gasification Technologies Conference, San Francisco, October 2002.
Trapp, W. L. “Eastman and Gasification: The Next Step, Building on Past Success.” Paper
presented at Gasification Technologies Conference, San Francisco, October 2001.
U.S. Department of Energy. “Mercury Emissions Control.” Available at: www.netl.doe.gov/
coalpower/environment/mercury/description.html, January 2003.
U.S. Department of Energy. “Gasification Markets and Technologies: Present and Future.”
Report DOE/FE-0447, July 2002.
U.S. Environmental Protection Agency. “Inventory of Greenhouse as Emissions,” April 2002.
U.S. Department of Energy. “The Tampa Electric Integrated Gasification Combined-Cycle
Project: An Update.” U.S. DOE Topical Report No. 19, July 2000.
van der Burgt, M. J., Cantle, J., and Boutkan V. K. “Carbon Dioxide Removal from Coal-
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van Hardeveld, R. M., Groeneveld, M. J., Kehman, J.-Y., and Bull, D. C. “Investigation of an
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van Liere, J., Bakker, W. T., and Bolt, N. “Supporting Research on Construction Materials and
Gasification Slag.” Paper presented at VGB Conference, “Buggenum IGCC Demonstration
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Weigner, P., Martens, F., Uhlenberg, J., and Wolff, J. “Increased Flexibility of Shell Gasification
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355
Chapter 10
Gasification and the
Future
The future of gasification is intimately intertwined with the future of energy and
energy policy. It is generally recognized that human development cannot continue to
base its economy on fossil fuels in the present manner forever, even if viewpoints on
the timescale do diverge, sometimes dramatically. This viewpoint is put most
strongly by the advocates of what is called the “hydrogen economy.” There is no
doubt that the use of hydrogen in combination with fuel cells as a transport fuel will
improve the microclimate of our conurbations significantly through the elimination
of CO
2
, NO
x
, CO, and hydrocarbon emissions from motor vehicles. And this is a pros-
pect that could become reality within the next 20 years. However, it is our opinion
that those proponents, who present the hydrogen economy as a solution to the CO
2
emissions or “greenhouse gas” issue, overstate their case. The hydrogen that we will
use in our fuel cells is not ready and waiting for us to collect. It is chemically locked
into other substances, the principle of which are water and to a lesser extent natural gas.
The issue remains, therefore, how to unlock this hydrogen and make it available in a
useable form. There are essentially three routes to hydrogen production: electrolysis of
water, steam reforming of natural gas, and gasification—whereby the fuel for the gas-
ification can be anything from coal to biomass. Thus, as can be seen from Table 10-1,
unless the power for electrolysis is generated without CO
2
emissions, hydrogen
production is inevitably associated with CO
2
production. Furthermore, it has to be
recognized that with the possible exception of nuclear energy, no CO
2
-free power-
generation technology is in the medium-term going to produce hydrogen in the quanti-
ties required to supply our transport needs. We therefore need to look at the potential
for a reduced CO
2
technology to help us on the way to a “no carbon” energy future.
It is our opinion that in the transition between fossil fuels and a fully “renewable
world,” gasification can play an important role. First, in the move toward a hydrogen
economy, one can expect that the hydrogen will be produced directly from fossil
fuels rather than by electrolysis. Furthermore, during this transition period the
implementation of polygeneration units producing both power and hydrogen will
allow a gradual change over from the former to the latter. This is the only way in
which an investment in power generation can be utilized for hydrogen production at
356
Gasification
moderate cost (Simbeck and Chang 2002). Second, gasification is a key technology
for more efficient power generation from coal and heavy oils with the best environ-
mental performance. And third, gasification provides the best option for producing
concentrated carbon dioxide streams that may have to be sequestered during the
transition in order to reduce the emission of greenhouse gases.
Of course, the above remarks are not restricted to coal but apply to the gasification
of any fossil fuel. Furthermore, they apply also to what may in the very long-term
become the most important feedstocks, biomass, and waste—that may, in a totally
“sustainable future,” have to take over the role of today’s fossil fuels.
What is seldom mentioned is that even in a “sustainable world” not only energy is
required but also carbon for organic chemicals including plastics. Although gasification
of waste may supply part of this requirement, the make-up will have to come from
biomass, which in this idealized “sustainable world” model is the only allowable
source of concentrated carbon (van der Burgt 1997). The only way to produce
organic chemicals from waste and biomass is first to gasify them in order to make
synthesis gas. At present, there is no process available to do this efficiently, as all
biomass and waste gasification processes to date have been developed for producing
fuel gas and power. Hence, although in a more renewable world hydrogen (by elec-
trolysis) and electricity may be available, gasification of waste and biomass—
directly or indirectly via bio-oil—are at least required to make synthesis gas for
organic chemicals. The first generation of downstream technologies to allow the use
of syngas (via methanol) as an alternative source for ethylene and propylene instead
of the conventional naphtha cracking is already in the demonstration stage (UOP
1997; Holtmann and Rothaemel 2001).
We therefore conclude that gasification can and will have an important role to
play in the coming decades, both for power generation and for the production of
bulk chemicals. In the more distant future it may also develop to become an important
source of base materials for all organic chemicals. It is hoped that this book will
contribute to the development of a better understanding of gasification processes
and their future development.
Table 10-1
CO
2
Emissions for Hydrogen Production Technologies
Technology kg CO
2
Emissions per Nm
3
H
2
Electrolysis with conventional
coal combustion 2.6
Biomass gasification 1.7–2.0
Coal gasification 1.0–1.4
Steam reforming of natural gas 0.8
Electrolysis with nuclear power 0
Gasification and the Future
357
REFERENCES
Holtmann, H.-D., and Rothaemel, M. “A Cost-Effective Methanol to Propylene Route.”
Petroleum Technology Quarterly (Autumn 2001).
Simbeck, D., and Chang, E. “Hydrogen Supply: Cost Estimate for Hydrogen Pathways—
Scoping Analysis.” National Renewable Energy Laboratory report. NREL/SR-540-32525
(July 2002).
UOP. “UOP/Hydro MTO Process: Methanol to Olefins Conversion.” UOP Company leaflet,
1997.
van der Burgt, M. J. “The Role of Biomass as an Energy Carrier for the Future.” Energy
World 246 (February 1997).
359
Appendix A
Companion Website
For those interested in following up on some of the ideas expressed in this book, we
have set up a website, www.gasification.higman.de, which includes both programs
for typical gasification calculations and a literature data bank. The content of the
website at the time this book went to press covers the following:
Computer Programs
Gasify.exe performs calculations for gasification for coal, oil, and natural gas. It is
an equilibrium calculation based on the information contained in Chapter 2. There is
a wide selection of calculation modes, such as fixed reactant quantities with variable
gasification temperature, fixed gasification temperature with variable oxygen demand,
and others.
Proxult.exe will convert proximate and ultimate coal analyses between “as
received” (ar), “moisture free” (mf), “ash free” (af), and “moisture- and ash-free”
(maf) basis, as described in Section 4.1. Further, LHV and HHV on any basis may
be converted into each other. In the absence of heat of combustion data, the heating
value will be generated using the proximate and ultimate analyses.
Heatloss.exe will calculate the loss of heat in a membrane wall under different internal
conditions (slagging/nonslagging) using the criteria described in Section 6.4.
Quench.exe provides a means of back-calculating the temperature at which the CO
shift reaction and the CO
2
methane reforming reaction have frozen during cooling,
as described in Section 6.8.
Viscos.exe estimates the viscosity of residual oil fractions as described in Section
4.2.1.
All these programs are executable files and can be downloaded for use by owners of
this book. Help files include a fuller description of the theoretical background than
contained in the book.