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Handbook of Biomass Downdraft Gasifier Engine Systems~,y~mp-271-3022 DE88001135 March 1988 UC Category: 245

@uR

ENERGY RESEARCH INTECHNICAL LIBRARY

OCT

7 1988

This handbook has been prepared by the Solar Energy Research Institute under the U.S. Department of Energy Solar Technical Information Program. It is intended as a guide to the design, testing, operation, and manufacture of small-scale [less than 200 kW (270 hp)] gasifiers. A great deal of the information will be useful for all levels of biomass gasification. The handbook is meant to be a practical guide to gasifier systems, and a minimum amount of space is devoted to questions of more theoretical interest. We apologize in advance for mixing English and Scientifique Internationale (SI) units. Whenever possible, we have used SI units, with the corresponding English units following in parentheses. Unfortunately, many of the figures use English units, and it would have been too difficult to convert all of these figures to both units. We have supplied a conversion chart in the Appendix to make these conversions easier for the reader. Mr. Bill Nostrand, one of our very helpful reviewers, died in May 1985. Bill was number one in the ranks of those who became interested in gasification because of its potential for supplying clean, renewable energy. We all will miss him. The improvement of gasification systems will be noticeably slowed by his death. We dedicate this book to the Bill Nostrands of this world who will bring gasifier systems to the level of safety, cleanliness, and reliability required to realize their full potential. Thanks, Bill.

T. B. Reed and A. Das Golden, Colorado

A Product of the

0276A Division of Midwest Research Institute

Solar Technical Information Program Solar Energy Research lnstitute161 7 Cole Boulevard, Golden, Colorado 80401 -3393

Operated for the

U.S. Department of Energy

AcknowledgmentsSince it is impossible for one or two authors to realistically comprehend a subject from all viewpoints, we have solicited input from leading workers in the field. Early versions were sent to a number of investigators, and each was invited to comment on and supplement our effort. We therefore express our heartfelt thanks to the following reviewers for greatly enhancing the quality of the final product: Dr. Thomas Milne, Solar Energy Research Institute Dr. Bjorn Kjellstrom, The Beijer Institute, Sweden Dr. Thomas McGowan, Georgia Institute of Technology Dr. Hubert Stassen, Twente University, The Netherlands Mr. Matthew Mendis, World Bank Prof. Ibarra Cruz, University of Manila, The Philippines Mr. Bill Nostrand, New England Gasification Associates We take final responsibility for the contents and omissions, and extend our apologies to those workers whose work we may have unknowingly omitted.

Organization and UseA gasifier converts solid fuel to gaseous fuel. A gasifier system includes the gasification reactor itself, along with the auxiliary equipment necessary to handle the solids, gases, and effluents going into or coming from the gasifier. The figure below shows the major components of a gasifier system and the chapters in which they are discussed.

Gasifier Ch. 4, 5, 6

I

I

Gas measurement and cleaning Ch. 7, 8r

Flare Ch. 9, 12

I

IEngine (or combustor) Ch. 11

t

Whole system Ch. 9, 10

+

NoticeThis report was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor any agency thereof, nor any of their employees, makes any warranties, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof. Printed in the United States of America Available from: Superintendent of Documents U.S. Government Printing Office Washington, DC 20402 National Technical Information Service U.S. Department of Commerce 5285 Port Royal Road Springfield, VA 22161 Price: Microfiche A01 Printed Copy A07 Codes are used for pricing all publications. The code is determined by the number of pages in the publication. Information pertaining to the pricing codes can be found in the current issue of the following publications which are generally available in most libraries: Energy Research Abstracts (ERA);Government Reports Announcements and Index (GRA and I); Scientific and Technical Abstract Reports (STAR);and puhlication NTIS-PR-360 available from NTIS at the above address.

4.3 Indirect and Direct Gasification Processes . . . . . . . . . . . . . . . . . . 4.3.1 Indirect (Pyrolitic) Gasification . . . . . . . . . . . . . . . . . . . 4.3.2 Direct Gasification . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4 Principles of Operation of Direct Gasifiers . . . . . . . . . . . . . . . . . 4.4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.2 Operation of the Updraft Gasifier . . . . . . . . . . . . . . . . . . 4.4.3 Operation of the Downdraft Gasifier . . . . . . . . . . . . . . . . 4.4.4 Factors Controlling Stability of Gasifier Operation . . . . . . . . 4.5 Charcoal Gasification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.0 Gasifier Designs

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 5.2 Basic Gasifier Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 5.3 Charcoal Gasifiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ; . . . . . . . . . . 31 5.4 Charcoal versus Biomass Fuels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 5.5 The Crossdraft Gasifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 5.6 The Updraft Gasifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 5.7 The Imbert Downdraft Gasifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 5.7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32 5.7.2 Description of the Downdraft (Imbert) Gasifier . . . . . . . . . . . . . . . . . . . . . . . . . 33 5.7.3 Superficial Velocity. Hearth Load. and Gasifier Sizing . . . . . . . . . . . . . . . . . . . . . 35 5.7.4 Turndown Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 5.7.5 Disadvantages of the Imbert Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36 5.8 The Stratified Downdraft Gasifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 5.8.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 5.8.2 Description of the Stratified Downdraft Gasifier . . . . . . . . . . . . . . . . . . . . . . . . 38 5.8.3 Unanswered Questions About the Stratified Downdraft Gasifier . . . . . . . . . . . . . . . 40 5.8.4 Modeling the Stratified Downdraft Gasifier . . . . . . . . . . . . . . . . . . . . . . . . . . 42 5.9 Tar-Cracking Gasifiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 5.9.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 5.9.2 Combustion of Tars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 5.9.3 Thermal Tar Cracking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 5.9.4 Catalytic Tar Cracking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 5.1OSummary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .48 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49

6.0 Gasifier Fabrication and Manufacture 6.1 Introduction . . . . . . . . . . . . . 6.2 Materials of Construction . . . . . . 6.3 Methods of Construction . . . . . . 6.4 Sizing and Laying out the Pipes . . 6.5 Instruments and Controls . . . . . . 6.5.1 Temperature . . . . . . . . 6.5.2 Pressure . . . . . . . . . . 6.5.3 Gas Mixture . . . . . . . . 6.5.4 Automatic Controls . . . .

iv

Handbook of Biomass Downdraft Gasifier Engine Systems

. 7.0 Gas Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .