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WO2012158115A2 - Élimination de l'humidité dans une étape de préséchage au cours d'un processus de torréfaction - Google Patents

Élimination de l'humidité dans une étape de préséchage au cours d'un processus de torréfaction Download PDF

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Publication number
WO2012158115A2
WO2012158115A2 PCT/SE2012/050530 SE2012050530W WO2012158115A2 WO 2012158115 A2 WO2012158115 A2 WO 2012158115A2 SE 2012050530 W SE2012050530 W SE 2012050530W WO 2012158115 A2 WO2012158115 A2 WO 2012158115A2
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WO
WIPO (PCT)
Prior art keywords
biomass
torrefaction
zone
drying
moisture content
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/SE2012/050530
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English (en)
Other versions
WO2012158115A3 (fr
Inventor
Ingemar Olofsson
Martin NORDWAEGER
Anders Nordin
Katarina HÅKANSSON
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Bioendev AB
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Bioendev AB
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
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Publication of WO2012158115A2 publication Critical patent/WO2012158115A2/fr
Publication of WO2012158115A3 publication Critical patent/WO2012158115A3/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G OR C10K; LIQUIFIED PETROLEUM GAS; USE OF ADDITIVES TO FUELS OR FIRES; FIRE-LIGHTERS
    • C10L9/00—Treating solid fuels to improve their combustion
    • C10L9/08—Treating solid fuels to improve their combustion by heat treatments, e.g. calcining
    • C10L9/083—Torrefaction
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E50/00—Technologies for the production of fuel of non-fossil origin
    • Y02E50/10—Biofuels, e.g. bio-diesel

Definitions

  • the present invention relates to the field of torrefaction of biomass. In particular, it relates to an improvement of the energy efficiency in a
  • Torrefaction is a thermal pre-treatment method that normally takes place in a substantially inert (oxygen free) atmosphere at a temperature of about 220- 600°C. During the process course a combustible gas comprising different organic compounds is produced from the biomass feedstock in addition to the torrefied biomass.
  • the process of producing a torrefied material from lignocellulosic biomass can be said to include four stages:
  • a torrefaction stage in which the material is actually torrefied and which starts when the material temperature reaches about 220°C -230°C.
  • the biomass partly decomposes and releases different types of volatiles/hydro carbons, such as hydroxy acetone, methanol, propanal, short carboxylic acids etc.
  • the torrefaction stage is characterised by decomposition of hemicellulose at temperatures from 220°C -230°C, and at higher torrefaction temperatures cellulose and lignin also starts to decompose and release volatiles; cellulose decomposes at a temperature of 305-375°C and lignin gradually decomposes over a temperature range of 250-500°C; 4) a cooling step to terminate the process and facilitate handling.
  • the torrefaction process is terminated as soon as the material is cooled below 220°C -230°C Summary of the present disclosure
  • combustible gases are released from the biomass.
  • these gases are usually collected and combusted in a boiler so that the energy in the gases can be reused as heat in the drying, heating and/or torrefaction stage of the torrefaction process.
  • the present inventors have realized that also during the drying process combustible gases are given off from the biomass.
  • Freshly cut wood contain about 50 % to 80 % moisture, but after storage the moisture content typically fall to about 35-40 %.
  • free water retained in the biomass is removed so that the moisture content is reduced close to zero. Therefore the water content in the gas mixture produced during the drying step is high and the gas mixture is thus not suitable for combustion.
  • the gas mixture released during the drying step comprises different kinds of smelly chemicals, such as terpenes, which needs to be destructed.
  • smelly chemicals such as terpenes
  • the present invention is based on the finding that the gases given of during the drying step can be collected and efficiently combusted in a combustion chamber together with gases produced later in the torrefaction process, provided that the water content in the biomass is sufficiently low, such as below 15 %.
  • the inventors have also realized that the vast majority of smelly volatiles released during the drying step are released in a late phase of the drying step. The proportion of the smelly volatiles is thus constantly increasing during the drying process and when the biomass is dried to a moister content below 6-7 % (w/w) the amounts are increasing rapidly.
  • the inventors thus solves the problems above by including a pre- drying step in the torrefaction process wherein the biomass initially is dried such as that the water content in the biomass is reduced below 15%, preferably below 10%.
  • the gas released during the first drying step mainly contains water and is therefore not suitable for combustion and does not need to be destructed. Therefore this gas can be released to the surrounding.
  • the biomass is further dried, e.g. in a drying zone of a torrefaction arrangement.
  • the gases released during this second drying step comprise smelly volatiles and are suitable for combustion. Therefore these gases are collected and preferably combusted in a combustion chamber together with the gases released during the heating and torrefaction stages.
  • the invention relates to a method of torrefaction of biomass and combustion of generated gases, comprising the steps of;
  • step a) drying biomass having an average moisture content of at least 20 %, such as at least 25 % (w/w) to obtain a dried biomass having an average moisture content of 3-15 % (w/w) and a first gas product; b) further drying the biomass from step a) to obtain a dry biomass and a second gas product;
  • step b) heating and torrefying the biomass from step b) to obtain torrefied material and a third gas product;
  • the invention in a second aspect relates to a system for torrefaction of biomass and combustion of generated gases, comprising: a first zone for drying biomass, said first zone having a biomass inlet, a gas outlet and a dried biomass outlet;
  • At least one additional zone for further drying, heating and torrefying the dried biomass from the first zone, said at least one additional zone having an inlet connected to the dried biomass outlet of the first drying zone and at least one gas outlet;
  • a gas combustion chamber being connected to receive gases from the at least one gas outlet of the at least one additional zone but not from the gas outlet of the first zone.
  • Figure 1 shows a system for torrefaction of biomass and combustion of generated gases. Definitions:
  • a thermal pre-treatment method that takes place in a virtually inert (oxygen- reduced or oxygen free) atmosphere at a temperature above 220 °C but below 600 °C and which produces a torrefied biomass and combustible gases.
  • a torrefaction stage parts of the biomass, in particular hemicellulose, decompose and releases different types of organic volatiles.
  • the actual torrefaction stage is preceded by a drying stage wherein free water retained in the biomass is removed and by a heating stage wherein the biomass is heated to the desired torrefaction temperature.
  • a specific region of a compartment in a torrefaction reactor located upstream of a heating zone in relation to a biomass inlet of a torrefaction reactor, comprising means for regulating the temperature in said specific region and wherein a biomass is dried to a water content below 10 % prior to heating.
  • Heating zone A specific region of a compartment in a torrefaction reactor, located upstream of a torrefaction zone in relation to a biomass inlet of a torrefaction reactor, comprising means for specifically regulating the temperature in said specific region and wherein the temperature of a biomass is increased to a
  • a specific region of a compartment in a torrefaction reactor located downstream of a heating zone in relation to a biomass inlet of a torrefaction reactor, comprising means for specifically regulating the temperature in said specific region and wherein the temperature of a previously heated biomass is kept virtually constant at the desired torrefaction temperature for a desired torrefaction time wherein a desired torrefaction temperature is in a range between 220 °C to 600 °C.
  • the residence time of the material in the torrefaction zone may be referred to as the torrefaction time.
  • the invention relates to a method of torrefaction of biomass and combustion of generated gases, comprising the steps of;
  • step a) drying biomass having an average moisture content of at least 20 %, such as at least 25 % (w/w) to obtain a dried biomass having an average moisture content of 3-15 % (w/w) and a first gas product; b) further drying the biomass from step a) to obtain a dry biomass and a second gas product;
  • step b) heating and torrefying the biomass from step b) to obtain torrefied material and a third gas product;
  • the dry biomass from step b) may have an average moisture content of less than 4 % (w/w), preferably less than 3 % (w/w).
  • the method comprises a step of determining the moisture content and/or the moisture content distribution between step a) and step b). Preferably the moisture content and/or the moisture content distribution is determined by NIR spectroscopy.
  • the gas mixture sent to combustion preferably has a theoretical flame temperature of at least 1500 °C.
  • the amount of energy supplied to the biomass in step a) may for example be increased by increasing the residence time of the biomass in the initial drying stage.
  • a low moisture content between step a) and step b), such as a moisture content below 3% indicates that the biomass have been over-dried which leads to a unnecessarily high loss of combustible gases is step a). Furthermore this leads to higher amounts of smelly volatiles present in the gas released during step a).
  • the amount of energy supplied in step a) should be decreased.
  • the amount of energy supplied to the biomass in step a) may for example be increased by increasing the residence time of the biomass in the initial drying stage. Therefore, in one embodiment the determined moisture content between step a) and step b) is compared to a reference value and a degree of heating and/or a residence time in step a) is adjusted based on the comparison.
  • a degree of heating and/or a residence time in step a) is increased if the average moisture content of the biomass is above an upper reference value. Further, the degree of heating and/or the residence time in step a) may be decreased if the average moister content of the biomass is below a lower reference value. In one embodiment the upper and the lower reference value is in the water content range of 3-15 % (w/w), 3-10 % (w/w) or 5-10 % (w/w).
  • the biomass obtained from step a) has moisture content of 3-12 % (w/w), such as 4-1 1 % (w/w), such as 4-10 %, such as 4-9 % (w/w), such as 4-8 % (w/w), such as 5-8 % (w/w).
  • the optimal moisture content level varies with the type of biomass.
  • the method further comprises measuring a combustion temperature in step d) and comparing the combustion
  • the first reference value may for example be at least 1000 °C, such as at least 1 100 °C, such as at least 1300 °C, such as in the range of 1300-1500 °C.
  • the degree of drying in step a) may be increased by increasing the temperature or amount of steam supplied in step a). Also, it maybe increased by increasing the residence time of the biomass in step a).
  • the degree of torrefaction is increased by increasing the residence time of the biomass in a torrefaction zone (i.e.
  • the combustion temperature in step d) is compared to a second reference value and, if the combustion temperature is higher than the second reference value, the degree of drying in step a) or the degree of torrefaction in step c) is decreased.
  • the degree of drying in step a) may be decreased by decreasing the temperature or amount of steam supplied in step a). Also, it maybe decreased by decreasing the residence time of the biomass in step a).
  • the degree of torrefaction is decreased by decreasing the torrefaction time and/or torrefaction temperature.
  • the biomass is lignocellulosic biomass, such as a wood material, e.g. wood chips.
  • a second aspect of the invention relates to a system for torrefaction of biomass and combustion of generated gases, comprising:
  • a first zone for drying biomass said first zone having a biomass inlet, a gas outlet and a dried biomass outlet; at least one additional zone for further drying, heating and torrefying the dried biomass from the first zone, said at least one additional zone having an inlet connected to the dried biomass outlet of the first drying zone and at least one gas outlet; and
  • a gas combustion chamber being connected to receive gases from the at least one gas outlet of the at least one additional zone but not from the gas outlet of the first zone.
  • a NIR camera is arranged at the dried biomass outlet of the first zone.
  • the NIR camera may be connected to a computer or a programmable logic controller so that the computer may receive a signal containing moisture content information from the NIR camera.
  • the computer may be capable of providing a moisture content value based on the signal. Further, the computer may be capable of comparing such a moisture content value to a reference value, and based on the comparison sending a signal to an arrangement for controlling the degree of drying in the first zone.
  • a temperature sensor is arranged at the combustion chamber.
  • the temperature sensor may be connected to a computer so that the computer may receive a signal containing temperature information from the sensor.
  • the computer may be capable of providing a temperature value based on the signal. Further, the computer may be capable of comparing such a temperature value to a reference value, and based on the comparison sending a signal to an arrangement for controlling the degree of drying in the first zone or the degree of torrefaction in the at least one additional zone.
  • Figure 1 a illustrates a system for torrefaction of biomass
  • Said system (1 ) comprises a first zone for drying biomass (2) having an average moisture content of about 40 % (w/w).
  • a dried biomass having an average moisture content of about 3-15 % (w/w) and a first gas product is generated.
  • Said first gas product comprises high amounts of water and is thus not suitable for combustion. Therefore the first gas product is discarded from the system (1 ) through the first drying zone gas outlet (3).
  • the dried biomass having an average moisture content of about 3-15 % (w/w) thereafter enters a zone for further drying (4) wherein a dry biomass, typically having an average moisture content below 3 % (w/w), and a second gas product is generated.
  • the second gas product comprises lower amount of water and have been shown to be combustible together with other gases. Therefore the second gas product is collected from the zone for further drying (4) via the zone for further drying gas outlet (5). After the biomass have been further dried in the zone for further drying (4) the dry biomass enters a heating zone (6) where the temperature of the biomass is elevated up to a desired torrefaction temperature. Thereafter the biomass enters a torrefaction zone (8) where the temperature is kept at the torrefaction temperature for a desired time (i.e. torrefaction time).
  • the biomass is giving of combustible gases which are collected from the said zones via the heating zone gas outlet (7) and the torrefaction zone gas outlet (9).
  • the torrefied biomass is cooled to a temperature below 130 °C in a cooling zone (10) and combustible gases are optionally collected from the cooling zone (10) via the cooling zone gas outlet (1 1 ).
  • the gas collected from the zone for further drying (4), the heating zone (6), the torrefaction zone (8) and optionally the cooling zone (10) are transported and introduced into a combustion chamber (12) of a boiler via a combustion chamber gas inlet (13).
  • the heat generated is used to heat water transported to the boiler via a water inlet (14) to produce steam which exits the boiler via the steam outlet (15).
  • the produced hot steam can be used in the drying steps, heating step and/or torrefaction step in the torrefaction process.
  • gases from the zones for further drying (4), heating (6), torrefaction (8) and optionally cooling (10) may be collected from a single outlet. Thus, it is not necessary to have four different outlets (5, 7, 9, 1 1 ).
  • a NIR camera is arranged at the biomass outlet of the first zone (2) for measuring the moisture content of the biomass leaving the first zone (2).
  • the NIR camera may be connected, via a computer, to means for controlling the degree of drying in the first zone (2).
  • Such means may control the residence time of the biomass in the first zone (2).
  • such means may control the amount of steam supplied to the first zone (2).
  • such means may control the temperature of such steam.

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  • Chemical & Material Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Combustion & Propulsion (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Organic Chemistry (AREA)
  • Drying Of Solid Materials (AREA)
  • Solid Fuels And Fuel-Associated Substances (AREA)

Abstract

L'invention concerne un procédé de torréfaction de biomasse et de combustion des gaz générés qui comprend les étapes consistant à: a) sécher la biomasse ayant une teneur en humidité moyenne d'au moins 20 %, à savoir au moins 20 % (p/p) pour obtenir une biomasse séchée ayant une teneur moyenne en humidité de 3 à 15 % (p/p) et un premier produit gazeux; b) sécher ensuite la biomasse issue de l'étape a) pour obtenir une biomasse séchée et un deuxième produit gazeux; c) chauffer et torréfier la biomasse issue de l'étape b) pour obtenir une matière torréfiée et un troisième produit gazeux; et d) brûler ensemble les deuxième et troisième produits gazeux sans le premier produit gazeux.
PCT/SE2012/050530 2011-05-18 2012-05-16 Élimination de l'humidité dans une étape de préséchage au cours d'un processus de torréfaction Ceased WO2012158115A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE1150464 2011-05-18
SE1150464-4 2011-05-18

Publications (2)

Publication Number Publication Date
WO2012158115A2 true WO2012158115A2 (fr) 2012-11-22
WO2012158115A3 WO2012158115A3 (fr) 2013-03-14

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Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL1030864C2 (nl) * 2006-01-06 2007-07-09 Stichting Energie Werkwijze en inrichting voor het behandelen van biomassa.
US8276289B2 (en) * 2009-03-27 2012-10-02 Terra Green Energy, Llc System and method for preparation of solid biomass by torrefaction
US8449724B2 (en) * 2009-08-19 2013-05-28 Andritz Technology And Asset Management Gmbh Method and system for the torrefaction of lignocellulosic material
US8956426B2 (en) * 2010-04-20 2015-02-17 River Basin Energy, Inc. Method of drying biomass
NL2007106C2 (en) * 2010-12-01 2013-01-15 Biolake B V Apparatus and process for the thermal treatment of biomass.

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
A. NORDIN; L. POMMER; I. OLOFSSON; K. HAKANSSON; M. NORDWAEGER; S. WIKLUND LINDSTR6M; M. BROSTR6M; T. LESTANDER; H. ORBERG; G. KAL: "Swedish Torrefaction R&D program", FIRST ANNUAL REPORT, 18 December 2009 (2009-12-18)
K. HAKANSSON ET AL.: "Torrefaction and gasification of hydrolysis residue", 16TH EUROPEAN BIOMASS CONFERENCE AND EXHIBITION, VALENCIA, SPAIN. ETAFLORENCE, 2008
M. J PRINS ET AL.: "More efficient biomass gasification via torrefaction", ENERGY, vol. 31, no. 15, 2006, pages 3458 - 3470, XP024900326, DOI: doi:10.1016/j.energy.2006.03.008
P. C. A. BERGMAN ET AL.: "Torrefaction for Entrained Flow Gasification of Biomass", REPORT C--05-067; ENERGY RESEARCH CENTRE OF THE NETHERLANDS (ECN): PETTEN, THE NETHERLANDS, July 2005 (2005-07-01)

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