WO2001094498A1

WO2001094498A1 - Method and apparatus for producing pyrolysis oil

Info

Publication number: WO2001094498A1
Application number: PCT/FI2001/000535
Authority: WO
Inventors: Anja Oasmaa; Yrjö SOLANTAUSTA; Eeva Kuoppala; Eero LEPPÄMÄKI; Kai SIPILÄ
Original assignee: Valtion Teknillinen Tutkimuskeskus
Priority date: 2000-06-08
Filing date: 2001-06-06
Publication date: 2001-12-13
Also published as: AU2001274125A1

Abstract

The invention relates to a method and an apparatus for producing pyrolysis oil by generating pyrolysis steam by flash pyrolysis of raw material containing extractive compounds and condensing the pyrolysis steam into a pyrolysis liquid. According to the invention, most of the extractive based compounds are separated from the pyrolysis liquid obtained via the pyrolysis to produce a pyrolysis oil of improved quality, and at least part of the separated fraction containing extractives is recovered, processed further and/or utilized. The apparatus of the invention comprises a pyrolyzer (1), a condenser (2), at least one separating device (3) for the separation of extractive based compounds and at least one means (4, 5, 6, 7) for the recovery, further processing and/or utilization of the fraction containing extractives.

Description

METHOD AND APPARATUS FOR PRODUCING PYROLYSIS OIL

The present invention relates to a method as defined in the preamble of claim 1 and to an apparatus as defined in the preamble of claim 12 for the production of pyrolysis oil by generating pyrolysis steam via flash pyrolysis of raw material containing extractive compounds and condensing the pyrolysis steam into a pyrolysis liquid. In this context, 'extractive agent' refers e.g. to resinoic acids, fatty acids, sterols, triglyc- erides or equivalent substances.

Several flash pyrolysis methods for the production of pyrolysis liquids and chemicals are known. In addition, flash pyrolysis methods for the production of pyrolysis oil for combustion are known. E.g. patent application FI 19992180 presents a method and an apparatus for the production of pyrolysis oil, and patent application FI 19992181 presents a method and an apparatus for improving the quality of a pyrolysis liquid.

A pyrolysis liquid consists of several tens or hundreds of chemical compounds, which have an effect on the properties of the product, e.g. properties regarding storability and combustion.

A problem with the combustion of previously known pyrolysis liquids is the formation of carbon deposits and glutinous substances in boilers and motors, causing disturbances in the operation of their atomiz- ers, which therefore have to be cleaned by interrupting the combustion process. Cleaning can be effected by supplying a solvent, such as alcohol, into the atomizers, which is an expensive and time-consuming solution. The object of the invention is to reduce the above-mentioned problems and to disclose a new practicable method and apparatus for the production of py- rolysis oil. A specific object of the invention is to disclose a method which can be used to produce pyrolysis oil of improved quality on an industrial scale for combustion. The method and apparatus of the invention are characterized by what is presented in the claims.

The invention is based on producing pyrolysis oil by generating pyrolysis steam from raw material containing extractive compounds and condensing the steam to produce a pyrolysis liquid. According to the invention, most of the extractive based compounds are separated from the pyrolysis liquid obtained via pyrolysis to produce a pyrolysis oil of improved quality. At least part of the separated fraction contain- ing extractives is recovered, processed further and/or utilized.

During the pyrolysis, some of the extractive compounds contained in the raw material may be converted into different compounds. In this case, the py- rolysis liquid may contain extractive compounds and/or compounds derived from these, all such compounds being designated in this context by the common term 'extractive based compounds'. 'Fraction containing extractives' in this context refers to a fraction separated from the pyrolysis liquid and containing extractive based compounds. A fraction containing extractives may preferably also contain other compounds.

In an embodiment of the invention, a separate phase, preferably a surface phase, containing extrac- tive based compounds is separated from the pyrolysis liquid. In an embodiment, the separate phase may be an intermediate phase .

In an embodiment of the invention, the quantity of extractive based compounds separated from the pyrolysis liquid amounts to 5 - 60 % by volume, preferably 20 - 40 % by volume, of the volume of the pyrolysis liquid. In an embodiment of the invention, the separation of extractive based compounds is performed mechanically in a decanter, sedimentation basin, centrifuge, extraction apparatus or a similar apparatus. In an embodiment of the invention, extractive based compounds are separated via solvent extraction, using e.g. n-hexane. Solvent extraction may alternatively be used in combination with mechanical separation or for separating a given component from a me- chanically separated fraction containing extractives.

In an embodiment of the invention, the separated fraction containing extractives is processed by distilling it into fractions. The fractions can be processed further either in separation from or par- tially together with each other.

In an embodiment of the invention, the fraction containing extractives is processed to produce chemicals, e.g. lubricants, anti-corrosion agents or the like. The fraction containing extractives used for the production of chemicals may have been separated mechanically and/or via solvent extraction.

In an embodiment of the invention, from the resinoic and/or fatty acids of the fraction containing extractives, an emulgator is produced via esterifica- tion. In an embodiment of the invention, the pyrolysis oil obtained is mixed with an emulgator produced from a fraction containing extractives and/or with light fuel oil to improve the quality of the pyrolysis oil. In addition, the pyrolysis oil may be mixed with a suitable chemical, polymer or a similar substance if desired.

In an embodiment of the invention, at least part of the fraction containing extractives, preferably after further processing, is mixed in the pyroly- sis oil to improve its quality as a fuel. Alternatively, the fraction containing extractives or part of it may be mixed in the pyrolysis oil without further processing.

In an embodiment, an organic liquid, e.g. methanol, and/or light fuel oil may be added to the pyrolysis oil to form an emulsion and an improved pyrolysis oil for use as a fuel.

In an embodiment of the invention, the pyrolysis liquid has been manufactured from forest waste, bark, peat, wood and/or waste plastic or mix- tures of these. In a preferred embodiment, the raw material used to produce a pyrolysis liquid is forest waste.

The apparatus of the invention comprises a pyrolyzer, in which a raw material containing extrac- tive compounds is processed by flash pyrolysis to produce pyrolysis steam, a condenser for condensing the pyrolysis steam into a pyrolysis liquid, at least one separating device for separating extractive based compounds from the pyrolysis liquid obtained via pyroly- sis and at least one means for the recovery, further processing and/or utilization of the separated fraction containing extractives.

The method of the invention makes it possible to produce a pyrolysis oil having an improved quality, e.g. in regard of its properties as a fuel. Moreover, the invention makes it possible to utilize the fraction containing extractives e.g. in the manufacture of a chemical and/or for improving the quality of pyrolysis oil. By using a pyrolysis oil manufactured by the method of the invention as a fuel, the formation of carbon deposits in the atomizers of boilers and motors can be reduced because especially resinoic acids produce carbon deposits. Furthermore, no significant amounts of glutinous compounds are generated by the combustion of the pyrolysis oil of the invention. Further, the method of the invention can be used to improve the thermal value of the pyrolysis oil produced. In addition, the solid matter content of the pyrolysis oil and therefore the dust emissions arising from its combustion can be reduced.

A further advantage of the method of the invention is that a homogeneous pyrolysis oil is achieved by separating extractive based compounds or possibly a separate phase from the pyrolysis liquid and that the fraction or phase containing extractives separated is utilized.

The pyrolysis oil produced by the method of the invention is an advantageous substitute for light fuel oil, used either as such or as an emulsion to- gether with light fuel oil.

The apparatus of the invention has the advantage of simplicity and ease of implementation.

The method of the invention can be applied e.g. in the production of pyrolysis oil and chemicals or in a chemical pulp production plant in the processing of raw soap and pine oil.

In the following, the invention will be described by the aid of detailed examples of its embodiments with reference to the attached drawings, wherein Fig. 1 - 2 present diagrams representing certain embodiments of the apparatus of the invention.

Fig. 1 represents an apparatus according to the invention for the production of pyrolysis oil of improved quality. The apparatus comprises a pyrolyzer 1 and a condenser 2 known in themselves as well as a separating device 3 for the separation of extractive based compounds. Moreover, the apparatus comprises an extraction pipe 4, a distiller 5, a feeder 6 and a mixer 7 for the recovery, processing and utilization of a fraction containing extractives.

In the pyrolyzer 1, a raw material 11 containing extractives is processed by flash pyrolysis at a temperature of 300 - 800 °C to produce pyrolysis steam with a delay of 0.1 - 10 seconds. The pyrolysis steam obtained is passed into the condenser 2, which in this embodiment is a scrubber. In the scrubber, the pyrolysis steam is condensed into a pyrolysis liquid. The pyrolysis steam and/or liquid may be filtered in conjunction with the pyrolyzer and/or scrubber or between them to remove e.g. solids from it. The pyrolyzer used may consist of a circulating-mass fluidized-bed reactor, a frothing fluidized-bed reactor or some other reactor type known in itself.

The production of the pyrolysis liquid may be implemented using e.g. apparatus as presented in patent applications FI 19992180 and/or FI 19992181, by connecting to them a separator 3 according to the invention for the separation of extractive based compounds and means 4,5,6,7 for the recovery, processing and/or utilization of the fraction containing extractives separated, e.g. for passing it back into the py- rolysis oil- In the embodiment of the apparatus illustrated in Fig. 1, the separating device 3 separates from the pyrolysis liquid obtained via pyrolysis a fraction containing extractive based compounds, thus producing a fraction containing extractives 13 and a pyrolysis oil 14. The pyrolysis oil 14 can be used as such, e.g. as a fuel, or passed into a mixer 7 to produce a further improved pyrolysis oil 15. The separating device 3 used is a simple device known in itself, e.g. a sedimentation basin, decanter, centrifuge or some other extracting device or the like. In the present embodiment, the separating device is a sedimentation basin. The separating device is disposed after the scrubber 2. Alternatively, the separating device may be disposed substantially in conjunction with the scrubber. The operation of the separating device 3 is so designed that the separation of extractive based compounds is performed upon the lapse of a certain delay after the condensation 2 of the pyrolysis liquid. The delay may depend on the separating device, the desired properties of the fraction containing extractives and the pyrolysis oil to be produced or on similar factors. The water content of the pyrolysis liquid may determine the length of the delay, because the surface phase of the pyrolysis liquid may initially contain water, most of which will gradually, e.g. within 2 days, sink into the bottom phase, i.e. into the pyrolysis oil .

The apparatus presented in Fig. 1 addition- ally comprises a control device 17 for defining and/or setting e.g. a suitable delay, the number of extractive based compounds to be separated and/or the separation of a desired fraction or phase containing extractives. The control device may be a manually or automatically operated device.

In the embodiment in Fig. 1, the fraction containing extractives 13 is removed from the separating device 3 via the extraction pipe 4 and passed into the distiller, where it is distilled into different fractions. From the distiller 5, one or more fractions are passed via a feed pipe 6 into the mixer 7, where they are mixed with the pyrolysis oil fraction to form a further improved pyrolysis oil 15. In this embodiment, the mixer is a container provided with mixing means known in themselves. Some of the fractions 12 produced in the distillation process 5 may be taken to a chemical production stage or burned as such e.g. in a combustion boiler 10 to produce energy for the pyrolysis process. In an alternative embodiment, the ap- paratus may comprise a desired device disposed between the distiller 5 and the feeder 6 for further processing of the fractions produced via distillation. The apparatus also comprises a combustion boiler 10 known in itself, which may consist of a fluidized-bed boiler or some other boiler known in itself. The raw material 11 to be pyrolyzed may be passed before the pyrolyzer 1 into a separate drier, to be dried so as to reduce the water content of the pyrolysis oil produced. The drier may consist of any type of drier known in the art, and it will not be de- scribed here in detail.

In the embodiment illustrated in Fig. 2, the apparatus of the invention corresponds in other respects to the apparatus presented in Fig. 1 except that it includes no distiller 5. The separated frac- tion 13 containing extractives is passed via the extraction pipe 4 into a unit 8 for producing and emulgator, said unit being connected to the apparatus of the invention. From the emulgator producing unit 8, the emulgator produced is passed via a feed pipe 7 into a mixer 7. In addition, the apparatus comprises a feeder 9 connected to the mixer 7 to supply light fuel oil into the pyrolysis oil 14. The product thus obtained is an improved pyrolysis oil emulsion 16. The residue formed in the emulgator producing unit 8 may be taken e.g. into the combustion boiler 10.

In the embodiments of the apparatus illustrated in Fig. 1 and 2, any kinds of separating device, extraction pipe, distillation equipment, feeder, mixer and controller may be used, which will not be described here in detail.

In an alternative embodiment, the fraction containing extractives 13 is first distilled in the distiller 5, whereupon at least some of the fractions are passed into an emulgator producing unit 8 con- nected to the apparatus of the invention. From the emulgator producing unit, the emulgator produced is taken into the mixer 7 to produce a pyrolysis oil of improved quality.

In an embodiment, the apparatus may comprise a recovery unit for recovering the fraction 13 containing extractives for possible subsequent utilization.

The water content of the pyrolysis oil produced may be reduced and its stability improved by the method presented in patent application FI 19992181.

Example 1

In an experiment, pyrolysis liquid was produced from forest waste using an apparatus according to Fig. 1, in which experiment it was observed that separation of phases occurred in the pyrolysis liquid, forming a multiphase oil due to the polarity differences between the phases. A fraction containing extractives was formed as harder froth-like matter on the surface of the pyrolysis liquid. This surface phase comprised about 30 % by volume of the volume of the pyrolysis liquid, and it contained about 90 - 95 % of the extractive based compounds in the pyrolysis liquid. The surface phase was almost anhydrous. The surface phase containing extractive based compounds was separated from the pyrolysis liquid by mechanical means .

Most of the extractive based compounds were derived from bark and needles contained in the forest waste. In addition to extractive based compounds, the pyrolysis liquid produced from the forest waste contained e.g. fatty alcohols, dicarboxylic acids and monomers of lignin. The fraction containing extractives contained a smaller amount of small-molecule breakdown products of cellulose and hemicellulose, because they preferably evaporated or reacted with or were dissolved in the bottom phase, i.e. the pyrolysis oil produced. Water-soluble compounds appeared after the separation more advantageously in the pyrolysis oil phase because of its higher water content. The surface phase contained a larger proportion of poorly water soluble methoxy phenols. It has been established that methoxy phenols cause obstruction of atomizers. The surface phase additionally contained solid matter and ash.

Table 1 presents the fuel properties of the surface phase containing extractives and of the pyrolysis oil.

Table 1 : Fuel properties

Table 1 shows that the pyrolysis oil produced has good fuel properties.

The separated phase containing extractives is preferably not used as such as a fuel because of the large amount of resinoic acids contained in it. Instead, the phase containing extractives is well suited for use as a source material for emulgators, detergents, lubricants and anti-corrosion agents. Example 2

In this experiment, the solid surface phase in a fresh state was separated mechanically from the fluid pyrolysis oil, i.e. from the bottom phase. Most of the substances forming carbon deposits in combustion could be removed.

The surface phase was taken to an emulgator producing stage, where the resinoic and fatty acids in the surface phase containing extractives were esteri- fied with alcohol to produce emulgators. The alcohol used was methanol or preferably glycol , whose properties include a good lubricity in the finished pyrolysis oil product. The emulgator produced was mixed as a methanol solution into the pyrolysis oil together with a certain polymer and light fuel oil, producing as a result a pyrolysis oil of a further improved quality.

Example 3 : Production of an emulgator

50 ml of methanol was added into the fraction (40 g) containing extractives, and the mixture was re- fluxed while simultaneously agitating it, using a hot plate. 10 g of solid NaOH was added into the mixture, and the mixture was refluxed further for 24 h. The fatty acids in the fraction containing extractives reacted forming Na salts because water was present. 20 ml of sulfuric acid (48 %) was gradually added into the mixture, simultaneously continuing the refluxing for 8 h. The mixture had a pH value below 4. Under these conditions, free fatty acids were generated. The sulfuric acid also served as an esterifying catalyst, and the fatty acids were esterified with the methanol present in the reaction mixture. Part (7.7 g) of the esterified mixture was leached with 5 ml of hexane, and the hexane leachate was analyzed. The leachate contained plenty of methyl esters of various organic acids. Even formic and acetous acids in the fraction containing extractives had been esterified.

In the production of an emulgator, sulfuric acid can be substituted e.g. with formic acid or acids of the distillate fraction.

The method and apparatus of the invention are applicable as different embodiments in the manufacture of pyrolysis oils, especially pyrolysis oils of improved quality in which the formation of carbon deposits during combustion is minimized. Furthermore, the method and apparatus of the invention are applicable for the separation of extractive based compounds from a pyrolysis liquid and for their further processing.

The embodiments of the invention are not restricted to the examples presented above; instead, they may be varied within the scope of the claims below.

Claims

1. Method for producing pyrolysis oil by generating pyrolysis steam by flash pyrolysis of raw material containing extractive compounds and condensing the pyrolysis steam into a pyrolysis liquid, characteri zed in that most of the extractive based compounds are separated from the pyrolysis liquid obtained via the pyrolysis to produce a pyrolysis oil of improved quality, and at least part of the fraction containing extractives is recovered, processed further and/or utilized.

2. Method as defined in claim 1, characterized in that a phase containing extractive based compounds, preferably a surface phase, is sepa- rated from the pyrolysis liquid.

3. Method as defined in claim 1 or 2, characterized in that the quantity of extractive based compounds separated from the pyrolysis liquid amounts to 5 - 60 % by volume, preferably 20 - 40 % by volume, of the volume of the pyrolysis liquid.

4. Method as defined in any one claims 1 - 3, characterized in that the separation of extractive based compounds is performed mechanically in a decanter, sedimentation basin, centrifuge, extrac- tion apparatus or a similar apparatus.

5. Method as defined in any one claims 1 - 4, characterized in that extractive based compounds are separated via solvent extraction.

6. Method as defined in any one claims 1 - 5, characterized in that the separated fraction containing extractives is processed by distilling it into fractions.

7. Method as defined in any one claims 1 - 6, characterized in that the fraction containing extractives is processed to produce chemicals.

8. Method as defined in any one claims 1 - 7, characterized in that an emulgator is pro- duced from the resinoic and/or fatty acids of the fraction containing extractives via esterification.

9. Method as defined in any one claims 1 - 8, characterized in that the pyrolysis oil ob- tained is mixed with the emulgator produced from the fraction containing extractives and/or with light fuel oil to produce an emulsion and to improve the quality of the pyrolysis oil .

10. Method as defined in any one claims 1 - 9, characterized in that at least part of the fraction containing extractives is mixed in the pyrolysis oil to improve its quality.

11. Method as defined in any one claims 1 - 10, characteri zed in that the pyrolysis liq- uid has been produced from forest waste, bark, peat, wood and/or waste plastic.

12. Apparatus for the production of pyrolysis oil, said apparatus comprising a pyrolyzer (1) , in which a raw material (11) containing extractive com- pounds is processed by flash pyrolysis to produce pyrolysis steam, and a condenser (2) for condensing the pyrolysis steam into a pyrolysis liquid, c h a r a c - terized in that the apparatus comprises at least one separating device (3) for separating extractive based compounds from the pyrolysis liquid obtained via pyrolysis to produce a pyrolysis oil (14,15,16) of improved quality and at least one means (4,5,6,7) for the recovery, further processing and/or utilization of the separated fraction containing extractives.

13. Apparatus as defined in claim 12, characterized in that the separating device (3) is a decanter, sedimentation basin, centrifuge, extraction apparatus or the like.

14. Apparatus as defined in claim 12 or 13, characterized in that the apparatus comprises a control device (17) for setting a suitable delay, the number of extractive based compounds to be sepa- rated and/or controlling the separation of a desired fraction containing extractives.

15. Apparatus as defined in any one of claims 12 - 14, characterized in that the apparatus comprises a distiller (5) for fractionating a fraction containing extractives.

16. Apparatus as defined in any one of claims 12 - 15, characterized in that the apparatus comprises a feeder (6) for passing the fraction con- taining extractives or a part of it and/or an emulgator and/or other chemical produced from it into the pyrolysis oil to improve its quality.