FI118596B - Method for treating biomass - Google Patents

Description

118596

METHOD FOR THE TREATMENT OF BIOMASS IN BIOMASS FÖRFARANDE FÖR ATT BEARBETA

FIELD OF THE INVENTION

The invention relates to a process for treating biomass, and in particular to a process for treating biomass, wherein the biomass is dried in a process in which a substantial part of the dried biomass is recycled to be blended into the incoming biomass. The invention also relates to the biological utilization of various biomasses.

BACKGROUND OF THE INVENTION

Many biomasses such as peat, sludge and various plant residues are biologically utilized, for example in growing media, fertilizers, usually in soil improvement or in the production of biogas in bioreactors. The major problem here is that these, like many other biomasses, are high in fiber, long chain carbon compounds such as sel-15 cellulose, hemicellulose, etc., which are difficult for microorganisms to utilize. Digestion of cellulose into shorter-chain compounds, such as sugars, enhances biological processes. For example, pulp from the papermaking industry also contains a significant amount of biomass, mostly cellulose fiber, and the decomposition of cellulose can also be a cost-effective solution for treating these pulps.

20 In the composting sector, microorganisms are found mainly in the thermophilic region, which also degrade cellulose. Efficient thermophilic composting, which requires, for example: a temperature of about 60 ° C, is only possible in a well-controlled composting reactor. In any case, the time required for composting is several days, and the composted ··· ♦ remains to be post-treated, for example, to be dried or cured and mixed. 25 different curing agents to make it a useful product. Composting also • ·; consumes carbon from biomass and produces carbon dioxide. Composting large quantities of biomass in a reactor is also a relatively expensive solution.

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The use of enzymes to enhance composting is known. Ordinary. . however, it is problematic in composting to effectively distribute the enzyme into the composite * · * 30. Also, the temperature in the compost is rarely favorable for the enzyme to function, i.e. preferably above 60 ° C. For example, the use of cellulase slightly improves the degradation of cellulose in composting, but otherwise does not significantly reduce the disadvantages of composting as a biomass treatment process.

JP 10120482 A discloses a method for accelerating composting. * * *. By adjusting the compost mass, for example, lignin-degrading xylanase and cellulose ··· 118596 yield degrading cellulase. JP 52107970 A discloses a similarly broadly defined method for treating plant material.

The Applicant's International Patent Application WO 00/58229 discloses a solution for treating and utilizing a slurry, wherein the slurry is dried into hydrophobized granules and a substantial portion of the dried granules is recycled to adhere the slurry to the surface of the hydrophobized granules. The treatment may also include composting, whereby rotating the granules several times through composting in the thermophilic region will also decompose relatively well into fibrous material such as cellulose. The solution then also has the disadvantages of the composting solution noted above.

In another alternative of WO 00/58229, the slurry is treated only by drying and recycling the granules. This method, which is the basis of the solution presented herein, is extremely fast and economically advantageous, but the fiber material is not degraded in the treatment and thus the end product is not optimal for bio-utilization.

JP 2001025799 A discloses a sludge treatment process in which the so-called "sludge" is clarified. the concentrated slurry (conventional solids content 3-5%) is mixed with suitable enzymes, mainly cellulase. The purpose is to disintegrate the cell walls and cell membranes in the slurry to facilitate further drying. Addition of the enzyme occurs in a pool to which stirring and heating may have been added to enhance the effect of the enzyme. After treatment with the enzyme, the slurry is further mechanically dried, for example, by centrifugation 20 or leachate extrusion, after which the solids content of the slurry is reported to be 26%. Only then is the slurry apparently dried in a thermal dryer. The enzyme li-. . heating to a concentrated slurry does not seem to make any sense, since in order to achieve the proper effect of the enzyme, the slurry containing 95% water must be heated to 60-70 ° C, · «· ** '*. which requires a lot of energy. In our view, adding the enzyme to such a wet 25 slurry is also not beneficial for its effect.

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It is also known to add cellulase or other enzymes either to the gasification reaction or to the acidification reactor to produce gas from the biomass. The effect of the enzyme is diminished by the fact that the conditions in the reactors are generally not favorable for the enzyme to function, digestion processes. generally operate in the mesophilic region and therefore temperatures below 40 • · * * 30 ° C, which is too low for enzymes Reactors are generally fed with a slurry of 80 · 95% water and dilute enzymes. too much.

SUMMARY OF THE INVENTION ··· “

The object of the invention is, firstly, to provide an efficient and economical process for the utilization of biomasses.

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In particular, it is an object of the present invention to provide a process that significantly improves the potential for utilization of biologically diverse biomasses such as sludge, collected bio-waste or peat.

It is a further object of the invention to provide a treatment method which ensures the hygienisation of biomass and meets the requirements of stricter environmental regulations.

It is yet another object of the invention to provide a process whereby the treated biomass is safe and easy to handle and use and is suitable for many applications.

To achieve these objects, the process for treating biomass according to the invention, wherein the biomass is dried in a process in which a substantial portion of the dried biomass is recycled to be blended into the incoming biomass, is as defined in the characterizing part of claim 1. Other claims define various embodiments of the invention.

The process according to the invention is particularly advantageous because the same conditions are well suited for both drying of the biomass and efficient treatment with enzymes such as cellulase. Recycling of biomass also has a beneficial effect in both drying and enzyme treatment. The wet biomass added in the blend is deposited on dry mass granules or particles, which facilitates drying. The enzyme or mixture of enzymes that is always added when new biomass is added has the most effective effect on the added mass. As the biomass circulates in the process, it undergoes on average several enzyme treatments, which naturally enhances the action of the enzymes.

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"Y BRIEF DESCRIPTION OF THE DRAWINGS

The invention and some embodiments thereof will be described in more detail in the following with reference to the accompanying drawings, in which: Figure 1 schematically illustrates a process for applying the method of the invention; Figure 2 schematically illustrates another process according to the invention. 3 to 5 illustrate embodiments of the method of the invention.

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Y ·: DETAILED DESCRIPTION OF THE INVENTION

··· * ... · For example, better enzyme preparations are continuously being developed to break down cellulose. The same applies to hemicellulose-degrading hemicellulases. Cellulase cleaves m 35 cellulose into glucose and other short chain carbon compounds. Enzyme preparations 4 118596 are often developed for specific applications for the treatment of certain biomasses and often contain several different enzymes. The optimum conditions for the action of different cellulases vary. Enzymes having a favorable temperature range of 60 to 70 ° C and a solids content of 60 to 70% solids to be digested are most suitable for the solutions disclosed in this application. The pH range favorable for cellulase enzymes is generally 3.5 to 5.5, which is characteristic of, for example, peat and vegetable bio-waste. Cellulase enzymes are also prepared in the pH range of 6-8, which is typical, for example, of many slurries.

The term "%" below refers to the percentage by weight in all cases.

10 In the example of Figure 1, the process is based on a process directly destined for granulation. The process corresponds to the method shown in Figure 3.

For example, the final product of the process is dried granules to a dry solids content of about 95%. Drying and granulation takes place in a drum 6, at the end of which the dried granules are taken to a screen 7 and distributed so that the desired fraction is withdrawn from the process as a final product and stored in a dry silo 9 and recycled substantially through a crusher 8, The granules also dry effectively during the cycle. The screen, the crusher and the rotary conveyor are provided with cool dry air blowing, and the rotary tank 3 is blown with a blower 12 of dry air. Crushing ensures that the new granules 20 formed on the recycled granules are small enough, for example for hygienization. A so-called dried slurry having a dry solids content of 20-30% is introduced into the process via a sludge silo 1. This is mixed,. in mixer 2, the amount of recycled granules is such that the mixture has a dry solids content.

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***, for example, is from 50 to 55%. During mixing, the enzyme or mixture of enzymes is added to the pulp as indicated by reference number 4 M ·. The mixed pulp with the new wet slurry] 25 deposited on the surface of the dry granules may be fed directly to the drum 6. It may also be * · * · * * * compressed by the nozzle 5 into pieces which are fed to the drum. According to experience, pressing into pieces accelerates the drying process and, most obviously, also helps to effectively and evenly mix the enzyme into the pulp. The pieces are, for example, pieces of circular cross-section having a diameter of 5 to 10 cm. In a continuously rotating dryer 6, the blades gradually mix from the feed end of the drum towards one end, which provides dry air heated through the heat exchanger of the heat unit 11. Vacuum 13 absorbs vacuum into the drum inlet end which causes warm air to flow through the mass to be dried towards the drum inlet end. The exhaust air is purged in Cyclone 14 and supplied to the exhaust air chimney 15. The exhaust air can also be supplied to the chimney »*« 35, for example through a heat exchanger or a deodorizer.

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The operation of the drum 6 may be continuous, such that a certain amount of new slurry and a corresponding amount of circulating fluid are introduced into the mixer, for example every 2 hours, while a certain amount of enzyme or enzyme mixture is added. The cellulase preparation to be added may be, for example, the preparation of AB Enzymes GmbH called Econase CE, which is estimated to be required per kg of biomass per 5 tonnes of dry matter. Because the biomass is recycled in the process and thus is affected several times by the enzyme, a suitable amount of enzyme to be added at a time may be, for example, 0.5 kg per tonne of dry matter of the new sludge incorporated. The enzyme may be diluted with water, for example in a ratio of 1: 2 to 1: 5, prior to mixing with the biomass. Increasing the amount of enzyme by dilution makes it easier to mix evenly with the biomass.

In the process of Figure 3, the incoming biomass with a dry solids content of 20-30% is mixed with the recycled granulate in step 31, whereby a certain amount of the enzyme or mixture of enzymes is added to the pulp. The blended pulp, having a suitable dry solids content of 50-55%, may be compressed into pieces at step 32 or proceed directly to step 33 where the pulp is dried and granulated. In step 33, the pulp is heated to a temperature favorable to the operation of the first selected enzymes. For example, the above-mentioned enzyme preparation Econase CE works best within a temperature range of 60-70 ° C. The pulp is then first heated to this temperature range, where it is then held for, for example, 1 hour, which is a sufficient duration of action of this enzyme. The preferred dry solids content for the enzyme is 60-65%. When the pulp is hand-rolled in a drum with mixing and drying air circulation, its dry solids content also reaches at least close to the best possible processing conditions during the enzyme treatment.

The temperature can then be increased to 75-80 ° C for at least 1 hour to ensure mass hygiene. Thereafter, drying is continued, for example, at a temperature above 70 ° C, until the granules have a solids content of 70-95%, for example about 80% as mentioned above. The pellets taken out of the drum are screened in step 34, whereupon the desired fraction and amount are recovered in the dry granule storage and the required amount of ··· * · ..1 is recycled after the crushing step 35 to the beginning of the process.

Cellulase enzymes suitable for the purpose described herein work best under mild conditions of 1: 30 under acidic conditions, preferably with a pH of less than 6. Therefore, the slurry or other biomass with a somewhat higher pH ··· * ... · may be treated with enzymes, e.g. why with a pH-lowering dilute acid such as acetic acid or a strongly diluted hydrochloric acid.

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The temperature of the pulp to be treated in the tumble drier or granulator is maintained for at least 1 hour at 75 ° C for at least 75 hours, and after each addition of 2 [mu] m, 118596 6, the above treatment is repeated. If the process is continuous, ensure that there is a period of hygienisation as the mass passes through the body.

In our opinion, it is not wise to raise the temperature of the pulp at any time, at least not significantly above 70-80 ° C. First, it could pose a fire risk, as with increasing temperatures, for example, the risk of ignition of dust is always increasing, and because biomass, such as peat, may contain highly flammable gasifying components. On the other hand, the drying process is also the most economical and easiest to implement and control, while maintaining these temperatures. In addition to the action of enzymes, pulp drying is also a partially biological process in which the heat generated by biological reactions also contributes, and temperatures most suitable for the biological function of the process are preferably below 70 ° C. The temperature of the air supplied to the dryer or granulator is, of course, somewhat higher than the desired pulp temperature.

The biomass continues to dry during recycling through a screen, a crusher, a rotating belt and a recycle pulp container through subsequent blowing of dry dry air and dehumidification. A suitable temperature for this drying air is, for example, 15-20 ° C. Warm granules from the drum dry effectively when brought into dry cool air due to the large difference in vapor pressure, while shrinking and solidifying. The result is solid granules having a solids content of 80-95 ° C.

Hygiene is ensured not only by the heat treatment described above, but also by crushing the recycled granules so that the new granules formed on them are small enough to raise the temperature throughout. As the mass has already been kept close to the hygienization temperature prior to the hygienisation step, "raising the temperature sufficiently high is virtually certain. It should also be noted that if the method involves pressing the mass into pieces prior to drying and heating, As the larger pieces remain in the treatment, the retention time at the gelling temperature can be extended accordingly.

The method of Figure 4 comprises substantially the same steps as the method of Figure 3, and only the granulation and drying step 33 'differs from the corresponding step of Figure 3 in that the addition of enzymes occurs in step 33. 'and not at the mixing stage 31 and that the biomass is therefore heated to 60-70 ° C with stirring.

Figure 2 shows another example of a process in which the method according to the invention has been applied. An example of a similar method is shown in Figure 5. Enzyme Age ···, 1. processing takes place in reactor 22 equipped with a heating device 26,27. Additional biomass

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I. »35 is disposed on top of the reactor, and the bottom 23 of the reactor is constructed so that the mass passes through the conveyor 24 underneath the bottom, and on the other hand the air is directed by arrows A and circulated by the vacuum 28 After the enzyme treatment, the pulp is discharged by means of conveyor 24 to a dryer 25 whereby it is dried to a solids content of 70-95%. The drying may involve granulation and may be carried out in the same manner as described above with respect to the process of Figure 1. Part of the dried pulp is taken to storage 28 and part recycled through a screen 7 and crusher 8 back to the beginning of the process into a binder silo 19, where other dry biomass, for example cellulosic pulp, can also be introduced for use as a binder in the process. The biomass to be added to the process is introduced into the silo 16 and from there through a crusher 17 to a mixer 20 where it is mixed with recycled dry biomass and possibly other binder from the silo 19 so that the mixture has a dry solids content of 10 to 50%. In the mixer, a certain amount of enzyme or mixture of enzymes is added to the pulp relative to the amount of dry matter of the biomass introduced into the process in the same manner as described above in connection with the process of Figure 1 and the process of Figure 3. The mixed and enzymatic biomass can be fed directly to the reactor 22 or, in this case, pressed into pieces by the nozzle 21.

One possible heat treatment in an enzymation reactor is described with reference to Figure 5. Crushing, mixing, adding enzymes and possibly crushing steps 36, 37 and 38 are, for example, as described above. In step 39, the pulp is first heated in the reactor to, for example, 60-70 ° C, where it is held for 1 hour, which is a sufficient time for the enzymes to act. The mass is then heated to 75 ° C for 1 hour to ensure hygiene. In step 40, the pulp discharged from the reactor is dried to a solids content of 70-95% and part of it is stored as a finished product and,. the part is recycled for blending at the beginning of the process with the incoming biomass.

• · · * '*. * In the case of cellulase-treated biomass, such as digestate hydrolysis residue or

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** · *, the end products of some biowaste smell, so the odor nuisance can be removed by, for example, hydrogen peroxide * 25 dressing treatment. For example, 40% hydrogen peroxide diluted 1: 2 to 1: 5 can be used. Hydrogen peroxide oxidizes odor gases such as hydrogen sulphide. At the same time, hydrogen peroxide hygienizes, for example, sludge or biowaste, that is, kills any pathogens and plant pathogens that may be present. Hydrogen peroxide kills, among other things, the Clostridium bacteria that reduce sulfides.

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ί.ί: 30 Peat also has absorbent properties and peat contains antiseptic and deodorant ingredients. Adding peat as a binder to, for example, sludge or biowaste (e.g. 10-15% peat) reduces odor nuisance in the final product.

The biomass to be treated by the process of the invention may be, for example, a dried ··· sewage sludge, as in the process of Figure 1. The method can also treat the digestion residue of the digestion plant. The biomass to be treated may also include agricultural or livestock biomass rich in cellulose and hemicellulose or food waste 118596

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biomass produced. The biomass may also include milling or sucking peat or crushed lump peat. Peat as such can also be advantageously treated by the process of the invention. Further, the biomass may include material derived from wood or other plants, such as tannery, bark slag, sawdust, wood chips or straw, or paper waste, which is often present in significant amounts in, for example, separately collected biowaste. The pulp to be treated may also be a waste pulp, of which only a part is biomass, for example fibrous clay produced as waste from the paper industry, typically 25% biomass (fiber), 25% clay and 50% water.

The biomass treated by the process of the invention is a dry, hygienized pulp (in many cases granulated) in which cellulose and possibly hemicellulose have been substantially degraded by enzymatic treatment while the pulp has been dried. For this reason, the end product is well suited, for example, as a soil conditioner or as a basic material for the production of bio-fertilizer. In the production of biogas, the treatment of cellulosic biomass with the process according to the invention prior to its introduction into the bioreactor significantly improves gas production, since microbes have significantly more ly-15-chain carbon compounds available than initially in the pulp. For example, the slurry can be processed by the process of the invention into granules which are fed directly into the digestion reactor. The granulated pulp is also well suited for the implementation of various biofilters, for example in waste water treatment.

The above values, such as temperatures, treatment times, solids content, and amount of enzyme added, are only examples. For example, as enzyme preparations develop, other values may become more advantageous in carrying out the process of the invention. Above. . the exemplary processes described include a step of ensuring hygienisation. • · * · *. * May also be used for applications where it is not needed and the mass temperature may be kept slightly low * ···. throughout the process.

() <25 The dry matter content of the biomass entering the drying step can vary, for example, from * -1 to 40% to 65%.

The implementation of the drying drums, reactors or the like used in the application of the process can also vary in many ways. For example, the process described in Figure 2 can also be carried out in a horizontal reactor, which may also be: rotating • a: 30 drum to connect reactor and dryer.

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The invention may vary within the scope of the appended claims.

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Claims (10)

A process for processing biomass, in which process the biomass is dried to a dry matter content of 70 - 95% in a process in which: the biomass is first mixed (31, 37) with recycled dried biomass, so that the dry matter content of the mixture formed is 40-65%, the mixture is dried (33.33 ', 39) by means of heating and air circulation, so that its temperature is raised to the range 60-80 ° C, with pouring times in temperatures within it, In: * the area is of the order of one hour or several hours and *: ** · a substantial portion of the dried biomass is circulated back to be mixed with the biomass entering the process, so that the biomass is circulated in The process in ♦ · · averages several times, ··· ϊ .., characterized in that one or more enzyme or mixture of enzyme containing at least cellulase is added to the biomass in the drying process, whereby process values and the enzyme or mixture are added. none of the enzymes is selected so that the temperature and the pouring time in the temperature are favorable -: ***: 30 the same for the activity of the enzyme and that the recycling and addition of the enzyme is arranged. · · · # So that the enzyme is added to the biomass on average several times in the processing. • Process according to claim 1, characterized in that said favorable temperature: is 60-70 ° C. 35 118596 Method according to claim 1, characterized in that said pouring time at a temperature within the range 60 - 80 ° C for the activity of the enzyme is of the order of 1 hour. Method according to claim 1, characterized in that the enzyme or mixture of enzyme 5 contains additional hemicellulase. Process according to claim 1, characterized in that the enzyme or mixture of enzymes is added to the biomass in the mixing phase (31, 37). 10 Process according to claim 1, characterized in that the enzyme or mixture of enzymes is added to the biomass in the beech of the drying phase (33 '). Process according to claim 1, characterized in that the enzyme or mixture of enzyme is diluted with water in a ratio of 1: 2-1: 5 to improve the mixture to the biomass. 15 Process according to claim 1, characterized in that the dry matter content of the biomass entering the process is 20 - 30%, the dry matter content of the mixture formed at the beginning of the drying is 50-55% and the dry matter content of the biomass starting from the process is 70 - 95%. 20 Method according to claim 1, characterized in that it comprises further granulation (6) and / or crushing. m «· ···· Method according to claim 1, characterized in that it comprises a phase in which the biomass is poured at least 1 hour at a temperature higher than 70 ° C to ensure the hygiene of:: 1: the biomass. ··· · ··· · · · · · · · ·· · ♦ · · ··· * ♦ · · ··· * * ·· • · · ··· • ♦ • · · · · * · · ··· · ·