FI126140B - Method for the treatment of biomass for recovery - Google Patents

Description

METHOD FOR THE TREATMENT OF BIOMASS MACHINES FOR THE UTILIZATION OF BIOMASSOR FÖR UTNYTTJANDE FÖRFARANDE FÖR ATT BEHANDLA

FIELD OF THE INVENTION

The invention relates to a process for the treatment of biomasses for recovery and specifically to the treatment of passive biomasses together with active biomasses in order to render the utilization more appropriate, efficient and economically viable.

BACKGROUND OF THE INVENTION

Significantly more extensive and efficient use will be made of different biomasses in the future. Renewable biomass will be an important source for the production of various forms of renewable energy, such as biogas, bioliquids or gaseous and solid biofuels. It is also appropriate to make better use of biomass produced as industrial by-products or waste, municipal waste and agricultural waste or by-product. More recently, large-scale production of new biomass has been highlighted as one of the key solutions for sustainable development.

Many biomasses contain little soluble carbon or short-chain carbon compounds readily available to microorganisms. In this application, such biomasses are also referred to as passive biomasses. Passive biomasses include, in particular, woody biomasses such as chips, shavings, sawdust, celluloses, industrial fiber sludges and recycled fibers, as well as field biomasses, such as biomass from reed or grass, cereal or oilseed crops. Passive biomass also includes paper and cardboard material in landfill waste, many packaging materials and also biodegradable plastics.

Biomasses that contain significant amounts of short-chain carbon compounds or soluble carbon that are readily utilized by microorganisms are also referred to herein as active biomasses. Such carbon sources include, for example, liquid or solid sugars, alcohols or activated dried biomass where passive biomass such as cellulose, hemicellulose and lignin have already been degraded by microbes, such as radiation fungi of the thermophilic region. For example, active biomasses include many waste sludges, such as municipal sewage sludge, food industry bio-waste and sludge, slurry and manure in general, municipal bio-waste, and decayed grass-based peat. Active biomasses generally also contain nutrients, especially soluble nitrogen, which are essential for active microbial activity.

Passive biomasses are already subject to some degree of oxygen-free heat treatment at higher temperatures, either pyrolysis or roasting, which allows the liquid and gaseous components to be recovered as bio-oils or as synthesis gas for further processing or as such for energy recovery. Further processing may include, for example, the production of liquid biofuels or biochemicals. The remaining bio-carbon can be utilized, for example, in energy production.

Carbonization or roasting of passive biomasses requires, as a pre-treatment, drying of the biomass to a very high dry matter content. The same requirement applies to almost all biomass utilization, such as the production of biofuels and biochemicals.

The moisture content of passive biomass used as fuel for power generation is now generally in the order of 50%. The moisture content of milled peat must be at least 40% due to processing and incineration processes, and in general both milled peat and chips are burned at a considerably higher humidity than this level. The drying takes place mainly naturally. In addition, chips and logging heaps and milling peat seams can be covered under dry conditions to absorb less water in wet conditions.

In order to improve efficiency there would be a great need to develop fuel production to be significantly drier than today, and for combustion processes to be successful and efficient in the use of dry biofuels.

A common problem in the handling and utilization of biomass is in many cases also the odor nuisance it generates.

The production of pellets by heat drying and pressing the wood or peat mass into pellets requires a high level of energy, which significantly reduces the profitability and ecology of their production and use. Another major problem with current pellet production methods is that the dried pellets readily absorb moisture from the air and decompose and, in addition, when exposed to moisture, form a favorable breeding ground for molds which also produce carbon monoxide.

It is known that microbial activity generates heat in active biomasses. For example, in composting, the temperature of the biomass can be raised to 50-60 ° C, whereby it is activated by microorganisms in the thermophilic region, in particular ray fungi, which decompose the compostable biomass more efficiently than microbes in the psycho or mesophilic region. can also be used effectively for drying biomass.

Even if such biological drying is applied to the utilization of active biomasses, the problem remains that it cannot be used for the treatment of passive biomasses, which, however, is far more extensive than the utilization of active biomasses.

The key problem with the utilization of biomass, both active and passive, is therefore that in almost all cases it would be desirable to dry the biomass at the lowest possible cost before actual recovery or further processing. It would be highly advantageous to be able to develop methods that could be applied systematically to the large-scale utilization of biomass for the drying and pretreatment of almost all biomasses. In addition, it would often be advantageous to have as much carbon in the dried biomass as readily available short-chain carbon compounds or soluble carbon.

US 7960165 B2 discloses a method and apparatus for drying organic material. The publication summarizes the solution as follows: - When starting, the organic material typically has a moisture content of 65%.

The process and apparatus are traced so that first there is a heating zone into which the material is fed, followed by one or more drying zones. The warm exhaust gases produced by the aerobic microbial activity in the heating area are used to heat the incoming new air and subsequently dry the material doses in subsequent treatment areas.

- New heated air is also circulated to the first area with the aim of raising the temperature "as high as possible as quickly as possible".

The publication lists a number of organic materials, mainly waste materials, to which the process could be applied mainly for the production of fuel. Clearly, there are numerous materials, wood waste, and so forth that cannot be treated by this method as such, since they do not produce microbial activity that naturally produces natural heat. However, no comment is made on this problem, nor is there any suggestion that organic materials could be mixed to solve this problem, and specifically to enable the treatment of passive biomasses, to meet the specified conditions for the method to work.

The publication does not provide any more specific information about temperatures, areas of microbial activity (psychrophilic, mesophilic, thermophilic), control of temperatures and microbial activity, material requirements or processing purposes other than drying the material for fuel use. At the end of the specification, an alternative is also disclosed in which the air circulation areas are replaced by a single drying area, which may be a rotating drum to which heated air is supplied. Here, too, the idea is that drying in the drum takes place with the help of heated air supplied thereto, and inevitably at lowering temperatures compared to temperatures in the first region.

FI 118596 B discloses combining enzyme treatment with biomass drying by heating and air circulation. The purpose is in particular to decompose passive long-chain constituents of biomass in this way. The enzymes or enzyme mixture contain at least a cellulase. The drying temperature is selected from 60 to 80 ° C, which is well suited for the efficient function of the enzymes. Thus, drying is essentially thermal, i.e., not drying by aerobic microbial activity.

SUMMARY OF THE INVENTION

The object of the invention is to provide a solution which largely solves the problems described above and fulfills the wishes set forth.

To achieve this object, the process of the invention for treating biomasses for utilization and specifically for treating passive biomasses in combination with active biomasses is characterized by what is defined in independent claim 1. The other claims define various embodiments of the invention.

In the solution according to the invention, it is essential that the passive biomass is activated in a treatment in which sufficient active biomass is mixed with it so that biological drying can also be utilized in the drying of the passive biomass.

At the same time, passive, for example wood-based biomass with dry solids content and 50-55% dry ventilation can be utilized as a binder or filler by blending it with more moisture-containing active biomass, such as various sludges, to obtain a sufficiently high start-up.

Active biomass is also used in the process as a medium for the decomposition and drying of passive biomass and provides a cost-effective, self-dried biomass basic product for the large-scale utilization of various biomasses, with substantially increased amount of bioavailable carbon.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention and some embodiments thereof will now be described in more detail with reference also to the accompanying drawings, in which Figures 1 and 2 schematically illustrate examples of plants employing the method of the invention.

DETAILED DESCRIPTION OF THE INVENTION

In the following, the process according to the invention and various embodiments thereof are generally considered. In the first step of the process, sufficient active biomass or biomass activated by soluble or short-chain carbon compounds and nutrient supplements is added to the passive biomass and admixed so that the dry matter content of the mixture is sufficiently high, approximately 40%. The blending also aims at providing high concentrations of carbon compounds and nutrients that are readily utilized by microorganisms for rapid onset of aerobic microbial activity. At the same time, care is taken to ensure that the pH of the biomass mixture is sufficiently high for the efficient functioning of the microbes, in the range of 5.5-8.

There is no recommendation as to the percentage of carbon compounds that are readily available to microorganisms, but should be based on experience in mixing and treating different biomasses. There are also significant differences between batches of biomass of the same species or quality. Since it is not possible to determine the required concentration of readily available carbon compounds, it is justified to confine itself to the technical specification of a concentration sufficient to trigger microbial activity.

Pre-treatment and mixing of passive and active biomasses, for example by adding nitrogen, can ensure that the C: N ratio of the biomass mixture is in the range of 20 to 35: 1. If necessary, soluble nitrogen, for example urea in powder form or in liquid form as an aqueous solution, is added to the biomass.

With the mixing of passive and active biomasses, hydrolytic enzymes may also be added to the pulp to accelerate the initiation of aerobic microbial activity.

Also, the small addition of long-chain carbon compounds such as cellulose, hemicellulose and lignin, to the decomposition accelerating enzyme or mixture of enzymes to the biomass mixture may be economically and process-friendly.

In order to create favorable conditions for microbial activity that starts quickly and efficiently in the biomass mixture, it may be necessary to improve the properties of the mixture by adding a pH-raising agent such as lye, lime or dried biomass from a high pH sewage sludge. It should be noted, for example, that during the onset of microbial activity, organic acids often form in the internal reactions of the biomass mixture, whereby the pH of the mixture may be too low to maintain and develop microbial activity. As a general guideline, it may be specified that the pH should remain within the range of 5.5 to 8.

Another viable option for improving the properties of the biomass mixture is to add a catalyst such as iron, for example iron dust or iron oxide, iron sulfate or other iron compound, since iron binds both nutrients and carbon to the biomass mixture. For example, in the manufacture of pellets, iron also improves the hydrophobization of the biomass mixture, which prevents moisture absorption into the pellets. In turn, it improves pellet retention and prevents mold formation and carbon monoxide evaporation from stored pellets.

As stated in the introduction, the process of the invention generally utilizes substantially the same microbial activity as composting. However, the method is fundamentally different from composting, which primarily aims at breaking down the biomass to be composted as completely as possible, first by maintaining a stronger microbial activity and then by so-called "maturing" the compost in a long-lasting slow final stage.

The method of the invention seeks to rapidly and efficiently initiate microbial activity and further increase the temperature of the pulp and rapidly transfer the microbial activity first through the psychophilic region to the mesophilic region and then to the thermophilic region at 50-60 ° C and subsequently at 60-80 ° C to the desired level. depending on how much carbonation is desired in the biomass. This is accomplished by controlling the ventilation and heat retention in the biomass mixture so that the action of aerobic microbes raises the temperature of the pulp relatively quickly as intended.

As the temperature rises from the psychophilic region, the biomass mixture is first waxed at a temperature in the range of 30 to 40 ° C by microorganisms of the mesophilic region, most of which are bacteria and some also of the fungi and fungi of the mesophilic region. Already at this stage, the fungi begin to break down and degrade cellulose, hemicellulose and lignin, and the mass also begins to evaporate moisture.

The action of the microbes further raises the temperature of the biomass to the thermophilic region, where the microorganism strain changes accordingly. It is composed largely of radiation fungi in the thermophilic region which efficiently degrade cellulose, hemicellulose and lignin. A particular object is the cleavage of long-chain carbon compounds in passive biomass in a biomass mixture which is thus biologically activated.

In the early stages of the thermophilic region, it is advisable to be careful of excessive ventilation so that the temperature does not rise above 60-65 ° C. At higher temperatures than that, microbial species begin to die and therefore the rise in temperature must be controlled. On the other hand, the regulation of ventilation and heat also aims to control the evaporation and removal of moisture from the biomass mixture so that microbial activity is not terminated too quickly, thereby failing to achieve the second goal of sufficient cleavage of long-chain carbon compounds. Ventilation and heat retention in the biomass blend is advantageously simulated to operate automatically in plant-like conditions where it can be controlled and controlled.

Under favorable conditions, the biomass temperature rises from the psychrophilic region to the thermophilic region within 10-15 hours. Drying can often be carried out over a period of 1 to 3 days, but it is preferred, however, to maintain the temperature for a sufficiently long time in the range of 60-80 ° C, where the sponges are still functional and degrade the passive biomasses.

This biological drying is continued to a dry solids content that it can achieve, typically to a dry solids content of 60-70%.

The activity of aerobic microbes begins to diminish as the biomass mixture dries, and ceases practically when a dry matter content of about 60% is reached. With this approach, ventilation can be increased vigorously, bringing the temperature of the biomass to as high as 80 ° C or above during the final drying stage. In this way, drying can continue to be effective even when the biomass mixture is cooled, especially if the drying air is extremely drier compared to the biomass temperature, and up to the said 70% dry matter content can be achieved. The final temperature pulse also has the advantageous effect of simultaneously hygienizing the biomass mixture.

The process according to the invention, in which passive biomasses can be dried with active or treated biomasses, could also be defined as biological media drying. Active biomass acts as a medium in which the microbial activity that is triggered causes the process to decompose and the microbial activity to be triggered also in the passive biomass. Passive biomass is utilized in the final stage of the process in the same way as active biomass, and the initially wet passive biomass dries out like the active biomass.

Further drying of the biomass mixture can be continued as needed, for example by pulse drying, in which the pulp temperature is raised during a short thermal heating period to, for example, about 80 ° C, followed by slowly blowing dry dry air, for example 10-15 ° C and humidity preferably, for example, about 5%. Drying continues until the mass has cooled to ambient temperature and there is no difference in vapor pressure. Such drying pulses may be repeated, if necessary, so that the dry matter content of the biomass is at least 95%. If the biomass is granulated or crushed, then one additional drying pulse is likely to be sufficient.

For a variety of biomass applications, said dry solids content of 70 to 80 percent is sufficient, but also biomass having said dry matter content of about 95 percent is particularly needed in fuel applications.

Naturally, the final drying of the biomass can be done thermally in ways other than pulse drying.

When drying biomass as described above, while decomposing carbon compounds that are difficult to utilize, in particular by means of radiation fungi in the thermophilic region, a kind of thermophilic bio-carbonation of the biomass can also be said. The amount of easily recoverable carbon increases rapidly in the biomass and can be up to 60-70% at the end of the treatment. This is because oxygen-based microbial activity raises the temperature of the biomass and causes the decomposition and carbonization of carbon compounds.

Figure 1 illustrates a plant in which slurry 2 or other active moist biomass 1 is mixed with passive biomass 1 and further recycled, dried and granulated biomass 3 from the process. The mixing is illustrated here by feeding materials from silos to a conveyor 4 which can be mixed into indicated by the arrow 6, for example, urea or another nitrogen-C mass in some other way to improve the ratio. In practice, the dosages of the various ingredients are tracked in the manner considered appropriate in each case. A suitable instruction in mixing is to obtain a dry solids content of the pulp in the range of 40-45%. It is possible to start aerobic microbial activity even in wetter masses, but when the humidity is at this level, it can be triggered quickly. As stated above, suitable enzymes, catalysts, or bioavailable carbonising or pH adjusting agents may also be added to the mixture mass at this stage, in particular, suitable waste materials available for this purpose.

From the mixer, the mass 7 is conveyed by means of a suitable conveyor 8 to the mixture mass or heaps 9, which, if necessary, are suitably protected for both damping and aeration control. An aerobic microbial activity is initiated in the pulp, which is controlled so that the temperature rises as quickly as possible to the thermophilic region, i.e. above 50 ° C, preferably to about 60 ° C.

The mixture mass is dried in this manner from about 60 percent dry matter content, after which the hot mass is fed into the granulating drum 10. By suitably adjusting the direction of the arrow 11 shown ilmanpuhallusta in the same manner as in general industrial drying areas, the temperature of the mass is preferably remain in the region 60-80 ° C, wherein the granules takes place in aerobic biological carbonization while still drying. The result is thus granules having a solids content of 70 to 90% and a high content of readily bioavailable carbon.

The pulp may also be produced in the granulation step to increase the direction of arrow 12 as shown in the granules further activating additives such as catalysts, enzymes, glycol, alcohol, or sugar-containing substances.

The granules produced can be used in many ways, for example as soil improvers in fields and other substrates, as basic material in bio-fertilizers or as an accelerator in composting or equally in digestion plants for biogas production. For example, the size of the granules may be in the range of 2 to 30 mm.

A portion of the granules is taken into storage 15 for use as a dry substance 3 which, at the beginning of the process, is metered to adjust the dry solids content of the blend to a desired range of 40-45% while providing additional biodegradable carbon.

Figure 2 shows a plant where the upstream end of the process up to the mixer 5 and the possible addition of urea or nitrogen 6 is similar to that of the plant of Figure 1. From the mixer, the pulp is now fed to a press press 16, from which the incoming pieces 17 are led by means of a suitable conveyor 18 to the mixture mass or piles 19, which are required to be suitably shielded, if necessary, both to dampen and to regulate the air supply. An aerobic microbial activity is initiated in the lump pile, which is controlled so that the temperature rises to the thermophilic area as quickly as possible, as in the case of the lump pile of Figure 1.

It is advantageous to dry the biomass blends in pieces or briquettes, since shrinkage of the biomass can best be utilized in the drying process. In many cases, crushing for drying may be necessary, for example due to the dense composition of the alloy mass, which prevents adequate ventilation for drying. The pieces dry evenly because the amount of air between them is sufficient to maintain microbial activity evenly throughout the pieces. For example, the pieces may have a diameter in the range of 50 to 250 mm.

Dried pieces with a dry solids content of 60 to 70% can be used as fuel, for example (arrow 20). On the other hand, the treatment can be continued as in the case of Fig. 1, whereby the pieces are first fed to the crusher 21 and then crushed to the granulation drum 22 where the aeration 23 and the possible use of activating additives 24 are similar to the plant of Fig. 1. The resulting granules are crushed or are utilized as shown by the arrow 25 in various applications, and on the other hand can be taken into storage 26 seosmassassa a powder for use in three.

Yet another possibility is to take the pieces 27 as indicated by the arrow hiillettäväksi for example, in a silo 28 by means of a suitable strong aeration 29. Carbonated granules 30 can be used for certain more specific applications, such as waste water treatment or biofuel preparation.

Instead of granulating, the mixture mass may also be pelletized, whereby it is preferable to compress the pellets from a biomass blend in a thermophilic temperature range and dry them in a drum at a temperature of 60-80 ° C at low rotation speed. It is preferable to add iron ions in some suitable form to the pulp to improve its hydrophobicity and to prevent moisture from being absorbed back into the pellets. This treatment also results in shrinkage of the pellets during drying, and the pellets produced are of an order of density, cohesiveness and calorific value compared to wood or peat pellets produced by conventional processes. The biomass mixture can also be compressed into pellets at an earlier stage after mixing the biomasses and then dried, for example, in a slow rotating drum as described above, where the temperature is allowed to rise to the thermophilic region. The size of the pellets can range from 5 to 50 mm.

The treatment in the granulating or pelleting drum is also easy to automate so that the temperature is maintained in the process, for example in the range of 60-80 ° C. The starting material for pellet production may need to be crushed or otherwise crushed to 0-5 mm.

In the crushing or possibly necessary screening, the residual biomass material can be used in the above-mentioned manner in the internal cycle of biomass treatment by adding it in the first blend to the biomass mixture.

Often the biomass obtained after the biological drying step to a dry matter content of the order of 70% is, for example, a good fuel in the form of lumps or crushed. In the burn form, it is suitable for use in grate-based incineration plants, and when crushed and screened, for example to 4 to 10 or 4 to 20 mm, is well suited as a fuel for stoker-type plants.

Also for further drying of pulp by pulse drying, the drum is a preferred treatment device. However, it is advantageous to screen 0 to 4 mm of fine material from the grit to be dried, as this improves the passage of drying air between the granules. The fine material can be utilized not only in the internal circulation of the treatment but also, for example, as a soil conditioner, which increases the carbon source needed by the microorganisms in the field.

In the temperature range 60-80 ° C, the temperature has never exceeded 90 ° C in biological drying with microbes and sponges and in the thermophilic bio-charcoal and, for example, pulse post-drying. Therefore, the liquid or gaseous components that are important for the use of the process-treated biomass for soil improvement, that is, for the re-cultivation of cellular masses for better moisture and nutrient binding, have not been evaporated from the biomass.

Thus, by biological drying and suitable post-drying, the dry matter content of the biomass can be obtained to more than 95% without evaporation or consumption of important constituents. Biomass thus treated, which in itself is an excellent fuel, is also an excellent raw material for many further processing applications.

Such applications include, for example, biogas production of new technologies, liquid fuel production, production gas as an intermediate step in the production of various biochemicals, and biocarbon production as soil improvers, fuels or activated carbon in filters, depending on the carbon method and temperature.

Another advantage of this heat treatment is that the biomass is practically completely hygienized, without having to worry about odors, for example. In addition, the carbonisation of biomass and the decomposition of carbon compounds will continue, improving both the biomass utilization in biological applications and the fuel value. This is important because in practice the use of biomass for combustion in energy production is often the most economically advantageous recovery.

Biologically and possibly with additional thermal drying, the mild torrefaction or similar treatment of well-dried biomass as described above is enhanced because the carbon gas and heat penetrate into the biomass to be charred more rapidly, when not inhibited by moisture. Energy is saved because the extra water does not have to be heated and evaporated during processing.

With the method according to the invention it is possible to develop the utilization of various active and passive biomasses on a large scale on a completely new basis. Recoverable biomasses can be collected from suitable areas to processing facilities developed at the level of industrial plants, where they are mixed, pre-treated and biologically dried, and possibly further dried and otherwise processed to certain specifications or raw materials for further processing. Compared to current biomass products and raw materials, these end products and raw materials are easily and inexpensively handled, stored and transported in extremely dry chunks, briquettes, pellets or crumbs. At the same time, they have decomposed hard-to-recover carbon compounds into an easy-to-recover form, while retaining to a very large extent all useful components of the biomass.

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

Claims (10)

A process for processing biomasses for utilization and in particular for processing passive biomasses together with active biomasses, characterized in that biomasses with different carbon, nutritional and moisture content are systematically collected for industrial processing, in which: at least one passive and an active biomass (1,2, 3) are mixed together and properties of the biomass mixture (7) are improved if necessary with additives such that the dry matter content is about 40%, the C: N ratio is in the range 20 - 35: 1, the pH is within the range of 5.5 to 8 and the amount of carbon readily usable for microbes is sufficient to initiate aerobic microbial activity; the microbial activity in the biomass mixture (9, 19) is maintained by regulating air exchange and the conservation of heat and, as the microbial activity heats the biomass, it is controlled to move from mesophilic to thermophilic region (approximately 50 - 60 ° C) and finally to the temperature range 60 - 80 ° C to dry the mixture by using biologically evolved heat to dry matter content of 60 - 70% and to decompose long-chain carbon compounds into short-chain or bilogically readily usable carbon within approximately 1-3 days; and the biomass mixture is finally treated in the temperature between 60 and 80 ° C mainly by regulating air exchange either in connection with granulation or by first treating the biomass mixture to crusher or pellets. Process according to claim 1, characterized in that in the final treatment in the temperature between 60 and 80 ° C the biomass mixture is dried in a granulation drum (10, 22) to the dry matter content 70 - 90%. Process according to claim 1, characterized in that the biomass mixture is pelleted for the final treatment. Method according to claim 1, characterized in that after mixing the biomass mixture is pressed into pieces (5, 16) to initiate and maintain the microbial activity in the bit height prior to the final treatment (19). Process according to claim 1, characterized in that the properties of the biomass mixture are improved by adding hydrolytic enzymes there to accelerate the initiation of the microbial activity. 6. A process according to claim 1, characterized in that the properties of the biomass mixture are improved by the addition of enzymes which accelerate the degradation of long chain carbon compounds, such as cellulose, hemicellulose and lignin. Process according to claim 1, characterized in that the properties of the biomass mixture are improved by adding nitrogen there, for example urea in powder form or in liquid form as aqueous solution. 8. A process according to claim 1, characterized in that the properties of the biomass mixture are improved by the addition of a substance which increases the pH, such as lye, lime or dried biomass produced by wastewater sludge at high pH. 9. A process according to claim 1, characterized in that the properties of the biomass mixture are improved by adding there short-chain carbon compounds, such as sugar, ethanol or carbon compounds, broken down by aerobic microbial activity. Process according to claim 1, characterized in that the biomass dried by the process is circulated to the mixing stage of the biomass to obtain a sufficient dry substance content.